Trivial authentication bypass in libssh leaves servers wide open

Re:Trivial authentication bypass in libssh leaves servers wi... by lozenge on Thursday October 18, 2018 @03:24AM (#18246567)

How could you do 10x better? Because it's a broad design flaw there is no suspicious LOC or suspiciously overcomplicated code needed to hide the backdoor. You have to understand the whole context to notice the bug.

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Re:Trivial authentication bypass in libssh leaves servers wi... by wepple on Thursday October 18, 2018 @08:18AM (#18247629)

But it’s still there in plain sight. I’d hazard a guess that this may be the first time a solid code reviewer looked at the code, and spotted it straight away*

If you wanted 10x better, you could throw in some code that exhibits undefined (but known on major compilers) behavior, or super subtle C issues. Even a simple if statement in C forces all kinds of wonderful promotions and type conversions which can truncate, wrap, and drastically change values in ways that even most C developers aren’t aware.

I encourage folks to go check out the “underhanded C contest” before suggesting that this bug is a backdoor.

*The person who found this, Peter, is indeed insanely good.

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Re:Trivial authentication bypass in libssh leaves servers wi... by lrvick on Thursday October 18, 2018 @12:49PM (#18249894)

Make sure the PRNG does not source enough entropy thus dramatically weakening all session keys to a crackable level.

Or do like WEP and recycle your one time pads. Lots of subtle design flaws one can introduce that generally get spotted in blackbox testing, and not in code.

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Re:Trivial authentication bypass in libssh leaves servers wi... by foota on Thursday October 18, 2018 @03:49AM (#18246670)

I mean, a backdoor can just be flipping an if somewhere from && to ||, not exactly suspicious if it's mixed in with other stuff.

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