CURLOPT_SSL_VERIFYHOST(3)

1CURLOPT_SSL_VERIFYHOST(3)  curl_easy_setopt options  CURLOPT_SSL_VERIFYHOST(3)
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NAME

6       CURLOPT_SSL_VERIFYHOST - verify the certificate's name against host
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SYNOPSIS

9       #include <curl/curl.h>
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11       CURLcode  curl_easy_setopt(CURL  *handle,  CURLOPT_SSL_VERIFYHOST, long
12       verify);
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DESCRIPTION

15       Pass a long as parameter specifying what to verify.
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17       This option determines whether libcurl verifies that the server cert is
18       for the server it is known as.
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20       When  negotiating  TLS and SSL connections, the server sends a certifi‐
21       cate indicating its identity.
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23       When CURLOPT_SSL_VERIFYHOST(3) is 2,  that  certificate  must  indicate
24       that  the  server  is  the server to which you meant to connect, or the
25       connection fails. Simply put, it means it has to have the same name  in
26       the certificate as is in the URL you operate against.
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28       Curl  considers  the server the intended one when the Common Name field
29       or a Subject Alternate Name field in the certificate matches  the  host
30       name in the URL to which you told Curl to connect.
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32       If verify value is set to 1:
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34       In  7.28.0  and  earlier:  treated as a debug option of some sorts, not
35       supported anymore due to frequently leading to programmer mistakes.
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37       From 7.28.1 to 7.65.3: setting it to 1 made  curl_easy_setopt()  return
38       an error and leaving the flag untouched.
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40       From 7.66.0: treats 1 and 2 the same.
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42       When  the  verify value is 0, the connection succeeds regardless of the
43       names in the certificate. Use that ability with caution!
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45       The default value for this option is 2.
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47       This option controls checking the server's certificate's claimed  iden‐
48       tity.   The  server  could  be  lying.   To  control  lying,  see  CUR‐
49       LOPT_SSL_VERIFYPEER(3).
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LIMITATIONS

52       Secure Transport: If verify value is 0, then SNI is also disabled.  SNI
53       is  a  TLS  extension that sends the hostname to the server. The server
54       may use that information to do such things as sending back  a  specific
55       certificate  for  the hostname, or forwarding the request to a specific
56       origin server. Some hostnames may be inaccessible if SNI is not sent.
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58       NSS: If CURLOPT_SSL_VERIFYPEER(3) is zero, CURLOPT_SSL_VERIFYHOST(3) is
59       also set to zero and cannot be overridden.
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DEFAULT

62       2
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PROTOCOLS

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

68       CURL *curl = curl_easy_init();
69       if(curl) {
70         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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72         /* Set the default value: strict name check please */
73         curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L);
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75         curl_easy_perform(curl);
76       }
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AVAILABILITY

79       If built TLS enabled.
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RETURN VALUE

82       Returns CURLE_OK if TLS is supported, and CURLE_UNKNOWN_OPTION if not.
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84       If 1 is set as argument, CURLE_BAD_FUNCTION_ARGUMENT is returned.
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