/*
* Byte comparison matcher support functions
*
* Copyright (C) 2018 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
* All Rights Reserved.
*
* Authors: Mickey Sola
*
* This program is free software; you can redistribute it and/or modify
* it 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
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*/
#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include "clamav.h"
#include "cltypes.h"
#include "others.h"
#include "matcher.h"
#include "matcher-ac.h"
#include "matcher-byte-comp.h"
#include "mpool.h"
#include "readdb.h"
#include "str.h"
/* DEBUGGING */
//#define MATCHER_BCOMP_DEBUG
#ifdef MATCHER_BCOMP_DEBUG
# define bcm_dbgmsg(...) cli_dbgmsg( __VA_ARGS__)
#else
# define bcm_dbgmsg(...)
#endif
#undef MATCHER_BCOMP_DEBUG
/* BCOMP MATCHER FUNCTIONS */
/**
* @brief function to add the byte compare subsig into the matcher root struct
*
* @param root the matcher root struct in question, houses all relevant lsig and subsig info
* @param virname virusname as given by the signature
* @param hexsig the raw sub signature buffer itself which we will be checking/parsing
* @param lsigid the numeric internal reference number which can be used to access this lsig in the root struct
* @param options additional options for pattern matching, stored as a bitmask
*
*/
int cli_bcomp_addpatt(struct cli_matcher *root, const char *virname, const char *hexsig, const char *offset, const uint32_t *lsigid, unsigned int options) {
if (!hexsig || !(*hexsig) || !root)
return CL_ENULLARG;
size_t len = 0;
const char *buf_start = NULL;
const char *buf_end = NULL;
char *buf = NULL;
const char *tokens[3];
size_t toks = 0;
int16_t ref_subsigid = -1;
int64_t offset_param = 0;
size_t byte_length = 0;
uint32_t comp_val = 0;
char *hexcpy = NULL;
/* we'll be using these to help the root matcher struct keep track of each loaded byte compare pattern */
struct cli_bcomp_meta **newmetatable;
uint32_t bcomp_count = 0;
/* zero out our byte compare data struct and tie it to the root struct's mempool instance */
struct cli_bcomp_meta *bcomp;
bcomp = (struct cli_bcomp_meta *) mpool_calloc(root->mempool, 1, sizeof(*bcomp));
if (!bcomp) {
cli_errmsg("cli_bcomp_addpatt: Unable to allocate memory for new byte compare meta\n");
return CL_EMEM;
}
/* allocate virname space with the root structure's mempool instance */
bcomp->virname = (char *) cli_mpool_virname(root->mempool, virname, options & CL_DB_OFFICIAL);
if(!bcomp->virname) {
cli_errmsg("cli_bcomp_addpatt: Unable to allocate memory for virname or NULL virname\n");
cli_bcomp_freemeta(root, bcomp);
return CL_EMEM;
}
/* bring along the standard lsigid vector, first param marks validity of vector, 2nd is lsigid, 3rd is subsigid */
if (lsigid) {
root->ac_lsigtable[lsigid[0]]->virname = bcomp->virname;
bcomp->lsigid[0] = 1;
bcomp->lsigid[1] = lsigid[0];
bcomp->lsigid[2] = lsigid[1];
}
else {
/* sigtool */
bcomp->lsigid[0] = 0;
}
/* first need to grab the subsig reference, we'll use this later to determine our offset */
buf_start = hexsig;
buf_end = hexsig;
ref_subsigid = strtol(buf_start, (char**) &buf_end, 10);
if (buf_end && buf_end[0] != '(') {
cli_errmsg("cli_bcomp_addpatt: while byte compare subsig parsing, reference subsig id was invalid or included non-decimal character\n");
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
bcomp->ref_subsigid = ref_subsigid;
/* use the passed hexsig buffer to find the start and ending parens and store the param length (minus starting paren) */
buf_start = buf_end;
if (buf_start[0] == '(') {
if (buf_end = strchr(buf_start, ')')) {
len = (size_t) (buf_end - ++buf_start);
}
else {
cli_errmsg("cli_bcomp_addpatt: ending paren not found\n");
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
}
else {
cli_errmsg("cli_bcomp_addpatt: opening paren not found\n");
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
/* make a working copy of the param buffer */
buf = cli_strndup(buf_start, len);
/* break up the new param buffer into its component strings and verify we have exactly 3 */
toks = cli_strtokenize(buf, '#', 3+1, tokens);
if (3 != toks) {
cli_errmsg("cli_bcomp_addpatt: %zu (or more) params provided, 3 expected\n", toks);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
/* since null termination is super guaranteed thanks to strndup and cli_strokenize, we can use strtol to grab the
* offset params. this has the added benefit of letting us parse hex values too */
buf_end = NULL;
buf_start = tokens[0];
switch (buf_start[0]) {
case '<':
if ((++buf_start)[0] == '<') {
offset_param = strtol(++buf_start, (char**) &buf_end, 0);
if (buf_end && buf_end+1 != tokens[1]) {
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), offset parameter included invalid characters\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
/* two's-complement for negative value */
offset_param = (~offset_param) + 1;
} else {
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), shift operator not valid\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
break;
case '>':
if ((++buf_start)[0] == '>') {
offset_param = strtol(buf_start, (char**) &buf_end, 0);
if (buf_end && buf_end+1 != tokens[1]) {
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), offset parameter included invalid characters\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
break;
} else {
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), shift operator and/or offset not valid\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
case '0':
case '\0':
offset_param = 0;
break;
default:
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), shift operator included invalid characters\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
bcomp->offset = offset_param;
/* the byte length indicator options are stored in a bitmask--by design each option gets its own nibble */
buf_start = tokens[1];
switch (*buf_start) {
case 'h': bcomp->options |= CLI_BCOMP_HEX; break;
case 'd': bcomp->options |= CLI_BCOMP_DEC; break;
default:
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), hex/decimal byte length indicator was found invalid\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
buf_start++;
switch (*buf_start) {
case 'l': bcomp->options |= CLI_BCOMP_LE; break;
case 'b': bcomp->options |= CLI_BCOMP_BE; break;
default:
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), little/big endian byte length indicator was invalid\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
/* parse out the byte length parameter */
buf_start++;
buf_end = NULL;
byte_length = strtol(buf_start, (char **) &buf_end, 0);
if (buf_end && buf_end+1 != tokens[2]) {
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), byte length parameter included invalid characters\n", tokens[0], tokens[1], tokens[3]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
bcomp->byte_len = byte_length;
/* currectly only >, <, and = are supported comparison symbols--this makes parsing very simple */
buf_start = tokens[2];
switch (*buf_start) {
case '<':
case '>':
case '=':
bcomp->comp_symbol = *buf_start; break;
default:
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), byte comparison symbol was invalid (>, <, = are supported operators)\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
/* no more tokens after this, so we take advantage of strtol and check if the buf_end is null terminated or not */
buf_start++;
buf_end = NULL;
comp_val = strtol(buf_start, (char **) &buf_end, 0);
if (*buf_end) {
cli_errmsg("cli_bcomp_addpatt: while parsing (%s#%s#%s), comparison value contained invalid input\n", tokens[0], tokens[1], tokens[2]);
free(buf);
cli_bcomp_freemeta(root, bcomp);
return CL_EMALFDB;
}
bcomp->comp_value = comp_val;
/* manually verify successful pattern parsing */
bcm_dbgmsg("Matcher Byte Compare: (%s%ld#%c%c%zu#%c%d)\n",
bcomp->offset == 0 ? "" :
(bcomp->offset < 0 ? "<<" : ">>"),
bcomp->offset,
bcomp->options & CLI_BCOMP_HEX ? 'h' : 'd',
bcomp->options & CLI_BCOMP_LE ? 'l' : 'b',
bcomp->byte_len,
bcomp->comp_symbol,
bcomp->comp_value);
/* add byte compare info to the root after reallocation */
bcomp_count = root->bcomp_metas+1;
/* allocate space for new meta table to store in root structure and increment number of byte compare patterns added */
newmetatable = (struct cli_bcomp_meta **) mpool_realloc(root->mempool, root->bcomp_metatable, bcomp_count * sizeof(struct cli_bcomp_meta *));
if(!newmetatable) {
cli_errmsg("cli_bcomp_addpatt: Unable to allocate memory for new bcomp meta table\n");
cli_bcomp_freemeta(root, bcomp);
return CL_EMEM;
}
newmetatable[bcomp_count-1] = bcomp;
root->bcomp_metatable = newmetatable;
root->bcomp_metas = bcomp_count;
/* if everything went well bcomp has been totally populated, which means we can cleanup and exit */
free(buf);
return CL_SUCCESS;
}
/**
* @brief function to perform all byte compare matching on the file buffer
*
* @param map the file map to perform logical byte comparison upon
* @param res the result structure, primarily used by sigtool
* @param root the root structure in which all byte compare lsig and subsig information is stored
* @param mdata the ac data struct which contains offset information from recent subsig matches
* @param ctx the clamav context struct
*
*/
int cli_bcomp_scanbuf(fmap_t *map, const char **virname, struct cli_ac_result **res, const struct cli_matcher *root, struct cli_ac_data *mdata, cli_ctx *ctx) {
int64_t i = 0, rc = 0, ret = CL_SUCCESS;
uint32_t lsigid, ref_subsigid;
uint32_t offset = 0;
uint8_t viruses_found = 0;
struct cli_bcomp_meta *bcomp = NULL;
if (!(root) || !(root->bcomp_metas) || !(root->bcomp_metatable) || !(mdata) || !(mdata->offmatrix) || !(ctx)) {
return CL_SUCCESS;
}
for(i = 0; i < root->bcomp_metas; i++) {
bcomp = root->bcomp_metatable[i];
lsigid = bcomp->lsigid[1];
ref_subsigid = bcomp->ref_subsigid;
/* ensures the referenced subsig matches as expected, and also ensures mdata has the needed offset */
if (ret = lsig_sub_matched(root, mdata, lsigid, ref_subsigid, CLI_OFF_NONE, 0)) {
continue;
}
/* grab the needed offset using from the last matched subsig offset matrix, i.e. the match performed above */
if (mdata->lsigsuboff_last[lsigid]) {
offset = mdata->lsigsuboff_last[lsigid][ref_subsigid];
} else {
ret = CL_SUCCESS;
continue;
}
/* now we have all the pieces of the puzzle, so lets do our byte compare check */
ret = cli_bcmp_compare_check(map, offset, bcomp);
/* set and append our lsig's virus name if the comparison came back positive */
if (CL_VIRUS == ret) {
viruses_found = 1;
if (virname) {
*virname = bcomp->virname;
}
/* if we aren't scanning all, let's just exit here */
if (!SCAN_ALL) {
break;
} else {
ret = cli_append_virus(ctx, (const char *)bcomp->virname);
}
}
}
if (ret == CL_SUCCESS && viruses_found) {
return CL_VIRUS;
}
return ret;
}
/**
* @brief does a numerical, logical byte comparison on a particular offset given a filemapping and the offset
*
* @param map the file buffer we'll be accessing to do our comparison check
* @param offset the offset of the referenced subsig match from the start of the file buffer
* @param bm the byte comparison meta data struct, contains all the other info needed to do the comparison
*
*/
int cli_bcmp_compare_check(fmap_t *map, int offset, struct cli_bcomp_meta *bm)
{
if (!map || !bm) {
bcm_dbgmsg("bcmp_compare_check: a param is null\n");
return CL_ENULLARG;
}
const uint32_t byte_len = bm->byte_len;
uint32_t length = map->len;
const unsigned char *buffer = NULL;
unsigned char *conversion_buf = NULL;
char opt = (char) bm->options;
uint32_t value = 0;
const unsigned char* end_buf = NULL;
/* ensure we won't run off the end of the file buffer */
if (bm->offset > 0) {
if (!((offset + bm->offset + byte_len <= length))) {
bcm_dbgmsg("bcmp_compare_check: %u bytes requested at offset %zu would go past file buffer of %u\n", byte_len, (offset + bm->offset), length);
return CL_CLEAN;
}
} else {
if (!(offset + bm->offset > 0)) {
bcm_dbgmsg("bcmp_compare_check: negative offset would underflow buffer\n");
return CL_CLEAN;
}
}
/* jump to byte compare offset, then store off specified bytes into a null terminated buffer */
offset += bm->offset;
buffer = fmap_need_off_once(map, offset, byte_len);
bcm_dbgmsg("bcmp_compare_check: literal extracted bytes before comparison (%s)\n", buffer);
/* handle byte length options to convert the string appropriately */
switch(opt) {
/*hl*/
case CLI_BCOMP_HEX | CLI_BCOMP_LE:
value = cli_strntoul(buffer, byte_len, (char**) &end_buf, 16);
if (value < 0 || NULL == end_buf || buffer+byte_len != end_buf) {
bcm_dbgmsg("bcmp_compare_check: little endian hex conversion unsuccessful\n");
return CL_CLEAN;
}
value = le32_to_host(value);
break;
/*hb*/
case CLI_BCOMP_HEX | CLI_BCOMP_BE:
value = cli_strntoul(buffer, byte_len, (char**) &end_buf, 16);
if (value < 0 || NULL == end_buf || buffer+byte_len != end_buf) {
bcm_dbgmsg("bcmp_compare_check: big endian hex conversion unsuccessful\n");
return CL_CLEAN;
}
value = be32_to_host(value);
break;
/*dl*/
case CLI_BCOMP_DEC | CLI_BCOMP_LE:
value = cli_strntoul(buffer, byte_len, (char**) &end_buf, 10);
if (value < 0 || NULL == end_buf || buffer+byte_len != end_buf) {
bcm_dbgmsg("bcmp_compare_check: little endian decimal conversion unsuccessful\n");
return CL_CLEAN;
}
value = le32_to_host(value);
break;
/*db*/
case CLI_BCOMP_DEC | CLI_BCOMP_BE:
value = cli_strntoul(buffer, byte_len, (char**) &end_buf, 10);
if (value < 0 || NULL == end_buf || buffer+byte_len != end_buf) {
bcm_dbgmsg("bcmp_compare_check: big endian decimal conversion unsuccessful\n");
return CL_CLEAN;
}
value = be32_to_host(value);
break;
default:
return CL_ENULLARG;
}
/* do the actual comparison */
switch (bm->comp_symbol) {
case '>':
if (value > bm->comp_value) {
bcm_dbgmsg("bcmp_compare_check: extracted value (%u) greater than comparison value (%u)\n", value, bm->comp_value);
return CL_VIRUS;
}
break;
case '<':
if (value < bm->comp_value) {
bcm_dbgmsg("bcmp_compare_check: extracted value (%u) less than comparison value (%u)\n", value, bm->comp_value);
return CL_VIRUS;
}
break;
case '=':
if (value == bm->comp_value) {
bcm_dbgmsg("bcmp_compare_check: extracted value (%u) equal to comparison value (%u)\n", value, bm->comp_value);
return CL_VIRUS;
}
break;
default:
bcm_dbgmsg("bcmp_compare_check: comparison symbol (%c) invalid\n", bm->comp_symbol);
return CL_ENULLARG;
}
/* comparison was not successful */
bcm_dbgmsg("bcmp_compare_check: extracted value was not %c %u\n", bm->comp_symbol, bm->comp_value);
return CL_CLEAN;
}
/**
* @brief cleans up the byte compare data struct
*
* @param root the root matcher struct whose mempool instance the bcomp struct has been allocated with
* @param bm the bcomp struct to be freed
*
*/
void cli_bcomp_freemeta(struct cli_matcher *root, struct cli_bcomp_meta *bm) {
if(!bm) {
return;
}
if (bm->virname) {
mpool_free(root->mempool, bm->virname);
bm->virname = NULL;
}
mpool_free(root->mempool, bm);
bm = NULL;
return;
}