1 /*
2  *  OpenVPN -- An application to securely tunnel IP networks
3  *             over a single TCP/UDP port, with support for SSL/TLS-based
4  *             session authentication and key exchange,
5  *             packet encryption, packet authentication, and
6  *             packet compression.
7  *
8  *  Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
9  *  Copyright (C) 2010-2018 Fox Crypto B.V. <openvpn@fox-it.com>
10  *
11  *  This program is free software; you can redistribute it and/or modify
12  *  it under the terms of the GNU General Public License version 2
13  *  as published by the Free Software Foundation.
14  *
15  *  This program is distributed in the hope that it will be useful,
16  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
17  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18  *  GNU General Public License for more details.
19  *
20  *  You should have received a copy of the GNU General Public License along
21  *  with this program; if not, write to the Free Software Foundation, Inc.,
22  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
23  */
24 
25 /**
26  * @file Control Channel Verification Module OpenSSL backend
27  */
28 
29 
30 #ifndef SSL_VERIFY_OPENSSL_H_
31 #define SSL_VERIFY_OPENSSL_H_
32 
33 #include <openssl/x509.h>
34 
35 #ifndef __OPENVPN_X509_CERT_T_DECLARED
36 #define __OPENVPN_X509_CERT_T_DECLARED
37 typedef X509 openvpn_x509_cert_t;
38 #endif
39 
40 /** @name Function for authenticating a new connection from a remote OpenVPN peer
41  *  @{ */
42 
43 /**
44  * Verify that the remote OpenVPN peer's certificate allows setting up a
45  * VPN tunnel.
46  * @ingroup control_tls
47  *
48  * This callback function is called every time a new TLS session is being
49  * setup to determine whether the remote OpenVPN peer's certificate is
50  * allowed to connect. It is called for once for every certificate in the chain.
51  * The callback functionality is configured in the \c init_ssl() function, which
52  * calls the OpenSSL library's \c SSL_CTX_set_verify() function with \c
53  * verify_callback() as its callback argument.
54  *
55  * It checks preverify_ok, and registers the certificate hash. If these steps
56  * succeed, it calls the \c verify_cert() function, which performs
57  * OpenVPN-specific verification.
58  *
59  * @param preverify_ok - Whether the remote OpenVPN peer's certificate
60  *                       past verification.  A value of 1 means it
61  *                       verified successfully, 0 means it failed.
62  * @param ctx          - The complete context used by the OpenSSL library
63  *                       to verify the certificate chain.
64  *
65  * @return The return value indicates whether the supplied certificate is
66  *     allowed to set up a VPN tunnel.  The following values can be
67  *     returned:
68  *      - \c 0: failure, this certificate is not allowed to connect.
69  *      - \c 1: success, this certificate is allowed to connect.
70  */
71 int verify_callback(int preverify_ok, X509_STORE_CTX *ctx);
72 
73 /** @} name Function for authenticating a new connection from a remote OpenVPN peer */
74 
75 #endif /* SSL_VERIFY_OPENSSL_H_ */
76