/*
 *  Copyright (C) 2004 Tomasz Kojm <tkojm@clamav.net>
 *
 *  Implementation (header structures) based on the PE format description
 *  by B. Luevelsmeyer
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#include <time.h>

#include "cltypes.h"
#include "clamav.h"
#include "others.h"
#include "upx.h"

#define IMAGE_DOS_SIGNATURE	    0x5a4d	    /* MZ */
#define IMAGE_NT_SIGNATURE	    0x00004550
#define IMAGE_OPTIONAL_SIGNATURE    0x010b

#define UPX_NRV2B "\x11\xc9\x75\x20\x41\x01\xdb\x75\x07\x8b\x1e\x83\xee\xfc\x11\xdb\x11\xc9\x01\xdb\x73\xef\x75\x09"
#define UPX_NRV2D "\x8b\x1e\x83\xee\xfc\x11\xdb\x11\xc9\x01\xdb\x75\x07\x8b\x1e\x83\xee\xfc\x11\xdb\x11\xc9\x75\x20"
#define UPX_NRV2E "\x83\xf0\xff\x74\x75\xd1\xf8\x89\xc5\xeb\x0b\x01\xdb\x75\x07\x8b\x1e\x83\xee\xfc\x11\xdb\x72\xcc"

#if WORDS_BIGENDIAN == 0
#define EC16(v)	(v)
#define EC32(v) (v)
#else
static inline uint16_t EC16(uint16_t v)
{
    return ((v >> 8) + (v << 8));
}

static inline uint32_t EC32(uint32_t v)
{
    return ((v >> 24) | ((v & 0x00FF0000) >> 8) | ((v & 0x0000FF00) << 8) | (v << 24));
}
#endif

extern short cli_leavetemps_flag;

struct pe_image_file_hdr {
    uint32_t Magic;
    uint16_t Machine;
    uint16_t NumberOfSections;
    uint32_t TimeDateStamp;		    /* unreliable */
    uint32_t PointerToSymbolTable;	    /* debug */
    uint32_t NumberOfSymbols;		    /* debug */
    uint16_t SizeOfOptionalHeader;	    /* == 224 */
    uint16_t Characteristics;
};

struct pe_image_data_dir {
    uint32_t VirtualAddress;
    uint32_t Size;
};

struct pe_image_optional_hdr {
    uint16_t Magic;
    uint8_t  MajorLinkerVersion;		    /* unreliable */
    uint8_t  MinorLinkerVersion;		    /* unreliable */
    uint32_t SizeOfCode;			    /* unreliable */
    uint32_t SizeOfInitializedData;		    /* unreliable */
    uint32_t SizeOfUninitializedData;		    /* unreliable */
    uint32_t AddressOfEntryPoint;
    uint32_t BaseOfCode;
    uint32_t BaseOfData;
    uint32_t ImageBase;				    /* multiple of 64 KB */
    uint32_t SectionAlignment;			    /* usually 32 or 4096 */
    uint32_t FileAlignment;			    /* usually 32 or 512 */
    uint16_t MajorOperatingSystemVersion;	    /* not used */
    uint16_t MinorOperatingSystemVersion;	    /* not used */
    uint16_t MajorImageVersion;			    /* unreliable */
    uint16_t MinorImageVersion;			    /* unreliable */
    uint16_t MajorSubsystemVersion;
    uint16_t MinorSubsystemVersion;
    uint32_t Win32VersionValue;			    /* ? */
    uint32_t SizeOfImage;
    uint32_t SizeOfHeaders;
    uint32_t CheckSum;				    /* NT drivers only */
    uint16_t Subsystem;
    uint16_t DllCharacteristics;
    uint32_t SizeOfStackReserve;
    uint32_t SizeOfStackCommit;
    uint32_t SizeOfHeapReserve;
    uint32_t SizeOfHeapCommit;
    uint32_t LoaderFlags;			    /* ? */
    uint32_t NumberOfRvaAndSizes;		    /* unreliable */
    struct pe_image_data_dir DataDirectory[16];
};

struct pe_image_section_hdr {
    uint8_t Name[8];			    /* may not end with NULL */
    /*
    union {
	uint32_t PhysicalAddress;
	uint32_t VirtualSize;
    } AddrSize;
    */
    uint32_t VirtualSize;
    uint32_t VirtualAddress;
    uint32_t SizeOfRawData;		    /* multiple of FileAlignment */
    uint32_t PointerToRawData;		    /* offset to the section's data */
    uint32_t PointerToRelocations;	    /* object files only */
    uint32_t PointerToLinenumbers;	    /* object files only */
    uint16_t NumberOfRelocations;	    /* object files only */
    uint16_t NumberOfLinenumbers;	    /* object files only */
    uint32_t Characteristics;
};

static uint32_t cli_rawaddr(uint32_t rva, struct pe_image_section_hdr *shp, uint16_t nos)
{
	int i, found = 0;


    for(i = 0; i < nos; i++) {
	if(EC32(shp[i].VirtualAddress) <= rva && EC32(shp[i].VirtualAddress) + EC32(shp[i].SizeOfRawData) > rva) {
	    found = 1;
	    break;
	}
    }

    if(!found) {
	cli_dbgmsg("Can't calculate raw address from RVA 0x%x\n", rva);
	return -1;
    }

    return rva - EC32(shp[i].VirtualAddress) + EC32(shp[i].PointerToRawData);
}

static int cli_ddump(int desc, int offset, int size, const char *file)
{
	int pos, ndesc, bread, sum = 0;
	char buff[FILEBUFF];


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

    if((pos = lseek(desc, 0, SEEK_CUR)) == -1) {
	cli_dbgmsg("Invalid descriptor\n");
	return -1;
    }

    if(lseek(desc, offset, SEEK_SET) == -1) {
	cli_dbgmsg("lseek() failed\n");
	lseek(desc, pos, SEEK_SET);
	return -1;
    }

    if((ndesc = open(file, O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU)) < 0) {
	cli_dbgmsg("Can't create file %s\n", file);
	lseek(desc, pos, SEEK_SET);
	return -1;
    }

    while((bread = read(desc, buff, FILEBUFF)) > 0) {
	if(sum + bread >= size) {
	    if(write(ndesc, buff, size - sum) == -1) {
		cli_dbgmsg("Can't write to file\n");
		lseek(desc, pos, SEEK_SET);
		close(ndesc);
		unlink(file);
		return -1;
	    }
	    break;
	} else {
	    if(write(ndesc, buff, bread) == -1) {
		cli_dbgmsg("Can't write to file\n");
		lseek(desc, pos, SEEK_SET);
		close(ndesc);
		unlink(file);
		return -1;
	    }
	}
	sum += bread;
    }

    close(ndesc);
    lseek(desc, pos, SEEK_SET);
    return 0;
}

int cli_memstr(const char *haystack, int hs, const char *needle, int ns)
{
	const char *pt;
	int n;

    if(!memcmp(haystack, needle, ns))
	return 1;

    pt = haystack;
    n = hs;
    while(n && (pt = memchr(pt, needle[0], n))) {
	n--;
	if(!memcmp(pt, needle, ns))
	    return 1;
    }

    return 0;
}

int cli_scanpe(int desc, const char **virname, long int *scanned, const struct cl_node *root, const struct cl_limits *limits, int options, int *arec, int *mrec)
{
	uint16_t e_magic; /* DOS signature ("MZ") */
	uint16_t nsections;
	uint32_t e_lfanew; /* address of new exe header */
	uint32_t ep; /* entry point (raw) */
	uint32_t timestamp;
	struct pe_image_file_hdr file_hdr;
	struct pe_image_optional_hdr optional_hdr;
	struct pe_image_section_hdr *section_hdr;
	struct stat sb;
	char sname[9], buff[24], *tempfile;
	int i, found, upx_success = 0;
	int (*upxfn)(char *, int , char *, int) = NULL;


    if(read(desc, &e_magic, sizeof(e_magic)) != sizeof(e_magic)) {
	cli_dbgmsg("Can't read DOS signature\n");
	return CL_EIO;
    }

    if(EC16(e_magic) != IMAGE_DOS_SIGNATURE) {
	cli_dbgmsg("Invalid DOS signature\n");
	return CL_CLEAN;
    }

    lseek(desc, 58, SEEK_CUR); /* skip to the end of the DOS header */

    if(read(desc, &e_lfanew, sizeof(e_lfanew)) != sizeof(e_lfanew)) {
	cli_dbgmsg("Can't read new header address\n");
	return CL_EIO;
    }

    e_lfanew = EC32(e_lfanew);
    cli_dbgmsg("e_lfanew == %d\n", e_lfanew);
    if(!e_lfanew) {
	cli_dbgmsg("Not a PE file\n");
	return CL_CLEAN;
    }
    lseek(desc, e_lfanew, SEEK_SET);

    if(read(desc, &file_hdr, sizeof(struct pe_image_file_hdr)) != sizeof(struct pe_image_file_hdr)) {
	cli_dbgmsg("Can't read file header\n");
	return CL_EIO;
    }

    if(EC32(file_hdr.Magic) != IMAGE_NT_SIGNATURE) {
	cli_dbgmsg("Invalid PE signature (probably NE file)\n");
	return CL_CLEAN;
    }

    /* cli_dbgmsg("Machine type: "); */
    switch(EC16(file_hdr.Machine)) {
	case 0x14c:
	    cli_dbgmsg("Machine type: 80386\n");
	    break;
	case 0x014d:
	    cli_dbgmsg("Machine type: 80486\n");
	    break;
	case 0x014e:
	    cli_dbgmsg("Machine type: 80586\n");
	    break;
	case 0x162:
	    cli_dbgmsg("Machine type: R3000\n");
	    break;
	case 0x166:
	    cli_dbgmsg("Machine type: R4000\n");
	    break;
	case 0x168:
	    cli_dbgmsg("Machine type: R10000\n");
	    break;
	case 0x184:
	    cli_dbgmsg("Machine type: DEC Alpha AXP\n");
	    break;
	case 0x1f0:
	    cli_dbgmsg("Machine type: PowerPC\n");
	    break;
	default:
	    cli_warnmsg("Unknown machine type in PE header\n");
    }

    nsections = EC16(file_hdr.NumberOfSections);
    cli_dbgmsg("NumberOfSections: %d\n", nsections);

    timestamp = EC32(file_hdr.TimeDateStamp);
    cli_dbgmsg("TimeDateStamp: %s", ctime((time_t *) &timestamp));

    cli_dbgmsg("SizeOfOptionalHeader: %d\n", EC16(file_hdr.SizeOfOptionalHeader));

    if(EC16(file_hdr.SizeOfOptionalHeader) != sizeof(struct pe_image_optional_hdr)) {
	cli_warnmsg("Broken PE header detected.\n");
	return CL_CLEAN;
    }

    if(read(desc, &optional_hdr, sizeof(struct pe_image_optional_hdr)) != sizeof(struct pe_image_optional_hdr)) {
	cli_dbgmsg("Can't optional file header\n");
	return CL_EIO;
    }

    cli_dbgmsg("MajorLinkerVersion: %d\n", optional_hdr.MajorLinkerVersion);
    cli_dbgmsg("MinorLinkerVersion: %d\n", optional_hdr.MinorLinkerVersion);
    cli_dbgmsg("SizeOfCode: %d\n", EC32(optional_hdr.SizeOfCode));
    cli_dbgmsg("SizeOfInitializedData: %d\n", EC32(optional_hdr.SizeOfInitializedData));
    cli_dbgmsg("SizeOfUninitializedData: %d\n", EC32(optional_hdr.SizeOfUninitializedData));
    cli_dbgmsg("AddressOfEntryPoint: 0x%x\n", EC32(optional_hdr.AddressOfEntryPoint));
    cli_dbgmsg("SectionAlignment: %d\n", EC32(optional_hdr.SectionAlignment));
    cli_dbgmsg("FileAlignment: %d\n", EC32(optional_hdr.FileAlignment));
    cli_dbgmsg("MajorSubsystemVersion: %d\n", EC16(optional_hdr.MajorSubsystemVersion));
    cli_dbgmsg("MinorSubsystemVersion: %d\n", EC16(optional_hdr.MinorSubsystemVersion));
    cli_dbgmsg("SizeOfImage: %d\n", EC32(optional_hdr.SizeOfImage));
    cli_dbgmsg("SizeOfHeaders: %d\n", EC32(optional_hdr.SizeOfHeaders));

    switch(EC16(optional_hdr.Subsystem)) {
	case 1:
	    cli_dbgmsg("Subsystem: Native (a driver ?)\n");
	    break;
	case 2:
	    cli_dbgmsg("Subsystem: Win32 GUI\n");
	    break;
	case 3:
	    cli_dbgmsg("Subsystem: Win32 console\n");
	    break;
	case 5:
	    cli_dbgmsg("Subsystem: OS/2 console\n");
	    break;
	case 7:
	    cli_dbgmsg("Subsystem: POSIX console\n");
	    break;
	default:
	    cli_warnmsg("Unknown subsystem in PE header\n");
    }

    cli_dbgmsg("NumberOfRvaAndSizes: %d\n", EC32(optional_hdr.NumberOfRvaAndSizes));

    section_hdr = (struct pe_image_section_hdr *) cli_calloc(nsections, sizeof(struct pe_image_section_hdr));

    if(!section_hdr) {
	cli_dbgmsg("Can't allocate memory for section headers\n");
	return CL_EMEM;
    }

    for(i = 0; i < nsections; i++) {

	if(read(desc, &section_hdr[i], sizeof(struct pe_image_section_hdr)) != sizeof(struct pe_image_section_hdr)) {
	    cli_dbgmsg("Can't read section header\n");
	    cli_warnmsg("Possibly broken PE file\n");
	    free(section_hdr);
	    return CL_CLEAN;
	}

	strncpy(sname, section_hdr[i].Name, 8);
	sname[8] = 0;
	cli_dbgmsg("------------------------------------\n");
	cli_dbgmsg("Section name: %s\n", sname);
	cli_dbgmsg("VirtualSize: %d\n", EC32(section_hdr[i].VirtualSize));
	cli_dbgmsg("VirtualAddress: 0x%x\n", EC32(section_hdr[i].VirtualAddress));
	cli_dbgmsg("SizeOfRawData: %d\n", EC32(section_hdr[i].SizeOfRawData));
	cli_dbgmsg("PointerToRawData: 0x%x (%d)\n", EC32(section_hdr[i].PointerToRawData), EC32(section_hdr[i].PointerToRawData));

	if(EC32(section_hdr[i].Characteristics) & 0x20) {
	    cli_dbgmsg("Section contains executable code\n");

	    if(EC32(section_hdr[i].VirtualSize) < EC32(section_hdr[i].SizeOfRawData)) {
		cli_dbgmsg("Section contains free space\n");
		/*
		cli_dbgmsg("Dumping %d bytes\n", section_hdr.SizeOfRawData - section_hdr.VirtualSize);
		ddump(desc, section_hdr.PointerToRawData + section_hdr.VirtualSize, section_hdr.SizeOfRawData - section_hdr.VirtualSize, cl_gentemp(NULL));
		*/

	    }
	}

	if(EC32(section_hdr[i].Characteristics) & 0x20000000)
	    cli_dbgmsg("Section's memory is executable\n");

/*
	if(!strcmp(sname, "_winzip_")) {
	    int ptrd = section_hdr.PointerToRawData & ~(optional_hdr.FileAlignment - 1);

	    cli_dbgmsg("WinZip section\n");
	    ddump(desc, ptrd, section_hdr.SizeOfRawData, cl_gentemp(NULL));
	}
*/

    }

    if(fstat(desc, &sb) == -1) {
	cli_dbgmsg("fstat failed\n");
	free(section_hdr);
	return CL_EIO;
    }

    ep = cli_rawaddr(EC32(optional_hdr.AddressOfEntryPoint), section_hdr, nsections);

    if(EC32(section_hdr[i].PointerToRawData) + EC32(section_hdr[i].SizeOfRawData) > sb.st_size || ep == -1) {
	cli_dbgmsg("Possibly broken PE file\n");
	free(section_hdr);
	return CL_CLEAN;
    }

    cli_dbgmsg("EntryPoint offset: 0x%x (%d)\n", ep, ep);


    /* UPX support */

    /* try to detect UPX code */

    if(lseek(desc, ep + 0x78, SEEK_SET) == -1) {
	cli_dbgmsg("lseek() failed\n");
	free(section_hdr);
	return CL_EIO;
    }

    if(read(desc, buff, 13) != 13) {
	cli_dbgmsg("UPX: Can't read 13 bytes at 0x%x (%d)\n", ep + 0x78, ep + 0x78);
    } else {
	if(cli_memstr(UPX_NRV2B, 24, buff, 13)) {
	    cli_dbgmsg("UPX: Looks like a NRV2B decompressor\n");
	    upxfn = upx_inflate2b;
	} else if(cli_memstr(UPX_NRV2D, 24, buff, 13)) {
	    cli_dbgmsg("UPX: Looks like a NRV2D decompressor\n");
	    upxfn = upx_inflate2d;
	} else if(cli_memstr(UPX_NRV2E, 24, buff, 13)) {
            cli_dbgmsg("UPX: Looks like a NRV2E decompressor\n");
	    upxfn = upx_inflate2e;
	}
    }

    /* try to find the first section with physical size == 0 */
    found = 0;
    for(i = 0; i < nsections - 1; i++) {
	if(!section_hdr[i].SizeOfRawData) {
	    found = 1;
	    cli_dbgmsg("UPX: empty section found - assuming UPX compression\n");
	    break;
	}
    }

    if(found) {
	    int ssize, dsize;
	    char *src, *dest;

	strncpy(sname, section_hdr[i].Name, 8);
	sname[8] = 0;
	cli_dbgmsg("UPX: Section %d name: %s\n", i, sname);
	strncpy(sname, section_hdr[i + 1].Name, 8);
	sname[8] = 0;
	cli_dbgmsg("UPX: Section %d name: %s\n", i + 1, sname);

	if(strncmp(section_hdr[i].Name, "UPX0", 4) || strncmp(section_hdr[i + 1].Name, "UPX1", 4))
	    cli_dbgmsg("UPX: Possibly hacked UPX section headers\n");

	/* we assume (i + 1) is UPX1 */
	ssize = EC32(section_hdr[i + 1].SizeOfRawData);
	dsize = EC32(section_hdr[i].VirtualSize) + EC32(section_hdr[i + 1].VirtualSize);

	/* FIXME: use file operations in case of big files */
	if((src = (char *) cli_malloc(ssize)) == NULL) {
	    free(section_hdr);
	    return CL_EMEM;
	}

	if((dest = (char *) cli_calloc(dsize, sizeof(char))) == NULL) {
	    free(section_hdr);
	    free(src);
	    return CL_EMEM;
	}

	lseek(desc, EC32(section_hdr[i + 1].PointerToRawData), SEEK_SET);
	if(read(desc, src, ssize) != ssize) {
	    cli_dbgmsg("Can't read raw data of section %d\n", i + 1);
	    free(section_hdr);
	    free(src);
	    free(dest);
	    return CL_EIO;
	}

	if(upxfn) {
	    if(upxfn(src, ssize, dest, dsize)) {
		cli_dbgmsg("UPX: Prefered decompressor failed\n");
	    } else {
		upx_success = 1;
		cli_dbgmsg("UPX: Successfuly decompressed\n");
	    }
	}

	if(!upx_success && upxfn != upx_inflate2b) {
	    if(upx_inflate2b(src, ssize, dest, dsize)) {
		cli_dbgmsg("UPX: NRV2B decompressor failed\n");
	    } else {
		upx_success = 1;
		cli_dbgmsg("UPX: Successfuly decompressed with NRV2B\n");
	    }
	}

	if(!upx_success && upxfn != upx_inflate2d) {
	    if(upx_inflate2d(src, ssize, dest, dsize)) {
		cli_dbgmsg("UPX: NRV2D decompressor failed\n");
	    } else {
		upx_success = 1;
		cli_dbgmsg("UPX: Successfuly decompressed with NRV2D\n");
	    }
	}

	if(!upx_success && upxfn != upx_inflate2e) {
	    if(upx_inflate2e(src, ssize, dest, dsize)) {
		cli_dbgmsg("UPX: NRV2E decompressor failed\n");
	    } else {
		upx_success = 1;
		cli_dbgmsg("UPX: Successfuly decompressed with NRV2E\n");
	    }
	}

	if(!upx_success) {
	    cli_dbgmsg("UPX: All decompressors failed\n");
	} else {
	    int ndesc;

	    if(cli_leavetemps_flag) {
		tempfile = cl_gentemp(NULL);
		if((ndesc = open(tempfile, O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU)) < 0) {
		    cli_dbgmsg("UPX: Can't create file %s\n", tempfile);
		    free(section_hdr);
		    free(src);
		    free(dest);
		    return CL_EIO;
		}

		if(write(ndesc, dest, dsize) != dsize) {
		    cli_dbgmsg("Can't write %d bytes\n", dsize);
		    free(section_hdr);
		    free(src);
		    free(dest);
		    return CL_EIO;
		}

		close(ndesc);
		cli_dbgmsg("UPX: Decompressed data saved in %s\n", tempfile);
		free(tempfile);
	    }

	    if(cl_scanbuff(dest, dsize, virname, root) == CL_VIRUS) {
		free(section_hdr);
		free(src);
		free(dest);
		return CL_VIRUS;
	    }
	}

	free(src);
	free(dest);
    }

    /* to be continued ... */

    free(section_hdr);
    return CL_CLEAN;
}