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
|
/*
Unix SMB/CIFS implementation.
Copyright (C) Andrew Tridgell 2004
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 2 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, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "includes.h"
/*
mark the flags2 field in a packet as signed
*/
static void mark_packet_signed(struct request_context *req)
{
uint16_t flags2;
flags2 = SVAL(req->out.hdr, HDR_FLG2);
flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
SSVAL(req->out.hdr, HDR_FLG2, flags2);
}
/*
calculate the signature for a message
*/
static void calc_signature(uint8 *buffer, size_t length,
DATA_BLOB *mac_key, uint8 signature[8])
{
unsigned char calc_md5_mac[16];
struct MD5Context md5_ctx;
MD5Init(&md5_ctx);
MD5Update(&md5_ctx, mac_key->data, mac_key->length);
MD5Update(&md5_ctx, buffer, length);
MD5Final(calc_md5_mac, &md5_ctx);
memcpy(signature, calc_md5_mac, 8);
}
/*
sign an outgoing packet
*/
void req_sign_packet(struct request_context *req)
{
/* check if we are doing signing on this connection */
if (req->smb->signing.signing_state != SMB_SIGNING_REQUIRED) {
return;
}
SBVAL(req->out.hdr, HDR_SS_FIELD, req->seq_num+1);
mark_packet_signed(req);
calc_signature(req->out.hdr, req->out.size - NBT_HDR_SIZE,
&req->smb->signing.mac_key,
&req->out.hdr[HDR_SS_FIELD]);
}
/*
setup the signing key for a connection. Called after authentication succeeds
in a session setup
*/
void srv_setup_signing(struct server_context *smb,
DATA_BLOB *session_key,
DATA_BLOB *session_response)
{
smb->signing.mac_key = data_blob(NULL,
session_key->length + session_response->length);
memcpy(smb->signing.mac_key.data, session_key->data, session_key->length);
if (session_response->length != 0) {
memcpy(&smb->signing.mac_key.data[session_key->length],
session_response->data,
session_response->length);
}
}
/*
allocate a sequence number to a request
*/
static void req_signing_alloc_seq_num(struct request_context *req)
{
req->seq_num = req->smb->signing.next_seq_num;
/* TODO: we need to handle one-way requests like NTcancel, which
only increment the sequence number by 1 */
if (req->smb->signing.signing_state != SMB_SIGNING_OFF) {
req->smb->signing.next_seq_num += 2;
}
}
/*
check the signature of an incoming packet
*/
BOOL req_signing_check_incoming(struct request_context *req)
{
unsigned char client_md5_mac[8], signature[8];
switch (req->smb->signing.signing_state) {
case SMB_SIGNING_OFF:
return True;
case SMB_SIGNING_SUPPORTED:
if (req->flags2 & FLAGS2_SMB_SECURITY_SIGNATURES) {
req->smb->signing.signing_state = SMB_SIGNING_REQUIRED;
}
return True;
case SMB_SIGNING_REQUIRED:
break;
}
req_signing_alloc_seq_num(req);
/* the first packet isn't checked as the key hasn't been established */
if (req->seq_num == 0) {
return True;
}
/* room enough for the signature? */
if (req->in.size < NBT_HDR_SIZE + HDR_SS_FIELD + 8) {
return False;
}
memcpy(client_md5_mac, req->in.hdr + HDR_SS_FIELD, 8);
SBVAL(req->in.hdr, HDR_SS_FIELD, req->seq_num);
calc_signature(req->in.hdr, req->in.size - NBT_HDR_SIZE,
&req->smb->signing.mac_key,
signature);
if (memcmp(client_md5_mac, signature, 8) != 0) {
DEBUG(2,("Bad SMB signature seq_num=%d\n", (int)req->seq_num));
return False;
}
return True;
}
|
