/* 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 */ #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); }