NAME

       CURLOPT_SSL_VERIFYHOST - verify the certificate's name against host

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_VERIFYHOST, long verify);

DESCRIPTION

       Pass a long set to 2L to make libcurl verify the host in the server's TLS certificate.

       When negotiating a TLS connection, the server sends a certificate indicating its identity.

       When CURLOPT_SSL_VERIFYHOST(3) is set to 1 or 2, the server certificate must indicate that
       it was made for the hostname or address curl connects to, or the connection fails.  Simply
       put,  it  means  it has to have the same name in the certificate as is used in the URL you
       operate against.

       curl considers the server the intended one  when  the  Common  Name  field  or  a  Subject
       Alternate  Name field in the certificate matches the hostname in the URL to which you told
       curl to connect.

       When the verify value is 0, the  connection  succeeds  regardless  of  the  names  in  the
       certificate. Use that ability with caution,

       This  option  controls  checking the server's certificate's claimed identity. The separate
       CURLOPT_SSL_VERIFYPEER(3) options enables/disables verification that  the  certificate  is
       signed by a trusted Certificate Authority.

       WARNING:  disabling  verification  of the certificate allows bad guys to man-in-the-middle
       the communication without you knowing it. Disabling verification makes  the  communication
       insecure.  Just  having  encryption on a transfer is not enough as you cannot be sure that
       you are communicating with the correct end-point.

       When libcurl uses secure protocols it trusts responses and allows  for  example  HSTS  and
       Alt-Svc information to be stored and used subsequently. Disabling certificate verification
       can make libcurl trust and use such information from malicious servers.

MATCHING

       A certificate can have the name as a wildcard. The only asterisk  (*)  must  then  be  the
       left-most character and it must be followed by a period. The wildcard must further contain
       more than one period as it cannot be set for a top-level domain.

       A certificate can be set for a numerical IP address (IPv4 or IPv6), but then it should  be
       a  Subject  Alternate  Name kind and its type should correctly identify the field as an IP
       address.

LIMITATIONS

       Secure Transport: If verify value is 0, then SNI is also disabled. SNI is a TLS  extension
       that  sends  the  hostname  to  the server. The server may use that information to do such
       things as sending back a specific certificate for the hostname, or forwarding the  request
       to a specific origin server. Some hostnames may be inaccessible if SNI is not sent.

DEFAULT

       2

PROTOCOLS

       This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

       All TLS backends support this option.

EXAMPLE

       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

           /* Set the default value: strict name check please */
           curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L);

           curl_easy_perform(curl);
         }
       }

AVAILABILITY

       Added in curl 7.8.1

HISTORY

       In  7.28.0  and  earlier:  the  value  1  was treated as a debug option of some sorts, not
       supported anymore due to frequently leading to programmer mistakes.

       From 7.28.1 to 7.65.3: setting it to  1  made  curl_easy_setopt(3)  return  an  error  and
       leaving the flag untouched.

       From 7.66.0: libcurl treats 1 and 2 to this option the same.

RETURN VALUE

       Returns CURLE_OK if TLS is supported, and CURLE_UNKNOWN_OPTION if not.

SEE ALSO

       CURLOPT_CAINFO(3), CURLOPT_PINNEDPUBLICKEY(3), CURLOPT_SSL_VERIFYPEER(3)