175 lines
5 KiB
Markdown
175 lines
5 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLINFO_TLS_SSL_PTR
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Section: 3
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Source: libcurl
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See-also:
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- CURLINFO_TLS_SESSION (3)
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- curl_easy_getinfo (3)
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- curl_easy_setopt (3)
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---
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# NAME
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CURLINFO_TLS_SESSION, CURLINFO_TLS_SSL_PTR - get TLS session info
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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_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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~~~
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# DESCRIPTION
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Pass a pointer to a *struct curl_tlssessioninfo **. The pointer is initialized
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to refer to a *struct curl_tlssessioninfo ** that contains an enum indicating
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the SSL library used for the handshake and a pointer to the respective
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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 **LIMITATIONS** section.
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~~~c
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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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~~~
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The *backend* 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_WOLFSSL, CURLSSLBACKEND_SECURETRANSPORT, CURLSSLBACKEND_GNUTLS,
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CURLSSLBACKEND_MBEDTLS, CURLSSLBACKEND_NSS, CURLSSLBACKEND_OPENSSL,
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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 *internals* struct member points to a TLS library specific pointer for
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the active ("in use") SSL connection, with the following underlying types:
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## GnuTLS
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**gnutls_session_t**
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## NSS
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**PRFileDesc ***
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## OpenSSL
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CURLINFO_TLS_SESSION(3): **SSL_CTX ***
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CURLINFO_TLS_SSL_PTR(3): **SSL ***
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Since 7.48.0 the *internals* member can point to these other SSL backends
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as well:
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## mbedTLS
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**mbedTLS_ssl_context ***
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## Secure Channel
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**CtxtHandle ***
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## Secure Transport
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**SSLContext ***
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## wolfSSL
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**SSL ***
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If the *internals* 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 (e.g. curl_easy_perform(3) has
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returned).
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# LIMITATIONS
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This option has some limitations that could make it unsafe when it comes to
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the manual verification of certificates.
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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. Currently there is no way to
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retrieve a second in-use SSL session associated with an easy handle.
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This option has not been thoroughly tested with clear text protocols that can
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be upgraded/downgraded to/from SSL: FTP, SMTP, POP3, IMAP when used with
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CURLOPT_USE_SSL(3). Though you can to retrieve the SSL pointer, it is possible
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that before you can do that, data (including auth) may have already been sent
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over a connection after it was upgraded.
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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 data 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, with the (possibly) changed certificate information.
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Instead of using this option to poll for certificate changes use
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CURLOPT_SSL_CTX_FUNCTION(3) to set a verification callback, if supported.
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That is safer and does not suffer from any of the problems above.
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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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# PROTOCOLS
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All TLS-based
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# EXAMPLE
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~~~c
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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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~~~
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# AVAILABILITY
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Added in 7.48.0.
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This option supersedes CURLINFO_TLS_SESSION(3) 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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# RETURN VALUE
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Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
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