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# This is a very simple DEX parser, to get the bytecodes for each method
# Output format will be:
# <class name> <method name> <bytecode as hex string>
import sys
from binascii import hexlify
from struct import pack, unpack
sys.path.append('.')
from androguard.core.dex import DalvikPacker, readsleb128, readuleb128
def read_null_terminated(f):
x = bytearray()
while True:
z = f.read(1)
if ord(z) == 0:
return x
else:
x.append(ord(z))
class MockClassManager:
@property
def packer(self):
return DalvikPacker(0x12345678)
cm = MockClassManager()
class read_dex:
def __init__(self, fname):
methods = [] # Stores method_idx, code_off
with open(fname, "rb") as f:
(
magic,
checksum,
signature,
file_size,
header_size,
endian_tag,
link_size,
link_off,
map_off,
self.string_ids_size,
string_ids_off,
type_ids_size,
type_ids_off,
proto_ids_size,
proto_ids_off,
field_ids_size,
field_ids_off,
method_ids_size,
method_ids_off,
class_defs_size,
class_defs_off,
data_size,
data_off,
) = unpack("<8sI20s20I", f.read(112))
# print("class_defs_size", class_defs_size, "class_defs_off", class_defs_off)
for i in range(class_defs_size):
# class_def_item
f.seek(class_defs_off + i * 8 * 4)
(
class_idx,
access_flags,
superclass_idx,
interfaces_off,
source_file_idx,
annotations_off,
class_data_off,
static_values_off,
) = unpack("<8I", f.read(8 * 4))
# Now parse the class_data_item
if class_data_off == 0:
continue
f.seek(class_data_off)
static_fields_size = readuleb128(cm, f)
instance_fields_size = readuleb128(cm, f)
direct_methods_size = readuleb128(cm, f)
virtual_methods_size = readuleb128(cm, f)
# print("class_data_item:", static_fields_size, instance_fields_size, direct_methods_size, virtual_methods_size)
# We do not need the fields...
for _ in range(static_fields_size + instance_fields_size):
readuleb128(cm, f)
readuleb128(cm, f)
# Now parse methods
method_idx = 0
for _ in range(direct_methods_size):
method_idx_diff = readuleb128(cm, f)
access_flags = readuleb128(cm, f)
code_off = readuleb128(cm, f)
# print("direct_methods", method_idx_diff, access_flags, code_off)
method_idx += method_idx_diff
methods.append([method_idx, code_off])
method_idx = 0
for _ in range(virtual_methods_size):
method_idx_diff = readuleb128(cm, f)
access_flags = readuleb128(cm, f)
code_off = readuleb128(cm, f)
# print("virtual_methods", method_idx_diff, access_flags, code_off)
method_idx += method_idx_diff
methods.append([method_idx, code_off])
# Read the string section
strings = dict()
self.str_raw = dict()
for i in range(self.string_ids_size):
f.seek(string_ids_off + i * 4)
(string_data_off,) = unpack("<I", f.read(4))
f.seek(string_data_off)
utf16_size = readuleb128(cm, f)
s = read_null_terminated(f)
# FIXME this is wrong...
self.str_raw[i] = s
strings[i] = s.decode("UTF-8")
# Read the type section
self.types = dict()
for i in range(type_ids_size):
f.seek(type_ids_off + i * 4)
(descriptor_idx,) = unpack("<I", f.read(4))
self.types[i] = descriptor_idx
method_ids = {}
# Next, we need to parse the method_id section
for i in range(method_ids_size):
f.seek(method_ids_off + i * 8)
class_idx, proto_idx, name_idx = unpack("<HHI", f.read(8))
method_ids[i] = [
strings[self.types[class_idx]],
strings[name_idx],
]
# Now parse the found methods and print to stdout
mres = dict()
for method_idx, code_off in methods:
if code_off == 0:
continue
# We just parse everything manually to get the length, then we save the
# complete code block
f.seek(code_off)
(
registers_size,
ins_size,
outs_size,
tries_size,
debug_info_off,
insns_size,
) = unpack("<4HII", f.read(4 * 2 + 2 * 4))
insns = unpack(
"<{}H".format(insns_size), f.read(2 * insns_size)
)
if tries_size > 0 and insns_size % 2 == 1:
padding = unpack("<H", f.read(2))
if tries_size > 0:
# try_item[tries_size]
tries = unpack(
"<{}".format("".join(["IHH"] * tries_size)),
f.read(8 * tries_size),
)
# encoded_catch_handler_list
size = readuleb128(cm, f)
for _ in range(size):
# encoded_catch_handler
s = readsleb128(cm, f)
for _ in range(abs(s)):
# encoded_type_addr_pair
_ = readuleb128(cm, f)
_ = readuleb128(cm, f)
if s <= 0:
catch_all_addr = readuleb128(cm, f)
l = f.tell() - code_off
f.seek(code_off)
buff = f.read(l)
mres[method_idx] = hexlify(buff)
self.methods = mres
if __name__ == "__main__":
for midx, buff in read_dex(sys.argv[1]).methods.items():
pass
# print(midx, buff)
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