/*
* 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, §ion_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;
}