CURLOPT_CERTINFO(3)

💅 CURLOPT_CERTINFO(3) — the libcurl girlies' guide ✨

Okay so bestie, you're reading a page from the libcurl manual — CURLOPT_CERTINFO(3), to be exact 🎀 — and honestly? It's a good one. Let's get into it.

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🌸 NAME 🌸

CURLOPT_CERTINFO — the option where you're literally asking for SSL certificate information 🦋

✨ SYNOPSIS ✨

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CERTINFO, long certinfo);

💖 DESCRIPTION 💖

So here's the vibe: you pass a long set to 1 to turn on libcurl's certificate chain info gatherer 👑. Like, you're telling it "girl, go collect the lore."

With this enabled, libcurl extracts lots of information and data about the certificates in the certificate chain used in the SSL connection 🔥. It's giving detective energy, no cap.

Then, after the transfer is done, you can pull all that data back out using curl_easy_getinfo(3) and its option CURLINFO_CERTINFO(3) 🫶. The way that it's a two-step situation — first you set it, then you get it — iykyk.

🎀 DEFAULT 🎀

0

(Yeah. Off. Not doing the thing. As it should be 💅)

🌈 PROTOCOLS 🌈

This functionality affects all TLS based protocols, bestie — so we're talking HTTPS, FTPS, IMAPS, POP3S, SMTPS, etc. ⭐ The whole TLS friend group.

Heads up though: this option works only with the following TLS backends — GnuTLS, OpenSSL, Rustls and Schannel 🙈. Everyone else is not invited to this particular party.

🧚 EXAMPLE 🧚

Okay this is the part where we actually do it. Look at her go:

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://www.example.com/");

    /* connect to any HTTPS site, trusted or not */
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);

    curl_easy_setopt(curl, CURLOPT_CERTINFO, 1L);

    result = curl_easy_perform(curl);

    if(!result) {
      struct curl_certinfo *ci;
      result = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ci);

      if(!result) {
        int i;
        printf("%d certs!\n", ci->num_of_certs);

        for(i = 0; i < ci->num_of_certs; i++) {
          struct curl_slist *slist;

          for(slist = ci->certinfo[i]; slist; slist = slist->next)
            printf("%s\n", slist->data);
        }
      }
    }
    curl_easy_cleanup(curl);
  }
}

Note the comment in there — it connects to any HTTPS site, trusted or not 😭. That's the demo being a demo, bestie, don't ship that energy to prod.

🦋 HISTORY 🦋

• Schannel support added in 7.50.0 ✨
• mbedTLS support added in 8.9.0 💜

🌟 AVAILABILITY 🌟

Added in curl 7.19.1 — she's been iconic for a minute 👑

🔥 RETURN VALUE 🔥

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

CURLE_OK (0) means everything was OK 💚. Non-zero means an error occurred — see libcurl-errors(3) for the whole breakdown.

💀 SEE ALSO 💀

• CURLINFO_CAINFO(3)
• CURLINFO_CAPATH(3)
• CURLINFO_CERTINFO(3)
• CURLOPT_CAINFO(3)
• CURLOPT_SSL_VERIFYPEER(3)

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and that's the whole page, bestie 🫶 this cutie was brought to you by libcurl, dated 2026-10-12, and she's filed under CURLOPT_CERTINFO(3). go get those certs 💅✨