summaryrefslogtreecommitdiff
path: root/source4/auth/gensec/schannel_sign.c
blob: 17a0c17d4193fbad35dec1f9a3dfbbeee9ea126e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
/* 
   Unix SMB/CIFS implementation.

   schannel library code

   Copyright (C) Andrew Tridgell 2004
   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005
   
   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 3 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, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "../lib/crypto/crypto.h"
#include "auth/gensec/gensec.h"
#include "auth/gensec/gensec_proto.h"
#include "auth/gensec/schannel.h"

#define NETSEC_SIGN_SIGNATURE { 0x77, 0x00, 0xff, 0xff, 0xff, 0xff, 0x00, 0x00 }
#define NETSEC_SEAL_SIGNATURE { 0x77, 0x00, 0x7a, 0x00, 0xff, 0xff, 0x00, 0x00 }

/*******************************************************************
 Encode or Decode the sequence number (which is symmetric)
 ********************************************************************/
static void netsec_deal_with_seq_num(struct schannel_state *state,
				     const uint8_t packet_digest[8],
				     uint8_t seq_num[8])
{
	static const uint8_t zeros[4];
	uint8_t sequence_key[16];
	uint8_t digest1[16];

	hmac_md5(state->creds->session_key, zeros, sizeof(zeros), digest1);
	hmac_md5(digest1, packet_digest, 8, sequence_key);
	arcfour_crypt(seq_num, sequence_key, 8);

	state->seq_num++;
}


/*******************************************************************
 Calculate the key with which to encode the data payload 
 ********************************************************************/
static void netsec_get_sealing_key(const uint8_t session_key[16],
				   const uint8_t seq_num[8],
				   uint8_t sealing_key[16]) 
{
	static const uint8_t zeros[4];
	uint8_t digest2[16];
	uint8_t sess_kf0[16];
	int i;

	for (i = 0; i < 16; i++) {
		sess_kf0[i] = session_key[i] ^ 0xf0;
	}
	
	hmac_md5(sess_kf0, zeros, 4, digest2);
	hmac_md5(digest2, seq_num, 8, sealing_key);
}


/*******************************************************************
 Create a digest over the entire packet (including the data), and 
 MD5 it with the session key.
 ********************************************************************/
static void schannel_digest(const uint8_t sess_key[16],
			    const uint8_t netsec_sig[8],
			    const uint8_t *confounder,
			    const uint8_t *data, size_t data_len,
			    uint8_t digest_final[16]) 
{
	uint8_t packet_digest[16];
	static const uint8_t zeros[4];
	struct MD5Context ctx;
	
	MD5Init(&ctx);
	MD5Update(&ctx, zeros, 4);
	MD5Update(&ctx, netsec_sig, 8);
	if (confounder) {
		MD5Update(&ctx, confounder, 8);
	}
	MD5Update(&ctx, data, data_len);
	MD5Final(packet_digest, &ctx);
	
	hmac_md5(sess_key, packet_digest, sizeof(packet_digest), digest_final);
}


/*
  unseal a packet
*/
NTSTATUS schannel_unseal_packet(struct gensec_security *gensec_security, 
				TALLOC_CTX *mem_ctx, 
				uint8_t *data, size_t length, 
				const uint8_t *whole_pdu, size_t pdu_length, 
				const DATA_BLOB *sig)
{
	struct schannel_state *state = talloc_get_type(gensec_security->private_data, struct schannel_state);
	
	uint8_t digest_final[16];
	uint8_t confounder[8];
	uint8_t seq_num[8];
	uint8_t sealing_key[16];
	static const uint8_t netsec_sig[8] = NETSEC_SEAL_SIGNATURE;

	if (sig->length != 32) {
		return NT_STATUS_ACCESS_DENIED;
	}

	memcpy(confounder, sig->data+24, 8);

	RSIVAL(seq_num, 0, state->seq_num);
	SIVAL(seq_num, 4, state->initiator?0:0x80);

	netsec_get_sealing_key(state->creds->session_key, seq_num, sealing_key);
	arcfour_crypt(confounder, sealing_key, 8);
	arcfour_crypt(data, sealing_key, length);

	schannel_digest(state->creds->session_key, 
			netsec_sig, confounder, 
			data, length, digest_final);

	if (memcmp(digest_final, sig->data+16, 8) != 0) {
		dump_data_pw("calc digest:", digest_final, 8);
		dump_data_pw("wire digest:", sig->data+16, 8);
		return NT_STATUS_ACCESS_DENIED;
	}

	netsec_deal_with_seq_num(state, digest_final, seq_num);

	if (memcmp(seq_num, sig->data+8, 8) != 0) {
		dump_data_pw("calc seq num:", seq_num, 8);
		dump_data_pw("wire seq num:", sig->data+8, 8);
		return NT_STATUS_ACCESS_DENIED;
	}

	return NT_STATUS_OK;
}

/*
  check the signature on a packet
*/
NTSTATUS schannel_check_packet(struct gensec_security *gensec_security, 
			       TALLOC_CTX *mem_ctx, 
			       const uint8_t *data, size_t length, 
			       const uint8_t *whole_pdu, size_t pdu_length, 
			       const DATA_BLOB *sig)
{
	struct schannel_state *state = talloc_get_type(gensec_security->private_data, struct schannel_state);

	uint8_t digest_final[16];
	uint8_t seq_num[8];
	static const uint8_t netsec_sig[8] = NETSEC_SIGN_SIGNATURE;

	/* w2k sends just 24 bytes and skip the confounder */
	if (sig->length != 32 && sig->length != 24) {
		return NT_STATUS_ACCESS_DENIED;
	}

	RSIVAL(seq_num, 0, state->seq_num);
	SIVAL(seq_num, 4, state->initiator?0:0x80);

	dump_data_pw("seq_num:\n", seq_num, 8);
	dump_data_pw("sess_key:\n", state->creds->session_key, 16);

	schannel_digest(state->creds->session_key, 
			netsec_sig, NULL, 
			data, length, digest_final);

	netsec_deal_with_seq_num(state, digest_final, seq_num);

	if (memcmp(seq_num, sig->data+8, 8) != 0) {
		dump_data_pw("calc seq num:", seq_num, 8);
		dump_data_pw("wire seq num:", sig->data+8, 8);
		return NT_STATUS_ACCESS_DENIED;
	}

	if (memcmp(digest_final, sig->data+16, 8) != 0) {
		dump_data_pw("calc digest:", digest_final, 8);
		dump_data_pw("wire digest:", sig->data+16, 8);
		return NT_STATUS_ACCESS_DENIED;
	}

	return NT_STATUS_OK;
}


/*
  seal a packet
*/
NTSTATUS schannel_seal_packet(struct gensec_security *gensec_security, 
			      TALLOC_CTX *mem_ctx, 
			      uint8_t *data, size_t length, 
			      const uint8_t *whole_pdu, size_t pdu_length, 
			      DATA_BLOB *sig)
{
	struct schannel_state *state = talloc_get_type(gensec_security->private_data, struct schannel_state);

	uint8_t digest_final[16];
	uint8_t confounder[8];
	uint8_t seq_num[8];
	uint8_t sealing_key[16];
	static const uint8_t netsec_sig[8] = NETSEC_SEAL_SIGNATURE;

	generate_random_buffer(confounder, 8);

	RSIVAL(seq_num, 0, state->seq_num);
	SIVAL(seq_num, 4, state->initiator?0x80:0);

	schannel_digest(state->creds->session_key, 
			netsec_sig, confounder, 
			data, length, digest_final);

	netsec_get_sealing_key(state->creds->session_key, seq_num, sealing_key);
	arcfour_crypt(confounder, sealing_key, 8);
	arcfour_crypt(data, sealing_key, length);

	netsec_deal_with_seq_num(state, digest_final, seq_num);

	(*sig) = data_blob_talloc(mem_ctx, NULL, 32);

	memcpy(sig->data, netsec_sig, 8);
	memcpy(sig->data+8, seq_num, 8);
	memcpy(sig->data+16, digest_final, 8);
	memcpy(sig->data+24, confounder, 8);

	dump_data_pw("signature:", sig->data+ 0, 8);
	dump_data_pw("seq_num  :", sig->data+ 8, 8);
	dump_data_pw("digest   :", sig->data+16, 8);
	dump_data_pw("confound :", sig->data+24, 8);

	return NT_STATUS_OK;
}


/*
  sign a packet
*/
NTSTATUS schannel_sign_packet(struct gensec_security *gensec_security, 
			      TALLOC_CTX *mem_ctx, 
			      const uint8_t *data, size_t length, 
			      const uint8_t *whole_pdu, size_t pdu_length, 
			      DATA_BLOB *sig)
{
	struct schannel_state *state = talloc_get_type(gensec_security->private_data, struct schannel_state);

	uint8_t digest_final[16];
	uint8_t seq_num[8];
	static const uint8_t netsec_sig[8] = NETSEC_SIGN_SIGNATURE;

	RSIVAL(seq_num, 0, state->seq_num);
	SIVAL(seq_num, 4, state->initiator?0x80:0);

	schannel_digest(state->creds->session_key, 
			netsec_sig, NULL, 
			data, length, digest_final);

	netsec_deal_with_seq_num(state, digest_final, seq_num);

	(*sig) = data_blob_talloc(mem_ctx, NULL, 32);

	memcpy(sig->data, netsec_sig, 8);
	memcpy(sig->data+8, seq_num, 8);
	memcpy(sig->data+16, digest_final, 8);
	memset(sig->data+24, 0, 8);

	dump_data_pw("signature:", sig->data+ 0, 8);
	dump_data_pw("seq_num  :", sig->data+ 8, 8);
	dump_data_pw("digest   :", sig->data+16, 8);
	dump_data_pw("confound :", sig->data+24, 8);

	return NT_STATUS_OK;
}