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/* 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 "util-debug.h"
#include "util-unittest.h"
#include "util-unittest-helper.h"
#include "stream-tcp.h"
#include "app-layer.h"
#include "app-layer-parser.h"
#include "app-layer-ssh.h"
#include "detect-ssh-hassh.h"
#include "rust.h"
#define KEYWORD_NAME "ssh.hassh"
#define KEYWORD_ALIAS "ssh-hassh"
#define KEYWORD_DOC "ssh-keywords.html#hassh"
#define BUFFER_NAME "ssh.hassh"
#define BUFFER_DESC "Ssh Client Fingerprinting For Ssh Clients "
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 *hassh = NULL;
uint32_t b_len = 0;
if (rs_ssh_tx_get_hassh(txv, &hassh, &b_len, flow_flags) != 1)
return NULL;
if (hassh == NULL || b_len == 0) {
SCLogDebug("SSH hassh not set");
return NULL;
}
InspectionBufferSetup(det_ctx, list_id, buffer, hassh, b_len);
InspectionBufferApplyTransforms(buffer, transforms);
}
return buffer;
}
/**
* \brief this function setup the hassh 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 DetectSshHasshSetup(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)) {
SCLogError("hassh support is not enabled");
}
return -2;
}
return 0;
}
static bool DetectSshHasshHashValidateCallback(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 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 (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 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 DetectSshHasshHashSetupCallback(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 hassh keyword.
*/
void DetectSshHasshRegister(void)
{
sigmatch_table[DETECT_AL_SSH_HASSH].name = KEYWORD_NAME;
sigmatch_table[DETECT_AL_SSH_HASSH].alias = KEYWORD_ALIAS;
sigmatch_table[DETECT_AL_SSH_HASSH].desc = BUFFER_NAME " sticky buffer";
sigmatch_table[DETECT_AL_SSH_HASSH].url = "/rules/" KEYWORD_DOC;
sigmatch_table[DETECT_AL_SSH_HASSH].Setup = DetectSshHasshSetup;
sigmatch_table[DETECT_AL_SSH_HASSH].flags |= SIGMATCH_INFO_STICKY_BUFFER | SIGMATCH_NOOPT;
DetectAppLayerMpmRegister2(BUFFER_NAME, SIG_FLAG_TOSERVER, 2,
PrefilterGenericMpmRegister, GetSshData,
ALPROTO_SSH, SshStateBannerDone),
DetectAppLayerInspectEngineRegister2(BUFFER_NAME, ALPROTO_SSH,
SIG_FLAG_TOSERVER, SshStateBannerDone,
DetectEngineInspectBufferGeneric, GetSshData);
DetectBufferTypeSetDescriptionByName(BUFFER_NAME, BUFFER_DESC);
g_ssh_hassh_buffer_id = DetectBufferTypeGetByName(BUFFER_NAME);
DetectBufferTypeRegisterSetupCallback(BUFFER_NAME, DetectSshHasshHashSetupCallback);
DetectBufferTypeRegisterValidateCallback(BUFFER_NAME, DetectSshHasshHashValidateCallback);
}
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