Ubuntu Manpage: CURLOPT_SSLVERSION - preferred TLS/SSL version

Provided by: libcurl4-doc_8.11.0-1ubuntu2_all

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.