curl / libcurl / API / curl_easy_setopt / CURLOPT_CAINFO

CURLOPT_CAINFO explained

Name

CURLOPT_CAINFO - path to Certificate Authority (CA) bundle

Synopsis

#include <curl/curl.h>
 
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CAINFO, char *path);

Description

Pass a char pointer to a null-terminated string naming a file holding one or more certificates to verify the peer with.

If CURLOPT_SSL_VERIFYPEER is zero and you avoid verifying the server's certificate, CURLOPT_CAINFO need not even indicate an accessible file.

This option is by default set to the system path where libcurl's CA certificate bundle is assumed to be stored, as established at build time.

(iOS and macOS) When curl uses Secure Transport this option is supported. If the option is not set, then curl uses the certificates in the system and user Keychain to verify the peer.

(Schannel) This option is supported for Schannel in Windows 7 or later but we recommend not using it until Windows 8 since it works better starting then. If the option is not set, then curl uses the certificates in the Windows' store of root certificates (the default for Schannel).

The application does not have to keep the string around after setting this option.

Using this option multiple times makes the last set string override the previous ones. Set it to NULL to disable its use again.

The default value for this can be figured out with CURLINFO_CAINFO.

Default

Built-in system specific. When curl is built with Secure Transport or Schannel, this option is not set by default.

Protocols

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

All TLS backends support this option.

Example

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_CAINFO, "/etc/certs/cabundle.pem");
    curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

History

Schannel support added in libcurl 7.60.

Availability

Added in curl 7.4.2

Return value

Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.