/[rdesktop]/sourceforge.net/trunk/rdesktop/secure.c
This is repository of my old source code which isn't updated any more. Go to git.rot13.org for current projects!
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Contents of /sourceforge.net/trunk/rdesktop/secure.c

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Revision 10 - (show annotations)
Tue Aug 15 10:23:24 2000 UTC (23 years, 8 months ago) by matty
File MIME type: text/plain
File size: 13417 byte(s)
Major commit of work from laptop - done in various free moments.
Implemented encryption layer and some basic licensing negotiation.
Reorganised code somewhat. While this is not quite as clean, it is
a lot faster - our parser speed was becoming a bottle-neck.

1 /*
2 rdesktop: A Remote Desktop Protocol client.
3 Protocol services - RDP encryption and licensing
4 Copyright (C) Matthew Chapman 1999-2000
5
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 */
20
21 #include "rdesktop.h"
22 #include "crypto/rc4.h"
23 #include "crypto/md5.h"
24 #include "crypto/sha.h"
25 #include "crypto/arith.h"
26
27 extern char hostname[16];
28 extern int width;
29 extern int height;
30 extern int keylayout;
31
32 static int rc4_key_len;
33 static RC4_KEY rc4_decrypt_key;
34 static RC4_KEY rc4_encrypt_key;
35
36 static uint8 sec_sign_key[8];
37 static uint8 sec_decrypt_key[16];
38 static uint8 sec_encrypt_key[16];
39 static uint8 sec_decrypt_update_key[8];
40 static uint8 sec_encrypt_update_key[8];
41 static uint8 sec_crypted_random[64];
42
43 /*
44 * General purpose 48-byte transformation, using two 32-byte salts (generally,
45 * a client and server salt) and a global salt value used for padding.
46 * Both SHA1 and MD5 algorithms are used.
47 */
48 void sec_hash_48(uint8 *out, uint8 *in, uint8 *salt1, uint8 *salt2, uint8 salt)
49 {
50 uint8 shasig[20];
51 uint8 pad[4];
52 SHA_CTX sha;
53 MD5_CTX md5;
54 int i;
55
56 for (i = 0; i < 3; i++)
57 {
58 memset(pad, salt+i, i+1);
59
60 SHA1_Init(&sha);
61 SHA1_Update(&sha, pad, i+1);
62 SHA1_Update(&sha, in, 48);
63 SHA1_Update(&sha, salt1, 32);
64 SHA1_Update(&sha, salt2, 32);
65 SHA1_Final(shasig, &sha);
66
67 MD5_Init(&md5);
68 MD5_Update(&md5, in, 48);
69 MD5_Update(&md5, shasig, 20);
70 MD5_Final(&out[i*16], &md5);
71 }
72 }
73
74 /*
75 * Weaker 16-byte transformation, also using two 32-byte salts, but
76 * only using a single round of MD5.
77 */
78 void sec_hash_16(uint8 *out, uint8 *in, uint8 *salt1, uint8 *salt2)
79 {
80 MD5_CTX md5;
81
82 MD5_Init(&md5);
83 MD5_Update(&md5, in, 16);
84 MD5_Update(&md5, salt1, 32);
85 MD5_Update(&md5, salt2, 32);
86 MD5_Final(out, &md5);
87 }
88
89 /* Reduce key entropy from 64 to 40 bits */
90 static void sec_make_40bit(uint8 *key)
91 {
92 key[0] = 0xd1;
93 key[1] = 0x26;
94 key[2] = 0x9e;
95 }
96
97 /* Generate a session key and RC4 keys, given client and server randoms */
98 static void sec_generate_keys(uint8 *client_key, uint8 *server_key,
99 int rc4_key_size)
100 {
101 uint8 session_key[48];
102 uint8 temp_hash[48];
103 uint8 input[48];
104
105 /* Construct input data to hash */
106 memcpy(input, client_key, 24);
107 memcpy(input+24, server_key, 24);
108
109 /* Generate session key - two rounds of sec_hash_48 */
110 sec_hash_48(temp_hash, input, client_key, server_key, 65);
111 sec_hash_48(session_key, temp_hash, client_key, server_key, 88);
112
113 /* Store first 8 bytes of session key, for generating signatures */
114 memcpy(sec_sign_key, session_key, 8);
115
116 /* Generate RC4 keys */
117 sec_hash_16(sec_decrypt_key, &session_key[16], client_key, server_key);
118 sec_hash_16(sec_encrypt_key, &session_key[32], client_key, server_key);
119
120 if (rc4_key_size == 1)
121 {
122 DEBUG("40-bit encryption enabled\n");
123 sec_make_40bit(sec_sign_key);
124 sec_make_40bit(sec_decrypt_key);
125 sec_make_40bit(sec_encrypt_key);
126 rc4_key_len = 8;
127 }
128 else
129 {
130 DEBUG("128-bit encryption enabled\n");
131 rc4_key_len = 16;
132 }
133
134 /* Store first 8 bytes of RC4 keys as update keys */
135 memcpy(sec_decrypt_update_key, sec_decrypt_key, 8);
136 memcpy(sec_encrypt_update_key, sec_encrypt_key, 8);
137
138 /* Initialise RC4 state arrays */
139 RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key);
140 RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key);
141 }
142
143 static uint8 pad_54[40] =
144 {
145 54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,
146 54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54,54
147 };
148
149 static uint8 pad_92[48] =
150 {
151 92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,
152 92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92,92
153 };
154
155 /* Output a uint32 into a buffer (little-endian) */
156 void buf_out_uint32(uint8 *buffer, uint32 value)
157 {
158 buffer[0] = (value) & 0xff;
159 buffer[1] = (value >> 8) & 0xff;
160 buffer[2] = (value >> 16) & 0xff;
161 buffer[3] = (value >> 24) & 0xff;
162 }
163
164 /* Generate a signature hash, using a combination of SHA1 and MD5 */
165 void sec_sign(uint8 *signature, uint8 *session_key, int length,
166 uint8 *data, int datalen)
167 {
168 uint8 shasig[20];
169 uint8 md5sig[16];
170 uint8 lenhdr[4];
171 SHA_CTX sha;
172 MD5_CTX md5;
173
174 buf_out_uint32(lenhdr, datalen);
175
176 SHA1_Init(&sha);
177 SHA1_Update(&sha, session_key, length);
178 SHA1_Update(&sha, pad_54, 40);
179 SHA1_Update(&sha, lenhdr, 4);
180 SHA1_Update(&sha, data, datalen);
181 SHA1_Final(shasig, &sha);
182
183 MD5_Init(&md5);
184 MD5_Update(&md5, session_key, length);
185 MD5_Update(&md5, pad_92, 48);
186 MD5_Update(&md5, shasig, 20);
187 MD5_Final(md5sig, &md5);
188
189 memcpy(signature, md5sig, length);
190 }
191
192 /* Update an encryption key - similar to the signing process */
193 static void sec_update(uint8 *key, uint8 *update_key)
194 {
195 uint8 shasig[20];
196 SHA_CTX sha;
197 MD5_CTX md5;
198 RC4_KEY update;
199
200 SHA1_Init(&sha);
201 SHA1_Update(&sha, update_key, 8);
202 SHA1_Update(&sha, pad_54, 40);
203 SHA1_Update(&sha, key, 8);
204 SHA1_Final(shasig, &sha);
205
206 MD5_Init(&md5);
207 MD5_Update(&md5, update_key, 8);
208 MD5_Update(&md5, pad_92, 48);
209 MD5_Update(&md5, shasig, 20);
210 MD5_Final(key, &md5);
211
212 RC4_set_key(&update, rc4_key_len, key);
213 RC4(&update, rc4_key_len, key, key);
214
215 if (rc4_key_len == 8)
216 sec_make_40bit(key);
217 }
218
219 /* Encrypt data using RC4 */
220 static void sec_encrypt(uint8 *data, int length)
221 {
222 static int use_count;
223
224 if (use_count == 4096)
225 {
226 sec_update(sec_encrypt_key, sec_encrypt_update_key);
227 RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key);
228 use_count = 0;
229 }
230
231 RC4(&rc4_encrypt_key, length, data, data);
232 use_count++;
233 }
234
235 /* Decrypt data using RC4 */
236 static void sec_decrypt(uint8 *data, int length)
237 {
238 static int use_count;
239
240 if (use_count == 4096)
241 {
242 sec_update(sec_decrypt_key, sec_decrypt_update_key);
243 RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key);
244 use_count = 0;
245 }
246
247 RC4(&rc4_decrypt_key, length, data, data);
248 use_count++;
249 }
250
251 /* Read in a NUMBER from a buffer */
252 static void sec_read_number(NUMBER *num, uint8 *buffer, int len)
253 {
254 INT *data = num->n_part;
255 int i, j;
256
257 for (i = 0, j = 0; j < len; i++, j += 2)
258 data[i] = buffer[j] | (buffer[j+1] << 8);
259
260 num->n_len = i;
261 }
262
263 /* Write a NUMBER to a buffer */
264 static void sec_write_number(NUMBER *num, uint8 *buffer, int len)
265 {
266 INT *data = num->n_part;
267 int i, j;
268
269 for (i = 0, j = 0; j < len; i++, j += 2)
270 {
271 buffer[j] = data[i] & 0xff;
272 buffer[j+1] = data[i] >> 8;
273 }
274 }
275
276 /* Perform an RSA public key encryption operation */
277 static void sec_rsa_encrypt(uint8 *out, uint8 *in, int len,
278 uint8 *modulus, uint8 *exponent)
279 {
280 NUMBER data, key;
281
282 /* Set modulus for arithmetic */
283 sec_read_number(&key, modulus, SEC_MODULUS_SIZE);
284 m_init(&key, NULL);
285
286 /* Exponentiate */
287 sec_read_number(&data, in, len);
288 sec_read_number(&key, exponent, SEC_EXPONENT_SIZE);
289 m_exp(&data, &key, &data);
290 sec_write_number(&data, out, SEC_MODULUS_SIZE);
291 }
292
293 /* Initialise secure transport packet */
294 STREAM sec_init(uint32 flags, int maxlen)
295 {
296 int hdrlen;
297 STREAM s;
298
299 hdrlen = (flags & SEC_ENCRYPT) ? 12 : 4;
300 s = mcs_init(maxlen + hdrlen);
301 s_push_layer(s, sec_hdr, hdrlen);
302
303 return s;
304 }
305
306 /* Transmit secure transport packet */
307 void sec_send(STREAM s, uint32 flags)
308 {
309 int datalen;
310
311 s_pop_layer(s, sec_hdr);
312 out_uint32_le(s, flags);
313
314 if (flags & SEC_ENCRYPT)
315 {
316 flags &= ~SEC_ENCRYPT;
317 datalen = s->end - s->p - 8;
318
319 #if RDP_DEBUG
320 DEBUG("Sending encrypted packet:\n");
321 hexdump(s->p+8, datalen);
322 #endif
323
324 sec_sign(s->p, sec_sign_key, 8, s->p+8, datalen);
325 sec_encrypt(s->p+8, datalen);
326 }
327
328 mcs_send(s);
329 }
330
331 /* Transfer the client random to the server */
332 static void sec_establish_key()
333 {
334 uint32 length = SEC_MODULUS_SIZE + SEC_PADDING_SIZE;
335 uint32 flags = SEC_CLIENT_RANDOM;
336 STREAM s;
337
338 s = sec_init(flags, 76);
339
340 out_uint32_le(s, length);
341 out_uint8p(s, sec_crypted_random, SEC_MODULUS_SIZE);
342 out_uint8s(s, SEC_PADDING_SIZE);
343
344 s_mark_end(s);
345 sec_send(s, flags);
346 }
347
348 /* Output connect initial data blob */
349 static void sec_out_mcs_data(STREAM s)
350 {
351 int hostlen = 2 * strlen(hostname);
352
353 out_uint16_be(s, 5); /* unknown */
354 out_uint16_be(s, 0x14);
355 out_uint8(s, 0x7c);
356 out_uint16_be(s, 1);
357
358 out_uint16_be(s, (158 | 0x8000)); /* remaining length */
359
360 out_uint16_be(s, 8); /* length? */
361 out_uint16_be(s, 16);
362 out_uint8(s, 0);
363 out_uint16_le(s, 0xc001);
364 out_uint8(s, 0);
365
366 out_uint32_le(s, 0x61637544); /* "Duca" ?! */
367 out_uint16_be(s, (144 | 0x8000)); /* remaining length */
368
369 /* Client information */
370 out_uint16_le(s, SEC_TAG_CLI_INFO);
371 out_uint16_le(s, 136); /* length */
372 out_uint16_le(s, 1);
373 out_uint16_le(s, 8);
374 out_uint16_le(s, width);
375 out_uint16_le(s, height);
376 out_uint16_le(s, 0xca01);
377 out_uint16_le(s, 0xaa03);
378 out_uint32_le(s, keylayout);
379 out_uint32_le(s, 419); /* client build? we are 419 compatible :-) */
380
381 /* Unicode name of client, padded to 32 bytes */
382 rdp_out_unistr(s, hostname, hostlen);
383 out_uint8s(s, 30-hostlen);
384
385 out_uint32_le(s, 4);
386 out_uint32(s, 0);
387 out_uint32_le(s, 12);
388 out_uint8s(s, 64); /* reserved? 4 + 12 doublewords */
389
390 out_uint16(s, 0xca01);
391 out_uint16(s, 0);
392
393 /* Client encryption settings */
394 out_uint16_le(s, SEC_TAG_CLI_CRYPT);
395 out_uint16(s, 8); /* length */
396 out_uint32_le(s, 1); /* encryption enabled */
397 s_mark_end(s);
398 }
399
400 /* Parse a public key structure */
401 static BOOL sec_parse_public_key(STREAM s, uint8 **modulus, uint8 **exponent)
402 {
403 uint32 magic, modulus_len;
404
405 in_uint32_le(s, magic);
406 if (magic != SEC_RSA_MAGIC)
407 {
408 ERROR("RSA magic 0x%x\n", magic);
409 return False;
410 }
411
412 in_uint32_le(s, modulus_len);
413 if (modulus_len != SEC_MODULUS_SIZE + SEC_PADDING_SIZE)
414 {
415 ERROR("modulus len 0x%x\n", modulus_len);
416 return False;
417 }
418
419 in_uint8s(s, 8); /* modulus_bits, unknown */
420 in_uint8p(s, *exponent, SEC_EXPONENT_SIZE);
421 in_uint8p(s, *modulus, SEC_MODULUS_SIZE);
422 in_uint8s(s, SEC_PADDING_SIZE);
423
424 return s_check(s);
425 }
426
427 /* Parse a crypto information structure */
428 static BOOL sec_parse_crypt_info(STREAM s, uint32 *rc4_key_size,
429 uint8 **server_random, uint8 **modulus, uint8 **exponent)
430 {
431 uint32 crypt_level, random_len, rsa_info_len;
432 uint16 tag, length;
433 uint8 *next_tag, *end;
434
435 in_uint32_le(s, *rc4_key_size); /* 1 = 40-bit, 2 = 128-bit */
436 in_uint32_le(s, crypt_level); /* 1 = low, 2 = medium, 3 = high */
437 in_uint32_le(s, random_len);
438 in_uint32_le(s, rsa_info_len);
439
440 if (random_len != SEC_RANDOM_SIZE)
441 {
442 ERROR("random len %d\n", random_len);
443 return False;
444 }
445
446 in_uint8p(s, *server_random, random_len);
447
448 /* RSA info */
449 end = s->p + rsa_info_len;
450 if (end > s->end)
451 return False;
452
453 in_uint8s(s, 12); /* unknown */
454
455 while (s->p < end)
456 {
457 in_uint16_le(s, tag);
458 in_uint16_le(s, length);
459
460 next_tag = s->p + length;
461
462 switch (tag)
463 {
464 case SEC_TAG_PUBKEY:
465 if (!sec_parse_public_key(s, modulus, exponent))
466 return False;
467
468 break;
469
470 case SEC_TAG_KEYSIG:
471 /* Is this a Microsoft key that we just got? */
472 /* Care factor: zero! */
473 break;
474
475 default:
476 NOTIMP("crypt tag 0x%x\n", tag);
477 }
478
479 s->p = next_tag;
480 }
481
482 return s_check_end(s);
483 }
484
485 /* Process crypto information blob */
486 static void sec_process_crypt_info(STREAM s)
487 {
488 uint8 *server_random, *modulus, *exponent;
489 uint8 client_random[SEC_RANDOM_SIZE];
490 uint32 rc4_key_size;
491
492 if (!sec_parse_crypt_info(s, &rc4_key_size, &server_random,
493 &modulus, &exponent))
494 return;
495
496 /* Generate a client random, and hence determine encryption keys */
497 generate_random(client_random);
498 sec_rsa_encrypt(sec_crypted_random, client_random,
499 SEC_RANDOM_SIZE, modulus, exponent);
500 sec_generate_keys(client_random, server_random, rc4_key_size);
501 }
502
503 /* Process connect response data blob */
504 static void sec_process_mcs_data(STREAM s)
505 {
506 uint16 tag, length;
507 uint8 *next_tag;
508
509 in_uint8s(s, 23); /* header */
510
511 while (s->p < s->end)
512 {
513 in_uint16_le(s, tag);
514 in_uint16_le(s, length);
515
516 if (length <= 4)
517 return;
518
519 next_tag = s->p + length - 4;
520
521 switch (tag)
522 {
523 case SEC_TAG_SRV_INFO:
524 case SEC_TAG_SRV_3:
525 break;
526
527 case SEC_TAG_SRV_CRYPT:
528 sec_process_crypt_info(s);
529 break;
530
531 default:
532 NOTIMP("response tag 0x%x\n", tag);
533 }
534
535 s->p = next_tag;
536 }
537 }
538
539 /* Receive secure transport packet */
540 STREAM sec_recv()
541 {
542 uint32 sec_flags;
543 STREAM s;
544
545 while ((s = mcs_recv()) != NULL)
546 {
547 in_uint32_le(s, sec_flags);
548
549 if (sec_flags & SEC_LICENCE_NEG)
550 {
551 licence_process(s);
552 continue;
553 }
554
555 if (sec_flags & SEC_ENCRYPT)
556 {
557 in_uint8s(s, 8); /* signature */
558 sec_decrypt(s->p, s->end - s->p);
559 }
560
561 return s;
562 }
563
564 return NULL;
565 }
566
567 /* Establish a secure connection */
568 BOOL sec_connect(char *server)
569 {
570 struct stream mcs_data;
571
572 /* We exchange some RDP data during the MCS-Connect */
573 mcs_data.size = 512;
574 mcs_data.p = mcs_data.data = xmalloc(mcs_data.size);
575 sec_out_mcs_data(&mcs_data);
576
577 if (!mcs_connect(server, &mcs_data))
578 return False;
579
580 sec_process_mcs_data(&mcs_data);
581 sec_establish_key();
582 return True;
583 }
584
585 /* Disconnect a connection */
586 void sec_disconnect()
587 {
588 mcs_disconnect();
589 }

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