/*
   rdesktop: A Remote Desktop Protocol client.
   RDP licensing negotiation
   Copyright (C) Matthew Chapman 1999-2000
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "rdesktop.h"
#include <openssl/rc4.h>

extern char* username;
extern char* hostname;
extern Bool licence;

static uint8 licence_key[16];
static uint8 licence_sign_key[16];

Bool licence_issued = False;

/* Generate a session key and RC4 keys, given client and server randoms */
void
licence_generate_keys (uint8 * client_key, uint8 * server_key,
		       uint8 * client_rsa)
{
  uint8 session_key[48];
  uint8 temp_hash[48];

  /* Generate session key - two rounds of sec_hash_48 */
  sec_hash_48 (temp_hash, client_rsa, client_key, server_key, 65);
  sec_hash_48 (session_key, temp_hash, server_key, client_key, 65);

  /* Store first 16 bytes of session key, for generating signatures */
  memcpy (licence_sign_key, session_key, 16);

  /* Generate RC4 key */
  sec_hash_16 (licence_key, &session_key[16], client_key, server_key);
}

/* Send a licence request packet */
static void
licence_send_request (uint8 * client_random, uint8 * rsa_data,
		      char *user, char *host)
{
  uint32 sec_flags = SEC_LICENCE_NEG;
  uint16 userlen = ( user == 0 ? 0 : strlen (user) + 1);
  uint16 hostlen = ( host == 0 ? 0 : strlen (host) + 1);
  uint16 length = 120 + userlen + hostlen;
  STREAM s;

  s = sec_init (sec_flags, length + 2);

  out_uint16_le (s, LICENCE_TAG_REQUEST);
  out_uint16_le (s, length);

  out_uint32_le (s, 1);
  out_uint32_le (s, 0xff010000);

  out_uint8p (s, client_random, SEC_RANDOM_SIZE);
  out_uint16 (s, 0);
  out_uint16_le (s, (SEC_MODULUS_SIZE + SEC_PADDING_SIZE));
  out_uint8p (s, rsa_data, SEC_MODULUS_SIZE);
  out_uint8s (s, SEC_PADDING_SIZE);

  out_uint16 (s, LICENCE_TAG_USER);
  out_uint16 (s, userlen);
  out_uint8p (s, user, userlen);

  out_uint16 (s, LICENCE_TAG_HOST);
  out_uint16 (s, hostlen);
  out_uint8p (s, host, hostlen);

  s_mark_end (s);
  sec_send (s, sec_flags);
}

/* Process a licence demand packet */
static void
licence_process_demand (STREAM s)
{
  uint8 null_data[SEC_MODULUS_SIZE];
  uint8 *server_random;

  /* Retrieve the server random from the incoming packet */
  in_uint8p (s, server_random, SEC_RANDOM_SIZE);

  /* We currently use null client keys. This is a bit naughty but, hey,
     the security of licence negotiation isn't exactly paramount. */
  memset (null_data, 0, sizeof (null_data));
  licence_generate_keys (null_data, server_random, null_data);

  /* Send a certificate request back to the server */
  licence_send_request (null_data, null_data, username, hostname);
}

/* Send an authentication response packet */
static void
licence_send_authresp (uint8 * token, uint8 * crypt_hwid, uint8 * signature)
{
  uint32 sec_flags = SEC_LICENCE_NEG;
  uint16 length = 58;
  STREAM s;

  s = sec_init (sec_flags, length + 2);

  out_uint16_le (s, LICENCE_TAG_AUTHRESP);
  out_uint16_le (s, length);

  out_uint16_le (s, 1);
  out_uint16_le (s, LICENCE_TOKEN_SIZE);
  out_uint8p (s, token, LICENCE_TOKEN_SIZE);

  out_uint16_le (s, 1);
  out_uint16_le (s, LICENCE_HWID_SIZE);
  out_uint8p (s, crypt_hwid, LICENCE_HWID_SIZE);

  out_uint8p (s, signature, LICENCE_SIGNATURE_SIZE);

  s_mark_end (s);
  sec_send (s, sec_flags);
}

/* Parse an authentication request packet */
static Bool
licence_parse_authreq (STREAM s, uint8 ** token, uint8 ** signature)
{
  uint16 tokenlen;

  in_uint8s (s, 6);		/* unknown: f8 3d 15 00 04 f6 */

  in_uint16_le (s, tokenlen);
  if (tokenlen != LICENCE_TOKEN_SIZE)
    {
      ERROR ("token len %d\n", tokenlen);
      return False;
    }

  in_uint8p (s, *token, tokenlen);
  in_uint8p (s, *signature, LICENCE_SIGNATURE_SIZE);

  return s_check_end (s);
}

/* Process an authentication request packet */
static void
licence_process_authreq (STREAM s)
{
  uint8 *in_token, *in_sig;
  uint8 out_token[LICENCE_TOKEN_SIZE], decrypt_token[LICENCE_TOKEN_SIZE];
  uint8 hwid[LICENCE_HWID_SIZE], crypt_hwid[LICENCE_HWID_SIZE];
  uint8 sealed_buffer[LICENCE_TOKEN_SIZE + LICENCE_HWID_SIZE];
  uint8 out_sig[LICENCE_SIGNATURE_SIZE];
  RC4_KEY crypt_key;

  /* Parse incoming packet and save the encrypted token */
  licence_parse_authreq (s, &in_token, &in_sig);
  memcpy (out_token, in_token, LICENCE_TOKEN_SIZE);

  /* Decrypt the token. It should read TEST in Unicode. */
  RC4_set_key (&crypt_key, 16, licence_key);
  RC4 (&crypt_key, LICENCE_TOKEN_SIZE, in_token, decrypt_token);

  /* Construct HWID */
  buf_out_uint32 (hwid, 2);
  strncpy (hwid + 4, hostname, LICENCE_HWID_SIZE - 4);

  /* Generate a signature for a buffer of token and HWID */
  memcpy (sealed_buffer, decrypt_token, LICENCE_TOKEN_SIZE);
  memcpy (sealed_buffer + LICENCE_TOKEN_SIZE, hwid, LICENCE_HWID_SIZE);
  sec_sign (out_sig, licence_sign_key, 16,
	    sealed_buffer, sizeof (sealed_buffer));

  /* Deliberately break signature if licencing disabled */
  if (!licence)
    memset (out_sig, 0, sizeof (out_sig));

  /* Now encrypt the HWID */
  RC4_set_key (&crypt_key, 16, licence_key);
  RC4 (&crypt_key, LICENCE_HWID_SIZE, hwid, crypt_hwid);

  licence_send_authresp (out_token, crypt_hwid, out_sig);
}

/* Process an licence issue packet */
static void
licence_process_issue (STREAM s)
{
  RC4_KEY crypt_key;
  uint32 length;
  uint16 check;

  in_uint8s (s, 2);		/* 3d 45 - unknown */
  in_uint16_le (s, length);
  if (!s_check_rem (s, length))
    return;

  RC4_set_key (&crypt_key, 16, licence_key);
  RC4 (&crypt_key, length, s->p, s->p);

  in_uint16 (s, check);
  if (check != 0)
    return;

  licence_issued = True;

  /* We should save the licence here */
  STATUS ("Server issued licence.\n");
}

/* Process a licence packet */
void
licence_process (STREAM s)
{
  uint16 tag;

  in_uint16_le (s, tag);
  in_uint8s (s, 2);		/* length */

  switch (tag)
    {
    case LICENCE_TAG_DEMAND:
      licence_process_demand (s);
      break;

    case LICENCE_TAG_AUTHREQ:
      licence_process_authreq (s);
      break;

    case LICENCE_TAG_ISSUE:
      licence_process_issue (s);
      break;

    case LICENCE_TAG_RESULT:
      licence_issued = True;
      break;

    default:
      NOTIMP ("licence tag 0x%x\n", tag);
    }
}