1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.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) 14Protocol: 15 - TLS 16TLS-backend: 17 - All 18--- 19 20# NAME 21 22CURLOPT_SSL_VERIFYPEER - verify the peer's SSL certificate 23 24# SYNOPSIS 25 26~~~c 27#include <curl/curl.h> 28 29CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_VERIFYPEER, long verify); 30~~~ 31 32# DESCRIPTION 33 34Pass a long as parameter to enable or disable. 35 36This option determines whether curl verifies the authenticity of the peer's 37certificate. A value of 1 means curl verifies; 0 (zero) means it does not. 38 39When negotiating a TLS or SSL connection, the server sends a certificate 40indicating its identity. Curl verifies whether the certificate is authentic, 41i.e. that you can trust that the server is who the certificate says it is. 42This trust is based on a chain of digital signatures, rooted in certification 43authority (CA) certificates you supply. curl uses a default bundle of CA 44certificates (the path for that is determined at build time) and you can 45specify alternate certificates with the CURLOPT_CAINFO(3) option or the 46CURLOPT_CAPATH(3) option. 47 48When CURLOPT_SSL_VERIFYPEER(3) is enabled, and the verification fails to 49prove that the certificate is signed by a CA, the connection fails. 50 51When this option is disabled (set to zero), the CA certificates are not loaded 52and the peer certificate verification is simply skipped. 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_SSL_VERIFYHOST(3) for that. The check that the host 57name in the certificate is valid for the hostname you are connecting to is 58done independently of the CURLOPT_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 66When libcurl uses secure protocols it trusts responses and allows for example 67HSTS and Alt-Svc information to be stored and used subsequently. Disabling 68certificate verification can make libcurl trust and use such information from 69malicious servers. 70 71# DEFAULT 72 731 - enabled 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