curl / libcurl / API / curl_easy_setopt / CURLOPT_SSL_CTX_DATA

CURLOPT_SSL_CTX_DATA explained

Name

CURLOPT_SSL_CTX_DATA - pointer passed to SSL context callback

Synopsis

#include <curl/curl.h>
 
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_DATA, void *pointer);

Description

Data pointer to pass to the ssl context callback set by the option CURLOPT_SSL_CTX_FUNCTION, this is the pointer you get as third parameter.

Default

NULL

Protocols

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

This option works only with the following TLS backends: BearSSL, OpenSSL, mbedTLS and wolfSSL

Example

/* OpenSSL specific */
 
#include <openssl/ssl.h>
#include <curl/curl.h>
#include <stdio.h>
 
static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
{
  X509_STORE *store;
  X509 *cert = NULL;
  BIO *bio;
  char *mypem = parm;
  /* get a BIO */
  bio = BIO_new_mem_buf(mypem, -1);
  /* use it to read the PEM formatted certificate from memory into an
   * X509 structure that SSL can use
   */
  PEM_read_bio_X509(bio, &cert, 0, NULL);
  if(!cert)
    printf("PEM_read_bio_X509 failed...\n");
 
  /* get a pointer to the X509 certificate store (which may be empty) */
  store = SSL_CTX_get_cert_store((SSL_CTX *)sslctx);
 
  /* add our certificate to this store */
  if(X509_STORE_add_cert(store, cert) == 0)
    printf("error adding certificate\n");
 
  /* decrease reference counts */
  X509_free(cert);
  BIO_free(bio);
 
  /* all set to go */
  return CURLE_OK;
}
 
int main(void)
{
  CURL *ch;
  CURLcode rv;
  char *mypem = /* example CA cert PEM - shortened */
    "-----BEGIN CERTIFICATE-----\n"
    "MIIHPTCCBSWgAwIBAgIBADANBgkqhkiG9w0BAQQFADB5MRAwDgYDVQQKEwdSb290\n"
    "IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNB\n"
    "IENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRA\n"
    "Y2FjZXJ0Lm9yZzAeFw0wMzAzMzAxMjI5NDlaFw0zMzAzMjkxMjI5NDlaMHkxEDAO\n"
    "GCSNe9FINSkYQKyTYOGWhlC0elnYjyELn8+CkcY7v2vcB5G5l1YjqrZslMZIBjzk\n"
    "zk6q5PYvCdxTby78dOs6Y5nCpqyJvKeyRKANihDjbPIky/qbn3BHLt4Ui9SyIAmW\n"
    "omTxJBzcoTWcFbLUvFUufQb1nA5V9FrWk9p2rSVzTMVD\n"
    "-----END CERTIFICATE-----\n";
 
  curl_global_init(CURL_GLOBAL_ALL);
  ch = curl_easy_init();
 
  curl_easy_setopt(ch, CURLOPT_SSLCERTTYPE, "PEM");
  curl_easy_setopt(ch, CURLOPT_SSL_VERIFYPEER, 1L);
  curl_easy_setopt(ch, CURLOPT_URL, "https://www.example.com/");
 
  curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
  curl_easy_setopt(ch, CURLOPT_SSL_CTX_DATA, mypem);
  rv = curl_easy_perform(ch);
  if(!rv)
    printf("*** transfer succeeded ***\n");
  else
    printf("*** transfer failed ***\n");
 
  curl_easy_cleanup(ch);
  curl_global_cleanup();
  return rv;
}

History

Added in 7.11.0 for OpenSSL, in 7.42.0 for wolfSSL, in 7.54.0 for mbedTLS, in 7.83.0 in BearSSL.

Availability

Added in curl 7.10.6

Return value

CURLE_OK if supported; or an error such as:

CURLE_NOT_BUILT_IN - Not supported by the SSL backend

CURLE_UNKNOWN_OPTION