/* Copyright (C) 2017-2020 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 Eric Leblond * * Match on ftp command used to trigger a ftp data transfer */ #include "suricata-common.h" #include "util-unittest.h" #include "detect-parse.h" #include "detect-engine.h" #include "detect-engine-state.h" #include "app-layer-ftp.h" #include "detect-ftpdata.h" /** * \brief Regex for parsing our keyword options */ #define PARSE_REGEX "^\\s*(stor|retr)\\s*$" static DetectParseRegex parse_regex; /* Prototypes of functions registered in DetectFtpdataRegister below */ static int DetectFtpdataMatch(DetectEngineThreadCtx *, Flow *, uint8_t, void *, void *, const Signature *, const SigMatchCtx *); static int DetectFtpdataSetup (DetectEngineCtx *, Signature *, const char *); static void DetectFtpdataFree (DetectEngineCtx *, void *); #ifdef UNITTESTS static void DetectFtpdataRegisterTests (void); #endif static int g_ftpdata_buffer_id = 0; /** * \brief Registration function for ftpcommand: keyword * * This function is called once in the 'lifetime' of the engine. */ void DetectFtpdataRegister(void) { /* keyword name: this is how the keyword is used in a rule */ sigmatch_table[DETECT_FTPDATA].name = "ftpdata_command"; /* description: listed in "suricata --list-keywords=all" */ sigmatch_table[DETECT_FTPDATA].desc = "match FTP command triggering a FTP data channel"; sigmatch_table[DETECT_FTPDATA].url = "/rules/ftp-keywords.html#ftpdata-command"; sigmatch_table[DETECT_FTPDATA].AppLayerTxMatch = DetectFtpdataMatch; /* setup function is called during signature parsing, when the ftpcommand * keyword is encountered in the rule */ sigmatch_table[DETECT_FTPDATA].Setup = DetectFtpdataSetup; /* free function is called when the detect engine is freed. Normally at * shutdown, but also during rule reloads. */ sigmatch_table[DETECT_FTPDATA].Free = DetectFtpdataFree; /* registers unittests into the system */ #ifdef UNITTESTS sigmatch_table[DETECT_FTPDATA].RegisterTests = DetectFtpdataRegisterTests; #endif DetectAppLayerInspectEngineRegister2("ftpdata_command", ALPROTO_FTPDATA, SIG_FLAG_TOSERVER, 0, DetectEngineInspectGenericList, NULL); DetectAppLayerInspectEngineRegister2("ftpdata_command", ALPROTO_FTPDATA, SIG_FLAG_TOCLIENT, 0, DetectEngineInspectGenericList, NULL); g_ftpdata_buffer_id = DetectBufferTypeGetByName("ftpdata_command"); /* set up the PCRE for keyword parsing */ DetectSetupParseRegexes(PARSE_REGEX, &parse_regex); } /** * \brief This function is used to check matches from the FTP App Layer Parser * * \param t pointer to thread vars * \param det_ctx pointer to the pattern matcher thread * \param p pointer to the current packet * \param m pointer to the sigmatch * \retval 0 no match * \retval 1 match */ static int DetectFtpdataMatch(DetectEngineThreadCtx *det_ctx, Flow *f, uint8_t flags, void *state, void *txv, const Signature *s, const SigMatchCtx *m) { const DetectFtpdataData *ftpcommandd = (const DetectFtpdataData *) m; const FtpDataState *ftp_state = (const FtpDataState *)state; if (ftp_state == NULL) return 0; if (ftpcommandd->command == ftp_state->command) { /* Only match if the flow is in the good direction */ if ((flags & STREAM_TOSERVER) && (ftpcommandd->command == FTP_COMMAND_RETR)) { return 0; } else if ((flags & STREAM_TOCLIENT) && (ftpcommandd->command == FTP_COMMAND_STOR)) { return 0; } return 1; } return 0; } /** * \brief This function is used to parse ftpcommand options passed via ftpcommand: keyword * * \param ftpcommandstr Pointer to the user provided ftpcommand options * * \retval ftpcommandd pointer to DetectFtpdataData on success * \retval NULL on failure */ static DetectFtpdataData *DetectFtpdataParse(const char *ftpcommandstr) { DetectFtpdataData *ftpcommandd = NULL; char arg1[5] = ""; size_t pcre2len; pcre2_match_data *match = NULL; int ret = DetectParsePcreExec(&parse_regex, &match, ftpcommandstr, 0, 0); if (ret != 2) { SCLogError("parse error, ret %" PRId32 "", ret); goto error; } pcre2len = sizeof(arg1); int res = pcre2_substring_copy_bynumber(match, 1, (PCRE2_UCHAR8 *)arg1, &pcre2len); if (res < 0) { SCLogError("pcre2_substring_copy_bynumber failed"); goto error; } SCLogDebug("Arg1 \"%s\"", arg1); ftpcommandd = SCMalloc(sizeof (DetectFtpdataData)); if (unlikely(ftpcommandd == NULL)) goto error; if (!strcmp(arg1, "stor")) { ftpcommandd->command = FTP_COMMAND_STOR; } else if (!strcmp(arg1, "retr")) { ftpcommandd->command = FTP_COMMAND_RETR; } else { SCLogError("Invalid command value"); goto error; } pcre2_match_data_free(match); return ftpcommandd; error: if (match) { pcre2_match_data_free(match); } if (ftpcommandd) SCFree(ftpcommandd); return NULL; } /** * \brief parse the options from the 'ftpcommand' keyword in the rule into * the Signature data structure. * * \param de_ctx pointer to the Detection Engine Context * \param s pointer to the Current Signature * \param str pointer to the user provided ftpcommand options * * \retval 0 on Success * \retval -1 on Failure */ static int DetectFtpdataSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str) { if (DetectSignatureSetAppProto(s, ALPROTO_FTPDATA) != 0) return -1; DetectFtpdataData *ftpcommandd = DetectFtpdataParse(str); if (ftpcommandd == NULL) return -1; SigMatch *sm = SigMatchAlloc(); if (sm == NULL) { DetectFtpdataFree(de_ctx, ftpcommandd); return -1; } sm->type = DETECT_FTPDATA; sm->ctx = (void *)ftpcommandd; SigMatchAppendSMToList(s, sm, g_ftpdata_buffer_id); return 0; } /** * \brief this function will free memory associated with DetectFtpdataData * * \param ptr pointer to DetectFtpdataData */ static void DetectFtpdataFree(DetectEngineCtx *de_ctx, void *ptr) { DetectFtpdataData *ftpcommandd = (DetectFtpdataData *)ptr; /* do more specific cleanup here, if needed */ SCFree(ftpcommandd); } #ifdef UNITTESTS static int DetectFtpdataParseTest01(void) { DetectFtpdataData *ftpcommandd = DetectFtpdataParse("stor"); FAIL_IF_NULL(ftpcommandd); FAIL_IF(!(ftpcommandd->command == FTP_COMMAND_STOR)); DetectFtpdataFree(NULL, ftpcommandd); PASS; } static int DetectFtpdataSignatureTest01(void) { DetectEngineCtx *de_ctx = DetectEngineCtxInit(); FAIL_IF_NULL(de_ctx); Signature *sig = DetectEngineAppendSig(de_ctx, "alert ip any any -> any any (ftpdata_command:stor; sid:1; rev:1;)"); FAIL_IF_NULL(sig); sig = DetectEngineAppendSig(de_ctx, "alert ip any any -> any any (ftpdata_command:retr; sid:2; rev:1;)"); FAIL_IF_NULL(sig); sig = DetectEngineAppendSig(de_ctx, "alert ip any any -> any any (ftpdata_command:xxx; sid:3; rev:1;)"); FAIL_IF_NOT_NULL(sig); DetectEngineCtxFree(de_ctx); PASS; } /** * \brief this function registers unit tests for DetectFtpdata */ static void DetectFtpdataRegisterTests(void) { UtRegisterTest("DetectFtpdataParseTest01", DetectFtpdataParseTest01); UtRegisterTest("DetectFtpdataSignatureTest01", DetectFtpdataSignatureTest01); } #endif /* UNITTESTS */