mirror of https://github.com/OISF/suricata
FragOffset Rule Keyword
Breno Silva
15 years ago
committed by
Victor Julien
parent
f96511a8b1
commit
7e299834d2
@ -0,0 +1,356 @@
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/* Copyright (c) 2009 Open Information Security Foundation */
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/** \file
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* \author Breno Silva <breno.silva@gmail.com>
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*/
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#include "suricata-common.h"
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#include "debug.h"
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#include "decode.h"
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#include "decode-ipv4.h"
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#include "decode-ipv6.h"
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#include "detect.h"
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#include "detect-fragoffset.h"
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#include "util-byte.h"
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#include "util-unittest.h"
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#include "util-debug.h"
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#define PARSE_REGEX "^\\s*(?:(<|>))?\\s*([0-9]+)"
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static pcre *parse_regex;
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static pcre_extra *parse_regex_study;
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int DetectFragOffsetMatch(ThreadVars *, DetectEngineThreadCtx *, Packet *, Signature *, SigMatch *);
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int DetectFragOffsetSetup(DetectEngineCtx *, Signature *, SigMatch *, char *);
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void DetectFragOffsetRegisterTests(void);
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void DetectFragOffsetFree(void *);
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/**
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* \brief Registration function for fragoffset
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*/
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void DetectFragOffsetRegister (void) {
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sigmatch_table[DETECT_FRAGOFFSET].name = "fragoffset";
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sigmatch_table[DETECT_FRAGOFFSET].Match = DetectFragOffsetMatch;
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sigmatch_table[DETECT_FRAGOFFSET].Setup = DetectFragOffsetSetup;
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sigmatch_table[DETECT_FRAGOFFSET].Free = DetectFragOffsetFree;
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sigmatch_table[DETECT_FRAGOFFSET].RegisterTests = DetectFragOffsetRegisterTests;
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const char *eb;
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int eo;
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int opts = 0;
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parse_regex = pcre_compile(PARSE_REGEX, opts, &eb, &eo, NULL);
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if (parse_regex == NULL) {
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SCLogError(SC_PCRE_COMPILE_FAILED,"pcre compile of \"%s\" failed at offset %" PRId32 ": %s", PARSE_REGEX, eo, eb);
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goto error;
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}
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parse_regex_study = pcre_study(parse_regex, 0, &eb);
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if (eb != NULL) {
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SCLogError(SC_PCRE_STUDY_FAILED,"pcre study failed: %s", eb);
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goto error;
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}
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return;
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error:
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return;
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}
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/**
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* \brief This function is used to match fragoffset rule option set on a packet
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*
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* \param t pointer to thread vars
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* \param det_ctx pointer to the pattern matcher thread
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* \param p pointer to the current packet
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* \param m pointer to the sigmatch that we will cast into DetectFragOffsetData
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*
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* \retval 0 no match
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* \retval 1 match
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* \retval -1 No frag offset is set
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*
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*/
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int DetectFragOffsetMatch (ThreadVars *t, DetectEngineThreadCtx *det_ctx, Packet *p, Signature *s, SigMatch *m) {
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uint16_t frag = 0;
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DetectFragOffsetData *fragoff = (DetectFragOffsetData *)m->ctx;
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if (PKT_IS_IPV4(p)) {
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frag = IPV4_GET_IPOFFSET(p);
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} else if (PKT_IS_IPV6(p)) {
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if(IPV6_EXTHDR_FH(p)) {
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frag = IPV6_EXTHDR_GET_FH_OFFSET(p);
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} else {
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return -1;
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}
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} else {
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SCLogDebug("No IPv4 or IPv6 packet");
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return -1;
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}
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switch (fragoff->mode) {
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case FRAG_LESS:
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if (frag < fragoff->frag_off) return 1;
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break;
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case FRAG_MORE:
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if (frag > fragoff->frag_off) return 1;
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break;
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default:
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if (frag == fragoff->frag_off) return 1;
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}
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return 0;
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}
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/**
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* \brief This function is used to parse fragoffset option passed via fragoffset: keyword
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*
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* \param fragoffsetstr Pointer to the user provided fragoffset options
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*
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* \retval fragoff pointer to DetectFragOffsetData on success
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* \retval NULL on failure
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*/
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DetectFragOffsetData *DetectFragOffsetParse (char *fragoffsetstr) {
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DetectFragOffsetData *fragoff = NULL;
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char *substr[2] = {NULL, NULL};
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#define MAX_SUBSTRINGS 30
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int ret = 0, res = 0;
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int ov[MAX_SUBSTRINGS];
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int i;
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const char *str_ptr;
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char *mode = NULL;
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ret = pcre_exec(parse_regex, parse_regex_study, fragoffsetstr, strlen(fragoffsetstr), 0, 0, ov, MAX_SUBSTRINGS);
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if (ret < 1 || ret > 4) {
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SCLogError(SC_PCRE_MATCH_FAILED,"Parse error %s", fragoffsetstr);
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goto error;
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}
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for (i = 1; i < ret; i++) {
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res = pcre_get_substring((char *)fragoffsetstr, ov, MAX_SUBSTRINGS, i, &str_ptr);
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if (res < 0) {
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SCLogError(SC_PCRE_GET_SUBSTRING_FAILED,"pcre_get_substring failed");
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goto error;
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}
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substr[i-1] = (char *)str_ptr;
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}
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fragoff = malloc(sizeof(DetectFragOffsetData));
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if (fragoff == NULL) {
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SCLogError(SC_ERR_MEM_ALLOC, "Error allocating memory");
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goto error;
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}
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fragoff->frag_off = 0;
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fragoff->mode = 0;
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mode = substr[0];
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if(mode != NULL) {
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while(*mode != '\0') {
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switch(*mode) {
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case '>':
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fragoff->mode = FRAG_MORE;
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break;
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case '<':
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fragoff->mode = FRAG_LESS;
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break;
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}
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mode++;
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}
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}
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ByteExtractStringUint16(&fragoff->frag_off, 10, 0, substr[1]);
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for (i = 0; i < 2; i++) {
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if (substr[i] != NULL) free(substr[i]);
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}
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return fragoff;
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error:
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for (i = 0; i < 2; i++) {
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if (substr[i] != NULL) free(substr[i]);
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}
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if (fragoff != NULL) DetectFragOffsetFree(fragoff);
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return NULL;
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}
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/**
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* \brief this function is used to add the parsed fragoffset data into the current signature
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*
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* \param de_ctx pointer to the Detection Engine Context
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* \param s pointer to the Current Signature
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* \param m pointer to the Current SigMatch
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* \param fragoffsetstr pointer to the user provided fragoffset option
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*
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* \retval 0 on Success
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* \retval -1 on Failure
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*/
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int DetectFragOffsetSetup (DetectEngineCtx *de_ctx, Signature *s, SigMatch *m, char *fragoffsetstr) {
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DetectFragOffsetData *fragoff = NULL;
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SigMatch *sm = NULL;
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fragoff = DetectFragOffsetParse(fragoffsetstr);
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if (fragoff == NULL) goto error;
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sm = SigMatchAlloc();
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if (sm == NULL) goto error;
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sm->type = DETECT_FRAGOFFSET;
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sm->ctx = (void *)fragoff;
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SigMatchAppend(s, m, sm);
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return 0;
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error:
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if (fragoff != NULL) DetectFragOffsetFree(fragoff);
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if (sm != NULL) free(sm);
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return -1;
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}
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/**
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* \brief this function will free memory associated with DetectFragOffsetData
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*
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* \param ptr pointer to DetectFragOffsetData
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*/
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void DetectFragOffsetFree (void *ptr) {
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DetectFragOffsetData *fragoff = (DetectFragOffsetData *)ptr;
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free(fragoff);
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}
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#ifdef UNITTESTS
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#include "detect-parse.h"
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#include "detect-engine.h"
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#include "detect-engine-mpm.h"
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/**
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* \test DetectFragOffsetParseTest01 is a test for setting a valid fragoffset value
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*/
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int DetectFragOffsetParseTest01 (void) {
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DetectFragOffsetData *fragoff = NULL;
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fragoff = DetectFragOffsetParse("300");
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if (fragoff != NULL && fragoff->frag_off == 300) {
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DetectFragOffsetFree(fragoff);
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return 1;
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}
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return 0;
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}
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/**
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* \test DetectFragOffsetParseTest02 is a test for setting a valid fragoffset value
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* with spaces all around
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*/
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int DetectFragOffsetParseTest02 (void) {
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DetectFragOffsetData *fragoff = NULL;
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fragoff = DetectFragOffsetParse(">300");
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if (fragoff != NULL && fragoff->frag_off == 300 && fragoff->mode == FRAG_MORE) {
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DetectFragOffsetFree(fragoff);
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return 1;
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}
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return 0;
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}
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/**
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* \test DetectFragOffsetParseTest03 is a test for setting an invalid fragoffset value
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*/
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int DetectFragOffsetParseTest03 (void) {
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DetectFragOffsetData *fragoff = NULL;
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fragoff = DetectFragOffsetParse("badc");
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if (fragoff != NULL) {
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DetectFragOffsetFree(fragoff);
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return 1;
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}
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return 0;
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}
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/**
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* \test DetectFragOffsetMatchTest01 is a test for checking the working of
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* fragoffset keyword by creating 2 rules and matching a crafted packet
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* against them. Only the first one shall trigger.
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*/
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int DetectFragOffsetMatchTest01 (void) {
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int result = 0;
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Packet p;
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Signature *s = NULL;
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DecodeThreadVars dtv;
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ThreadVars th_v;
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DetectEngineThreadCtx *det_ctx = NULL;
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IPV4Hdr ip4h;
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memset(&p, 0, sizeof(Packet));
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memset(&ip4h, 0, sizeof(IPV4Hdr));
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memset(&dtv, 0, sizeof(DecodeThreadVars));
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memset(&th_v, 0, sizeof(ThreadVars));
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FlowInitConfig(FLOW_QUIET);
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p.src.family = AF_INET;
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p.dst.family = AF_INET;
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p.src.addr_data32[0] = 0x01020304;
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p.dst.addr_data32[0] = 0x04030201;
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ip4h.ip_src.s_addr = p.src.addr_data32[0];
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ip4h.ip_dst.s_addr = p.dst.addr_data32[0];
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ip4h.ip_off = 0x2222;
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p.ip4h = &ip4h;
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DetectEngineCtx *de_ctx = DetectEngineCtxInit();
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if (de_ctx == NULL) {
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goto end;
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}
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de_ctx->flags |= DE_QUIET;
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s = de_ctx->sig_list = SigInit(de_ctx, "alert ip any any -> any any (fragoffset:546; sid:1;)");
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if (s == NULL) {
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goto end;
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}
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s = s->next = SigInit(de_ctx, "alert ip any any -> any any (fragoffset:5000; sid:2;)");
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if (s == NULL) {
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goto end;
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}
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SigGroupBuild(de_ctx);
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DetectEngineThreadCtxInit(&th_v, (void *)de_ctx, (void *)&det_ctx);
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SigMatchSignatures(&th_v, de_ctx, det_ctx, &p);
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if (PacketAlertCheck(&p, 1) == 0) {
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printf("sid 1 did not alert, but should have: ");
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goto cleanup;
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} else if (PacketAlertCheck(&p, 2)) {
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printf("sid 2 alerted, but should not have: ");
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goto cleanup;
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}
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result = 1;
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cleanup:
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SigGroupCleanup(de_ctx);
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SigCleanSignatures(de_ctx);
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DetectEngineThreadCtxDeinit(&th_v, (void *)det_ctx);
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DetectEngineCtxFree(de_ctx);
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FlowShutdown();
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end:
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return result;
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}
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#endif /* UNITTESTS */
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void DetectFragOffsetRegisterTests (void) {
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#ifdef UNITTESTS
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UtRegisterTest("DetectFragOffsetParseTest01", DetectFragOffsetParseTest01, 1);
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UtRegisterTest("DetectFragOffsetParseTest02", DetectFragOffsetParseTest02, 1);
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UtRegisterTest("DetectFragOffsetParseTest03", DetectFragOffsetParseTest03, 0);
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UtRegisterTest("DetectFragOffsetMatchTest01", DetectFragOffsetMatchTest01, 1);
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#endif /* UNITTESTS */
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}
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@ -0,0 +1,21 @@
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/* Copyright (c) 2009 Open Information Security Foundation */
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/** \file
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* \author Breno Silva <breno.silva@gmail.com>
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*/
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#ifndef __DETECT_FRAGOFFSET_H__
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#define __DETECT_FRAGOFFSET_H__
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#define FRAG_LESS 1
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#define FRAG_MORE 2
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typedef struct DetectFragOffsetData_ {
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uint16_t frag_off;
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uint8_t mode;
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} DetectFragOffsetData;
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/* prototypes */
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void DetectFragOffsetRegister(void);
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#endif /* __DETECT_FRAGOFFSET__ */
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