Demystifying the Secure Enclave Processor

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SEP Memory Protection Bootstrap • Ping acknowledgement of BootTZ0 • Exit out of initial message loop. • Checks whether TZ0 and TZ1 have been locked by reading the registers at 0x2_0000_09xx (shared between SEP and AP). ▫ If not, spin. • Map TZ0 region to physical address 0x8000_0000. Page tables in ROM already mapped that PA to VA 0x1018_0000. Stage 2 Stage 3 Acknowledge Ping Acknowledge BootTZ0 Map in TZ0 Setup Memory Encryption Begin Stage 3 Configure TZ0 and TZ1 Send Ping Send BootTZ0 Send Ping iBoot Kernel
Memory Encryption Setup • Use “True Random Number Generator” to generate 192 bits of randomness and store it in the TZ0 area (not encrypted yet). • Use a standard key generation format (used for generating ART for example) to generate final encryption key: ▫ [4 byte magic = 0xFF XK1][4 bytes of 0s][192-bits of randomness] • Copy key from AES result registers through SEP registers directly into encryption controller registers (without touching memory).
Page 1 and 2: Demystifying the Secure Enclave Pro
Page 3 and 4: Introduction • iPhone 5S was a te
Page 5 and 6: Secure (?) Enclave Processor • Ve
Page 7 and 8: Glossary • AP: Application Proces
Page 11 and 12: Dedicated Hardware Peripherals •
Page 13 and 14: Physical Memory • Dedicated BootR
Page 17 and 18: SEP Initialization - Page Tables
Page 19 and 20: SEP Initialization - Second Stage
Page 21: SEP Boot Flow SEP AP Configure TZ0
Page 25 and 26: • Mode actually used is AES-256-X
Page 27 and 28: SEP Boot Flow: Stage 3 SEP AP Ackno
Page 29 and 30: Sending SEPOS • SEPOS is sent (op
Page 31 and 32: Boot-loading: Img4 • SEP uses the
Page 33 and 34: Img4 - Manifest • The manifest (A
Page 35 and 36: IMG4 - Manifest Properties (2/2) He
Page 37 and 38: Reversing SEP’s Img4 Parser: Stag
Page 39 and 40: Img4 Parsing Flow SEP AP Decode Pay
Page 43 and 44: Secure Mailbox • Actual mailbox i
Page 45 and 46: Interrupt-based Message Passing •
Page 47 and 48: Mailbox Message Format • A single
Page 49 and 50: 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 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
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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
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Heap Corruptions: malloc() Free Lis
Page 101 and 102:
No-Execute Protection • SEPOS imp
Page 103 and 104:
Attack Surface: BootROM • Effecti
Page 105 and 106:
Attack Surface: Hardware • Memory
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End Game: JTAG • Glitch the fuse
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Conclusion • SEP(OS) was designed
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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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Demystifying the Secure Enclave Processor

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