curl/docs/libcurl/opts/CURLOPT_SSLVERSION.md

c	SPDX-License-Identifier	Title	Section	Source	See-also	Protocol	TLS-backend	Added-in
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.	curl	CURLOPT_SSLVERSION	3	libcurl	CURLOPT_HTTP_VERSION (3) CURLOPT_IPRESOLVE (3) CURLOPT_PROXY_SSLVERSION (3) CURLOPT_USE_SSL (3)	TLS	All	7.1

NAME

CURLOPT_SSLVERSION - preferred TLS/SSL version

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLVERSION, long version);

DESCRIPTION

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%

EXAMPLE

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);
  }
}

HISTORY

SSLv2 is disabled by default since 7.18.1. Other SSL versions availability may vary depending on which backend libcurl has been built to use.

SSLv3 is disabled by default since 7.39.0.

SSLv2 and SSLv3 are refused completely since curl 7.77.0

Since 8.10.0 wolfSSL is fully supported. Before 8.10.0 the MAX macros were not supported with wolfSSL and the other macros did not set a minimum, but restricted the TLS version to only the specified one.

Rustls support added in 8.10.0.

CURL_SSLVERSION_* macros became long types in 8.16.0, prior to this version a long cast was necessary when passed to curl_easy_setopt(3).

%AVAILABILITY%

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).