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180501cb02
Stick to "Schannel" everywhere. The configure option --with-winssl is kept to allow existing builds to work but --with-schannel is added as an alias. Closes #3504
171 lines
6.3 KiB
Groff
171 lines
6.3 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.haxx.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 CURLINFO_TLS_SSL_PTR 3 "23 Feb 2016" "libcurl 7.48.0" "curl_easy_getinfo options"
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.SH NAME
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CURLINFO_TLS_SESSION, CURLINFO_TLS_SSL_PTR \- get TLS session info
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_TLS_SSL_PTR,
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struct curl_tlssessioninfo **session);
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/* if you need compatibility with libcurl < 7.48.0 use
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CURLINFO_TLS_SESSION instead: */
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CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_TLS_SESSION,
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struct curl_tlssessioninfo **session);
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.SH DESCRIPTION
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Pass a pointer to a 'struct curl_tlssessioninfo *'. The pointer will be
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initialized to refer to a 'struct curl_tlssessioninfo *' that will contain an
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enum indicating the SSL library used for the handshake and a pointer to the
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respective internal TLS session structure of this underlying SSL library.
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This option may be useful for example to extract certificate information in a
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format convenient for further processing, such as manual validation. Refer to
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the \fBLIMITATIONS\fP section.
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.nf
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struct curl_tlssessioninfo {
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curl_sslbackend backend;
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void *internals;
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};
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.fi
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The \fIbackend\fP struct member is one of the defines in the CURLSSLBACKEND_*
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series: CURLSSLBACKEND_NONE (when built without TLS support),
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CURLSSLBACKEND_CYASSL, CURLSSLBACKEND_DARWINSSL,
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CURLSSLBACKEND_GNUTLS, CURLSSLBACKEND_GSKIT, CURLSSLBACKEND_MBEDTLS,
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CURLSSLBACKEND_NSS, CURLSSLBACKEND_OPENSSL, CURLSSLBACKEND_POLARSSL,
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CURLSSLBACKEND_SCHANNEL or CURLSSLBACKEND_MESALINK. (Note that the OpenSSL
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forks are all reported as just OpenSSL here.)
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The \fIinternals\fP struct member will point to a TLS library specific pointer
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for the active ("in use") SSL connection, with the following underlying types:
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.RS
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.IP GnuTLS
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gnutls_session_t
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.IP gskit
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gsk_handle
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.IP NSS
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PRFileDesc *
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.IP OpenSSL
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CURLINFO_TLS_SESSION: SSL_CTX *
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CURLINFO_TLS_SSL_PTR: SSL *
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.RE
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Since 7.48.0 the \fIinternals\fP member can point to these other SSL backends
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as well:
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.RS
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.IP mbedTLS
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mbedtls_ssl_context *
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.IP PolarSSL
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ssl_context *
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.IP "Secure Channel"
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CtxtHandle *
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.IP "Secure Transport (DarwinSSL)"
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SSLContext *
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.IP "WolfSSL (formerly CyaSSL)"
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SSL *
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.IP "MesaLink"
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SSL *
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.RE
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If the \fIinternals\fP pointer is NULL then either the SSL backend is not
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supported, an SSL session has not yet been established or the connection is no
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longer associated with the easy handle (eg curl_easy_perform has returned).
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.SH LIMITATIONS
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\fBThis option has some limitations that could make it unsafe when it comes to
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the manual verification of certificates.\fP
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This option only retrieves the first in-use SSL session pointer for your easy
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handle, however your easy handle may have more than one in-use SSL session if
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using FTP over SSL. That is because the FTP protocol has a control channel and
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a data channel and one or both may be over SSL. \fBCurrently there is no way to
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retrieve a second in-use SSL session associated with an easy handle.\fP
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This option has not been thoroughly tested with plaintext protocols that can be
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upgraded/downgraded to/from SSL: FTP, SMTP, POP3, IMAP when used with
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\fICURLOPT_USE_SSL(3)\fP. Though you will be able to retrieve the SSL pointer,
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it's possible that before you can do that \fBdata (including auth) may have
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already been sent over a connection after it was upgraded.\fP
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Renegotiation. If unsafe renegotiation or renegotiation in a way that the
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certificate is allowed to change is allowed by your SSL library this may occur
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and the certificate may change, and \fBdata may continue to be sent or received
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after renegotiation but before you are able to get the (possibly) changed SSL
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pointer,\fP with the (possibly) changed certificate information.
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If you are using OpenSSL or wolfSSL then \fICURLOPT_SSL_CTX_FUNCTION(3)\fP can
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be used to set a certificate verification callback in the CTX. That is safer
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than using this option to poll for certificate changes and doesn't suffer from
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any of the problems above. There is currently no way in libcurl to set a
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verification callback for the other SSL backends.
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How are you using this option? Are you affected by any of these limitations?
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Please let us know by making a comment at
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https://github.com/curl/curl/issues/685
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.SH PROTOCOLS
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All TLS-based
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.SH EXAMPLE
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.nf
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#include <curl/curl.h>
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#include <openssl/ssl.h>
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CURL *curl;
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static size_t wf(void *ptr, size_t size, size_t nmemb, void *stream)
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{
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const struct curl_tlssessioninfo *info = NULL;
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CURLcode res = curl_easy_getinfo(curl, CURLINFO_TLS_SSL_PTR, &info);
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if(info && !res) {
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if(CURLSSLBACKEND_OPENSSL == info->backend) {
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printf("OpenSSL ver. %s\\n", SSL_get_version((SSL*)info->internals));
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}
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}
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return size * nmemb;
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}
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int main(int argc, char** argv)
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{
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CURLcode res;
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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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curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, wf);
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res = curl_easy_perform(curl);
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curl_easy_cleanup(curl);
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}
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return res;
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}
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.fi
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.SH AVAILABILITY
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Added in 7.48.0.
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This option supersedes \fICURLINFO_TLS_SESSION(3)\fP which was added in 7.34.0.
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This option is exactly the same as that option except in the case of OpenSSL.
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.SH RETURN VALUE
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Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
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.SH "SEE ALSO"
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.BR curl_easy_getinfo "(3), " curl_easy_setopt "(3), "
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.BR CURLINFO_TLS_SESSION "(3), "
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