Extend further validation of config values (#8469)

- This PR allows config KVS to be validated properly
  without being affected by ENV overrides, rejects
  invalid values during set operation

- Expands unit tests and refactors the error handling
  for notification targets, returns error instead of
  ignoring targets for invalid KVS

- Does all the prep-work for implementing safe-mode
  style operation for MinIO server, introduces a new
  global variable to toggle safe mode based operations
  NOTE: this PR itself doesn't provide safe mode operations

cmd/config/compress/compress.go

@@ -56,11 +56,15 @@ var (
 )
 
 // Parses the given compression exclude list `extensions` or `content-types`.
-func parseCompressIncludes(includes []string) ([]string, error) {
+func parseCompressIncludes(include string) ([]string, error) {
+	includes := strings.Split(include, config.ValueSeparator)
 	for _, e := range includes {
 		if len(e) == 0 {
 			return nil, config.ErrInvalidCompressionIncludesValue(nil).Msg("extension/mime-type cannot be empty")
 		}
+		if e == "/" {
+			return nil, config.ErrInvalidCompressionIncludesValue(nil).Msg("extension/mime-type cannot be '/'")
+		}
 	}
 	return includes, nil
 }
@@ -90,22 +94,21 @@ func LookupConfig(kvs config.KVS) (Config, error) {
 	compressMimeTypesLegacy := env.Get(EnvCompressMimeTypesLegacy, kvs.Get(MimeTypes))
 	if compressExtensions != "" || compressMimeTypes != "" || compressMimeTypesLegacy != "" {
 		if compressExtensions != "" {
-			extensions, err := parseCompressIncludes(strings.Split(compressExtensions, config.ValueSeparator))
+			extensions, err := parseCompressIncludes(compressExtensions)
 			if err != nil {
 				return cfg, fmt.Errorf("%s: Invalid MINIO_COMPRESS_EXTENSIONS value (`%s`)", err, extensions)
 			}
 			cfg.Extensions = extensions
 		}
 		if compressMimeTypes != "" {
-			mimeTypes, err := parseCompressIncludes(strings.Split(compressMimeTypes, config.ValueSeparator))
+			mimeTypes, err := parseCompressIncludes(compressMimeTypes)
 			if err != nil {
 				return cfg, fmt.Errorf("%s: Invalid MINIO_COMPRESS_MIME_TYPES value (`%s`)", err, mimeTypes)
 			}
 			cfg.MimeTypes = mimeTypes
 		}
 		if compressMimeTypesLegacy != "" {
-			mimeTypes, err := parseCompressIncludes(strings.Split(compressMimeTypesLegacy,
-				config.ValueSeparator))
+			mimeTypes, err := parseCompressIncludes(compressMimeTypesLegacy)
 			if err != nil {
 				return cfg, fmt.Errorf("%s: Invalid MINIO_COMPRESS_MIME_TYPES value (`%s`)", err, mimeTypes)
 			}

cmd/config/compress/compress_test.go

@@ -0,0 +1,57 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 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 compress
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestParseCompressIncludes(t *testing.T) {
+	testCases := []struct {
+		str              string
+		expectedPatterns []string
+		success          bool
+	}{
+		// invalid input
+		{",,,", []string{}, false},
+		{"", []string{}, false},
+		{",", []string{}, false},
+		{"/", []string{}, false},
+		{"text/*,/", []string{}, false},
+
+		// valid input
+		{".txt,.log", []string{".txt", ".log"}, true},
+		{"text/*,application/json", []string{"text/*", "application/json"}, true},
+	}
+
+	for _, testCase := range testCases {
+		testCase := testCase
+		t.Run(testCase.str, func(t *testing.T) {
+			gotPatterns, err := parseCompressIncludes(testCase.str)
+			if !testCase.success && err == nil {
+				t.Error("expected failure but success instead")
+			}
+			if testCase.success && err != nil {
+				t.Errorf("expected success but failed instead %s", err)
+			}
+			if testCase.success && !reflect.DeepEqual(testCase.expectedPatterns, gotPatterns) {
+				t.Errorf("expected patterns %s but got %s", testCase.expectedPatterns, gotPatterns)
+			}
+		})
+	}
+}