Enhance policy handling to support SSE and WORM (#5790)

- remove old bucket policy handling
- add new policy handling
- add new policy handling unit tests

This patch brings support to bucket policy to have more control not
limiting to anonymous.  Bucket owner controls to allow/deny any rest
API.

For example server side encryption can be controlled by allowing
PUT/GET objects with encryptions including bucket owner.

pkg/policy/effect_test.go

@@ -0,0 +1,122 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package policy
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+func TestEffectIsAllowed(t *testing.T) {
+	testCases := []struct {
+		effect         Effect
+		check          bool
+		expectedResult bool
+	}{
+		{Allow, false, false},
+		{Allow, true, true},
+		{Deny, false, true},
+		{Deny, true, false},
+	}
+
+	for i, testCase := range testCases {
+		result := testCase.effect.IsAllowed(testCase.check)
+
+		if result != testCase.expectedResult {
+			t.Fatalf("case %v: expected: %v, got: %v\n", i+1, testCase.expectedResult, result)
+		}
+	}
+
+}
+
+func TestEffectIsValid(t *testing.T) {
+	testCases := []struct {
+		effect         Effect
+		expectedResult bool
+	}{
+		{Allow, true},
+		{Deny, true},
+		{Effect(""), false},
+		{Effect("foo"), false},
+	}
+
+	for i, testCase := range testCases {
+		result := testCase.effect.IsValid()
+
+		if result != testCase.expectedResult {
+			t.Fatalf("case %v: expected: %v, got: %v\n", i+1, testCase.expectedResult, result)
+		}
+	}
+}
+
+func TestEffectMarshalJSON(t *testing.T) {
+	testCases := []struct {
+		effect         Effect
+		expectedResult []byte
+		expectErr      bool
+	}{
+		{Allow, []byte(`"Allow"`), false},
+		{Deny, []byte(`"Deny"`), false},
+		{Effect(""), nil, true},
+		{Effect("foo"), nil, true},
+	}
+
+	for i, testCase := range testCases {
+		result, err := json.Marshal(testCase.effect)
+		expectErr := (err != nil)
+
+		if expectErr != testCase.expectErr {
+			t.Fatalf("case %v: error: expected: %v, got: %v\n", i+1, testCase.expectErr, expectErr)
+		}
+
+		if !testCase.expectErr {
+			if !reflect.DeepEqual(result, testCase.expectedResult) {
+				t.Fatalf("case %v: result: expected: %v, got: %v\n", i+1, string(testCase.expectedResult), string(result))
+			}
+		}
+	}
+}
+
+func TestEffectUnmarshalJSON(t *testing.T) {
+	testCases := []struct {
+		data           []byte
+		expectedResult Effect
+		expectErr      bool
+	}{
+		{[]byte(`"Allow"`), Allow, false},
+		{[]byte(`"Deny"`), Deny, false},
+		{[]byte(`""`), Effect(""), true},
+		{[]byte(`"foo"`), Effect(""), true},
+	}
+
+	for i, testCase := range testCases {
+		var result Effect
+		err := json.Unmarshal(testCase.data, &result)
+		expectErr := (err != nil)
+
+		if expectErr != testCase.expectErr {
+			t.Fatalf("case %v: error: expected: %v, got: %v\n", i+1, testCase.expectErr, expectErr)
+		}
+
+		if !testCase.expectErr {
+			if result != testCase.expectedResult {
+				t.Fatalf("case %v: result: expected: %v, got: %v\n", i+1, testCase.expectedResult, result)
+			}
+		}
+	}
+}