clamav/clamav-devel/libclamav/pe.c

/*
 *  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"

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(shp[i].VirtualAddress <= rva && shp[i].VirtualAddress + 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 - shp[i].VirtualAddress + 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 CL_EIO;
    }

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

    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 CL_EIO;
    }

    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 CL_EIO;
	    }
	    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 CL_EIO;
	    }
	}
	sum += bread;
    }

    close(ndesc);
    lseek(desc, pos, SEEK_SET);
    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 *reclev)
{
	uint16_t e_magic; /* DOS signature ("MZ") */
	uint32_t e_lfanew; /* address of new exe header */
	uint32_t ep; /* entry point (raw) */
	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;
	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(e_magic != IMAGE_DOS_SIGNATURE) {
	cli_dbgmsg("Invalid DOS signature\n");
	return -1;
    }

    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 -1;
    }

    cli_dbgmsg("e_lfanew == %d\n", e_lfanew);
    if(!e_lfanew) {
	cli_dbgmsg("Not a PE file\n");
	return -2;
    }

    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 -1;
    }

    if(file_hdr.Magic != IMAGE_NT_SIGNATURE) {
	cli_dbgmsg("Invalid PE signature (probably NE file)\n");
	return -2;
    }

    /* cli_dbgmsg("Machine type: "); */
    switch(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");
    }

    cli_dbgmsg("NumberOfSections: %d\n", file_hdr.NumberOfSections);
    cli_dbgmsg("TimeDateStamp: %s", ctime((time_t *) &file_hdr.TimeDateStamp));

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

    if(file_hdr.SizeOfOptionalHeader != sizeof(struct pe_image_optional_hdr)) {
	cli_warnmsg("Broken PE header detected.\n");
	return -1;
    }

    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 -1;
    }

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

    switch(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", optional_hdr.NumberOfRvaAndSizes);

    section_hdr = (struct pe_image_section_hdr *) cli_calloc(file_hdr.NumberOfSections, 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 < file_hdr.NumberOfSections; 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", section_hdr[i].VirtualSize);
	cli_dbgmsg("VirtualAddress: 0x%x\n", section_hdr[i].VirtualAddress);
	cli_dbgmsg("Section size: %d\n", section_hdr[i].SizeOfRawData);
	cli_dbgmsg("PointerToRawData: 0x%x (%d)\n", section_hdr[i].PointerToRawData, section_hdr[i].PointerToRawData);

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

	    if(section_hdr[i].VirtualSize < 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(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(optional_hdr.AddressOfEntryPoint, section_hdr, file_hdr.NumberOfSections);

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

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

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

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

    if(upxfn) {
	/* try to find the first section with physical size == 0 */
	found = 0;
	for(i = 0; i < file_hdr.NumberOfSections; i++) {
	    if(!section_hdr[i].SizeOfRawData) {
		found = 1;
		break;
	    }
	}

	if(found) {
		uint32_t ssize, dsize;
		char *src, *dest;

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

	    /* FIXME: use file operations in case of big files */
	    ssize = section_hdr[i + 1].SizeOfRawData;
	    dsize = section_hdr[i].VirtualSize + section_hdr[i + 1].VirtualSize;
	    if((src = (char *) malloc(ssize)) == NULL) {
		free(section_hdr);
		return CL_EMEM;
	    }

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

	    lseek(desc, 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_EMEM;
	    }

	    if(upxfn(src, ssize, dest, dsize)) {
		cli_dbgmsg("UPX decompression failed\n");
	    } else {
		    int ndesc;

		tempfile = cl_gentemp(NULL);

		if((ndesc = open(tempfile, O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU)) < 0) {
		    cli_dbgmsg("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);

		/* TODO: scan and unlink file */

		/* unlink(tempfile); */
		free(tempfile);
	    }

	    free(src);
	    free(dest);

	} else {
	    cli_dbgmsg("UPX sections not found\n");
	}
    }

    /* to be continued ... */

    free(section_hdr);
    return CL_CLEAN;
}