avoid potential secret leaking while reading .dockercfg

There are a lot of scenarios where an invalid .dockercfg file
will still contain secrets. This commit removes logging of the
contents to avoid any potential leaking and manages the actual error
by printing to the user the actual location of the invalid file.

Signed-off-by: Nikolaos Moraitis <nmoraiti@redhat.com>

pkg/credentialprovider/config_test.go

@@ -309,3 +309,96 @@ func TestDockerConfigEntryJSONCompatibleEncode(t *testing.T) {
 		}
 	}
 }
+
+func TestReadDockerConfigFileFromBytes(t *testing.T) {
+	testCases := []struct {
+		id               string
+		input            []byte
+		expectedCfg      DockerConfig
+		errorExpected    bool
+		expectedErrorMsg string
+	}{
+		{
+			id:    "valid input, no error expected",
+			input: []byte(`{"http://foo.example.com":{"username": "foo", "password": "bar", "email": "foo@example.com"}}`),
+			expectedCfg: DockerConfig(map[string]DockerConfigEntry{
+				"http://foo.example.com": {
+					Username: "foo",
+					Password: "bar",
+					Email:    "foo@example.com",
+				},
+			}),
+		},
+		{
+			id:               "invalid input, error expected",
+			input:            []byte(`{"http://foo.example.com":{"username": "foo", "password": "bar", "email": "foo@example.com"`),
+			errorExpected:    true,
+			expectedErrorMsg: "error occurred while trying to unmarshal json",
+		},
+	}
+
+	for _, tc := range testCases {
+		cfg, err := readDockerConfigFileFromBytes(tc.input)
+		if err != nil && !tc.errorExpected {
+			t.Fatalf("Error was not expected: %v", err)
+		}
+		if err != nil && tc.errorExpected {
+			if !reflect.DeepEqual(err.Error(), tc.expectedErrorMsg) {
+				t.Fatalf("Expected error message: `%s` got `%s`", tc.expectedErrorMsg, err.Error())
+			}
+		} else {
+			if !reflect.DeepEqual(cfg, tc.expectedCfg) {
+				t.Fatalf("expected: %v got %v", tc.expectedCfg, cfg)
+			}
+		}
+	}
+}
+
+func TestReadDockerConfigJSONFileFromBytes(t *testing.T) {
+	testCases := []struct {
+		id               string
+		input            []byte
+		expectedCfg      DockerConfig
+		errorExpected    bool
+		expectedErrorMsg string
+	}{
+		{
+			id:    "valid input, no error expected",
+			input: []byte(`{"auths": {"http://foo.example.com":{"username": "foo", "password": "bar", "email": "foo@example.com"}, "http://bar.example.com":{"username": "bar", "password": "baz", "email": "bar@example.com"}}}`),
+			expectedCfg: DockerConfig(map[string]DockerConfigEntry{
+				"http://foo.example.com": {
+					Username: "foo",
+					Password: "bar",
+					Email:    "foo@example.com",
+				},
+				"http://bar.example.com": {
+					Username: "bar",
+					Password: "baz",
+					Email:    "bar@example.com",
+				},
+			}),
+		},
+		{
+			id:               "invalid input, error expected",
+			input:            []byte(`{"auths": {"http://foo.example.com":{"username": "foo", "password": "bar", "email": "foo@example.com"}, "http://bar.example.com":{"username": "bar", "password": "baz", "email": "bar@example.com"`),
+			errorExpected:    true,
+			expectedErrorMsg: "error occurred while trying to unmarshal json",
+		},
+	}
+
+	for _, tc := range testCases {
+		cfg, err := readDockerConfigJSONFileFromBytes(tc.input)
+		if err != nil && !tc.errorExpected {
+			t.Fatalf("Error was not expected: %v", err)
+		}
+		if err != nil && tc.errorExpected {
+			if !reflect.DeepEqual(err.Error(), tc.expectedErrorMsg) {
+				t.Fatalf("Expected error message: `%s` got `%s`", tc.expectedErrorMsg, err.Error())
+			}
+		} else {
+			if !reflect.DeepEqual(cfg, tc.expectedCfg) {
+				t.Fatalf("expected: %v got %v", tc.expectedCfg, cfg)
+			}
+		}
+	}
+}