internal/ethapi: return error code -32602 for invalid storage key (#33282)

This was found because other clients are failing RPC tests generated by
Geth. Nethermind and Besu return the correct error code, -32602, in this
situation.

Author: fjl

internal/ethapi/api.go

@@ -374,9 +374,9 @@ func (api *BlockChainAPI) GetProof(ctx context.Context, address common.Address,
 	// Deserialize all keys. This prevents state access on invalid input.
 	for i, hexKey := range storageKeys {
 		var err error
-		keys[i], keyLengths[i], err = decodeHash(hexKey)
+		keys[i], keyLengths[i], err = decodeStorageKey(hexKey)
 		if err != nil {
-			return nil, err
+			return nil, &invalidParamsError{fmt.Sprintf("%v: %q", err, hexKey)}
 		}
 	}
 	statedb, header, err := api.b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
@@ -441,21 +441,22 @@ func (api *BlockChainAPI) GetProof(ctx context.Context, address common.Address,
 	}, statedb.Error()
 }
 
-// decodeHash parses a hex-encoded 32-byte hash. The input may optionally
-// be prefixed by 0x and can have a byte length up to 32.
-func decodeHash(s string) (h common.Hash, inputLength int, err error) {
+// decodeStorageKey parses a hex-encoded 32-byte hash.
+// For legacy compatibility reasons, we parse these keys leniently,
+// with the 0x prefix being optional.
+func decodeStorageKey(s string) (h common.Hash, inputLength int, err error) {
 	if strings.HasPrefix(s, "0x") || strings.HasPrefix(s, "0X") {
 		s = s[2:]
 	}
 	if (len(s) & 1) > 0 {
 		s = "0" + s
 	}
 	if len(s) > 64 {
-		return common.Hash{}, len(s) / 2, errors.New("hex string too long, want at most 32 bytes")
+		return common.Hash{}, len(s) / 2, errors.New("storage key too long (want at most 32 bytes)")
 	}
 	b, err := hex.DecodeString(s)
 	if err != nil {
-		return common.Hash{}, 0, errors.New("hex string invalid")
+		return common.Hash{}, 0, errors.New("invalid hex in storage key")
 	}
 	return common.BytesToHash(b), len(b), nil
 }
@@ -589,9 +590,9 @@ func (api *BlockChainAPI) GetStorageAt(ctx context.Context, address common.Addre
 	if state == nil || err != nil {
 		return nil, err
 	}
-	key, _, err := decodeHash(hexKey)
+	key, _, err := decodeStorageKey(hexKey)
 	if err != nil {
-		return nil, fmt.Errorf("unable to decode storage key: %s", err)
+		return nil, &invalidParamsError{fmt.Sprintf("%v: %q", err, hexKey)}
 	}
 	res := state.GetState(address, key)
 	return res[:], state.Error()