CURLOPT_CERTINFO - request SSL certificate information

Added in curl 7.19.1

0

Pass a long set to 1 to enable libcurl's certificate chain info gatherer. With this enabled, libcurl extracts lots of information and data about the certificates in the certificate chain used in the SSL connection. This data may then be retrieved after a transfer using curl_easy_getinfo(3) and its option CURLINFO_CERTINFO(3).

int main(void) { CURL *curl = curl_easy_init(); if(curl) { CURLcode res; 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); res = curl_easy_perform(curl); if(!res) { struct curl_certinfo *ci; res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ci); if(!res) { 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); } }

Schannel support added in 7.50.0. Secure Transport support added in 7.79.0. mbedTLS support added in 8.9.0.

CURLOPT_CERTINFO - request SSL certificate information

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. This option works only with the following TLS backends: GnuTLS, OpenSSL, Schannel, Secure Transport and rustls

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).

CURLINFO_CAINFO(3), CURLINFO_CAPATH(3), CURLINFO_CERTINFO(3), CURLOPT_CAINFO(3), CURLOPT_SSL_VERIFYPEER(3) libcurl 2025-06-16 CURLOPT_CERTINFO(3)

#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CERTINFO, long certinfo);