curl / libcurl / API / curl_easy_setopt / CURLOPT_HTTPAUTH

CURLOPT_HTTPAUTH explained

Name

CURLOPT_HTTPAUTH - HTTP server authentication methods to try

Synopsis

#include <curl/curl.h>
 
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPAUTH, long bitmask);

Description

Pass a long as parameter, which is set to a bitmask, to tell libcurl which authentication method(s) you want it to use speaking to the remote server.

The available bits are listed below. If more than one bit is set, libcurl first queries the host to see which authentication methods it supports and then picks the best one you allow it to use. For some methods, this induces an extra network round-trip. Set the actual name and password with the CURLOPT_USERPWD option or with the CURLOPT_USERNAME and the CURLOPT_PASSWORD options.

For authentication with a proxy, see CURLOPT_PROXYAUTH.

CURLAUTH_BASIC

HTTP Basic authentication. This is the default choice, and the only method that is in wide-spread use and supported virtually everywhere. This sends the username and password over the network in plain text, easily captured by others.

CURLAUTH_DIGEST

HTTP Digest authentication. Digest authentication is defined in RFC 2617 and is a more secure way to do authentication over public networks than the regular old-fashioned Basic method.

CURLAUTH_DIGEST_IE

HTTP Digest authentication with an IE flavor. Digest authentication is defined in RFC 2617 and is a more secure way to do authentication over public networks than the regular old-fashioned Basic method. The IE flavor is simply that libcurl uses a special "quirk" that IE is known to have used before version 7 and that some servers require the client to use.

CURLAUTH_BEARER

HTTP Bearer token authentication, used primarily in OAuth 2.0 protocol.

You can set the Bearer token to use with CURLOPT_XOAUTH2_BEARER.

CURLAUTH_NEGOTIATE

HTTP Negotiate (SPNEGO) authentication. Negotiate authentication is defined in RFC 4559 and is the most secure way to perform authentication over HTTP.

You need to build libcurl with a suitable GSS-API library or SSPI on Windows for this to work.

CURLAUTH_NTLM

HTTP NTLM authentication. A proprietary protocol invented and used by Microsoft. It uses a challenge-response and hash concept similar to Digest, to prevent the password from being eavesdropped.

You need to build libcurl with either OpenSSL or GnuTLS support for this option to work, or build libcurl on Windows with SSPI support.

CURLAUTH_NTLM_WB

Support for this is removed since libcurl 8.8.0.

NTLM delegating to winbind helper. Authentication is performed by a separate binary application that is executed when needed. The name of the application is specified at compile time but is typically /usr/bin/ntlm_auth.

Note that libcurl forks when necessary to run the winbind application and kill it when complete, calling waitpid() to await its exit when done. On POSIX operating systems, killing the process causes a SIGCHLD signal to be raised (regardless of whether CURLOPT_NOSIGNAL is set), which must be handled intelligently by the application. In particular, the application must not unconditionally call wait() in its SIGCHLD signal handler to avoid being subject to a race condition. This behavior is subject to change in future versions of libcurl.

CURLAUTH_ANY

This is a convenience macro that sets all bits and thus makes libcurl pick any it finds suitable. libcurl automatically selects the one it finds most secure.

CURLAUTH_ANYSAFE

This is a convenience macro that sets all bits except Basic and thus makes libcurl pick any it finds suitable. libcurl automatically selects the one it finds most secure.

CURLAUTH_ONLY

This is a meta symbol. OR this value together with a single specific auth value to force libcurl to probe for unrestricted auth and if not, only that single auth algorithm is acceptable.

CURLAUTH_AWS_SIGV4

provides AWS V4 signature authentication on HTTPS header see CURLOPT_AWS_SIGV4.

Default

CURLAUTH_BASIC

Protocols

This functionality affects http only

Example

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode ret;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    /* allow whatever auth the server speaks */
    curl_easy_setopt(curl, CURLOPT_HTTPAUTH, (long)CURLAUTH_ANY);
    curl_easy_setopt(curl, CURLOPT_USERPWD, "james:bond");
    ret = curl_easy_perform(curl);
  }
}

History

CURLAUTH_DIGEST_IE was added in 7.19.3

CURLAUTH_ONLY was added in 7.21.3

CURLAUTH_NTLM_WB was added in 7.22.0

CURLAUTH_BEARER was added in 7.61.0

CURLAUTH_AWS_SIGV4 was added in 7.74.0

Availability

Added in curl 7.10.6

Return value

Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or CURLE_NOT_BUILT_IN if the bitmask specified no supported authentication methods.