CURLOPT_PROXY_ISSUERCERT

Section: curl_easy_setopt options (3)
Updated: November 04, 2020
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NAME

CURLOPT_PROXY_ISSUERCERT - proxy issuer SSL certificate filename

SYNOPSIS

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

DESCRIPTION

Pass a char * 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 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.

DEFAULT

NULL

PROTOCOLS

All TLS-based protocols

EXAMPLE

CURL *curl = curl_easy_init();
if(curl) {
  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");
  ret = curl_easy_perform(curl);
  curl_easy_cleanup(curl);
}

AVAILABILITY

Added in libcurl 7.71.0. This option is supported by the OpenSSL backends.

RETURN VALUE

Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.