iOS Kernel Heap Armageddon - Hakim

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OSObject Retain Count • reference counter for objects • 32 bit field - but only lower 16 bit are the reference counter • upper 16 bit used as collection reference counter • reference counting stops at 65534 -> memory leak 0x00 0x04 vtable ptr + 8 retainCount 0x08 Stefan Esser • iOS Kernel Heap Armageddon REVISITED • July 2012 • 68
Overwriting an OSObject in Memory • overwriting or corrupting the vtable ptr • everything the kernel will do with the object will trigger code exec 0x00 0x04 vtable ptr + 8 retainCount • overwriting the retain count 0x08 • might allow freeing the object early • and code execution through dangling references • use after free Stefan Esser • iOS Kernel Heap Armageddon REVISITED • July 2012 • 69
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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
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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: OSObject Memory Layout 0x00 0x04 vt
Page 71 and 72: OSArray Memory Layout and Overwriti
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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