CURLOPT_PROXY_SSLKEY - private key file for HTTPS proxy client cert

Added in curl 7.52.0

NULL

Pass a pointer to a null-terminated string as parameter. The string should be the filename of your private key used for connecting to the HTTPS proxy. The default format is "PEM" and can be changed with CURLOPT_PROXY_SSLKEYTYPE(3). (Windows, iOS and macOS) This option is ignored by Secure Transport and Schannel SSL backends because they expect the private key to be already present in the key chain or PKCS#12 file containing the certificate. 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.

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_PROXY, "https://proxy"); curl_easy_setopt(curl, CURLOPT_PROXY_SSLCERT, "client.pem"); curl_easy_setopt(curl, CURLOPT_PROXY_SSLKEY, "key.pem"); curl_easy_setopt(curl, CURLOPT_PROXY_KEYPASSWD, "s3cret"); res = curl_easy_perform(curl); curl_easy_cleanup(curl); } }

CURLOPT_PROXY_SSLKEY - private key file for HTTPS proxy client cert

This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. This option works only with the following TLS backends: OpenSSL, Schannel, mbedTLS and wolfSSL

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).

CURLOPT_PROXY_SSLCERT(3), CURLOPT_PROXY_SSLKEYTYPE(3), CURLOPT_SSLCERT(3), CURLOPT_SSLKEY(3), CURLOPT_SSLKEYTYPE(3) libcurl 2025-06-16 CURLOPT_PROXY_SSLKEY(3)

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