1---
2c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
3SPDX-License-Identifier: curl
4Title: CURLOPT_SSL_VERIFYPEER
5Section: 3
6Source: libcurl
7See-also:
8  - CURLINFO_CAINFO (3)
9  - CURLINFO_CAPATH (3)
10  - CURLOPT_CAINFO (3)
11  - CURLOPT_PROXY_SSL_VERIFYHOST (3)
12  - CURLOPT_PROXY_SSL_VERIFYPEER (3)
13  - CURLOPT_SSL_VERIFYHOST (3)
14---
15
16# NAME
17
18CURLOPT_SSL_VERIFYPEER - verify the peer's SSL certificate
19
20# SYNOPSIS
21
22~~~c
23#include <curl/curl.h>
24
25CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_VERIFYPEER, long verify);
26~~~
27
28# DESCRIPTION
29
30Pass a long as parameter to enable or disable.
31
32This option determines whether curl verifies the authenticity of the peer's
33certificate. A value of 1 means curl verifies; 0 (zero) means it does not.
34
35When negotiating a TLS or SSL connection, the server sends a certificate
36indicating its identity. Curl verifies whether the certificate is authentic,
37i.e. that you can trust that the server is who the certificate says it is.
38This trust is based on a chain of digital signatures, rooted in certification
39authority (CA) certificates you supply. curl uses a default bundle of CA
40certificates (the path for that is determined at build time) and you can
41specify alternate certificates with the CURLOPT_CAINFO(3) option or the
42CURLOPT_CAPATH(3) option.
43
44When CURLOPT_SSL_VERIFYPEER(3) is enabled, and the verification fails to
45prove that the certificate is signed by a CA, the connection fails.
46
47When this option is disabled (set to zero), the CA certificates are not loaded
48and the peer certificate verification is simply skipped.
49
50Authenticating the certificate is not enough to be sure about the server. You
51typically also want to ensure that the server is the server you mean to be
52talking to. Use CURLOPT_SSL_VERIFYHOST(3) for that. The check that the host
53name in the certificate is valid for the hostname you are connecting to is
54done independently of the CURLOPT_SSL_VERIFYPEER(3) option.
55
56WARNING: disabling verification of the certificate allows bad guys to
57man-in-the-middle the communication without you knowing it. Disabling
58verification makes the communication insecure. Just having encryption on a
59transfer is not enough as you cannot be sure that you are communicating with
60the correct end-point.
61
62When libcurl uses secure protocols it trusts responses and allows for example
63HSTS and Alt-Svc information to be stored and used subsequently. Disabling
64certificate verification can make libcurl trust and use such information from
65malicious servers.
66
67# DEFAULT
68
691 - enabled
70
71# PROTOCOLS
72
73All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.
74
75# EXAMPLE
76
77~~~c
78int main(void)
79{
80  CURL *curl = curl_easy_init();
81  if(curl) {
82    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
83
84    /* Set the default value: strict certificate check please */
85    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1L);
86
87    curl_easy_perform(curl);
88  }
89}
90~~~
91
92# AVAILABILITY
93
94If built TLS enabled.
95
96# RETURN VALUE
97
98Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
99