169 lines
6.4 KiB
Groff
169 lines
6.4 KiB
Groff
|
.\" **************************************************************************
|
||
|
|
.\" * _ _ ____ _
|
||
|
|
.\" * Project ___| | | | _ \| |
|
||
|
|
.\" * / __| | | | |_) | |
|
||
|
|
.\" * | (__| |_| | _ <| |___
|
||
|
|
.\" * \___|\___/|_| \_\_____|
|
||
|
|
.\" *
|
||
|
|
.\" * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
|
||
|
|
.\" *
|
||
|
|
.\" * This software is licensed as described in the file COPYING, which
|
||
|
|
.\" * you should have received as part of this distribution. The terms
|
||
|
|
.\" * are also available at https://curl.se/docs/copyright.html.
|
||
|
|
.\" *
|
||
|
|
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
|
||
|
|
.\" * copies of the Software, and permit persons to whom the Software is
|
||
|
|
.\" * furnished to do so, under the terms of the COPYING file.
|
||
|
|
.\" *
|
||
|
|
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
|
||
|
|
.\" * KIND, either express or implied.
|
||
|
|
.\" *
|
||
|
|
.\" * SPDX-License-Identifier: curl
|
||
|
|
.\" *
|
||
|
|
.\" **************************************************************************
|
||
|
|
.\"
|
||
|
|
.TH CURLOPT_SSL_CTX_FUNCTION 3 "19 Jun 2014" libcurl libcurl
|
||
|
|
.SH NAME
|
||
|
|
CURLOPT_SSL_CTX_FUNCTION \- SSL context callback for OpenSSL, wolfSSL or mbedTLS
|
||
|
|
.SH SYNOPSIS
|
||
|
|
.nf
|
||
|
|
#include <curl/curl.h>
|
||
|
|
|
||
|
|
CURLcode ssl_ctx_callback(CURL *curl, void *ssl_ctx, void *clientp);
|
||
|
|
|
||
|
|
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_FUNCTION,
|
||
|
|
ssl_ctx_callback);
|
||
|
|
.SH DESCRIPTION
|
||
|
|
This option only works for libcurl powered by OpenSSL, wolfSSL, mbedTLS or
|
||
|
|
BearSSL. If libcurl was built against another SSL library this functionality
|
||
|
|
is absent.
|
||
|
|
|
||
|
|
Pass a pointer to your callback function, which should match the prototype
|
||
|
|
shown above.
|
||
|
|
|
||
|
|
This callback function gets called by libcurl just before the initialization
|
||
|
|
of an SSL connection after having processed all other SSL related options to
|
||
|
|
give a last chance to an application to modify the behavior of the SSL
|
||
|
|
initialization. The \fIssl_ctx\fP parameter is actually a pointer to the SSL
|
||
|
|
library's \fISSL_CTX\fP for OpenSSL or wolfSSL, a pointer to
|
||
|
|
\fImbedtls_ssl_config\fP for mbedTLS or a pointer to
|
||
|
|
\fIbr_ssl_client_context\fP for BearSSL. If an error is returned from the
|
||
|
|
callback no attempt to establish a connection is made and the perform
|
||
|
|
operation returns the callback's error code. Set the \fIclientp\fP argument
|
||
|
|
with the \fICURLOPT_SSL_CTX_DATA(3)\fP option.
|
||
|
|
|
||
|
|
This function gets called on all new connections made to a server, during the
|
||
|
|
SSL negotiation. The \fIssl_ctx\fP points to a newly initialized object each
|
||
|
|
time, but note the pointer may be the same as from a prior call.
|
||
|
|
|
||
|
|
To use this properly, a non-trivial amount of knowledge of your SSL library is
|
||
|
|
necessary. For example, you can use this function to call library-specific
|
||
|
|
callbacks to add additional validation code for certificates, and even to
|
||
|
|
change the actual URI of an HTTPS request.
|
||
|
|
|
||
|
|
For OpenSSL, asynchronous certificate verification via
|
||
|
|
\fISSL_set_retry_verify\fP is supported. (Added in 8.3.0)
|
||
|
|
|
||
|
|
WARNING: The \fICURLOPT_SSL_CTX_FUNCTION(3)\fP callback allows the application
|
||
|
|
to reach in and modify SSL details in the connection without libcurl itself
|
||
|
|
knowing anything about it, which then subsequently can lead to libcurl
|
||
|
|
unknowingly reusing SSL connections with different properties. To remedy this
|
||
|
|
you may set \fICURLOPT_FORBID_REUSE(3)\fP from the callback function.
|
||
|
|
|
||
|
|
WARNING: If you are using DNS-over-HTTPS (DoH) via \fICURLOPT_DOH_URL(3)\fP
|
||
|
|
then this callback is also called for those transfers and the curl handle is
|
||
|
|
set to an internal handle. \fBThis behavior is subject to change.\fP We
|
||
|
|
recommend before performing your transfer set \fICURLOPT_PRIVATE(3)\fP on your
|
||
|
|
curl handle so you can identify it in the context callback. If you have a
|
||
|
|
reason to modify DoH SSL context please let us know on the curl-library
|
||
|
|
mailing list because we are considering removing this capability.
|
||
|
|
.SH DEFAULT
|
||
|
|
NULL
|
||
|
|
.SH PROTOCOLS
|
||
|
|
All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.
|
||
|
|
.SH EXAMPLE
|
||
|
|
.nf
|
||
|
|
/* OpenSSL specific */
|
||
|
|
|
||
|
|
#include <openssl/ssl.h>
|
||
|
|
#include <curl/curl.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
|
||
|
|
static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
|
||
|
|
{
|
||
|
|
X509_STORE *store;
|
||
|
|
X509 *cert = NULL;
|
||
|
|
BIO *bio;
|
||
|
|
char *mypem = parm;
|
||
|
|
/* get a BIO */
|
||
|
|
bio = BIO_new_mem_buf(mypem, -1);
|
||
|
|
/* use it to read the PEM formatted certificate from memory into an
|
||
|
|
* X509 structure that SSL can use
|
||
|
|
*/
|
||
|
|
PEM_read_bio_X509(bio, &cert, 0, NULL);
|
||
|
|
if(cert == NULL)
|
||
|
|
printf("PEM_read_bio_X509 failed...\\n");
|
||
|
|
|
||
|
|
/* get a pointer to the X509 certificate store (which may be empty) */
|
||
|
|
store = SSL_CTX_get_cert_store((SSL_CTX *)sslctx);
|
||
|
|
|
||
|
|
/* add our certificate to this store */
|
||
|
|
if(X509_STORE_add_cert(store, cert) == 0)
|
||
|
|
printf("error adding certificate\\n");
|
||
|
|
|
||
|
|
/* decrease reference counts */
|
||
|
|
X509_free(cert);
|
||
|
|
BIO_free(bio);
|
||
|
|
|
||
|
|
/* all set to go */
|
||
|
|
return CURLE_OK;
|
||
|
|
}
|
||
|
|
|
||
|
|
int main(void)
|
||
|
|
{
|
||
|
|
CURL * ch;
|
||
|
|
CURLcode rv;
|
||
|
|
char *mypem = /* example CA cert PEM - shortened */
|
||
|
|
"-----BEGIN CERTIFICATE-----\\n"
|
||
|
|
"MIIHPTCCBSWgAwIBAgIBADANBgkqhkiG9w0BAQQFADB5MRAwDgYDVQQKEwdSb290\\n"
|
||
|
|
"IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNB\\n"
|
||
|
|
"IENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRA\\n"
|
||
|
|
"Y2FjZXJ0Lm9yZzAeFw0wMzAzMzAxMjI5NDlaFw0zMzAzMjkxMjI5NDlaMHkxEDAO\\n"
|
||
|
|
"GCSNe9FINSkYQKyTYOGWhlC0elnYjyELn8+CkcY7v2vcB5G5l1YjqrZslMZIBjzk\\n"
|
||
|
|
"zk6q5PYvCdxTby78dOs6Y5nCpqyJvKeyRKANihDjbPIky/qbn3BHLt4Ui9SyIAmW\\n"
|
||
|
|
"omTxJBzcoTWcFbLUvFUufQb1nA5V9FrWk9p2rSVzTMVD\\n"
|
||
|
|
"-----END CERTIFICATE-----\\n";
|
||
|
|
|
||
|
|
curl_global_init(CURL_GLOBAL_ALL);
|
||
|
|
ch = curl_easy_init();
|
||
|
|
|
||
|
|
curl_easy_setopt(ch, CURLOPT_SSLCERTTYPE, "PEM");
|
||
|
|
curl_easy_setopt(ch, CURLOPT_SSL_VERIFYPEER, 1L);
|
||
|
|
curl_easy_setopt(ch, CURLOPT_URL, "https://www.example.com/");
|
||
|
|
|
||
|
|
curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
|
||
|
|
curl_easy_setopt(ch, CURLOPT_SSL_CTX_DATA, mypem);
|
||
|
|
rv = curl_easy_perform(ch);
|
||
|
|
if(!rv)
|
||
|
|
printf("*** transfer succeeded ***\\n");
|
||
|
|
else
|
||
|
|
printf("*** transfer failed ***\\n");
|
||
|
|
|
||
|
|
curl_easy_cleanup(ch);
|
||
|
|
curl_global_cleanup();
|
||
|
|
return rv;
|
||
|
|
}
|
||
|
|
.fi
|
||
|
|
.SH AVAILABILITY
|
||
|
|
Added in 7.11.0 for OpenSSL, in 7.42.0 for wolfSSL, in 7.54.0 for mbedTLS,
|
||
|
|
in 7.83.0 in BearSSL. Other SSL backends are not supported.
|
||
|
|
.SH RETURN VALUE
|
||
|
|
CURLE_OK if supported; or an error such as:
|
||
|
|
|
||
|
|
CURLE_NOT_BUILT_IN - Not supported by the SSL backend
|
||
|
|
|
||
|
|
CURLE_UNKNOWN_OPTION
|
||
|
|
.SH "SEE ALSO"
|
||
|
|
.BR CURLOPT_SSL_CTX_DATA (3),
|
||
|
|
.BR CURLOPT_SSL_VERIFYPEER (3)
|