vyper performs incorrect topic logging in raw_log

Summary

Incorrect values can be logged when raw_log builtin is called with memory or storage arguments to be used as topics.

A contract search was performed and no vulnerable contracts were found in production. In particular, no uses of raw_log() were found at all in production; it is apparently not a well-known function.

Details

The build_IR function of the RawLog class fails to properly unwrap the variables provided as topics. Consequently, incorrect values are logged as topics.

PoC

x: bytes32

@external
def f():
    self.x = 0x1234567890123456789012345678901234567890123456789012345678901234
    raw_log([self.x], b"") # LOG1(offset:0x60, size:0x00, topic1:0x00)

    y: bytes32 = 0x1234567890123456789012345678901234567890123456789012345678901234
    raw_log([y], b"") # LOG1(offset:0x80, size:0x00, topic1:0x40)

Patches

Fixed in https://github.com/vyperlang/vyper/pull/3977.

Impact

Incorrect values can be logged which may result in unexpected behavior in client-side applications relying on these logs.