Tribblix: manual page: CURLOPT_PROXY

CURLOPT_PROXY_ISSUERCERT(3) Introduction to Library Functions

NAME

CURLOPT_PROXY_ISSUERCERT - proxy issuer SSL certificate filename

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_ISSUERCERT, char *file);

DESCRIPTION

Pass a char pointer to a null-terminated string naming a file holding
a CA certificate in PEM format. If the option is set, an additional
check against the peer certificate is performed to verify the issuer
of the HTTPS proxy is indeed the one associated with the certificate
provided by the option. This additional check is useful in
multi-level PKI where one needs to enforce that the peer certificate
is from a specific branch of the tree.

This option makes sense only when used in combination with the
CURLOPT_PROXY_SSL_VERIFYPEER(3) option. Otherwise, the result of the
check is not considered as failure.

A specific error code (CURLE_SSL_ISSUER_ERROR) is defined with the
option, which is returned if the setup of the SSL/TLS session has
failed due to a mismatch with the issuer of peer certificate
(CURLOPT_PROXY_SSL_VERIFYPEER(3) has to be set too for the check to
fail).

The application does not have to keep the string around after setting
this option.

Using this option multiple times makes the last set string override
the previous ones. Set it to NULL to disable its use again.

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: GnuTLS and
OpenSSL

EXAMPLE

int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
/* using an HTTPS proxy */
curl_easy_setopt(curl, CURLOPT_PROXY, "https://localhost:443");
curl_easy_setopt(curl, CURLOPT_PROXY_ISSUERCERT, "/etc/certs/cacert.pem");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}

AVAILABILITY

Added in curl 7.71.0

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).