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dexparser.py
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dexparser.py
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import mmap
import struct
import disassembler
import zlib
import hashlib
import logging
def uleb128_value(m, off):
size = 1
result = ord(m[off+0: off+1])
if result > 0x7f :
cur = ord(m[off+1:off+2])
result = (result & 0x7f) | ((cur & 0x7f) << 7)
size += 1
if cur > 0x7f :
cur = ord(m[off+2:off+3])
result |= ((cur & 0x7f) << 14)
size += 1
if cur > 0x7f :
cur = ord(m[off+3:off+4])
result |= ((cur & 0x7f) << 21)
size += 1
if cur > 0x7f :
cur = ord(m[off+4:off+5])
result |= (cur << 28)
size += 1
return result, size
def encoded_field(mmap, offset):
myoff = offset
field_idx_diff, size = uleb128_value(mmap, myoff)
myoff += size
access_flags, size = uleb128_value(mmap, myoff)
myoff += size
size = myoff - offset
return [field_idx_diff, access_flags, size]
def encoded_method(mmap, offset):
myoff = offset
method_idx_diff, size = uleb128_value(mmap, myoff)
myoff += size
access_flags, size = uleb128_value(mmap, myoff)
myoff += size
code_off, size = uleb128_value(mmap, myoff)
myoff += size
size = myoff - offset
return [method_idx_diff, access_flags, code_off, size]
def encoded_annotation(mmap, offset):
myoff = offset
type_idx_diff, size = uleb128_value(mmap, myoff)
#print hex(type_idx_diff), size
myoff += size
size_diff, size = uleb128_value(mmap, myoff)
#print hex(size_diff), size
myoff += size
name_idx_diff, size = uleb128_value(mmap, myoff)
#print hex(name_idx_diff)
myoff += size
value_type = mmap[myoff:myoff+1]
encoded_value = mmap[myoff+1:myoff+2]
return [type_idx_diff, size_diff, name_idx_diff, value_type, encoded_value]
class Dex:
def __init__(self, filedir):
f = open(filedir, 'r+b')
m = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_WRITE)
self.mmap = m
magic = m[0:8]
checksum = struct.unpack('<L', m[8:0xC])[0]
signiture = m[0xC:0x20]
file_size = struct.unpack('<L', m[0x20:0x24])[0]
header_size = struct.unpack('<L', m[0x24:0x28])[0]
endian_tag = struct.unpack('<L', m[0x28:0x2C])[0]
link_size = struct.unpack('<L', m[0x2C:0x30])[0]
link_off = struct.unpack('<L', m[0x30:0x34])[0]
map_off = struct.unpack('<L', m[0x34:0x38])[0]
string_ids_size = struct.unpack('<L', m[0x38:0x3C])[0]
string_ids_off = struct.unpack('<L', m[0x3C:0x40])[0]
type_ids_size = struct.unpack('<L', m[0x40:0x44])[0]
type_ids_off = struct.unpack('<L', m[0x44:0x48])[0]
proto_ids_size = struct.unpack('<L', m[0x48:0x4C])[0]
proto_ids_off = struct.unpack('<L', m[0x4C:0x50])[0]
field_ids_size = struct.unpack('<L', m[0x50:0x54])[0]
field_ids_off = struct.unpack('<L', m[0x54:0x58])[0]
method_ids_size = struct.unpack('<L', m[0x58:0x5C])[0]
method_ids_off = struct.unpack('<L', m[0x5C:0x60])[0]
class_defs_size = struct.unpack('<L', m[0x60:0x64])[0]
class_defs_off = struct.unpack('<L', m[0x64:0x68])[0]
data_size = struct.unpack('<L', m[0x68:0x6C])[0]
data_off = struct.unpack('<L', m[0x6C:0x70])[0]
header_data = {}
header_data['magic' ] = magic
header_data['checksum' ] = checksum
header_data['signiture' ] = signiture
header_data['file_size' ] = file_size
header_data['header_size' ] = header_size
header_data['endian_tag' ] = endian_tag
header_data['link_size' ] = link_size
header_data['link_off' ] = link_off
header_data['map_off' ] = map_off
header_data['string_ids_size'] = string_ids_size
header_data['string_ids_off' ] = string_ids_off
header_data['type_ids_size' ] = type_ids_size
header_data['type_ids_off' ] = type_ids_off
header_data['proto_ids_size' ] = proto_ids_size
header_data['proto_ids_off' ] = proto_ids_off
header_data['field_ids_size' ] = field_ids_size
header_data['field_ids_off' ] = field_ids_off
header_data['method_ids_size'] = method_ids_size
header_data['method_ids_off' ] = method_ids_off
header_data['class_defs_size'] = class_defs_size
header_data['class_defs_off' ] = class_defs_off
header_data['data_size' ] = data_size
header_data['data_off' ] = data_off
self.header = header_data
self.classdef_list = []
self.typeid_list = []
self.string_list = []
self.method_list = []
self.typeid_list = []
self.classdef_list = self.get_classdef_list()
self.typeid_list = self.get_typeid_list()
self.string_list = self.get_string_list()
self.method_list = self.get_method_list()
self.typeid_list = self.get_typeid_list()
def mmapdata(self):
return self.mmap
def header_info(self):
return self.header
def checksum(self):
return "%x" % self.header["checksum"]
def get_string_list(self):
if self.string_list:
return self.string_list
string_ids_size = self.header['string_ids_size']
string_ids_off = self.header['string_ids_off']
for i in range(string_ids_size):
off = struct.unpack('<L', self.mmap[string_ids_off + (i*4) : string_ids_off + (i*4) + 4 ])[0]
c_size, u1eb12b_length = uleb128_value(self.mmap, off)
c_char = self.mmap[off+u1eb12b_length:off+u1eb12b_length+c_size]
self.string_list.append(c_char)
return self.string_list
def get_typeid_list(self):
if self.typeid_list:
return self.typeid_list
type_ids_size = self.header['type_ids_size']
type_ids_off = self.header['type_ids_off']
for i in range(type_ids_size):
idx = struct.unpack('<L', self.mmap[type_ids_off + (i*4) : type_ids_off + (i*4) + 4])[0]
self.typeid_list.append(idx)
return self.typeid_list
def get_typeid_list(self):
if self.typeid_list:
return self.typeid_list
type_ids_size = self.header['type_ids_size']
type_ids_off = self.header['type_ids_off']
for i in range(type_ids_size):
idx = struct.unpack('<L', self.mmap[type_ids_off + (i*4) : type_ids_off + (i*4) + 4])[0]
self.typeid_list.append(idx)
return self.typeid_list
def get_classdef_list(self):
if self.classdef_list:
return self.classdef_list
class_defs_off = self.header['class_defs_off']
class_defs_size = self.header['class_defs_size']
for i in range(class_defs_size):
class_idx = struct.unpack('<L', self.mmap[class_defs_off+(i*32) :class_defs_off+(i*32)+4])[0]
access_flag = struct.unpack('<L', self.mmap[class_defs_off+(i*32)+4 :class_defs_off+(i*32)+8])[0]
superclass_idx = struct.unpack('<L', self.mmap[class_defs_off+(i*32)+8 :class_defs_off+(i*32)+12])[0]
interfaces_off = struct.unpack('<L', self.mmap[class_defs_off+(i*32)+12:class_defs_off+(i*32)+16])[0]
source_file_idx = struct.unpack('<L', self.mmap[class_defs_off+(i*32)+16:class_defs_off+(i*32)+20])[0]
annotation_off = struct.unpack('<L', self.mmap[class_defs_off+(i*32)+20:class_defs_off+(i*32)+24])[0]
class_data_off = struct.unpack('<L', self.mmap[class_defs_off+(i*32)+24:class_defs_off+(i*32)+28])[0]
static_values_off = struct.unpack('<L', self.mmap[class_defs_off+(i*32)+28:class_defs_off+(i*32)+32])[0]
sorted_access = [i for i in disassembler.ACCESS_ORDER if i & access_flag]
self.classdef_list.append([class_idx, [disassembler.access_flag_classes[flag] for flag in sorted_access], superclass_idx, interfaces_off, source_file_idx, annotation_off, class_data_off, static_values_off])
return self.classdef_list
def get_method_list(self):
if self.method_list:
return self.method_list
method_ids_size = self.header['method_ids_size']
method_ids_off = self.header['method_ids_off']
for i in range(method_ids_size):
class_idx = struct.unpack('<H', self.mmap[method_ids_off+(i*8) :method_ids_off+(i*8)+2])[0]
proto_idx = struct.unpack('<H', self.mmap[method_ids_off+(i*8)+2:method_ids_off+(i*8)+4])[0]
name_idx = struct.unpack('<L', self.mmap[method_ids_off+(i*8)+4:method_ids_off+(i*8)+8])[0]
self.method_list.append([class_idx, proto_idx, name_idx])
return self.method_list
def get_classdata(self, offset):
static_field_list = []
instance_field_list = []
direct_method_list = []
virtual_method_list = []
static_fields, sf_size = uleb128_value(self.mmap, offset)
offset += sf_size
instance_fields, if_size = uleb128_value(self.mmap, offset)
offset += if_size
direct_methods, dm_size = uleb128_value(self.mmap, offset)
offset += dm_size
virtual_methods, vm_size = uleb128_value(self.mmap, offset)
offset += vm_size
for i in range(static_fields):
field_idx_diff, access_flags, size = encoded_field(self.mmap, offset)
if i == 0:
diff = field_idx_diff
else:
diff += field_idx_diff
static_field_list.append([diff, access_flags])
offset += size
#print static_field_list
for i in range(instance_fields):
field_idx_diff, access_flags, size = encoded_field(self.mmap, offset)
if i == 0:
diff = field_idx_diff
else:
diff += field_idx_diff
instance_field_list.append([diff, access_flags])
offset += size
#print instance_field_list
for i in range(direct_methods):
method_idx_diff, access_flags, code_off, size = encoded_method(self.mmap, offset)
if i == 0:
diff = method_idx_diff
else:
diff += method_idx_diff
direct_method_list.append([diff, access_flags, code_off])
offset += size
#print direct_method_list
for i in range(virtual_methods):
method_idx_diff, access_flags, code_off, size = encoded_method(self.mmap, offset)
if i == 0:
diff = method_idx_diff
else:
diff += method_idx_diff
virtual_method_list.append([diff, access_flags, code_off])
offset += size
#print virtual_method_list
return [static_field_list, instance_field_list, direct_method_list, virtual_method_list]
def get_classdef(self, cname):
list_size = len(self.classdef_list)
for i in range(list_size):
classdef = self.classdef_list[i]
class_idx = classdef[0]
typeid = self.typeid_list[class_idx]
if str(self.string_list[typeid])[2:-1] == cname:
return i, classdef
return -1, []
def get_method_sig(self, protoidx):
protoid_list_off = self.header["proto_ids_off"]
protoid_list_size = self.header["proto_ids_size"]
#get DexProtoId
shorty_idx = struct.unpack('<L', self.mmap[protoid_list_off+(protoidx*12) :protoid_list_off+(protoidx*12)+ 4])[0]
return_type_idx = struct.unpack('<L', self.mmap[protoid_list_off+(protoidx*12)+4:protoid_list_off+(protoidx*12)+ 8])[0]
param_off = struct.unpack('<L', self.mmap[protoid_list_off+(protoidx*12)+8:protoid_list_off+(protoidx*12)+12])[0]
#get return type
return_type = str(self.string_list[self.typeid_list[return_type_idx]])[2:-1]
#get argument type
arg_num = self.mmap[param_off]
sig = "("
for i in range(arg_num):
typeidx = struct.unpack("<H", self.mmap[param_off + 4 + i*2 : param_off + 6 + i*2])[0]
sig += str(self.string_list[self.typeid_list[typeidx]])[2:-1]
sig += ")"
sig += return_type
return sig
def find_dexmethod(self, method_list, fname, sig):
list_size = len(method_list)
for i in range(list_size):
dexmethod = method_list[i]
protoidx = self.method_list[dexmethod[0]][1]
nameidx = self.method_list[dexmethod[0]][2]
if str(self.string_list[nameidx])[2:-1] != fname:
continue
if self.get_method_sig(protoidx) == sig:
return i, dexmethod
return -1, []
def get_dexmethod_off_from_classdata(self, classdata_off, fname, sig):
offset = classdata_off
static_fields, sf_size = uleb128_value(self.mmap, offset)
offset += sf_size
instance_fields, if_size = uleb128_value(self.mmap, offset)
offset += if_size
direct_methods, dm_size = uleb128_value(self.mmap, offset)
offset += dm_size
virtual_methods, vm_size = uleb128_value(self.mmap, offset)
offset += vm_size
for i in range(static_fields):
field_idx_diff, access_flags, size = encoded_field(self.mmap, offset)
if i == 0:
diff = field_idx_diff
else:
diff += field_idx_diff
offset += size
for i in range(instance_fields):
field_idx_diff, access_flags, size = encoded_field(self.mmap, offset)
if i == 0:
diff = field_idx_diff
else:
diff += field_idx_diff
offset += size
for i in range(direct_methods):
method_idx_diff, access_flags, code_off, size = encoded_method(self.mmap, offset)
if i == 0:
diff = method_idx_diff
else:
diff += method_idx_diff
protoidx = self.method_list[diff][1]
nameidx = self.method_list[diff][2]
if str(self.string_list[nameidx])[2:-1] == fname:
if self.get_method_sig(protoidx) == sig:
return diff, offset
offset += size
for i in range(virtual_methods):
method_idx_diff, access_flags, code_off, size = encoded_method(self.mmap, offset)
if i == 0:
diff = method_idx_diff
else:
diff += method_idx_diff
protoidx = self.method_list[diff][1]
nameidx = self.method_list[diff][2]
if str(self.string_list[nameidx])[2:-1] == fname:
if self.get_method_sig(protoidx) == sig:
return diff, offset
offset += size
return -1, -1
def save(self):
self.mmap.close()
def set_access_flags(self, offset, accessflags, lens):
write_size = 0
#print("%x" % ((accessflags & 0x7f) + 0x80))
while accessflags > 127:
self.mmap[offset : offset + 1] = struct.pack("B", 0x80 + (accessflags & 0x7f))
write_size += 1
accessflags = accessflags >> 7
offset += 1
self.mmap[offset : offset + 1] = struct.pack("B", accessflags)
write_size += 1
offset += 1
while write_size < lens:
if write_size < lens - 1:
self.mmap[offset : offset + 1] = struct.pack("B", 0x80)
else:
self.mmap[offset : offset + 1] = struct.pack("B", 0x00)
offset += 1
write_size += 1
def update_checksum(self):
checkdata = self.mmap[12:]
checksum = zlib.adler32(checkdata)
self.mmap[8:12] = struct.pack('<I',checksum & 0xffffffff)
def update_signature(self):
sigdata = self.mmap[32:]
sha1 = hashlib.sha1()
sha1.update(sigdata)
signature = sha1.digest()
self.mmap[12 : 32] = struct.pack("20s", signature)
#change java funtion to native funtion
def java2native(self, cname, fname, sig):
classdef_index, classdef = self.get_classdef(cname)
classdata_off = classdef[6]
methodid_index, dexmethod_offset = self.get_dexmethod_off_from_classdata(classdata_off, fname, sig)
#print(classdef_index, methodid_index, dexmethod_offset)
#logging.info("classdef_index: %d" % classdef_index)
#logging.info("methodid_index: %d" % methodid_index)
#logging.info("dexmethod_offset: %d" % dexmethod_offset)
#modify
methodidx, size = uleb128_value(self.mmap, dexmethod_offset)
dexmethod_offset += size
accessflags, asize = uleb128_value(self.mmap, dexmethod_offset)
codeoff, csize = uleb128_value(self.mmap, dexmethod_offset + asize)
#logging.info("codeoff: %d" % codeoff)
self.set_access_flags(dexmethod_offset, accessflags | 0x100, asize + csize)
return codeoff