1 |
/* |
2 |
rdesktop: A Remote Desktop Protocol client. |
3 |
Protocol services - RDP encryption and licensing |
4 |
Copyright (C) Matthew Chapman 1999-2000 |
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|
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This program is free software; you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation; either version 2 of the License, or |
9 |
(at your option) any later version. |
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|
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This program is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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|
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You should have received a copy of the GNU General Public License |
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along with this program; if not, write to the Free Software |
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
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*/ |
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|
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#include "rdesktop.h" |
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#include "crypto/rc4.h" |
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#include "crypto/md5.h" |
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#include "crypto/sha.h" |
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#include "crypto/arith.h" |
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|
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extern char hostname[16]; |
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extern int width; |
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extern int height; |
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extern int keylayout; |
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|
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static int rc4_key_len; |
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static RC4_KEY rc4_decrypt_key; |
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static RC4_KEY rc4_encrypt_key; |
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|
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static uint8 sec_sign_key[8]; |
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static uint8 sec_decrypt_key[16]; |
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static uint8 sec_encrypt_key[16]; |
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static uint8 sec_decrypt_update_key[8]; |
40 |
static uint8 sec_encrypt_update_key[8]; |
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static uint8 sec_crypted_random[64]; |
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|
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/* |
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* General purpose 48-byte transformation, using two 32-byte salts (generally, |
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* a client and server salt) and a global salt value used for padding. |
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* Both SHA1 and MD5 algorithms are used. |
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*/ |
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void sec_hash_48(uint8 *out, uint8 *in, uint8 *salt1, uint8 *salt2, |
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uint8 salt) |
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{ |
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uint8 shasig[20]; |
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uint8 pad[4]; |
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SHA_CTX sha; |
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MD5_CTX md5; |
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int i; |
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|
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for (i = 0; i < 3; i++) |
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{ |
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memset(pad, salt + i, i + 1); |
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|
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SHA1_Init(&sha); |
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SHA1_Update(&sha, pad, i + 1); |
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SHA1_Update(&sha, in, 48); |
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SHA1_Update(&sha, salt1, 32); |
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SHA1_Update(&sha, salt2, 32); |
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SHA1_Final(shasig, &sha); |
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|
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MD5_Init(&md5); |
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MD5_Update(&md5, in, 48); |
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MD5_Update(&md5, shasig, 20); |
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MD5_Final(&out[i * 16], &md5); |
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} |
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} |
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|
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/* |
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* Weaker 16-byte transformation, also using two 32-byte salts, but |
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* only using a single round of MD5. |
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*/ |
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void sec_hash_16(uint8 *out, uint8 *in, uint8 *salt1, uint8 *salt2) |
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{ |
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MD5_CTX md5; |
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|
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MD5_Init(&md5); |
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MD5_Update(&md5, in, 16); |
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MD5_Update(&md5, salt1, 32); |
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MD5_Update(&md5, salt2, 32); |
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MD5_Final(out, &md5); |
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} |
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|
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/* Reduce key entropy from 64 to 40 bits */ |
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static void sec_make_40bit(uint8 *key) |
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{ |
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key[0] = 0xd1; |
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key[1] = 0x26; |
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key[2] = 0x9e; |
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} |
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|
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/* Generate a session key and RC4 keys, given client and server randoms */ |
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static void sec_generate_keys(uint8 *client_key, uint8 *server_key, |
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int rc4_key_size) |
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{ |
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uint8 session_key[48]; |
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uint8 temp_hash[48]; |
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uint8 input[48]; |
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|
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/* Construct input data to hash */ |
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memcpy(input, client_key, 24); |
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memcpy(input + 24, server_key, 24); |
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|
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/* Generate session key - two rounds of sec_hash_48 */ |
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sec_hash_48(temp_hash, input, client_key, server_key, 65); |
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sec_hash_48(session_key, temp_hash, client_key, server_key, 88); |
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|
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/* Store first 8 bytes of session key, for generating signatures */ |
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memcpy(sec_sign_key, session_key, 8); |
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|
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/* Generate RC4 keys */ |
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sec_hash_16(sec_decrypt_key, &session_key[16], client_key, |
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server_key); |
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sec_hash_16(sec_encrypt_key, &session_key[32], client_key, |
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server_key); |
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|
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if (rc4_key_size == 1) |
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{ |
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DEBUG("40-bit encryption enabled\n"); |
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sec_make_40bit(sec_sign_key); |
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sec_make_40bit(sec_decrypt_key); |
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sec_make_40bit(sec_encrypt_key); |
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rc4_key_len = 8; |
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} |
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else |
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{ |
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DEBUG("128-bit encryption enabled\n"); |
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rc4_key_len = 16; |
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} |
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|
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/* Store first 8 bytes of RC4 keys as update keys */ |
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memcpy(sec_decrypt_update_key, sec_decrypt_key, 8); |
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memcpy(sec_encrypt_update_key, sec_encrypt_key, 8); |
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|
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/* Initialise RC4 state arrays */ |
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RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key); |
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RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key); |
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} |
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|
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static uint8 pad_54[40] = { |
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54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, |
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54, 54, 54, |
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54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, |
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54, 54, 54 |
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}; |
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|
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static uint8 pad_92[48] = { |
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92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, |
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92, 92, 92, 92, 92, 92, 92, |
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92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, |
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92, 92, 92, 92, 92, 92, 92 |
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}; |
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|
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/* Output a uint32 into a buffer (little-endian) */ |
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void buf_out_uint32(uint8 *buffer, uint32 value) |
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{ |
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buffer[0] = (value) & 0xff; |
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buffer[1] = (value >> 8) & 0xff; |
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buffer[2] = (value >> 16) & 0xff; |
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buffer[3] = (value >> 24) & 0xff; |
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} |
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|
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/* Generate a signature hash, using a combination of SHA1 and MD5 */ |
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void sec_sign(uint8 *signature, uint8 *session_key, int length, |
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uint8 *data, int datalen) |
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{ |
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uint8 shasig[20]; |
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uint8 md5sig[16]; |
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uint8 lenhdr[4]; |
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SHA_CTX sha; |
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MD5_CTX md5; |
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|
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buf_out_uint32(lenhdr, datalen); |
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|
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SHA1_Init(&sha); |
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SHA1_Update(&sha, session_key, length); |
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SHA1_Update(&sha, pad_54, 40); |
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SHA1_Update(&sha, lenhdr, 4); |
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SHA1_Update(&sha, data, datalen); |
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SHA1_Final(shasig, &sha); |
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|
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MD5_Init(&md5); |
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MD5_Update(&md5, session_key, length); |
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MD5_Update(&md5, pad_92, 48); |
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MD5_Update(&md5, shasig, 20); |
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MD5_Final(md5sig, &md5); |
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|
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memcpy(signature, md5sig, length); |
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} |
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|
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/* Update an encryption key - similar to the signing process */ |
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static void sec_update(uint8 *key, uint8 *update_key) |
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{ |
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uint8 shasig[20]; |
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SHA_CTX sha; |
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MD5_CTX md5; |
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RC4_KEY update; |
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|
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SHA1_Init(&sha); |
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SHA1_Update(&sha, update_key, 8); |
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SHA1_Update(&sha, pad_54, 40); |
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SHA1_Update(&sha, key, 8); |
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SHA1_Final(shasig, &sha); |
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|
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MD5_Init(&md5); |
212 |
MD5_Update(&md5, update_key, 8); |
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MD5_Update(&md5, pad_92, 48); |
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MD5_Update(&md5, shasig, 20); |
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MD5_Final(key, &md5); |
216 |
|
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RC4_set_key(&update, rc4_key_len, key); |
218 |
RC4(&update, rc4_key_len, key, key); |
219 |
|
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if (rc4_key_len == 8) |
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sec_make_40bit(key); |
222 |
} |
223 |
|
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/* Encrypt data using RC4 */ |
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static void sec_encrypt(uint8 *data, int length) |
226 |
{ |
227 |
static int use_count; |
228 |
|
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if (use_count == 4096) |
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{ |
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sec_update(sec_encrypt_key, sec_encrypt_update_key); |
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RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key); |
233 |
use_count = 0; |
234 |
} |
235 |
|
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RC4(&rc4_encrypt_key, length, data, data); |
237 |
use_count++; |
238 |
} |
239 |
|
240 |
/* Decrypt data using RC4 */ |
241 |
static void sec_decrypt(uint8 *data, int length) |
242 |
{ |
243 |
static int use_count; |
244 |
|
245 |
if (use_count == 4096) |
246 |
{ |
247 |
sec_update(sec_decrypt_key, sec_decrypt_update_key); |
248 |
RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key); |
249 |
use_count = 0; |
250 |
} |
251 |
|
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RC4(&rc4_decrypt_key, length, data, data); |
253 |
use_count++; |
254 |
} |
255 |
|
256 |
/* Read in a NUMBER from a buffer */ |
257 |
static void sec_read_number(NUMBER * num, uint8 *buffer, int len) |
258 |
{ |
259 |
INT *data = num->n_part; |
260 |
int i, j; |
261 |
|
262 |
for (i = 0, j = 0; j < len; i++, j += 2) |
263 |
data[i] = buffer[j] | (buffer[j + 1] << 8); |
264 |
|
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num->n_len = i; |
266 |
} |
267 |
|
268 |
/* Write a NUMBER to a buffer */ |
269 |
static void sec_write_number(NUMBER * num, uint8 *buffer, int len) |
270 |
{ |
271 |
INT *data = num->n_part; |
272 |
int i, j; |
273 |
|
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for (i = 0, j = 0; j < len; i++, j += 2) |
275 |
{ |
276 |
buffer[j] = data[i] & 0xff; |
277 |
buffer[j + 1] = data[i] >> 8; |
278 |
} |
279 |
} |
280 |
|
281 |
/* Perform an RSA public key encryption operation */ |
282 |
static void sec_rsa_encrypt(uint8 *out, uint8 *in, int len, |
283 |
uint8 *modulus, uint8 *exponent) |
284 |
{ |
285 |
NUMBER data, key; |
286 |
|
287 |
/* Set modulus for arithmetic */ |
288 |
sec_read_number(&key, modulus, SEC_MODULUS_SIZE); |
289 |
m_init(&key, NULL); |
290 |
|
291 |
/* Exponentiate */ |
292 |
sec_read_number(&data, in, len); |
293 |
sec_read_number(&key, exponent, SEC_EXPONENT_SIZE); |
294 |
m_exp(&data, &key, &data); |
295 |
sec_write_number(&data, out, SEC_MODULUS_SIZE); |
296 |
} |
297 |
|
298 |
/* Initialise secure transport packet */ |
299 |
STREAM sec_init(uint32 flags, int maxlen) |
300 |
{ |
301 |
int hdrlen; |
302 |
STREAM s; |
303 |
|
304 |
hdrlen = (flags & SEC_ENCRYPT) ? 12 : 4; |
305 |
s = mcs_init(maxlen + hdrlen); |
306 |
s_push_layer(s, sec_hdr, hdrlen); |
307 |
|
308 |
return s; |
309 |
} |
310 |
|
311 |
/* Transmit secure transport packet */ |
312 |
void sec_send(STREAM s, uint32 flags) |
313 |
{ |
314 |
int datalen; |
315 |
|
316 |
s_pop_layer(s, sec_hdr); |
317 |
out_uint32_le(s, flags); |
318 |
|
319 |
if (flags & SEC_ENCRYPT) |
320 |
{ |
321 |
flags &= ~SEC_ENCRYPT; |
322 |
datalen = s->end - s->p - 8; |
323 |
|
324 |
#if RDP_DEBUG |
325 |
DEBUG("Sending encrypted packet:\n"); |
326 |
hexdump(s->p + 8, datalen); |
327 |
#endif |
328 |
|
329 |
sec_sign(s->p, sec_sign_key, 8, s->p + 8, datalen); |
330 |
sec_encrypt(s->p + 8, datalen); |
331 |
} |
332 |
|
333 |
mcs_send(s); |
334 |
} |
335 |
|
336 |
/* Transfer the client random to the server */ |
337 |
static void sec_establish_key() |
338 |
{ |
339 |
uint32 length = SEC_MODULUS_SIZE + SEC_PADDING_SIZE; |
340 |
uint32 flags = SEC_CLIENT_RANDOM; |
341 |
STREAM s; |
342 |
|
343 |
s = sec_init(flags, 76); |
344 |
|
345 |
out_uint32_le(s, length); |
346 |
out_uint8p(s, sec_crypted_random, SEC_MODULUS_SIZE); |
347 |
out_uint8s(s, SEC_PADDING_SIZE); |
348 |
|
349 |
s_mark_end(s); |
350 |
sec_send(s, flags); |
351 |
} |
352 |
|
353 |
/* Output connect initial data blob */ |
354 |
static void sec_out_mcs_data(STREAM s) |
355 |
{ |
356 |
int hostlen = 2 * strlen(hostname); |
357 |
|
358 |
out_uint16_be(s, 5); /* unknown */ |
359 |
out_uint16_be(s, 0x14); |
360 |
out_uint8(s, 0x7c); |
361 |
out_uint16_be(s, 1); |
362 |
|
363 |
out_uint16_be(s, (158 | 0x8000)); /* remaining length */ |
364 |
|
365 |
out_uint16_be(s, 8); /* length? */ |
366 |
out_uint16_be(s, 16); |
367 |
out_uint8(s, 0); |
368 |
out_uint16_le(s, 0xc001); |
369 |
out_uint8(s, 0); |
370 |
|
371 |
out_uint32_le(s, 0x61637544); /* "Duca" ?! */ |
372 |
out_uint16_be(s, (144 | 0x8000)); /* remaining length */ |
373 |
|
374 |
/* Client information */ |
375 |
out_uint16_le(s, SEC_TAG_CLI_INFO); |
376 |
out_uint16_le(s, 136); /* length */ |
377 |
out_uint16_le(s, 1); |
378 |
out_uint16_le(s, 8); |
379 |
out_uint16_le(s, width); |
380 |
out_uint16_le(s, height); |
381 |
out_uint16_le(s, 0xca01); |
382 |
out_uint16_le(s, 0xaa03); |
383 |
out_uint32_le(s, keylayout); |
384 |
out_uint32_le(s, 419); /* client build? we are 419 compatible :-) */ |
385 |
|
386 |
/* Unicode name of client, padded to 32 bytes */ |
387 |
rdp_out_unistr(s, hostname, hostlen); |
388 |
out_uint8s(s, 30 - hostlen); |
389 |
|
390 |
out_uint32_le(s, 4); |
391 |
out_uint32(s, 0); |
392 |
out_uint32_le(s, 12); |
393 |
out_uint8s(s, 64); /* reserved? 4 + 12 doublewords */ |
394 |
|
395 |
out_uint16(s, 0xca01); |
396 |
out_uint16(s, 0); |
397 |
|
398 |
/* Client encryption settings */ |
399 |
out_uint16_le(s, SEC_TAG_CLI_CRYPT); |
400 |
out_uint16(s, 8); /* length */ |
401 |
out_uint32_le(s, 1); /* encryption enabled */ |
402 |
s_mark_end(s); |
403 |
} |
404 |
|
405 |
/* Parse a public key structure */ |
406 |
static BOOL sec_parse_public_key(STREAM s, uint8 **modulus, uint8 **exponent) |
407 |
{ |
408 |
uint32 magic, modulus_len; |
409 |
|
410 |
in_uint32_le(s, magic); |
411 |
if (magic != SEC_RSA_MAGIC) |
412 |
{ |
413 |
ERROR("RSA magic 0x%x\n", magic); |
414 |
return False; |
415 |
} |
416 |
|
417 |
in_uint32_le(s, modulus_len); |
418 |
if (modulus_len != SEC_MODULUS_SIZE + SEC_PADDING_SIZE) |
419 |
{ |
420 |
ERROR("modulus len 0x%x\n", modulus_len); |
421 |
return False; |
422 |
} |
423 |
|
424 |
in_uint8s(s, 8); /* modulus_bits, unknown */ |
425 |
in_uint8p(s, *exponent, SEC_EXPONENT_SIZE); |
426 |
in_uint8p(s, *modulus, SEC_MODULUS_SIZE); |
427 |
in_uint8s(s, SEC_PADDING_SIZE); |
428 |
|
429 |
return s_check(s); |
430 |
} |
431 |
|
432 |
/* Parse a crypto information structure */ |
433 |
static BOOL sec_parse_crypt_info(STREAM s, uint32 *rc4_key_size, |
434 |
uint8 **server_random, uint8 **modulus, |
435 |
uint8 **exponent) |
436 |
{ |
437 |
uint32 crypt_level, random_len, rsa_info_len; |
438 |
uint16 tag, length; |
439 |
uint8 *next_tag, *end; |
440 |
|
441 |
in_uint32_le(s, *rc4_key_size); /* 1 = 40-bit, 2 = 128-bit */ |
442 |
in_uint32_le(s, crypt_level); /* 1 = low, 2 = medium, 3 = high */ |
443 |
in_uint32_le(s, random_len); |
444 |
in_uint32_le(s, rsa_info_len); |
445 |
|
446 |
if (random_len != SEC_RANDOM_SIZE) |
447 |
{ |
448 |
ERROR("random len %d\n", random_len); |
449 |
return False; |
450 |
} |
451 |
|
452 |
in_uint8p(s, *server_random, random_len); |
453 |
|
454 |
/* RSA info */ |
455 |
end = s->p + rsa_info_len; |
456 |
if (end > s->end) |
457 |
return False; |
458 |
|
459 |
in_uint8s(s, 12); /* unknown */ |
460 |
|
461 |
while (s->p < end) |
462 |
{ |
463 |
in_uint16_le(s, tag); |
464 |
in_uint16_le(s, length); |
465 |
|
466 |
next_tag = s->p + length; |
467 |
|
468 |
switch (tag) |
469 |
{ |
470 |
case SEC_TAG_PUBKEY: |
471 |
if (!sec_parse_public_key |
472 |
(s, modulus, exponent)) |
473 |
return False; |
474 |
|
475 |
break; |
476 |
|
477 |
case SEC_TAG_KEYSIG: |
478 |
/* Is this a Microsoft key that we just got? */ |
479 |
/* Care factor: zero! */ |
480 |
break; |
481 |
|
482 |
default: |
483 |
NOTIMP("crypt tag 0x%x\n", tag); |
484 |
} |
485 |
|
486 |
s->p = next_tag; |
487 |
} |
488 |
|
489 |
return s_check_end(s); |
490 |
} |
491 |
|
492 |
/* Process crypto information blob */ |
493 |
static void sec_process_crypt_info(STREAM s) |
494 |
{ |
495 |
uint8 *server_random, *modulus, *exponent; |
496 |
uint8 client_random[SEC_RANDOM_SIZE]; |
497 |
uint32 rc4_key_size; |
498 |
|
499 |
if (!sec_parse_crypt_info(s, &rc4_key_size, &server_random, |
500 |
&modulus, &exponent)) |
501 |
return; |
502 |
|
503 |
/* Generate a client random, and hence determine encryption keys */ |
504 |
generate_random(client_random); |
505 |
sec_rsa_encrypt(sec_crypted_random, client_random, |
506 |
SEC_RANDOM_SIZE, modulus, exponent); |
507 |
sec_generate_keys(client_random, server_random, rc4_key_size); |
508 |
} |
509 |
|
510 |
/* Process connect response data blob */ |
511 |
static void sec_process_mcs_data(STREAM s) |
512 |
{ |
513 |
uint16 tag, length; |
514 |
uint8 *next_tag; |
515 |
|
516 |
in_uint8s(s, 23); /* header */ |
517 |
|
518 |
while (s->p < s->end) |
519 |
{ |
520 |
in_uint16_le(s, tag); |
521 |
in_uint16_le(s, length); |
522 |
|
523 |
if (length <= 4) |
524 |
return; |
525 |
|
526 |
next_tag = s->p + length - 4; |
527 |
|
528 |
switch (tag) |
529 |
{ |
530 |
case SEC_TAG_SRV_INFO: |
531 |
case SEC_TAG_SRV_3: |
532 |
break; |
533 |
|
534 |
case SEC_TAG_SRV_CRYPT: |
535 |
sec_process_crypt_info(s); |
536 |
break; |
537 |
|
538 |
default: |
539 |
NOTIMP("response tag 0x%x\n", tag); |
540 |
} |
541 |
|
542 |
s->p = next_tag; |
543 |
} |
544 |
} |
545 |
|
546 |
/* Receive secure transport packet */ |
547 |
STREAM sec_recv() |
548 |
{ |
549 |
uint32 sec_flags; |
550 |
STREAM s; |
551 |
|
552 |
while ((s = mcs_recv()) != NULL) |
553 |
{ |
554 |
in_uint32_le(s, sec_flags); |
555 |
|
556 |
if (sec_flags & SEC_LICENCE_NEG) |
557 |
{ |
558 |
licence_process(s); |
559 |
continue; |
560 |
} |
561 |
|
562 |
if (sec_flags & SEC_ENCRYPT) |
563 |
{ |
564 |
in_uint8s(s, 8); /* signature */ |
565 |
sec_decrypt(s->p, s->end - s->p); |
566 |
} |
567 |
|
568 |
return s; |
569 |
} |
570 |
|
571 |
return NULL; |
572 |
} |
573 |
|
574 |
/* Establish a secure connection */ |
575 |
BOOL sec_connect(char *server) |
576 |
{ |
577 |
struct stream mcs_data; |
578 |
|
579 |
/* We exchange some RDP data during the MCS-Connect */ |
580 |
mcs_data.size = 512; |
581 |
mcs_data.p = mcs_data.data = xmalloc(mcs_data.size); |
582 |
sec_out_mcs_data(&mcs_data); |
583 |
|
584 |
if (!mcs_connect(server, &mcs_data)) |
585 |
return False; |
586 |
|
587 |
sec_process_mcs_data(&mcs_data); |
588 |
sec_establish_key(); |
589 |
return True; |
590 |
} |
591 |
|
592 |
/* Disconnect a connection */ |
593 |
void sec_disconnect() |
594 |
{ |
595 |
mcs_disconnect(); |
596 |
} |