internal/ethapi: quantity-encode storage keys in eth_getProof response (#27309)

This changes the eth_getProof method implementation to re-encode the requested
storage keys, canonicalizing them in the response. For backwards-compatibility reasons,
go-ethereum accepts non-canonical hex keys. Accepting them is fine, but we should
not mirror invalid inputs into the output.

Closes #27306

---------
Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Felix Lange <fjl@twurst.com>

ethclient/gethclient/gethclient_test.go

@@ -105,6 +105,9 @@ func TestGethClient(t *testing.T) {
 		{
 			"TestGetProof",
 			func(t *testing.T) { testGetProof(t, client) },
+		}, {
+			"TestGetProofCanonicalizeKeys",
+			func(t *testing.T) { testGetProofCanonicalizeKeys(t, client) },
 		}, {
 			"TestGCStats",
 			func(t *testing.T) { testGCStats(t, client) },
@@ -218,6 +221,7 @@ func testGetProof(t *testing.T, client *rpc.Client) {
 	if result.Balance.Cmp(balance) != 0 {
 		t.Fatalf("invalid balance, want: %v got: %v", balance, result.Balance)
 	}
+
 	// test storage
 	if len(result.StorageProof) != 1 {
 		t.Fatalf("invalid storage proof, want 1 proof, got %v proof(s)", len(result.StorageProof))
@@ -228,7 +232,37 @@ func testGetProof(t *testing.T, client *rpc.Client) {
 		t.Fatalf("invalid storage proof value, want: %v, got: %v", slotValue, proof.Value.Bytes())
 	}
 	if proof.Key != testSlot.String() {
-		t.Fatalf("invalid storage proof key, want: %v, got: %v", testSlot.String(), proof.Key)
+		t.Fatalf("invalid storage proof key, want: %q, got: %q", testSlot.String(), proof.Key)
+	}
+}
+
+func testGetProofCanonicalizeKeys(t *testing.T, client *rpc.Client) {
+	ec := New(client)
+
+	// Tests with non-canon input for storage keys.
+	// Here we check that the storage key is canonicalized.
+	result, err := ec.GetProof(context.Background(), testAddr, []string{"0x0dEadbeef"}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result.StorageProof[0].Key != "0xdeadbeef" {
+		t.Fatalf("wrong storage key encoding in proof: %q", result.StorageProof[0].Key)
+	}
+	if result, err = ec.GetProof(context.Background(), testAddr, []string{"0x000deadbeef"}, nil); err != nil {
+		t.Fatal(err)
+	}
+	if result.StorageProof[0].Key != "0xdeadbeef" {
+		t.Fatalf("wrong storage key encoding in proof: %q", result.StorageProof[0].Key)
+	}
+
+	// If the requested storage key is 32 bytes long, it will be returned as is.
+	hashSizedKey := "0x00000000000000000000000000000000000000000000000000000000deadbeef"
+	result, err = ec.GetProof(context.Background(), testAddr, []string{hashSizedKey}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if result.StorageProof[0].Key != hashSizedKey {
+		t.Fatalf("wrong storage key encoding in proof: %q", result.StorageProof[0].Key)
 	}
 }
 

internal/ethapi/api.go

@@ -672,19 +672,21 @@ func (n *proofList) Delete(key []byte) error {
 func (s *BlockChainAPI) GetProof(ctx context.Context, address common.Address, storageKeys []string, blockNrOrHash rpc.BlockNumberOrHash) (*AccountResult, error) {
 	var (
 		keys         = make([]common.Hash, len(storageKeys))
+		keyLengths   = make([]int, len(storageKeys))
 		storageProof = make([]StorageResult, len(storageKeys))
 		storageTrie  state.Trie
 		storageHash  = types.EmptyRootHash
 		codeHash     = types.EmptyCodeHash
 	)
-	// Greedily deserialize all keys. This prevents state access on invalid input
+	// Deserialize all keys. This prevents state access on invalid input.
 	for i, hexKey := range storageKeys {
-		if key, err := decodeHash(hexKey); err != nil {
+		var err error
+		keys[i], keyLengths[i], err = decodeHash(hexKey)
+		if err != nil {
 			return nil, err
-		} else {
-			keys[i] = key
 		}
 	}
+
 	state, _, err := s.b.StateAndHeaderByNumberOrHash(ctx, blockNrOrHash)
 	if state == nil || err != nil {
 		return nil, err
@@ -692,28 +694,39 @@ func (s *BlockChainAPI) GetProof(ctx context.Context, address common.Address, st
 	if storageTrie, err = state.StorageTrie(address); err != nil {
 		return nil, err
 	}
-	// if we have a storageTrie, the account exists and we must update
+
+	// If we have a storageTrie, the account exists and we must update
 	// the storage root hash and the code hash.
 	if storageTrie != nil {
 		storageHash = storageTrie.Hash()
 		codeHash = state.GetCodeHash(address)
 	}
-	// create the proof for the storageKeys
+	// Create the proofs for the storageKeys.
 	for i, key := range keys {
+		// Output key encoding is a bit special: if the input was a 32-byte hash, it is
+		// returned as such. Otherwise, we apply the QUANTITY encoding mandated by the
+		// JSON-RPC spec for getProof. This behavior exists to preserve backwards
+		// compatibility with older client versions.
+		var outputKey string
+		if keyLengths[i] != 32 {
+			outputKey = hexutil.EncodeBig(key.Big())
+		} else {
+			outputKey = hexutil.Encode(key[:])
+		}
+
 		if storageTrie == nil {
-			storageProof[i] = StorageResult{storageKeys[i], &hexutil.Big{}, []string{}}
+			storageProof[i] = StorageResult{outputKey, &hexutil.Big{}, []string{}}
 			continue
 		}
 		var proof proofList
 		if err := storageTrie.Prove(crypto.Keccak256(key.Bytes()), &proof); err != nil {
 			return nil, err
 		}
-		storageProof[i] = StorageResult{storageKeys[i],
-			(*hexutil.Big)(state.GetState(address, key).Big()),
-			proof}
+		value := (*hexutil.Big)(state.GetState(address, key).Big())
+		storageProof[i] = StorageResult{outputKey, value, proof}
 	}
 
-	// create the accountProof
+	// Create the accountProof.
 	accountProof, proofErr := state.GetProof(address)
 	if proofErr != nil {
 		return nil, proofErr
@@ -732,7 +745,7 @@ func (s *BlockChainAPI) GetProof(ctx context.Context, address common.Address, st
 
 // 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) (common.Hash, error) {
+func decodeHash(s string) (h common.Hash, inputLength int, err error) {
 	if strings.HasPrefix(s, "0x") || strings.HasPrefix(s, "0X") {
 		s = s[2:]
 	}
@@ -741,12 +754,12 @@ func decodeHash(s string) (common.Hash, error) {
 	}
 	b, err := hex.DecodeString(s)
 	if err != nil {
-		return common.Hash{}, errors.New("hex string invalid")
+		return common.Hash{}, 0, errors.New("hex string invalid")
 	}
 	if len(b) > 32 {
-		return common.Hash{}, errors.New("hex string too long, want at most 32 bytes")
+		return common.Hash{}, len(b), errors.New("hex string too long, want at most 32 bytes")
 	}
-	return common.BytesToHash(b), nil
+	return common.BytesToHash(b), len(b), nil
 }
 
 // GetHeaderByNumber returns the requested canonical block header.
@@ -876,7 +889,7 @@ func (s *BlockChainAPI) GetStorageAt(ctx context.Context, address common.Address
 	if state == nil || err != nil {
 		return nil, err
 	}
-	key, err := decodeHash(hexKey)
+	key, _, err := decodeHash(hexKey)
 	if err != nil {
 		return nil, fmt.Errorf("unable to decode storage key: %s", err)
 	}