本文博客地址：http://blog.csdn.net/qq1084283172/article/details/53561622
在前面的博客中已经介绍了Android的脱壳工具DexExtractor的原理和使用说明，接下来就来分析一下另一个Android的脱壳工具drizzleDumper的原理和使用说明。drizzleDumper脱壳工具的作者是Drizzle.Risk，他是在strazzere大神的android-unpacker脱壳工具的基础上修改过来的drizzleDumper，他在完成drizzleDumper脱壳工具的时候，对某数字加固、ijiami、bangbang加固进行了脱壳测试，效果比较理想。drizzleDumper脱壳工具是一款基于内存特征搜索的dex文件dump脱壳工具。
一、drizzleDumper脱壳工具的相关链接和讨论：
github地址：https://github.com/DrizzleRisk/drizzleDumper#drizzledumper
freebuf地址：http://www.freebuf.com/sectool/105147.html
看雪地址：http://bbs.pediy.com/showthread.php?goto=nextoldest&nojs=1&t=213174
android-unpacker地址：https://github.com/strazzere/android-unpacker/tree/master/native-unpacker
二、drizzleDumper脱壳工具的原理分析（见代码的注释）：
drizzleDumper工作的原理是root环境下，通过ptrace附加需要脱壳的apk进程，然后在脱壳的apk进程的内存中进行dex文件的特征搜索，当搜索到dex文件时，进行dex文件的内存dump。
drizzleDumper.h头文件
/*
* drizzleDumper Code By Drizzle.Risk
* file: drizzleDumper.h
*/
#include <stdlib.h>
#include <stdio.h>
#include <dirent.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <linux/user.h>
#ifdef HAVE_STDINT_H
#include <stdint.h> /* C99 */
typedef uint8_t u1;
typedef uint16_t u2;
typedef uint32_t u4;
typedef uint64_t u8;
typedef int8_t s1;
typedef int16_t s2;
typedef int32_t s4;
typedef int64_t s8;
#else
typedef unsigned char u1;
typedef unsigned short u2;
typedef unsigned int u4;
typedef unsigned long long u8;
typedef signed char s1;
typedef signed short s2;
typedef signed int s4;
typedef signed long long s8;
#endif
/*
* define kSHA1DigestLen
*/
enum { kSHA1DigestLen = 20,
kSHA1DigestOutputLen = kSHA1DigestLen*2 +1 };
/*
* define DexHeader
*/
typedef struct DexHeader {
u1 magic[8]; /* includes version number */
u4 checksum; /* adler32 checksum */
u1 signature[kSHA1DigestLen]; /* SHA-1 hash */
u4 fileSize; /* length of entire file */
u4 headerSize; /* offset to start of next section */
u4 endianTag;
u4 linkSize;
u4 linkOff;
u4 mapOff;
u4 stringIdsSize;
u4 stringIdsOff;
u4 typeIdsSize;
u4 typeIdsOff;
u4 protoIdsSize;
u4 protoIdsOff;
u4 fieldIdsSize;
u4 fieldIdsOff;
u4 methodIdsSize;
u4 methodIdsOff;
u4 classDefsSize;
u4 classDefsOff;
u4 dataSize;
u4 dataOff;
} DexHeader;
//#define ORIG_EAX 11
static const char* static_safe_location = "/data/local/tmp/";
static const char* suffix = "_dumped_";
typedef struct {
uint32_t start;
uint32_t end;
} memory_region;
uint32_t get_clone_pid(uint32_t service_pid);
uint32_t get_process_pid(const char* target_package_name);
char *determine_filter(uint32_t clone_pid, int memory_fd);
int find_magic_memory(uint32_t clone_pid, int memory_fd, memory_region *memory ,const char* file_name);
int peek_memory(int memory_file, uint32_t address);
int dump_memory(const char *buffer , int len , char each_filename[]);
int attach_get_memory(uint32_t pid);
drizzleDumper.c实现文件
/*
* drizzleDumper Code By Drizzle.Risk
* file: drizzleDumper.c
*/
#include "drizzleDumper.h"
// 主函数main
int main(int argc, char *argv[]) {
printf("[>>>] This is drizzleDumper [<<<]
");
printf("[>>>] code by Drizzle [<<<]
");
printf("[>>>] 2016.05 [<<<]
");
// 脱壳工具drizzleDumper在工作的实收需要3个参数（需要脱壳的apk的package_name、脱壳等待的时间wait_times(s)）
if(argc <= 1)
{
printf("[*] Useage : ./drizzleDumper package_name wait_times(s)
[*] The wait_times(s) means how long between the two Scans, default 0s
[*] if successed, you can find the dex file in /data/local/tmp
[*] Good Luck!
");
return 0;
}
// 由于脱壳的原理是基于进程的ptrace，需要有root权限
if(getuid() != 0)
{
printf("[*] Device Not root!
");
return -1;
}
double wait_times = 0.01;
// 脱壳工具drizzleDumper在工作的实收需要3个参数（需要脱壳的apk的package_name、脱壳等待的时间wait_times(s)）
if(argc >= 3)
{
// 获取加固脱壳的等待时间
wait_times = strtod(argv[2], NULL);
printf("[*] The wait_times is %ss
", argv[2]);
}
// 获取需要被脱壳的加固apk的包名
char *package_name = argv[1];
printf("[*] Try to Find %s
", package_name);
uint32_t pid = -1;
int i = 0;
int mem_file;
uint32_t clone_pid;
char *extra_filter;
char *dumped_file_name;
// 进入循环
while(1)
{
// 休眠等待一段时间
sleep(wait_times);
pid = -1;
// 获取加固需要被脱壳的apk的进程pid
pid = get_process_pid(package_name);
// 判断获取的进程pid是否有效
if(pid < 1 || pid == -1)
{
continue;
}
printf("[*] pid is %d
", pid);
// 获取进程pid的一个线程tid，方便后面进行ptrace附加
clone_pid = get_clone_pid(pid);
if(clone_pid <= 0)
{
continue;
}
printf("[*] clone pid is %d
", clone_pid);
memory_region memory;
printf("[*] ptrace [clone_pid] %d
", clone_pid);
// 对指定pid进程的克隆即tid进程ptrace附加，获取指定pid进程的内存模块基址
mem_file = attach_get_memory(clone_pid);
// 对获取到的内存有效数据的进行校验3次即最多进行3次脱壳尝试
if(mem_file == -10201)
{
continue;
}
else if(mem_file == -20402)
{
//continue;
}
else if(mem_file == -30903)
{
//continue
}
/****
*static const char* static_safe_location = "/data/local/tmp/";
*static const char* suffix = "_dumped_";
****/
// 申请内存空间保存内存dump出来的dex文件的名称
dumped_file_name = malloc(strlen(static_safe_location) + strlen(package_name) + strlen(suffix));
// 格式化生成存dump出来的dex文件的名称
sprintf(dumped_file_name, "%s%s%s", static_safe_location, package_name, suffix);
printf("[*] Scanning dex ...
");
// 通过ptrace附件目标pid进程，在目标进程的pid中进行dex文件的搜索然后进行内存dump
if(find_magic_memory(clone_pid, mem_file, &memory, dumped_file_name) <= 0)
{
printf("[*] The magic was Not Found!
");
ptrace(PTRACE_DETACH, clone_pid, NULL, 0);
close(mem_file);
continue;
}
else
{
// dex的内存dump成功，跳出循环
close(mem_file);
ptrace(PTRACE_DETACH, clone_pid, NULL, 0);
break;
}
}
printf("[*] Done.
");
return 1;
}
// 获取指定进程的一个线程tid
uint32_t get_clone_pid(uint32_t service_pid)
{
DIR *service_pid_dir;
char service_pid_directory[1024];
// 格式化字符串
sprintf(service_pid_directory, "/proc/%d/task/", service_pid);
// 查询指定进程的pid的线程TID的信息
if((service_pid_dir = opendir(service_pid_directory)) == NULL)
{
return -1;
}
struct dirent* directory_entry = NULL;
struct dirent* last_entry = NULL;
// 获取指定pid进程的线程TID
while((directory_entry = readdir(service_pid_dir)) != NULL)
{
last_entry = directory_entry;
}
if(last_entry == NULL)
return -1;
closedir(service_pid_dir);
// 返回获取到的指定pid的线程tid
return atoi(last_entry->d_name);
}
// 通过运行的apk的名称的获取进程的pid
uint32_t get_process_pid(const char *target_package_name)
{
char self_pid[10];
sprintf(self_pid, "%u", getpid());
DIR *proc = NULL;
if((proc = opendir("/proc")) == NULL)
return -1;
struct dirent *directory_entry = NULL;
while((directory_entry = readdir(proc)) != NULL)
{
if (directory_entry == NULL)
return -1;
if (strcmp(directory_entry->d_name, "self") == 0 || strcmp(directory_entry->d_name, self_pid) == 0)
continue;
char cmdline[1024];
snprintf(cmdline, sizeof(cmdline), "/proc/%s/cmdline", directory_entry->d_name);
FILE *cmdline_file = NULL;
if((cmdline_file = fopen(cmdline, "r")) == NULL)
continue;
char process_name[1024];
fscanf(cmdline_file, "%s", process_name);
fclose(cmdline_file);
if(strcmp(process_name, target_package_name) == 0)
{
closedir(proc);
return atoi(directory_entry->d_name);
}
}
closedir(proc);
return -1;
}
// 在目标进程的内存空间中进行dex文件的搜索
int find_magic_memory(uint32_t clone_pid, int memory_fd, memory_region *memory , const char *file_name) {
int ret = 0;
char maps[2048];
// 格式化字符串得到/proc/pid/maps
snprintf(maps, sizeof(maps), "/proc/%d/maps", clone_pid);
FILE *maps_file = NULL;
// 打开文件/proc/pid/maps，获取指定pid进程的内存分布信息
if((maps_file = fopen(maps, "r")) == NULL)
{
printf(" [+] fopen %s Error
" , maps);
return -1;
}
char mem_line[1024];
// 循环读取文件/proc/pid/maps中的pid进程的每一条内存分布信息
while(fscanf(maps_file, "%[^
]
", mem_line) >= 0)
{
char mem_address_start[10]={0};
char mem_address_end[10]={0};
char mem_info[1024]={0};
// 解析pid进程的的内存分布信息--内存分布起始地址、内存分布结束地址等
sscanf(mem_line, "%8[^-]-%8[^ ]%*s%*s%*s%*s%s", mem_address_start, mem_address_end, mem_info);
memset(mem_line , 0 ,1024);
// 获取内存分布起始地址的大小
uint32_t mem_start = strtoul(mem_address_start, NULL, 16);
memory->start = mem_start;
// 获取内存分布结束地址的大小
memory->end = strtoul(mem_address_end, NULL, 16);
// 获取实际的内存区间大小
int len = memory->end - memory->start;
// 过滤掉不符合条件的内存分布区间
if(len <= 10000)
{//too small
continue;
}
else if(len >= 150000000)
{//too big
continue;
}
char each_filename[254] = {0};
char randstr[10] = {0};
sprintf(randstr ,"%d", rand()%9999);
// 拼接字符串得到dump的dex文件的生成名称
strncpy(each_filename , file_name , 200); //防溢出
strncat(each_filename , randstr , 10);
strncat(each_filename , ".dex" , 4);
// 先将pid进程内存文件句柄的指针置文件开头
lseek64(memory_fd , 0 , SEEK_SET);
// 设置pid进程内存文件句柄的指针为内存分布起始地址
off_t r1 = lseek64(memory_fd , memory->start , SEEK_SET);
if(r1 == -1)
{
//do nothing
}
else
{
// 根据内存分布区间的大小申请内存空间
char *buffer = malloc(len);
// 读取pid进程的指定区域的内存数据
ssize_t readlen = read(memory_fd, buffer, len);
printf("meminfo: %s ,len: %d ,readlen: %d, start: %x
", mem_info, len, readlen, memory->start);
// 对读取的内存分布区域的数据进行dex文件的扫描和查找
if(buffer[1] == 'E' && buffer[2] == 'L' && buffer[3] == 'F')
{
free(buffer);
continue;
}
// 查找到dex文件所在的内存区域
if(buffer[0] == 'd' && buffer[1] == 'e' && buffer[2] == 'x' && buffer[3] == '
' && buffer[4] == '0' && buffer[5] == '3')
{
printf(" [+] find dex, len : %d , info : %s
" , readlen , mem_info);
DexHeader header;
char real_lenstr[10]={0};
// 获取内存区域中dex文件的文件头信息
memcpy(&header , buffer ,sizeof(DexHeader));
sprintf(real_lenstr , "%x" , header.fileSize);
// 通过dex文件头信息，获取到整个dex文件的大小
long real_lennum = strtol(real_lenstr , NULL, 16);
printf(" [+] This dex's fileSize: %d
", real_lennum);
// 对dex文件所在的内存区域进行内存dump
if(dump_memory(buffer , len , each_filename) == 1)
{
// 打印dump的dex文件的名称
printf(" [+] dex dump into %s
", each_filename);
free(buffer);
continue;
}
else
{
printf(" [+] dex dump error
");
}
}
free(buffer);
}
// 前面的内存方法搜索没有查找dex文件的内存，尝试下面的内存+8位置进行搜索
// 具体什么原因没太明白??
lseek64(memory_fd , 0 , SEEK_SET); //保险，先归零
r1 = lseek64(memory_fd , memory->start + 8 , SEEK_SET); //不用 pread，因为pread用的是lseek
if(r1 == -1)
{
continue;
}
else
{
char *buffer = malloc(len);
ssize_t readlen = read(memory_fd, buffer, len);
if(buffer[0] == 'd' && buffer[1] == 'e' && buffer[2] == 'x' && buffer[3] == '
' && buffer[4] == '0' && buffer[5] == '3')
{
printf(" [+] Find dex! memory len : %d
" , readlen);
DexHeader header;
char real_lenstr[10]={0};
// 获取内存dex文件的文件头信息
memcpy(&header , buffer ,sizeof(DexHeader));
sprintf(real_lenstr , "%x" , header.fileSize);
// 通过dex文件头信息，获取到整个dex文件的大小
long real_lennum = strtol(real_lenstr , NULL, 16);
printf(" [+] This dex's fileSize: %d
", real_lennum);
// 对dex文件所在的内存区域进行内存dump
if(dump_memory(buffer , len , each_filename) == 1)
{
printf(" [+] dex dump into %s
", each_filename);
free(buffer);
continue; //如果本次成功了，就不尝试其他方法了
}
else
{
printf(" [+] dex dump error
");
}
}
free(buffer);
}
}
fclose(maps_file);
return ret;
}
// 从内存中dump数据到文件中
int dump_memory(const char *buffer , int len , char each_filename[])
{
int ret = -1;
// 创建文件
FILE *dump = fopen(each_filename, "wb");
// 将需要dump的内存数据写入到/data/local/tmp文件路径下
if(fwrite(buffer, len, 1, dump) != 1)
{
ret = -1;
}
else
{
ret = 1;
}
fclose(dump);
return ret;
}
// 获取指定附加pid进程的内存模块基址
int attach_get_memory(uint32_t pid) {
char mem[1024];
bzero(mem,1024);
// 格式化字符串得到字符串/proc/pid/mem
snprintf(mem, sizeof(mem), "/proc/%d/mem", pid);
int ret = -1;
int mem_file;
// 尝试ptrace附加目标pid进程
ret = ptrace(PTRACE_ATTACH, pid, NULL, NULL);
// 对ptrace附加目标pid进程的操作结果进行判断
if (0 != ret)
{
int err = errno; //这时获取errno
if(err == 1) //EPERM
{
return -30903; //代表已经被跟踪或无法跟踪
}
else
{
return -10201; //其他错误(进程不存在或非法操作)
}
}
else
{
// ptrace附加目标进程pid成功，获取指定pid进程的内存模块基址
// 获取其它进程的内存模块基址，需要root权限
if(!(mem_file = open(mem, O_RDONLY)))
{
return -20402; //打开错误
}
}
return mem_file;
}
drizzleDumper的编译配置文件Android.mk
LOCAL_PATH := $(call my-dir)
TARGET_PIE := true
NDK_APP_PIE := true
include $(CLEAR_VARS)
# 需要编译的源码文件
LOCAL_SRC_FILES :=
drizzleDumper.c
LOCAL_C_INCLUDE :=
drizzleDumper.h
definitions.h
LOCAL_MODULE := drizzleDumper
LOCAL_MODULE_TAGS := optional
# Allow execution on android-16+
# 支持PIE
LOCAL_CFLAGS += -fPIE
LOCAL_LDFLAGS += -fPIE -pie
# 编译生成可执行ELF文件
include $(BUILD_EXECUTABLE)
include $(call all-makefiles-under,$(LOCAL_PATH))
三、drizzleDumper的使用说明
关于drizzleDumper的使用，作者已经在freebuf的文章中已经讲的很详细了，具体的修改的地方也指出来了。
四、下面就使用nexcus 5的已经root的真机进行drizzleDumper的脱壳实战（以com.qihoo.freewifi为例）：
在cmd控制台的条件下，执行cd命令进入到存放drizzleDumper的文件夹，然后将drizzleDumper文件推送到android手机的/data/local/tmp文件夹下并赋予可执行权限，然后根据每种android加固的特点，选择需要脱壳的apk和drizzleDumper运行的先后顺序，调整能够脱壳成功的过程。这里使用的com.qihoo.freewifi为例，先运行com.qihoo.freewifi程序，然后adb shell条件下su提权，执行drizzleDumper的脱壳操作，等待2秒。
cd xxxxx/drizzleDumper
adb push drizzleDumper /data/local/tmp
adb shell chmod 0777 /data/local/tmp/drizzleDumper
adb shell #进入androd系统的shell
su #获取root权限
./data/local/tmp/drizzleDumper com.qihoo.freewifi 2 #执行脱壳操作
说明：对脱壳是否成功，这个估计有一定的概率性，主要的目的是学习工具作者的脱壳思想和方法，自己去实践，不管怎样谢谢工具的作者Drizzle.Risk，代码中有理解错误的地方希望大牛不吝赐。
编译好的drizzleDumper文件和代码的打包下载地址：http://download.csdn.net/detail/qq1084283172/9707768。
参考网址：
http://www.freebuf.com/sectool/105147.html
https://github.com/DrizzleRisk/drizzleDumper