Module host 

Host functions overrides for Ethereum address recovery.

The host functions overriding is required because of impersonation feature. Impersonation is used for sending/executing transactions with a signer where its private key is unknown. Sent transactions require a signature that is obtained with sender’s private key and the pallet-revive runtime logic can recover the signer’s ethereum address from the signature and the rest of the transaction bytes. The runtime recovers the signer’s address by running secp256k1_ecdsa_recover to recover the signer’s public key, and keccak_256 to hash the public key to a 20 byes Ethereum address. These functions are exposed by sp-io and used as host functions by the runtime. This module implements tweaked versions of the host functions from sp-io, which can recognize fake signatures used for impersonated transactions, and can recover the signer address from them, while expecting those fake signatures to be built in a certain way ([0; 12] + sender’s Ethereum address + [IMPERSONATION_MARKER; 32] + recovery_id).

The tweaked host functions are especially useful in the context of overriding the same sp-io host functions in the wasm executor type.

Modules

crypto

hashing

Constants

IMPERSONATION_MARKER

Magic marker used to identify impersonated transactions. Using 0xDE for “DEfake” - a distinctive pattern that won’t collide with legitimate EVM data. Previously we used [0; 33] but this collided with Solidity mapping key computations for slot 0 (which also have 32 trailing zero bytes).

Functions

is_impersonated

recover_maybe_impersonated_address

Recover sender address from signed transaction, handling impersonated transactions. For impersonated transactions (fake signatures), extracts the address embedded in the signature. For normal transactions, performs standard ECDSA recovery.

Type Aliases

PublicKeyToHashOverride

Provides host function that override hashing functions in the scope of impersonation.

SenderAddressRecoveryOverride

Provides host function that overrides ETH address recovery from signature in the scope of impersonation.