CURLOPT_SSLVERSION(3)      Library Functions Manual      CURLOPT_SSLVERSION(3)

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: 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.

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

       All TLS backends support this option.

EXAMPLE
       int main(void)
       {
         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, (long)CURL_SSLVERSION_TLSv1);

           /* Perform the request */
           curl_easy_perform(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.

AVAILABILITY
       Added in curl 7.1

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

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

libcurl                           2024-11-07             CURLOPT_SSLVERSION(3)