Demystifying the Secure Enclave Processor

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SEPOS Mitigations Summary Mitigation Present Notes Stack Cookie Protection Yes (…) ‘GARD’ – mostly ineffective Memory Layout Randomization User No Kernel No Image base: 0xF0001000 Stack Guard Pages Yes/No Not for main thread Object Map Guard Pages Yes Gaps between object mappings Heap Metadata Protection No Null-Page Protection No Must be root task to map page No-Execute Protection Yes Both XN and PXN
Attack Surface: BootROM • Effectively only two major attack surfaces ▫ IMG4 Parser Memory Corruption Logic Flaws ▫ Hardware based • Only minor anti-exploit mitigations present ▫ No ASLR ▫ Basic stack guard ▫ One decent bug = game over
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Demystifying the Secure Enclave Pro
Page 3 and 4:
Introduction • iPhone 5S was a te
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Secure (?) Enclave Processor • Ve
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Glossary • AP: Application Proces
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Page 11 and 12:
Dedicated Hardware Peripherals •
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Physical Memory • Dedicated BootR
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Page 17 and 18:
SEP Initialization - Page Tables
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SEP Initialization - Second Stage
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SEP Boot Flow SEP AP Configure TZ0
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Memory Encryption Setup • Use “
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• Mode actually used is AES-256-X
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SEP Boot Flow: Stage 3 SEP AP Ackno
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Sending SEPOS • SEPOS is sent (op
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Boot-loading: Img4 • SEP uses the
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Img4 - Manifest • The manifest (A
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IMG4 - Manifest Properties (2/2) He
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Reversing SEP’s Img4 Parser: Stag
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Img4 Parsing Flow SEP AP Decode Pay
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Secure Mailbox • Actual mailbox i
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Interrupt-based Message Passing •
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Mailbox Message Format • A single
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SEP Endpoint • Each endpoint is r
Page 51 and 52: SEP Endpoints (2/2) Index Name Driv
Page 53 and 54: Control Endpoint Opcodes Opcode Nam
Page 55 and 56: Endpoint Registration (AP) Start Cr
Page 57 and 58: Demystifying the Secure Enclave Pro
Page 59 and 60: L4-embedded • Modified version of
Page 61 and 62: SEPOS Architecture SEP Applications
Page 63 and 64: System Calls (1/2) Num Name Descrip
Page 65 and 66: Privileged System Calls • Some sy
Page 67 and 68: SEPOS (INIT) • Initial process on
Page 69 and 70: Application List • Includes infor
Page 71 and 72: Bootstrap Server • Implements the
Page 73 and 74: Privileged Methods • An applicati
Page 75 and 76: proc_has_privilege( ) int proc_has_
Page 77 and 78: Entitlement Assignment int proc_cre
Page 79 and 80: SEP Drivers • Hosts all SEP drive
Page 81 and 82: Driver Interaction Retrieves SEPD t
Page 83 and 84: SEP Services • Hosts various SEP
Page 85 and 86: Service Interaction Retrieves sepS
Page 87 and 88: Demystifying the Secure Enclave Pro
Page 89 and 90: Attack Surface: AKF Endpoints • E
Page 91 and 92: Attack Surface: Endpoint Handler SE
Page 93 and 94: Address Space Layout - Image • SE
Page 95 and 96: Stack Corruptions • The main thre
Page 97 and 98: Stack Corruptions • SEP applicati
Page 99 and 100: Heap Corruptions: malloc() Free Lis
Page 101: No-Execute Protection • SEPOS imp
Page 105 and 106: Attack Surface: Hardware • Memory
Page 107 and 108: End Game: JTAG • Glitch the fuse
Page 109 and 110: Conclusion • SEP(OS) was designed
Page 111 and 112: Thanks! • Questions?
Page 113 and 114: SEPOS: System Methods Class Id Meth
Page 115 and 116: SEPOS: Object Methods (2/2) Class I
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