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 mbed TLS backend
27  */
28 
29 #ifndef SSL_VERIFY_MBEDTLS_H_
30 #define SSL_VERIFY_MBEDTLS_H_
31 
32 #include "syshead.h"
33 #include <mbedtls/x509_crt.h>
34 
35 #ifndef __OPENVPN_X509_CERT_T_DECLARED
36 #define __OPENVPN_X509_CERT_T_DECLARED
37 typedef mbedtls_x509_crt 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 when a new TLS session is being setup to
49  * determine whether the remote OpenVPN peer's certificate is allowed to
50  * connect. It is called for once for every certificate in the chain. The
51  * callback functionality is configured in the \c key_state_ssl_init() function,
52  * which calls the mbed TLS library's \c mbedtls_ssl_conf_verify() function with
53  * \c verify_callback() as its callback argument.
54  *
55  * It checks *flags and registers the certificate hash. If these steps succeed,
56  * it calls the \c verify_cert() function, which performs OpenVPN-specific
57  * verification.
58  *
59  * @param session_obj  - The OpenVPN \c tls_session associated with this object,
60  *                       as set during SSL session setup.
61  * @param cert         - The certificate used by mbed TLS.
62  * @param cert_depth   - The depth of the current certificate in the chain, with
63  *                       0 being the actual certificate.
64  * @param flags        - Whether the remote OpenVPN peer's certificate
65  *                       passed verification.  A value of 0 means it
66  *                       verified successfully, any other value means it
67  *                       failed. \c verify_callback() is considered to have
68  *                       ok'ed this certificate if flags is 0 when it returns.
69  *
70  * @return The return value is 0 unless a fatal error occurred.
71  */
72 int verify_callback(void *session_obj, mbedtls_x509_crt *cert, int cert_depth,
73                     uint32_t *flags);
74 
75 /** @} name Function for authenticating a new connection from a remote OpenVPN peer */
76 
77 #endif /* SSL_VERIFY_MBEDTLS_H_ */
78