Ubuntu Manpage: CURLOPT_PROXY_SSL_VERIFYPEER - verify the proxy's SSL certificate

NAME

       CURLOPT_PROXY_SSL_VERIFYPEER - verify the proxy's SSL certificate

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_SSL_VERIFYPEER,
                                 long verify);

DESCRIPTION

Pass a long as parameter set to 1L to enable or 0L to disable.

This option tells curl to verifies the authenticity of the HTTPS proxy's certificate. A
value of 1 means curl verifies; 0 (zero) means it does not.

This is the proxy version of CURLOPT_SSL_VERIFYPEER(3) that is used for ordinary HTTPS
servers.

When negotiating a TLS or SSL connection, the server sends a certificate indicating its
identity. Curl verifies whether the certificate is authentic, i.e. that you can trust that
the server is who the certificate says it is. This trust is based on a chain of digital
signatures, rooted in certification authority (CA) certificates you supply. curl uses a
default bundle of CA certificates (the path for that is determined at build time) and you
can specify alternate certificates with the CURLOPT_PROXY_CAINFO(3) option or the
CURLOPT_PROXY_CAPATH(3) option.

When CURLOPT_PROXY_SSL_VERIFYPEER(3) is enabled, and the verification fails to prove that
the certificate is authentic, the connection fails. When the option is zero, the peer
certificate verification succeeds regardless.

Authenticating the certificate is not enough to be sure about the server. You typically
also want to ensure that the server is the server you mean to be talking to. Use
CURLOPT_PROXY_SSL_VERIFYHOST(3) for that. The check that the host name in the certificate
is valid for the host name you are connecting to is done independently of the
CURLOPT_PROXY_SSL_VERIFYPEER(3) option.

WARNING: disabling verification of the certificate allows bad guys to man-in-the-middle
the communication without you knowing it. Disabling verification makes the communication
insecure. Just having encryption on a transfer is not enough as you cannot be sure that
you are communicating with the correct end-point.

DEFAULT

PROTOCOLS

All

EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

         /* Set the default value: strict certificate check please */
         curl_easy_setopt(curl, CURLOPT_PROXY_SSL_VERIFYPEER, 1L);

         curl_easy_perform(curl);
       }

AVAILABILITY

       Added in 7.52.0

       If built TLS enabled.

RETURN VALUE

       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.