> In Mach-O binaries, functions whose pointers are in the __mod_init_funcs run before main.
Remember that obfuscation makes your code run slower. This specific one is part of the reason why the dyld team probably hates you.
Reverse Engineering Snapchat: Obfuscation Techniques
61–70 of 180 posts
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#62Earlier quoted context omitted.
Certificate pinning spoils that, no spoofing of certs with pinning. Cert (or hash of) delivered with app. If server cert doesn't match expected value coded into app, someone is messing with something, terminate connection.
Yes that complicates things. But if you can find the cert in the binary's data section, maybe you can patch it with your own.
Assuming this is for Android, the APK would no longer be signed and would cause all login attempts to fail.
Have a read about "SafetyNet Attestion API" for Android.
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#63This sort of thing has been prevalent in the game world for decades.
I once had the chance to work on a project disassembling casino machines, and they had similar protection appropriate for the technology of the time
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#64Earlier quoted context omitted.
Yes that complicates things. But if you can find the cert in the binary's data section, maybe you can patch it with your own.
Assuming this is for Android, the APK would no longer be signed and would cause all login attempts to fail. Have a read about "SafetyNet Attestion API" for Android.
You could patch Android and run it in an emulator. Or patch Snap not to care. Not super familiar, but there should be a way. Client side security can only do so much.
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#65Will Apple approve an app with this level of Obfuscation in it's source? I thought they had to have the source itself?
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#66This is an awesome write-up; I’m shocked at the level of effort that went into Snap’s obfuscation process. It implies that are entire teams of engineers out there whose sole job it is to play cat&mouse with reverse engineers and nothing more. Another comment mentioned that this effort is outsourced, so not only are there teams, but entire companies dedicated to this! What a blast that must be... though the immense am…
> though the immense amount of [invested|wasted] (take your pick depending on cynicism) effort spent on this game makes me a little sad
that's an odd position to take. You seem to be ignoring the philosophy behind the cat&mouse game that is RE (and Security Engineering in general). What you call cosplaying Sisyphus is to me one of the most rewarding aspects of Tech. Breaking things especially is fun when somebody has made an effort to lock things down (and maybe even claimed it's "unhackable"). This is an area where you're still paid to solve puzzles and where taking the long-view matters. RE is complex and hard but exactly because of this it's one of the most rewarding things in all of CompSci.
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#67Will Apple approve an app with this level of Obfuscation in it's source? I thought they had to have the source itself?
Apple don't need the source of your app, but some bytecode that they can optimize for target platform. As for making sure that certain app not using private frameworks they can just do it through the testing.
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#68Will Apple approve an app with this level of Obfuscation in it's source? I thought they had to have the source itself?
No, they don't. You can provide them with symbol files for your application so they can symbolicate crashes on your behalf, but this isn't required. (Interestingly, there are teams at Apple that reverse engineer applications for compatibility reasons, and the occasional "someone got an obfuscated binary past app review and we need to know what it does".)
Re: Reverse Engineering Snapchat: Obfuscation Techniques
#69Will Apple approve an app with this level of Obfuscation in it's source? I thought they had to have the source itself?
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Re: Reverse Engineering Snapchat: Obfuscation Techniques
#70Will Apple approve an app with this level of Obfuscation in it's source? I thought they had to have the source itself?
Apple don't need the source of your app, but some bytecode that they can optimize for target platform. As for making sure that certain app not using private frameworks they can just do it through the testing.
Bytecode is not required for applications targeting iOS. And I will note that the latter is fairly difficult to actually check in principle, and it's mainly enforced (actually, in certain cases it's not ;) ) in practice by the threat of consequences if they catch you doing it rather than testing.