CURLOPT_PROXY_SSLKEY(3) Introduction to Library Functions

NAME

CURLOPT_PROXY_SSLKEY - private key file for HTTPS proxy client cert

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_SSLKEY, char *keyfile);

DESCRIPTION

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).

This option is ignored by the Schannel backend because it expects 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.

DEFAULT

NULL

PROTOCOLS

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

EXAMPLE

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_KEYPASSWD, "s3cret");
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}

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).

SEE ALSO

CURLOPT_PROXY_SSLCERT(3), CURLOPT_PROXY_SSLKEYTYPE(3),
CURLOPT_SSLCERT(3), CURLOPT_SSLKEY(3), CURLOPT_SSLKEYTYPE(3)

libcurl 2026-01-08 CURLOPT_PROXY_SSLKEY(3)