Randar: A Minecraft exploit that uses LLL lattice reduction to crack server RNG

• randar-explanation

  2 569 8.6 Shell

  "Randar" is an exploit for Minecraft which uses LLL lattice reduction to crack the internal state of an incorrectly reused java.util.Random in the Minecraft server, then works backwards from that to locate other players currently loaded into the world.

  

• Roshambo

  1 3 - C

  My dissertation

- It plays randomly for the first 998 turns (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...): this line is "if (*turn < trials - 2) return libra ? callback() : random() % 3;", and "libra" is initalized to (int) NULL, i.e. zero, on every invocation.

- In the last 2 turns, it uses `find_goodkarma` to comb through the stack to find where the variables that match its history and the opponents' history are stored. These the stack arrays p1hist and p2hist (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...)

They're easy to find because they contain 998 known values each in a ~random sequence of (0, 1, 2), and they're just upwards of the stack from the current invocation of the Psychic Friends Network.

`find_goodkarma` simply increments a pointer until the whole sequence of 998 values matches the known history.

- Then, it rewrites the history to make itself win. These lines (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...) never get executed, then these lines (https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...) tally up draws so far (libra), wins (cancer) and losses (scorpio).

This line makes sure its move is the opponents' move +1 mod 3, which is the winning move: https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...

Then, these lines repeat the same trick for the number of wins and losses. It checks whether it's p1 or p2 by comparing the addresses of the win/loss arrays, and then overwrites the wins/losses appropriately using `pizza` https://github.com/MrValdez/Roshambo/blob/master/rsb-iocaine...

in the end it returns an arbitrary value (the address of `good_hand` mod 3).

It was fun to follow but the result is kind of boring :)

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• drand

  7 700 6.0 Go

  🎲 A Distributed Randomness Beacon Daemon - Go implementation

  

Or, if you don't want to trust the source, https://drand.love/

• LattiCG

  1 54 6.7 Java

  Reverses the internal seed(s) of JavaRandom given information on its output in the form of a system of inequalities on various Random calls. Works by reducing the problem to finding certain vectors in a lattice, which is then solved through a branch and bound algorithm using a reduced version of the lattice.

It was a one-way collaboration, in that we referenced their discoveries and code such as LattiCG https://github.com/mjtb49/LattiCG, but they were unaware of anything we were doing until now. https://twitter.com/admiral_stapler/status/17806748612594609...

Naming Baritone after Fit is actually a coincidence / joke, the repo github.com/cabaletta/baritone was the result of random brainstorming for something untaken. We only later realized it described Fit and thus added that to the readme :)

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