CURLOPT_PROXY_SSLKEYTYPE(3)

CURLOPT_PROXY_SSLKEYTYPE3

Type of the proxy private key file

Usage

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

Overview

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

Pass a pointer to a null-terminated string as parameter. The string should be the format of your private key. Supported formats are "PEM", "DER", "ENG" and "PROV" (the latter added in curl 8.12.0).

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.

Protocols

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

This option works only with the following TLS backends: OpenSSL and wolfSSL

Examples

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_PROXY, "https://proxy.example");
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLCERT, "client.pem");
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLKEY, "key.pem");
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLKEYTYPE, "PEM");
    curl_easy_setopt(curl, CURLOPT_PROXY_KEYPASSWD, "s3cret");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

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).

Releases

6 releases since Debian 9 (Stretch); the text changed 5 times.

  1. 9
  2. 10
  3. 11
  4. 12
  5. 13
  6. Arch

Availability

Added in curl 7.52.0

From curl 8.23.0-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.