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92 lines
4.2 KiB
Groff
92 lines
4.2 KiB
Groff
.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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.\" * are also available at https://curl.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" **************************************************************************
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.\"
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.TH CURLOPT_SSL_CTX_FUNCTION 3 "19 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
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.SH NAME
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CURLOPT_SSL_CTX_FUNCTION \- SSL context callback for OpenSSL, wolfSSL or mbedTLS
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLcode ssl_ctx_callback(CURL *curl, void *ssl_ctx, void *userptr);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_FUNCTION,
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ssl_ctx_callback);
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.SH DESCRIPTION
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This option only works for libcurl powered by OpenSSL, wolfSSL or mbedTLS. If
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libcurl was built against another SSL library this functionality is absent.
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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This callback function gets called by libcurl just before the initialization
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of an SSL connection after having processed all other SSL related options to
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give a last chance to an application to modify the behavior of the SSL
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initialization. The \fIssl_ctx\fP parameter is actually a pointer to the SSL
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library's \fISSL_CTX\fP for OpenSSL or wolfSSL, and a pointer to
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\fImbedtls_ssl_config\fP for mbedTLS. If an error is returned from the
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callback no attempt to establish a connection is made and the perform
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operation will return the callback's error code. Set the \fIuserptr\fP
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argument with the \fICURLOPT_SSL_CTX_DATA(3)\fP option.
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This function will get called on all new connections made to a server, during
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the SSL negotiation. The \fIssl_ctx\fP will point to a newly initialized object
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each time, but note the pointer may be the same as from a prior call.
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To use this properly, a non-trivial amount of knowledge of your SSL library is
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necessary. For example, you can use this function to call library-specific
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callbacks to add additional validation code for certificates, and even to
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change the actual URI of an HTTPS request.
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WARNING: The \fICURLOPT_SSL_CTX_FUNCTION(3)\fP callback allows the application
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to reach in and modify SSL details in the connection without libcurl itself
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knowing anything about it, which then subsequently can lead to libcurl
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unknowingly reusing SSL connections with different properties. To remedy this
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you may set \fICURLOPT_FORBID_REUSE(3)\fP from the callback function.
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WARNING: If you are using DNS-over-HTTPS (DoH) via \fICURLOPT_DOH_URL(3)\fP
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then the CTX callback will also be called for those transfers and the curl
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handle is set to an internal handle. \fBThis behavior is subject to change.\fP
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We recommend before performing your transfer set \fICURLOPT_PRIVATE(3)\fP on
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your curl handle so you can identify it in the CTX callback. If you have a
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reason to modify DoH SSL context please let us know on the curl-library mailing
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list because we are considering removing this capability.
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.SH DEFAULT
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NULL
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.SH PROTOCOLS
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All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.
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.SH EXAMPLE
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See cacertinmem.c in docs/examples directory for usage example.
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https://curl.se/libcurl/c/cacertinmem.html
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.SH AVAILABILITY
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Added in 7.11.0 for OpenSSL, in 7.42.0 for wolfSSL and in 7.54.0 for
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mbedTLS. Other SSL backends are not supported.
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.SH RETURN VALUE
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CURLE_OK if supported; or an error such as:
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CURLE_NOT_BUILT_IN - Not supported by the SSL backend
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CURLE_UNKNOWN_OPTION
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.SH "SEE ALSO"
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.BR CURLOPT_SSL_CTX_DATA "(3), " CURLOPT_SSL_VERIFYPEER "(3), "
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