CURLOPT_SSLENGINE - Set SSL engine or provider

Added in curl 7.9.3

NULL

Pass a pointer to a null-terminated string as parameter. It is used as the identifier for the engine or provider you want to use for your private key. OpenSSL 1 had engines, OpenSSL 3 has providers. The application does not have to keep the string around after setting this option. When asking libcurl to use a provider, the application can also optionally provide a property, a set of name value pairs. Such a property can be specified separated from the name with a colon (:). 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_SSLENGINE, "dynamic"); res = curl_easy_perform(curl); curl_easy_cleanup(curl); } }

CURLOPT_SSLENGINE - Set SSL engine or provider

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

CURLE_OK - Engine found. CURLE_SSL_ENGINE_NOTFOUND - Engine not found, or OpenSSL was not built with engine support. CURLE_SSL_ENGINE_INITFAILED - Engine found but initialization failed. CURLE_NOT_BUILT_IN - Option not built in, OpenSSL is not the SSL backend. CURLE_UNKNOWN_OPTION - Option not recognized. CURLE_OUT_OF_MEMORY - Insufficient heap space.

CURLINFO_SSL_ENGINES(3), CURLOPT_SSLENGINE_DEFAULT(3), CURLOPT_SSLKEY(3) libcurl 2025-06-16 CURLOPT_SSLENGINE(3)

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