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)
 	}
 }