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.  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 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 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.

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)