CURLOPT_PROXY_CAPATH - Man Page

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_CAPATH, char *capath);

Pass a char pointer to a null-terminated string naming a directory holding multiple CA certificates to verify the HTTPS proxy with. If libcurl is built against OpenSSL, the certificate directory must be prepared using the OpenSSL c_rehash utility. This makes sense only when CURLOPT_PROXY_SSL_VERIFYPEER(3) is enabled (which it is by default).

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 and switch back to internal default.

The default value for this can be figured out with CURLINFO_CAPATH(3).

NULL

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

This option works only with the following TLS backends: GnuTLS, OpenSSL and mbedTLS

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    /* using an HTTPS proxy */
    curl_easy_setopt(curl, CURLOPT_PROXY, "https://localhost:443");
    curl_easy_setopt(curl, CURLOPT_PROXY_CAPATH, "/etc/cert-dir");
    res = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

Added in curl 7.52.0

CURLE_OK if supported; or an error such as:

CURLE_NOT_BUILT_IN - Not supported by the SSL backend

CURLE_UNKNOWN_OPTION

CURLE_OUT_OF_MEMORY

CURLOPT_CAINFO(3), CURLOPT_DEBUGFUNCTION(3), CURLOPT_PROXY_CAINFO(3), CURLOPT_PROXY_SSL_VERIFYHOST(3), CURLOPT_STDERR(3)

curl_easy_setopt(3), CURLOPT_PROXY_CAINFO(3), CURLOPT_PROXY_CAINFO_BLOB(3), CURLOPT_PROXY_PINNEDPUBLICKEY(3), CURLOPT_PROXY_SSL_VERIFYPEER(3), libcurl-symbols(3).