1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.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) 15Protocol: 16 - TLS 17TLS-backend: 18 - All 19--- 20 21# NAME 22 23CURLOPT_DOH_SSL_VERIFYPEER - verify the DoH SSL certificate 24 25# SYNOPSIS 26 27~~~c 28#include <curl/curl.h> 29 30CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DOH_SSL_VERIFYPEER, 31 long verify); 32~~~ 33 34# DESCRIPTION 35 36Pass a long as parameter set to 1L to enable or 0L to disable. 37 38This option tells curl to verify the authenticity of the DoH (DNS-over-HTTPS) 39server's certificate. A value of 1 means curl verifies; 0 (zero) means it 40does not. 41 42This option is the DoH equivalent of CURLOPT_SSL_VERIFYPEER(3) and 43only affects requests to the DoH server. 44 45When negotiating a TLS or SSL connection, the server sends a certificate 46indicating its identity. Curl verifies whether the certificate is authentic, 47i.e. that you can trust that the server is who the certificate says it is. 48This trust is based on a chain of digital signatures, rooted in certification 49authority (CA) certificates you supply. curl uses a default bundle of CA 50certificates (the path for that is determined at build time) and you can 51specify alternate certificates with the CURLOPT_CAINFO(3) option or the 52CURLOPT_CAPATH(3) option. 53 54When CURLOPT_DOH_SSL_VERIFYPEER(3) is enabled, and the verification fails to 55prove that the certificate is authentic, the connection fails. When the option 56is zero, the peer certificate verification succeeds regardless. 57 58Authenticating the certificate is not enough to be sure about the server. You 59typically also want to ensure that the server is the server you mean to be 60talking to. Use CURLOPT_DOH_SSL_VERIFYHOST(3) for that. The check that the 61hostname in the certificate is valid for the hostname you are connecting to 62is done independently of the CURLOPT_DOH_SSL_VERIFYPEER(3) option. 63 64WARNING: disabling verification of the certificate allows bad guys to 65man-in-the-middle the communication without you knowing it. Disabling 66verification makes the communication insecure. Just having encryption on a 67transfer is not enough as you cannot be sure that you are communicating with 68the correct end-point. 69 70# DEFAULT 71 721 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