/*
  *  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;

 }