DEX文件解析---1、dex文件头解析

一、dex文件

dex文件是Android平台上可执行文件的一种文件类型。它的文件格式可以下面这张图概括：

dex文件头一般固定为0x70个字节大小，包含标志、版本号、校验码、sha-1签名以及其他一些方法、类的数量和偏移地址等信息。如下图所示：

二、dex文件头各字段解析

dex文件头包含以下各个字段：

magic:包含了dex文件标识符以及版本，从0x00开始，长度为8个字节

checksum:dex文件校验码，偏移量为:0x08，长度为4个字节。

signature:dex sha-1签名，偏移量为0x0c,长度为20个字节

file_szie:dex文件大小，偏移量为0x20，长度为4个字节

header_size:dex文件头大小，偏移量为0x24，长度为4个字节，一般为0x70

endian_tag:dex文件判断字节序是否交换，偏移量为0x28，长度为4个字节，一般情况下为0x78563412

link_size:dex文件链接段大小，为0则表示为静态链接，偏移量为0x2c，长度为4个字节

link_off:dex文件链接段偏移位置，偏移量为0x30，长度为4个字节

map_off:dex文件中map数据段偏移位置，偏移位置为0x34，长度为4个字节

string_ids_size:dex文件包含的字符串数量，偏移量为0x38，长度为4个字节

string_ids_off:dex文件字符串开始偏移位置，偏移量为0x3c，长度为4个字节

type_ids_size:dex文件类数量，偏移量为0x40，长度为4个字节

type_ids_off:dex文件类偏移位置，偏移量为0x44，长度为4个字节

photo_ids_size:dex文件中方法原型数量，偏移量为0x48，长度为4个字节

photo_ids_off:dex文件中方法原型偏移位置，偏移量为0x4c，长度为4个字节

field_ids_size:dex文件中字段数量，偏移量为0x50，长度为4个字节

field_ids_off:dex文件中字段偏移位置，偏移量为0x54，长度为4个字节

method_ids_size:dex文件中方法数量，偏移量为0x58，长度为4个字节

method_ids_off:dex文件中方法偏移位置，偏移量为0x5c，长度为4个字节

class_defs_size:dex文件中类定义数量，偏移量为0x60，长度为4个字节

class_defs_off:dex文件中类定义偏移位置，偏移量为0x64，长度为4个字节

data_size:dex数据段大小，偏移量为0x68，长度为4个字节

data_off:dex数据段偏移位置，偏移量为0x6c，长度为4个字节

三、dex文件头代码解析示例(python)

dex使用open函数以二进制打开文件，然后使用seek函数移动文件指针，例如magic就是f.seek(0x00)，然后读取相应信息的字节数即可，例如读取版本号f.seek(0x04) f.read(4)，然后做相应打印操作就行，dex文件头较简单，不涉及编码等，所以解析起来感觉脑子都不用带。。。。。具体代码可以看下面或者github，下面附上代码运行图：

四、dex文件头解析实现代码(python实现)

import binascii

def parserHeader(f):

f.seek(0x00)

magic_mask = f.read(4)

magic_mask = binascii.b2a_hex(magic_mask)

magic_mask = str(magic_mask,encoding='utf-8')

print('文件标识符: ',end='')

print(magic_mask)

f.seek(0x04)

magic_version = f.read(4)

magic_version = binascii.b2a_hex(magic_version)

magic_version = str(magic_version,encoding='utf-8')

print('文件版本: ',end='')

print(magic_version)

f.seek(0x08)

checksum = f.read(4)

checksum = binascii.b2a_hex(checksum)

checksum = str(checksum,encoding='utf-8')

print('校验码: ',end='')

print(checksum)

f.seek(0x0c)

signature = f.read(20)

signature = binascii.b2a_hex(signature)

signature = str(signature,encoding='utf-8')

print('SHA-1签名: ',end='')

print(signature)

f.seek(0x20)

file_size = f.read(4)

a = bytearray(file_size)

a.reverse()

file_size = bytes(a)

file_size = binascii.b2a_hex(file_size)

file_size = str(file_size,encoding='utf-8')

print('文件大小: ',end='')

print(int(file_size,16),end='')

print(' byte')

f.seek(0x24)

header_size = f.read(4)

a = bytearray(header_size)

a.reverse()

header_size = bytes(a)

header_size = binascii.b2a_hex(header_size)

header_size = str(header_size,encoding='utf-8')

print('文件头大小: ',end='')

print(int(header_size,16),end='')

print(' byte')

f.seek(0x28)

endian_tag = f.read(4)

endian_tag = binascii.b2a_hex(endian_tag)

endian_tag = str(endian_tag,encoding='utf-8')

print('字节序交换标志: ',end='')

print(endian_tag)

f.seek(0x2c)

link_size = f.read(4)

a = bytearray(link_size)

a.reverse()

link_size = bytes(a)

link_size = binascii.b2a_hex(link_size)

link_size = str(link_size,encoding='utf-8')

print('链接段大小: ',end='')

print(int(link_size,16),end='')

print(' byte')

f.seek(0x30)

link_off = f.read(4)

a = bytearray(link_off)

a.reverse()

link_off = bytes(a)

link_off = binascii.b2a_hex(link_off)

link_off = str(link_off,encoding='utf-8')

print('链接段偏移位置: ',end='')

print(hex(int(link_off,16)))

f.seek(0x34)

map_off = f.read(4)

a = bytearray(map_off)

a.reverse()

map_off = bytes(a)

map_off = binascii.b2a_hex(map_off)

map_off = str(map_off,encoding='utf-8')

print('map数据偏移位置: ',end='')

print(hex(int(map_off,16)))

f.seek(0x38)

stringidsSize = f.read(4)

a = bytearray(stringidsSize)

a.reverse()

stringidsSize = bytes(a)

stringidsSize = binascii.b2a_hex(stringidsSize)

stringidsSize = str(stringidsSize,encoding='utf-8')

print('字符串数量: ',end='')

print(int(stringidsSize,16),end='')

print('(',end='')

print(hex(int(stringidsSize,16)),end='')

print(')')

f.seek(0x3c)

string_ids_off = f.read(4)

a = bytearray(string_ids_off)

a.reverse()

string_ids_off = bytes(a)

string_ids_off = binascii.b2a_hex(string_ids_off)

string_ids_off = str(string_ids_off,encoding='utf-8')

print('字符串偏移位置: ',end='')

print(hex(int(string_ids_off,16)))

f.seek(0x40)

type_ids_size = f.read(4)

a = bytearray(type_ids_size)

a.reverse()

type_ids_size = bytes(a)

type_ids_size = binascii.b2a_hex(type_ids_size)

type_ids_size = str(type_ids_size,encoding='utf-8')

print('类数量: ',end='')

print(int(type_ids_size,16),end='')

print('(',end='')

print(hex(int(type_ids_size,16)),end='')

print(')')

f.seek(0x44)

type_ids_off = f.read(4)

a = bytearray(type_ids_off)

a.reverse()

type_ids_off = bytes(a)

type_ids_off = binascii.b2a_hex(type_ids_off)

type_ids_off = str(type_ids_off,encoding='utf-8')

print('类偏移位置: ',end='')

print(hex(int(type_ids_off,16)))

f.seek(0x48)

photo_ids_size = f.read(4)

a = bytearray(photo_ids_size)

a.reverse()

photo_ids_size = bytes(a)

photo_ids_size = binascii.b2a_hex(photo_ids_size)

photo_ids_size = str(photo_ids_size,encoding='utf-8')

print('方法原型数量: ',end='')

print(int(photo_ids_size,16),end='')

print('(',end='')

print(hex(int(photo_ids_size,16)),end='')

print(')')

f.seek(0x4c)

photo_ids_off = f.read(4)

a = bytearray(photo_ids_off)

a.reverse()

photo_ids_off = bytes(a)

photo_ids_off = binascii.b2a_hex(photo_ids_off)

photo_ids_off = str(photo_ids_off,encoding='utf-8')

print('方法原型偏移位置: ',end='')

print(hex(int(photo_ids_off,16)))

f.seek(0x50)

field_ids_size = f.read(4)

a = bytearray(field_ids_size)

a.reverse()

field_ids_size = bytes(a)

field_ids_size = binascii.b2a_hex(field_ids_size)

field_ids_size = str(field_ids_size,encoding='utf-8')

print('字段数量: ',end='')

print(int(field_ids_size,16),end='')

print('(',end='')

print(hex(int(field_ids_size,16)),end='')

print(')')

f.seek(0x54)

field_ids_off = f.read(4)

a = bytearray(field_ids_off)

a.reverse()

field_ids_off = bytes(a)

field_ids_off = binascii.b2a_hex(field_ids_off)

field_ids_off = str(field_ids_off,encoding='utf-8')

print('字段偏移位置: ',end='')

print(hex(int(field_ids_off,16)))

f.seek(0x58)

method_ids_size = f.read(4)

a = bytearray(method_ids_size)

a.reverse()

method_ids_size = bytes(a)

method_ids_size = binascii.b2a_hex(method_ids_size)

method_ids_size = str(method_ids_size,encoding='utf-8')

print('方法数量: ',end='')

print(int(method_ids_size,16),end='')

print('(',end='')

print(hex(int(method_ids_size,16)),end='')

print(')')

f.seek(0x5c)

method_ids_off = f.read(4)

a = bytearray(method_ids_off)

a.reverse()

method_ids_off = bytes(a)

method_ids_off = binascii.b2a_hex(method_ids_off)

method_ids_off = str(method_ids_off,encoding='utf-8')

print('方法偏移位置: ',end='')

print(hex(int(method_ids_off,16)))

f.seek(0x60)

class_defs_size = f.read(4)

a = bytearray(class_defs_size)

a.reverse()

class_defs_size = bytes(a)

class_defs_size = binascii.b2a_hex(class_defs_size)

class_defs_size = str(class_defs_size,encoding='utf-8')

print('类定义数量: ',end='')

print(int(class_defs_size,16),end='')

print('(',end='')

print(hex(int(class_defs_size,16)),end='')

print(')')

f.seek(0x64)

class_defs_off = f.read(4)

a = bytearray(class_defs_off)

a.reverse()

class_defs_off = bytes(a)

class_defs_off = binascii.b2a_hex(class_defs_off)

class_defs_off = str(class_defs_off,encoding='utf-8')

print('类定义偏移位置: ',end='')

print(hex(int(class_defs_off,16)))

f.seek(0x68)

data_size = f.read(4)

a = bytearray(data_size)

a.reverse()

data_size = bytes(a)

data_size = binascii.b2a_hex(data_size)

data_size = str(data_size,encoding='utf-8')

print('数据段大小: ',end='')

print(int(data_size,16),end='')

print('(',end='')

print(hex(int(data_size,16)),end='')

print(')')

f.seek(0x6c)

data_off = f.read(4)

a = bytearray(data_off)

a.reverse()

data_off = bytes(a)

data_off = binascii.b2a_hex(data_off)

data_off = str(data_off,encoding='utf-8')

print('数据段偏移位置: ',end='')

print(hex(int(data_off,16)))

if __name__ == '__main__':

f = open("C:\\Users\\admin\\Desktop\\android_nx\\classes.dex", 'rb', True)

parserHeader(f)

f.close()

五、相关链接

参考链接