/*
 * Copyright (C) 2009 Free Software Foundation
 *
 * Author: Daiki Ueno
 *
 * This file is part of GNUTLS.
 *
 * The GNUTLS library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA
 *
 */

#include <gnutls_int.h>
#include <gnutls_errors.h>
#include <gnutls_datum.h>
#include <gnutls_algorithms.h>
#include <gnutls_handshake.h>
#include <gnutls_num.h>
#include <gnutls_constate.h>
#include <gnutls_session_pack.h>
#include <random.h>
#include <ext_session_ticket.h>

#ifdef ENABLE_SESSION_TICKET

#define KEY_NAME_SIZE SESSION_TICKET_KEY_NAME_SIZE
#define KEY_SIZE SESSION_TICKET_KEY_SIZE
#define IV_SIZE SESSION_TICKET_IV_SIZE
#define MAC_SECRET_SIZE SESSION_TICKET_MAC_SECRET_SIZE

#define MAC_SIZE 32

struct ticket
{
  opaque key_name[KEY_NAME_SIZE];
  opaque IV[IV_SIZE];
  opaque *encrypted_state;
  uint16_t encrypted_state_len;
  opaque mac[MAC_SIZE];
};

static int
digest_ticket (const gnutls_datum_t * key, struct ticket *ticket,
	       opaque * digest)
{
  digest_hd_st digest_hd;
  uint16_t length16;
  int ret;

  ret = _gnutls_hmac_init (&digest_hd, GNUTLS_MAC_SHA256, key->data,
			   key->size);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }
  _gnutls_hmac (&digest_hd, ticket->key_name, KEY_NAME_SIZE);
  _gnutls_hmac (&digest_hd, ticket->IV, IV_SIZE);
  length16 = _gnutls_conv_uint16 (ticket->encrypted_state_len);
  _gnutls_hmac (&digest_hd, &length16, 2);
  _gnutls_hmac (&digest_hd, ticket->encrypted_state,
		ticket->encrypted_state_len);
  _gnutls_hmac_deinit (&digest_hd, digest);

  return 0;
}

static int
decrypt_ticket (gnutls_session_t session, struct ticket *ticket)
{
  cipher_hd_st cipher_hd;
  gnutls_datum_t key, IV, mac_secret, state;
  opaque final[32];
  time_t timestamp = time (0);
  int ret;

  /* Check the integrity of ticket using HMAC-SHA-256. */
  mac_secret.data =
    session->security_parameters.extensions.session_ticket_key->mac_secret;
  mac_secret.size = MAC_SECRET_SIZE;
  ret = digest_ticket (&mac_secret, ticket, final);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  if (memcmp (ticket->mac, final, MAC_SIZE))
    {
      gnutls_assert ();
      return GNUTLS_E_DECRYPTION_FAILED;
    }

  /* Decrypt encrypted_state using 128-bit AES in CBC mode. */
  key.data = session->security_parameters.extensions.session_ticket_key->key;
  key.size = KEY_SIZE;
  IV.data = ticket->IV;
  IV.size = IV_SIZE;
  ret =
    _gnutls_cipher_init (&cipher_hd, GNUTLS_CIPHER_AES_128_CBC, &key, &IV);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }
  ret = _gnutls_cipher_decrypt (&cipher_hd, ticket->encrypted_state,
				ticket->encrypted_state_len);
  _gnutls_cipher_deinit (&cipher_hd);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  /* Unpack security parameters. */
  state.data = ticket->encrypted_state;
  state.size = ticket->encrypted_state_len;
  ret = _gnutls_session_unpack (session, &state);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  if (timestamp - session->internals.resumed_security_parameters.timestamp >
      session->internals.expire_time
      || session->internals.resumed_security_parameters.timestamp > timestamp)
    {
      gnutls_assert ();
      return GNUTLS_E_EXPIRED;
    }

  session->internals.resumed = RESUME_TRUE;

  return 0;
}

static int
encrypt_ticket (gnutls_session_t session, struct ticket *ticket)
{
  cipher_hd_st cipher_hd;
  gnutls_datum_t key, IV, mac_secret, state, encrypted_state;
  int blocksize;
  int ret;

  /* Pack security parameters. */
  ret = _gnutls_session_pack (session, &state);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }
  blocksize = _gnutls_cipher_get_block_size (GNUTLS_CIPHER_AES_128_CBC);
  encrypted_state.size =
    ((state.size + blocksize - 1) / blocksize) * blocksize;
  encrypted_state.data = gnutls_malloc (encrypted_state.size);
  if (!encrypted_state.data)
    {
      gnutls_assert ();
      _gnutls_free_datum (&state);
      return GNUTLS_E_MEMORY_ERROR;
    }
  memset (encrypted_state.data, 0, encrypted_state.size);
  memcpy (encrypted_state.data, state.data, state.size);
  _gnutls_free_datum (&state);

  /* Encrypt state using 128-bit AES in CBC mode. */
  key.data = session->security_parameters.extensions.session_ticket_key->key;
  key.size = KEY_SIZE;
  IV.data = session->security_parameters.extensions.session_ticket_IV;
  IV.size = IV_SIZE;
  ret =
    _gnutls_cipher_init (&cipher_hd, GNUTLS_CIPHER_AES_128_CBC, &key, &IV);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (&encrypted_state);
      return ret;
    }

  ret = _gnutls_cipher_encrypt (&cipher_hd, encrypted_state.data,
				encrypted_state.size);
  _gnutls_cipher_deinit (&cipher_hd);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (&encrypted_state);
      return ret;
    }

  /* Fill the ticket structure to compute MAC. */
  memcpy (ticket->key_name,
	  session->security_parameters.extensions.
	  session_ticket_key->key_name, KEY_NAME_SIZE);
  memcpy (ticket->IV, IV.data, IV.size);
  ticket->encrypted_state_len = encrypted_state.size;
  ticket->encrypted_state = encrypted_state.data;

  mac_secret.data =
    session->security_parameters.extensions.session_ticket_key->mac_secret;
  mac_secret.size = MAC_SECRET_SIZE;
  ret = digest_ticket (&mac_secret, ticket, ticket->mac);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (&encrypted_state);
      return ret;
    }

  return 0;
}

int
_gnutls_session_ticket_recv_params (gnutls_session_t session,
				    const opaque * data, size_t _data_size)
{
  ssize_t data_size = _data_size;

  if (!session->internals.session_ticket_enable)
    return 0;

  if (session->security_parameters.entity == GNUTLS_SERVER)
    {
      struct ticket ticket;
      const opaque *encrypted_state;
      int ret;

      /* The client requested a new session ticket. */
      if (data_size == 0)
	{
	  session->internals.session_ticket_renew = 1;
	  return 0;
	}

      DECR_LEN (data_size, KEY_NAME_SIZE);
      memcpy (ticket.key_name, data, KEY_NAME_SIZE);
      data += KEY_NAME_SIZE;

      /* If the key name of the ticket does not match the one that we
         hold, issue a new ticket. */
      if (memcmp (ticket.key_name,
		  session->security_parameters.extensions.
		  session_ticket_key->key_name, KEY_NAME_SIZE))
	{
	  session->internals.session_ticket_renew = 1;
	  return 0;
	}

      DECR_LEN (data_size, IV_SIZE);
      memcpy (ticket.IV, data, IV_SIZE);
      data += IV_SIZE;

      DECR_LEN (data_size, 2);
      ticket.encrypted_state_len = _gnutls_read_uint16 (data);
      data += 2;

      encrypted_state = data;

      DECR_LEN (data_size, ticket.encrypted_state_len);
      data += ticket.encrypted_state_len;

      DECR_LEN (data_size, MAC_SIZE);
      memcpy (ticket.mac, data, MAC_SIZE);

      ticket.encrypted_state = gnutls_malloc (ticket.encrypted_state_len);
      if (!ticket.encrypted_state)
	{
	  gnutls_assert ();
	  return GNUTLS_E_MEMORY_ERROR;
	}
      memcpy (ticket.encrypted_state, encrypted_state,
	      ticket.encrypted_state_len);

      ret = decrypt_ticket (session, &ticket);
      gnutls_free (ticket.encrypted_state);
      if (ret < 0)
	{
	  session->internals.session_ticket_renew = 1;
	  return 0;
	}
    }
  else
    {
      if (data_size == 0)
	{
	  session->internals.session_ticket_renew = 1;
	  return 0;
	}
    }

  return 0;
}

/* returns a positive number if we send the extension data, zero if we
   do not want to send it, and a negative number on failure.
 */
int
_gnutls_session_ticket_send_params (gnutls_session_t session,
				    opaque * data, size_t _data_size)
{
  ssize_t data_size = _data_size;

  if (!session->internals.session_ticket_enable)
    return 0;

  if (session->security_parameters.entity == GNUTLS_SERVER)
    {
      if (session->internals.session_ticket_renew)
	{
	  return GNUTLS_E_INT_RET_0;
	}
    }
  else
    {
      if (session->internals.resumed_security_parameters.extensions.
	  session_ticket_len > 0)
	{
	  DECR_LENGTH_RET (data_size,
			   session->internals.resumed_security_parameters.
			   extensions.session_ticket_len,
			   GNUTLS_E_SHORT_MEMORY_BUFFER);
	  memcpy (data,
		  session->internals.resumed_security_parameters.extensions.
		  session_ticket,
		  session->internals.resumed_security_parameters.extensions.
		  session_ticket_len);

	  return session->internals.resumed_security_parameters.
	    extensions.session_ticket_len;
	}
      else
	{
	  return GNUTLS_E_INT_RET_0;
	}
    }
  return 0;
}

/**
 * gnutls_session_ticket_key_generate:
 * @key: is a pointer to a #gnutls_datum_t which will contain a newly
 * created key.
 *
 * Generate a random key to encrypt security parameters within
 * SessionTicket.
 *
 * Returns: On success, %GNUTLS_E_SUCCESS (0) is returned, or an
 * error code.
 *
 * Since: 2.10.0
 **/
int
gnutls_session_ticket_key_generate (gnutls_datum_t * key)
{
  int ret;

  key->size = sizeof (struct gnutls_session_ticket_key_st);
  key->data = gnutls_malloc (key->size);
  if (!key->data)
    {
      gnutls_assert ();
      return GNUTLS_E_MEMORY_ERROR;
    }

  ret = _gnutls_rnd (GNUTLS_RND_RANDOM, key->data, key->size);
  if (ret < 0)
    {
      gnutls_assert ();
      _gnutls_free_datum (key);
      return ret;
    }

  return 0;
}

/**
 * gnutls_session_ticket_enable_client:
 * @session: is a #gnutls_session_t structure.
 *
 * Request that the client should attempt session resumption using
 * SessionTicket.
 *
 * Returns: On success, %GNUTLS_E_SUCCESS (0) is returned, or an
 * error code.
 *
 * Since: 2.10.0
 **/
int
gnutls_session_ticket_enable_client (gnutls_session_t session)
{
  if (!session)
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  session->internals.session_ticket_enable = 1;
  return 0;
}

/**
 * gnutls_session_ticket_enable_server:
 * @session: is a #gnutls_session_t structure.
 * @key: key to encrypt session parameters.
 *
 * Request that the server should attempt session resumption using
 * SessionTicket.  @key must be initialized with
 * gnutls_session_ticket_key_generate().
 *
 * Returns: On success, %GNUTLS_E_SUCCESS (0) is returned, or an
 * error code.
 *
 * Since: 2.10.0
 **/
int
gnutls_session_ticket_enable_server (gnutls_session_t session,
				     const gnutls_datum_t * key)
{
  int ret;

  if (!session || !key
      || key->size != sizeof (struct gnutls_session_ticket_key_st))
    {
      gnutls_assert ();
      return GNUTLS_E_INVALID_REQUEST;
    }

  ret = _gnutls_rnd (GNUTLS_RND_RANDOM,
		     session->security_parameters.extensions.
		     session_ticket_IV, IV_SIZE);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  session->security_parameters.extensions.session_ticket_key =
    (struct gnutls_session_ticket_key_st *) key->data;
  session->internals.session_ticket_enable = 1;
  return 0;
}

int
_gnutls_send_new_session_ticket (gnutls_session_t session, int again)
{
  uint8_t *data = NULL, *p;
  int data_size = 0;
  int ret;
  struct ticket ticket;
  uint16_t ticket_len;
  gnutls_cipher_algorithm_t write_bulk_cipher_algorithm;
  gnutls_mac_algorithm_t write_mac_algorithm;
  gnutls_compression_method_t write_compression_algorithm;

#define SAVE_WRITE_SECURITY_PARAMETERS					\
  do									\
    {									\
      write_bulk_cipher_algorithm =					\
	session->security_parameters.write_bulk_cipher_algorithm;	\
      write_mac_algorithm =						\
	session->security_parameters.write_mac_algorithm;		\
      write_compression_algorithm =					\
	session->security_parameters.write_compression_algorithm;	\
    }									\
  while (0)

#define RESTORE_WRITE_SECURITY_PARAMETERS				\
  do									\
    {									\
      session->security_parameters.write_bulk_cipher_algorithm =	\
	write_bulk_cipher_algorithm;					\
      session->security_parameters.write_mac_algorithm =		\
	write_mac_algorithm;						\
      session->security_parameters.write_compression_algorithm =	\
	write_compression_algorithm;					\
    }									\
  while (0)

  if (again == 0)
    {
      /* XXX: Temporarily set write algorithms to be used.
         _gnutls_write_connection_state_init() does this job, but it also
         triggers encryption, while NewSessionTicket should not be
         encrypted in the record layer. */
      SAVE_WRITE_SECURITY_PARAMETERS;
      ret = _gnutls_set_write_cipher (session,
				      _gnutls_cipher_suite_get_cipher_algo
				      (&session->security_parameters.
				       current_cipher_suite));
      if (ret < 0)
	return ret;
      ret = _gnutls_set_write_mac (session,
				   _gnutls_cipher_suite_get_mac_algo
				   (&session->security_parameters.
				    current_cipher_suite));
      if (ret < 0)
	return ret;
      ret = _gnutls_set_write_compression (session,
					   session->internals.
					   compression_method);
      if (ret < 0)
	return ret;

      ret = encrypt_ticket (session, &ticket);
      RESTORE_WRITE_SECURITY_PARAMETERS;
      if (ret < 0)
	{
	  gnutls_assert ();
	  return ret;
	}

      ticket_len = KEY_NAME_SIZE + IV_SIZE + 2 + ticket.encrypted_state_len
	+ MAC_SIZE;

      data = gnutls_malloc (4 + 2 + ticket_len);
      if (!data)
	{
	  gnutls_assert ();
	  gnutls_free (ticket.encrypted_state);
	  return GNUTLS_E_MEMORY_ERROR;
	}

      p = data;
      /* FIXME: ticket lifetime is fixed to 10 days, which should be
         customizable. */
      _gnutls_write_uint32 (864000, p);
      p += 4;

      _gnutls_write_uint16 (ticket_len, p);
      p += 2;

      memcpy (p, ticket.key_name, KEY_NAME_SIZE);
      p += KEY_NAME_SIZE;

      memcpy (p, ticket.IV, IV_SIZE);
      p += IV_SIZE;

      _gnutls_write_uint16 (ticket.encrypted_state_len, p);
      p += 2;

      memcpy (p, ticket.encrypted_state, ticket.encrypted_state_len);
      gnutls_free (ticket.encrypted_state);
      p += ticket.encrypted_state_len;

      memcpy (p, ticket.mac, MAC_SIZE);
      p += MAC_SIZE;

      data_size = p - data;
    }

  ret = _gnutls_send_handshake (session, data_size ? data : NULL, data_size,
				GNUTLS_HANDSHAKE_NEW_SESSION_TICKET);
  gnutls_free (data);

  return ret;
}

int
_gnutls_recv_new_session_ticket (gnutls_session_t session)
{
  uint8_t *data = NULL, *p;
  int data_size;
  uint32_t lifetime_hint;
  uint16_t ticket_len;
  int ret;

  ret = _gnutls_recv_handshake (session, &data, &data_size,
				GNUTLS_HANDSHAKE_NEW_SESSION_TICKET,
				MANDATORY_PACKET);
  if (ret < 0)
    {
      gnutls_assert ();
      return ret;
    }

  p = data;
  DECR_LENGTH_COM (data_size, 4, goto error);
  lifetime_hint = _gnutls_read_uint32 (p);
  p += 4;

  DECR_LENGTH_COM (data_size, 2, goto error);
  ticket_len = _gnutls_read_uint16 (p);
  p += 2;

  DECR_LENGTH_COM (data_size, ticket_len, goto error);
  session->security_parameters.extensions.session_ticket =
    gnutls_realloc (session->security_parameters.extensions.session_ticket,
		    ticket_len);
  if (!session->security_parameters.extensions.session_ticket)
    {
      gnutls_assert ();
      gnutls_free (data);
      return GNUTLS_E_MEMORY_ERROR;
    }
  memcpy (session->security_parameters.extensions.session_ticket,
	  p, ticket_len);
  gnutls_free (data);
  session->security_parameters.extensions.session_ticket_len = ticket_len;

  /* Discard the current session ID.  (RFC5077 3.4) */
  ret = _gnutls_generate_session_id (session->security_parameters.session_id,
				     &session->security_parameters.
				     session_id_size);
  if (ret < 0)
    {
      gnutls_assert ();
      gnutls_free (data);
      gnutls_free (session->security_parameters.extensions.session_ticket);
      return GNUTLS_E_INTERNAL_ERROR;
    }
  return 0;

error:
  gnutls_free (data);
  return GNUTLS_E_UNEXPECTED_PACKET_LENGTH;
}

#endif