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
|
/* Copyright (C) 2007-2020 Open Information Security Foundation
*
* You can copy, redistribute or modify this Program under the terms of
* the GNU General Public License version 2 as published by the Free
* Software Foundation.
*
* 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
* version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/**
* \file
*
* \author Vadym Malakhatko <v.malakhatko@sirinsoftware.com>
*/
#include "suricata-common.h"
#include "threads.h"
#include "decode.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-content.h"
#include "detect-engine.h"
#include "detect-engine-mpm.h"
#include "detect-engine-state.h"
#include "detect-engine-prefilter.h"
#include "flow.h"
#include "flow-var.h"
#include "flow-util.h"
#include "stream-tcp.h"
#include "util-debug.h"
#include "util-unittest.h"
#include "util-unittest-helper.h"
#include "app-layer.h"
#include "app-layer-parser.h"
#include "app-layer-ssh.h"
#include "detect-ssh-hassh-server.h"
#include "rust.h"
#define KEYWORD_NAME "ssh.hassh.server"
#define KEYWORD_ALIAS "ssh-hassh-server"
#define KEYWORD_DOC "ssh-keywords.html#ssh.hassh.server"
#define BUFFER_NAME "ssh.hassh.server"
#define BUFFER_DESC "Ssh Client Fingerprinting For Ssh Servers"
static int g_ssh_hassh_buffer_id = 0;
static InspectionBuffer *GetSshData(DetectEngineThreadCtx *det_ctx,
const DetectEngineTransforms *transforms, Flow *_f,
const uint8_t flow_flags, void *txv, const int list_id)
{
SCEnter();
InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
if (buffer->inspect == NULL) {
const uint8_t *hasshServer = NULL;
uint32_t b_len = 0;
if (rs_ssh_tx_get_hassh(txv, &hasshServer, &b_len, flow_flags) != 1)
return NULL;
if (hasshServer == NULL || b_len == 0) {
SCLogDebug("SSH hassh not set");
return NULL;
}
InspectionBufferSetup(det_ctx, list_id, buffer, hasshServer, b_len);
InspectionBufferApplyTransforms(buffer, transforms);
}
return buffer;
}
/**
* \brief this function setup the ssh.hassh.server modifier keyword used in the rule
*
* \param de_ctx Pointer to the Detection Engine Context
* \param s Pointer to the Signature to which the current keyword belongs
* \param str Should hold an empty string always
*
* \retval 0 On success
* \retval -1 On failure
* \retval -2 on failure that should be silent after the first
*/
static int DetectSshHasshServerSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg)
{
if (DetectBufferSetActiveList(de_ctx, s, g_ssh_hassh_buffer_id) < 0)
return -1;
if (DetectSignatureSetAppProto(s, ALPROTO_SSH) < 0)
return -1;
/* try to enable Hassh */
rs_ssh_enable_hassh();
/* Check if Hassh is disabled */
if (!RunmodeIsUnittests() && !rs_ssh_hassh_is_enabled()) {
if (!SigMatchSilentErrorEnabled(de_ctx, DETECT_AL_SSH_HASSH_SERVER)) {
SCLogError("hassh support is not enabled");
}
return -2;
}
return 0;
}
static bool DetectSshHasshServerHashValidateCallback(const Signature *s, const char **sigerror)
{
for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
if (s->init_data->buffers[x].id != (uint32_t)g_ssh_hassh_buffer_id)
continue;
const SigMatch *sm = s->init_data->buffers[x].head;
for (; sm != NULL; sm = sm->next) {
if (sm->type != DETECT_CONTENT)
continue;
const DetectContentData *cd = (DetectContentData *)sm->ctx;
if (cd->flags & DETECT_CONTENT_NOCASE) {
*sigerror = "ssh.hassh.server should not be used together with "
"nocase, since the rule is automatically "
"lowercased anyway which makes nocase redundant.";
SCLogWarning("rule %u: %s", s->id, *sigerror);
}
if (cd->content_len != 32) {
*sigerror = "Invalid length of the specified ssh.hassh.server (should "
"be 32 characters long). This rule will therefore "
"never match.";
SCLogWarning("rule %u: %s", s->id, *sigerror);
return false;
}
for (size_t i = 0; i < cd->content_len; ++i) {
if (!isxdigit(cd->content[i])) {
*sigerror = "Invalid ssh.hassh.server string (should be string of hexadecimal "
"characters)."
"This rule will therefore never match.";
SCLogWarning("rule %u: %s", s->id, *sigerror);
return false;
}
}
}
}
return true;
}
static void DetectSshHasshServerHashSetupCallback(const DetectEngineCtx *de_ctx,
Signature *s)
{
for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
if (s->init_data->buffers[x].id != (uint32_t)g_ssh_hassh_buffer_id)
continue;
SigMatch *sm = s->init_data->buffers[x].head;
for (; sm != NULL; sm = sm->next) {
if (sm->type != DETECT_CONTENT)
continue;
DetectContentData *cd = (DetectContentData *)sm->ctx;
uint32_t u;
for (u = 0; u < cd->content_len; u++) {
if (isupper(cd->content[u])) {
cd->content[u] = u8_tolower(cd->content[u]);
}
}
SpmDestroyCtx(cd->spm_ctx);
cd->spm_ctx =
SpmInitCtx(cd->content, cd->content_len, 1, de_ctx->spm_global_thread_ctx);
}
}
}
/**
* \brief Registration function for hasshServer keyword.
*/
void DetectSshHasshServerRegister(void)
{
sigmatch_table[DETECT_AL_SSH_HASSH_SERVER].name = KEYWORD_NAME;
sigmatch_table[DETECT_AL_SSH_HASSH_SERVER].alias = KEYWORD_ALIAS;
sigmatch_table[DETECT_AL_SSH_HASSH_SERVER].desc = BUFFER_NAME " sticky buffer";
sigmatch_table[DETECT_AL_SSH_HASSH_SERVER].url = "/rules/" KEYWORD_DOC;
sigmatch_table[DETECT_AL_SSH_HASSH_SERVER].Setup = DetectSshHasshServerSetup;
sigmatch_table[DETECT_AL_SSH_HASSH_SERVER].flags |= SIGMATCH_INFO_STICKY_BUFFER | SIGMATCH_NOOPT;
DetectAppLayerMpmRegister2(BUFFER_NAME, SIG_FLAG_TOCLIENT, 2,
PrefilterGenericMpmRegister, GetSshData,
ALPROTO_SSH, SshStateBannerDone);
DetectAppLayerInspectEngineRegister2(BUFFER_NAME, ALPROTO_SSH,
SIG_FLAG_TOCLIENT, SshStateBannerDone,
DetectEngineInspectBufferGeneric, GetSshData);
DetectBufferTypeSetDescriptionByName(BUFFER_NAME, BUFFER_DESC);
g_ssh_hassh_buffer_id = DetectBufferTypeGetByName(BUFFER_NAME);
DetectBufferTypeRegisterSetupCallback(BUFFER_NAME, DetectSshHasshServerHashSetupCallback);
DetectBufferTypeRegisterValidateCallback(BUFFER_NAME, DetectSshHasshServerHashValidateCallback);
}
|
