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f25124338c
It's mostly a filler word. I've read through each use of it in the code base and did minor rephrasings when "simply" carried some meaning. The overwhelming majority of cases, removing it improved the text significantly. Inspired by #20793. Closes #20822
118 lines
3.4 KiB
Markdown
118 lines
3.4 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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- CURLOPT_PROXY_SSL_VERIFYHOST (3)
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- CURLOPT_DOH_SSL_VERIFYHOST (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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Added-in: 7.8.1
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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 set to 2L to make libcurl verify the host in the server's TLS
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certificate.
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When negotiating a TLS connection, the server sends a certificate indicating
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its identity.
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When CURLOPT_SSL_VERIFYHOST(3) is set to 1 or 2, the server certificate must
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indicate that it was made for the hostname or address curl connects to, or the
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connection fails. The certificate has to have the same name as is used in the
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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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When the *verify* value is 0, the connection succeeds regardless of the names
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in the certificate. Use that ability with caution.
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This option controls checking the server's certificate's claimed identity. The
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separate CURLOPT_SSL_VERIFYPEER(3) options enables/disables verification that
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the certificate is signed by a trusted Certificate Authority.
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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. Having encryption on a transfer
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is not enough as you cannot be sure that you are communicating with the
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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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# MATCHING
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A certificate can have the name as a wildcard. The only asterisk (`*`) must
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then be the left-most character and it must be followed by a period. The
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wildcard must further contain more than one period as it cannot be set for a
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top-level domain.
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A certificate can be set for a numerical IP address (IPv4 or IPv6), but then
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it should be a Subject Alternate Name kind and its type should correctly
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identify the field as an IP address.
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# DEFAULT
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2
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# %PROTOCOLS%
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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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# HISTORY
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In 7.28.0 and earlier: the value 1 was treated as a debug option of some
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sorts, not supported 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: libcurl treats 1 and 2 to this option the same.
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# RETURN VALUE
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curl_easy_setopt(3) returns a CURLcode indicating success or error.
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CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
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libcurl-errors(3).
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