xref: /aosp_15_r20/external/curl/docs/libcurl/opts/CURLOPT_SSLVERSION.md (revision 6236dae45794135f37c4eb022389c904c8b0090d)

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

# NAME

CURLOPT_SSLVERSION - preferred TLS/SSL version

# SYNOPSIS

~~~c
#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%

# EXAMPLE

~~~c
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%

# RETURN VALUE

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