Android中的so注入(inject)和挂钩(hook) - For both x86 and arm

对于Android for arm上的so注入（inject）和挂钩（hook），网上已有牛人给出了代码-libinject（http://bbs.pediy.com/showthread.php?t=141355）。由于实现中的ptrace函数是依赖于平台的，所以不经改动只能用于arm平台。本文将之扩展了一下，使它能够通用于Android的x86和arm平台。Arm平台部分基本重用了libinject中的代码，其中因为汇编不好移植且容易出错，所以把shellcode.s用ptrace_call替换掉了，另外保留了mmap，用来传字符串参数，当然也可以通过栈来传，但栈里和其它东西混一起，一弄不好就会隔儿了，所以还是保险点好。最后注意设备要root。

首先创建目录及文件：

jni

inject.c

Android.mk

Application.mk

inject.c:

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#include <stdio.h>

#include <stdlib.h>

#include <asm/user.h>

#include <asm/ptrace.h>

#include <sys/ptrace.h>

#include <sys/wait.h>

#include <sys/mman.h>

#include <dlfcn.h>

#include <dirent.h>

#include <unistd.h>

#include <string.h>

#include <elf.h>

#include <android/log.h>

#if defined(__i386__)

#define pt_regs user_regs_struct

#endif

#define ENABLE_DEBUG 1

#if ENABLE_DEBUG

#define LOG_TAG "INJECT"

#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG, fmt, ##args)

#define DEBUG_PRINT(format,args...) \

LOGD(format, ##args)

#else

#define DEBUG_PRINT(format,args...)

#endif

#define CPSR_T_MASK ( 1u << 5 )

const char *libc_path = "/system/lib/libc.so";

const char *linker_path = "/system/bin/linker";

int ptrace_readdata(pid_t pid, uint8_t *src, uint8_t *buf, size_t size)

{

uint32_t i, j, remain;

uint8_t *laddr;

union u {

long val;

char chars[sizeof(long)];

} d;

j = size / 4;

remain = size % 4;

laddr = buf;

for (i = 0; i < j; i ++) {

d.val = ptrace(PTRACE_PEEKTEXT, pid, src, 0);

memcpy(laddr, d.chars, 4);

src += 4;

laddr += 4;

}

if (remain > 0) {

d.val = ptrace(PTRACE_PEEKTEXT, pid, src, 0);

memcpy(laddr, d.chars, remain);

}

return 0;

}

int ptrace_writedata(pid_t pid, uint8_t *dest, uint8_t *data, size_t size)

{

uint32_t i, j, remain;

uint8_t *laddr;

union u {

long val;

char chars[sizeof(long)];

} d;

j = size / 4;

remain = size % 4;

laddr = data;

for (i = 0; i < j; i ++) {

memcpy(d.chars, laddr, 4);

ptrace(PTRACE_POKETEXT, pid, dest, d.val);

dest += 4;

laddr += 4;

}

if (remain > 0) {

d.val = ptrace(PTRACE_PEEKTEXT, pid, dest, 0);

for (i = 0; i < remain; i ++) {

d.chars[i] = *laddr ++;

}

ptrace(PTRACE_POKETEXT, pid, dest, d.val);

}

return 0;

}

#if defined(__arm__)

int ptrace_call(pid_t pid, uint32_t addr, long *params, uint32_t num_params, struct pt_regs* regs)

{

uint32_t i;

for (i = 0; i < num_params && i < 4; i ++) {

regs->uregs[i] = params[i];

}

//

// push remained params onto stack

//

if (i < num_params) {

regs->ARM_sp -= (num_params - i) * sizeof(long) ;

ptrace_writedata(pid, (void *)regs->ARM_sp, (uint8_t *)¶ms[i], (num_params - i) * sizeof(long));

}

regs->ARM_pc = addr;

if (regs->ARM_pc & 1) {

/* thumb */

regs->ARM_pc &= (~1u);

regs->ARM_cpsr |= CPSR_T_MASK;

} else {

/* arm */

regs->ARM_cpsr &= ~CPSR_T_MASK;

}

regs->ARM_lr = 0;

if (ptrace_setregs(pid, regs) == -1

|| ptrace_continue(pid) == -1) {

printf("error\n");

return -1;

}

int stat = 0;

waitpid(pid, &stat, WUNTRACED);

while (stat != 0xb7f) {

if (ptrace_continue(pid) == -1) {

printf("error\n");

return -1;

}

waitpid(pid, &stat, WUNTRACED);

}

return 0;

}

#elif defined(__i386__)

long ptrace_call(pid_t pid, uint32_t addr, long *params, uint32_t num_params, struct user_regs_struct * regs)

{

regs->esp -= (num_params) * sizeof(long) ;

ptrace_writedata(pid, (void *)regs->esp, (uint8_t *)params, (num_params) * sizeof(long));

long tmp_addr = 0x00;

regs->esp -= sizeof(long);

ptrace_writedata(pid, regs->esp, (char *)&tmp_addr, sizeof(tmp_addr));

regs->eip = addr;

if (ptrace_setregs(pid, regs) == -1

|| ptrace_continue( pid) == -1) {

printf("error\n");

return -1;

}

int stat = 0;

waitpid(pid, &stat, WUNTRACED);

while (stat != 0xb7f) {

if (ptrace_continue(pid) == -1) {

printf("error\n");

return -1;

}

waitpid(pid, &stat, WUNTRACED);

}

return 0;

}

#else

#error "Not supported"

#endif

int ptrace_getregs(pid_t pid, struct pt_regs * regs)

{

if (ptrace(PTRACE_GETREGS, pid, NULL, regs) < 0) {

perror("ptrace_getregs: Can not get register values");

return -1;

}

return 0;

}

int ptrace_setregs(pid_t pid, struct pt_regs * regs)

{

if (ptrace(PTRACE_SETREGS, pid, NULL, regs) < 0) {

perror("ptrace_setregs: Can not set register values");

return -1;

}

return 0;

}

int ptrace_continue(pid_t pid)

{

if (ptrace(PTRACE_CONT, pid, NULL, 0) < 0) {

perror("ptrace_cont");

return -1;

}

return 0;

}

int ptrace_attach(pid_t pid)

{

if (ptrace(PTRACE_ATTACH, pid, NULL, 0) < 0) {

perror("ptrace_attach");

return -1;

}

int status = 0;

waitpid(pid, &status , WUNTRACED);

return 0;

}

int ptrace_detach(pid_t pid)

{

if (ptrace(PTRACE_DETACH, pid, NULL, 0) < 0) {

perror("ptrace_detach");

return -1;

}

return 0;

}

void* get_module_base(pid_t pid, const char* module_name)

{

FILE *fp;

long addr = 0;

char *pch;

char filename[32];

char line[1024];

if (pid < 0) {

/* self process */

snprintf(filename, sizeof(filename), "/proc/self/maps", pid);

} else {

snprintf(filename, sizeof(filename), "/proc/%d/maps", pid);

}

fp = fopen(filename, "r");

if (fp != NULL) {

while (fgets(line, sizeof(line), fp)) {

if (strstr(line, module_name)) {

pch = strtok( line, "-" );

addr = strtoul( pch, NULL, 16 );

if (addr == 0x8000)

addr = 0;

break;

}

}

fclose(fp) ;

}

return (void *)addr;

}

void* get_remote_addr(pid_t target_pid, const char* module_name, void* local_addr)

{

void* local_handle, *remote_handle;

local_handle = get_module_base(-1, module_name);

remote_handle = get_module_base(target_pid, module_name);

DEBUG_PRINT("[+] get_remote_addr: local[%x], remote[%x]\n", local_handle, remote_handle);

void * ret_addr = (void *)((uint32_t)local_addr + (uint32_t)remote_handle - (uint32_t)local_handle);

#if defined(__i386__)

if (!strcmp(module_name, libc_path)) {

ret_addr += 2;

}

#endif

return ret_addr;

}

int find_pid_of(const char *process_name)

{

int id;

pid_t pid = -1;

DIR* dir;

FILE *fp;

char filename[32];

char cmdline[256];

struct dirent * entry;

if (process_name == NULL)

return -1;

dir = opendir("/proc");

if (dir == NULL)

return -1;

while((entry = readdir(dir)) != NULL) {

id = atoi(entry->d_name);

if (id != 0) {

sprintf(filename, "/proc/%d/cmdline", id);

fp = fopen(filename, "r");

if (fp) {

fgets(cmdline, sizeof(cmdline), fp);

fclose(fp);

if (strcmp(process_name, cmdline) == 0) {

/* process found */

pid = id;

break;

}

}

}

}

closedir(dir);

return pid;

}

long ptrace_retval(struct pt_regs * regs)

{

#if defined(__arm__)

return regs->ARM_r0;

#elif defined(__i386__)

return regs->eax;

#else

#error "Not supported"

#endif

}

long ptrace_ip(struct pt_regs * regs)

{

#if defined(__arm__)

return regs->ARM_pc;

#elif defined(__i386__)

return regs->eip;

#else

#error "Not supported"

#endif

}

int ptrace_call_wrapper(pid_t target_pid, const char * func_name, void * func_addr, long * parameters, int param_num, struct pt_regs * regs)

{

DEBUG_PRINT("[+] Calling %s in target process.\n", func_name);

if (ptrace_call(target_pid, (uint32_t)func_addr, parameters, param_num, regs) == -1)

return -1;

if (ptrace_getregs(target_pid, regs) == -1)

return -1;

DEBUG_PRINT("[+] Target process returned from %s, return value=%x, pc=%x \n",

func_name, ptrace_retval(regs), ptrace_ip(regs));

return 0;

}

int inject_remote_process(pid_t target_pid, const char *library_path, const char *function_name, const char *param, size_t param_size)

{

int ret = -1;

void *mmap_addr, *dlopen_addr, *dlsym_addr, *dlclose_addr, *dlerror_addr;

void *local_handle, *remote_handle, *dlhandle;

uint8_t *map_base = 0;

uint8_t *dlopen_param1_ptr, *dlsym_param2_ptr, *saved_r0_pc_ptr, *inject_param_ptr, *remote_code_ptr, *local_code_ptr;

struct pt_regs regs, original_regs;

extern uint32_t _dlopen_addr_s, _dlopen_param1_s, _dlopen_param2_s, _dlsym_addr_s, \

_dlsym_param2_s, _dlclose_addr_s, _inject_start_s, _inject_end_s, _inject_function_param_s, \

_saved_cpsr_s, _saved_r0_pc_s;

uint32_t code_length;

long parameters[10];

DEBUG_PRINT("[+] Injecting process: %d\n", target_pid);

if (ptrace_attach(target_pid) == -1)

goto exit;

if (ptrace_getregs(target_pid, ®s) == -1)

goto exit;

/* save original registers */

memcpy(&original_regs, ®s, sizeof(regs));

mmap_addr = get_remote_addr(target_pid, libc_path, (void *)mmap);

DEBUG_PRINT("[+] Remote mmap address: %x\n", mmap_addr);

/* call mmap */

parameters[0] = 0; // addr

parameters[1] = 0x4000; // size

parameters[2] = PROT_READ | PROT_WRITE | PROT_EXEC; // prot

parameters[3] = MAP_ANONYMOUS | MAP_PRIVATE; // flags

parameters[4] = 0; //fd

parameters[5] = 0; //offset

if (ptrace_call_wrapper(target_pid, "mmap", mmap_addr, parameters, 6, ®s) == -1)

goto exit;

map_base = ptrace_retval(®s);

dlopen_addr = get_remote_addr( target_pid, linker_path, (void *)dlopen );

dlsym_addr = get_remote_addr( target_pid, linker_path, (void *)dlsym );

dlclose_addr = get_remote_addr( target_pid, linker_path, (void *)dlclose );

dlerror_addr = get_remote_addr( target_pid, linker_path, (void *)dlerror );

DEBUG_PRINT("[+] Get imports: dlopen: %x, dlsym: %x, dlclose: %x, dlerror: %x\n",

dlopen_addr, dlsym_addr, dlclose_addr, dlerror_addr);

printf("library path = %s\n", library_path);

ptrace_writedata(target_pid, map_base, library_path, strlen(library_path) + 1);

parameters[0] = map_base;

parameters[1] = RTLD_NOW| RTLD_GLOBAL;

if (ptrace_call_wrapper(target_pid, "dlopen", dlopen_addr, parameters, 2, ®s) == -1)

goto exit;

void * sohandle = ptrace_retval(®s);

#define FUNCTION_NAME_ADDR_OFFSET 0x100

ptrace_writedata(target_pid, map_base + FUNCTION_NAME_ADDR_OFFSET, function_name, strlen(function_name) + 1);

parameters[0] = sohandle;

parameters[1] = map_base + FUNCTION_NAME_ADDR_OFFSET;

if (ptrace_call_wrapper(target_pid, "dlsym", dlsym_addr, parameters, 2, ®s) == -1)

goto exit;

void * hook_entry_addr = ptrace_retval(®s);

DEBUG_PRINT("hook_entry_addr = %p\n", hook_entry_addr);

#define FUNCTION_PARAM_ADDR_OFFSET 0x200

ptrace_writedata(target_pid, map_base + FUNCTION_PARAM_ADDR_OFFSET, param, strlen(param) + 1);

parameters[0] = map_base + FUNCTION_PARAM_ADDR_OFFSET;

if (ptrace_call_wrapper(target_pid, "hook_entry", hook_entry_addr, parameters, 1, ®s) == -1)

goto exit;

printf("Press enter to dlclose and detach\n");

getchar();

parameters[0] = sohandle;

if (ptrace_call_wrapper(target_pid, "dlclose", dlclose, parameters, 1, ®s) == -1)

goto exit;

/* restore */

ptrace_setregs(target_pid, &original_regs);

ptrace_detach(target_pid);

ret = 0;

exit:

return ret;

}

int main(int argc, char** argv) {

pid_t target_pid;

target_pid = find_pid_of("/system/bin/surfaceflinger");

if (-1 == target_pid) {

printf("Can't find the process\n");

return -1;

}

//target_pid = find_pid_of("/data/test");

inject_remote_process(target_pid, "/data/libhello.so", "hook_entry", "I'm parameter!", strlen("I'm parameter!"));

return 0;

}

注意上面的/system/bin/surfaceflinger进程我随手写的，你的设备上不一定有。没有的话挑其它的也行，前提是ps命令里能找到。

Android.mk:

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LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := inject

LOCAL_SRC_FILES := inject.c

#shellcode.s

LOCAL_LDLIBS += -L$(SYSROOT)/usr/lib -llog

#LOCAL_FORCE_STATIC_EXECUTABLE := true

include $(BUILD_EXECUTABLE)

Application.mk:

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APP_ABI := x86 armeabi-v7a

运行nkd-build编译成生x86和arm平台下的可执行文件：

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jzj@jzj-laptop:~/workspace/inject_hook/inject_jni$ ndk-build

Install : inject => libs/x86/inject

Install : inject => libs/armeabi-v7a/inject

再来生成要注入的so，创建目录及文件：

jni

hello.c

Android.mk

Application.mk

hello.c:

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#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <android/log.h>

#include <elf.h>

#include <fcntl.h>

#define LOG_TAG "DEBUG"

#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, fmt, ##args)

int hook_entry(char * a){

LOGD("Hook success, pid = %d\n", getpid());

LOGD("Hello %s\n", a);

return 0;

}

Android.mk:

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LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_LDLIBS += -L$(SYSROOT)/usr/lib -llog

#LOCAL_ARM_MODE := arm

LOCAL_MODULE := hello

LOCAL_SRC_FILES := hello.c

include $(BUILD_SHARED_LIBRARY)

Application.mk:

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APP_ABI := x86 armeabi-v7a

运行nkd-build编译成生x86和arm平台下的so：

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jzj@jzj-laptop:~/workspace/inject_hook/hook_so_simple$ ndk-build

Install : libhello.so => libs/x86/libhello.so

Install : libhello.so => libs/armeabi-v7a/libhello.so

然后就可以跑起来试试了，连接root过的Android设备或者打开模拟器。将inject和libhello.so拷入设备，设执行权限，执行：



先看看被注入进程（surfaceflinger）的mmap，可以看到我们的so已经被加载了，紧接着的那一块就是我们mmap出来的：



从logcat中也可以看到so注入成功，并且以被注入进程的身份执行了so中的代码：



简单的注入成功，现在我们再来做一个实验，就是应用这套机制来截获surfaceflinger中的eglSwapBuffers调用，然后用我们自己的函数来替换掉原来的eglSwapBuffers调用。关于截系统中的函数调用网上有例子http://bbs.pediy.com/showthread.php?t=157419，这里依葫芦画瓢。首先将hello.c改下：

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#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <android/log.h>

#include <EGL/egl.h>

#include <GLES/gl.h>

#include <elf.h>

#include <fcntl.h>

#include <sys/mman.h>

#define LOG_TAG "DEBUG"

#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, fmt, ##args)

EGLBoolean (*old_eglSwapBuffers)(EGLDisplay dpy, EGLSurface surf) = -1;

EGLBoolean new_eglSwapBuffers(EGLDisplay dpy, EGLSurface surface)

{

LOGD("New eglSwapBuffers\n");

if (old_eglSwapBuffers == -1)

LOGD("error\n");

return old_eglSwapBuffers(dpy, surface);

}

void* get_module_base(pid_t pid, const char* module_name)

{

FILE *fp;

long addr = 0;

char *pch;

char filename[32];

char line[1024];

if (pid < 0) {

/* self process */

snprintf(filename, sizeof(filename), "/proc/self/maps", pid);

} else {

snprintf(filename, sizeof(filename), "/proc/%d/maps", pid);

}

fp = fopen(filename, "r");

if (fp != NULL) {

while (fgets(line, sizeof(line), fp)) {

if (strstr(line, module_name)) {

pch = strtok( line, "-" );

addr = strtoul( pch, NULL, 16 );

if (addr == 0x8000)

addr = 0;

break;

}

}

fclose(fp) ;

}

return (void *)addr;

}

#define LIBSF_PATH "/system/lib/libsurfaceflinger.so"

int hook_eglSwapBuffers()

{

old_eglSwapBuffers = eglSwapBuffers;

LOGD("Orig eglSwapBuffers = %p\n", old_eglSwapBuffers);

void * base_addr = get_module_base(getpid(), LIBSF_PATH);

LOGD("libsurfaceflinger.so address = %p\n", base_addr);

int fd;

fd = open(LIBSF_PATH, O_RDONLY);

if (-1 == fd) {

LOGD("error\n");

return -1;

}

Elf32_Ehdr ehdr;

read(fd, &ehdr, sizeof(Elf32_Ehdr));

unsigned long shdr_addr = ehdr.e_shoff;

int shnum = ehdr.e_shnum;

int shent_size = ehdr.e_shentsize;

unsigned long stridx = ehdr.e_shstrndx;

Elf32_Shdr shdr;

lseek(fd, shdr_addr + stridx * shent_size, SEEK_SET);

read(fd, &shdr, shent_size);

char * string_table = (char *)malloc(shdr.sh_size);

lseek(fd, shdr.sh_offset, SEEK_SET);

read(fd, string_table, shdr.sh_size);

lseek(fd, shdr_addr, SEEK_SET);

int i;

uint32_t out_addr = 0;

uint32_t out_size = 0;

uint32_t got_item = 0;

int32_t got_found = 0;

for (i = 0; i < shnum; i++) {

read(fd, &shdr, shent_size);

if (shdr.sh_type == SHT_PROGBITS) {

int name_idx = shdr.sh_name;

if (strcmp(&(string_table[name_idx]), ".got.plt") == 0

|| strcmp(&(string_table[name_idx]), ".got") == 0) {

out_addr = base_addr + shdr.sh_addr;

out_size = shdr.sh_size;

LOGD("out_addr = %lx, out_size = %lx\n", out_addr, out_size);

for (i = 0; i < out_size; i += 4) {

got_item = *(uint32_t *)(out_addr + i);

if (got_item == old_eglSwapBuffers) {

LOGD("Found eglSwapBuffers in got\n");

got_found = 1;

uint32_t page_size = getpagesize();

uint32_t entry_page_start = (out_addr + i) & (~(page_size - 1));

mprotect((uint32_t *)entry_page_start, page_size, PROT_READ | PROT_WRITE);

*(uint32_t *)(out_addr + i) = new_eglSwapBuffers;

break;

} else if (got_item == new_eglSwapBuffers) {

LOGD("Already hooked\n");

break;

}

}

if (got_found)

break;

}

}

}

free(string_table);

close(fd);

}

int hook_entry(char * a){

LOGD("Hook success\n");

LOGD("Start hooking\n");

hook_eglSwapBuffers();

return 0;

}

其实这种查找方法有点简单粗暴，要是正式应用的话可以在动态符号表中查找这个符号的got地址。

接着Android.mk改为：

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LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_LDLIBS += -L$(SYSROOT)/usr/lib -llog -lEGL

#LOCAL_ARM_MODE := arm

LOCAL_MODULE := hello

LOCAL_SRC_FILES := hello.c

include $(BUILD_SHARED_LIBRARY)

Application.mk :

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APP_ABI := x86 armeabi-v7a

APP_PLATFORM := android-14

运行ndk-build编译：

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jzj@jzj-laptop:~/workspace/inject_hook/hook_so$ ndk-build

Install : libhello.so => libs/x86/libhello.so

Install : libhello.so => libs/armeabi-v7a/libhello.so

和上面一样运行，查看logcat，我们可以看到surfaceflinger中调用eglSwapBuffers的地址已被替换成我们的版本：

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D/INJECT ( 2231): [+] Injecting process: 1728

D/INJECT ( 2231): [+] get_remote_addr: local[b7e4f000], remote[b7e73000]

D/INJECT ( 2231): [+] Remote mmap address: b7e9fe32

D/INJECT ( 2231): [+] Calling mmap in target process.

D/INJECT ( 2231): [+] Target process returned from mmap, return value=b4f1c000, pc=0

D/INJECT ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]

D/INJECT ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]

D/INJECT ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]

D/INJECT ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]

D/INJECT ( 2231): [+] Get imports: dlopen: b7f84f50, dlsym: b7f84fd0, dlclose: b7f84de0, dlerror: b7f84dc0

D/INJECT ( 2231): [+] Calling dlopen in target process.

D/INJECT ( 2231): [+] Target process returned from dlopen, return value=b7f995ec, pc=0

D/INJECT ( 2231): [+] Calling dlsym in target process.

D/INJECT ( 2231): [+] Target process returned from dlsym, return value=b4f17e10, pc=0

D/INJECT ( 2231): hook_entry_addr = 0xb4f17e10

D/DEBUG ( 1728): Hook success

D/DEBUG ( 1728): Start hooking

D/DEBUG ( 1728): Orig eglSwapBuffers = 0xb7d4a9c0

D/DEBUG ( 1728): libsurfaceflinger.so address = 0xb7f22000

D/DEBUG ( 1728): out_addr = b7f7aff4, out_size = 624

D/DEBUG ( 1728): Found eglSwapBuffers in got

...

D/DEBUG ( 1728): New eglSwapBuffers

D/DEBUG ( 1728): New eglSwapBuffers

D/DEBUG ( 1728): New eglSwapBuffers

...