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e3fe020089
Remove the PROTOCOLS section from the source files completely and instead generate them based on the header data in the curldown files. It also generates TLS backend information for options marked for TLS as protocol. Closes #13175
115 lines
3.2 KiB
Markdown
115 lines
3.2 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_SSL_VERIFYHOST
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_CAINFO (3)
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- CURLOPT_PINNEDPUBLICKEY (3)
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- CURLOPT_SSL_VERIFYPEER (3)
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Protocol:
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- TLS
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TLS-backend:
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- All
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---
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# NAME
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CURLOPT_SSL_VERIFYHOST - verify the certificate's name against host
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_VERIFYHOST, long verify);
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~~~
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# DESCRIPTION
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Pass a long as parameter specifying what to *verify*.
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This option determines whether libcurl verifies that the server cert is for
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the server it is known as.
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When negotiating TLS and SSL connections, the server sends a certificate
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indicating its identity.
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When CURLOPT_SSL_VERIFYHOST(3) is 2, that certificate must indicate that
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the server is the server to which you meant to connect, or the connection
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fails. Simply put, it means it has to have the same name in the certificate as
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is in the URL you operate against.
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Curl considers the server the intended one when the Common Name field or a
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Subject Alternate Name field in the certificate matches the hostname in the
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URL to which you told Curl to connect.
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If *verify* value is set to 1:
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In 7.28.0 and earlier: treated as a debug option of some sorts, not supported
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anymore due to frequently leading to programmer mistakes.
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From 7.28.1 to 7.65.3: setting it to 1 made curl_easy_setopt(3) return
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an error and leaving the flag untouched.
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From 7.66.0: treats 1 and 2 the same.
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When the *verify* value is 0, the connection succeeds regardless of the
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names in the certificate. Use that ability with caution!
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The default value for this option is 2.
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This option controls checking the server's certificate's claimed identity.
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The server could be lying. To control lying, see CURLOPT_SSL_VERIFYPEER(3).
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WARNING: disabling verification of the certificate allows bad guys to
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man-in-the-middle the communication without you knowing it. Disabling
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verification makes the communication insecure. Just having encryption on a
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transfer is not enough as you cannot be sure that you are communicating with
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the correct end-point.
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When libcurl uses secure protocols it trusts responses and allows for example
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HSTS and Alt-Svc information to be stored and used subsequently. Disabling
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certificate verification can make libcurl trust and use such information from
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malicious servers.
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# LIMITATIONS
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Secure Transport: If *verify* value is 0, then SNI is also disabled. SNI is
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a TLS extension that sends the hostname to the server. The server may use that
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information to do such things as sending back a specific certificate for the
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hostname, or forwarding the request to a specific origin server. Some hostnames
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may be inaccessible if SNI is not sent.
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# DEFAULT
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2
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
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/* Set the default value: strict name check please */
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curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L);
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curl_easy_perform(curl);
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}
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}
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~~~
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# AVAILABILITY
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If built TLS enabled.
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# RETURN VALUE
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Returns CURLE_OK if TLS is supported, and CURLE_UNKNOWN_OPTION if not.
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If 1 is set as argument, *CURLE_BAD_FUNCTION_ARGUMENT* is returned.
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