ecrecover related bugs are not detected(Support for SWC-122)

[HarryR]

Description

It doesn't detect ecrecover failing upon invalid input

How to Reproduce

See the following piece of code:

https://gist.github.com/HarryR/cce52596ffebdff2744c5d790888015a

This was caused by a compiler bug in Solidity < 0.4.14, where the output memory area for the ecrecover call wasn't cleared, which means in the case of an invalid signature the memory may contain user-controllable input.

If the contract address is passed in as the last 20 bytes of the 32-byte stuff2hash input, then the if condition will be true and the contract will send all funds to the caller.

This was recently highlighted as a problem with the 0x contracts, see: https://samczsun.com/the-0x-vulnerability-explained/

Expected behavior

this bug should be detected

[norhh]

Hi @HarryR . Currently Mythril doesn't yet support SWC-122. We will support it soon.

[HarryR]

SWC-122 is vague and wishy-washy, and could be applicable to many different schemes.

Surely there should be a more-specific SWC, specifically about the semantics of CALL to builtin which can may not overwrite output memory, or other conditions where an output is expected but ends up being user-controlled - where sanitisation is required before the call?

[norhh]

SWC-122 is vague and wishy-washy Yeah SWC-122 is vague. Surely there should be a more-specific SWC, specifically about the semantics of CALL to builtin which can may not overwrite output memory, or other conditions where an output is expected but ends up being user-controlled - where sanitisation is required before the call? You can raise this issue in SWCRegistry if you want to.