1---
2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
3SPDX-License-Identifier: curl
4Title: CURLOPT_SSLVERSION
5Section: 3
6Source: libcurl
7See-also:
8  - CURLOPT_HTTP_VERSION (3)
9  - CURLOPT_IPRESOLVE (3)
10  - CURLOPT_PROXY_SSLVERSION (3)
11  - CURLOPT_USE_SSL (3)
12Protocol:
13  - TLS
14TLS-backend:
15  - All
16---
17
18# NAME
19
20CURLOPT_SSLVERSION - preferred TLS/SSL version
21
22# SYNOPSIS
23
24~~~c
25#include <curl/curl.h>
26
27CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLVERSION, long version);
28~~~
29
30# DESCRIPTION
31
32Pass a long as parameter to control which version range of SSL/TLS versions to
33use.
34
35The SSL and TLS versions have typically developed from the most insecure
36version to be more and more secure in this order through history: SSL v2,
37SSLv3, TLS v1.0, TLS v1.1, TLS v1.2 and the most recent TLS v1.3.
38
39Use one of the available defines for this purpose. The available options are:
40
41## CURL_SSLVERSION_DEFAULT
42
43The default acceptable version range. The minimum acceptable version is by
44default TLS v1.0 since 7.39.0 (unless the TLS library has a stricter rule).
45
46## CURL_SSLVERSION_TLSv1
47
48TLS v1.0 or later
49
50## CURL_SSLVERSION_SSLv2
51
52SSL v2 - refused
53
54## CURL_SSLVERSION_SSLv3
55
56SSL v3 - refused
57
58## CURL_SSLVERSION_TLSv1_0
59
60TLS v1.0 or later (Added in 7.34.0)
61
62## CURL_SSLVERSION_TLSv1_1
63
64TLS v1.1 or later (Added in 7.34.0)
65
66## CURL_SSLVERSION_TLSv1_2
67
68TLS v1.2 or later (Added in 7.34.0)
69
70## CURL_SSLVERSION_TLSv1_3
71
72TLS v1.3 or later (Added in 7.52.0)
73
74The maximum TLS version can be set by using *one* of the
75CURL_SSLVERSION_MAX_ macros below. It is also possible to OR *one* of the
76CURL_SSLVERSION_ macros with *one* of the CURL_SSLVERSION_MAX_ macros.
77The MAX macros are not supported for WolfSSL.
78
79## CURL_SSLVERSION_MAX_DEFAULT
80
81The flag defines the maximum supported TLS version by libcurl, or the default
82value from the SSL library is used. libcurl uses a sensible default maximum,
83which was TLS v1.2 up to before 7.61.0 and is TLS v1.3 since then - assuming
84the TLS library support it. (Added in 7.54.0)
85
86## CURL_SSLVERSION_MAX_TLSv1_0
87
88The flag defines maximum supported TLS version as TLS v1.0.
89(Added in 7.54.0)
90
91## CURL_SSLVERSION_MAX_TLSv1_1
92
93The flag defines maximum supported TLS version as TLS v1.1.
94(Added in 7.54.0)
95
96## CURL_SSLVERSION_MAX_TLSv1_2
97
98The flag defines maximum supported TLS version as TLS v1.2.
99(Added in 7.54.0)
100
101## CURL_SSLVERSION_MAX_TLSv1_3
102
103The flag defines maximum supported TLS version as TLS v1.3.
104(Added in 7.54.0)
105
106In versions of curl prior to 7.54 the CURL_SSLVERSION_TLS options were
107documented to allow *only* the specified TLS version, but behavior was
108inconsistent depending on the TLS library.
109
110# DEFAULT
111
112CURL_SSLVERSION_DEFAULT
113
114# EXAMPLE
115
116~~~c
117int main(void)
118{
119  CURL *curl = curl_easy_init();
120  if(curl) {
121    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
122
123    /* ask libcurl to use TLS version 1.0 or later */
124    curl_easy_setopt(curl, CURLOPT_SSLVERSION, (long)CURL_SSLVERSION_TLSv1);
125
126    /* Perform the request */
127    curl_easy_perform(curl);
128  }
129}
130~~~
131
132# AVAILABILITY
133
134SSLv2 and SSLv3 are refused completely since curl 7.77.0
135
136SSLv2 is disabled by default since 7.18.1. Other SSL versions availability may
137vary depending on which backend libcurl has been built to use.
138
139SSLv3 is disabled by default since 7.39.0.
140
141# RETURN VALUE
142
143Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
144