1---
2c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
3SPDX-License-Identifier: curl
4Title: CURLOPT_DOH_SSL_VERIFYPEER
5Section: 3
6Source: libcurl
7See-also:
8  - CURLOPT_CAINFO (3)
9  - CURLOPT_CAPATH (3)
10  - CURLOPT_DOH_SSL_VERIFYHOST (3)
11  - CURLOPT_PROXY_SSL_VERIFYHOST (3)
12  - CURLOPT_PROXY_SSL_VERIFYPEER (3)
13  - CURLOPT_SSL_VERIFYHOST (3)
14  - CURLOPT_SSL_VERIFYPEER (3)
15---
16
17# NAME
18
19CURLOPT_DOH_SSL_VERIFYPEER - verify the DoH SSL certificate
20
21# SYNOPSIS
22
23~~~c
24#include <curl/curl.h>
25
26CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DOH_SSL_VERIFYPEER,
27                          long verify);
28~~~
29
30# DESCRIPTION
31
32Pass a long as parameter set to 1L to enable or 0L to disable.
33
34This option tells curl to verify the authenticity of the DoH (DNS-over-HTTPS)
35server's certificate. A value of 1 means curl verifies; 0 (zero) means it
36does not.
37
38This option is the DoH equivalent of CURLOPT_SSL_VERIFYPEER(3) and
39only affects requests to the DoH server.
40
41When negotiating a TLS or SSL connection, the server sends a certificate
42indicating its identity. Curl verifies whether the certificate is authentic,
43i.e. that you can trust that the server is who the certificate says it is.
44This trust is based on a chain of digital signatures, rooted in certification
45authority (CA) certificates you supply. curl uses a default bundle of CA
46certificates (the path for that is determined at build time) and you can
47specify alternate certificates with the CURLOPT_CAINFO(3) option or the
48CURLOPT_CAPATH(3) option.
49
50When CURLOPT_DOH_SSL_VERIFYPEER(3) is enabled, and the verification fails to
51prove that the certificate is authentic, the connection fails. When the option
52is zero, the peer certificate verification succeeds regardless.
53
54Authenticating the certificate is not enough to be sure about the server. You
55typically also want to ensure that the server is the server you mean to be
56talking to. Use CURLOPT_DOH_SSL_VERIFYHOST(3) for that. The check that the
57hostname in the certificate is valid for the hostname you are connecting to
58is done independently of the CURLOPT_DOH_SSL_VERIFYPEER(3) option.
59
60WARNING: disabling verification of the certificate allows bad guys to
61man-in-the-middle the communication without you knowing it. Disabling
62verification makes the communication insecure. Just having encryption on a
63transfer is not enough as you cannot be sure that you are communicating with
64the correct end-point.
65
66# DEFAULT
67
681
69
70# PROTOCOLS
71
72DoH
73
74# EXAMPLE
75
76~~~c
77int main(void)
78{
79  CURL *curl = curl_easy_init();
80  if(curl) {
81    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
82
83    curl_easy_setopt(curl, CURLOPT_DOH_URL,
84                     "https://cloudflare-dns.com/dns-query");
85
86    /* Disable certificate verification of the DoH server */
87    curl_easy_setopt(curl, CURLOPT_DOH_SSL_VERIFYPEER, 0L);
88
89    curl_easy_perform(curl);
90  }
91}
92~~~
93
94# AVAILABILITY
95
96Added in 7.76.0
97
98If built TLS enabled.
99
100# RETURN VALUE
101
102Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
103