/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/
#include "curl_setup.h"

#ifdef USE_LIBSSH2

/* #define CURL_LIBSSH2_DEBUG */

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef __VMS
#include <in.h>
#include <inet.h>
#endif

#include "urldata.h"
#include "sendf.h"
#include "curl_trc.h"
#include "hostip.h"
#include "progress.h"
#include "transfer.h"
#include "vssh/ssh.h"
#include "url.h"
#include "cfilters.h"
#include "connect.h"
#include "parsedate.h" /* for the week day and month names */
#include "multiif.h"
#include "select.h"
#include "curlx/fopen.h"
#include "vssh/vssh.h"
#include "curlx/strparse.h"
#include "curlx/base64.h" /* for base64 encoding/decoding */

static const char *sftp_libssh2_strerror(unsigned long err)
{
  switch(err) {
  case LIBSSH2_FX_NO_SUCH_FILE:
    return "No such file or directory";

  case LIBSSH2_FX_PERMISSION_DENIED:
    return "Permission denied";

  case LIBSSH2_FX_FAILURE:
    return "Operation failed";

  case LIBSSH2_FX_BAD_MESSAGE:
    return "Bad message from SFTP server";

  case LIBSSH2_FX_NO_CONNECTION:
    return "Not connected to SFTP server";

  case LIBSSH2_FX_CONNECTION_LOST:
    return "Connection to SFTP server lost";

  case LIBSSH2_FX_OP_UNSUPPORTED:
    return "Operation not supported by SFTP server";

  case LIBSSH2_FX_INVALID_HANDLE:
    return "Invalid handle";

  case LIBSSH2_FX_NO_SUCH_PATH:
    return "No such file or directory";

  case LIBSSH2_FX_FILE_ALREADY_EXISTS:
    return "File already exists";

  case LIBSSH2_FX_WRITE_PROTECT:
    return "File is write protected";

  case LIBSSH2_FX_NO_MEDIA:
    return "No media";

  case LIBSSH2_FX_NO_SPACE_ON_FILESYSTEM:
    return "Disk full";

  case LIBSSH2_FX_QUOTA_EXCEEDED:
    return "User quota exceeded";

  case LIBSSH2_FX_UNKNOWN_PRINCIPLE:
    return "Unknown principle";

  case LIBSSH2_FX_LOCK_CONFlICT:
    return "File lock conflict";

  case LIBSSH2_FX_DIR_NOT_EMPTY:
    return "Directory not empty";

  case LIBSSH2_FX_NOT_A_DIRECTORY:
    return "Not a directory";

  case LIBSSH2_FX_INVALID_FILENAME:
    return "Invalid filename";

  case LIBSSH2_FX_LINK_LOOP:
    return "Link points to itself";
  }
  return "Unknown error in libssh2";
}

static void kbd_callback(const char *name, int name_len,
                         const char *instruction, int instruction_len,
                         int num_prompts,
                         const LIBSSH2_USERAUTH_KBDINT_PROMPT *prompts,
                         LIBSSH2_USERAUTH_KBDINT_RESPONSE *responses,
                         void **abstract)
{
  struct Curl_easy *data = (struct Curl_easy *)*abstract;

#ifdef CURL_LIBSSH2_DEBUG
  curl_mfprintf(stderr, "name=%s\n", name);
  curl_mfprintf(stderr, "name_len=%d\n", name_len);
  curl_mfprintf(stderr, "instruction=%s\n", instruction);
  curl_mfprintf(stderr, "instruction_len=%d\n", instruction_len);
  curl_mfprintf(stderr, "num_prompts=%d\n", num_prompts);
#else
  (void)name;
  (void)name_len;
  (void)instruction;
  (void)instruction_len;
#endif /* CURL_LIBSSH2_DEBUG */
  if(num_prompts == 1) {
    struct connectdata *conn = data->conn;
    /* this function must allocate memory that can be freed by libssh2, which
       uses the LIBSSH2_FREE_FUNC callback */
    responses[0].text = Curl_cstrdup(conn->passwd);
    responses[0].length =
      responses[0].text == NULL ? 0 : curlx_uztoui(strlen(conn->passwd));
  }
  (void)prompts;
} /* kbd_callback */

static CURLcode sftp_libssh2_error_to_CURLE(unsigned long err)
{
  switch(err) {
  case LIBSSH2_FX_OK:
    return CURLE_OK;

  case LIBSSH2_FX_NO_SUCH_FILE:
  case LIBSSH2_FX_NO_SUCH_PATH:
    return CURLE_REMOTE_FILE_NOT_FOUND;

  case LIBSSH2_FX_PERMISSION_DENIED:
  case LIBSSH2_FX_WRITE_PROTECT:
  case LIBSSH2_FX_LOCK_CONFlICT:
    return CURLE_REMOTE_ACCESS_DENIED;

  case LIBSSH2_FX_NO_SPACE_ON_FILESYSTEM:
  case LIBSSH2_FX_QUOTA_EXCEEDED:
    return CURLE_REMOTE_DISK_FULL;

  case LIBSSH2_FX_FILE_ALREADY_EXISTS:
    return CURLE_REMOTE_FILE_EXISTS;

  case LIBSSH2_FX_DIR_NOT_EMPTY:
    return CURLE_QUOTE_ERROR;

  default:
    break;
  }

  return CURLE_SSH;
}

static CURLcode libssh2_session_error_to_CURLE(int err)
{
  switch(err) {
  /* Ordered by order of appearance in libssh2.h */
  case LIBSSH2_ERROR_NONE:
    return CURLE_OK;

  /* This is the error returned by libssh2_scp_recv2
   * on unknown file */
  case LIBSSH2_ERROR_SCP_PROTOCOL:
    return CURLE_REMOTE_FILE_NOT_FOUND;

  case LIBSSH2_ERROR_SOCKET_NONE:
    return CURLE_COULDNT_CONNECT;

  case LIBSSH2_ERROR_ALLOC:
    return CURLE_OUT_OF_MEMORY;

  case LIBSSH2_ERROR_SOCKET_SEND:
    return CURLE_SEND_ERROR;

  case LIBSSH2_ERROR_HOSTKEY_INIT:
  case LIBSSH2_ERROR_HOSTKEY_SIGN:
  case LIBSSH2_ERROR_PUBLICKEY_UNRECOGNIZED:
  case LIBSSH2_ERROR_PUBLICKEY_UNVERIFIED:
    return CURLE_PEER_FAILED_VERIFICATION;

  case LIBSSH2_ERROR_PASSWORD_EXPIRED:
    return CURLE_LOGIN_DENIED;

  case LIBSSH2_ERROR_SOCKET_TIMEOUT:
  case LIBSSH2_ERROR_TIMEOUT:
    return CURLE_OPERATION_TIMEDOUT;

  case LIBSSH2_ERROR_EAGAIN:
    return CURLE_AGAIN;
  }

  return CURLE_SSH;
}

/* These functions are made to use the libcurl memory functions - NOT the
   debugmem functions, as that leads us to trigger on libssh2 memory leaks
   that are not ours to care for */

static LIBSSH2_ALLOC_FUNC(my_libssh2_malloc)
{
  (void)abstract;
  return Curl_cmalloc(count);
}

static LIBSSH2_REALLOC_FUNC(my_libssh2_realloc)
{
  (void)abstract;
  return Curl_crealloc(ptr, count);
}

static LIBSSH2_FREE_FUNC(my_libssh2_free)
{
  (void)abstract;
  if(ptr) /* ssh2 agent sometimes call free with null ptr */
    Curl_cfree(ptr);
}

static int sshkeycallback(CURL *easy,
                          const struct curl_khkey *knownkey, /* known */
                          const struct curl_khkey *foundkey, /* found */
                          enum curl_khmatch match,
                          void *clientp)
{
  (void)easy;
  (void)knownkey;
  (void)foundkey;
  (void)clientp;

  /* we only allow perfect matches, and we reject everything else */
  return (match != CURLKHMATCH_OK) ? CURLKHSTAT_REJECT : CURLKHSTAT_FINE;
}

static enum curl_khtype convert_ssh2_keytype(int sshkeytype)
{
  enum curl_khtype keytype = CURLKHTYPE_UNKNOWN;
  switch(sshkeytype) {
  case LIBSSH2_HOSTKEY_TYPE_RSA:
    keytype = CURLKHTYPE_RSA;
    break;
  case LIBSSH2_HOSTKEY_TYPE_DSS:
    keytype = CURLKHTYPE_DSS;
    break;
#ifdef LIBSSH2_HOSTKEY_TYPE_ECDSA_256
  case LIBSSH2_HOSTKEY_TYPE_ECDSA_256:
    keytype = CURLKHTYPE_ECDSA;
    break;
#endif
#ifdef LIBSSH2_HOSTKEY_TYPE_ECDSA_384
  case LIBSSH2_HOSTKEY_TYPE_ECDSA_384:
    keytype = CURLKHTYPE_ECDSA;
    break;
#endif
#ifdef LIBSSH2_HOSTKEY_TYPE_ECDSA_521
  case LIBSSH2_HOSTKEY_TYPE_ECDSA_521:
    keytype = CURLKHTYPE_ECDSA;
    break;
#endif
#ifdef LIBSSH2_HOSTKEY_TYPE_ED25519
  case LIBSSH2_HOSTKEY_TYPE_ED25519:
    keytype = CURLKHTYPE_ED25519;
    break;
#endif
  }
  return keytype;
}

static CURLcode ssh_knownhost(struct Curl_easy *data,
                              struct ssh_conn *sshc)
{
  int sshkeytype = 0;
  size_t keylen = 0;
  int rc = 0;
  CURLcode result = CURLE_OK;

  if(data->set.str[STRING_SSH_KNOWNHOSTS]) {
    /* we are asked to verify the host against a file */
    struct connectdata *conn = data->conn;
    struct libssh2_knownhost *host = NULL;
    const char *remotekey = libssh2_session_hostkey(sshc->ssh_session,
                                                    &keylen, &sshkeytype);
    int keycheck = LIBSSH2_KNOWNHOST_CHECK_FAILURE;
    int keybit = 0;

    if(remotekey) {
      /*
       * A subject to figure out is what hostname we need to pass in here.
       * What hostname does OpenSSH store in its file if an IDN name is
       * used?
       */
      enum curl_khmatch keymatch;
      curl_sshkeycallback func =
        data->set.ssh_keyfunc ? data->set.ssh_keyfunc : sshkeycallback;
      struct curl_khkey knownkey;
      struct curl_khkey *knownkeyp = NULL;
      struct curl_khkey foundkey;

      switch(sshkeytype) {
      case LIBSSH2_HOSTKEY_TYPE_RSA:
        keybit = LIBSSH2_KNOWNHOST_KEY_SSHRSA;
        break;
      case LIBSSH2_HOSTKEY_TYPE_DSS:
        keybit = LIBSSH2_KNOWNHOST_KEY_SSHDSS;
        break;
      case LIBSSH2_HOSTKEY_TYPE_ECDSA_256:
        keybit = LIBSSH2_KNOWNHOST_KEY_ECDSA_256;
        break;
      case LIBSSH2_HOSTKEY_TYPE_ECDSA_384:
        keybit = LIBSSH2_KNOWNHOST_KEY_ECDSA_384;
        break;
      case LIBSSH2_HOSTKEY_TYPE_ECDSA_521:
        keybit = LIBSSH2_KNOWNHOST_KEY_ECDSA_521;
        break;
      case LIBSSH2_HOSTKEY_TYPE_ED25519:
        keybit = LIBSSH2_KNOWNHOST_KEY_ED25519;
        break;
      default:
        infof(data, "unsupported key type, cannot check knownhosts");
        keybit = 0;
        break;
      }
      if(!keybit)
        /* no check means failure! */
        rc = CURLKHSTAT_REJECT;
      else {
        keycheck = libssh2_knownhost_checkp(sshc->kh,
                                            conn->origin->hostname,
                                            (conn->origin->port != PORT_SSH) ?
                                            conn->origin->port : -1,
                                            remotekey, keylen,
                                            LIBSSH2_KNOWNHOST_TYPE_PLAIN|
                                            LIBSSH2_KNOWNHOST_KEYENC_RAW|
                                            keybit,
                                            &host);

        infof(data, "SSH host check: %d, key: %s", keycheck,
              (keycheck <= LIBSSH2_KNOWNHOST_CHECK_MISMATCH) ?
              host->key : "<none>");

        /* setup 'knownkey' */
        if(keycheck <= LIBSSH2_KNOWNHOST_CHECK_MISMATCH) {
          knownkey.key = host->key;
          knownkey.len = 0;
          knownkey.keytype = convert_ssh2_keytype(sshkeytype);
          knownkeyp = &knownkey;
        }

        /* setup 'foundkey' */
        foundkey.key = remotekey;
        foundkey.len = keylen;
        foundkey.keytype = convert_ssh2_keytype(sshkeytype);

        /*
         * if any of the LIBSSH2_KNOWNHOST_CHECK_* defines and the
         * curl_khmatch enum are ever modified, we need to introduce a
         * translation table here!
         */
        keymatch = (enum curl_khmatch)keycheck;

        /* Ask the callback how to behave */
        Curl_set_in_callback(data, TRUE);
        rc = func(data, knownkeyp, /* from the knownhosts file */
                  &foundkey, /* from the remote host */
                  keymatch, data->set.ssh_keyfunc_userp);
        Curl_set_in_callback(data, FALSE);
      }
    }
    else
      /* no remotekey means failure! */
      rc = CURLKHSTAT_REJECT;

    switch(rc) {
    default: /* unknown return codes is the same as reject */
    case CURLKHSTAT_REJECT:
      myssh_to(data, sshc, SSH_SESSION_FREE);
      FALLTHROUGH();
    case CURLKHSTAT_DEFER:
      /* DEFER means bail out but keep the SSH_HOSTKEY state */
      result = CURLE_PEER_FAILED_VERIFICATION;
      break;
    case CURLKHSTAT_FINE_REPLACE:
      /* remove old host+key that does not match */
      if(host)
        libssh2_knownhost_del(sshc->kh, host);
      FALLTHROUGH();
    case CURLKHSTAT_FINE:
    case CURLKHSTAT_FINE_ADD_TO_FILE:
      /* proceed */
      if(keycheck != LIBSSH2_KNOWNHOST_CHECK_MATCH) {
        /* the found host+key did not match but has been told to be fine
           anyway so we add it in memory */
        int addrc = libssh2_knownhost_add(sshc->kh,
                                          conn->origin->hostname, NULL,
                                          remotekey, keylen,
                                          LIBSSH2_KNOWNHOST_TYPE_PLAIN|
                                          LIBSSH2_KNOWNHOST_KEYENC_RAW|
                                          keybit, NULL);
        if(addrc)
          infof(data, "WARNING: adding the known host %s failed",
                conn->origin->hostname);
        else if(rc == CURLKHSTAT_FINE_ADD_TO_FILE ||
                rc == CURLKHSTAT_FINE_REPLACE) {
          /* now we write the entire in-memory list of known hosts to the
             known_hosts file */
          int wrc =
            libssh2_knownhost_writefile(sshc->kh,
                                        data->set.str[STRING_SSH_KNOWNHOSTS],
                                        LIBSSH2_KNOWNHOST_FILE_OPENSSH);
          if(wrc) {
            infof(data, "WARNING: writing %s failed",
                  data->set.str[STRING_SSH_KNOWNHOSTS]);
          }
        }
      }
      break;
    }
  }
  return result;
}

static CURLcode ssh_check_fingerprint(struct Curl_easy *data,
                                      struct ssh_conn *sshc)
{
  const char *pubkey_md5 = data->set.str[STRING_SSH_HOST_PUBLIC_KEY_MD5];
  const char *pubkey_sha256 = data->set.str[STRING_SSH_HOST_PUBLIC_KEY_SHA256];

  infof(data, "SSH MD5 public key: %s",
        pubkey_md5 != NULL ? pubkey_md5 : "NULL");
  infof(data, "SSH SHA256 public key: %s",
        pubkey_sha256 != NULL ? pubkey_sha256 : "NULL");

  if(pubkey_sha256) {
    const char *fingerprint = NULL;
    char *fingerprint_b64 = NULL;
    size_t fingerprint_b64_len;
    size_t pub_pos = 0;
    size_t b64_pos = 0;

    /* The fingerprint points to static storage (!), do not free() it. */
    fingerprint = libssh2_hostkey_hash(sshc->ssh_session,
                                       LIBSSH2_HOSTKEY_HASH_SHA256);
    if(!fingerprint) {
      failf(data,
            "Denied establishing ssh session: SHA256 fingerprint "
            "not available");
      myssh_to(data, sshc, SSH_SESSION_FREE);
      return CURLE_PEER_FAILED_VERIFICATION;
    }

    /* The length of fingerprint is 32 bytes for SHA256.
     * See libssh2_hostkey_hash documentation. */
    if(curlx_base64_encode((const uint8_t *)fingerprint, 32, &fingerprint_b64,
                           &fingerprint_b64_len) != CURLE_OK) {
      myssh_to(data, sshc, SSH_SESSION_FREE);
      return CURLE_PEER_FAILED_VERIFICATION;
    }

    if(!fingerprint_b64) {
      failf(data, "SHA256 fingerprint could not be encoded");
      myssh_to(data, sshc, SSH_SESSION_FREE);
      return CURLE_PEER_FAILED_VERIFICATION;
    }

    infof(data, "SSH SHA256 fingerprint: %s", fingerprint_b64);

    /* Find the position of any = padding characters in the public key */
    while((pubkey_sha256[pub_pos] != '=') && pubkey_sha256[pub_pos]) {
      pub_pos++;
    }

    /* Find the position of any = padding characters in the base64 coded
     * hostkey fingerprint */
    while((fingerprint_b64[b64_pos] != '=') && fingerprint_b64[b64_pos]) {
      b64_pos++;
    }

    /* Before we authenticate we check the hostkey's SHA256 fingerprint
     * against a known fingerprint, if available.
     */
    if((pub_pos != b64_pos) ||
       strncmp(fingerprint_b64, pubkey_sha256, pub_pos)) {
      failf(data,
            "Denied establishing ssh session: mismatch SHA256 fingerprint. "
            "Remote %s is not equal to %s", fingerprint_b64, pubkey_sha256);
      curlx_free(fingerprint_b64);
      myssh_to(data, sshc, SSH_SESSION_FREE);
      return CURLE_PEER_FAILED_VERIFICATION;
    }

    curlx_free(fingerprint_b64);

    infof(data, "SHA256 checksum match");
  }

  if(pubkey_md5) {
    char md5buffer[33];
    const char *fingerprint;

    fingerprint = libssh2_hostkey_hash(sshc->ssh_session,
                                       LIBSSH2_HOSTKEY_HASH_MD5);

    if(fingerprint) {
      /* The fingerprint points to static storage (!), do not free() it. */
      int i;
      for(i = 0; i < 16; i++) {
        curl_msnprintf(&md5buffer[i * 2], 3, "%02x",
                       (unsigned char)fingerprint[i]);
      }

      infof(data, "SSH MD5 fingerprint: %s", md5buffer);
    }

    /* This does NOT verify the length of 'pubkey_md5' separately, which
       makes the comparison below fail unless it is exactly 32 characters */
    if(!fingerprint || !curl_strequal(md5buffer, pubkey_md5)) {
      if(fingerprint) {
        failf(data,
              "Denied establishing ssh session: mismatch MD5 fingerprint. "
              "Remote %s is not equal to %s", md5buffer, pubkey_md5);
      }
      else {
        failf(data,
              "Denied establishing ssh session: MD5 fingerprint "
              "not available");
      }
      myssh_to(data, sshc, SSH_SESSION_FREE);
      return CURLE_PEER_FAILED_VERIFICATION;
    }
    infof(data, "MD5 checksum match");
  }

  if(!pubkey_md5 && !pubkey_sha256) {
    if(data->set.ssh_hostkeyfunc) {
      size_t keylen = 0;
      int sshkeytype = 0;
      int rc = 0;
      /* we handle the process to the callback */
      const char *remotekey = libssh2_session_hostkey(sshc->ssh_session,
                                                      &keylen, &sshkeytype);
      if(remotekey) {
        enum curl_khtype keytype = convert_ssh2_keytype(sshkeytype);
        Curl_set_in_callback(data, TRUE);
        rc = data->set.ssh_hostkeyfunc(data->set.ssh_hostkeyfunc_userp,
                                       (int)keytype, remotekey, keylen);
        Curl_set_in_callback(data, FALSE);
        if(rc != CURLKHMATCH_OK) {
          myssh_to(data, sshc, SSH_SESSION_FREE);
          return CURLE_PEER_FAILED_VERIFICATION;
        }
      }
      else {
        myssh_to(data, sshc, SSH_SESSION_FREE);
        return CURLE_PEER_FAILED_VERIFICATION;
      }
      return CURLE_OK;
    }
    else {
      return ssh_knownhost(data, sshc);
    }
  }
  else {
    /* as we already matched, we skip the check for known hosts */
    return CURLE_OK;
  }
}

/*
 * ssh_force_knownhost_key_type() checks the known hosts file and try to
 * force a specific public key type from the server if an entry is found.
 */
static CURLcode ssh_force_knownhost_key_type(struct Curl_easy *data,
                                             struct ssh_conn *sshc)
{
  CURLcode result = CURLE_OK;

  static const char hostkey_method_ssh_ed25519[] = "ssh-ed25519";
  static const char hostkey_method_ssh_ecdsa_521[] = "ecdsa-sha2-nistp521";
  static const char hostkey_method_ssh_ecdsa_384[] = "ecdsa-sha2-nistp384";
  static const char hostkey_method_ssh_ecdsa_256[] = "ecdsa-sha2-nistp256";
  static const char hostkey_method_ssh_rsa_all[] =
    "rsa-sha2-256,rsa-sha2-512,ssh-rsa";
  static const char hostkey_method_ssh_dss[] = "ssh-dss";
  bool found = FALSE;

  if(sshc->kh &&
     !data->set.str[STRING_SSH_HOST_PUBLIC_KEY_MD5] &&
     !data->set.str[STRING_SSH_HOST_PUBLIC_KEY_SHA256]) {
    struct libssh2_knownhost *store = NULL;
    struct connectdata *conn = data->conn;
    /* lets try to find our host in the known hosts file */
    while(!libssh2_knownhost_get(sshc->kh, &store, store)) {
      /* For non-standard ports, the name is enclosed in */
      /* square brackets, followed by a colon and the port */
      if(store) {
        if(store->name) {
          if(store->name[0] == '[') {
            curl_off_t port;
            size_t kh_name_size = 0;
            const char *p;
            const char *kh_name_end = strstr(store->name, "]:");
            if(!kh_name_end) {
              infof(data, "Invalid host pattern %s in %s",
                    store->name, data->set.str[STRING_SSH_KNOWNHOSTS]);
              continue;
            }
            p = kh_name_end + 2; /* start of port number */
            if(!curlx_str_number(&p, &port, 0xffff) &&
               (kh_name_end && (port == conn->origin->port))) {
              kh_name_size = strlen(store->name) - 1 - strlen(kh_name_end);
              if(strncmp(store->name + 1,
                         conn->origin->hostname, kh_name_size) == 0) {
                found = TRUE;
                break;
              }
            }
          }
          else if(strcmp(store->name, conn->origin->hostname) == 0) {
            found = TRUE;
            break;
          }
        }
        else {
          found = TRUE;
          break;
        }
      }
    }

    if(found) {
      int rc;
      const char *hostkey_method = NULL;
      infof(data, "Found host %s in %s",
            conn->origin->hostname, data->set.str[STRING_SSH_KNOWNHOSTS]);

      switch(store->typemask & LIBSSH2_KNOWNHOST_KEY_MASK) {
      case LIBSSH2_KNOWNHOST_KEY_ED25519:
        hostkey_method = hostkey_method_ssh_ed25519;
        break;
      case LIBSSH2_KNOWNHOST_KEY_ECDSA_521:
        hostkey_method = hostkey_method_ssh_ecdsa_521;
        break;
      case LIBSSH2_KNOWNHOST_KEY_ECDSA_384:
        hostkey_method = hostkey_method_ssh_ecdsa_384;
        break;
      case LIBSSH2_KNOWNHOST_KEY_ECDSA_256:
        hostkey_method = hostkey_method_ssh_ecdsa_256;
        break;
      case LIBSSH2_KNOWNHOST_KEY_SSHRSA:
        hostkey_method = hostkey_method_ssh_rsa_all;
        break;
      case LIBSSH2_KNOWNHOST_KEY_SSHDSS:
        hostkey_method = hostkey_method_ssh_dss;
        break;
      case LIBSSH2_KNOWNHOST_KEY_RSA1:
        failf(data, "Found host key type RSA1 which is not supported");
        return CURLE_SSH;
      default:
        failf(data, "Unknown host key type: %i",
              (store->typemask & LIBSSH2_KNOWNHOST_KEY_MASK));
        return CURLE_SSH;
      }

      infof(data, "Set \"%s\" as SSH hostkey type", hostkey_method);
      rc = libssh2_session_method_pref(sshc->ssh_session,
                                       LIBSSH2_METHOD_HOSTKEY, hostkey_method);
      if(rc) {
        char *err_msg = NULL;
        int errlen;
        libssh2_session_last_error(sshc->ssh_session, &err_msg, &errlen, 0);
        failf(data, "libssh2 method '%s' failed: %s", hostkey_method, err_msg);
        result = libssh2_session_error_to_CURLE(rc);
      }
    }
    else {
      infof(data, "Did not find host %s in %s",
            conn->origin->hostname, data->set.str[STRING_SSH_KNOWNHOSTS]);
    }
  }

  return result;
}

static CURLcode quote_error(struct Curl_easy *data,
                            struct ssh_conn *sshc)
{
  failf(data, "Suspicious data after the command line");
  curlx_safefree(sshc->quote_path1);
  curlx_safefree(sshc->quote_path2);
  return CURLE_QUOTE_ERROR;
}

static CURLcode sftp_quote(struct Curl_easy *data,
                           struct ssh_conn *sshc,
                           struct SSHPROTO *sshp)
{
  const char *cp;
  CURLcode result = CURLE_OK;

  /*
   * Support some of the "FTP" commands
   *
   * 'sshc->quote_item' is already verified to be non-NULL before it
   * switched to this state.
   */
  const char *cmd = sshc->quote_item->data;
  sshc->acceptfail = FALSE;

  /* if a command starts with an asterisk, which a legal SFTP command never
     can, the command is allowed to fail without it causing any
     aborts or cancels etc. It causes libcurl to act as if the command
     is successful, whatever the server responds. */

  if(cmd[0] == '*') {
    cmd++;
    sshc->acceptfail = TRUE;
  }

  if(curl_strequal("pwd", cmd)) {
    /* output debug output if that is requested */
    char *tmp = curl_maprintf("257 \"%s\" is current directory.\n",
                              sshp->path);
    if(!tmp)
      return CURLE_OUT_OF_MEMORY;
    Curl_debug(data, CURLINFO_HEADER_OUT, "PWD\n", 4);
    Curl_debug(data, CURLINFO_HEADER_IN, tmp, strlen(tmp));

    /* this sends an FTP-like "header" to the header callback so that
       the current directory can be read similar to how it is read when
       using ordinary FTP. */
    result = Curl_client_write(data, CLIENTWRITE_HEADER, tmp, strlen(tmp));
    curlx_free(tmp);
    if(!result)
      myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
    return result;
  }

  /*
   * the arguments following the command must be separated from the
   * command with a space so we can check for it unconditionally
   */
  cp = strchr(cmd, ' ');
  if(!cp) {
    failf(data, "Syntax error command '%s', missing parameter", cmd);
    return result;
  }

  /*
   * also, every command takes at least one argument so we get that
   * first argument right now
   */
  result = Curl_get_pathname(&cp, &sshc->quote_path1, sshc->homedir);
  if(result) {
    if(result != CURLE_OUT_OF_MEMORY)
      failf(data, "Syntax error: Bad first parameter to '%s'", cmd);
    return result;
  }

  /*
   * SFTP is a binary protocol, so we do not send text commands to the server.
   * Instead, we scan for commands used by OpenSSH's sftp program and call the
   * appropriate libssh2 functions.
   */
  if(!strncmp(cmd, "chgrp ", 6) ||
     !strncmp(cmd, "chmod ", 6) ||
     !strncmp(cmd, "chown ", 6) ||
     !strncmp(cmd, "atime ", 6) ||
     !strncmp(cmd, "mtime ", 6)) {
    /* attribute change */

    /* sshc->quote_path1 contains the mode to set */
    /* get the destination */
    result = Curl_get_pathname(&cp, &sshc->quote_path2, sshc->homedir);
    if(result) {
      if(result != CURLE_OUT_OF_MEMORY)
        failf(data, "Syntax error in %s: Bad second parameter", cmd);
      curlx_safefree(sshc->quote_path1);
      return result;
    }
    if(*cp)
      return quote_error(data, sshc);

    memset(&sshp->quote_attrs, 0, sizeof(LIBSSH2_SFTP_ATTRIBUTES));
    myssh_to(data, sshc, SSH_SFTP_QUOTE_STAT);
    return result;
  }
  if(!strncmp(cmd, "ln ", 3) ||
     !strncmp(cmd, "symlink ", 8)) {
    /* symbolic linking */
    /* sshc->quote_path1 is the source */
    /* get the destination */
    result = Curl_get_pathname(&cp, &sshc->quote_path2, sshc->homedir);
    if(result) {
      if(result != CURLE_OUT_OF_MEMORY)
        failf(data, "Syntax error in ln/symlink: Bad second parameter");
      curlx_safefree(sshc->quote_path1);
      return result;
    }
    if(*cp)
      return quote_error(data, sshc);
    myssh_to(data, sshc, SSH_SFTP_QUOTE_SYMLINK);
    return result;
  }
  else if(!strncmp(cmd, "mkdir ", 6)) {
    if(*cp)
      return quote_error(data, sshc);
    /* create directory */
    myssh_to(data, sshc, SSH_SFTP_QUOTE_MKDIR);
    return result;
  }
  else if(!strncmp(cmd, "rename ", 7)) {
    /* rename file */
    /* first param is the source path */
    /* second param is the dest. path */
    result = Curl_get_pathname(&cp, &sshc->quote_path2, sshc->homedir);
    if(result) {
      if(result != CURLE_OUT_OF_MEMORY)
        failf(data, "Syntax error in rename: Bad second parameter");
      curlx_safefree(sshc->quote_path1);
      return result;
    }
    if(*cp)
      return quote_error(data, sshc);
    myssh_to(data, sshc, SSH_SFTP_QUOTE_RENAME);
    return result;
  }
  else if(!strncmp(cmd, "rmdir ", 6)) {
    if(*cp)
      return quote_error(data, sshc);
    /* delete directory */
    myssh_to(data, sshc, SSH_SFTP_QUOTE_RMDIR);
    return result;
  }
  else if(!strncmp(cmd, "rm ", 3)) {
    if(*cp)
      return quote_error(data, sshc);
    myssh_to(data, sshc, SSH_SFTP_QUOTE_UNLINK);
    return result;
  }
  else if(!strncmp(cmd, "statvfs ", 8)) {
    if(*cp)
      return quote_error(data, sshc);
    myssh_to(data, sshc, SSH_SFTP_QUOTE_STATVFS);
    return result;
  }

  failf(data, "Unknown SFTP command");
  curlx_safefree(sshc->quote_path1);
  curlx_safefree(sshc->quote_path2);
  return CURLE_QUOTE_ERROR;
}

static CURLcode sftp_upload_init(struct Curl_easy *data,
                                 struct ssh_conn *sshc,
                                 struct SSHPROTO *sshp,
                                 bool *blockp)
{
  unsigned long flags;

  /*
   * NOTE!!!  libssh2 requires that the destination path is a full path
   *          that includes the destination file and name OR ends in a "/"
   *          If this is not done the destination file is named the
   *          same name as the last directory in the path.
   */

  if(data->state.resume_from) {
    LIBSSH2_SFTP_ATTRIBUTES attrs;
    if(data->state.resume_from < 0) {
      int rc = libssh2_sftp_stat_ex(sshc->sftp_session, sshp->path,
                                    curlx_uztoui(strlen(sshp->path)),
                                    LIBSSH2_SFTP_STAT, &attrs);
      if(rc == LIBSSH2_ERROR_EAGAIN) {
        *blockp = TRUE;
        return CURLE_OK;
      }
      if(rc) {
        data->state.resume_from = 0;
      }
      else {
        curl_off_t size = attrs.filesize;
        if(size < 0) {
          failf(data, "Bad file size (%" FMT_OFF_T ")", size);
          return CURLE_BAD_DOWNLOAD_RESUME;
        }
        data->state.resume_from = attrs.filesize;
      }
    }
  }

  if(data->set.remote_append) {
    /* True append mode: create if nonexisting */
    flags = LIBSSH2_FXF_WRITE | LIBSSH2_FXF_CREAT | LIBSSH2_FXF_APPEND;
  }
  else if(data->state.resume_from > 0) {
    /*
     * Resume MUST NOT use APPEND; some servers force writes to EOF when
     * APPEND is set, ignoring a prior seek().
     */
    flags = LIBSSH2_FXF_WRITE;
  }
  else {
    /* Clear file before writing (normal behavior) */
    flags = LIBSSH2_FXF_WRITE | LIBSSH2_FXF_CREAT | LIBSSH2_FXF_TRUNC;
  }

  sshc->sftp_handle =
    libssh2_sftp_open_ex(sshc->sftp_session, sshp->path,
                         curlx_uztoui(strlen(sshp->path)),
                         flags, (long)data->set.new_file_perms,
                         LIBSSH2_SFTP_OPENFILE);

  if(!sshc->sftp_handle) {
    CURLcode result;
    unsigned long sftperr;
    int rc = libssh2_session_last_errno(sshc->ssh_session);

    if(LIBSSH2_ERROR_EAGAIN == rc) {
      *blockp = TRUE;
      return CURLE_OK;
    }

    if(LIBSSH2_ERROR_SFTP_PROTOCOL == rc)
      /* only when there was an SFTP protocol error can we extract
         the sftp error! */
      sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    else
      sftperr = LIBSSH2_FX_OK; /* not an sftp error at all */

    if(sshc->secondCreateDirs) {
      myssh_to(data, sshc, SSH_SFTP_CLOSE);
      failf(data, "Creating the dir/file failed: %s",
            sftp_libssh2_strerror(sftperr));
      return sftp_libssh2_error_to_CURLE(sftperr);
    }
    if((sftperr == LIBSSH2_FX_NO_SUCH_FILE ||
        sftperr == LIBSSH2_FX_FAILURE ||
        sftperr == LIBSSH2_FX_NO_SUCH_PATH) &&
       data->set.ftp_create_missing_dirs &&
       (strlen(sshp->path) > 1)) {
      /* try to create the path remotely */
      sshc->secondCreateDirs = 1;
      myssh_to(data, sshc, SSH_SFTP_CREATE_DIRS_INIT);
      return CURLE_OK;
    }
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    result = sftp_libssh2_error_to_CURLE(sftperr);
    if(!result) {
      /* Sometimes, for some reason libssh2_sftp_last_error() returns zero
         even though libssh2_sftp_open() failed previously! We need to
         work around that! */
      result = CURLE_SSH;
      sftperr = LIBSSH2_FX_OK;
    }
    failf(data, "Upload failed: %s (%lu/%d)",
          sftperr != LIBSSH2_FX_OK ?
          sftp_libssh2_strerror(sftperr) : "ssh error",
          sftperr, rc);
    return result;
  }

  /* If we have a restart point then we need to seek to the correct
     Skip if in explicit remote append mode. */
  if(data->state.resume_from > 0 && !data->set.remote_append) {
    int seekerr = CURL_SEEKFUNC_OK;
    /* Let's read off the proper amount of bytes from the input. */
    if(data->set.seek_func) {
      Curl_set_in_callback(data, TRUE);
      seekerr = data->set.seek_func(data->set.seek_client,
                                    data->state.resume_from, SEEK_SET);
      Curl_set_in_callback(data, FALSE);
    }

    if(seekerr != CURL_SEEKFUNC_OK) {
      curl_off_t passed = 0;

      if(seekerr != CURL_SEEKFUNC_CANTSEEK) {
        failf(data, "Could not seek stream");
        return CURLE_FTP_COULDNT_USE_REST;
      }
      /* seekerr == CURL_SEEKFUNC_CANTSEEK (cannot seek to offset) */
      do {
        char scratch[4 * 1024];
        size_t readthisamountnow =
          (data->state.resume_from - passed >
           (curl_off_t)sizeof(scratch)) ?
          sizeof(scratch) : curlx_sotouz(data->state.resume_from - passed);

        size_t actuallyread;
        Curl_set_in_callback(data, TRUE);
        actuallyread = data->state.fread_func(scratch, 1,
                                              readthisamountnow,
                                              data->state.in);
        Curl_set_in_callback(data, FALSE);

        passed += actuallyread;
        if((actuallyread == 0) || (actuallyread > readthisamountnow)) {
          /* this checks for greater-than only to make sure that the
             CURL_READFUNC_ABORT return code still aborts */
          failf(data, "Failed to read data");
          return CURLE_FTP_COULDNT_USE_REST;
        }
      } while(passed < data->state.resume_from);
    }

    /* now, decrease the size of the read */
    if(data->state.infilesize > 0) {
      data->state.infilesize -= data->state.resume_from;
      data->req.size = data->state.infilesize;
      Curl_pgrsSetUploadSize(data, data->state.infilesize);
    }

    libssh2_sftp_seek64(sshc->sftp_handle,
                        (libssh2_uint64_t)data->state.resume_from);
  }
  if(data->state.infilesize > 0) {
    data->req.size = data->state.infilesize;
    Curl_pgrsSetUploadSize(data, data->state.infilesize);
  }
  /* upload data */
  Curl_xfer_setup_send(data, FIRSTSOCKET);

  /* not set by Curl_xfer_setup to preserve io_flags */
  data->conn->recv_idx = FIRSTSOCKET;

  /* since we do not really wait for anything at this point, we want the
     state machine to move on as soon as possible so mark this as dirty */
  Curl_multi_mark_dirty(data);

  myssh_to(data, sshc, SSH_STOP);
  return CURLE_OK;
}

static CURLcode ssh_state_pkey_init(struct Curl_easy *data,
                                    struct ssh_conn *sshc)
{
  /*
   * Check the supported auth types in the order I feel is most secure
   * with the requested type of authentication
   */
  sshc->authed = FALSE;

  if((data->set.ssh_auth_types & CURLSSH_AUTH_PUBLICKEY) &&
     (strstr(sshc->authlist, "publickey") != NULL)) {
    bool out_of_memory = FALSE;

    sshc->rsa_pub = sshc->rsa = NULL;

    if(data->set.str[STRING_SSH_PRIVATE_KEY]) {
      sshc->rsa = curlx_strdup(data->set.str[STRING_SSH_PRIVATE_KEY]);
      if(!sshc->rsa)
        out_of_memory = TRUE;
    }
    else {
      /* To ponder about: should really the lib be messing about with the
         HOME environment variable etc? */
      char *home = curl_getenv("HOME");
      curlx_struct_stat sbuf;

      /* If no private key file is specified, try some common paths. */
      if(home) {
        /* Try ~/.ssh first. */
        sshc->rsa = curl_maprintf("%s/.ssh/id_rsa", home);
        if(!sshc->rsa)
          out_of_memory = TRUE;
        else if(curlx_stat(sshc->rsa, &sbuf)) {
          curlx_free(sshc->rsa);
          sshc->rsa = curl_maprintf("%s/.ssh/id_dsa", home);
          if(!sshc->rsa)
            out_of_memory = TRUE;
          else if(curlx_stat(sshc->rsa, &sbuf)) {
            curlx_safefree(sshc->rsa);
          }
        }
        curlx_free(home);
      }
      if(!out_of_memory && !sshc->rsa) {
        /* Nothing found; try the current dir. */
        sshc->rsa = curlx_strdup("id_rsa");
        if(sshc->rsa && curlx_stat(sshc->rsa, &sbuf)) {
          curlx_free(sshc->rsa);
          sshc->rsa = curlx_strdup("id_dsa");
          if(sshc->rsa && curlx_stat(sshc->rsa, &sbuf)) {
            curlx_free(sshc->rsa);
            /* Out of guesses. Set to the empty string to avoid
             * surprising info messages. */
            sshc->rsa = curlx_strdup("");
          }
        }
      }
    }

    /*
     * Unless the user explicitly specifies a public key file, let
     * libssh2 extract the public key from the private key file.
     * This is done by passing sshc->rsa_pub = NULL.
     */
    if(!out_of_memory && data->set.str[STRING_SSH_PUBLIC_KEY] &&
       /* treat empty string the same way as NULL */
       data->set.str[STRING_SSH_PUBLIC_KEY][0]) {
      sshc->rsa_pub = curlx_strdup(data->set.str[STRING_SSH_PUBLIC_KEY]);
      if(!sshc->rsa_pub)
        out_of_memory = TRUE;
    }

    if(out_of_memory || !sshc->rsa) {
      curlx_safefree(sshc->rsa);
      curlx_safefree(sshc->rsa_pub);
      myssh_to(data, sshc, SSH_SESSION_FREE);
      return CURLE_OUT_OF_MEMORY;
    }

    sshc->passphrase = data->set.ssl.key_passwd;
    if(!sshc->passphrase)
      sshc->passphrase = "";

    if(sshc->rsa_pub)
      infof(data, "Using SSH public key file '%s'", sshc->rsa_pub);
    infof(data, "Using SSH private key file '%s'", sshc->rsa);

    myssh_to(data, sshc, SSH_AUTH_PKEY);
  }
  else {
    myssh_to(data, sshc, SSH_AUTH_PASS_INIT);
  }
  return CURLE_OK;
}

static CURLcode sftp_quote_stat(struct Curl_easy *data,
                                struct ssh_conn *sshc,
                                struct SSHPROTO *sshp,
                                bool *blockp)
{
  const char *cmd = sshc->quote_item->data;
  sshc->acceptfail = FALSE;

  /* if a command starts with an asterisk, which a legal SFTP command never
     can, the command is allowed to fail without it causing any aborts or
     cancels etc. It causes libcurl to act as if the command is
     successful, whatever the server responds. */

  if(cmd[0] == '*') {
    cmd++;
    sshc->acceptfail = TRUE;
  }

  if(!!strncmp(cmd, "chmod", 5)) {
    /* Since chown and chgrp only set owner OR group but libssh2 wants to set
     * them both at once, we need to obtain the current ownership first. This
     * takes an extra protocol round trip.
     */
    int rc = libssh2_sftp_stat_ex(sshc->sftp_session, sshc->quote_path2,
                                  curlx_uztoui(strlen(sshc->quote_path2)),
                                  LIBSSH2_SFTP_STAT,
                                  &sshp->quote_attrs);
    if(rc == LIBSSH2_ERROR_EAGAIN) {
      *blockp = TRUE;
      return CURLE_OK;
    }
    if(rc && !sshc->acceptfail) { /* get those attributes */
      unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
      failf(data, "Attempt to get SFTP stats failed: %s",
            sftp_libssh2_strerror(sftperr));
      goto fail;
    }
  }

  /* Now set the new attributes... */
  if(!strncmp(cmd, "chgrp", 5)) {
    const char *p = sshc->quote_path1;
    curl_off_t gid;
    if(!curlx_str_number(&p, &gid, ULONG_MAX)) {
      sshp->quote_attrs.gid = (unsigned long)gid;
      sshp->quote_attrs.flags = LIBSSH2_SFTP_ATTR_UIDGID;
    }
    else if(!sshc->acceptfail) {
      failf(data, "Syntax error: chgrp gid not a number");
      goto fail;
    }
  }
  else if(!strncmp(cmd, "chmod", 5)) {
    curl_off_t perms;
    const char *p = sshc->quote_path1;
    /* permissions are octal */
    if(curlx_str_octal(&p, &perms, 07777)) {
      failf(data, "Syntax error: chmod permissions not a number");
      goto fail;
    }

    sshp->quote_attrs.permissions = (unsigned long)perms;
    sshp->quote_attrs.flags = LIBSSH2_SFTP_ATTR_PERMISSIONS;
  }
  else if(!strncmp(cmd, "chown", 5)) {
    const char *p = sshc->quote_path1;
    curl_off_t uid;
    if(!curlx_str_number(&p, &uid, ULONG_MAX)) {
      sshp->quote_attrs.uid = (unsigned long)uid;
      sshp->quote_attrs.flags = LIBSSH2_SFTP_ATTR_UIDGID;
    }
    else if(!sshc->acceptfail) {
      failf(data, "Syntax error: chown uid not a number");
      goto fail;
    }
  }
  else if(!strncmp(cmd, "atime", 5) ||
          !strncmp(cmd, "mtime", 5)) {
    time_t date;
    bool fail = FALSE;

    if(Curl_getdate_capped(sshc->quote_path1, &date)) {
      failf(data, "incorrect date format for %.*s", 5, cmd);
      fail = TRUE;
    }
#if SIZEOF_TIME_T > SIZEOF_LONG
    if(date > 0xffffffff) {
      /* if 'long' cannot hold >32-bit, this date cannot be sent */
      failf(data, "date overflow");
      fail = TRUE;
    }
#endif
    if(fail)
      goto fail;
    if(!strncmp(cmd, "atime", 5))
      sshp->quote_attrs.atime = (unsigned long)date;
    else /* mtime */
      sshp->quote_attrs.mtime = (unsigned long)date;

    sshp->quote_attrs.flags = LIBSSH2_SFTP_ATTR_ACMODTIME;
  }

  /* Now send the completed structure... */
  myssh_to(data, sshc, SSH_SFTP_QUOTE_SETSTAT);
  return CURLE_OK;
fail:
  curlx_safefree(sshc->quote_path1);
  curlx_safefree(sshc->quote_path2);
  return CURLE_QUOTE_ERROR;
}

static CURLcode sftp_download_stat(struct Curl_easy *data,
                                   struct ssh_conn *sshc,
                                   struct SSHPROTO *sshp,
                                   bool *blockp)
{
  LIBSSH2_SFTP_ATTRIBUTES attrs;
  int rc = libssh2_sftp_stat_ex(sshc->sftp_session, sshp->path,
                                curlx_uztoui(strlen(sshp->path)),
                                LIBSSH2_SFTP_STAT, &attrs);
  if(rc == LIBSSH2_ERROR_EAGAIN) {
    *blockp = TRUE;
    return CURLE_OK;
  }
  if(rc ||
     !(attrs.flags & LIBSSH2_SFTP_ATTR_SIZE) ||
     (attrs.filesize == 0)) {
    /*
     * libssh2_sftp_open() did not return an error, so maybe the server
     * does not support stat()
     * OR the server does not return a file size with a stat()
     * OR file size is 0
     */
    data->req.size = -1;
    data->req.maxdownload = -1;
    Curl_pgrsSetDownloadSize(data, -1);
    attrs.filesize = 0; /* might be uninitialized but is read below */
  }
  else {
    curl_off_t size = attrs.filesize;

    if(size < 0) {
      failf(data, "Bad file size (%" FMT_OFF_T ")", size);
      return CURLE_BAD_DOWNLOAD_RESUME;
    }
    if(data->state.use_range) {
      curl_off_t from;
      CURLcode result = Curl_ssh_range(data, data->state.range, size,
                                       &from, &size);
      if(result)
        return result;

      libssh2_sftp_seek64(sshc->sftp_handle, (libssh2_uint64_t)from);
    }
    data->req.size = size;
    data->req.maxdownload = size;
    Curl_pgrsSetDownloadSize(data, size);
  }

  /* We can resume if we can seek to the resume position */
  if(data->state.resume_from) {
    if(data->state.resume_from < 0) {
      /* We are supposed to download the last abs(from) bytes */
      if((curl_off_t)attrs.filesize < -data->state.resume_from) {
        failf(data, "Offset (%" FMT_OFF_T ") was beyond file size (%"
              FMT_OFF_T ")",
              data->state.resume_from, (curl_off_t)attrs.filesize);
        return CURLE_BAD_DOWNLOAD_RESUME;
      }
      /* download from where? */
      data->state.resume_from += attrs.filesize;
    }
    else {
      if((curl_off_t)attrs.filesize < data->state.resume_from) {
        failf(data, "Offset (%" FMT_OFF_T
              ") was beyond file size (%" FMT_OFF_T ")",
              data->state.resume_from, (curl_off_t)attrs.filesize);
        return CURLE_BAD_DOWNLOAD_RESUME;
      }
    }
    /* Now store the number of bytes we are expected to download */
    data->req.size = attrs.filesize - data->state.resume_from;
    data->req.maxdownload = attrs.filesize - data->state.resume_from;
    Curl_pgrsSetDownloadSize(data, attrs.filesize - data->state.resume_from);
    libssh2_sftp_seek64(sshc->sftp_handle,
                        (libssh2_uint64_t)data->state.resume_from);
  }

  /* Setup the actual download */
  if(data->req.size == 0) {
    /* no data to transfer */
    Curl_xfer_setup_nop(data);
    infof(data, "File already completely downloaded");
    myssh_to(data, sshc, SSH_STOP);
    return CURLE_OK;
  }
  Curl_xfer_setup_recv(data, FIRSTSOCKET, data->req.size);

  /* not set by Curl_xfer_setup to preserve io_flags */
  data->conn->send_idx = 0;

  myssh_to(data, sshc, SSH_STOP);

  return CURLE_OK;
}

static CURLcode sftp_readdir(struct Curl_easy *data,
                             struct ssh_conn *sshc,
                             struct SSHPROTO *sshp,
                             bool *blockp)
{
  CURLcode result = CURLE_OK;
  int rc = libssh2_sftp_readdir_ex(sshc->sftp_handle,
                                   sshp->readdir_filename, CURL_PATH_MAX,
                                   sshp->readdir_longentry, CURL_PATH_MAX,
                                   &sshp->readdir_attrs);
  if(rc == LIBSSH2_ERROR_EAGAIN) {
    *blockp = TRUE;
    return result;
  }
  if(rc > 0) {
    size_t readdir_len = (size_t)rc;
    sshp->readdir_filename[readdir_len] = '\0';

    if(data->set.list_only) {
      result = Curl_client_write(data, CLIENTWRITE_BODY,
                                 sshp->readdir_filename,
                                 readdir_len);
      if(!result)
        result = Curl_client_write(data, CLIENTWRITE_BODY, "\n", 1);
      if(result)
        return result;
    }
    else {
      result = curlx_dyn_add(&sshp->readdir, sshp->readdir_longentry);

      if(!result) {
        if((sshp->readdir_attrs.flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) &&
           ((sshp->readdir_attrs.permissions & LIBSSH2_SFTP_S_IFMT) ==
            LIBSSH2_SFTP_S_IFLNK)) {
          result = curlx_dyn_addf(&sshp->readdir_link, "%s%s", sshp->path,
                                  sshp->readdir_filename);
          myssh_to(data, sshc, SSH_SFTP_READDIR_LINK);
        }
        else {
          myssh_to(data, sshc, SSH_SFTP_READDIR_BOTTOM);
        }
      }
      return result;
    }
  }
  else if(!rc) {
    myssh_to(data, sshc, SSH_SFTP_READDIR_DONE);
  }
  else {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    result = sftperr ? sftp_libssh2_error_to_CURLE(sftperr) : CURLE_SSH;
    failf(data, "Could not open remote file for reading: %s :: %d",
          sftp_libssh2_strerror(sftperr),
          libssh2_session_last_errno(sshc->ssh_session));
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
  }
  return result;
}

static CURLcode ssh_state_init(struct Curl_easy *data,
                               struct ssh_conn *sshc)
{
  CURLcode result;
  sshc->secondCreateDirs = 0;
  sshc->nextstate = SSH_NO_STATE;

  /* Set libssh2 to non-blocking, since everything internally is
     non-blocking */
  libssh2_session_set_blocking(sshc->ssh_session, 0);

  result = ssh_force_knownhost_key_type(data, sshc);
  if(result)
    myssh_to(data, sshc, SSH_SESSION_FREE);
  else
    myssh_to(data, sshc, SSH_S_STARTUP);
  return result;
}

static CURLcode ssh_state_startup(struct Curl_easy *data,
                                  struct ssh_conn *sshc)
{
  struct connectdata *conn = data->conn;
  int rc = libssh2_session_handshake(sshc->ssh_session,
                                     conn->sock[FIRSTSOCKET]);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc) {
    char *err_msg = NULL;
    (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
    failf(data, "Failure establishing ssh session: %d, %s", rc, err_msg);

    myssh_to(data, sshc, SSH_SESSION_FREE);
    return CURLE_FAILED_INIT;
  }

  myssh_to(data, sshc, SSH_HOSTKEY);
  return CURLE_OK;
}

static CURLcode ssh_state_hostkey(struct Curl_easy *data,
                                  struct ssh_conn *sshc)
{
  /*
   * Before we authenticate we should check the hostkey's fingerprint
   * against our known hosts. How that is handled (reading from file,
   * whatever) is up to us.
   */
  CURLcode result = ssh_check_fingerprint(data, sshc);
  if(!result)
    myssh_to(data, sshc, SSH_AUTHLIST);
  return result;
}

static CURLcode ssh_state_authlist(struct Curl_easy *data,
                                   struct ssh_conn *sshc)
{
  /*
   * Figure out authentication methods
   * NB: As soon as we have provided a username to an openssh server we
   * must never change it later. Thus, always specify the correct username
   * here, even though the libssh2 docs kind of indicate that it should be
   * possible to get a 'generic' list (not user-specific) of authentication
   * methods, presumably with a blank username. That does not work in my
   * experience.
   * Therefore always specify it here.
   */
  struct connectdata *conn = data->conn;
  sshc->authlist = libssh2_userauth_list(sshc->ssh_session,
                                         conn->user,
                                         curlx_uztoui(strlen(conn->user)));

  if(!sshc->authlist) {
    int rc;
    if(libssh2_userauth_authenticated(sshc->ssh_session)) {
      sshc->authed = TRUE;
      infof(data, "SSH user accepted with no authentication");
      myssh_to(data, sshc, SSH_AUTH_DONE);
      return CURLE_OK;
    }
    rc = libssh2_session_last_errno(sshc->ssh_session);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    myssh_to(data, sshc, SSH_SESSION_FREE);
    return libssh2_session_error_to_CURLE(rc);
  }
  infof(data, "SSH authentication methods available: %s", sshc->authlist);

  myssh_to(data, sshc, SSH_AUTH_PKEY_INIT);
  return CURLE_OK;
}

static CURLcode ssh_state_auth_pkey(struct Curl_easy *data,
                                    struct ssh_conn *sshc)
{
  /* The function below checks if the files exists, no need to stat() here.
   */
  struct connectdata *conn = data->conn;
  int rc =
    libssh2_userauth_publickey_fromfile_ex(sshc->ssh_session,
                                           conn->user,
                                           curlx_uztoui(
                                             strlen(conn->user)),
                                           sshc->rsa_pub,
                                           sshc->rsa, sshc->passphrase);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  curlx_safefree(sshc->rsa_pub);
  curlx_safefree(sshc->rsa);

  if(rc == 0) {
    sshc->authed = TRUE;
    infof(data, "Initialized SSH public key authentication");
    myssh_to(data, sshc, SSH_AUTH_DONE);
  }
  else {
    char *err_msg = NULL;
    char unknown[] = "Reason unknown (-1)";
    if(rc == -1) {
      /* No error message has been set and the last set error message, if
         any, is from a previous error so ignore it. #11837 */
      err_msg = unknown;
    }
    else {
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
    }
    infof(data, "SSH public key authentication failed: %s", err_msg);
    myssh_to(data, sshc, SSH_AUTH_PASS_INIT);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_auth_pass_init(struct Curl_easy *data,
                                         struct ssh_conn *sshc)
{
  if((data->set.ssh_auth_types & CURLSSH_AUTH_PASSWORD) &&
     (strstr(sshc->authlist, "password") != NULL)) {
    myssh_to(data, sshc, SSH_AUTH_PASS);
  }
  else {
    myssh_to(data, sshc, SSH_AUTH_HOST_INIT);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_auth_pass(struct Curl_easy *data,
                                    struct ssh_conn *sshc)
{
  struct connectdata *conn = data->conn;
  int rc =
    libssh2_userauth_password_ex(sshc->ssh_session, conn->user,
                                 curlx_uztoui(strlen(conn->user)),
                                 conn->passwd,
                                 curlx_uztoui(strlen(conn->passwd)),
                                 NULL);
  if(rc == LIBSSH2_ERROR_EAGAIN) {
    return CURLE_AGAIN;
  }
  if(rc == 0) {
    sshc->authed = TRUE;
    infof(data, "Initialized password authentication");
    myssh_to(data, sshc, SSH_AUTH_DONE);
  }
  else {
    myssh_to(data, sshc, SSH_AUTH_HOST_INIT);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_auth_host_init(struct Curl_easy *data,
                                         struct ssh_conn *sshc)
{
  if((data->set.ssh_auth_types & CURLSSH_AUTH_HOST) &&
     (strstr(sshc->authlist, "hostbased") != NULL)) {
    myssh_to(data, sshc, SSH_AUTH_HOST);
  }
  else {
    myssh_to(data, sshc, SSH_AUTH_AGENT_INIT);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_auth_agent_init(struct Curl_easy *data,
                                          struct ssh_conn *sshc)
{
  int rc = 0;
  if((data->set.ssh_auth_types & CURLSSH_AUTH_AGENT) &&
     (strstr(sshc->authlist, "publickey") != NULL)) {

    /* Connect to the ssh-agent */
    /* The agent could be shared by a curl thread i believe
       but nothing obvious as keys can be added/removed at any time */
    if(!sshc->ssh_agent) {
      sshc->ssh_agent = libssh2_agent_init(sshc->ssh_session);
      if(!sshc->ssh_agent) {
        infof(data, "Could not create agent object");

        myssh_to(data, sshc, SSH_AUTH_KEY_INIT);
        return CURLE_OK;
      }
    }

    rc = libssh2_agent_connect(sshc->ssh_agent);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;
    if(rc < 0) {
      infof(data, "Failure connecting to agent");
      myssh_to(data, sshc, SSH_AUTH_KEY_INIT);
    }
    else {
      myssh_to(data, sshc, SSH_AUTH_AGENT_LIST);
    }
  }
  else
    myssh_to(data, sshc, SSH_AUTH_KEY_INIT);
  return CURLE_OK;
}

static CURLcode ssh_state_auth_agent_list(struct Curl_easy *data,
                                          struct ssh_conn *sshc)
{
  int rc = libssh2_agent_list_identities(sshc->ssh_agent);

  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;
  if(rc < 0) {
    infof(data, "Failure requesting identities to agent");
    myssh_to(data, sshc, SSH_AUTH_KEY_INIT);
  }
  else {
    myssh_to(data, sshc, SSH_AUTH_AGENT);
    sshc->sshagent_prev_identity = NULL;
  }
  return CURLE_OK;
}

static CURLcode ssh_state_auth_agent(struct Curl_easy *data,
                                     struct ssh_conn *sshc)
{
  /* as prev_identity evolves only after an identity user auth finished we
     can safely request it again as long as EAGAIN is returned here or by
     libssh2_agent_userauth */
  int rc = libssh2_agent_get_identity(sshc->ssh_agent,
                                      &sshc->sshagent_identity,
                                      sshc->sshagent_prev_identity);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc == 0) {
    struct connectdata *conn = data->conn;
    rc = libssh2_agent_userauth(sshc->ssh_agent, conn->user,
                                sshc->sshagent_identity);

    if(rc < 0) {
      if(rc != LIBSSH2_ERROR_EAGAIN) {
        /* tried and failed? go to next identity */
        sshc->sshagent_prev_identity = sshc->sshagent_identity;
        return CURLE_OK;
      }
      return CURLE_AGAIN;
    }
  }

  if(rc < 0)
    infof(data, "Failure requesting identities to agent");
  else if(rc == 1)
    infof(data, "No identity would match");

  if(rc == LIBSSH2_ERROR_NONE) {
    sshc->authed = TRUE;
    infof(data, "Agent based authentication successful");
    myssh_to(data, sshc, SSH_AUTH_DONE);
  }
  else {
    myssh_to(data, sshc, SSH_AUTH_KEY_INIT);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_auth_key_init(struct Curl_easy *data,
                                        struct ssh_conn *sshc)
{
  if((data->set.ssh_auth_types & CURLSSH_AUTH_KEYBOARD) &&
     (strstr(sshc->authlist, "keyboard-interactive") != NULL)) {
    myssh_to(data, sshc, SSH_AUTH_KEY);
  }
  else {
    myssh_to(data, sshc, SSH_AUTH_DONE);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_auth_key(struct Curl_easy *data,
                                   struct ssh_conn *sshc)
{
  /* Authentication failed. Continue with keyboard-interactive now. */
  struct connectdata *conn = data->conn;
  int rc =
    libssh2_userauth_keyboard_interactive_ex(sshc->ssh_session,
                                             conn->user,
                                             curlx_uztoui(
                                               strlen(conn->user)),
                                             &kbd_callback);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc == 0) {
    sshc->authed = TRUE;
    infof(data, "Initialized keyboard interactive authentication");
    myssh_to(data, sshc, SSH_AUTH_DONE);
    return CURLE_OK;
  }
  return CURLE_LOGIN_DENIED;
}

static CURLcode ssh_state_auth_done(struct Curl_easy *data,
                                    struct ssh_conn *sshc)
{
  struct connectdata *conn = data->conn;
  if(!sshc->authed) {
    failf(data, "Authentication failure");
    myssh_to(data, sshc, SSH_SESSION_FREE);
    return CURLE_LOGIN_DENIED;
  }

  /*
   * At this point we have an authenticated ssh session.
   */
  infof(data, "Authentication complete");

  Curl_pgrsTime(data, TIMER_APPCONNECT); /* SSH is connected */

  data->conn->recv_idx = FIRSTSOCKET;
  conn->send_idx = -1;

  if(conn->scheme->protocol == CURLPROTO_SFTP) {
    myssh_to(data, sshc, SSH_SFTP_INIT);
    return CURLE_OK;
  }
  infof(data, "SSH CONNECT phase done");
  myssh_to(data, sshc, SSH_STOP);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_init(struct Curl_easy *data,
                                    struct ssh_conn *sshc)
{
  /*
   * Start the libssh2 sftp session
   */
  sshc->sftp_session = libssh2_sftp_init(sshc->ssh_session);
  if(!sshc->sftp_session) {
    char *err_msg = NULL;
    if(libssh2_session_last_errno(sshc->ssh_session) ==
       LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
    failf(data, "Failure initializing sftp session: %s", err_msg);
    myssh_to(data, sshc, SSH_SESSION_FREE);
    return CURLE_FAILED_INIT;
  }
  myssh_to(data, sshc, SSH_SFTP_REALPATH);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_realpath(struct Curl_easy *data,
                                        struct ssh_conn *sshc,
                                        struct SSHPROTO *sshp)
{
  /*
   * Get the "home" directory
   */
  int rc;

  if(!sshp)
    return CURLE_FAILED_INIT;

  rc = libssh2_sftp_symlink_ex(sshc->sftp_session, ".",
                               curlx_uztoui(strlen(".")),
                               sshp->readdir_filename, CURL_PATH_MAX,
                               LIBSSH2_SFTP_REALPATH);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  myssh_to(data, sshc, SSH_STOP);
  if(rc > 0) {
    curlx_free(sshc->homedir);
    sshc->homedir = curlx_strdup(sshp->readdir_filename);
    if(!sshc->homedir)
      return CURLE_OUT_OF_MEMORY;
    curlx_free(data->state.most_recent_ftp_entrypath);
    data->state.most_recent_ftp_entrypath = curlx_strdup(sshc->homedir);
    if(!data->state.most_recent_ftp_entrypath)
      return CURLE_OUT_OF_MEMORY;
  }
  else {
    /* Return the error type */
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    CURLcode result;
    if(sftperr)
      result = sftp_libssh2_error_to_CURLE(sftperr);
    else
      /* in this case, the error was not in the SFTP level but for example a
         time-out or similar */
      result = CURLE_SSH;
    CURL_TRC_SSH(data, "error = %lu makes libcurl = %d", sftperr, (int)result);
    return result;
  }

  /* This is the last step in the SFTP connect phase. Do note that while we
     get the homedir here, we get the "workingpath" in the DO action since the
     homedir remains the same between request but the working path does not. */
  CURL_TRC_SSH(data, "CONNECT phase done");
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_init(struct Curl_easy *data,
                                          struct ssh_conn *sshc,
                                          struct SSHPROTO *sshp)
{
  CURLcode result;

  if(!sshp)
    return CURLE_FAILED_INIT;

  result = Curl_getworkingpath(data, sshc->homedir, &sshp->path);
  if(result) {
    myssh_to(data, sshc, SSH_STOP);
    return result;
  }

  if(data->set.quote) {
    infof(data, "Sending quote commands");
    sshc->quote_item = data->set.quote;
    myssh_to(data, sshc, SSH_SFTP_QUOTE);
  }
  else {
    myssh_to(data, sshc, SSH_SFTP_GETINFO);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_postquote_init(struct Curl_easy *data,
                                              struct ssh_conn *sshc)
{
  if(data->set.postquote) {
    infof(data, "Sending quote commands");
    sshc->quote_item = data->set.postquote;
    myssh_to(data, sshc, SSH_SFTP_QUOTE);
  }
  else {
    myssh_to(data, sshc, SSH_STOP);
  }
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote(struct Curl_easy *data,
                                     struct ssh_conn *sshc,
                                     struct SSHPROTO *sshp)
{
  /* Send quote commands */
  CURLcode result;

  if(!sshp)
    return CURLE_FAILED_INIT;

  result = sftp_quote(data, sshc, sshp);
  if(result) {
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
  }
  return result;
}

static CURLcode ssh_state_sftp_next_quote(struct Curl_easy *data,
                                          struct ssh_conn *sshc)
{
  curlx_safefree(sshc->quote_path1);
  curlx_safefree(sshc->quote_path2);

  sshc->quote_item = sshc->quote_item->next;

  if(sshc->quote_item) {
    myssh_to(data, sshc, SSH_SFTP_QUOTE);
  }
  else {
    if(sshc->nextstate != SSH_NO_STATE) {
      myssh_to(data, sshc, sshc->nextstate);
      sshc->nextstate = SSH_NO_STATE;
    }
    else {
      myssh_to(data, sshc, SSH_SFTP_GETINFO);
    }
  }
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_stat(struct Curl_easy *data,
                                          struct ssh_conn *sshc,
                                          struct SSHPROTO *sshp,
                                          bool *blockp)
{
  CURLcode result;

  if(!sshp)
    return CURLE_FAILED_INIT;

  result = sftp_quote_stat(data, sshc, sshp, blockp);
  if(result) {
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
  }
  return result;
}

static CURLcode ssh_state_sftp_quote_setstat(struct Curl_easy *data,
                                             struct ssh_conn *sshc,
                                             struct SSHPROTO *sshp)
{
  int rc;

  if(!sshp)
    return CURLE_FAILED_INIT;

  rc = libssh2_sftp_stat_ex(sshc->sftp_session, sshc->quote_path2,
                            curlx_uztoui(strlen(sshc->quote_path2)),
                            LIBSSH2_SFTP_SETSTAT,
                            &sshp->quote_attrs);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc && !sshc->acceptfail) {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "Attempt to set SFTP stats for \"%s\" failed: %s",
          sshc->quote_path2, sftp_libssh2_strerror(sftperr));
    curlx_safefree(sshc->quote_path1);
    curlx_safefree(sshc->quote_path2);
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
    return CURLE_QUOTE_ERROR;
  }
  myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_symlink(struct Curl_easy *data,
                                             struct ssh_conn *sshc)
{
  int rc =
    libssh2_sftp_symlink_ex(sshc->sftp_session, sshc->quote_path1,
                            curlx_uztoui(strlen(sshc->quote_path1)),
                            sshc->quote_path2,
                            curlx_uztoui(strlen(sshc->quote_path2)),
                            LIBSSH2_SFTP_SYMLINK);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc && !sshc->acceptfail) {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "symlink \"%s\" to \"%s\" failed: %s",
          sshc->quote_path1, sshc->quote_path2,
          sftp_libssh2_strerror(sftperr));
    curlx_safefree(sshc->quote_path1);
    curlx_safefree(sshc->quote_path2);
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
    return CURLE_QUOTE_ERROR;
  }
  myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_mkdir(struct Curl_easy *data,
                                           struct ssh_conn *sshc)
{
  int rc = libssh2_sftp_mkdir_ex(sshc->sftp_session, sshc->quote_path1,
                                 curlx_uztoui(strlen(sshc->quote_path1)),
                                 (long)data->set.new_directory_perms);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc && !sshc->acceptfail) {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "mkdir \"%s\" failed: %s",
          sshc->quote_path1, sftp_libssh2_strerror(sftperr));
    curlx_safefree(sshc->quote_path1);
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
    return CURLE_QUOTE_ERROR;
  }
  myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_rename(struct Curl_easy *data,
                                            struct ssh_conn *sshc)
{
  int rc =
    libssh2_sftp_rename_ex(sshc->sftp_session, sshc->quote_path1,
                           curlx_uztoui(strlen(sshc->quote_path1)),
                           sshc->quote_path2,
                           curlx_uztoui(strlen(sshc->quote_path2)),
                           LIBSSH2_SFTP_RENAME_OVERWRITE |
                           LIBSSH2_SFTP_RENAME_ATOMIC |
                           LIBSSH2_SFTP_RENAME_NATIVE);

  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc && !sshc->acceptfail) {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "rename \"%s\" to \"%s\" failed: %s",
          sshc->quote_path1, sshc->quote_path2,
          sftp_libssh2_strerror(sftperr));
    curlx_safefree(sshc->quote_path1);
    curlx_safefree(sshc->quote_path2);
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
    return CURLE_QUOTE_ERROR;
  }
  myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_rmdir(struct Curl_easy *data,
                                           struct ssh_conn *sshc)
{
  int rc = libssh2_sftp_rmdir_ex(sshc->sftp_session, sshc->quote_path1,
                                 curlx_uztoui(strlen(sshc->quote_path1)));
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc && !sshc->acceptfail) {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "rmdir \"%s\" failed: %s",
          sshc->quote_path1, sftp_libssh2_strerror(sftperr));
    curlx_safefree(sshc->quote_path1);
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
    return CURLE_QUOTE_ERROR;
  }
  myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_unlink(struct Curl_easy *data,
                                            struct ssh_conn *sshc)
{
  int rc = libssh2_sftp_unlink_ex(sshc->sftp_session, sshc->quote_path1,
                                  curlx_uztoui(strlen(sshc->quote_path1)));
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc && !sshc->acceptfail) {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "rm \"%s\" failed: %s",
          sshc->quote_path1, sftp_libssh2_strerror(sftperr));
    curlx_safefree(sshc->quote_path1);
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
    return CURLE_QUOTE_ERROR;
  }
  myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_quote_statvfs(struct Curl_easy *data,
                                             struct ssh_conn *sshc)
{
  LIBSSH2_SFTP_STATVFS statvfs;
  int rc = libssh2_sftp_statvfs(sshc->sftp_session, sshc->quote_path1,
                                curlx_uztoui(strlen(sshc->quote_path1)),
                                &statvfs);

  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc && !sshc->acceptfail) {
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "statvfs \"%s\" failed: %s",
          sshc->quote_path1, sftp_libssh2_strerror(sftperr));
    curlx_safefree(sshc->quote_path1);
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
    return CURLE_QUOTE_ERROR;
  }
  else if(rc == 0) {
#ifdef _MSC_VER
#define CURL_LIBSSH2_VFS_SIZE_MASK "I64u"
#else
#define CURL_LIBSSH2_VFS_SIZE_MASK "llu"
#endif
    CURLcode result;
    char *tmp = curl_maprintf("statvfs:\n"
                              "f_bsize: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_frsize: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_blocks: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_bfree: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_bavail: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_files: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_ffree: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_favail: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_fsid: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_flag: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n"
                              "f_namemax: %" CURL_LIBSSH2_VFS_SIZE_MASK "\n",
                              statvfs.f_bsize, statvfs.f_frsize,
                              statvfs.f_blocks, statvfs.f_bfree,
                              statvfs.f_bavail, statvfs.f_files,
                              statvfs.f_ffree, statvfs.f_favail,
                              statvfs.f_fsid, statvfs.f_flag,
                              statvfs.f_namemax);
    if(!tmp) {
      myssh_to(data, sshc, SSH_SFTP_CLOSE);
      sshc->nextstate = SSH_NO_STATE;
      return CURLE_OUT_OF_MEMORY;
    }

    result = Curl_client_write(data, CLIENTWRITE_HEADER, tmp, strlen(tmp));
    curlx_free(tmp);
    if(result) {
      myssh_to(data, sshc, SSH_SFTP_CLOSE);
      sshc->nextstate = SSH_NO_STATE;
      return result;
    }
  }
  myssh_to(data, sshc, SSH_SFTP_NEXT_QUOTE);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_create_dirs_mkdir(struct Curl_easy *data,
                                                 struct ssh_conn *sshc,
                                                 struct SSHPROTO *sshp)
{
  /* 'mode' - parameter is preliminary - default to 0644 */
  int rc;

  if(!sshp)
    return CURLE_FAILED_INIT;

  rc = libssh2_sftp_mkdir_ex(sshc->sftp_session, sshp->path,
                             curlx_uztoui(strlen(sshp->path)),
                             (long)data->set.new_directory_perms);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  *sshc->slash_pos = '/';
  ++sshc->slash_pos;
  if(rc < 0) {
    /*
     * Abort if failure was not that the directory already exists or
     * the permission was denied (creation might succeed further down
     * the path) - retry on unspecific FAILURE also
     */
    unsigned long sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    if((sftperr != LIBSSH2_FX_FILE_ALREADY_EXISTS) &&
       (sftperr != LIBSSH2_FX_FAILURE) &&
       (sftperr != LIBSSH2_FX_PERMISSION_DENIED)) {
      myssh_to(data, sshc, SSH_SFTP_CLOSE);
      return sftp_libssh2_error_to_CURLE(sftperr);
    }
  }
  myssh_to(data, sshc, SSH_SFTP_CREATE_DIRS);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_readdir_init(struct Curl_easy *data,
                                            struct ssh_conn *sshc,
                                            struct SSHPROTO *sshp)
{
  if(!sshp)
    return CURLE_FAILED_INIT;

  Curl_pgrsSetDownloadSize(data, -1);
  if(data->req.no_body) {
    myssh_to(data, sshc, SSH_STOP);
    return CURLE_OK;
  }

  /*
   * This is a directory that we are trying to get, so produce a directory
   * listing
   */
  sshc->sftp_handle =
    libssh2_sftp_open_ex(sshc->sftp_session, sshp->path,
                         curlx_uztoui(strlen(sshp->path)),
                         0, 0, LIBSSH2_SFTP_OPENDIR);
  if(!sshc->sftp_handle) {
    unsigned long sftperr;
    if(libssh2_session_last_errno(sshc->ssh_session) == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "Could not open directory for reading: %s",
          sftp_libssh2_strerror(sftperr));
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    return sftp_libssh2_error_to_CURLE(sftperr);
  }
  myssh_to(data, sshc, SSH_SFTP_READDIR);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_readdir_link(struct Curl_easy *data,
                                            struct ssh_conn *sshc,
                                            struct SSHPROTO *sshp)
{
  CURLcode result;
  int rc;
  if(!sshp)
    return CURLE_FAILED_INIT;

  rc = libssh2_sftp_symlink_ex(sshc->sftp_session,
                               curlx_dyn_ptr(&sshp->readdir_link),
                               (unsigned int)
                               curlx_dyn_len(&sshp->readdir_link),
                               sshp->readdir_filename,
                               CURL_PATH_MAX, LIBSSH2_SFTP_READLINK);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  curlx_dyn_free(&sshp->readdir_link);

  if(rc < 0)
    return CURLE_OUT_OF_MEMORY;

  /* append filename and extra output */
  result = curlx_dyn_addf(&sshp->readdir, " -> %s", sshp->readdir_filename);
  if(result)
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
  else
    myssh_to(data, sshc, SSH_SFTP_READDIR_BOTTOM);
  return result;
}

static CURLcode ssh_state_scp_download_init(struct Curl_easy *data,
                                            struct ssh_conn *sshc,
                                            struct SSHPROTO *sshp)
{
  curl_off_t bytecount;
  libssh2_struct_stat sb;

  if(!sshp)
    return CURLE_FAILED_INIT;
  /*
   * We must check the remote file; if it is a directory no values are
   * be set in sb
   */

  /*
   * If support for >2GB files exists, use it.
   */

  /* get a fresh new channel from the ssh layer */
  memset(&sb, 0, sizeof(libssh2_struct_stat));
  sshc->ssh_channel = libssh2_scp_recv2(sshc->ssh_session, sshp->path, &sb);
  if(!sshc->ssh_channel) {
    int ssh_err;
    char *err_msg = NULL;

    if(libssh2_session_last_errno(sshc->ssh_session) ==
       LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    ssh_err = libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
    failf(data, "%s", err_msg);
    myssh_to(data, sshc, SSH_SCP_CHANNEL_FREE);
    return libssh2_session_error_to_CURLE(ssh_err);
  }

  /* download data */
  bytecount = (curl_off_t)sb.st_size;
  data->req.maxdownload = (curl_off_t)sb.st_size;
  Curl_xfer_setup_recv(data, FIRSTSOCKET, bytecount);

  /* not set by Curl_xfer_setup to preserve io_flags */
  data->conn->send_idx = 0;

  myssh_to(data, sshc, SSH_STOP);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_close(struct Curl_easy *data,
                                     struct ssh_conn *sshc,
                                     struct SSHPROTO *sshp)
{
  int rc = 0;
  if(!sshp)
    return CURLE_FAILED_INIT;
  if(sshc->sftp_handle) {
    rc = libssh2_sftp_close(sshc->sftp_handle);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    if(rc < 0) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to close libssh2 file: %d %s", rc, err_msg);
    }
    sshc->sftp_handle = NULL;
  }

  curlx_safefree(sshp->path);

  CURL_TRC_SSH(data, "SFTP DONE done");

  /* Check if nextstate is set and move .nextstate could be POSTQUOTE_INIT
     After nextstate is executed, the control should come back to
     SSH_SFTP_CLOSE to pass the correct result back */
  if(sshc->nextstate != SSH_NO_STATE &&
     sshc->nextstate != SSH_SFTP_CLOSE) {
    myssh_to(data, sshc, sshc->nextstate);
    sshc->nextstate = SSH_SFTP_CLOSE;
  }
  else
    myssh_to(data, sshc, SSH_STOP);

  return CURLE_OK;
}

static CURLcode ssh_state_sftp_shutdown(struct Curl_easy *data,
                                        struct ssh_conn *sshc)
{
  /* during times we get here due to a broken transfer and then the
     sftp_handle might not have been taken down so make sure that is done
     before we proceed */
  int rc = 0;
  if(sshc->sftp_handle) {
    rc = libssh2_sftp_close(sshc->sftp_handle);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    if(rc < 0) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to close libssh2 file: %d %s", rc, err_msg);
    }
    sshc->sftp_handle = NULL;
  }
  if(sshc->sftp_session) {
    rc = libssh2_sftp_shutdown(sshc->sftp_session);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    if(rc < 0) {
      infof(data, "Failed to stop libssh2 sftp subsystem");
    }
    sshc->sftp_session = NULL;
  }

  curlx_safefree(sshc->homedir);

  myssh_to(data, sshc, SSH_SESSION_DISCONNECT);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_download_init(struct Curl_easy *data,
                                             struct ssh_conn *sshc,
                                             struct SSHPROTO *sshp)
{
  if(!sshp)
    return CURLE_FAILED_INIT;
  /*
   * Work on getting the specified file
   */
  sshc->sftp_handle =
    libssh2_sftp_open_ex(sshc->sftp_session, sshp->path,
                         curlx_uztoui(strlen(sshp->path)),
                         LIBSSH2_FXF_READ, (long)data->set.new_file_perms,
                         LIBSSH2_SFTP_OPENFILE);
  if(!sshc->sftp_handle) {
    unsigned long sftperr;
    if(libssh2_session_last_errno(sshc->ssh_session) ==
       LIBSSH2_ERROR_EAGAIN) {
      return CURLE_AGAIN;
    }
    sftperr = libssh2_sftp_last_error(sshc->sftp_session);
    failf(data, "Could not open remote file for reading: %s",
          sftp_libssh2_strerror(sftperr));
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    return sftp_libssh2_error_to_CURLE(sftperr);
  }
  myssh_to(data, sshc, SSH_SFTP_DOWNLOAD_STAT);
  return CURLE_OK;
}

static CURLcode ssh_state_scp_upload_init(struct Curl_easy *data,
                                          struct ssh_conn *sshc,
                                          struct SSHPROTO *sshp)
{
  if(!sshp)
    return CURLE_FAILED_INIT;
  /*
   * libssh2 requires that the destination path is a full path that
   * includes the destination file and name OR ends in a "/" . If this is
   * not done the destination file is named the same name as the last
   * directory in the path.
   */
  sshc->ssh_channel =
    libssh2_scp_send64(sshc->ssh_session, sshp->path,
                       (int)data->set.new_file_perms,
                       (libssh2_int64_t)data->state.infilesize, 0, 0);
  if(!sshc->ssh_channel) {
    int ssh_err;
    char *err_msg = NULL;
    CURLcode result;
    if(libssh2_session_last_errno(sshc->ssh_session) ==
       LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    ssh_err = libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
    failf(data, "%s", err_msg);
    myssh_to(data, sshc, SSH_SCP_CHANNEL_FREE);
    result = libssh2_session_error_to_CURLE(ssh_err);

    /* Map generic errors to upload failed */
    if(result == CURLE_SSH ||
       result == CURLE_REMOTE_FILE_NOT_FOUND)
      result = CURLE_UPLOAD_FAILED;
    return result;
  }

  /* upload data */
  data->req.size = data->state.infilesize;
  Curl_pgrsSetUploadSize(data, data->state.infilesize);
  Curl_xfer_setup_send(data, FIRSTSOCKET);

  /* not set by Curl_xfer_setup to preserve io_flags */
  data->conn->recv_idx = FIRSTSOCKET;

  myssh_to(data, sshc, SSH_STOP);

  return CURLE_OK;
}

static CURLcode ssh_state_session_disconnect(struct Curl_easy *data,
                                             struct ssh_conn *sshc)
{
  /* during weird times when we have been prematurely aborted, the channel
     is still alive when we reach this state and we MUST kill the channel
     properly first */
  int rc = 0;
  if(sshc->ssh_channel) {
    rc = libssh2_channel_free(sshc->ssh_channel);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    if(rc < 0) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to free libssh2 scp subsystem: %d %s", rc, err_msg);
    }
    sshc->ssh_channel = NULL;
  }

  if(sshc->ssh_session) {
    rc = libssh2_session_disconnect(sshc->ssh_session, "Shutdown");
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;

    if(rc < 0) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to disconnect libssh2 session: %d %s", rc, err_msg);
    }
  }

  curlx_safefree(sshc->homedir);

  myssh_to(data, sshc, SSH_SESSION_FREE);
  return CURLE_OK;
}

static CURLcode sshc_cleanup(struct ssh_conn *sshc, struct Curl_easy *data,
                             bool block)
{
  int rc;

  if(sshc->kh) {
    libssh2_knownhost_free(sshc->kh);
    sshc->kh = NULL;
  }

  if(sshc->ssh_agent) {
    rc = libssh2_agent_disconnect(sshc->ssh_agent);
    if((rc < 0) && data) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to disconnect from libssh2 agent: %d %s",
            rc, err_msg);
    }
    if(!block && (rc == LIBSSH2_ERROR_EAGAIN))
      return CURLE_AGAIN;

    libssh2_agent_free(sshc->ssh_agent);
    sshc->ssh_agent = NULL;

    /* NB: there is no need to free identities, they are part of internal
       agent stuff */
    sshc->sshagent_identity = NULL;
    sshc->sshagent_prev_identity = NULL;
  }

  if(sshc->sftp_handle) {
    rc = libssh2_sftp_close(sshc->sftp_handle);
    if((rc < 0) && data) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to close libssh2 file: %d %s", rc, err_msg);
    }
    if(!block && (rc == LIBSSH2_ERROR_EAGAIN))
      return CURLE_AGAIN;

    sshc->sftp_handle = NULL;
  }

  if(sshc->ssh_channel) {
    rc = libssh2_channel_free(sshc->ssh_channel);
    if((rc < 0) && data) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to free libssh2 scp subsystem: %d %s", rc, err_msg);
    }
    if(!block && (rc == LIBSSH2_ERROR_EAGAIN))
      return CURLE_AGAIN;

    sshc->ssh_channel = NULL;
  }

  if(sshc->sftp_session) {
    rc = libssh2_sftp_shutdown(sshc->sftp_session);
    if((rc < 0) && data) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to stop libssh2 sftp subsystem: %d %s", rc, err_msg);
    }
    if(!block && (rc == LIBSSH2_ERROR_EAGAIN))
      return CURLE_AGAIN;

    sshc->sftp_session = NULL;
  }

  if(sshc->ssh_session) {
    rc = libssh2_session_free(sshc->ssh_session);
    if((rc < 0) && data) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session, &err_msg, NULL, 0);
      infof(data, "Failed to free libssh2 session: %d %s", rc, err_msg);
    }
    if(!block && (rc == LIBSSH2_ERROR_EAGAIN))
      return CURLE_AGAIN;

    sshc->ssh_session = NULL;
  }

  /* worst-case scenario cleanup */
  DEBUGASSERT(sshc->ssh_session == NULL);
  DEBUGASSERT(sshc->ssh_channel == NULL);
  DEBUGASSERT(sshc->sftp_session == NULL);
  DEBUGASSERT(sshc->sftp_handle == NULL);
  DEBUGASSERT(sshc->kh == NULL);
  DEBUGASSERT(sshc->ssh_agent == NULL);

  curlx_safefree(sshc->rsa_pub);
  curlx_safefree(sshc->rsa);
  curlx_safefree(sshc->quote_path1);
  curlx_safefree(sshc->quote_path2);
  curlx_safefree(sshc->homedir);

  return CURLE_OK;
}

static CURLcode ssh_state_sftp_getinfo(struct Curl_easy *data,
                                       struct ssh_conn *sshc)
{
  if(data->set.get_filetime)
    myssh_to(data, sshc, SSH_SFTP_FILETIME);
  else
    myssh_to(data, sshc, SSH_SFTP_TRANS_INIT);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_filetime(struct Curl_easy *data,
                                        struct ssh_conn *sshc,
                                        struct SSHPROTO *sshp)
{
  LIBSSH2_SFTP_ATTRIBUTES attrs;
  int rc;

  if(!sshp)
    return CURLE_FAILED_INIT;

  rc = libssh2_sftp_stat_ex(sshc->sftp_session, sshp->path,
                            curlx_uztoui(strlen(sshp->path)),
                            LIBSSH2_SFTP_STAT, &attrs);
  if(rc == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  if(rc == 0)
    data->info.filetime = (time_t)attrs.mtime;

  myssh_to(data, sshc, SSH_SFTP_TRANS_INIT);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_trans_init(struct Curl_easy *data,
                                          struct ssh_conn *sshc,
                                          struct SSHPROTO *sshp)
{
  if(data->state.upload)
    myssh_to(data, sshc, SSH_SFTP_UPLOAD_INIT);
  else if(sshp) {
    size_t plen = strlen(sshp->path);
    if(plen && (sshp->path[plen - 1] == '/'))
      myssh_to(data, sshc, SSH_SFTP_READDIR_INIT);
    else
      myssh_to(data, sshc, SSH_SFTP_DOWNLOAD_INIT);
  }
  else
    return CURLE_FAILED_INIT;
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_upload_init(struct Curl_easy *data,
                                           struct ssh_conn *sshc,
                                           struct SSHPROTO *sshp,
                                           bool *block)
{
  CURLcode result;
  if(!sshp)
    return CURLE_FAILED_INIT;
  result = sftp_upload_init(data, sshc, sshp, block);
  if(result) {
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
  }
  return result;
}

static CURLcode ssh_state_sftp_create_dirs_init(struct Curl_easy *data,
                                                struct ssh_conn *sshc,
                                                struct SSHPROTO *sshp)
{
  if(!sshp)
    return CURLE_FAILED_INIT;
  if(strlen(sshp->path) > 1) {
    sshc->slash_pos = sshp->path + 1; /* ignore the leading '/' */
    myssh_to(data, sshc, SSH_SFTP_CREATE_DIRS);
  }
  else
    myssh_to(data, sshc, SSH_SFTP_UPLOAD_INIT);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_create_dirs(struct Curl_easy *data,
                                           struct ssh_conn *sshc,
                                           struct SSHPROTO *sshp)
{
  if(!sshp)
    return CURLE_FAILED_INIT;
  sshc->slash_pos = strchr(sshc->slash_pos, '/');
  if(sshc->slash_pos) {
    *sshc->slash_pos = 0;
    infof(data, "Creating directory '%s'", sshp->path);
    myssh_to(data, sshc, SSH_SFTP_CREATE_DIRS_MKDIR);
    return CURLE_OK;
  }
  myssh_to(data, sshc, SSH_SFTP_UPLOAD_INIT);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_readdir(struct Curl_easy *data,
                                       struct ssh_conn *sshc,
                                       struct SSHPROTO *sshp,
                                       bool *block)
{
  CURLcode result;
  if(!sshp)
    return CURLE_FAILED_INIT;
  result = sftp_readdir(data, sshc, sshp, block);
  if(result)
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
  return result;
}

static CURLcode ssh_state_sftp_readdir_bottom(struct Curl_easy *data,
                                              struct ssh_conn *sshc,
                                              struct SSHPROTO *sshp)
{
  CURLcode result;
  if(!sshp)
    return CURLE_FAILED_INIT;

  result = curlx_dyn_addn(&sshp->readdir, "\n", 1);
  if(!result)
    result = Curl_client_write(data, CLIENTWRITE_BODY,
                               curlx_dyn_ptr(&sshp->readdir),
                               curlx_dyn_len(&sshp->readdir));
  if(result) {
    curlx_dyn_free(&sshp->readdir);
    myssh_to(data, sshc, SSH_STOP);
  }
  else {
    curlx_dyn_reset(&sshp->readdir);
    myssh_to(data, sshc, SSH_SFTP_READDIR);
  }
  return result;
}

static CURLcode ssh_state_sftp_readdir_done(struct Curl_easy *data,
                                            struct ssh_conn *sshc)
{
  if(libssh2_sftp_closedir(sshc->sftp_handle) ==
     LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;

  sshc->sftp_handle = NULL;

  /* no data to transfer */
  Curl_xfer_setup_nop(data);
  myssh_to(data, sshc, SSH_STOP);
  return CURLE_OK;
}

static CURLcode ssh_state_sftp_download_stat(struct Curl_easy *data,
                                             struct ssh_conn *sshc,
                                             struct SSHPROTO *sshp,
                                             bool *block)
{
  CURLcode result;
  if(!sshp)
    return CURLE_FAILED_INIT;
  result = sftp_download_stat(data, sshc, sshp, block);
  if(result) {
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
    sshc->nextstate = SSH_NO_STATE;
  }
  return result;
}

static CURLcode ssh_state_scp_trans_init(struct Curl_easy *data,
                                         struct ssh_conn *sshc,
                                         struct SSHPROTO *sshp)
{
  CURLcode result;
  if(!sshp)
    return CURLE_FAILED_INIT;
  result = Curl_getworkingpath(data, sshc->homedir,
                               &sshp->path);
  if(result) {
    myssh_to(data, sshc, SSH_STOP);
    return result;
  }

  if(data->state.upload) {
    if(data->state.infilesize < 0) {
      failf(data, "SCP requires a known file size for upload");
      myssh_to(data, sshc, SSH_SCP_CHANNEL_FREE);
      return CURLE_UPLOAD_FAILED;
    }
    myssh_to(data, sshc, SSH_SCP_UPLOAD_INIT);
  }
  else
    myssh_to(data, sshc, SSH_SCP_DOWNLOAD_INIT);
  return CURLE_OK;
}

static CURLcode ssh_state_scp_done(struct Curl_easy *data,
                                   struct ssh_conn *sshc)
{
  if(data->state.upload)
    myssh_to(data, sshc, SSH_SCP_SEND_EOF);
  else
    myssh_to(data, sshc, SSH_SCP_CHANNEL_FREE);
  return CURLE_OK;
}

static CURLcode ssh_state_scp_send_eof(struct Curl_easy *data,
                                       struct ssh_conn *sshc)
{
  if(sshc->ssh_channel) {
    int rc = libssh2_channel_send_eof(sshc->ssh_channel);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;
    if(rc) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session,
                                       &err_msg, NULL, 0);
      infof(data,
            "Failed to send libssh2 channel EOF: %d %s",
            rc, err_msg);
    }
  }
  myssh_to(data, sshc, SSH_SCP_WAIT_EOF);
  return CURLE_OK;
}

static CURLcode ssh_state_scp_wait_eof(struct Curl_easy *data,
                                       struct ssh_conn *sshc)
{
  if(sshc->ssh_channel) {
    int rc = libssh2_channel_wait_eof(sshc->ssh_channel);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;
    if(rc) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session,
                                       &err_msg, NULL, 0);
      infof(data, "Failed to get channel EOF: %d %s",
            rc, err_msg);
    }
  }
  myssh_to(data, sshc, SSH_SCP_WAIT_CLOSE);
  return CURLE_OK;
}

static CURLcode ssh_state_scp_wait_close(struct Curl_easy *data,
                                         struct ssh_conn *sshc)
{
  if(sshc->ssh_channel) {
    int rc =
      libssh2_channel_wait_closed(sshc->ssh_channel);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;
    if(rc) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session,
                                       &err_msg, NULL, 0);
      infof(data, "Channel failed to close: %d %s",
            rc, err_msg);
    }
  }
  myssh_to(data, sshc, SSH_SCP_CHANNEL_FREE);
  return CURLE_OK;
}

static CURLcode ssh_state_scp_channel_free(
  struct Curl_easy *data,
  struct ssh_conn *sshc)
{
  if(sshc->ssh_channel) {
    int rc = libssh2_channel_free(sshc->ssh_channel);
    if(rc == LIBSSH2_ERROR_EAGAIN)
      return CURLE_AGAIN;
    if(rc < 0) {
      char *err_msg = NULL;
      (void)libssh2_session_last_error(sshc->ssh_session,
                                       &err_msg, NULL, 0);
      infof(data,
            "Failed to free libssh2 scp subsystem: %d %s",
            rc, err_msg);
    }
    sshc->ssh_channel = NULL;
  }
  CURL_TRC_SSH(data, "SCP DONE phase complete");
  myssh_to(data, sshc, SSH_STOP);
  return CURLE_OK;
}

static CURLcode ssh_state_session_free(struct Curl_easy *data,
                                       struct ssh_conn *sshc)
{
  CURLcode result = sshc_cleanup(sshc, data, FALSE);
  struct connectdata *conn = data->conn;
  if(result)
    return result;
  memset(sshc, 0, sizeof(struct ssh_conn));
  connclose(conn, "SSH session free");
  sshc->state = SSH_SESSION_FREE; /* current */
  myssh_to(data, sshc, SSH_STOP);
  return CURLE_OK;
}

/*
 * ssh_statemachine() runs the SSH state machine as far as it can without
 * blocking and without reaching the end. The data the pointer 'block' points
 * to is set to TRUE if the libssh2 function returns LIBSSH2_ERROR_EAGAIN
 * meaning it wants to be called again when the socket is ready
 */
static CURLcode ssh_statemachine(struct Curl_easy *data,
                                 struct ssh_conn *sshc,
                                 struct SSHPROTO *sshp,
                                 bool *block)
{
  CURLcode result = CURLE_OK;
  *block = 0; /* we are not blocking by default */

  do {
    switch(sshc->state) {
    case SSH_INIT:
      result = ssh_state_init(data, sshc);
      if(result)
        break;
      FALLTHROUGH();

    case SSH_S_STARTUP:
      result = ssh_state_startup(data, sshc);
      if(result)
        break;
      FALLTHROUGH();

    case SSH_HOSTKEY:
      result = ssh_state_hostkey(data, sshc);
      break;

    case SSH_AUTHLIST:
      result = ssh_state_authlist(data, sshc);
      break;

    case SSH_AUTH_PKEY_INIT:
      result = ssh_state_pkey_init(data, sshc);
      break;

    case SSH_AUTH_PKEY:
      result = ssh_state_auth_pkey(data, sshc);
      break;

    case SSH_AUTH_PASS_INIT:
      result = ssh_state_auth_pass_init(data, sshc);
      break;

    case SSH_AUTH_PASS:
      result = ssh_state_auth_pass(data, sshc);
      break;

    case SSH_AUTH_HOST_INIT:
      result = ssh_state_auth_host_init(data, sshc);
      break;

    case SSH_AUTH_HOST:
      myssh_to(data, sshc, SSH_AUTH_AGENT_INIT);
      break;

    case SSH_AUTH_AGENT_INIT:
      result = ssh_state_auth_agent_init(data, sshc);
      break;

    case SSH_AUTH_AGENT_LIST:
      result = ssh_state_auth_agent_list(data, sshc);
      break;

    case SSH_AUTH_AGENT:
      result = ssh_state_auth_agent(data, sshc);
      break;

    case SSH_AUTH_KEY_INIT:
      result = ssh_state_auth_key_init(data, sshc);
      break;

    case SSH_AUTH_KEY:
      result = ssh_state_auth_key(data, sshc);
      break;

    case SSH_AUTH_DONE:
      result = ssh_state_auth_done(data, sshc);
      break;

    case SSH_SFTP_INIT:
      result = ssh_state_sftp_init(data, sshc);
      break;

    case SSH_SFTP_REALPATH:
      result = ssh_state_sftp_realpath(data, sshc, sshp);
      break;

    case SSH_SFTP_QUOTE_INIT:
      result = ssh_state_sftp_quote_init(data, sshc, sshp);
      break;

    case SSH_SFTP_POSTQUOTE_INIT:
      result = ssh_state_sftp_postquote_init(data, sshc);
      break;

    case SSH_SFTP_QUOTE:
      result = ssh_state_sftp_quote(data, sshc, sshp);
      break;

    case SSH_SFTP_NEXT_QUOTE:
      result = ssh_state_sftp_next_quote(data, sshc);
      break;

    case SSH_SFTP_QUOTE_STAT:
      result = ssh_state_sftp_quote_stat(data, sshc, sshp, block);
      break;

    case SSH_SFTP_QUOTE_SETSTAT:
      result = ssh_state_sftp_quote_setstat(data, sshc, sshp);
      break;

    case SSH_SFTP_QUOTE_SYMLINK:
      result = ssh_state_sftp_quote_symlink(data, sshc);
      break;

    case SSH_SFTP_QUOTE_MKDIR:
      result = ssh_state_sftp_quote_mkdir(data, sshc);
      break;

    case SSH_SFTP_QUOTE_RENAME:
      result = ssh_state_sftp_quote_rename(data, sshc);
      break;

    case SSH_SFTP_QUOTE_RMDIR:
      result = ssh_state_sftp_quote_rmdir(data, sshc);
      break;

    case SSH_SFTP_QUOTE_UNLINK:
      result = ssh_state_sftp_quote_unlink(data, sshc);
      break;

    case SSH_SFTP_QUOTE_STATVFS:
      result = ssh_state_sftp_quote_statvfs(data, sshc);
      break;

    case SSH_SFTP_GETINFO:
      result = ssh_state_sftp_getinfo(data, sshc);
      break;

    case SSH_SFTP_FILETIME:
      result = ssh_state_sftp_filetime(data, sshc, sshp);
      break;

    case SSH_SFTP_TRANS_INIT:
      result = ssh_state_sftp_trans_init(data, sshc, sshp);
      break;

    case SSH_SFTP_UPLOAD_INIT:
      result = ssh_state_sftp_upload_init(data, sshc, sshp, block);
      break;

    case SSH_SFTP_CREATE_DIRS_INIT:
      result = ssh_state_sftp_create_dirs_init(data, sshc, sshp);
      break;

    case SSH_SFTP_CREATE_DIRS:
      result = ssh_state_sftp_create_dirs(data, sshc, sshp);
      break;

    case SSH_SFTP_CREATE_DIRS_MKDIR:
      result = ssh_state_sftp_create_dirs_mkdir(data, sshc, sshp);
      break;

    case SSH_SFTP_READDIR_INIT:
      result = ssh_state_sftp_readdir_init(data, sshc, sshp);
      break;

    case SSH_SFTP_READDIR:
      result = ssh_state_sftp_readdir(data, sshc, sshp, block);
      break;

    case SSH_SFTP_READDIR_LINK:
      result = ssh_state_sftp_readdir_link(data, sshc, sshp);
      break;

    case SSH_SFTP_READDIR_BOTTOM:
      result = ssh_state_sftp_readdir_bottom(data, sshc, sshp);
      break;

    case SSH_SFTP_READDIR_DONE:
      result = ssh_state_sftp_readdir_done(data, sshc);
      break;

    case SSH_SFTP_DOWNLOAD_INIT:
      result = ssh_state_sftp_download_init(data, sshc, sshp);
      break;

    case SSH_SFTP_DOWNLOAD_STAT:
      result = ssh_state_sftp_download_stat(data, sshc, sshp, block);
      break;

    case SSH_SFTP_CLOSE:
      result = ssh_state_sftp_close(data, sshc, sshp);
      break;

    case SSH_SFTP_SHUTDOWN:
      result = ssh_state_sftp_shutdown(data, sshc);
      break;

    case SSH_SCP_TRANS_INIT:
      result = ssh_state_scp_trans_init(data, sshc, sshp);
      break;

    case SSH_SCP_UPLOAD_INIT:
      result = ssh_state_scp_upload_init(data, sshc, sshp);
      break;

    case SSH_SCP_DOWNLOAD_INIT:
      result = ssh_state_scp_download_init(data, sshc, sshp);
      break;

    case SSH_SCP_DONE:
      result = ssh_state_scp_done(data, sshc);
      break;

    case SSH_SCP_SEND_EOF:
      result = ssh_state_scp_send_eof(data, sshc);
      break;

    case SSH_SCP_WAIT_EOF:
      result = ssh_state_scp_wait_eof(data, sshc);
      break;

    case SSH_SCP_WAIT_CLOSE:
      result = ssh_state_scp_wait_close(data, sshc);
      break;

    case SSH_SCP_CHANNEL_FREE:
      result = ssh_state_scp_channel_free(data, sshc);
      break;

    case SSH_SESSION_DISCONNECT:
      result = ssh_state_session_disconnect(data, sshc);
      break;

    case SSH_SESSION_FREE:
      result = ssh_state_session_free(data, sshc);
      break;

    case SSH_QUIT:
    default:
      /* internal error */
      myssh_to(data, sshc, SSH_STOP);
      break;
    }

  } while(!result && (sshc->state != SSH_STOP) && !*block);

  if(result == CURLE_AGAIN) {
    /* we would block, we need to wait for the socket to be ready (in the
       right direction too)! */
    *block = TRUE;
    result = CURLE_OK;
  }
  CURL_TRC_SSH(data, "[%s] statemachine() -> %d, block=%d",
               Curl_ssh_statename(sshc->state), result, *block);

  return result;
}

/* called by the multi interface to figure out what socket(s) to wait for and
   for what actions in the DO_DONE, PERFORM and WAITPERFORM states */
static CURLcode ssh_pollset(struct Curl_easy *data,
                            struct easy_pollset *ps)
{
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  curl_socket_t sock = conn->sock[FIRSTSOCKET];
  int waitfor;

  if(!sshc || (sock == CURL_SOCKET_BAD))
    return CURLE_FAILED_INIT;

  waitfor = sshc->waitfor ? sshc->waitfor : data->req.io_flags;
  if(waitfor) {
    int flags = 0;
    if(waitfor & REQ_IO_RECV)
      flags |= CURL_POLL_IN;
    if(waitfor & REQ_IO_SEND)
      flags |= CURL_POLL_OUT;
    DEBUGASSERT(flags);
    CURL_TRC_SSH(data, "pollset, flags=%x", flags);
    return Curl_pollset_change(data, ps, sock, flags, 0);
  }
  /* While we still have a session, we listen incoming data. */
  if(sshc->ssh_session)
    return Curl_pollset_change(data, ps, sock, CURL_POLL_IN, 0);
  return CURLE_OK;
}

/*
 * When one of the libssh2 functions has returned LIBSSH2_ERROR_EAGAIN this
 * function is used to figure out in what direction and stores this info so
 * that the multi interface can take advantage of it. Make sure to call this
 * function in all cases so that when it _does not_ return EAGAIN we can
 * restore the default wait bits.
 */
static void ssh_block2waitfor(struct Curl_easy *data,
                              struct ssh_conn *sshc,
                              bool block)
{
  int dir = 0;
  (void)data;
  if(block) {
    dir = libssh2_session_block_directions(sshc->ssh_session);
    if(dir) {
      /* translate the libssh2 define bits into our own bit defines */
      sshc->waitfor =
        ((dir & LIBSSH2_SESSION_BLOCK_INBOUND) ? REQ_IO_RECV : 0) |
        ((dir & LIBSSH2_SESSION_BLOCK_OUTBOUND) ? REQ_IO_SEND : 0);
    }
  }
  if(!dir)
    sshc->waitfor = 0;
}

/* called repeatedly until done from multi.c */
static CURLcode ssh_multi_statemach(struct Curl_easy *data, bool *done)
{
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  struct SSHPROTO *sshp = Curl_meta_get(data, CURL_META_SSH_EASY);
  CURLcode result = CURLE_OK;
  bool block; /* we store the status and use that to provide a ssh_pollset()
                 implementation */
  if(!sshc || !sshp)
    return CURLE_FAILED_INIT;

  do {
    result = ssh_statemachine(data, sshc, sshp, &block);
    *done = (sshc->state == SSH_STOP);
    /* if there is no error, it is not done and it did not EWOULDBLOCK, then
       try again */
  } while(!result && !*done && !block);
  ssh_block2waitfor(data, sshc, block);

  return result;
}

static CURLcode ssh_block_statemach(struct Curl_easy *data,
                                    struct ssh_conn *sshc,
                                    struct SSHPROTO *sshp,
                                    bool disconnect)
{
  CURLcode result = CURLE_OK;
  struct curltime start = *Curl_pgrs_now(data);

  while((sshc->state != SSH_STOP) && !result) {
    bool block;
    timediff_t left_ms = 1000;

    result = ssh_statemachine(data, sshc, sshp, &block);
    if(result)
      break;

    if(!disconnect) {
      result = Curl_pgrsCheck(data);
      if(result)
        break;

      left_ms = Curl_timeleft_ms(data);
      if(left_ms < 0) {
        failf(data, "Operation timed out");
        return CURLE_OPERATION_TIMEDOUT;
      }
    }
    else if(curlx_ptimediff_ms(Curl_pgrs_now(data), &start) > 1000) {
      /* disconnect timeout */
      failf(data, "Disconnect timed out");
      result = CURLE_OK;
      break;
    }

    if(block) {
      int dir = libssh2_session_block_directions(sshc->ssh_session);
      curl_socket_t sock = data->conn->sock[FIRSTSOCKET];
      curl_socket_t fd_read = CURL_SOCKET_BAD;
      curl_socket_t fd_write = CURL_SOCKET_BAD;
      if(LIBSSH2_SESSION_BLOCK_INBOUND & dir)
        fd_read = sock;
      if(LIBSSH2_SESSION_BLOCK_OUTBOUND & dir)
        fd_write = sock;
      /* wait for the socket to become ready */
      (void)Curl_socket_check(fd_read, CURL_SOCKET_BAD, fd_write,
                              left_ms > 1000 ? 1000 : left_ms);
    }
  }

  return result;
}

static void myssh_easy_dtor(void *key, size_t klen, void *entry)
{
  struct SSHPROTO *sshp = entry;
  (void)key;
  (void)klen;
  curlx_safefree(sshp->path);
  curlx_dyn_free(&sshp->readdir);
  curlx_dyn_free(&sshp->readdir_link);
  curlx_free(sshp);
}

static void myssh_conn_dtor(void *key, size_t klen, void *entry)
{
  struct ssh_conn *sshc = entry;
  (void)key;
  (void)klen;
  sshc_cleanup(sshc, NULL, TRUE);
  curlx_free(sshc);
}

/*
 * SSH setup and connection
 */
static CURLcode ssh_setup_connection(struct Curl_easy *data,
                                     struct connectdata *conn)
{
  struct ssh_conn *sshc;
  struct SSHPROTO *sshp;
  (void)conn;

  sshc = curlx_calloc(1, sizeof(*sshc));
  if(!sshc)
    return CURLE_OUT_OF_MEMORY;

  if(Curl_conn_meta_set(conn, CURL_META_SSH_CONN, sshc, myssh_conn_dtor))
    return CURLE_OUT_OF_MEMORY;

  sshp = curlx_calloc(1, sizeof(*sshp));
  if(!sshp)
    return CURLE_OUT_OF_MEMORY;

  curlx_dyn_init(&sshp->readdir, CURL_PATH_MAX * 2);
  curlx_dyn_init(&sshp->readdir_link, CURL_PATH_MAX);
  if(Curl_meta_set(data, CURL_META_SSH_EASY, sshp, myssh_easy_dtor))
    return CURLE_OUT_OF_MEMORY;

  return CURLE_OK;
}

static Curl_recv scp_recv, sftp_recv;
static Curl_send scp_send, sftp_send;

#ifndef CURL_DISABLE_PROXY
static ssize_t ssh_tls_recv(libssh2_socket_t sock, void *buffer,
                            size_t length, int flags, void **abstract)
{
  struct Curl_easy *data = (struct Curl_easy *)*abstract;
  int sockindex = Curl_conn_sockindex(data, sock);
  size_t nread;
  CURLcode result;
  struct connectdata *conn = data->conn;
  Curl_recv *backup = conn->recv[sockindex];
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  (void)flags;

  if(!sshc)
    return -1;

  /* swap in the TLS reader function for this call only, and then swap back
     the SSH one again */
  conn->recv[sockindex] = sshc->tls_recv;
  result = Curl_conn_recv(data, sockindex, buffer, length, &nread);
  conn->recv[sockindex] = backup;
  if(result == CURLE_AGAIN)
    return -EAGAIN; /* magic return code for libssh2 */
  else if(result)
    return -1; /* generic error */
  Curl_debug(data, CURLINFO_DATA_IN, (const char *)buffer, nread);
  return (ssize_t)nread;
}

static ssize_t ssh_tls_send(libssh2_socket_t sock, const void *buffer,
                            size_t length, int flags, void **abstract)
{
  struct Curl_easy *data = (struct Curl_easy *)*abstract;
  int sockindex = Curl_conn_sockindex(data, sock);
  size_t nwrite;
  CURLcode result;
  struct connectdata *conn = data->conn;
  Curl_send *backup = conn->send[sockindex];
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  (void)flags;

  if(!sshc)
    return -1;

  /* swap in the TLS writer function for this call only, and then swap back
     the SSH one again */
  conn->send[sockindex] = sshc->tls_send;
  result = Curl_conn_send(data, sockindex, buffer, length, FALSE, &nwrite);
  conn->send[sockindex] = backup;
  if(result == CURLE_AGAIN)
    return -EAGAIN; /* magic return code for libssh2 */
  else if(result)
    return -1; /* error */
  Curl_debug(data, CURLINFO_DATA_OUT, (const char *)buffer, nwrite);
  return (ssize_t)nwrite;
}
#endif

/*
 * Curl_ssh_connect() gets called from Curl_protocol_connect() to allow us to
 * do protocol-specific actions at connect-time.
 */
static CURLcode ssh_connect(struct Curl_easy *data, bool *done)
{
#ifdef CURL_LIBSSH2_DEBUG
  curl_socket_t sock;
#endif
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  CURLcode result;

#if LIBSSH2_VERSION_NUM >= 0x010b00
  {
    const char *crypto_str;
    switch(libssh2_crypto_engine()) {
    case libssh2_gcrypt:
      crypto_str = "libgcrypt";
      break;
    case libssh2_mbedtls:
      crypto_str = "mbedTLS";
      break;
    case libssh2_openssl:
      crypto_str = "openssl compatible";
      break;
    case libssh2_os400qc3:
      crypto_str = "OS400QC3";
      break;
    case libssh2_wincng:
      crypto_str = "WinCNG";
      break;
    default:
      crypto_str = NULL;
      break;
    }
    if(crypto_str)
      infof(data, "libssh2 cryptography backend: %s", crypto_str);
  }
#endif

  if(!sshc)
    return CURLE_FAILED_INIT;

  infof(data, "User: '%s'", conn->user);
#ifdef CURL_LIBSSH2_DEBUG
  infof(data, "Password: %s", conn->passwd);
  sock = conn->sock[FIRSTSOCKET];
#endif /* CURL_LIBSSH2_DEBUG */

  /* libcurl MUST to set custom memory functions so that the kbd_callback
     function's memory allocations can be properly freed */
  sshc->ssh_session = libssh2_session_init_ex(my_libssh2_malloc,
                                              my_libssh2_free,
                                              my_libssh2_realloc, data);

  if(!sshc->ssh_session) {
    failf(data, "Failure initialising ssh session");
    return CURLE_FAILED_INIT;
  }

  /* Set the packet read timeout if the libssh2 version supports it */
#if LIBSSH2_VERSION_NUM >= 0x010B00
  if(data->set.server_response_timeout > 0) {
    libssh2_session_set_read_timeout(sshc->ssh_session,
                             (long)(data->set.server_response_timeout / 1000));
  }
#endif

#ifndef CURL_DISABLE_PROXY
  if(conn->http_proxy.proxytype == CURLPROXY_HTTPS) {
    /*
      Setup libssh2 callbacks to make it read/write TLS from the socket.

      ssize_t
      recvcb(libssh2_socket_t sock, void *buffer, size_t length,
      int flags, void **abstract);

      ssize_t
      sendcb(libssh2_socket_t sock, const void *buffer, size_t length,
      int flags, void **abstract);

    */
#if LIBSSH2_VERSION_NUM >= 0x010b01
    infof(data, "Uses HTTPS proxy");
#if defined(__clang__) && __clang_major__ >= 16
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcast-function-type-strict"
#endif
    libssh2_session_callback_set2(sshc->ssh_session,
                                  LIBSSH2_CALLBACK_RECV,
                                  (libssh2_cb_generic *)ssh_tls_recv);
    libssh2_session_callback_set2(sshc->ssh_session,
                                  LIBSSH2_CALLBACK_SEND,
                                  (libssh2_cb_generic *)ssh_tls_send);
#if defined(__clang__) && __clang_major__ >= 16
#pragma clang diagnostic pop
#endif
#else
    /*
     * This crazy union dance is here to avoid assigning a void pointer a
     * function pointer as it is invalid C. The problem is of course that
     * libssh2 has such an API...
     */
    union receive {
      void *recvp;
      ssize_t (*recvptr)(libssh2_socket_t, void *, size_t, int, void **);
    };
    union transfer {
      void *sendp;
      ssize_t (*sendptr)(libssh2_socket_t, const void *, size_t, int, void **);
    };
    union receive sshrecv;
    union transfer sshsend;

    sshrecv.recvptr = ssh_tls_recv;
    sshsend.sendptr = ssh_tls_send;

    infof(data, "Uses HTTPS proxy");
    libssh2_session_callback_set(sshc->ssh_session,
                                 LIBSSH2_CALLBACK_RECV, sshrecv.recvp);
    libssh2_session_callback_set(sshc->ssh_session,
                                 LIBSSH2_CALLBACK_SEND, sshsend.sendp);
#endif

    /* Store the underlying TLS recv/send function pointers to be used when
       reading from the proxy */
    sshc->tls_recv = conn->recv[FIRSTSOCKET];
    sshc->tls_send = conn->send[FIRSTSOCKET];
  }

#endif /* CURL_DISABLE_PROXY */
  if(conn->scheme->protocol & CURLPROTO_SCP) {
    conn->recv[FIRSTSOCKET] = scp_recv;
    conn->send[FIRSTSOCKET] = scp_send;
  }
  else {
    conn->recv[FIRSTSOCKET] = sftp_recv;
    conn->send[FIRSTSOCKET] = sftp_send;
  }

  if(data->set.ssh_compression &&
     libssh2_session_flag(sshc->ssh_session, LIBSSH2_FLAG_COMPRESS, 1) < 0) {
    infof(data, "Failed to enable compression for ssh session");
  }

  if(data->set.str[STRING_SSH_KNOWNHOSTS]) {
    int rc;
    sshc->kh = libssh2_knownhost_init(sshc->ssh_session);
    if(!sshc->kh) {
      libssh2_session_free(sshc->ssh_session);
      sshc->ssh_session = NULL;
      return CURLE_FAILED_INIT;
    }

    /* read all known hosts from there */
    rc = libssh2_knownhost_readfile(sshc->kh,
                                    data->set.str[STRING_SSH_KNOWNHOSTS],
                                    LIBSSH2_KNOWNHOST_FILE_OPENSSH);
    if(rc < 0)
      infof(data, "Failed to read known hosts from %s",
            data->set.str[STRING_SSH_KNOWNHOSTS]);
  }

#ifdef CURL_LIBSSH2_DEBUG
  libssh2_trace(sshc->ssh_session, ~0);
  infof(data, "SSH socket: %d", (int)sock);
#endif /* CURL_LIBSSH2_DEBUG */

  myssh_to(data, sshc, SSH_INIT);

  result = ssh_multi_statemach(data, done);

  return result;
}

/*
 ***********************************************************************
 *
 * scp_perform()
 *
 * This is the actual DO function for SCP. Get a file according to
 * the options previously setup.
 */

static CURLcode scp_perform(struct Curl_easy *data,
                            bool *connected,
                            bool *dophase_done)
{
  struct ssh_conn *sshc = Curl_conn_meta_get(data->conn, CURL_META_SSH_CONN);
  CURLcode result = CURLE_OK;

  CURL_TRC_SSH(data, "DO phase starts");

  *dophase_done = FALSE; /* not done yet */
  if(!sshc)
    return CURLE_FAILED_INIT;

  /* start the first command in the DO phase */
  myssh_to(data, sshc, SSH_SCP_TRANS_INIT);

  /* run the state-machine */
  result = ssh_multi_statemach(data, dophase_done);

  *connected = Curl_conn_is_connected(data->conn, FIRSTSOCKET);

  if(*dophase_done) {
    CURL_TRC_SSH(data, "DO phase is complete");
  }

  return result;
}

/* called from multi.c while DOing */
static CURLcode scp_doing(struct Curl_easy *data,
                          bool *dophase_done)
{
  CURLcode result;
  result = ssh_multi_statemach(data, dophase_done);

  if(*dophase_done) {
    CURL_TRC_SSH(data, "DO phase is complete");
  }
  return result;
}

/* BLOCKING, but the function is using the state machine so the only reason
   this is still blocking is that the multi interface code has no support for
   disconnecting operations that takes a while */
static CURLcode scp_disconnect(struct Curl_easy *data,
                               struct connectdata *conn,
                               bool dead_connection)
{
  CURLcode result = CURLE_OK;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  struct SSHPROTO *sshp = Curl_meta_get(data, CURL_META_SSH_EASY);
  (void)dead_connection;

  if(sshc && sshc->ssh_session) {
    /* only if there is a session still around to use! */
    myssh_to(data, sshc, SSH_SESSION_DISCONNECT);
    result = ssh_block_statemach(data, sshc, sshp, TRUE);
  }

  if(sshc)
    return sshc_cleanup(sshc, data, TRUE);
  return result;
}

/* generic done function for both SCP and SFTP called from their specific
   done functions */
static CURLcode ssh_done(struct Curl_easy *data, CURLcode status)
{
  struct ssh_conn *sshc = Curl_conn_meta_get(data->conn, CURL_META_SSH_CONN);
  struct SSHPROTO *sshp = Curl_meta_get(data, CURL_META_SSH_EASY);
  CURLcode result = CURLE_OK;

  if(!sshc || !sshp)
    return CURLE_FAILED_INIT;

  if(!status)
    /* run the state-machine */
    result = ssh_block_statemach(data, sshc, sshp, FALSE);
  else
    result = status;

  if(Curl_pgrsDone(data))
    return CURLE_ABORTED_BY_CALLBACK;

  CURL_REQ_CLEAR_IO(data);
  return result;
}

static CURLcode scp_done(struct Curl_easy *data, CURLcode status,
                         bool premature)
{
  struct ssh_conn *sshc = Curl_conn_meta_get(data->conn, CURL_META_SSH_CONN);
  (void)premature;

  if(sshc && !status)
    myssh_to(data, sshc, SSH_SCP_DONE);

  return ssh_done(data, status);
}

static CURLcode scp_send(struct Curl_easy *data, int sockindex,
                         const uint8_t *mem, size_t len, bool eos,
                         size_t *pnwritten)
{
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  CURLcode result = CURLE_OK;
  ssize_t nwritten;

  (void)sockindex; /* we only support SCP on the fixed known primary socket */
  (void)eos;
  *pnwritten = 0;

  if(!sshc)
    return CURLE_FAILED_INIT;

  /* libssh2_channel_write() returns int! */
  nwritten = (ssize_t)libssh2_channel_write(sshc->ssh_channel,
                                            (const char *)mem, len);

  ssh_block2waitfor(data, sshc, (nwritten == LIBSSH2_ERROR_EAGAIN));

  if(nwritten == LIBSSH2_ERROR_EAGAIN)
    result = CURLE_AGAIN;
  else if(nwritten < LIBSSH2_ERROR_NONE)
    result = libssh2_session_error_to_CURLE((int)nwritten);
  else
    *pnwritten = (size_t)nwritten;

  return result;
}

static CURLcode scp_recv(struct Curl_easy *data, int sockindex,
                         char *mem, size_t len, size_t *pnread)
{
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  CURLcode result = CURLE_OK;
  ssize_t nread;

  (void)sockindex; /* we only support SCP on the fixed known primary socket */
  *pnread = 0;

  if(!sshc)
    return CURLE_FAILED_INIT;

  /* libssh2_channel_read() returns int */
  nread = (ssize_t)libssh2_channel_read(sshc->ssh_channel, mem, len);

  ssh_block2waitfor(data, sshc, (nread == LIBSSH2_ERROR_EAGAIN));
  if(nread == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;
  else if(nread < LIBSSH2_ERROR_NONE)
    result = libssh2_session_error_to_CURLE((int)nread);
  else
    *pnread = (size_t)nread;

  return result;
}

/*
 * =============== SFTP ===============
 */

/*
 ***********************************************************************
 *
 * sftp_perform()
 *
 * This is the actual DO function for SFTP. Get a file/directory according to
 * the options previously setup.
 */

static CURLcode sftp_perform(struct Curl_easy *data,
                             bool *connected,
                             bool *dophase_done)
{
  struct ssh_conn *sshc = Curl_conn_meta_get(data->conn, CURL_META_SSH_CONN);
  CURLcode result = CURLE_OK;

  CURL_TRC_SSH(data, "DO phase starts");

  *dophase_done = FALSE; /* not done yet */
  if(!sshc)
    return CURLE_FAILED_INIT;

  /* start the first command in the DO phase */
  myssh_to(data, sshc, SSH_SFTP_QUOTE_INIT);

  /* run the state-machine */
  result = ssh_multi_statemach(data, dophase_done);

  *connected = Curl_conn_is_connected(data->conn, FIRSTSOCKET);

  if(*dophase_done) {
    CURL_TRC_SSH(data, "DO phase is complete");
  }

  return result;
}

/* called from multi.c while DOing */
static CURLcode sftp_doing(struct Curl_easy *data,
                           bool *dophase_done)
{
  CURLcode result = ssh_multi_statemach(data, dophase_done);

  if(*dophase_done) {
    CURL_TRC_SSH(data, "DO phase is complete");
  }
  return result;
}

/* BLOCKING, but the function is using the state machine so the only reason
   this is still blocking is that the multi interface code has no support for
   disconnecting operations that takes a while */
static CURLcode sftp_disconnect(struct Curl_easy *data,
                                struct connectdata *conn, bool dead_connection)
{
  CURLcode result = CURLE_OK;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  struct SSHPROTO *sshp = Curl_meta_get(data, CURL_META_SSH_EASY);
  (void)dead_connection;

  if(sshc) {
    if(sshc->ssh_session) {
      /* only if there is a session still around to use! */
      CURL_TRC_SSH(data, "DISCONNECT starts now");
      myssh_to(data, sshc, SSH_SFTP_SHUTDOWN);
      result = ssh_block_statemach(data, sshc, sshp, TRUE);
      CURL_TRC_SSH(data, "DISCONNECT is done -> %d", result);
    }
    sshc_cleanup(sshc, data, TRUE);
  }
  return result;
}

static CURLcode sftp_done(struct Curl_easy *data, CURLcode status,
                          bool premature)
{
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);

  if(!sshc)
    return CURLE_FAILED_INIT;

  if(!status) {
    /* Post quote commands are executed after the SFTP_CLOSE state to avoid
       errors that could happen due to open file handles during POSTQUOTE
       operation */
    if(!premature && data->set.postquote && !conn->bits.retry)
      sshc->nextstate = SSH_SFTP_POSTQUOTE_INIT;
    myssh_to(data, sshc, SSH_SFTP_CLOSE);
  }
  return ssh_done(data, status);
}

/* return number of sent bytes */
static CURLcode sftp_send(struct Curl_easy *data, int sockindex,
                          const uint8_t *mem, size_t len, bool eos,
                          size_t *pnwritten)
{
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  ssize_t nwrite;

  (void)sockindex;
  (void)eos;
  *pnwritten = 0;

  if(!sshc)
    return CURLE_FAILED_INIT;

  nwrite = libssh2_sftp_write(sshc->sftp_handle, (const char *)mem, len);

  ssh_block2waitfor(data, sshc, (nwrite == LIBSSH2_ERROR_EAGAIN));

  if(nwrite == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;
  else if(nwrite < LIBSSH2_ERROR_NONE)
    return libssh2_session_error_to_CURLE((int)nwrite);
  *pnwritten = (size_t)nwrite;
  return CURLE_OK;
}

/*
 * Return number of received (decrypted) bytes
 * or <0 on error
 */
static CURLcode sftp_recv(struct Curl_easy *data, int sockindex,
                          char *mem, size_t len, size_t *pnread)
{
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
  ssize_t nread;

  (void)sockindex;
  *pnread = 0;

  if(!sshc)
    return CURLE_FAILED_INIT;

  nread = libssh2_sftp_read(sshc->sftp_handle, mem, len);

  ssh_block2waitfor(data, sshc, (nread == LIBSSH2_ERROR_EAGAIN));

  if(nread == LIBSSH2_ERROR_EAGAIN)
    return CURLE_AGAIN;
  else if(nread < 0)
    return libssh2_session_error_to_CURLE((int)nread);

  *pnread = (size_t)nread;
  return CURLE_OK;
}

/*
 * The DO function is generic for both protocols. There was previously two
 * separate ones but this way means less duplicated code.
 */
static CURLcode ssh_do(struct Curl_easy *data, bool *done)
{
  CURLcode result;
  bool connected = FALSE;
  struct connectdata *conn = data->conn;
  struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);

  *done = FALSE; /* default to false */
  if(!sshc)
    return CURLE_FAILED_INIT;

  data->req.size = -1; /* make sure this is unknown at this point */
  sshc->secondCreateDirs = 0;   /* reset the create directory attempt state
                                   variable */

  Curl_pgrsReset(data);

  if(conn->scheme->protocol & CURLPROTO_SCP)
    result = scp_perform(data, &connected, done);
  else
    result = sftp_perform(data, &connected, done);

  return result;
}

CURLcode Curl_ssh_init(void)
{
  if(libssh2_init(0)) {
    DEBUGF(curl_mfprintf(stderr, "Error: libssh2_init failed\n"));
    return CURLE_FAILED_INIT;
  }
  return CURLE_OK;
}

void Curl_ssh_cleanup(void)
{
  libssh2_exit();
}

void Curl_ssh_version(char *buffer, size_t buflen)
{
  (void)curl_msnprintf(buffer, buflen, "libssh2/%s", libssh2_version(0));
}

/* The SSH session is associated with the *CONNECTION* but the callback user
 * pointer is an easy handle pointer. This function allows us to reassign the
 * user pointer to the *CURRENT* (new) easy handle.
 */
static void ssh_attach(struct Curl_easy *data, struct connectdata *conn)
{
  DEBUGASSERT(data);
  DEBUGASSERT(conn);
  if(conn->scheme->protocol & PROTO_FAMILY_SSH) {
    struct ssh_conn *sshc = Curl_conn_meta_get(conn, CURL_META_SSH_CONN);
    if(sshc && sshc->ssh_session) {
      /* only re-attach if the session already exists */
      void **abstract = libssh2_session_abstract(sshc->ssh_session);
      *abstract = data;
    }
  }
}

/*
 * SCP protocol handler.
 */
const struct Curl_protocol Curl_protocol_scp = {
  ssh_setup_connection,                 /* setup_connection */
  ssh_do,                               /* do_it */
  scp_done,                             /* done */
  ZERO_NULL,                            /* do_more */
  ssh_connect,                          /* connect_it */
  ssh_multi_statemach,                  /* connecting */
  scp_doing,                            /* doing */
  ssh_pollset,                          /* proto_pollset */
  ssh_pollset,                          /* doing_pollset */
  ZERO_NULL,                            /* domore_pollset */
  ssh_pollset,                          /* perform_pollset */
  scp_disconnect,                       /* disconnect */
  ZERO_NULL,                            /* write_resp */
  ZERO_NULL,                            /* write_resp_hd */
  ZERO_NULL,                            /* connection_is_dead */
  ssh_attach,                           /* attach */
  ZERO_NULL,                            /* follow */
};

/*
 * SFTP protocol handler.
 */
const struct Curl_protocol Curl_protocol_sftp = {
  ssh_setup_connection,                 /* setup_connection */
  ssh_do,                               /* do_it */
  sftp_done,                            /* done */
  ZERO_NULL,                            /* do_more */
  ssh_connect,                          /* connect_it */
  ssh_multi_statemach,                  /* connecting */
  sftp_doing,                           /* doing */
  ssh_pollset,                          /* proto_pollset */
  ssh_pollset,                          /* doing_pollset */
  ZERO_NULL,                            /* domore_pollset */
  ssh_pollset,                          /* perform_pollset */
  sftp_disconnect,                      /* disconnect */
  ZERO_NULL,                            /* write_resp */
  ZERO_NULL,                            /* write_resp_hd */
  ZERO_NULL,                            /* connection_is_dead */
  ssh_attach,                           /* attach */
  ZERO_NULL,                            /* follow */
};

#endif /* USE_LIBSSH2 */
