CURLOPT_ISSUERCERT(3) Library Functions Manual CURLOPT_ISSUERCERT(3)
NAME
CURLOPT_ISSUERCERT - issuer SSL certificate filename
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ISSUERCERT, char *file);
DESCRIPTION
Pass a char pointer to a null-terminated string naming a file holding a
CA certificate in PEM format. If the option is set, an additional check
against the peer certificate is performed to verify the issuer is indeed
the one associated with the certificate provided by the option. This ad-
ditional check is useful in multi-level PKI where one needs to enforce
that the peer certificate is from a specific branch of the tree.
This option makes sense only when used in combination with the CUR-
LOPT_SSL_VERIFYPEER(3) option. Otherwise, the result of the check is not
considered as failure.
A specific error code (CURLE_SSL_ISSUER_ERROR) is defined with the op-
tion, which is returned if the setup of the SSL/TLS session has failed
due to a mismatch with the issuer of peer certificate (CURLOPT_SSL_VERI-
FYPEER(3) has to be set too for the check to fail). (Added in 7.19.0)
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again.
The application does not have to keep the string around after setting
this option.
DEFAULT
NULL
PROTOCOLS
This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS,
POP3S, SMTPS etc.
This option works only with the following TLS backends: GnuTLS and
OpenSSL
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
curl_easy_setopt(curl, CURLOPT_ISSUERCERT, "/etc/certs/cacert.pem");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
AVAILABILITY
Added in curl 7.19.0
RETURN VALUE
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).
SEE ALSO
CURLOPT_CRLFILE(3), CURLOPT_SSL_VERIFYHOST(3), CURLOPT_SSL_VERIFYPEER(3)
libcurl 2026-07-12 CURLOPT_ISSUERCERT(3)
Generated by dwww version 1.16 on Sat Oct 3 05:46:36 CEST 2026.