CURLOPT_SSLKEY(3) Introduction to Library Functions CURLOPT_SSLKEY(3)

NAME


CURLOPT_SSLKEY - private key file for TLS and SSL client cert

SYNOPSIS


#include <curl/curl.h>

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

DESCRIPTION


Pass a pointer to a null-terminated string as parameter. The string
should be the filename of your private key. The default format is
"PEM" and can be changed with CURLOPT_SSLKEYTYPE(3).

(Windows) This option is ignored by the Schannel SSL 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,
Rustls, 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_SSLCERT, "client.pem");
curl_easy_setopt(curl, CURLOPT_SSLKEY, "key.pem");
curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}

AVAILABILITY


Added in curl 7.9.3

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_SSLCERT(3), CURLOPT_SSLKEYTYPE(3), CURLOPT_SSLKEY_BLOB(3)

libcurl 2026-01-08 CURLOPT_SSLKEY(3)