crypto: improve error messages in LoadECDSA (#20718)

This improves error messages when the file is too short or too long.
Also rewrite the test for SaveECDSA because LoadECDSA has its own
test now.

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

crypto/crypto_test.go

@@ -139,39 +139,82 @@ func TestNewContractAddress(t *testing.T) {
 	checkAddr(t, common.HexToAddress("c9ddedf451bc62ce88bf9292afb13df35b670699"), caddr2)
 }
 
-func TestLoadECDSAFile(t *testing.T) {
-	keyBytes := common.FromHex(testPrivHex)
-	fileName0 := "test_key0"
-	fileName1 := "test_key1"
-	checkKey := func(k *ecdsa.PrivateKey) {
-		checkAddr(t, PubkeyToAddress(k.PublicKey), common.HexToAddress(testAddrHex))
-		loadedKeyBytes := FromECDSA(k)
-		if !bytes.Equal(loadedKeyBytes, keyBytes) {
-			t.Fatalf("private key mismatch: want: %x have: %x", keyBytes, loadedKeyBytes)
+func TestLoadECDSA(t *testing.T) {
+	tests := []struct {
+		input string
+		err   string
+	}{
+		// good
+		{input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"},
+		{input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\n"},
+		{input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\n\r"},
+		{input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\r\n"},
+		{input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\n\n"},
+		{input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\n\r"},
+		// bad
+		{
+			input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcde",
+			err:   "key file too short, want 64 hex characters",
+		},
+		{
+			input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcde\n",
+			err:   "key file too short, want 64 hex characters",
+		},
+		{
+			input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdeX",
+			err:   "invalid hex character 'X' in private key",
+		},
+		{
+			input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdefX",
+			err:   "invalid character 'X' at end of key file",
+		},
+		{
+			input: "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef\n\n\n",
+			err:   "key file too long, want 64 hex characters",
+		},
+	}
+
+	for _, test := range tests {
+		f, err := ioutil.TempFile("", "loadecdsa_test.*.txt")
+		if err != nil {
+			t.Fatal(err)
+		}
+		filename := f.Name()
+		f.WriteString(test.input)
+		f.Close()
+
+		_, err = LoadECDSA(filename)
+		switch {
+		case err != nil && test.err == "":
+			t.Fatalf("unexpected error for input %q:\n  %v", test.input, err)
+		case err != nil && err.Error() != test.err:
+			t.Fatalf("wrong error for input %q:\n  %v", test.input, err)
+		case err == nil && test.err != "":
+			t.Fatalf("LoadECDSA did not return error for input %q", test.input)
 		}
 	}
+}
 
-	ioutil.WriteFile(fileName0, []byte(testPrivHex), 0600)
-	defer os.Remove(fileName0)
-
-	key0, err := LoadECDSA(fileName0)
+func TestSaveECDSA(t *testing.T) {
+	f, err := ioutil.TempFile("", "saveecdsa_test.*.txt")
 	if err != nil {
 		t.Fatal(err)
 	}
-	checkKey(key0)
+	file := f.Name()
+	f.Close()
+	defer os.Remove(file)
 
-	// again, this time with SaveECDSA instead of manual save:
-	err = SaveECDSA(fileName1, key0)
+	key, _ := HexToECDSA(testPrivHex)
+	if err := SaveECDSA(file, key); err != nil {
+		t.Fatal(err)
+	}
+	loaded, err := LoadECDSA(file)
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer os.Remove(fileName1)
-
-	key1, err := LoadECDSA(fileName1)
-	if err != nil {
-		t.Fatal(err)
+	if !reflect.DeepEqual(key, loaded) {
+		t.Fatal("loaded key not equal to saved key")
 	}
-	checkKey(key1)
 }
 
 func TestValidateSignatureValues(t *testing.T) {