1 /* -*- c-basic-offset: 8 -*-
2 rdesktop: A Remote Desktop Protocol client.
3 Protocol services - RDP encryption and licensing
4 Copyright (C) Matthew Chapman 1999-2002
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.
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.
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.
23 #include <openssl/rc4.h>
24 #include <openssl/md5.h>
25 #include <openssl/sha.h>
26 #include <openssl/bn.h>
27 #include <openssl/x509v3.h>
29 extern char hostname[16];
33 extern BOOL g_encryption;
34 extern BOOL g_licence_issued;
35 extern BOOL g_use_rdp5;
36 extern BOOL g_console_session;
37 extern int g_server_bpp;
38 extern uint16 mcs_userid;
39 extern VCHANNEL g_channels[];
40 extern unsigned int g_num_channels;
42 static int rc4_key_len;
43 static RC4_KEY rc4_decrypt_key;
44 static RC4_KEY rc4_encrypt_key;
45 static RSA *server_public_key;
47 static uint8 sec_sign_key[16];
48 static uint8 sec_decrypt_key[16];
49 static uint8 sec_encrypt_key[16];
50 static uint8 sec_decrypt_update_key[16];
51 static uint8 sec_encrypt_update_key[16];
52 static uint8 sec_crypted_random[SEC_MODULUS_SIZE];
56 uint16 g_server_rdp_version = 0;
59 * General purpose 48-byte transformation, using two 32-byte salts (generally,
60 * a client and server salt) and a global salt value used for padding.
61 * Both SHA1 and MD5 algorithms are used.
64 sec_hash_48(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2, uint8 salt)
72 for (i = 0; i < 3; i++)
74 memset(pad, salt + i, i + 1);
77 SHA1_Update(&sha, pad, i + 1);
78 SHA1_Update(&sha, in, 48);
79 SHA1_Update(&sha, salt1, 32);
80 SHA1_Update(&sha, salt2, 32);
81 SHA1_Final(shasig, &sha);
84 MD5_Update(&md5, in, 48);
85 MD5_Update(&md5, shasig, 20);
86 MD5_Final(&out[i * 16], &md5);
91 * Weaker 16-byte transformation, also using two 32-byte salts, but
92 * only using a single round of MD5.
95 sec_hash_16(uint8 * out, uint8 * in, uint8 * salt1, uint8 * salt2)
100 MD5_Update(&md5, in, 16);
101 MD5_Update(&md5, salt1, 32);
102 MD5_Update(&md5, salt2, 32);
103 MD5_Final(out, &md5);
106 /* Reduce key entropy from 64 to 40 bits */
108 sec_make_40bit(uint8 * key)
115 /* Generate a session key and RC4 keys, given client and server randoms */
117 sec_generate_keys(uint8 * client_key, uint8 * server_key, int rc4_key_size)
119 uint8 session_key[48];
123 /* Construct input data to hash */
124 memcpy(input, client_key, 24);
125 memcpy(input + 24, server_key, 24);
127 /* Generate session key - two rounds of sec_hash_48 */
128 sec_hash_48(temp_hash, input, client_key, server_key, 65);
129 sec_hash_48(session_key, temp_hash, client_key, server_key, 88);
131 /* Store first 16 bytes of session key, for generating signatures */
132 memcpy(sec_sign_key, session_key, 16);
134 /* Generate RC4 keys */
135 sec_hash_16(sec_decrypt_key, &session_key[16], client_key, server_key);
136 sec_hash_16(sec_encrypt_key, &session_key[32], client_key, server_key);
138 if (rc4_key_size == 1)
140 DEBUG(("40-bit encryption enabled\n"));
141 sec_make_40bit(sec_sign_key);
142 sec_make_40bit(sec_decrypt_key);
143 sec_make_40bit(sec_encrypt_key);
148 DEBUG(("rc_4_key_size == %d, 128-bit encryption enabled\n", rc4_key_size));
152 /* Save initial RC4 keys as update keys */
153 memcpy(sec_decrypt_update_key, sec_decrypt_key, 16);
154 memcpy(sec_encrypt_update_key, sec_encrypt_key, 16);
156 /* Initialise RC4 state arrays */
157 RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key);
158 RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key);
162 printf("sec_decrypt_key: ");
163 for (i = 0; i < 16; ++i)
164 printf("0x%02x ", sec_decrypt_key[i]);
167 printf("sec_encrypt_key: ");
168 for (i = 0; i < 16; ++i)
169 printf("0x%02x ", sec_encrypt_key[i]);
174 static uint8 pad_54[40] = {
175 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54,
177 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54,
181 static uint8 pad_92[48] = {
182 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92,
183 92, 92, 92, 92, 92, 92, 92,
184 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92, 92,
185 92, 92, 92, 92, 92, 92, 92
188 /* Output a uint32 into a buffer (little-endian) */
190 buf_out_uint32(uint8 * buffer, uint32 value)
192 buffer[0] = (value) & 0xff;
193 buffer[1] = (value >> 8) & 0xff;
194 buffer[2] = (value >> 16) & 0xff;
195 buffer[3] = (value >> 24) & 0xff;
198 /* Generate a signature hash, using a combination of SHA1 and MD5 */
200 sec_sign(uint8 * signature, int siglen, uint8 * session_key, int keylen, uint8 * data, int datalen)
208 buf_out_uint32(lenhdr, datalen);
211 SHA1_Update(&sha, session_key, keylen);
212 SHA1_Update(&sha, pad_54, 40);
213 SHA1_Update(&sha, lenhdr, 4);
214 SHA1_Update(&sha, data, datalen);
215 SHA1_Final(shasig, &sha);
218 MD5_Update(&md5, session_key, keylen);
219 MD5_Update(&md5, pad_92, 48);
220 MD5_Update(&md5, shasig, 20);
221 MD5_Final(md5sig, &md5);
223 memcpy(signature, md5sig, siglen);
226 /* Update an encryption key - similar to the signing process */
228 sec_update(uint8 * key, uint8 * update_key)
236 SHA1_Update(&sha, update_key, rc4_key_len);
237 SHA1_Update(&sha, pad_54, 40);
238 SHA1_Update(&sha, key, rc4_key_len);
239 SHA1_Final(shasig, &sha);
242 MD5_Update(&md5, update_key, rc4_key_len);
243 MD5_Update(&md5, pad_92, 48);
244 MD5_Update(&md5, shasig, 20);
245 MD5_Final(key, &md5);
247 RC4_set_key(&update, rc4_key_len, key);
248 RC4(&update, rc4_key_len, key, key);
250 if (rc4_key_len == 8)
254 /* Encrypt data using RC4 */
256 sec_encrypt(uint8 * data, int length)
258 static int use_count;
260 if (use_count == 4096)
262 sec_update(sec_decrypt_key, sec_decrypt_update_key);
263 RC4_set_key(&rc4_decrypt_key, rc4_key_len, sec_decrypt_key);
267 RC4(&rc4_decrypt_key, length, data, data);
271 /* Decrypt data using RC4 */
273 sec_decrypt(uint8 * data, int length)
275 static int use_count;
277 if (use_count == 4096)
279 sec_update(sec_encrypt_key, sec_encrypt_update_key);
280 RC4_set_key(&rc4_encrypt_key, rc4_key_len, sec_encrypt_key);
284 RC4(&rc4_encrypt_key, length, data, data);
289 reverse(uint8 * p, int len)
294 for (i = 0, j = len - 1; i < j; i++, j--)
302 /* Perform an RSA public key encryption operation */
304 sec_rsa_encrypt(uint8 * out, uint8 * in, int len, uint8 * modulus, uint8 * exponent)
307 BIGNUM mod, exp, x, y;
308 uint8 inr[SEC_MODULUS_SIZE];
311 reverse(modulus, SEC_MODULUS_SIZE);
312 reverse(exponent, SEC_EXPONENT_SIZE);
313 memcpy(inr, in, len);
322 BN_bin2bn(modulus, SEC_MODULUS_SIZE, &mod);
323 BN_bin2bn(exponent, SEC_EXPONENT_SIZE, &exp);
324 BN_bin2bn(inr, len, &x);
325 BN_mod_exp(&y, &x, &exp, &mod, ctx);
326 outlen = BN_bn2bin(&y, out);
327 reverse(out, outlen);
328 if (outlen < SEC_MODULUS_SIZE)
329 memset(out + outlen, 0, SEC_MODULUS_SIZE - outlen);
338 /* Initialise secure transport packet */
340 sec_init(uint32 flags, int maxlen)
345 /*if (!g_licence_issued) */
346 hdrlen = (flags & SEC_ENCRYPT) ? 12 : 4;
348 hdrlen = (flags & SEC_ENCRYPT) ? 12 : 0; */
349 s = mcs_init(maxlen + hdrlen);
350 s_push_layer(s, sec_hdr, hdrlen);
355 /* Transmit secure transport packet over specified channel */
357 sec_send_to_channel(STREAM s, uint32 flags, uint16 channel)
361 // DEBUG(("sending packet to channel %u\n", channel));
363 s_pop_layer(s, sec_hdr);
364 // if (!g_licence_issued || (flags & SEC_ENCRYPT))
365 out_uint32_le(s, flags);
367 if (flags & SEC_ENCRYPT)
369 flags &= ~SEC_ENCRYPT;
370 datalen = s->end - s->p - 8;
373 DEBUG(("Sending encrypted packet:\n"));
374 hexdump(s->p + 8, datalen);
377 sec_sign(s->p, 8, sec_sign_key, rc4_key_len, s->p + 8, datalen);
378 sec_encrypt(s->p + 8, datalen);
381 mcs_send_to_channel(s, channel);
384 /* Transmit secure transport packet */
387 sec_send(STREAM s, uint32 flags)
389 sec_send_to_channel(s, flags, MCS_GLOBAL_CHANNEL);
393 /* Transfer the client random to the server */
395 sec_establish_key(void)
397 uint32 length = SEC_MODULUS_SIZE + SEC_PADDING_SIZE;
398 uint32 flags = SEC_CLIENT_RANDOM;
401 s = sec_init(flags, 76);
403 out_uint32_le(s, length);
404 out_uint8p(s, sec_crypted_random, SEC_MODULUS_SIZE);
405 out_uint8s(s, SEC_PADDING_SIZE);
411 /* Parse a public key structure */
413 sec_parse_public_key(STREAM s, uint8 ** modulus, uint8 ** exponent)
415 uint32 magic, modulus_len;
417 in_uint32_le(s, magic);
418 if (magic != SEC_RSA_MAGIC)
420 error("RSA magic 0x%x\n", magic);
424 in_uint32_le(s, modulus_len);
425 if (modulus_len != SEC_MODULUS_SIZE + SEC_PADDING_SIZE)
427 error("modulus len 0x%x\n", modulus_len);
431 in_uint8s(s, 8); /* modulus_bits, unknown */
432 in_uint8p(s, *exponent, SEC_EXPONENT_SIZE);
433 in_uint8p(s, *modulus, SEC_MODULUS_SIZE);
434 in_uint8s(s, SEC_PADDING_SIZE);
440 sec_parse_x509_key(X509 * cert)
442 EVP_PKEY *epk = NULL;
443 /* By some reason, Microsoft sets the OID of the Public RSA key to
444 the oid for "MD5 with RSA Encryption" instead of "RSA Encryption"
446 Kudos to Richard Levitte for the following (. intiutive .)
447 lines of code that resets the OID and let's us extract the key. */
448 if (OBJ_obj2nid(cert->cert_info->key->algor->algorithm) == NID_md5WithRSAEncryption)
450 DEBUG_RDP5(("Re-setting algorithm type to RSA in server certificate\n"));
451 cert->cert_info->key->algor->algorithm = OBJ_nid2obj(NID_rsaEncryption);
453 epk = X509_get_pubkey(cert);
456 error("Failed to extract public key from certificate\n");
460 server_public_key = (RSA *) epk->pkey.ptr;
466 /* Parse a crypto information structure */
468 sec_parse_crypt_info(STREAM s, uint32 * rc4_key_size,
469 uint8 ** server_random, uint8 ** modulus, uint8 ** exponent)
471 uint32 crypt_level, random_len, rsa_info_len;
472 uint32 cacert_len, cert_len, flags;
473 X509 *cacert, *server_cert;
475 uint8 *next_tag, *end;
477 in_uint32_le(s, *rc4_key_size); /* 1 = 40-bit, 2 = 128-bit */
478 in_uint32_le(s, crypt_level); /* 1 = low, 2 = medium, 3 = high */
479 if (crypt_level == 0) /* no encryption */
481 in_uint32_le(s, random_len);
482 in_uint32_le(s, rsa_info_len);
484 if (random_len != SEC_RANDOM_SIZE)
486 error("random len %d, expected %d\n", random_len, SEC_RANDOM_SIZE);
490 in_uint8p(s, *server_random, random_len);
493 end = s->p + rsa_info_len;
497 in_uint32_le(s, flags); /* 1 = RDP4-style, 0x80000002 = X.509 */
500 DEBUG_RDP5(("We're going for the RDP4-style encryption\n"));
501 in_uint8s(s, 8); /* unknown */
505 in_uint16_le(s, tag);
506 in_uint16_le(s, length);
508 next_tag = s->p + length;
513 if (!sec_parse_public_key(s, modulus, exponent))
515 DEBUG_RDP5(("Got Public key, RDP4-style\n"));
520 /* Is this a Microsoft key that we just got? */
521 /* Care factor: zero! */
522 /* Actually, it would probably be a good idea to check if the public key is signed with this key, and then store this
523 key as a known key of the hostname. This would prevent some MITM-attacks. */
527 unimpl("crypt tag 0x%x\n", tag);
537 DEBUG_RDP5(("We're going for the RDP5-style encryption\n"));
538 in_uint32_le(s, certcount); /* Number of certificates */
542 error("Server didn't send enough X509 certificates\n");
546 for(; certcount > 2; certcount--)
547 { /* ignore all the certificates between the root and the signing CA */
551 DEBUG_RDP5(("Ignored certs left: %d\n", certcount));
553 in_uint32_le(s, ignorelen);
554 DEBUG_RDP5(("Ignored Certificate length is %d\n", ignorelen));
555 ignorecert = d2i_X509(NULL, &(s->p), ignorelen);
557 if(ignorecert == NULL)
558 { /* XXX: error out? */
559 DEBUG_RDP5(("got a bad cert: this will probably screw up the rest of the communication\n"));
562 #ifdef WITH_DEBUG_RDP5
563 DEBUG_RDP5(("cert #%d (ignored):\n",certcount));
564 X509_print_fp(stdout, ignorecert);
568 /* Do da funky X.509 stuffy
570 "How did I find out about this? I looked up and saw a
571 bright light and when I came to I had a scar on my forehead
572 and knew about X.500"
573 - Peter Gutman in a early version of
574 http://www.cs.auckland.ac.nz/~pgut001/pubs/x509guide.txt
577 in_uint32_le(s, cacert_len);
578 DEBUG_RDP5(("CA Certificate length is %d\n", cacert_len));
579 cacert = d2i_X509(NULL, &(s->p), cacert_len);
580 /* Note: We don't need to move s->p here - d2i_X509 is
581 "kind" enough to do it for us */
584 error("Couldn't load CA Certificate from server\n");
588 /* Currently, we don't use the CA Certificate.
590 *) Verify the server certificate (server_cert) with the
592 *) Store the CA Certificate with the hostname of the
593 server we are connecting to as key, and compare it
594 when we connect the next time, in order to prevent
598 in_uint32_le(s, cert_len);
599 DEBUG_RDP5(("Certificate length is %d\n", cert_len));
600 server_cert = d2i_X509(NULL, &(s->p), cert_len);
601 if (NULL == server_cert)
603 error("Couldn't load Certificate from server\n");
607 in_uint8s(s, 16); /* Padding */
609 /* Note: Verifying the server certificate must be done here,
610 before sec_parse_public_key since we'll have to apply
611 serious violence to the key after this */
613 if (!sec_parse_x509_key(server_cert))
615 DEBUG_RDP5(("Didn't parse X509 correctly\n"));
618 return True; /* There's some garbage here we don't care about */
620 return s_check_end(s);
623 /* Process crypto information blob */
625 sec_process_crypt_info(STREAM s)
627 uint8 *server_random, *modulus, *exponent;
628 uint8 client_random[SEC_RANDOM_SIZE];
630 uint8 inr[SEC_MODULUS_SIZE];
632 if (!sec_parse_crypt_info(s, &rc4_key_size, &server_random, &modulus, &exponent))
634 DEBUG(("Failed to parse crypt info\n"));
638 DEBUG(("Generating client random\n"));
639 /* Generate a client random, and hence determine encryption keys */
640 /* This is what the MS client do: */
641 memset(inr, 0, SEC_RANDOM_SIZE);
642 /* *ARIGL!* Plaintext attack, anyone?
644 generate_random(inr);
645 ..but that generates connection errors now and then (yes,
646 "now and then". Something like 0 to 3 attempts needed before a
647 successful connection. Nice. Not!
650 generate_random(client_random);
651 if (NULL != server_public_key)
652 { /* Which means we should use
653 RDP5-style encryption */
655 memcpy(inr + SEC_RANDOM_SIZE, client_random, SEC_RANDOM_SIZE);
656 reverse(inr + SEC_RANDOM_SIZE, SEC_RANDOM_SIZE);
658 RSA_public_encrypt(SEC_MODULUS_SIZE,
659 inr, sec_crypted_random, server_public_key, RSA_NO_PADDING);
661 reverse(sec_crypted_random, SEC_MODULUS_SIZE);
665 { /* RDP4-style encryption */
666 sec_rsa_encrypt(sec_crypted_random,
667 client_random, SEC_RANDOM_SIZE, modulus, exponent);
669 sec_generate_keys(client_random, server_random, rc4_key_size);
673 /* Process SRV_INFO, find RDP version supported by server */
675 sec_process_srv_info(STREAM s)
677 in_uint16_le(s, g_server_rdp_version);
678 DEBUG_RDP5(("Server RDP version is %d\n", g_server_rdp_version));
679 /* if (1 == g_server_rdp_version)
684 /* Process connect response data blob */
686 sec_process_mcs_data(STREAM s)
692 in_uint8s(s, 21); /* header (T.124 stuff, probably) */
697 while (s->p < s->end)
699 in_uint16_le(s, tag);
700 in_uint16_le(s, length);
705 next_tag = s->p + length - 4;
709 case SEC_TAG_SRV_INFO:
710 sec_process_srv_info(s);
713 case SEC_TAG_SRV_CRYPT:
714 sec_process_crypt_info(s);
717 case SEC_TAG_SRV_CHANNELS:
718 /* FIXME: We should parse this information and
719 use it to map RDP5 channels to MCS
724 unimpl("response tag 0x%x\n", tag);
731 extern unsigned char cacert[];
733 /* Receive secure transport packet */
741 while ((s = mcs_recv(&channel)) != NULL)
743 if (/*g_encryption || !g_licence_issued*/ 1)
745 in_uint32_le(s, sec_flags);
746 printf("sec_flags=%x\n", sec_flags);
748 if (sec_flags & SEC_ENCRYPT)
751 in_uint8s(s, 8); /* signature */
752 sec_decrypt(s->p, s->end - s->p);
755 if (sec_flags & SEC_LICENCE_NEG)
757 printf("SEC_LICENSE_NEG unknown\n");
758 //licence_process(s);
762 if (sec_flags & SEC_LOGON_INFO)
764 printf("Received logon packet!\n");
765 rdp_get_logon_info(s);
771 s = sec_init(g_encryption ? SEC_ENCRYPT : 0, 10);
772 out_uint16_le(s, 10);
773 out_uint16_le(s, (RDP_PDU_DEMAND_ACTIVE | 0x10));
774 out_uint16_le(s, 1001);
776 out_uint32_le(s, 0x103ea);
778 sec_send(s, g_encryption ? SEC_ENCRYPT : 0);
784 if (sec_flags & SEC_CLIENT_RANDOM) {
786 uint8 inr[SEC_MODULUS_SIZE];
789 printf("Receiving the client random!\n");
790 in_uint32_le(s, length);
791 if (length != SEC_MODULUS_SIZE + SEC_PADDING_SIZE) {
792 error("Client random was wrong size, %u bytes\n", length);
794 in_uint8a(s, sec_crypted_random, SEC_MODULUS_SIZE);
795 in_uint8s(s, SEC_PADDING_SIZE);
796 if (!s_check_end(s)) {
797 error("Junk after client random\n");
800 reverse(sec_crypted_random, SEC_MODULUS_SIZE);
802 RSA_private_decrypt(SEC_MODULUS_SIZE, sec_crypted_random, inr, privkey, RSA_NO_PADDING);
804 reverse(inr + SEC_RANDOM_SIZE, SEC_RANDOM_SIZE);
806 printf("Unencrypted client random: ");
807 for (i = 0; i < SEC_RANDOM_SIZE; ++i) {
808 printf("0x%x ", inr[i + SEC_RANDOM_SIZE]);
812 // now we can generate the keys
813 sec_generate_keys(inr + SEC_RANDOM_SIZE, cacert, 1);
818 printf("Received MCS data on ch %u\n", channel);
819 if (channel != MCS_GLOBAL_CHANNEL)
821 channel_process(s, channel);
831 /* Disconnect a connection */