使用ptrace向已运行进程中注入.so并执行相关函数

原文地址：http://blog.csdn.net/myarrow/article/details/9630377

1. 简介

使用ptrace向已运行进程中注入.so并执行相关函数，其中的“注入”二字的真正含义为：此.so被link到已运行进程（以下简称为：目标进程）空间中，从而.so中的函数在目标进程空间中有对应的地址，然后通过此地址便可在目标进程中进行调用。

到底是如何注入的呢？

本文实现方案为：在目标进程中，通过dlopen把需要注入的.so加载到目标进程的空间中。

2. 如何让目标进程执行dlopen加载.so?

显然，目标进程本来是没有实现通过dlopen来加载我们想注入的.so，为了实现此功能，我们需要目标进程执行一段我们实现的代码，此段代码的功能为通过dlopen来加载一个.so。

3. 【加载.so的实现代码】

加载需要注入的.so的实现代码如下所示：

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.global _dlopen_addr_s @dlopen函数在目标进程中的地址 注：以下全局变化在C中可读写

.global _dlopen_param1_s @dlopen参数1<.so>在目标进程中的地址

.global _dlopen_param2_s @dlopen参数2在目标进程中的地址



.global _dlsym_addr_s @dlsym函数在目标进程中的地址

.global _dlsym_param2_s @dlsym参数2在目标进程中的地址，其实为函数名



.global _dlclose_addr_s @dlcose在目标进程中的地址



.global _inject_start_s @汇编代码段的起始地址

.global _inject_end_s @汇编代码段的结束地址



.global _inject_function_param_s @hook_init参数在目标进程中的地址



.global _saved_cpsr_s @保存CPSR，以便执行完hook_init之后恢复环境

.global _saved_r0_pc_s @保存r0-r15，以便执行完hook_init之后恢复环境





.data



_inject_start_s:

@ debug loop

3:

@sub r1, r1, #0

@B 3b



@ dlopen

ldr r1, _dlopen_param2_s @设置dlopen第二个参数, flag

ldr r0, _dlopen_param1_s @设置dlopen第一个参数 .so

ldr r3, _dlopen_addr_s @设置dlopen函数

blx r3 @执行dlopen函数,返回值位于r0中

subs r4, r0, #0 @把dlopen的返回值soinfo保存在r4中，以方便后面dlclose使用

beq 2f



@dlsym

ldr r1, _dlsym_param2_s @设置dlsym第二个参数，第一个参数已经在r0中了

ldr r3, _dlsym_addr_s @设置dlsym函数

blx r3 @执行dlsym函数，返回值位于r0中

subs r3, r0, #0 @把返回值<hook_init在目标进程中的地址>保存在r3中

beq 1f



@call our function

ldr r0, _inject_function_param_s @设置hook_init第一个参数

blx r3 @执行hook_init

subs r0, r0, #0

beq 2f



1:

@dlclose

mov r0, r4 @把dlopen的返回值设为dlcose的第一个参数

ldr r3, _dlclose_addr_s @设置dlclose函数

blx r3 @执行dlclose函数



2:

@restore context

ldr r1, _saved_cpsr_s @恢复CPSR

msr cpsr_cf, r1

ldr sp, _saved_r0_pc_s @恢复寄存器r0-r15

ldmfd sp, {r0-pc}









_dlopen_addr_s: @初始化_dlopen_addr_s

.word 0x11111111



_dlopen_param1_s:

.word 0x11111111



_dlopen_param2_s:

.word 0x2 @RTLD_GLOBAL



_dlsym_addr_s:

.word 0x11111111



_dlsym_param2_s:

.word 0x11111111



_dlclose_addr_s:

.word 0x11111111



_inject_function_param_s:

.word 0x11111111



_saved_cpsr_s:

.word 0x11111111



_saved_r0_pc_s:

.word 0x11111111





_inject_end_s: @代码结束地址



.space 0x400, 0 @代码段空间大小



.end

4. 如何把【加载.so的实现代码】写入目标进程并启动执行？

为了把【加载.so的实现代码】写入目标进程，主要有以下两步操作：

1) 在目标进程中找到存放【加载.so的实现代码】的空间(通过mmap实现)

2) 把【加载.so的实现代码】写入目标进程指定的空间

3) 启动执行

4.1 在目标进程中找到存放【加载.so的实现代码】的空间

通过mmap来实现，其实现步骤如下：

1) 获取目标进程中mmap地址

2) 把mmap参数据放入r0-r3,另外两个写入目标进程sp

3) pc设置为mmap地址，lr设置为0

4) 把准备好的寄存器写入目标进程(PTRACE_SETREGS),并启动目标进程运行(PTRACE_CONT)

5) 分配的内存首地址位于r0 (PTRACE_GETREGS)

4.2 为【加载.so的实现代码】中的全局变量赋值

1) 获取目标进程中dlopen地址并赋值给_dlopen_addr_s

2) 获取目标进程中dlsym地址并赋值给_dlsym_addr_s

3) 获取目标进程中dlclose地址并赋值给_dlclose_addr_s

4) 把需要加载的.so的路径放入 汇编代码中，并获取此路径在目标进程中的地址然后赋值给_dlopen_param1_s

5) 把需要加载的.so中的hook_init放入 汇编代码中，并获取此路径在目标进程中的地址然后赋值给_dlsym_param2_s

6) 把目标进程中的cpsr保存在_saved_cpsr_s中

7) 把目标进程中的r0-r15存入汇编代码中，并获取此变量在目标进程中的地址然后赋值给_saved_r0_pc_s

8) 通过ptrace( PTRACE_POKETEXT,...)把汇编代码写入目标进程中，起始地址由前面的mmap所分配

9) 把目标进程的pc设置为汇编代码的起始地址，然后调用ptrace(PTRACE_DETACH,...)以启动目标进程执行

5. 把汇编代码写入目标进程并执行的实现代码

5.1 主函数 writecode_to_targetproc

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#include <stdio.h>

#include <stdlib.h>

#include <asm/ptrace.h>

#include <asm/user.h>

#include <asm/ptrace.h>

#include <sys/wait.h>

#include <sys/mman.h>

#include <dlfcn.h>

#include <dirent.h>

#include <unistd.h>

#include <string.h>

#include <android/log.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <sys/stat.h>



#define MAX_PATH 0x100

#define REMOTE_ADDR( addr, local_base, remote_base ) ( (uint32_t)(addr) + (uint32_t)(remote_base) - (uint32_t)(local_base) )



/* write the assembler code into target proc,

* and invoke it to execute

*/

int writecode_to_targetproc(

pid_t target_pid, // target process pid

const char *library_path, // the path of .so that will be

// upload to target process

const char *function_name, // .so init fucntion e.g. hook_init

void *param, // the parameters of init function

size_t param_size ) // number of parameters

{

int ret = -1;

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

void *local_handle, *remote_handle, *dlhandle;

uint8_t *map_base;

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 global variable in the assembler code

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];



// make target_pid as its child process and stop

if ( ptrace_attach( target_pid ) == -1 )

return -1;



// get the values of 18 registers from target_pid

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

goto exit;



// save original registers

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



// get mmap address from target_pid

// the mmap is the address of mmap in the cur process

mmap_addr = get_remote_addr( target_pid, "/system/lib/libc.so", (void *)mmap );



// set mmap parameters

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



// execute the mmap in target_pid

if ( ptrace_call( target_pid, (uint32_t)mmap_addr, parameters, 6, ®s ) == -1 )

goto exit;



// get the return values of mmap <in r0>

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

goto exit;



// get the start address for assembler code

map_base = (uint8_t *)regs.ARM_r0;



// get the address of dlopen, dlsym and dlclose in target process

dlopen_addr = get_remote_addr( target_pid, "/system/bin/linker", (void *)dlopen );

dlsym_addr = get_remote_addr( target_pid, "/system/bin/linker", (void *)dlsym );

dlclose_addr = get_remote_addr( target_pid, "/system/bin/linker", (void *)dlclose );



// set the start address for assembler code in target process

remote_code_ptr = map_base + 0x3C00;



// set the start address for assembler code in cur process

local_code_ptr = (uint8_t *)&_inject_start_s;



// set global variable of assembler code

// and these address is in the target process

_dlopen_addr_s = (uint32_t)dlopen_addr;

_dlsym_addr_s = (uint32_t)dlsym_addr;

_dlclose_addr_s = (uint32_t)dlclose_addr;



code_length = (uint32_t)&_inject_end_s - (uint32_t)&_inject_start_s;



dlopen_param1_ptr = local_code_ptr + code_length + 0x20;

dlsym_param2_ptr = dlopen_param1_ptr + MAX_PATH;

saved_r0_pc_ptr = dlsym_param2_ptr + MAX_PATH;

inject_param_ptr = saved_r0_pc_ptr + MAX_PATH;





// save library path to assembler code global variable

strcpy( dlopen_param1_ptr, library_path );

_dlopen_param1_s = REMOTE_ADDR( dlopen_param1_ptr, local_code_ptr, remote_code_ptr );





// save function name to assembler code global variable

strcpy( dlsym_param2_ptr, function_name );

_dlsym_param2_s = REMOTE_ADDR( dlsym_param2_ptr, local_code_ptr, remote_code_ptr );



// save cpsr to assembler code global variable

_saved_cpsr_s = original_regs.ARM_cpsr;



// save r0-r15 to assembler code global variable

memcpy( saved_r0_pc_ptr, &(original_regs.ARM_r0), 16 * 4 ); // r0 ~ r15

_saved_r0_pc_s = REMOTE_ADDR( saved_r0_pc_ptr, local_code_ptr, remote_code_ptr );



// save function parameters to assembler code global variable

memcpy( inject_param_ptr, param, param_size );

_inject_function_param_s = REMOTE_ADDR( inject_param_ptr, local_code_ptr, remote_code_ptr );



// write the assembler code into target process

// now the values of global variable is in the target process space

ptrace_writedata( target_pid, remote_code_ptr, local_code_ptr, 0x400 );



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



// set sp and pc to the start address of assembler code

regs.ARM_sp = (long)remote_code_ptr;

regs.ARM_pc = (long)remote_code_ptr;



// set registers for target process

ptrace_setregs( target_pid, ®s );



// make the target_pid is not a child process of cur process

// and make target_pid continue to running

ptrace_detach( target_pid );



// now finish it successfully

ret = 0;



exit:

return ret;

}

5.2 attach目标进程ptrace_attach

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int ptrace_attach( pid_t pid )

{

// after PTRACE_ATTACH, the proc<pid> will stop

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

{

perror( "ptrace_attach" );

return -1;

}



// wait proc<pid> stop

waitpid( pid, NULL, WUNTRACED );



// after PTRACE_SYSCALL, the proc<pid> will continue,

// but when exectue sys call function, proc<pid> will stop

if ( ptrace( PTRACE_SYSCALL, pid, NULL, 0 ) < 0 )

{

perror( "ptrace_syscall" );

return -1;

}



// wait proc<pid> stop

waitpid( pid, NULL, WUNTRACED );



return 0;

}

5.3 获取目标进程寄存器值ptrace_getregs

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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;

}

5.4 获取目标进程中指定模块中指定函数的地址get_remote_addr

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/* find the start address of module whose name is module_name

* in the designated process

*/

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 );



return (void *)( (uint32_t)local_addr + (uint32_t)remote_handle - (uint32_t)local_handle );

}

5.5 在目标进程中执行指定函数ptrace_call

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

{

uint32_t i;



// put the first 4 parameters into r0-r3

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

{

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

}



// push remained params into 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) );

}

// set the pc to func <e.g: mmap> that will be executed

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;

}



// when finish this func, pid will stop

regs->ARM_lr = 0;



// set the regsister and start to execute

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

|| ptrace_continue( pid ) == -1 )

{

return -1;

}



// wait pid finish work and stop

waitpid( pid, NULL, WUNTRACED );



return 0;

}

5.6 把代码写入目标进程指定地址ptrace_writedata

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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;

}

5.7 设置目标进程寄存器ptrace_setregs

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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;

}

5.8 detach目标进程ptrace_detach

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int ptrace_detach( pid_t pid )

{

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

{

perror( "ptrace_detach" );

return -1;

}



return 0;

}

6. 需要被加载的.so

需要被加载的.so例子程序如下，其目的是替换目标进程libapp.so中的strlen函数。其主要实现见hook_init。

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int g_isInit = 0;

pthread_t g_hThread;



__attribute__((visibility("default"))) void hook_init( char *args )

{

if( g_isInit == 1 )

{

printf("i am already in!");

return;

}



void* soHandle = NULL;



// the libapp.so is a .so of target process, and it call strcmp

soHandle = dlopen( "libapp.so", RTLD_GLOBAL );

if( soHandle != NULL )

{

g_realstrcmp = NULL;

replaceFunc( soHandle, "strcmp", my_strcmp, (void**)&g_realstrcmp );



int ret = pthread_create( &g_hThread, NULL, my_thread, NULL );

if( ret != 0 )

{

printf("create thread error:%d", ret );

}



g_isInit = 1;

}



}

6.1 替换函数replaceFunc

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// replace function of libapp.so

// e.g: replace strcmp of libapp.so with my_strcmp

void replaceFunc(void *handle,const char *name, void* pNewFun, void** pOldFun )

{



if(!handle)

return;



soinfo *si = (soinfo*)handle;

Elf32_Sym *symtab = si->symtab;

const char *strtab = si->strtab;

Elf32_Rel *rel = si->plt_rel;

unsigned count = si->plt_rel_count;

unsigned idx;



// these external functions that are called by libapp.so

// is in the plt_rel

for(idx=0; idx<count; idx++)

{

unsigned type = ELF32_R_TYPE(rel->r_info);

unsigned sym = ELF32_R_SYM(rel->r_info);

unsigned reloc = (unsigned)(rel->r_offset + si->base);

char *sym_name = (char *)(strtab + symtab[sym].st_name);



if(strcmp(sym_name, name)==0)

{

*pOldFun = (void *)*((unsigned*)reloc);

*((unsigned*)reloc)= pNewFun;

break;

}

rel++;

}

}

6.2 新函数及其它函数

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// global function variable, save the address of strcmp of libapp.so

int (*g_realstrcmp)(const char *s1, const char *s2);



// my strcmp function

int my_strcmp(const char *s1, const char *s2)

{

if( g_realstrcmp != NULL )

{

int nRet = g_realstrcmp( s1, s2 );

printf("***%s: s1=%s, s2=%s\n",__FUNCTION__, s1, s2 );

return nRet;

}



return -1;

}





// create a thread

void* my_thread( void* pVoid )

{

int sock;

sock = socket(AF_INET, SOCK_DGRAM, 0);

if( sock < -1 )

{

printf("create socket failed!\n");

return 0;

}



struct sockaddr_in addr_serv;

int len;

memset(&addr_serv, 0, sizeof(struct sockaddr_in));

addr_serv.sin_family = AF_INET;

addr_serv.sin_port = htons(9999);

addr_serv.sin_addr.s_addr = inet_addr("127.0.0.1");

len = sizeof(addr_serv);



int flags = fcntl( sock, F_GETFL, 0);

fcntl( sock, F_SETFL, flags | O_NONBLOCK);

int nPreState = -1;

unsigned char data=0;

while( 1 )

{

data++;

sendto( sock, &data, sizeof( data ), 0, (struct sockaddr *)&addr_serv, sizeof( addr_serv ) );

usleep( 30000 );

}

}