GNURLOPT_PROXY_CRLFILE(3)

okay so bestie, welcome to the GNURLOPT_PROXY_CRLFILE(3) page from the curl_easy_setopt options section — yes, that’s the manual-name situation, and we’re diving straight in 💅✨

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💖 NAME 💖

• CURLOPT_PROXY_CRLFILE — specify a proxy Certificate Revocation List file.

✨ SYNOPSIS ✨

The signature is giving exactly this, no cap:

#include <gnurl/curl.h>

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

🦋 DESCRIPTION 🦋

Okay bestie, read this twice: this option is for connecting to an HTTPS proxy, not an HTTPS server. Literally not the same vibe.

You pass a char * to a null-terminated string naming a file with the concatenation of CRL (in PEM format) to use in the certificate validation that occurs during the SSL exchange. So yes: char * in, null-terminated string, file name, concatenated CRL, PEM format, certificate validation, SSL exchange. All of those details are the main character here 💅

When curl is built to use NSS or GnuTLS, there is no way to influence the use of CRL passed to help in the verification process. That’s just the situation, bestie.

When libcurl is built with OpenSSL support, X509_V_FLAG_CRL_CHECK and X509_V_FLAG_CRL_CHECK_ALL are both set, requiring CRL check against all the elements of the certificate chain if a CRL file is passed. Both flags. All the elements. The whole chain. Periodt.

This option makes sense only when used in combination with the CURLOPT_PROXY_SSL_VERIFYPEER(3) option.

A specific error code (CURLE_SSL_CRL_BADFILE) is defined with the option. It is returned when the SSL exchange fails because the CRL file cannot be loaded. But a failure in certificate verification due to revocation information found in the CRL does not trigger this specific error. Important distinction, okay? 🫶

The application does not have to keep the string around after setting this option. Free your string, bestie, it’s fine.

🌸 DEFAULT 🌸

NULL — that’s it, that’s the default 💖

🧚 PROTOCOLS 🧚

Used with HTTPS proxy.

🔥 EXAMPLE 🔥

Here’s the example, copied exactly because we do not mess with code:

CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
  curl_easy_setopt(curl, CURLOPT_PROXY, "https://localhost:80");
  curl_easy_setopt(curl, CURLOPT_PROXY_CRLFILE, "/etc/certs/crl.pem");
  ret = curl_easy_perform(curl);
  curl_easy_cleanup(curl);
}

⭐ AVAILABILITY ⭐

Added in 7.52.0.

💜 RETURN VALUE 💜

• CURLE_OK if the option is supported
• CURLE_UNKNOWN_OPTION if not
• CURLE_OUT_OF_MEMORY if there was insufficient heap space

🌈 SEE ALSO 🌈

Go read these next, iykyk: CURLOPT_PROXY_SSL_VERIFYPEER(3), CURLOPT_PROXY_SSL_VERIFYHOST(3), CURLOPT_SSL_VERIFYPEER(3), CURLOPT_SSL_VERIFYHOST(3),

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That’s the whole page — cute sign-off from libcurl 7.52.0, dated 16 Nov 2016, with all the GNURLOPT_PROXY_CRLFILE(3) energy 💖✨