/*

  *  Copyright (C) 2007-2008 Sourcefire, Inc.
  *

  *  Authors: Trog, Török Edvin

  *
  *  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.

  */
 

 #ifdef	_MSC_VER
 #include <windows.h>
 #endif
 

 #include "clamav-config.h"
 

 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>

 #ifdef	HAVE_UNISTD_H

 #include <unistd.h>

 #endif
 #ifndef	C_WINDOWS

 #include <netinet/in.h>

 #endif

 #include <string.h>

 #include <ctype.h>

 #include "clamav.h"
 #include "others.h"

 #include "cltypes.h"

 #include "special.h"

 #include "matcher.h"

 /* NOTE: Photoshop stores data in BIG ENDIAN format, this is the opposite
 	to virtually everything else */
 

 #define special_endian_convert_16(v) be16_to_host(v)
 #define special_endian_convert_32(v) be32_to_host(v)

 int cli_check_mydoom_log(int desc, cli_ctx *ctx)

 {
 	int32_t record[8], check;
 	int i, retval=CL_VIRUS, j;
 
     cli_dbgmsg("in cli_check_mydoom_log()\n");
 
     /* Check upto the first five records in the file */
     for (j=0 ; j<5 ; j++) {
 	if (cli_readn(desc, &record, 32) != 32) {
 	    break;
 	}

 	if(!j && record[0] == 0xffffffff) /* bb#1241 */
 	    return CL_CLEAN;

 
 	/* Decode the key */
 	record[0] = ~ntohl(record[0]);

 	cli_dbgmsg("Mydoom: key: %d\n", record[0]);

 	check = 0;
 	for (i=1 ; i<8; i++) {
 	    record[i] = ntohl(record[i]) ^ record[0];
 	    check += record[i];
 	}

 	cli_dbgmsg("Mydoom: check: %d\n", ~check);

 	if ((~check) != record[0]) {
 	    return CL_CLEAN;
 	}
     }
 
     if (j < 2) {
 	retval = CL_CLEAN;
     } else if (retval==CL_VIRUS) {

 	if(cli_checkfp(desc, ctx))
 	    return CL_CLEAN;
 	*ctx->virname = "Worm.Mydoom.M.log";

     }
 
     return retval;
 }
 

 static int jpeg_check_photoshop_8bim(int fd, cli_ctx *ctx)

 {
 	unsigned char bim[5];

 	uint16_t id, ntmp;
 	uint8_t nlength;

 	uint32_t size;
 	off_t offset;
 	int retval;
 
 	if (cli_readn(fd, bim, 4) != 4) {
 		cli_dbgmsg("read bim failed\n");
 		return -1;
 	}
 
 	if (memcmp(bim, "8BIM", 4) != 0) {
 		bim[4] = '\0';
 		cli_dbgmsg("missed 8bim: %s\n", bim);
 		return -1;
 	}
 
 	if (cli_readn(fd, &id, 2) != 2) {
 		return -1;
 	}
 	id = special_endian_convert_16(id);
 	cli_dbgmsg("ID: 0x%.4x\n", id);

 	if (cli_readn(fd, &nlength, 1) != 1) {

 		return -1;
 	}

 	ntmp = nlength + ((((uint16_t)nlength)+1) & 0x01);
 	lseek(fd, ntmp, SEEK_CUR);
 	

 	if (cli_readn(fd, &size, 4) != 4) {
 		return -1;
 	}
 	size = special_endian_convert_32(size);
 	if (size == 0) {
 		return -1;
 	}
 	if ((size & 0x01) == 1) {
 		size++;
 	}
 	/* Is it a thumbnail image */
 	if ((id != 0x0409) && (id != 0x040c)) {
 		/* No - Seek past record */
 		lseek(fd, size, SEEK_CUR);
 		return 0;
 	}
 
 	cli_dbgmsg("found thumbnail\n");
 	/* Check for thumbmail image */
 	offset = lseek(fd, 0, SEEK_CUR);
 
 	/* Jump past header */
 	lseek(fd, 28, SEEK_CUR);
 

 	retval = cli_check_jpeg_exploit(fd, ctx);

 	if (retval == 1) {

 		cli_dbgmsg("Exploit found in thumbnail\n");

 	}
 	lseek(fd, offset+size, SEEK_SET);
 
 	return retval;
 }
 

 static int jpeg_check_photoshop(int fd, cli_ctx *ctx)

 {
 	int retval;
 	unsigned char buffer[14];

 	off_t old, new;

 
 	if (cli_readn(fd, buffer, 14) != 14) {
 		return 0;
 	}
 
 	if (memcmp(buffer, "Photoshop 3.0", 14) != 0) {
 		return 0;
 	}
 
 	cli_dbgmsg("Found Photoshop segment\n");
 	do {

 		old = lseek(fd, 0, SEEK_CUR);

 		retval = jpeg_check_photoshop_8bim(fd, ctx);

 		new = lseek(fd, 0, SEEK_CUR);
 		if(new <= old)
 			break;

 	} while (retval == 0);
 
 	if (retval == -1) {
 		retval = 0;
 	}
 	return retval;
 }
 

 int cli_check_jpeg_exploit(int fd, cli_ctx *ctx)

 {
 	unsigned char buffer[4];
 	off_t offset;
 	int retval;

 
 	cli_dbgmsg("in cli_check_jpeg_exploit()\n");

 	if(ctx->recursion > ctx->engine->maxreclevel)
 	    return CL_EMAXREC;

 
 	if (cli_readn(fd, buffer, 2) != 2) {
 		return 0;
 	}

 	if ((buffer[0] != 0xff) || (buffer[1] != 0xd8)) {

 		return 0;
 	}

 	for (;;) {
 		if ((retval=cli_readn(fd, buffer, 4)) != 4) {
 			return 0;
 		}

 		/* Check for multiple 0xFF values, we need to skip them */
 		if ((buffer[0] == 0xff) && (buffer[1] == 0xff)) {
 			lseek(fd, -3, SEEK_CUR);
 			continue;
 		}

 		if ((buffer[0] == 0xff) && (buffer[1] == 0xfe)) {
 			if (buffer[2] == 0x00) {
 				if ((buffer[3] == 0x00) || (buffer[3] == 0x01)) {
 					return 1;
 				}
 			}
 		}
 		if (buffer[0] != 0xff) {
 			return -1;
 		}
 		if (buffer[1] == 0xda) {
 			/* End of Image marker */
 			return 0;
 		}

 		offset = ((unsigned int) buffer[2] << 8) + buffer[3];
 		if (offset < 2) {

 			return -1;

 		}
 		offset -= 2;
 		offset += lseek(fd, 0, SEEK_CUR);

 
 		if (buffer[1] == 0xed) {
 			/* Possible Photoshop file */

 			ctx->recursion++;
 			retval=jpeg_check_photoshop(fd, ctx);
 			ctx->recursion--;
 			if (retval != 0)

 				return retval;
 		}
 

 		if (lseek(fd, offset, SEEK_SET) != offset) {
 			return -1;
 		}
 	}
 }

 static uint32_t riff_endian_convert_32(uint32_t value, int big_endian)
 {

 	if (big_endian)
 		return be32_to_host(value);
 	else
 		return le32_to_host(value);

 }

 
 static int riff_read_chunk(int fd, int big_endian, int rec_level)
 {
 	uint32_t chunk_id;
 	uint32_t chunk_size;
 	int length;
 	uint32_t list_type;
 	off_t offset, cur_offset;
 
 	if (rec_level > 1000) {
 		cli_dbgmsg("riff_read_chunk: recursion level exceeded\n");
 		return 0;
 	}
 	
 	length = sizeof(uint32_t);
 	if (cli_readn(fd, &chunk_id, length) != length) {
 		return 0;
 	}
 	if (cli_readn(fd, &chunk_size, length) != length) {
 		return 0;
 	}

 	chunk_size = riff_endian_convert_32(chunk_size, big_endian);

 
 	if (memcmp(&chunk_id, "RIFF", 4) == 0) {
 		return 0;
 	} else if (memcmp(&chunk_id, "RIFX", 4) == 0) {
 		return 0;
 	}
 	
 	if ((memcmp(&chunk_id, "LIST", 4) == 0) ||
 		 (memcmp(&chunk_id, "PROP", 4) == 0) ||
 		 (memcmp(&chunk_id, "FORM", 4) == 0) ||
 		 (memcmp(&chunk_id, "CAT ", 4) == 0)) {
 		if (cli_readn(fd, &list_type, sizeof(list_type)) != sizeof(list_type)) {
 			cli_dbgmsg("riff_read_chunk: read list type failed\n");
 			return 0;
 		}
 		return riff_read_chunk(fd, big_endian, ++rec_level);	
 	}
 	
 	cur_offset = lseek(fd, 0, SEEK_CUR);
 	offset = cur_offset + chunk_size;
 	/* Check for odd alignment */
 	if ((offset & 0x01) == 1) {
 		offset++;
 	}
 	if (offset < cur_offset) {
 		return 0;
 	}
 	if (lseek(fd, offset, SEEK_SET) != offset) {
 		return 2;
 	}
 	return 1;
 }
 
 int cli_check_riff_exploit(int fd)
 {
 	uint32_t chunk_id;
 	uint32_t chunk_size;
 	uint32_t form_type;
 	int length, big_endian, retval;
 	off_t offset;
 	
 	cli_dbgmsg("in cli_check_riff_exploit()\n");
 
 	length = sizeof(uint32_t);
 	if (cli_readn(fd, &chunk_id, length) != length) {
 		return 0;
 	}
 	if (cli_readn(fd, &chunk_size, length) != length) {
 		return 0;
 	}
 	if (cli_readn(fd, &form_type, length) != length) {
 		return 0;
 	}
 	
 	if (memcmp(&chunk_id, "RIFF", 4) == 0) {
 		big_endian = FALSE;
 	} else if (memcmp(&chunk_id, "RIFX", 4) == 0) {
 		big_endian = TRUE;
 	} else {
 		/* Not a RIFF file */
 		return 0;
 	}
 

 	if (memcmp(&form_type, "ACON", 4) != 0) {
 		/* Only scan MS animated icon files */
 		/* There is a *lot* of broken software out there that produces bad RIFF files */
 		return 0;
 	}
 

 	chunk_size = riff_endian_convert_32(chunk_size, big_endian);

 
 	do {
 		retval = riff_read_chunk(fd, big_endian, 1);
 	} while (retval == 1);
 		
 	offset = lseek(fd, 0, SEEK_CUR);
 

 	if (offset < (int64_t)chunk_size) {

 		retval = 2;

 	}

 	return retval;
 }

 
 static inline int swizz_j48(const uint16_t n[])
 {
 	cli_dbgmsg("swizz_j48: %u, %u, %u\n",n[0],n[1],n[2]);
 	/* rules based on J48 tree */

 	if (n[0] <= 945 || !n[1])
 		return 0;
 	if (n[0] <= 1006)
 		return (n[2] > 0 && n[2] <= 6);
 	else
 		return n[1] <= 10;

 }
 
 void cli_detect_swizz_str(const unsigned char *str, uint32_t len, struct swizz_stats *stats, int blob)
 {
 	unsigned char stri[4096];
         uint32_t i, j = 0;
 	int bad = 0;
 	int lastalnum = 0;
 	uint8_t ngrams[17576];
 	uint16_t all=0;
 	uint16_t ngram_cnts[3];
 	uint16_t words = 0;
 	int ret;
 

 	stats->entries++;

 	for(i=0;i<len-1 && j < sizeof(stri)-2;i += 2) {
 		unsigned char c = str[i];
 		if (str[i+1] || !c) {
 			bad++;
 			continue;
 		}
 		if (!isalnum(c)) {
 			if (!lastalnum)
 				continue;
 			lastalnum = 0;
 			c = ' ';
 		} else {
 			lastalnum = 1;
 			if (isdigit(c))
 				continue;
 		}
 		stri[j++] = tolower(c);
 	}
 	stri[j++] = '\0';
 	if ((!blob && (bad >= 8)) || j < 4)
 		return;
 	memset(ngrams, 0, sizeof(ngrams));
 	memset(ngram_cnts, 0, sizeof(ngram_cnts));
 	for(i=0;i<j-2;i++) {
 		if (stri[i] != ' ' && stri[i+1] != ' ' && stri[i+2] != ' ') {
 			uint16_t idx = (stri[i] - 'a')*676 + (stri[i+1] - 'a')*26 + (stri[i+2] - 'a');

 			if (idx < sizeof(ngrams)) {

 				ngrams[idx]++;

 				stats->gngrams[idx]++;
 			}

 		} else if (stri[i] == ' ')
 			words++;
 	}
 	for(i=0;i<sizeof(ngrams);i++) {
 		uint8_t v = ngrams[i];
 		if (v > 3) v = 3;
 		if (v) {
 			ngram_cnts[v-1]++;
 			all++;
 		}
 	}
 	if (!all)
 		return;
 	cli_dbgmsg("cli_detect_swizz_str: %u, %u, %u\n",ngram_cnts[0],ngram_cnts[1],ngram_cnts[2]);
 	/* normalize */
 	for(i=0;i<sizeof(ngram_cnts)/sizeof(ngram_cnts[0]);i++) {
 		uint32_t v = ngram_cnts[i];
 		ngram_cnts[i] = (v<<10)/all;
 	}

 	ret = swizz_j48(ngram_cnts) ? CL_VIRUS : CL_CLEAN;

 	if (!words) ret = CL_CLEAN;

 	cli_dbgmsg("cli_detect_swizz_str: %s, %u words\n", ret == CL_VIRUS ? "suspicious" : "ok", words);

 	if (ret == CL_VIRUS) {

 		stats->suspicious += j;

 		cli_dbgmsg("cli_detect_swizz_str: %s\n", stri);
 	}

 	stats->total += j;
 }
 

 static inline int swizz_j48_global(const uint32_t gn[])

 {
 	if (gn[0] <= 24185) {
 		return gn[0] > 22980 && gn[8] > 0 && gn[8] <= 97;
 	}
 	if (!gn[8]) {
 		if (gn[4] <= 311) {
 			if (!gn[4]) {
 				return gn[1] > 0 &&
 					((gn[0] <= 26579 && gn[3] > 0) ||
 					 (gn[0] > 28672 && gn[0] <= 30506));
 			}
 			if (gn[5] <= 616) {
 				if (gn[6] <= 104) {
 					return gn[9] <= 167;
 				}
 				return gn[6] <= 286;
 			}
 		}
 		return 0;
 	}
 	return 1;
 }
 

 int cli_detect_swizz(struct swizz_stats *stats)
 {

 	uint32_t gn[10];
 	uint32_t all = 0;
 	unsigned i;
 	int global_swizz = CL_CLEAN;
 

 	cli_dbgmsg("cli_detect_swizz: %lu/%lu, version:%d, manifest: %d \n",
 			(unsigned long)stats->suspicious, (unsigned long)stats->total,
 			stats->has_version, stats->has_manifest);

 	memset(gn, 0, sizeof(gn));
 	for(i=0;i<17576;i++) {
 		uint8_t v = stats->gngrams[i];
 		if (v > 10) v = 10;
 		if (v) {
 			gn[v-1]++;
 			all++;
 		}
 	}
 	if (all) {
 		/* normalize */
 		cli_dbgmsg("cli_detect_swizz: gn: ");
 		for(i=0;i<sizeof(gn)/sizeof(gn[0]);i++) {
 			uint32_t v = gn[i];
 			gn[i] = (v<<15)/all;
 			if (cli_debug_flag)
 			cli_dbgmsg("%lu, ", (unsigned long)gn[i]);
 		}
 		global_swizz = swizz_j48_global(gn) ? CL_VIRUS : CL_CLEAN;
 		cli_dbgmsg("\ncli_detect_swizz: global: %s\n", global_swizz ? "suspicious" : "clean");

 	}

 	if (stats->errors > stats->entries || stats->errors >= SWIZZ_MAXERRORS) {
 	    cli_dbgmsg("cli_detect_swizz: resources broken, ignoring\n");
 	    return CL_CLEAN;
 	}

 	if (stats->total <= 337)

 	    return CL_CLEAN;

 	if (stats->suspicious<<10 > 40*stats->total)

 	    return CL_VIRUS;
 	if (!stats->suspicious)
 	    return CL_CLEAN;

 	return global_swizz;

 }