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
[cpp] view plain copy /* * 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
[cpp] view plain copy /* * 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 [<<<]\n"); printf("[>>>] code by Drizzle [<<<]\n"); printf("[>>>] 2016.05 [<<<]\n"); // 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)\n[*] The wait_times(s) means how long between the two Scans, default 0s \n[*] if successed, you can find the dex file in /data/local/tmp\n[*] Good Luck!\n"); 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!\n"); 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\n", 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\n", 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\n", 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\n", clone_pid); memory_region memory; printf("[*] ptrace [clone_pid] %d\n", 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 ...\n"); // 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!\n"); 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.\n\n"); 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 \n" , 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, "%[^\n]\n", 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()
