Provided by: libcurl4-doc_7.88.1-8ubuntu1_all bug


       CURLOPT_SSL_VERIFYHOST - verify the certificate's name against host


       #include <curl/curl.h>

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


       Pass a long as parameter specifying what to verify.

       This  option determines whether libcurl verifies that the server cert is for the server it
       is known as.

       When negotiating TLS and SSL connections, the server sends a  certificate  indicating  its

       When CURLOPT_SSL_VERIFYHOST(3) is 2, that certificate must indicate that the server is the
       server to which you meant to connect, or the connection fails. Simply put, it means it has
       to have the same name in the certificate as is 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 host name in the URL to which you told
       Curl to connect.

       If verify value is set to 1:

       In  7.28.0 and earlier: 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() return an error and leaving
       the flag untouched.

       From 7.66.0: treats 1 and 2 the same.

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

       The default value for this option is 2.

       This option controls checking the server's certificate's  claimed  identity.   The  server
       could be lying.  To control lying, see CURLOPT_SSL_VERIFYPEER(3).

       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.


       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.

       NSS:  If  CURLOPT_SSL_VERIFYPEER(3) is zero, CURLOPT_SSL_VERIFYHOST(3) is also set to zero
       and cannot be overridden.




       All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.


       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "");

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



       If built TLS enabled.


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

       If 1 is set as argument, CURLE_BAD_FUNCTION_ARGUMENT is returned.