curl / libcurl / API / curl_easy_setopt / CURLOPT_SOCKS5_AUTH

CURLOPT_SOCKS5_AUTH explained

Name

CURLOPT_SOCKS5_AUTH - methods for SOCKS5 proxy authentication

Synopsis

#include <curl/curl.h>
 
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SOCKS5_AUTH, long bitmask);

Description

Pass a long as parameter, which is set to a bitmask, to tell libcurl which authentication method(s) are allowed for SOCKS5 proxy authentication. The only supported flags are CURLAUTH_BASIC, which allows username/password authentication, and CURLAUTH_GSSAPI, which allows GSS-API authentication. Set the actual username and password with the CURLOPT_PROXYUSERPWD option.

libcurl offers the SOCKS5 "no authentication" method in addition to the ones in the bitmask, and accepts it if the proxy selects it. CURLAUTH_NONE is zero and therefore cannot be combined with the other flags; setting the bitmask to CURLAUTH_NONE makes libcurl offer only the no authentication method.

Add CURLAUTH_ONLY to the bitmask to require authentication. libcurl then does not offer the no authentication method, and rejects it with CURLE_PROXY if the proxy selects it anyway. A connection that was set up without SOCKS5 authentication is also not reused for such a transfer. Setting CURLAUTH_ONLY without CURLAUTH_BASIC or CURLAUTH_GSSAPI makes curl_easy_setopt return CURLE_BAD_FUNCTION_ARGUMENT.

The specific socks authentication method is an access property, it does not change the security context. This means that this option changes how the connection and access to the proxy happens when a connection is setup, but it does not affect which proxy connections libcurl can reuse. libcurl may reuse a connection that was set up with a different socks authentication method. Proxy connection reuse still depends on other properties matching, such as the protocol, proxy hostname, port number, credentials and other settings that affect the connection.

Default

CURLAUTH_BASIC | CURLAUTH_GSSAPI

Protocols

This functionality affects all supported protocols

Example

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
 
    /* request to use a SOCKS5 proxy */
    curl_easy_setopt(curl, CURLOPT_PROXY, "socks5://user:pass@myproxy.com");
 
    /* enable username/password authentication only */
    curl_easy_setopt(curl, CURLOPT_SOCKS5_AUTH, CURLAUTH_BASIC);
 
    /* Perform the request */
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

History

CURLAUTH_* macros became long types in 7.26.0, prior to this version a long cast was necessary when passed to curl_easy_setopt.

CURLAUTH_ONLY is supported since 8.23.0.

Availability

Added in curl 7.55.0

Return value

curl_easy_setopt returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors.