CURLINFO_CERTINFO - get the TLS certificate chain

Added in curl 7.19.1

Pass a pointer to a structcurl_certinfo * and it is set to point to a struct that holds info about the server's certificate chain, assuming you had CURLOPT_CERTINFO(3) enabled when the request was made. struct curl_certinfo { int num_of_certs; struct curl_slist **certinfo; }; The certinfo struct member is an array of linked lists of certificate information. The num_of_certs struct member is the number of certificates which is the number of elements in the array. Each certificate's list has items with textual information in the format "name:content" such as "Subject:Foo", "Issuer:Bar", etc. The items in each list varies depending on the SSL backend and the certificate.

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) { int i; struct curl_certinfo *ci; res = curl_easy_getinfo(curl, CURLINFO_CERTINFO, &ci); if(!res) { 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); } } See also the certinfo.c example.

GnuTLS support added in 7.42.0. Schannel support added in 7.50.0. Secure Transport support added in 7.79.0. mbedTLS support added in 8.9.0.

CURLINFO_CERTINFO - get the TLS certificate chain

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_getinfo(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_CAPATH(3), curl_easy_getinfo(3), curl_easy_setopt(3) libcurl 2025-06-16 CURLINFO_CERTINFO(3)

#include <curl/curl.h> CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_CERTINFO, struct curl_certinfo **chainp);