repo/core/curl/files/CURLINFO_CERTINFO.3

.\" generated by cd2nroff 0.1 from CURLINFO_CERTINFO.md
.TH CURLINFO_CERTINFO 3 "2024-11-09" libcurl
.SH NAME
CURLINFO_CERTINFO \- get the TLS certificate chain
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_CERTINFO,
                           struct curl_certinfo **chainp);
.fi
.SH DESCRIPTION
Pass a pointer to a \fIstruct curl_certinfo \fP* and it is set to point to a
struct that holds info about the server\(aqs certificate chain, assuming you had
\fICURLOPT_CERTINFO(3)\fP enabled when the request was made.

.nf
struct curl_certinfo {
  int num_of_certs;
  struct curl_slist **certinfo;
};
.fi

The \fIcertinfo\fP struct member is an array of linked lists of certificate
information. The \fInum_of_certs\fP struct member is the number of certificates
which is the number of elements in the array. Each certificate\(aqs 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.
.SH PROTOCOLS
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 and Secure Transport
.SH EXAMPLE
.nf
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);
  }
}
.fi

See also the \fIcertinfo.c\fP example.
.SH HISTORY
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.
.SH AVAILABILITY
Added in curl 7.19.1
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH SEE ALSO
.BR CURLINFO_CAPATH (3),
.BR curl_easy_getinfo (3),
.BR curl_easy_setopt (3)