internal/ethapi: return error when requesting invalid trie key (#25762)

This change makes eth_getProof and eth_getStorageAt return an error when
the argument contains invalid hex in storage keys.

Co-authored-by: Felix Lange <fjl@twurst.com>

internal/ethapi/api.go

@@ -18,6 +18,7 @@ package ethapi
 
 import (
 	"context"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"math/big"
@@ -674,15 +675,19 @@ func (s *BlockChainAPI) GetProof(ctx context.Context, address common.Address, st
 	}
 
 	// create the proof for the storageKeys
-	for i, key := range storageKeys {
+	for i, hexKey := range storageKeys {
+		key, err := decodeHash(hexKey)
+		if err != nil {
+			return nil, err
+		}
 		if storageTrie != nil {
-			proof, storageError := state.GetStorageProof(address, common.HexToHash(key))
+			proof, storageError := state.GetStorageProof(address, key)
 			if storageError != nil {
 				return nil, storageError
 			}
-			storageProof[i] = StorageResult{key, (*hexutil.Big)(state.GetState(address, common.HexToHash(key)).Big()), toHexSlice(proof)}
+			storageProof[i] = StorageResult{hexKey, (*hexutil.Big)(state.GetState(address, key).Big()), toHexSlice(proof)}
 		} else {
-			storageProof[i] = StorageResult{key, &hexutil.Big{}, []string{}}
+			storageProof[i] = StorageResult{hexKey, &hexutil.Big{}, []string{}}
 		}
 	}
 
@@ -703,6 +708,22 @@ func (s *BlockChainAPI) GetProof(ctx context.Context, address common.Address, st
 	}, state.Error()
 }
 
+// decodeHash parses a hex-encoded 32-byte hash. The input may optionally
+// be prefixed by 0x and can have an byte length up to 32.
+func decodeHash(s string) (common.Hash, error) {
+	if strings.HasPrefix(s, "0x") || strings.HasPrefix(s, "0X") {
+		s = s[2:]
+	}
+	b, err := hex.DecodeString(s)
+	if err != nil {
+		return common.Hash{}, fmt.Errorf("hex string invalid")
+	}
+	if len(b) > 32 {
+		return common.Hash{}, fmt.Errorf("hex string too long, want at most 32 bytes")
+	}
+	return common.BytesToHash(b), nil
+}
+
 // GetHeaderByNumber returns the requested canonical block header.
 // * When blockNr is -1 the chain head is returned.
 // * When blockNr is -2 the pending chain head is returned.
@@ -821,12 +842,16 @@ func (s *BlockChainAPI) GetCode(ctx context.Context, address common.Address, blo
 // GetStorageAt returns the storage from the state at the given address, key and
 // block number. The rpc.LatestBlockNumber and rpc.PendingBlockNumber meta block
 // numbers are also allowed.
-func (s *BlockChainAPI) GetStorageAt(ctx context.Context, address common.Address, key string, blockNrOrHash rpc.BlockNumberOrHash) (hexutil.Bytes, error) {
+func (s *BlockChainAPI) GetStorageAt(ctx context.Context, address common.Address, hexKey string, blockNrOrHash rpc.BlockNumberOrHash) (hexutil.Bytes, error) {
 	state, _, err := s.b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
 	if state == nil || err != nil {
 		return nil, err
 	}
-	res := state.GetState(address, common.HexToHash(key))
+	key, err := decodeHash(hexKey)
+	if err != nil {
+		return nil, fmt.Errorf("unable to decode storage key: %s", err)
+	}
+	res := state.GetState(address, key)
 	return res[:], state.Error()
 }