Resource matching fix to overcome issues with regular expression based match (#1476)

bucket-handlers.go

@@ -54,7 +54,7 @@ func enforceBucketPolicy(action string, bucket string, reqURL *url.URL) (s3Error
 		return ErrAccessDenied
 	}
 
-	// Construct resource in 'arn:aws:s3:::examplebucket' format.
+	// Construct resource in 'arn:aws:s3:::examplebucket/object' format.
 	resource := AWSResourcePrefix + strings.TrimPrefix(reqURL.Path, "/")
 
 	// Get conditions for policy verification.

bucket-policy-handlers.go

@@ -77,15 +77,43 @@ func bucketPolicyActionMatch(action string, statement policyStatement) bool {
 
 // Verify if given resource matches with policy statement.
 func bucketPolicyResourceMatch(resource string, statement policyStatement) bool {
-	for _, presource := range statement.Resources {
-		matched, err := regexp.MatchString(presource, strings.TrimPrefix(resource, "/"))
-		fatalIf(err, "Invalid pattern, please verify the pattern string.", nil)
-		// For any path matches, we return quickly and the let the caller continue.
-		if matched {
+
+	match := func(pattern, subj string) bool {
+		if pattern == "" {
+			return subj == pattern
+		}
+		if pattern == "*" {
 			return true
 		}
+		parts := strings.Split(pattern, "*")
+		if len(parts) == 1 {
+			return subj == pattern
+		}
+		tGlob := strings.HasSuffix(pattern, "*")
+		end := len(parts) - 1
+		if !strings.HasPrefix(subj, parts[0]) {
+			return false
+		}
+		for i := 1; i < end; i++ {
+			if !strings.Contains(subj, parts[i]) {
+				return false
+			}
+			idx := strings.Index(subj, parts[i]) + len(parts[i])
+			subj = subj[idx:]
+		}
+		return tGlob || strings.HasSuffix(subj, parts[end])
 	}
-	return false
+
+	for _, presource := range statement.Resources {
+		// the resource rule for object could contain "*" wild card.
+		// the requested object can be given access based on the already set bucket policy if
+		// the match is successful.
+		// More info: http://docs.aws.amazon.com/AmazonS3/latest/dev/s3-arn-format.html .
+		if matched := match(presource, resource); !matched {
+			return false
+		}
+	}
+	return true
 }
 
 // Verify if given condition matches with policy statement.

bucket-policy-handlers_test.go

@@ -0,0 +1,78 @@
+/*
+ * Minio Cloud Storage, (C) 2015, 2016 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 main
+
+import (
+	"fmt"
+	"testing"
+)
+
+// Tests validate Bucket policy resource matcher.
+func TestBucketPolicyResourceMatch(t *testing.T) {
+
+	// generates\ statement with given resource..
+	generateStatement := func(resource string) policyStatement {
+		statement := policyStatement{}
+		statement.Resources = []string{resource}
+		return statement
+	}
+
+	// generates resource prefix.
+	generateResource := func(bucketName, objectName string) string {
+		return AWSResourcePrefix + bucketName + "/" + objectName
+	}
+
+	testCases := []struct {
+		resourceToMatch       string
+		statement             policyStatement
+		expectedResourceMatch bool
+	}{
+		// Test case 1-4.
+		// Policy with resource ending with bucket/* allows access to all objects inside the given bucket.
+		{generateResource("minio-bucket", ""), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/*")), true},
+		{generateResource("minio-bucket", ""), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/*")), true},
+		{generateResource("minio-bucket", ""), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/*")), true},
+		{generateResource("minio-bucket", ""), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/*")), true},
+		// Test case - 5.
+		// Policy with resource ending with bucket/oo* should not allow access to bucket/output.txt.
+		{generateResource("minio-bucket", "output.txt"), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/oo*")), false},
+		// Test case - 6.
+		// Policy with resource ending with bucket/oo* should allow access to bucket/ootput.txt.
+		{generateResource("minio-bucket", "ootput.txt"), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/oo*")), true},
+		// Test case - 7.
+		// Policy with resource ending with bucket/oo* allows access to all subfolders starting with "oo" inside given bucket.
+		{generateResource("minio-bucket", "oop-bucket/my-file"), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/oo*")), true},
+		// Test case - 8.
+		{generateResource("minio-bucket", "Asia/India/1.pjg"), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/Asia/Japan/*")), false},
+		// Test case - 9.
+		{generateResource("minio-bucket", "Asia/India/1.pjg"), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix, "minio-bucket"+"/Asia/Japan/*")), false},
+		// Test case - 10.
+		// Proves that the name space is flat.
+		{generateResource("minio-bucket", "Africa/Bihar/India/design_info.doc/Bihar"), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix,
+			"minio-bucket"+"/*/India/*/Bihar")), true},
+		// Test case - 11.
+		// Proves that the name space is flat.
+		{generateResource("minio-bucket", "Asia/China/India/States/Bihar/output.txt"), generateStatement(fmt.Sprintf("%s%s", AWSResourcePrefix,
+			"minio-bucket"+"/*/India/*/Bihar/*")), true},
+	}
+	for i, testCase := range testCases {
+		actualResourceMatch := bucketPolicyResourceMatch(testCase.resourceToMatch, testCase.statement)
+		if testCase.expectedResourceMatch != actualResourceMatch {
+			t.Errorf("Test %d: Expected Resource match to be `%v`, but instead found it to be `%v`", i+1, testCase.expectedResourceMatch, actualResourceMatch)
+		}
+	}
+}