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上一篇 android hook 框架 libinject 简介、编译、运行 实际运行了so的注入并调用了注入so里的一个函数，这篇开始分析其实现。
与之前分析的 abdi 项目一样，libinject2 也是依赖于linux系统的 ptrace 系统调用。
这个库首先对ptrace的调用封装了几个helper函数
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; { 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; }
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; }
下面两个函数实现了获取目标进程加载的动态库内部函数的地址，与 adbi 的原理一致，都是利用函数与动态库加载进内存的起始地址的offset一致，来计算的，个人觉得 libinject 在实现同样的功能时代码给 adbi 写得更舒服，这也是研究各种源码的好处，有对比才有高低。
void* get_module_base(pid_t pid, const char* module_name) // 这个函数获取动态库 module_name 加载在进程 pid 后的起始地址 { 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); // 同样是通过解析 maps 文件得到的 } 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) // 这个函数获取目标进程内某个动态库函数的地址 { 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);// 算法一致， local_addr - local_handle 得到 // offset, 然后再加上 remote_handle, 即得到目标进程的函数地址 return ret_addr; }
下面这个是 libinject2 的核心函数：
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; struct pt_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; }
最后是main函数，libinject2 只是注入了一个So到目标进程，并执行了so里的一个函数，还没有真正劫持目标进程的函数
int main(int argc, char** argv) { pid_t target_pid; //target_pid = find_pid_of("/system/bin/surfaceflinger"); target_pid = atoi(argv[1]); 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/local/tmp/libhello.so", "hook_entry", "I‘m parameter!", strlen("I‘m parameter!")); return 0; }
android hook 框架 libinject2 如何实现so注入
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原文地址：http://www.cnblogs.com/jiayy/p/4286864.html
