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/* |
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* Copyright (C) 2007-2008 Sourcefire, Inc.
*
* Authors: Tomasz Kojm |
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*
* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation. |
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*
* 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
* along with this program; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA. |
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*/
|
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#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <stdio.h>
|
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#include "clamav.h"
#include "memory.h"
#include "others.h"
#include "cltypes.h" |
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#include "matcher.h" |
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#include "matcher-bm.h" |
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#include "filetypes.h" |
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|
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#define BM_MIN_LENGTH 3 |
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#define BM_BLOCK_SIZE 3 |
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#define HASH(a,b,c) (211 * a + 37 * b + c) |
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|
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int cli_bm_addpatt(struct cli_matcher *root, struct cli_bm_patt *pattern) |
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{ |
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uint16_t idx, i; |
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const unsigned char *pt = pattern->pattern; |
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struct cli_bm_patt *prev, *next = NULL;
if(pattern->length < BM_MIN_LENGTH) { |
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cli_errmsg("Signature for %s is too short\n", pattern->virname);
return CL_EPATSHORT; |
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}
|
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#if BM_MIN_LENGTH == BM_BLOCK_SIZE
/* try to load balance bm_suffix (at the cost of bm_shift) */
for(i = 0; i < pattern->length - BM_BLOCK_SIZE + 1; i++) { |
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idx = HASH(pt[i], pt[i + 1], pt[i + 2]); |
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if(!root->bm_suffix[idx]) {
if(i) {
pattern->prefix = pattern->pattern;
pattern->prefix_length = i;
pattern->pattern = &pattern->pattern[i];
pattern->length -= i;
pt = pattern->pattern;
}
break;
} |
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} |
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#endif |
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|
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for(i = 0; i <= BM_MIN_LENGTH - BM_BLOCK_SIZE; i++) {
idx = HASH(pt[i], pt[i + 1], pt[i + 2]);
root->bm_shift[idx] = MIN(root->bm_shift[idx], BM_MIN_LENGTH - BM_BLOCK_SIZE - i);
} |
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prev = next = root->bm_suffix[idx];
while(next) { |
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if(pt[0] >= next->pattern[0]) |
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break;
prev = next;
next = next->next;
}
|
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if(next == root->bm_suffix[idx]) { |
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pattern->next = root->bm_suffix[idx]; |
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if(root->bm_suffix[idx])
pattern->cnt = root->bm_suffix[idx]->cnt; |
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root->bm_suffix[idx] = pattern;
} else {
pattern->next = prev->next;
prev->next = pattern;
} |
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root->bm_suffix[idx]->cnt++; |
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|
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root->bm_patterns++; |
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return CL_SUCCESS; |
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}
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int cli_bm_init(struct cli_matcher *root) |
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{ |
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uint16_t i, size = HASH(255, 255, 255) + 1; |
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|
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if(!(root->bm_shift = (uint8_t *) cli_calloc(size, sizeof(uint8_t)))) |
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return CL_EMEM;
|
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if(!(root->bm_suffix = (struct cli_bm_patt **) cli_calloc(size, sizeof(struct cli_bm_patt *)))) { |
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free(root->bm_shift);
return CL_EMEM;
}
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for(i = 0; i < size; i++) |
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root->bm_shift[i] = BM_MIN_LENGTH - BM_BLOCK_SIZE + 1;
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return CL_SUCCESS; |
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}
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void cli_bm_free(struct cli_matcher *root) |
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{ |
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struct cli_bm_patt *patt, *prev;
uint16_t i, size = HASH(255, 255, 255) + 1; |
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|
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if(root->bm_shift)
free(root->bm_shift);
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if(root->bm_suffix) { |
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for(i = 0; i < size; i++) { |
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patt = root->bm_suffix[i];
while(patt) {
prev = patt;
patt = patt->next;
if(prev->prefix)
free(prev->prefix);
else
free(prev->pattern);
if(prev->virname)
free(prev->virname);
if(prev->offset)
free(prev->offset);
free(prev); |
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}
} |
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free(root->bm_suffix); |
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} |
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}
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int cli_bm_scanbuff(const unsigned char *buffer, uint32_t length, const char **virname, const struct cli_matcher *root, uint32_t offset, cli_file_t ftype, int fd) |
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{ |
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uint32_t i, j, off;
uint8_t found, pchain, shift;
uint16_t idx, idxchk; |
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struct cli_bm_patt *p; |
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const unsigned char *bp, *pt; |
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unsigned char prefix; |
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struct cli_target_info info; |
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|
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if(!root || !root->bm_shift) |
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return CL_CLEAN;
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if(length < BM_MIN_LENGTH)
return CL_CLEAN;
|
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memset(&info, 0, sizeof(info));
|
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for(i = BM_MIN_LENGTH - BM_BLOCK_SIZE; i < length - BM_BLOCK_SIZE + 1; ) { |
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idx = HASH(buffer[i], buffer[i + 1], buffer[i + 2]); |
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shift = root->bm_shift[idx];
if(shift == 0) {
prefix = buffer[i - BM_MIN_LENGTH + BM_BLOCK_SIZE];
p = root->bm_suffix[idx]; |
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pchain = 0;
while(p) {
if(p->pattern[0] != prefix) {
if(pchain)
break;
p = p->next;
continue;
} else pchain = 1; |
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off = i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
bp = buffer + off; |
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|
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if((off + p->length > length) || (p->prefix_length > off)) { |
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p = p->next;
continue;
}
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idxchk = MIN(p->length, length - off) - 1;
if(idxchk) {
if((bp[idxchk] != p->pattern[idxchk]) || (bp[idxchk / 2] != p->pattern[idxchk / 2])) { |
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p = p->next;
continue;
}
}
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if(p->prefix_length) {
off -= p->prefix_length;
bp -= p->prefix_length;
pt = p->prefix;
} else {
pt = p->pattern;
}
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found = 1; |
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for(j = 0; j < p->length + p->prefix_length && off < length; j++, off++) {
if(bp[j] != pt[j]) { |
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found = 0;
break;
}
} |
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|
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if(found && p->length + p->prefix_length == j) { |
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if(p->target || p->offset) { |
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off = offset + i - p->prefix_length - BM_MIN_LENGTH + BM_BLOCK_SIZE; |
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if((fd == -1 && !ftype) || !cli_validatesig(ftype, p->offset, off, &info, fd, p->virname)) { |
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p = p->next;
continue;
} |
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}
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if(virname)
*virname = p->virname;
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if(info.exeinfo.section)
free(info.exeinfo.section);
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return CL_VIRUS;
} |
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|
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p = p->next;
}
shift = 1;
}
i += shift;
}
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if(info.exeinfo.section)
free(info.exeinfo.section);
return CL_CLEAN; |
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} |