/*
  *  OpenVPN -- An application to securely tunnel IP networks
  *             over a single TCP/UDP port, with support for SSL/TLS-based
  *             session authentication and key exchange,
  *             packet encryption, packet authentication, and
  *             packet compression.
  *

  *  Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
  *  Copyright (C) 2010-2018 Fox Crypto B.V. <openvpn@fox-it.com>

  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2
  *  as published by the Free Software Foundation.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *

  *  You should have received a copy of the GNU General Public License along
  *  with this program; if not, write to the Free Software Foundation, Inc.,
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

  */
 
 /**
  * @file Control Channel Verification Module library-specific backend interface
  */
 
 #ifndef SSL_VERIFY_BACKEND_H_
 #define SSL_VERIFY_BACKEND_H_
 

 /**
  * Result of verification function
  */

 typedef enum { SUCCESS = 0, FAILURE = 1 } result_t;

 /*
  * Backend support functions.
  *
  * The following functions are needed by the backend, but defined in the main
  * file.
  */
 
 /*

  * Verify certificate for the given session. Performs OpenVPN-specific
  * verification.
  *
  * This function must be called for every certificate in the certificate
  * chain during the certificate verification stage of the handshake.
  *

  * @param session       TLS Session associated with this tunnel
  * @param cert          Certificate to process
  * @param cert_depth    Depth of the current certificate

  *

  * @return              \c SUCCESS if verification was successful, \c FAILURE on failure.

  */

 result_t verify_cert(struct tls_session *session, openvpn_x509_cert_t *cert, int cert_depth);

 
 /*

  * Remember the given certificate hash, allowing the certificate chain to be
  * locked between sessions.
  *
  * Must be called for every certificate in the verification chain, whether it
  * is valid or not.
  *

  * @param session       TLS Session associated with this tunnel
  * @param cert_depth    Depth of the current certificate
  * @param cert_hash     Hash of the current certificate

  */

 void cert_hash_remember(struct tls_session *session, const int cert_depth,
                         const struct buffer *cert_hash);

 /*
  * Library-specific functions.
  *
  * The following functions must be implemented on a library-specific basis.
  */
 
 /*

  * Retrieve certificate's subject name.

  *

  * @param cert          Certificate to retrieve the subject from.
  * @param gc            Garbage collection arena to use when allocating string.

  *

  * @return              a string containing the subject

  */

 char *x509_get_subject(openvpn_x509_cert_t *cert, struct gc_arena *gc);

 /**
  * Retrieve the certificate's SHA1 fingerprint.
  *

  * @param cert          Certificate to retrieve the fingerprint from.
  * @param gc            Garbage collection arena to use when allocating string.

  *

  * @return              a string containing the certificate fingerprint

  */

 struct buffer x509_get_sha1_fingerprint(openvpn_x509_cert_t *cert,
                                         struct gc_arena *gc);

 
 /**
  * Retrieve the certificate's SHA256 fingerprint.

  *

  * @param cert          Certificate to retrieve the fingerprint from.
  * @param gc            Garbage collection arena to use when allocating string.

  *

  * @return              a string containing the certificate fingerprint

  */

 struct buffer x509_get_sha256_fingerprint(openvpn_x509_cert_t *cert,
                                           struct gc_arena *gc);

 /*
  * Retrieve the certificate's username from the specified field.
  *
  * If the field is prepended with ext: and ENABLE_X509ALTUSERNAME is enabled,
  * it will be loaded from an X.509 extension
  *

  * @param cn                    Buffer to return the common name in.
  * @param cn_len                Length of the cn buffer.
  * @param x509_username_field   Name of the field to load from
  * @param cert                  Certificate to retrieve the common name from.

  *

  * @return              \c FAILURE, \c or SUCCESS

  */

 result_t backend_x509_get_username(char *common_name, int cn_len,
                                    char *x509_username_field, openvpn_x509_cert_t *peer_cert);

 #ifdef ENABLE_X509ALTUSERNAME
 /**
  * Return true iff the supplied extension field is supported by the
  * --x509-username-field option.
  */
 bool x509_username_field_ext_supported(const char *extname);
 #endif
 

 /*

  * Return the certificate's serial number in decimal string representation.

  *
  * The serial number is returned as a string, since it might be a bignum.
  *

  * @param cert          Certificate to retrieve the serial number from.
  * @param gc            Garbage collection arena to use when allocating string.

  *

  * @return              String representation of the certificate's serial number
  *                      in decimal notation, or NULL on error.

  */

 char *backend_x509_get_serial(openvpn_x509_cert_t *cert, struct gc_arena *gc);

 
 /*

  * Return the certificate's serial number in hex string representation.
  *
  * The serial number is returned as a string, since it might be a bignum.
  *

  * @param cert          Certificate to retrieve the serial number from.
  * @param gc            Garbage collection arena to use when allocating string.

  *

  * @return              String representation of the certificate's serial number
  *                      in hex notation, or NULL on error.

  */

 char *backend_x509_get_serial_hex(openvpn_x509_cert_t *cert,
                                   struct gc_arena *gc);

 
 /*

  * Save X509 fields to environment, using the naming convention:
  *
  * X509_{cert_depth}_{name}={value}

  *

  * @param es            Environment set to save variables in
  * @param cert_depth    Depth of the certificate
  * @param cert          Certificate to set the environment for

  */

 void x509_setenv(struct env_set *es, int cert_depth, openvpn_x509_cert_t *cert);

 
 /*
  * Start tracking the given attribute.
  *
  * The tracked attributes are stored in ll_head.
  *

  * @param ll_head       The x509_track to store tracked atttributes in
  * @param name          Name of the attribute to track
  * @param msglevel      Message level for errors
  * @param gc            Garbage collection arena for temp data

  *
  */

 void x509_track_add(const struct x509_track **ll_head, const char *name,
                     int msglevel, struct gc_arena *gc);

 
 /*
  * Save X509 fields to environment, using the naming convention:
  *

  *  X509_{cert_depth}_{name}={value}
  *
  * This function differs from setenv_x509 below in the following ways:

  *

  * (1) Only explicitly named attributes in xt are saved, per usage
  *     of --x509-track program options.
  * (2) Only the level 0 cert info is saved unless the XT_FULL_CHAIN
  *     flag is set in xt->flags (corresponds with prepending a '+'
  *     to the name when specified by --x509-track program option).
  * (3) This function supports both X509 subject name fields as
  *     well as X509 V3 extensions.
  *
  * @param xt

  * @param es            Environment set to save variables in
  * @param cert_depth    Depth of the certificate
  * @param cert          Certificate to set the environment for

  */

 void x509_setenv_track(const struct x509_track *xt, struct env_set *es,
                        const int depth, openvpn_x509_cert_t *x509);

 /*
  * Check X.509 Netscape certificate type field, if available.
  *

  * @param cert          Certificate to check.
  * @param usage         One of \c NS_CERT_CHECK_CLIENT, \c NS_CERT_CHECK_SERVER,
  *                      or \c NS_CERT_CHECK_NONE.

  *

  * @return              \c SUCCESS if NS_CERT_CHECK_NONE or if the certificate has
  *                      the expected bit set. \c FAILURE if the certificate does
  *                      not have NS cert type verification or the wrong bit set.

  */

 result_t x509_verify_ns_cert_type(openvpn_x509_cert_t *cert, const int usage);

 /*
  * Verify X.509 key usage extension field.
  *

  * @param cert          Certificate to check.
  * @param expected_ku   Array of valid key usage values
  * @param expected_len  Length of the key usage array

  *

  * @return              \c SUCCESS if one of the key usage values matches, \c FAILURE
  *                      if key usage is not enabled, or the values do not match.

  */

 result_t x509_verify_cert_ku(openvpn_x509_cert_t *x509, const unsigned *const expected_ku,
                              int expected_len);

 /*
  * Verify X.509 extended key usage extension field.
  *

  * @param cert          Certificate to check.
  * @param expected_oid  String representation of the expected Object ID. May be
  *                      either the string representation of the numeric OID
  *                      (e.g. \c "1.2.3.4", or the descriptive string matching
  *                      the OID.

  *

  * @return              \c SUCCESS if one of the expected OID matches one of the
  *                      extended key usage fields, \c FAILURE if extended key
  *                      usage is not enabled, or the values do not match.

  */

 result_t x509_verify_cert_eku(openvpn_x509_cert_t *x509, const char *const expected_oid);

 /*
  * Store the given certificate in pem format in a temporary file in tmp_dir
  *

  * @param cert          Certificate to store
  * @param tmp_dir       Temporary directory to store the directory
  * @param gc            gc_arena to store temporary objects in

  *
  *

  */

 result_t x509_write_pem(FILE *peercert_file, openvpn_x509_cert_t *peercert);

 /**
  * Return true iff a CRL is configured, but is not loaded.  This can be caused
  * by e.g. a CRL parsing error, a missing CRL file or CRL file permission
  * errors.  (These conditions are checked upon startup, but the CRL might be
  * updated and reloaded during runtime.)

  */

 bool tls_verify_crl_missing(const struct tls_options *opt);

 #endif /* SSL_VERIFY_BACKEND_H_ */