bool PackTos::canPack()
{
if (!readFileHeader())
return false;
unsigned char buf[768];
fi->readx(buf, sizeof(buf));
checkAlreadyPacked(buf, sizeof(buf));
if (!checkFileHeader())
throwCantPack("unsupported header flags");
if (file_size < 1024)
throwCantPack("program is too small");
return true;
}
bool PackCom::canPack()
{
unsigned char buf[128];
fi->readx(buf, sizeof(buf));
if (memcmp(buf,"MZ",2) == 0 || memcmp(buf,"ZM",2) == 0 // .exe
|| memcmp (buf,"\xff\xff\xff\xff",4) == 0) // .sys
return false;
if (!fn_has_ext(fi->getName(),"com"))
return false;
checkAlreadyPacked(buf, sizeof(buf));
if (file_size < 1024)
throwCantPack("file is too small");
if (file_size > 0xFF00)
throwCantPack("file is too big for dos/com");
return true;
}
// common part of canPack(), enhanced by subclasses
bool PackUnix::canPack()
{
if (exetype == 0)
return false;
#if defined(__unix__)
// must be executable by owner
if ((fi->st.st_mode & S_IXUSR) == 0)
throwCantPack("file not executable; try 'chmod +x'");
#endif
if (file_size < 4096)
throwCantPack("file is too small");
// info: currently the header is 36 (32+4) bytes before EOF
unsigned char buf[256];
fi->seek(-(off_t)sizeof(buf), SEEK_END);
fi->readx(buf, sizeof(buf));
checkAlreadyPacked(buf, sizeof(buf));
return true;
}
static const
#include "stub/i086-dos16.sys.h"
/*************************************************************************
//
**************************************************************************/
bool PackSys::canPack()
{
unsigned char buf[128];
fi->readx(buf, sizeof(buf));
if (memcmp (buf,"\xff\xff\xff\xff",4) != 0)
return false;
if (!fn_has_ext(fi->getName(),"sys"))
return false;
checkAlreadyPacked(buf, sizeof(buf));
if (file_size < 1024)
throwCantPack("file is too small");
if (file_size > 0x10000)
throwCantPack("file is too big for dos/sys");
return true;
}
// read full kernel into obuf[], gzip-decompress into ibuf[],
// return decompressed size
int PackVmlinuzI386::decompressKernel()
{
// read whole kernel image
obuf.alloc(file_size);
fi->seek(0, SEEK_SET);
fi->readx(obuf, file_size);
{
const upx_byte *base = NULL;
unsigned relocated = 0;
// See startup_32: in linux/arch/i386/boot/compressed/head.S
const upx_byte *p = &obuf[setup_size];
unsigned cpa_0 = 0;
unsigned cpa_1 = 0;
int j;
if (0x205<=h.version) {
cpa_0 = h.kernel_alignment;
cpa_1 = 0u - cpa_0;
} else
for ((p = &obuf[setup_size]), (j= 0); j < 0x200; ++j, ++p) {
if (0==memcmp("\x89\xeb\x81\xc3", p, 4)
&& 0==memcmp("\x81\xe3", 8+ p, 2)) {
// movl %ebp,%ebx
// addl $imm.w,%ebx
// andl $imm.w,%ebx
cpa_0 = 1+ get_te32( 4+ p);
cpa_1 = get_te32(10+ p);
break;
}
}
for ((p = &obuf[setup_size]), (j= 0); j < 0x200; ++j, ++p) {
if (0==memcmp("\x8d\x83", p, 2) // leal d32(%ebx),%eax
&& 0==memcmp("\xff\xe0", 6+ p, 2) // jmp *%eax
) {
relocated = get_te32(2+ p);
}
if (0==memcmp("\xE8\x00\x00\x00\x00\x5D", p, 6)) {
// "call 1f; 1f: pop %ebp" determines actual execution address.
// linux-2.6.21 (spring 2007) and later; upx stub needs work
// unless LOAD_PHYSICAL_ADDR is known.
// Allowed code is: linux-2.6.23/arch/x86/head_32.S 2008-01-01
// call 1f
// 1: popl %ebp
// subl $1b, %ebp # 32-bit immediate
// movl $LOAD_PHYSICAL_ADDR, %ebx
//
if (0==memcmp("\x81\xed", 6+ p, 2) // subl $imm.w,%ebp
&& 0==memcmp("\xbb", 12+ p, 1) ) { // movl $imm.w,%ebx
physical_start = get_te32(13+ p);
} else
if (0==memcmp("\x81\xed", 6+ p, 2) // subl $imm.w,%ebp
&& is_pow2(cpa_0) && (0u-cpa_0)==cpa_1) {
base = (5+ p) - get_te32(8+ p);
config_physical_align = cpa_0;
}
else {
throwCantPack("Unrecognized relocatable kernel");
}
}
// Find "ljmp $__BOOT_CS,$__PHYSICAL_START" if any.
if (0==memcmp("\xEA\x00\x00", p, 3) && 0==(0xf & p[3]) && 0==p[4]) {
/* whole megabyte < 16 MiB */
physical_start = get_te32(1+ p);
break;
}
}
if (base && relocated) {
p = base + relocated;
for (j = 0; j < 0x200; ++j, ++p) {
if (0==memcmp("\x01\x9c\x0b", p, 3) // addl %ebx,d32(%ebx,%ecx)
) {
page_offset = 0u - get_te32(3+ p);
}
if (0==memcmp("\x89\xeb", p, 2) // movl %ebp,%ebx
&& 0==memcmp("\x81\xeb", 2+ p, 2) // subl $imm32,%ebx
) {
physical_start = get_te32(4+ p);
}
}
}
}
checkAlreadyPacked(obuf + setup_size, UPX_MIN(file_size - setup_size, (off_t)1024));
int gzoff = setup_size;
if (0x208<=h.version) {
gzoff += h.payload_offset;
}
for (; gzoff < file_size; gzoff++)
{
// find gzip header (2 bytes magic + 1 byte method "deflated")
int off = find(obuf + gzoff, file_size - gzoff, "\x1F\x8B\x08", 3);
if (off < 0)
break;
gzoff += off;
const int gzlen = (h.version < 0x208) ? (file_size - gzoff) : h.payload_length;
if (gzlen < 256)
break;
// check gzip flag byte
unsigned char flags = obuf[gzoff + 3];
if ((flags & 0xe0) != 0) // reserved bits set
continue;
//printf("found gzip header at offset %d\n", gzoff);
// try to decompress
int klen;
int fd;
off_t fd_pos;
for (;;)
{
klen = -1;
fd = -1;
fd_pos = -1;
// open
fi->seek(gzoff, SEEK_SET);
fd = dup(fi->getFd());
if (fd < 0)
break;
gzFile zf = gzdopen(fd, "rb");
if (zf == NULL)
break;
// estimate gzip-decompressed kernel size & alloc buffer
if (ibuf.getSize() == 0)
ibuf.alloc(gzlen * 3);
// decompress
klen = gzread(zf, ibuf, ibuf.getSize());
fd_pos = lseek(fd, 0, SEEK_CUR);
gzclose(zf);
fd = -1;
if (klen != (int)ibuf.getSize())
break;
// realloc and try again
unsigned s = ibuf.getSize();
ibuf.dealloc();
ibuf.alloc(3 * s / 2);
}
if (fd >= 0)
(void) close(fd);
if (klen <= 0)
continue;
if (klen <= gzlen)
continue;
if (0x208<=h.version && 0==memcmp("\177ELF", ibuf, 4)) {
// Full ELF in theory; for now, try to handle as .bin at physical_start.
// Check for PT_LOAD.p_paddr being ascending and adjacent.
Elf_LE32_Ehdr const *const ehdr = (Elf_LE32_Ehdr const *)(void const *)ibuf;
Elf_LE32_Phdr const *phdr = (Elf_LE32_Phdr const *)(ehdr->e_phoff + (char const *)ehdr);
Elf_LE32_Shdr const *shdr = (Elf_LE32_Shdr const *)(ehdr->e_shoff + (char const *)ehdr);
unsigned hi_paddr = 0, lo_paddr = 0;
unsigned delta_off = 0;
for (unsigned j=0; j < ehdr->e_phnum; ++j, ++phdr) {
if (phdr->PT_LOAD==phdr->p_type) {
unsigned step = (hi_paddr + phdr->p_align - 1) & ~(phdr->p_align - 1);
if (0==hi_paddr) { // first PT_LOAD
if (physical_start!=phdr->p_paddr) {
return 0;
}
delta_off = phdr->p_paddr - phdr->p_offset;
lo_paddr = phdr->p_paddr;
hi_paddr = phdr->p_filesz + phdr->p_paddr;
}
else if (step==phdr->p_paddr
&& delta_off==(phdr->p_paddr - phdr->p_offset)) {
hi_paddr = phdr->p_filesz + phdr->p_paddr;
}
else {
return 0; // Not equivalent to a .bin. Too complex for now.
}
}
}
// FIXME: ascending order is only a convention; might need sorting.
for (unsigned j=1; j < ehdr->e_shnum; ++j) {
if (shdr->SHT_PROGBITS==shdr->sh_type) { // SHT_REL might be intermixed
if (shdr->SHF_EXECINSTR & shdr[j].sh_flags) {
filter_len += shdr[j].sh_size; // FIXME: include sh_addralign
}
else {
break;
}
}
}
memmove(ibuf, (lo_paddr - delta_off) + ibuf, hi_paddr - lo_paddr); // FIXME: set_size
// FIXME: .bss ? Apparently handled by head.S
}
if (opt->force > 0)
return klen;
// some checks
if (fd_pos != file_size)
{
//printf("fd_pos: %ld, file_size: %ld\n", (long)fd_pos, (long)file_size);
// linux-2.6.21.5/arch/i386/boot/compressed/vmlinux.lds
// puts .data.compressed ahead of .text, .rodata, etc;
// so piggy.o need not be last in bzImage. Alas.
//throwCantPack("trailing bytes after kernel image; use option '-f' to force packing");
}
// see /usr/src/linux/arch/i386/kernel/head.S
// 2.4.x: [cli;] cld; mov $...,%eax
if (memcmp(ibuf, "\xFC\xB8", 2) == 0) goto head_ok;
if (memcmp(ibuf, "\xFA\xFC\xB8", 3) == 0) goto head_ok;
// 2.6.21.5 CONFIG_PARAVIRT mov %cs,%eax; test $3,%eax; jne ...;
if (memcmp(ibuf, "\x8c\xc8\xa9\x03\x00\x00\x00\x0f\x85", 9) == 0) goto head_ok;
if (memcmp(ibuf, "\x8c\xc8\xa8\x03\x0f\x85", 6) == 0) goto head_ok;
// 2.6.x: [cli;] cld; lgdt ...
if (memcmp(ibuf, "\xFC\x0F\x01", 3) == 0) goto head_ok;
if (memcmp(ibuf, "\xFA\xFC\x0F\x01", 4) == 0) goto head_ok;
// 2.6.x+grsecurity+strongswan+openwall+trustix: ljmp $0x10,...
if (ibuf[0] == 0xEA && memcmp(ibuf+5, "\x10\x00", 2) == 0) goto head_ok;
// x86_64 2.6.x
if (0xB8==ibuf[0] // mov $...,%eax
&& 0x8E==ibuf[5] && 0xD8==ibuf[6] // mov %eax,%ds
&& 0x0F==ibuf[7] && 0x01==ibuf[8] && 020==(070 & ibuf[9]) // lgdtl
&& 0xB8==ibuf[14] // mov $...,%eax
&& 0x0F==ibuf[19] && 0xA2==ibuf[20] // cpuid
) goto head_ok;
// cmpw $0x207,0x206(%esi) Debian vmlinuz-2.6.24-12-generic
if (0==memcmp("\x66\x81\xbe\x06\x02\x00\x00\x07\x02", ibuf, 9)) goto head_ok;
// testb $0x40,0x211(%esi) Fedora vmlinuz-2.6.25-0.218.rc8.git7.fc9.i686
if (0==memcmp("\xf6\x86\x11\x02\x00\x00\x40", ibuf, 7)) goto head_ok;
// rex.W prefix for x86_64
if (0x48==ibuf[0]) throwCantPack("x86_64 bzImage is not yet supported");
throwCantPack("unrecognized kernel architecture; use option '-f' to force packing");
head_ok:
// FIXME: more checks for special magic bytes in ibuf ???
// FIXME: more checks for kernel architecture ???
return klen;
}
return 0;
}
