Adding ASLR to Jailbroken iPhones [PDF] - Antid0te

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Installing on the iPhone • current iOS 4.1 jailbreaks are user - space jailbreaks • only iOS 4.2.1 jailbreak for iPod 2G / iPhone 3G and 3GS (old bootrom) are not user - space • just replacing dyld / dyld_shared_cache not possible due to codesigning • „replacing“ must happen after jailbreak is active Stefan Esser • Adding ASLR to jailbroken iPhones • December 2010 • 56
Analysis of current Jailbreak • /sbin/launchd launched in a way that libgmalloc.dylib is loaded • libgmalloc.dylib is a fake dylib that just replaces stack with payload • stack payload launches a ROP attack • ROP is used for sysctl() • security.mac.proc_enforce=0 • secutiry.mac.vnode_enforce=0 • and executing /usr/lib/pf2 • pf2 is a kernel exploit that patches the kernel and re-executes /sbin/launchd Stefan Esser • Adding ASLR to jailbroken iPhones • December 2010 • 57
Page 1 and 2:
http://www.sektioneins.de Adding AS
Page 3 and 4:
What the talk is NOT about This tal
Page 5 and 6: Part I Introduction Stefan Esser
Page 7 and 8: Jailbroken iPhones and Security •
Page 9 and 10: Codesigning ??? • every binary on
Page 11 and 12: Example Crashdump CrashReporter Key
Page 13 and 14: Part II Dyld Shared Cache and ASLR
Page 15 and 16: Libraries where are thou? • since
Page 17 and 18: dyld_shared_cache Header Stefan Ess
Page 19 and 20: Rebasing the Libraries... • okay
Page 21 and 22: the iPhone SDK to the rescue? (II)
Page 23 and 24: Okay what now ? looking at differen
Page 25 and 26: Obvious Complications • different
Page 27 and 28: Let‘s start diffing • Python im
Page 29 and 30: Analysing the results (I) • Expec
Page 31 and 32: What are the two large unknown valu
Page 33 and 34: Small Values and Pointers • some
Page 35 and 36: iPhone libobjc does not match the s
Page 37 and 38: Analysing the different pointer pro
Page 39 and 40: What needs to be rebased? • image
Page 41 and 42: The Dynamic Linker • iPhone OS /
Page 43 and 44: Relocating the Dynamic Linker (II)
Page 45 and 46: Stack Randomization (I) • stack o
Page 47 and 48: Stack Randomization Test int main()
Page 49 and 50: Baby Steps... • generic solution
Page 51 and 52: Crazy Solution • Crazy Solution
Page 53 and 54: Brute Force Pointer Detection (II)
Page 55: Part IV Installing it on the iPhone
Page 59 and 60: Installing an alternative dyld •
Page 61 and 62: Thank you for listening... DEMO Ste
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Adding ASLR to Jailbroken iPhones [PDF] - Antid0te

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