SIWE ExpirationTime check skipped when NotBefore is absent

[oniani1]

In web3GrantEthereum, the expiration time check for SIWE messages is gated on NotBefore != nil:

if parsedMessage.NotBefore != nil && parsedMessage.ExpirationTime != nil && !parsedMessage.ExpirationTime.IsZero() && now.After(*parsedMessage.ExpirationTime) {

Per EIP-4361, not-before and expiration-time are independent optional fields. A SIWE message can specify an expirationTime without a notBefore. When that happens, the entire expiration check is skipped and the expired message is accepted.

The Solana handler checks them independently and doesn't have this issue:

if !parsedMessage.ExpirationTime.IsZero() && now.After(parsedMessage.ExpirationTime) {

The MaximumValidityDuration fallback doesn't help here because it's a broader window based on IssuedAt, not the per-message ExpirationTime. A message that sets a 5-minute expiration would still be accepted for the full MaximumValidityDuration window.

Removing parsedMessage.NotBefore != nil && from the condition fixes it.