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IOS系统下进程模块的遍历
发布于：2016-4-29 16:17 | 189871次阅读 作者: 管理员 | 原作者: TP | 来自: 原创
一、背景 如前面《Android系统下进程模块的遍历》所述，模块遍历是一种很常见的需求，不同的是实现方式。Android的底层是linux操作系统， 可以通过proc虚拟文件系统获取进程的状态等信息；而IOS的底层是Darwin系统，并没有提供proc虚拟文件系统的功能。那么，该怎样获取进程加载模块的信息呢？这里有两种方法。下面分别介绍。
二、进程模块遍历的实现方式 1. 从内存中的dyld模块内容中获取 dyld是系统的动态链接器，当应用启动时，系统在解析完主模块macho的信息后，会首先运行dyld，通过dyld动态加载应用需要的所有模块，并把每个模块的信息保存到自己的macho文件的“_dyld_all_image_infos”的符号数据中。 Macho是IOS系统上的可执行文件和动态库的格式，类似于Windows系统上的PE、Linux系统上的ELF。它的结构如下图：
它的结构分成三部分：Header、Load Command和Data。其中，Header用来描述cpu架构、Command数目等文件信息；Load Command则描述文件中的段信息；Data包含每个段要引用的数据。Macho的文件信息可以通过MachOView应用来查看，如下图：
使用此种方式实现进程模块遍历算法为：遍历进程的虚拟内存空间，找到macho模块；检查是否是dyld模块，以及包含“_dyld_all_image_infos”符号，如果是，则找到该符号的内容地址；最后，从该符号的内容地址中获取模块信息。此算法涉及到的api有以下几种：
详细代码步骤如下： a)遍历进程的虚拟内存空间，找到macho模块。 FindRegion方法的代码如下： for (;;) { int print = 0; int done = 0;
address = prev_address + prev_size;
/* Check to see if address space has wrapped around. */ if (address == 0) { print = done = 1; }
if (!done) { // Even on iOS, we use VM_REGION_BASIC_INFO_COUNT_64. This works. count = VM_REGION_BASIC_INFO_COUNT; kret = vm_region (mach_task_self(), &address, &size, VM_REGION_BASIC_INFO, (vm_region_info_t) &info, &count, &object_name); if (kret != KERN_SUCCESS) { /* iOS 6 workaround - attempt to reget the task port to avoiD */ /* "(ipc/send) invalid destination port" (1000003 or something) */ kret = vm_region (mach_task_self(), &address, &size, VM_REGION_BASIC_INFO, (vm_region_info_t) &info, &count, &object_name); }
if (kret != KERN_SUCCESS) { printf("FindRegion: mach_vm_region failed for address %p - Error: %x\n", (void *)address, (kret)); size = 0; if (address >= USER_MAX_ADDRESS) return; print = done = 1; } }
// 当前地址不是上一块内存的起始地址+内存长度，表示新的模块 if (address != prev_address + prev_size) { print = 1; }
// 当前内存块的权限和上一个内存块的权限不同 if ((info.protection != prev_info.protection) || (info.max_protection != prev_info.max_protection) || (info.inheritance != prev_info.inheritance) || (info.shared != prev_info.shared) || (info.reserved != prev_info.reserved)) { print = 1; }
if (print) { int print_size = 0; const char *print_size_unit = NULL;
// 从此内存块中找出模块列表信息 bool bRet = FindListOfImage(mach_task_self(), prev_address, prev_size); if (bRet == true) { done = 1; }
/* Quick hack to show size of segment, which GDB does not */ print_size = prev_size; if (print_size > 1024) { print_size /= 1024; print_size_unit = "K"; } if (print_size > 1024) { print_size /= 1024; print_size_unit = "M"; } if (print_size > 1024) { print_size /= 1024; print_size_unit = "G"; } /* End Quick hack */
if (nsubregions > 1) { printf("FindRegion: (%d sub-regions)\n", nsubregions); }
prev_address = address; prev_size = size; memcpy (&prev_info, &info, sizeof (vm_region_basic_info_data_t)); nsubregions = 1;
num_printed++; } else { prev_size += size; nsubregions++; }
if (address >= USER_MAX_ADDRESS) { done = 1; }
if (done) { break; } } b)检查是否是dyld模块，以及包含“_dyld_all_image_infos”符号；如果有，则找到该符号的内存地址。 FindListOfImage方法代码如下： for (int k = 0; k < ((struct mach_header *)pbyMachoHeader)->ncmds; ++k) { if ((unsigned char*)pbyLoadCommand >= (unsigned char*)pbyMachoHeader + size) { printf("FindListOfImage: lc out of range\n"); break; }
printf("FindListOfImage: pbyLoadCommand index:%d, cmd:%d, size:%d\n", k, pbyLoadCommand->cmd, pbyLoadCommand->cmdsize);
if (pbyLoadCommand->cmd == LC_ID_DYLINKER) { struct dylinker_command* pbyDyldCommand = (struct dylinker_command*)pbyLoadCommand; char *pszDyldName = (char *)pbyDyldCommand + pbyDyldCommand->name.offset;
printf("FindListOfImage: %d, pbyDyldCommand name is:%s, name offset:%d, (pbyDyldCommand:%x, pbyDyldCommand name:%x)\n", k, pszDyldName, pbyDyldCommand->name.offset, pbyDyldCommand, pszDyldName);
if (pszDyldName != NULL && strstr(pszDyldName, "/lib/dyld") != NULL) { // 从macho模块中找到"_dyld_all_image_infos"符号的地址 pbyDyldAllImageInfos = GetDyldAllImageInfosAddr((struct mach_header *)pbyMemHeader, "_dyld_all_image_infos"); }
break; }
// find next load command address pbyLoadCommand = (struct load_command *)((char*)pbyLoadCommand + pbyLoadCommand->cmdsize); }
vm_deallocate(t, (vm_offset_t)pbyMachoHeader, nMagicSize);
if (pbyDyldAllImageInfos) { // 解析符号内容 ParseImageInfos(pbyDyldAllImageInfos); return true; } GetDyldAllImageInfosAddr函数代码如下： unsigned long ulImageSlide = (pbyTextHdr->vmsize - pbyTextHdr->filesize) + (pbyDataHdr->vmsize - pbyDataHdr->filesize);
struct nlist *pbySymtabContent = (struct nlist *)( (unsigned long)pbyMachoHeader + pbySymtabHdr->symoff + ulImageSlide ); const char *pbyStrtabContent = (const char *)( (unsigned long)pbyMachoHeader + pbySymtabHdr->stroff + ulImageSlide);
unsigned nSymbolCount = pbySymtabHdr->nsyms; for(unsigned i = 0; i < nSymbolCount; i++) { struct nlist &SymItemRef = pbySymtabContent[i]; if(SymItemRef.n_sect == NO_SECT) { continue; }
char *pbySymItemName = (char *)(pbyStrtabContent + SymItemRef.n_un.n_strx); if(strcmp(pszSymbolName, pbySymItemName) == 0) { unsigned long ulDyldImageInfosOffset = SymItemRef.n_value - pbyTextHdr->vmaddr; pbyDyldAllImageInfos = (void *)( (unsigned long)pbyMachoHeader + ulDyldImageInfosOffset); break; } } c)从” _dyld_all_image_infos“符号内容中获取模块信息。 ParseImageInfos方法代码如下： nDyldInfoCount = sizeof(dyld_all_image_infos); pbyDyldAllImageInfoContent = ReadProcessMemory(mach_task_self(), (vm_address_t)pbyDyldAllImageInfo, &nDyldInfoCount); if (!pbyDyldAllImageInfoContent) { printf("ParseImageInfos: read mem failed 1\n"); break; }
struct dyld_all_image_infos * dyldaii = (struct dyld_all_image_infos *)pbyDyldAllImageInfoContent;
printf("ParseImageInfos: Version: %d, %d images at offset %p\n",dyldaii->version, dyldaii->infoArrayCount, dyldaii->infoArray);
nImageCount = dyldaii->infoArrayCount; nDyldAllImageInfoArrayCount = nImageCount * sizeof(struct dyld_image_info);
pbyDyldAllImageInfoArrayContent = ReadProcessMemory(mach_task_self(), (mach_vm_address_t)dyldaii->infoArray, &nDyldAllImageInfoArrayCount); if (!pbyDyldAllImageInfoArrayContent) { printf("ParseImageInfos: read mem failed 1\n"); break; }
struct dyld_image_info *dii = (struct dyld_image_info *)pbyDyldAllImageInfoArrayContent;
unsigned char *pszImageFilePath; mach_msg_type_number_t nPathNameLen;
for (int i = 0; i < nImageCount; i++) { nPathNameLen = 1024;
pszImageFilePath = ReadProcessMemory(mach_task_self(), (mach_vm_address_t)dii[i].imageFilePath, &nPathNameLen);
ModInfo *pstModInfo = new ModInfo();
if (pszImageFilePath) { pstModInfo->m_pszModPath = strdup((char *)pszImageFilePath); pstModInfo->m_pulModBase = (unsigned long *)dii[i].imageLoadAddress; m_MapModuleList[pstModInfo->m_pszModPath] = pstModInfo;
vm_deallocate(mach_task_self(), (vm_offset_t)pszImageFilePath, 1024); } else {//解决获取不到主进程文件路径的问题 struct dl_info curr_dl_info = {0}; dladdr(dii[i].imageLoadAddress, &curr_dl_info); printf("ParseImageInfos: find process mod: %d:%p:%s\n", i, curr_dl_info.dli_fbase, curr_dl_info.dli_fname);
pstModInfo->m_pszModPath = strdup(curr_dl_info.dli_fname); pstModInfo->m_pulModBase = (unsigned long *)dii[i].imageLoadAddress; m_MapModuleList[pstModInfo->m_pszModPath] = pstModInfo; }
printf("ParseImageInfos: mod[%d] path:%s, mod base:%p\n", i, pstModInfo->m_pszModPath, pstModInfo->m_pulModBase); } 2. 利用dyld的API获取进程模块信息 除了第1种方法外，还有一种更简单的实现进程模块遍历的方法，那就是dyld提供的接口。涉及到的API有以下几种： 如上面介绍： _dlyd_image_count：获取当前已加载的模块数量，但是不是线程安全的。 _dyld_get_image_header：返回当前已加载的某个模块的头部地址。_dyld_get_image_vmaddr_slide：当前已加载的某个模块的虚拟内存偏移值。 _dyld_get_image_name：返回当前已加载的某个模块的名称。_dyld_register_func_for_addr_image：注册添加模块时的回调函数。 _dyld_register_func_for_remove_image：注册移除模块时的回调函数。 使用此方法实现模块遍历的算法为：先用进程中已加载模块的数量，然后逐个获取名称和模块首地址，具体代码如下： void SearchModuleInfo::EnumDyldModules() { m_nModNum = _dyld_image_count();
for (int i = 0; i < m_nModNum; i++) { const mach_header* pstMachoHeader = _dyld_get_image_header(i); const char *pszImageFullPath = _dyld_get_image_name(i);
ModInfo *pstModInfo = new ModInfo(); pstModInfo->m_pszModPath = strdup(pszImageFullPath); pstModInfo->m_pulModBase = (unsigned long *)pstMachoHeader; m_MapModuleList[pstModInfo->m_pszModPath] = pstModInfo;
printf("mod[%d]: %s-%p-%p\n", i, pszImageFullPath, pstMachoHeader, (unsigned long*)_dyld_get_image_vmaddr_slide(i)); } } 三、IOS系统上进程模块遍历的运用场景 获取自己进程的模块加载列表，如是否已加载目标模块。 获取自己进程中某个特定模块的信息，如代码段、数据段是否被修改。 |
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