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Fix endianness issues in macho module (#2041)
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This is backward compatible change that affects the `magic` field. After this change the value in the `magic` field looks exactly as it looks in the file regardless of the endianness of the current platform, if the file starts with `CA FE BA BE` the value in magic is `0xCAFEBABE`, not `0xBEBAFECA` as it used to be in little-endian architectures.
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@plusvic
plusvic authored Feb 12, 2024
1 parent f3b3027 commit 4369ca6
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3 changes: 2 additions & 1 deletion .github/workflows/build.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -145,5 +145,6 @@ jobs:
./bootstrap.sh &&
./configure --disable-proc-scan --enable-macho &&
make &&
make check
make check &&
cat test-suite.log
"
113 changes: 65 additions & 48 deletions libyara/modules/macho/macho.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -35,49 +35,43 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#define MODULE_NAME macho

// Check for Mach-O binary magic constant.

int is_macho_file_block(const uint32_t* magic)
{
return *magic == MH_MAGIC || *magic == MH_CIGAM || *magic == MH_MAGIC_64 ||
*magic == MH_CIGAM_64;
}

// Check if file is for 32-bit architecture.

int macho_is_32(const uint8_t* magic)
{
// Magic must be [CE]FAEDFE or FEEDFA[CE].
return magic[0] == 0xce || magic[3] == 0xce;
}

// Check if file is for big-endian architecture.

int macho_is_big(const uint8_t* magic)
int macho_is_32(uint32_t magic)
{
// Magic must be [FE]EDFACE or [FE]EDFACF.
return magic[0] == 0xfe;
return magic == MH_MAGIC || magic == MH_CIGAM;
}

// Check for Mach-O fat binary magic constant.

int is_fat_macho_file_block(const uint32_t* magic)
{
return *magic == FAT_MAGIC || *magic == FAT_CIGAM || *magic == FAT_MAGIC_64 ||
*magic == FAT_CIGAM_64;
}

// Check if file is 32-bit fat file.

int macho_fat_is_32(const uint8_t* magic)
int macho_fat_is_32(const uint32_t* magic)
{
// Magic must be CAFEBA[BE].
return magic[3] == 0xbe;
return yr_be32toh(*magic) == FAT_MAGIC;
}

static int should_swap_bytes(const uint32_t magic)
{
// In big-endian platforms byte swapping is needed for little-endian files
// but in little-endian platforms the files that need swapping are the
// the big-endian ones.
#if defined(WORDS_BIGENDIAN)
return magic == MH_CIGAM || magic == MH_CIGAM_64 || magic == FAT_CIGAM ||
magic == FAT_CIGAM_64;
#else
return magic == MH_MAGIC || magic == MH_MAGIC_64 || magic == FAT_MAGIC ||
magic == FAT_MAGIC_64;
#endif
}

static void swap_mach_header(yr_mach_header_64_t* mh)
Expand All @@ -90,7 +84,7 @@ static void swap_mach_header(yr_mach_header_64_t* mh)
mh->sizeofcmds = yr_bswap32(mh->sizeofcmds);
mh->flags = yr_bswap32(mh->flags);

if (!macho_is_32((const uint8_t*) &mh->magic))
if (!macho_is_32(mh->magic))
mh->reserved = yr_bswap32(mh->reserved);
}

Expand Down Expand Up @@ -222,8 +216,8 @@ void macho_handle_unixthread(
return;

// command_size is the size indicated in yr_thread_command_t structure, but
// limited to the data's size because we can't rely on the structure having a
// valid size.
// limited to the data's size because we can't rely on the structure having
// a valid size.
uint32_t command_size = yr_min(size, ((yr_thread_command_t*) data)->cmdsize);

// command_size should be at least the size of yr_thread_command_t.
Expand Down Expand Up @@ -441,13 +435,16 @@ void macho_handle_segment(

yr_set_integer(sec.size, object, "segments[%i].sections[%i].size", i, j);

yr_set_integer(sec.offset, object, "segments[%i].sections[%i].offset", i, j);
yr_set_integer(
sec.offset, object, "segments[%i].sections[%i].offset", i, j);

yr_set_integer(sec.align, object, "segments[%i].sections[%i].align", i, j);

yr_set_integer(sec.reloff, object, "segments[%i].sections[%i].reloff", i, j);
yr_set_integer(
sec.reloff, object, "segments[%i].sections[%i].reloff", i, j);

yr_set_integer(sec.nreloc, object, "segments[%i].sections[%i].nreloc", i, j);
yr_set_integer(
sec.nreloc, object, "segments[%i].sections[%i].nreloc", i, j);

yr_set_integer(sec.flags, object, "segments[%i].sections[%i].flags", i, j);

Expand Down Expand Up @@ -528,13 +525,16 @@ void macho_handle_segment_64(

yr_set_integer(sec.size, object, "segments[%i].sections[%i].size", i, j);

yr_set_integer(sec.offset, object, "segments[%i].sections[%i].offset", i, j);
yr_set_integer(
sec.offset, object, "segments[%i].sections[%i].offset", i, j);

yr_set_integer(sec.align, object, "segments[%i].sections[%i].align", i, j);

yr_set_integer(sec.reloff, object, "segments[%i].sections[%i].reloff", i, j);
yr_set_integer(
sec.reloff, object, "segments[%i].sections[%i].reloff", i, j);

yr_set_integer(sec.nreloc, object, "segments[%i].sections[%i].nreloc", i, j);
yr_set_integer(
sec.nreloc, object, "segments[%i].sections[%i].nreloc", i, j);

yr_set_integer(sec.flags, object, "segments[%i].sections[%i].flags", i, j);

Expand Down Expand Up @@ -563,15 +563,20 @@ void macho_parse_file(
if (size < sizeof(yr_mach_header_64_t))
return;

size_t header_size = macho_is_32(data) ? sizeof(yr_mach_header_32_t)
: sizeof(yr_mach_header_64_t);

// yr_mach_header_64_t is used for storing the header for both for 32-bits and
// 64-bits files. yr_mach_header_64_t is exactly like yr_mach_header_32_t
// but with an extra "reserved" field at the end.
// yr_mach_header_64_t is used for storing the header for both for 32-bits
// and 64-bits files. yr_mach_header_64_t is exactly like
// yr_mach_header_32_t but with an extra "reserved" field at the end.
yr_mach_header_64_t header;

memcpy(&header, data, header_size);
memcpy(&header, data, sizeof(yr_mach_header_64_t));

// The magic number is always handled as big-endian. If the magic bytes are
// CA FE BA BE, then header.magic is 0xCAFEBABE.
header.magic = yr_be32toh(header.magic);

size_t header_size = (header.magic == MH_MAGIC || header.magic == MH_CIGAM)
? sizeof(yr_mach_header_32_t)
: sizeof(yr_mach_header_64_t);

int should_swap = should_swap_bytes(header.magic);

Expand All @@ -587,7 +592,7 @@ void macho_parse_file(
yr_set_integer(header.flags, object, "flags");

// The "reserved" field exists only in 64 bits files.
if (!macho_is_32(data))
if (!macho_is_32(header.magic))
yr_set_integer(header.reserved, object, "reserved");

// The first command parsing pass handles only segments.
Expand Down Expand Up @@ -652,7 +657,8 @@ void macho_parse_file(
switch (command_struct.cmd)
{
case LC_UNIXTHREAD:
macho_handle_unixthread(command, size - parsed_size, base_address, object, context);
macho_handle_unixthread(
command, size - parsed_size, base_address, object, context);
break;
case LC_MAIN:
macho_handle_main(command, size - parsed_size, object, context);
Expand All @@ -672,10 +678,11 @@ void macho_load_fat_arch_header(
uint32_t num,
yr_fat_arch_64_t* arch)
{
if (macho_fat_is_32(data))
if (macho_fat_is_32((uint32_t*) data))
{
yr_fat_arch_32_t* arch32 =
(yr_fat_arch_32_t*) (data + sizeof(yr_fat_header_t) + (num * sizeof(yr_fat_arch_32_t)));
(yr_fat_arch_32_t*) (data + sizeof(yr_fat_header_t) +
(num * sizeof(yr_fat_arch_32_t)));

arch->cputype = yr_be32toh(arch32->cputype);
arch->cpusubtype = yr_be32toh(arch32->cpusubtype);
Expand All @@ -687,7 +694,8 @@ void macho_load_fat_arch_header(
else
{
yr_fat_arch_64_t* arch64 =
(yr_fat_arch_64_t*) (data + sizeof(yr_fat_header_t) + (num * sizeof(yr_fat_arch_64_t)));
(yr_fat_arch_64_t*) (data + sizeof(yr_fat_header_t) +
(num * sizeof(yr_fat_arch_64_t)));

arch->cputype = yr_be32toh(arch64->cputype);
arch->cpusubtype = yr_be32toh(arch64->cpusubtype);
Expand All @@ -707,7 +715,7 @@ void macho_parse_fat_file(
{
size_t fat_arch_sz = sizeof(yr_fat_arch_64_t);

if (macho_fat_is_32(data))
if (macho_fat_is_32((uint32_t*) data))
fat_arch_sz = sizeof(yr_fat_arch_32_t);

if (size < sizeof(yr_fat_header_t))
Expand Down Expand Up @@ -810,10 +818,12 @@ void macho_set_definitions(YR_OBJECT* object)
yr_set_integer(CPU_SUBTYPE_PENTII_M3, object, "CPU_SUBTYPE_PENTII_M3");
yr_set_integer(CPU_SUBTYPE_PENTII_M5, object, "CPU_SUBTYPE_PENTII_M5");
yr_set_integer(CPU_SUBTYPE_CELERON, object, "CPU_SUBTYPE_CELERON");
yr_set_integer(CPU_SUBTYPE_CELERON_MOBILE, object, "CPU_SUBTYPE_CELERON_MOBILE");
yr_set_integer(
CPU_SUBTYPE_CELERON_MOBILE, object, "CPU_SUBTYPE_CELERON_MOBILE");
yr_set_integer(CPU_SUBTYPE_PENTIUM_3, object, "CPU_SUBTYPE_PENTIUM_3");
yr_set_integer(CPU_SUBTYPE_PENTIUM_3_M, object, "CPU_SUBTYPE_PENTIUM_3_M");
yr_set_integer(CPU_SUBTYPE_PENTIUM_3_XEON, object, "CPU_SUBTYPE_PENTIUM_3_XEON");
yr_set_integer(
CPU_SUBTYPE_PENTIUM_3_XEON, object, "CPU_SUBTYPE_PENTIUM_3_XEON");
yr_set_integer(CPU_SUBTYPE_PENTIUM_M, object, "CPU_SUBTYPE_PENTIUM_M");
yr_set_integer(CPU_SUBTYPE_PENTIUM_4, object, "CPU_SUBTYPE_PENTIUM_4");
yr_set_integer(CPU_SUBTYPE_PENTIUM_4_M, object, "CPU_SUBTYPE_PENTIUM_4_M");
Expand Down Expand Up @@ -843,7 +853,8 @@ void macho_set_definitions(YR_OBJECT* object)
yr_set_integer(CPU_SUBTYPE_POWERPC_602, object, "CPU_SUBTYPE_POWERPC_602");
yr_set_integer(CPU_SUBTYPE_POWERPC_603, object, "CPU_SUBTYPE_POWERPC_603");
yr_set_integer(CPU_SUBTYPE_POWERPC_603e, object, "CPU_SUBTYPE_POWERPC_603e");
yr_set_integer(CPU_SUBTYPE_POWERPC_603ev, object, "CPU_SUBTYPE_POWERPC_603ev");
yr_set_integer(
CPU_SUBTYPE_POWERPC_603ev, object, "CPU_SUBTYPE_POWERPC_603ev");
yr_set_integer(CPU_SUBTYPE_POWERPC_604, object, "CPU_SUBTYPE_POWERPC_604");
yr_set_integer(CPU_SUBTYPE_POWERPC_604e, object, "CPU_SUBTYPE_POWERPC_604e");
yr_set_integer(CPU_SUBTYPE_POWERPC_620, object, "CPU_SUBTYPE_POWERPC_620");
Expand Down Expand Up @@ -881,7 +892,8 @@ void macho_set_definitions(YR_OBJECT* object)
yr_set_integer(MH_NOFIXPREBINDING, object, "MH_NOFIXPREBINDING");
yr_set_integer(MH_PREBINDABLE, object, "MH_PREBINDABLE");
yr_set_integer(MH_ALLMODSBOUND, object, "MH_ALLMODSBOUND");
yr_set_integer(MH_SUBSECTIONS_VIA_SYMBOLS, object, "MH_SUBSECTIONS_VIA_SYMBOLS");
yr_set_integer(
MH_SUBSECTIONS_VIA_SYMBOLS, object, "MH_SUBSECTIONS_VIA_SYMBOLS");
yr_set_integer(MH_CANONICAL, object, "MH_CANONICAL");
yr_set_integer(MH_WEAK_DEFINES, object, "MH_WEAK_DEFINES");
yr_set_integer(MH_BINDS_TO_WEAK, object, "MH_BINDS_TO_WEAK");
Expand Down Expand Up @@ -914,7 +926,8 @@ void macho_set_definitions(YR_OBJECT* object)
yr_set_integer(S_CSTRING_LITERALS, object, "S_CSTRING_LITERALS");
yr_set_integer(S_4BYTE_LITERALS, object, "S_4BYTE_LITERALS");
yr_set_integer(S_8BYTE_LITERALS, object, "S_8BYTE_LITERALS");
yr_set_integer(S_NON_LAZY_SYMBOL_POINTERS, object, "S_NON_LAZY_SYMBOL_POINTERS");
yr_set_integer(
S_NON_LAZY_SYMBOL_POINTERS, object, "S_NON_LAZY_SYMBOL_POINTERS");
yr_set_integer(S_LAZY_SYMBOL_POINTERS, object, "S_LAZY_SYMBOL_POINTERS");
yr_set_integer(S_LITERAL_POINTERS, object, "S_LITERAL_POINTERS");
yr_set_integer(S_SYMBOL_STUBS, object, "S_SYMBOL_STUBS");
Expand Down Expand Up @@ -946,7 +959,8 @@ void macho_set_definitions(YR_OBJECT* object)
yr_set_integer(S_ATTR_STRIP_STATIC_SYMS, object, "S_ATTR_STRIP_STATIC_SYMS");
yr_set_integer(S_ATTR_NO_DEAD_STRIP, object, "S_ATTR_NO_DEAD_STRIP");
yr_set_integer(S_ATTR_LIVE_SUPPORT, object, "S_ATTR_LIVE_SUPPORT");
yr_set_integer(S_ATTR_SELF_MODIFYING_CODE, object, "S_ATTR_SELF_MODIFYING_CODE");
yr_set_integer(
S_ATTR_SELF_MODIFYING_CODE, object, "S_ATTR_SELF_MODIFYING_CODE");
yr_set_integer(S_ATTR_DEBUG, object, "S_ATTR_DEBUG");
yr_set_integer(S_ATTR_SOME_INSTRUCTIONS, object, "S_ATTR_SOME_INSTRUCTIONS");
yr_set_integer(S_ATTR_EXT_RELOC, object, "S_ATTR_EXT_RELOC");
Expand Down Expand Up @@ -1048,9 +1062,12 @@ define_function(ep_for_arch_subtype)
uint64_t entry_point = yr_get_integer(module, "file[%i].entry_point", i);
uint64_t file_offset = yr_get_integer(module, "fat_arch[%i].offset", i);

if (entry_point == YR_UNDEFINED) {
if (entry_point == YR_UNDEFINED)
{
return_integer(YR_UNDEFINED);
} else {
}
else
{
return_integer(file_offset + entry_point);
}
}
Expand Down
4 changes: 2 additions & 2 deletions tests/test-macho.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -236,8 +236,8 @@ int main(int argc, char** argv)

assert_true_rule_file(
"import \"macho\" rule test { condition: \
macho.file[0].magic == 0xfeedface and \
macho.file[1].magic == 0xfeedfacf }",
macho.file[0].magic == 0xcefaedfe and \
macho.file[1].magic == 0xcffaedfe }",
"tests/data/tiny-universal");

// Entry points for files (LC_MAIN)
Expand Down

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