open-dsi
/
clamav
mirror of https://github.com/Cisco-Talos/clamav
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Support wildcard alternate strings of identical length in Aho-Corasick pattern matcher.

Browse Source
0.98.2
Steven Morgan 12 years ago
parent 2680e1c3e2
commit 1c2b8bd6a4
2 changed files with 46 additions and 23 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Show Stats Download Patch File Download Diff File
  1. 65
      libclamav/matcher-ac.c
  2. 4
      libclamav/matcher-ac.h

65
libclamav/matcher-ac.c
Unescape View File

@ -1,5 +1,5 @@
/* /*
* Copyright (C) 2007-2009 Sourcefire, Inc. * Copyright (C) 2007-2013 Sourcefire, Inc.
* *
* Authors: Tomasz Kojm * Authors: Tomasz Kojm
* *
@ -166,8 +166,12 @@ int cli_ac_addpatt(struct cli_matcher *root, struct cli_ac_patt *pattern)
while(ph) { while(ph) {
if(!ph_add_after && ph->partno <= pattern->partno && (!ph->next || ph->next->partno > pattern->partno)) if(!ph_add_after && ph->partno <= pattern->partno && (!ph->next || ph->next->partno > pattern->partno))
ph_add_after = ph; ph_add_after = ph;
if((ph->length == pattern->length) && (ph->prefix_length == pattern->prefix_length) && (ph->ch[0] == pattern->ch[0]) && (ph->ch[1] == pattern->ch[1])) { if((ph->length == pattern->length) &&
if(!memcmp(ph->pattern, pattern->pattern, ph->length * sizeof(uint16_t)) && !memcmp(ph->prefix, pattern->prefix, ph->prefix_length * sizeof(uint16_t))) { (ph->prefix_length == pattern->prefix_length) &&
(ph->special_len == pattern->special_len) &&
(ph->ch[0] == pattern->ch[0]) && (ph->ch[1] == pattern->ch[1])) {
if(!memcmp(ph->pattern, pattern->pattern, ph->length * sizeof(uint16_t)) &&
!memcmp(ph->prefix, pattern->prefix, ph->prefix_length * sizeof(uint16_t))) {
if(!ph->special && !pattern->special) { if(!ph->special && !pattern->special) {
match = 1; match = 1;
} else if(ph->special == pattern->special) { } else if(ph->special == pattern->special) {
@ -806,12 +810,13 @@ int cli_ac_chklsig(const char *expr, const char *end, uint32_t *lsigcnt, unsigne
inline static int ac_findmatch(const unsigned char *buffer, uint32_t offset, uint32_t fileoffset, uint32_t length, const struct cli_ac_patt *pattern, uint32_t *end) inline static int ac_findmatch(const unsigned char *buffer, uint32_t offset, uint32_t fileoffset, uint32_t length, const struct cli_ac_patt *pattern, uint32_t *end)
{ {
uint32_t bp, match; uint32_t bp, match;
uint16_t wc, i, j, specialcnt = pattern->special_pattern; uint16_t wc, i, j, specialcnt = pattern->special_pattern;
struct cli_ac_special *special; struct cli_ac_special *special;
if((offset + pattern->length > length) || (pattern->prefix_length > offset)) if ((offset + pattern->length + pattern->special_len > length) ||
(pattern->prefix_length + pattern->special_len > offset))
return 0; return 0;
bp = offset + pattern->depth; bp = offset + pattern->depth;
@ -874,7 +879,7 @@ inline static int ac_findmatch(const unsigned char *buffer, uint32_t offset, uin
if(pattern->prefix) { if(pattern->prefix) {
specialcnt = 0; specialcnt = 0;
bp = offset - pattern->prefix_length; bp = offset - pattern->prefix_length - pattern->special_len;
match = 1; match = 1;
for(i = 0; i < pattern->prefix_length; i++) { for(i = 0; i < pattern->prefix_length; i++) {
AC_MATCH_CHAR(pattern->prefix[i],buffer[bp]); AC_MATCH_CHAR(pattern->prefix[i],buffer[bp]);
@ -885,7 +890,7 @@ inline static int ac_findmatch(const unsigned char *buffer, uint32_t offset, uin
} }
if(!(pattern->ch[0] & CLI_MATCH_IGNORE)) { if(!(pattern->ch[0] & CLI_MATCH_IGNORE)) {
bp = offset - pattern->prefix_length; bp = offset - pattern->prefix_length - pattern->special_len;
if(pattern->ch_mindist[0] + (uint32_t) 1 > bp) if(pattern->ch_mindist[0] + (uint32_t) 1 > bp)
return 0; return 0;
bp -= pattern->ch_mindist[0] + 1; bp -= pattern->ch_mindist[0] + 1;
@ -1198,12 +1203,16 @@ int cli_ac_scanbuff(const unsigned char *buffer, uint32_t length, const char **v
continue; continue;
} }
bp = i + 1 - patt->depth; bp = i + 1 - patt->depth;
if(patt->offdata[0] != CLI_OFF_VERSION && patt->offdata[0] != CLI_OFF_MACRO && !patt->next_same && (patt->offset_min != CLI_OFF_ANY) && (!patt->sigid || patt->partno == 1)) { if (patt->offdata[0] != CLI_OFF_VERSION &&
patt->offdata[0] != CLI_OFF_MACRO &&
!patt->next_same &&
(patt->offset_min != CLI_OFF_ANY) &&
(!patt->sigid || patt->partno == 1)) {
if(patt->offset_min == CLI_OFF_NONE) { if(patt->offset_min == CLI_OFF_NONE) {
patt = patt->next; patt = patt->next;
continue; continue;
} }
realoff = offset + bp - patt->prefix_length; realoff = offset + bp - patt->prefix_length - patt->special_len;
if(patt->offdata[0] == CLI_OFF_ABSOLUTE) { if(patt->offdata[0] == CLI_OFF_ABSOLUTE) {
if(patt->offset_max < realoff || patt->offset_min > realoff) { if(patt->offset_max < realoff || patt->offset_min > realoff) {
patt = patt->next; patt = patt->next;
@ -1225,7 +1234,7 @@ int cli_ac_scanbuff(const unsigned char *buffer, uint32_t length, const char **v
pt = pt->next_same; pt = pt->next_same;
continue; continue;
} }
realoff = offset + bp - pt->prefix_length; realoff = offset + bp - pt->prefix_length - patt->special_len;
if(pt->offdata[0] == CLI_OFF_VERSION) { if(pt->offdata[0] == CLI_OFF_VERSION) {
if(!cli_hashset_contains_maybe_noalloc(mdata->vinfo, realoff)) { if(!cli_hashset_contains_maybe_noalloc(mdata->vinfo, realoff)) {
pt = pt->next_same; pt = pt->next_same;
@ -1358,9 +1367,10 @@ int cli_ac_scanbuff(const unsigned char *buffer, uint32_t length, const char **v
if(res) { if(res) {
newres = (struct cli_ac_result *) malloc(sizeof(struct cli_ac_result)); newres = (struct cli_ac_result *) malloc(sizeof(struct cli_ac_result));
if(!newres) { if(!newres) {
cli_errmsg("cli_ac_scanbuff: Can't allocate memory for newres %u\n", sizeof(struct cli_ac_result)); cli_errmsg("cli_ac_scanbuff: Can't allocate memory for newres %u\n",
sizeof(struct cli_ac_result));
return CL_EMEM; return CL_EMEM;
} }
newres->virname = pt->virname; newres->virname = pt->virname;
newres->customdata = pt->customdata; newres->customdata = pt->customdata;
newres->next = *res; newres->next = *res;
@ -1391,7 +1401,8 @@ int cli_ac_scanbuff(const unsigned char *buffer, uint32_t length, const char **v
if(pt->type == CL_TYPE_IGNORED && (!pt->rtype || ftype == pt->rtype)) if(pt->type == CL_TYPE_IGNORED && (!pt->rtype || ftype == pt->rtype))
return CL_TYPE_IGNORED; return CL_TYPE_IGNORED;
if((pt->type > type || pt->type >= CL_TYPE_SFX || pt->type == CL_TYPE_MSEXE) && (!pt->rtype || ftype == pt->rtype)) { if((pt->type > type || pt->type >= CL_TYPE_SFX || pt->type == CL_TYPE_MSEXE) &&
(!pt->rtype || ftype == pt->rtype)) {
cli_dbgmsg("Matched signature for file type %s at %u\n", pt->virname, realoff); cli_dbgmsg("Matched signature for file type %s at %u\n", pt->virname, realoff);
type = pt->type; type = pt->type;
@ -1411,9 +1422,10 @@ int cli_ac_scanbuff(const unsigned char *buffer, uint32_t length, const char **v
if(res) { if(res) {
newres = (struct cli_ac_result *) malloc(sizeof(struct cli_ac_result)); newres = (struct cli_ac_result *) malloc(sizeof(struct cli_ac_result));
if(!newres) { if(!newres) {
cli_errmsg("cli_ac_scanbuff: Can't allocate memory for newres %u\n", sizeof(struct cli_ac_result)); cli_errmsg("cli_ac_scanbuff: Can't allocate memory for newres %u\n",
return CL_EMEM; sizeof(struct cli_ac_result));
} return CL_EMEM;
}
newres->virname = pt->virname; newres->virname = pt->virname;
newres->customdata = pt->customdata; newres->customdata = pt->customdata;
newres->offset = realoff; newres->offset = realoff;
@ -1675,6 +1687,10 @@ int cli_ac_addsig(struct cli_matcher *root, const char *virname, const char *hex
newspecial->type = AC_SPECIAL_WHITE; newspecial->type = AC_SPECIAL_WHITE;
*/ */
} else { } else {
/* This code block needs to be refactored to support alternate strings of varying lengths.
Only alternate strings of the same length are supported by this code block. A related
but different issue to resolve is mixing strings with individual characters
(ie, AC_SPECIAL_ALT_CHAR vs. AC_SPECIAL_ALT_STR). */
newspecial->num = 1; newspecial->num = 1;
for(i = 0; i < strlen(pt); i++) for(i = 0; i < strlen(pt); i++)
if(pt[i] == '|') if(pt[i] == '|')
@ -1689,7 +1705,7 @@ int cli_ac_addsig(struct cli_matcher *root, const char *virname, const char *hex
break; break;
} }
} else { } else {
newspecial->type = AC_SPECIAL_ALT_STR; newspecial->type = AC_SPECIAL_ALT_STR;
} }
for(i = 0; i < newspecial->num; i++) { for(i = 0; i < newspecial->num; i++) {
@ -1730,9 +1746,16 @@ int cli_ac_addsig(struct cli_matcher *root, const char *virname, const char *hex
} }
specialpt->next->str = (unsigned char *) c; specialpt->next->str = (unsigned char *) c;
specialpt->next->len = clen; specialpt->next->len = clen;
specialpt->next->negative = specialpt->negative;
specialpt->next->type = specialpt->type;
/* following two lines are temporary to revert to previous behavior for
alternate string with varying lengths, which is not supported currently. */
if (clen-1 != new->special_len)
new->special_len = 0;
} else { } else {
newspecial->str = (unsigned char *) c; newspecial->str = (unsigned char *) c;
newspecial->len = clen; newspecial->len = clen;
new->special_len = clen-1;
} }
} }
} }
@ -1839,8 +1862,8 @@ int cli_ac_addsig(struct cli_matcher *root, const char *virname, const char *hex
new->special_pattern++; new->special_pattern++;
} }
if(new->length + new->prefix_length > root->maxpatlen) if(new->length + new->prefix_length + new->special_len > root->maxpatlen)
root->maxpatlen = new->length + new->prefix_length; root->maxpatlen = new->length + new->prefix_length + new->special_len;
new->virname = cli_mpool_virname(root->mempool, virname, options & CL_DB_OFFICIAL); new->virname = cli_mpool_virname(root->mempool, virname, options & CL_DB_OFFICIAL);
if(!new->virname) { if(!new->virname) {

4
libclamav/matcher-ac.h
Unescape View File

@ -1,5 +1,5 @@
/* /*
* Copyright (C) 2007-2009 Sourcefire, Inc. * Copyright (C) 2007-2013 Sourcefire, Inc.
* *
* Authors: Tomasz Kojm * Authors: Tomasz Kojm
* *
@ -62,7 +62,7 @@ struct cli_ac_patt {
void *customdata; void *customdata;
uint16_t ch_mindist[2]; uint16_t ch_mindist[2];
uint16_t ch_maxdist[2]; uint16_t ch_maxdist[2];
uint16_t parts, partno, special, special_pattern; uint16_t parts, partno, special, special_pattern, special_len;
struct cli_ac_special **special_table; struct cli_ac_special **special_table;
struct cli_ac_patt *next, *next_same; struct cli_ac_patt *next, *next_same;
uint16_t rtype, type; uint16_t rtype, type;

Write Preview
Loading…
Cancel
Save