CURLOPT_SSLVERSION3

Usage

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLVERSION, long version);

Overview

Pass a long as parameter to control which version range of SSL/TLS versions to use.

The SSL and TLS versions have typically developed from the most insecure version to be more and more secure in this order through history: SSLv2, SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 and the most recent TLSv1.3.

Use one of the available defines for this purpose. The available options are:

CURL_SSLVERSION_DEFAULT

The default acceptable version range. The minimum acceptable version is by default TLSv1.2 since 8.16.0 (unless the TLS library has a stricter rule).

CURL_SSLVERSION_TLSv1

TLSv1.0 or later

CURL_SSLVERSION_SSLv2

SSLv2 - refused

CURL_SSLVERSION_SSLv3

SSLv3 - refused

CURL_SSLVERSION_TLSv1_0

TLSv1.0 or later

CURL_SSLVERSION_TLSv1_1

TLSv1.1 or later

CURL_SSLVERSION_TLSv1_2

TLSv1.2 or later

CURL_SSLVERSION_TLSv1_3

TLSv1.3 or later

The maximum TLS version can be set by using one of the CURL_SSLVERSION_MAX_ macros below. It is also possible to OR one of the CURL_SSLVERSION_ macros with one of the CURL_SSLVERSION_MAX_ macros.

CURL_SSLVERSION_MAX_DEFAULT

The flag defines the maximum supported TLS version by libcurl, or the default value from the SSL library is used. libcurl uses a sensible default maximum, which was TLSv1.2 up to before 7.61.0 and is TLSv1.3 since then - assuming the TLS library support it.

CURL_SSLVERSION_MAX_TLSv1_0

The flag defines maximum supported TLS version as TLSv1.0.

CURL_SSLVERSION_MAX_TLSv1_1

The flag defines maximum supported TLS version as TLSv1.1.

CURL_SSLVERSION_MAX_TLSv1_2

The flag defines maximum supported TLS version as TLSv1.2.

CURL_SSLVERSION_MAX_TLSv1_3

The flag defines maximum supported TLS version as TLSv1.3.

Default

CURL_SSLVERSION_DEFAULT

Protocols

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

All TLS backends support this option.

Examples

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    /* ask libcurl to use TLS version 1.0 or later */
    curl_easy_setopt(curl, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);
    /* Perform the request */
    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).