Impact
the ecrecover precompile does not fill the output buffer if the signature does not verify, see https://github.com/ethereum/go-ethereum/blob/b058cf454b3bdc7e770e2b3cec83a0bcb48f55ee/core/vm/contracts.go#L188. however, the ecrecover builtin will still return whatever is at memory location 0.
this means that the if the compiler has been convinced to write to the 0 memory location with specially crafted data (generally, this can happen with a hashmap access or immutable read) just before the ecrecover, a signature check might pass on an invalid signature.
A contract search was performed. Most uses of ecrecover are used for erc2612-style permit implementations, which typically look like:
assert _owner != empty(address)
assert block.timestamp <= _deadline
nonce: uint256 = self.nonces[_owner]
digest: bytes32 = keccak256(
concat(
b"\x19\x01",
self.DOMAIN_SEPARATOR,
keccak256(_abi_encode(PERMIT_TYPEHASH, _owner, _spender, _value, nonce, _deadline))
)
)
assert ecrecover(digest, convert(_v, uint256), convert(_r, uint256), convert(_s, uint256)) == _ownerin this case, the immutable PERMIT_TYPEHASH is loaded into ecrecover's output buffer right before ecrecover(), and so the output of ecrecover() here when the signature is invalid will be the value of PERMIT_TYPEHASH. in this case, since PERMIT_TYPEHASH is not a valid address, it will never compare == to _owner, and so the behaviour is exactly the same as if ecrecover() returned 0 in this case.
in general, a contract could have unexpected behavior (i.e. mistakenly pass this style of signature check) if an immutable representing a real address (ex. OWNER) was read right before the ecrecover operation.
Patches
v0.3.10 (with 019a37ab98ff53f04fecfadf602b6cd5ac748f7f and #3586)
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
References
Are there any links users can visit to find out more?
References
Impact
the ecrecover precompile does not fill the output buffer if the signature does not verify, see https://github.com/ethereum/go-ethereum/blob/b058cf454b3bdc7e770e2b3cec83a0bcb48f55ee/core/vm/contracts.go#L188. however, the ecrecover builtin will still return whatever is at memory location 0.
this means that the if the compiler has been convinced to write to the 0 memory location with specially crafted data (generally, this can happen with a hashmap access or immutable read) just before the ecrecover, a signature check might pass on an invalid signature.
A contract search was performed. Most uses of
ecrecoverare used for erc2612-style permit implementations, which typically look like:in this case, the immutable
PERMIT_TYPEHASHis loaded intoecrecover's output buffer right beforeecrecover(), and so the output ofecrecover()here when the signature is invalid will be the value ofPERMIT_TYPEHASH. in this case, sincePERMIT_TYPEHASHis not a valid address, it will never compare==to_owner, and so the behaviour is exactly the same as ifecrecover()returned 0 in this case.in general, a contract could have unexpected behavior (i.e. mistakenly pass this style of signature check) if an immutable representing a real address (ex.
OWNER) was read right before theecrecoveroperation.Patches
v0.3.10 (with 019a37ab98ff53f04fecfadf602b6cd5ac748f7f and #3586)
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
References
Are there any links users can visit to find out more?
References