iOS Kernel Heap Armageddon - Hakim

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OSString Memory Layout and Overwriting It • overwriting flags controls if string is freed or not • overwriting length • might allow kernel heap information leaks • on free memory end up in wrong kalloc zone • overwriting string ptr 0x00 0x04 0x08 0x0C 0x10 0x14 vtable ptr + 8 retainCount flags length string ptr • allows kernel heap information leaks • on free arbitrary pointer ends up in kalloc zone kalloc()ed memory Stefan Esser • iOS Kernel Heap Armageddon REVISITED • July 2012 • 70
OSArray Memory Layout and Overwriting It 0x00 0x04 0x08 vtable ptr + 8 retainCount updateStamp 0x00 0x04 kalloc(capacity * sizeof(void *)) • overwriting updateStamp + fOptions = not interesting OSObject ptr OSObject ptr 0x0C fOptions 0x08 NULL 0x10 array ptr 0x0C 0x14 0x18 0x1C 0x20 0x24 count capacity capacityIncrement reserved • overwriting count + capacity + capacityIncrement • might allow uninitialized memory access • or different consufing attacks agains kalloc zones • overwriting array ptr + array itself • allows supplying arbitrary OSObject ptrs • any action the kernel performs on these will result in code exec Stefan Esser • iOS Kernel Heap Armageddon REVISITED • July 2012 • 71
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http://www.sektioneins.de iOS Kerne
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DISCLAIMER iOS 6 • is in beta =>
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So what is this talk about? • zon
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Some Kernel Zones $ zprint kalloc e
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iOS Kernel Zone Allocator 101 • k
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iOS Kernel Zone Allocator 101 • z
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iOS Kernel Zone Allocator 101 • w
Page 15 and 16:
Exploiting the freelist in iOS 6
Page 17 and 18:
Overview Managers and Wrappers not
Page 19 and 20: kalloc() • kalloc() is a wrapper
Page 21 and 22: kfree() • kfree() is a bit specia
Page 23 and 24: _MALLOC() • _MALLOC() is a wrappe
Page 25 and 26: _MALLOC() in iOS 5.x void *_MALLOC(
Page 27 and 28: What about kern_os_malloc(), new an
Page 29 and 30: mcache / slab could and might fill
Page 31 and 32: kernel_memory_allocate • “maste
Page 33 and 34: Cross Zone Attacks • what is the
Page 35 and 36: Visualization of Zone Page Allocati
Page 61 and 62: Zone Page Allocation Distribution (
Page 63 and 64: Cross Memory Allocator Attacks •
Page 65 and 66: iOS Kernel C++ • iOS kernel‘s l
Page 67 and 68: OSObject Memory Layout 0x00 0x04 vt
Page 69: Overwriting an OSObject in Memory
Page 73 and 74: “Generic“ Technique to control
Page 75 and 76: Heap Feng Shui / Heap Massage / ...
Page 77 and 78: OSUnserializeXML() • deserializat
Page 79 and 80: How does the parser work? (II) •
Page 81 and 82: How does the parser work? (IV) •
Page 83 and 84: How does the parser work? (VI) •
Page 85 and 86: How does the parser work? (VIII)
Page 87 and 88: Heap Spraying (Remember?) • alloc
Page 89 and 90: Heap Spraying • allocate repeated
Page 91 and 92: Heap Spraying • allocate repeated
Page 93 and 94: Fill Arbitrary Sized Memory Blocks
Page 95 and 96: Poking Holes into Allocated Data
Page 97 and 98: Extra: Keeping Data Allocated • s
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iOS Kernel Heap Armageddon - Hakim

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