Breaking iOS Code Signing - Reverse Engineering Mac OS X

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Code signing and iOS securityFriday, October 14, 11
iOS Security ModelAll code (binaries and libraries)must be signed by a trusted partyBy default this is AppleDevices can be provisioned toallow additional keys forDevelopment or EnterprisepurposesFriday, October 14, 11
Page 3: AgendaCode signing and iOS security
Page 7 and 8: Malware preventionSince only signed
Page 9 and 10: Exploit mitigationNo pages are writ
Page 11 and 12: ComparisonIn OS XCan allocate RWX p
Page 13 and 14: Overview of internalsMandatory Acce
Page 15 and 16: iOS MAC policiesOnly 2 policies reg
Page 17 and 18: AMFI hooksAMFI uses the following M
Page 19 and 20: mac_vnode_check_execintmac_vnode_ch
Page 21 and 22: mpo_vnode_check_signatureSets CS_HA
Page 23 and 24: Kernel checksparse_machfile(struct
Page 25 and 26: Actual signature validationintubc_c
Page 27 and 28: Code signing so farWhen binary is l
Page 29 and 30: Enforcement codevm_fault_enter{.../
Page 31 and 32: Validating code matches hashvm_page
Page 33 and 34: When a page is invalidBack in vm_fa
Page 35 and 36: No new codeWe’ve seen how all exe
Page 37 and 38: Existing regionsvm_map_protect(...)
Page 39 and 40: Dynamic codesigningIn order to util
Page 41 and 42: Speed vs securityThere is a (single
Page 43 and 44: MobileSafari# ldid -e /Applications
Page 45 and 46: Inside mmapintmmap(proc_t p, struct
Page 47 and 48: Even further......if (flags & MAP_J
Page 49 and 50: Now we pass the checkvm_map_enter(.
Page 51 and 52: vm_map_enter (again)if ((flags & VM
Page 53 and 54: 7 PatchesCan be found at https://gi
Page 55 and 56:
vm_map_enter (again!)vm_map_enter(.
Page 57 and 58:
vm_map_protectvm_map_protect(...){.
Page 59 and 60:
vm_map_protectvm_map_protect(...){.
Page 61 and 62:
Allow “unvalidated” pagesSet cs
Page 63 and 64:
MobileSafari shellcodeunsigned int
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Unsigned code, iOS 2void (*f)();uns
Page 67 and 68:
Questions?Thanks for coming!Friday,
Page 69 and 70:
An iOS 5.0 code signing bugintmmap(
Page 71 and 72:
An iOS 5.0 code signing bug#define
Page 73 and 74:
Allocating RWX regionsAny process w
Page 75 and 76:
Running unsigned codeMalicious App
Page 77 and 78:
Copy and fixup dyldint fd = open("f
Page 79 and 80:
Patch 2uintptr_t ImageLoaderMachO::
Page 81 and 82:
Patch 2uintptr_t ImageLoaderMachO::
Page 83 and 84:
Patch 3void ImageLoaderMachO::mapSe
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Patch 3void ImageLoaderMachO::mapSe
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Patch 4void ImageLoader::link(const
Page 89 and 90:
Apple review processAn app that did
Page 91 and 92:
InstastockAlso rejected - for illeg
Page 93 and 94:
App Store Review ProcessNot very cl
Page 95:
Questions?Contact me at charlie.mil
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