summaryrefslogtreecommitdiff
path: root/libcli/smb/smb2_signing.c
blob: 43c9ba5c1c00a85092a8ef8534efc29efc90e9a3 (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
/*
   Unix SMB/CIFS implementation.
   SMB2 signing

   Copyright (C) Stefan Metzmacher 2009

   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 "system/filesys.h"
#include "../libcli/smb/smb_common.h"
#include "../lib/crypto/crypto.h"

NTSTATUS smb2_signing_sign_pdu(DATA_BLOB signing_key,
			       enum protocol_types protocol,
			       struct iovec *vector,
			       int count)
{
	uint8_t *hdr;
	uint64_t session_id;
	uint8_t res[16];
	int i;

	if (count < 2) {
		return NT_STATUS_INVALID_PARAMETER;
	}

	if (vector[0].iov_len != SMB2_HDR_BODY) {
		return NT_STATUS_INVALID_PARAMETER;
	}

	hdr = (uint8_t *)vector[0].iov_base;

	session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
	if (session_id == 0) {
		/*
		 * do not sign messages with a zero session_id.
		 * See MS-SMB2 3.2.4.1.1
		 */
		return NT_STATUS_OK;
	}

	if (signing_key.length == 0) {
		DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
			 (unsigned)signing_key.length));
		return NT_STATUS_ACCESS_DENIED;
	}

	memset(hdr + SMB2_HDR_SIGNATURE, 0, 16);

	SIVAL(hdr, SMB2_HDR_FLAGS, IVAL(hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);

	if (protocol >= PROTOCOL_SMB2_24) {
		struct aes_cmac_128_context ctx;
		uint8_t key[AES_BLOCK_SIZE];

		ZERO_STRUCT(key);
		memcpy(key, signing_key.data, MIN(signing_key.length, 16));

		aes_cmac_128_init(&ctx, key);
		for (i=0; i < count; i++) {
			aes_cmac_128_update(&ctx,
					(const uint8_t *)vector[i].iov_base,
					vector[i].iov_len);
		}
		aes_cmac_128_final(&ctx, res);
	} else {
		struct HMACSHA256Context m;
		uint8_t digest[SHA256_DIGEST_LENGTH];

		ZERO_STRUCT(m);
		hmac_sha256_init(signing_key.data, MIN(signing_key.length, 16), &m);
		for (i=0; i < count; i++) {
			hmac_sha256_update((const uint8_t *)vector[i].iov_base,
					   vector[i].iov_len, &m);
		}
		hmac_sha256_final(digest, &m);
		memcpy(res, digest, 16);
	}
	DEBUG(5,("signed SMB2 message\n"));

	memcpy(hdr + SMB2_HDR_SIGNATURE, res, 16);

	return NT_STATUS_OK;
}

NTSTATUS smb2_signing_check_pdu(DATA_BLOB signing_key,
				enum protocol_types protocol,
				const struct iovec *vector,
				int count)
{
	const uint8_t *hdr;
	const uint8_t *sig;
	uint64_t session_id;
	uint8_t res[16];
	static const uint8_t zero_sig[16] = { 0, };
	int i;

	if (count < 2) {
		return NT_STATUS_INVALID_PARAMETER;
	}

	if (vector[0].iov_len != SMB2_HDR_BODY) {
		return NT_STATUS_INVALID_PARAMETER;
	}

	hdr = (const uint8_t *)vector[0].iov_base;

	session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
	if (session_id == 0) {
		/*
		 * do not sign messages with a zero session_id.
		 * See MS-SMB2 3.2.4.1.1
		 */
		return NT_STATUS_OK;
	}

	if (signing_key.length == 0) {
		/* we don't have the session key yet */
		return NT_STATUS_OK;
	}

	sig = hdr+SMB2_HDR_SIGNATURE;

	if (protocol >= PROTOCOL_SMB2_24) {
		struct aes_cmac_128_context ctx;
		uint8_t key[AES_BLOCK_SIZE];

		ZERO_STRUCT(key);
		memcpy(key, signing_key.data, MIN(signing_key.length, 16));

		aes_cmac_128_init(&ctx, key);
		aes_cmac_128_update(&ctx, hdr, SMB2_HDR_SIGNATURE);
		aes_cmac_128_update(&ctx, zero_sig, 16);
		for (i=1; i < count; i++) {
			aes_cmac_128_update(&ctx,
					(const uint8_t *)vector[i].iov_base,
					vector[i].iov_len);
		}
		aes_cmac_128_final(&ctx, res);
	} else {
		struct HMACSHA256Context m;
		uint8_t digest[SHA256_DIGEST_LENGTH];

		ZERO_STRUCT(m);
		hmac_sha256_init(signing_key.data, MIN(signing_key.length, 16), &m);
		hmac_sha256_update(hdr, SMB2_HDR_SIGNATURE, &m);
		hmac_sha256_update(zero_sig, 16, &m);
		for (i=1; i < count; i++) {
			hmac_sha256_update((const uint8_t *)vector[i].iov_base,
					   vector[i].iov_len, &m);
		}
		hmac_sha256_final(digest, &m);
		memcpy(res, digest, 16);
	}

	if (memcmp(res, sig, 16) != 0) {
		DEBUG(0,("Bad SMB2 signature for message\n"));
		dump_data(0, sig, 16);
		dump_data(0, res, 16);
		return NT_STATUS_ACCESS_DENIED;
	}

	return NT_STATUS_OK;
}

void smb2_key_derivation(const uint8_t *KI, size_t KI_len,
			 const uint8_t *Label, size_t Label_len,
			 const uint8_t *Context, size_t Context_len,
			 uint8_t KO[16])
{
	struct HMACSHA256Context ctx;
	uint8_t buf[4];
	static const uint8_t zero = 0;
	uint8_t digest[SHA256_DIGEST_LENGTH];
	uint32_t i = 1;
	uint32_t L = 128;

	/*
	 * a simplified version of
	 * "NIST Special Publication 800-108" section 5.1
	 * using hmac-sha256.
	 */
	hmac_sha256_init(KI, KI_len, &ctx);

	RSIVAL(buf, 0, i);
	hmac_sha256_update(buf, sizeof(buf), &ctx);
	hmac_sha256_update(Label, Label_len, &ctx);
	hmac_sha256_update(&zero, 1, &ctx);
	hmac_sha256_update(Context, Context_len, &ctx);
	RSIVAL(buf, 0, L);
	hmac_sha256_update(buf, sizeof(buf), &ctx);

	hmac_sha256_final(digest, &ctx);

	memcpy(KO, digest, 16);
}