Tribblix: manual page: CURLOPT_PROXY

CURLOPT_PROXY_CAINFO(3) Introduction to Library Functions

NAME

CURLOPT_PROXY_CAINFO - path to proxy Certificate Authority (CA)
bundle

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_CAINFO, char *path);

DESCRIPTION

This option is for connecting to an HTTPS proxy, not an HTTPS server.

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

If CURLOPT_PROXY_SSL_VERIFYPEER(3) is zero and you avoid verifying
the server's certificate, CURLOPT_PROXY_CAINFO(3) 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 only) If curl is built against Secure Transport, then
this option is supported for backward compatibility with other SSL
engines, but it should not be set. If the option is not set, then
curl uses the certificates in the system and user Keychain to verify
the peer, which is the preferred method of verifying the peer's
certificate chain.

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
switches back to internal default.

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

DEFAULT

Built-in system specific

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) {
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_CAINFO, "/etc/certs/cabundle.pem");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}

NOTES

For TLS backends that do not support certificate files, the
CURLOPT_PROXY_CAINFO(3) option is ignored. Refer to
https://curl.se/docs/ssl-compared.html

AVAILABILITY

Added in curl 7.52.0

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).