CURLOPT_SSLVERSION(3)      curl_easy_setopt options      CURLOPT_SSLVERSION(3)

NAME
       CURLOPT_SSLVERSION - set 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: SSL v2, SSLv3, TLS v1.0, TLS v1.1, TLS v1.2 and the most
       recent TLS v1.3.

       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 TLS v1.0 since 7.39.0
                     (unless the TLS library has a stricter rule).

              CURL_SSLVERSION_TLSv1
                     TLS v1.0 or later

              CURL_SSLVERSION_SSLv2
                     SSL v2 - refused

              CURL_SSLVERSION_SSLv3
                     SSL v3 - refused

              CURL_SSLVERSION_TLSv1_0
                     TLS v1.0 or later (Added in 7.34.0)

              CURL_SSLVERSION_TLSv1_1
                     TLS v1.1 or later (Added in 7.34.0)

              CURL_SSLVERSION_TLSv1_2
                     TLS v1.2 or later (Added in 7.34.0)

              CURL_SSLVERSION_TLSv1_3
                     TLS v1.3 or later (Added in 7.52.0)

       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.
       The MAX macros are not supported for WolfSSL.

              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 will use a sensible default maximum, which
                     was TLS v1.2 up to before 7.61.0 and is TLS v1.3 since
                     then - assuming the TLS library support it. (Added in
                     7.54.0)

              CURL_SSLVERSION_MAX_TLSv1_0
                     The flag defines maximum supported TLS version as TLS
                     v1.0.  (Added in 7.54.0)

              CURL_SSLVERSION_MAX_TLSv1_1
                     The flag defines maximum supported TLS version as TLS
                     v1.1.  (Added in 7.54.0)

              CURL_SSLVERSION_MAX_TLSv1_2
                     The flag defines maximum supported TLS version as TLS
                     v1.2.  (Added in 7.54.0)

              CURL_SSLVERSION_MAX_TLSv1_3
                     The flag defines maximum supported TLS version as TLS
                     v1.3.  (Added in 7.54.0)

       In versions of curl prior to 7.54 the CURL_SSLVERSION_TLS options were
       documented to allow only the specified TLS version, but behavior was
       inconsistent depending on the TLS library.

DEFAULT
       CURL_SSLVERSION_DEFAULT

PROTOCOLS
       All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

EXAMPLE
       CURL *curl = curl_easy_init();
       if(curl) {
         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 */
         curl_easy_perform(curl);
       }

AVAILABILITY
       SSLv2 and SSLv3 are refused completely since curl 7.77.0

       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.

RETURN VALUE
       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION
       if not.

SEE ALSO
       CURLOPT_USE_SSL(3), CURLOPT_HTTP_VERSION(3),
       CURLOPT_PROXY_SSLVERSION(3), CURLOPT_IPRESOLVE(3)

libcurl 7.77.0                  March 22, 2021           CURLOPT_SSLVERSION(3)