api: Handle content-length-range policy properly. (#3297)

content-length-range policy in postPolicy API was
not working properly handle it. The reflection
strategy used has changed in recent version of Go.
Any free form interface{} of any integer is treated
as `float64` this caused a bug where content-length-range
parsing failed to provide any value.

Fixes #3295

cmd/api-errors.go

@@ -629,6 +629,8 @@ func toAPIErrorCode(err error) (apiErr APIErrorCode) {
 		apiErr = ErrContentSHA256Mismatch
 	case ObjectTooLarge:
 		apiErr = ErrEntityTooLarge
+	case ObjectTooSmall:
+		apiErr = ErrEntityTooSmall
 	default:
 		apiErr = ErrInternalError
 	}

cmd/bucket-handlers.go

@@ -470,14 +470,22 @@ func (api objectAPIHandlers) PostPolicyBucketHandler(w http.ResponseWriter, r *h
 		return
 	}
 
-	// Use limitReader to ensure that object size is within expected range.
+	// Use rangeReader to ensure that object size is within expected range.
 	lengthRange := postPolicyForm.Conditions.ContentLengthRange
 	if lengthRange.Valid {
 		// If policy restricted the size of the object.
-		fileBody = limitReader(fileBody, int64(lengthRange.Min), int64(lengthRange.Max))
+		fileBody = &rangeReader{
+			Reader: fileBody,
+			Min:    lengthRange.Min,
+			Max:    lengthRange.Max,
+		}
 	} else {
 		// Default values of min/max size of the object.
-		fileBody = limitReader(fileBody, 0, maxObjectSize)
+		fileBody = &rangeReader{
+			Reader: fileBody,
+			Min:    0,
+			Max:    maxObjectSize,
+		}
 	}
 
 	// Save metadata.

cmd/object-utils.go

@@ -163,27 +163,25 @@ func (d byBucketName) Len() int           { return len(d) }
 func (d byBucketName) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
 func (d byBucketName) Less(i, j int) bool { return d[i].Name < d[j].Name }
 
-// Copied from io.LimitReader()
-// limitReader returns a Reader that reads from r
-// but returns error after n bytes.
-// The underlying implementation is a *LimitedReader.
-type limitedReader struct {
-	R io.Reader // underlying reader
-	M int64     // min bytes remaining
-	N int64     // max bytes remaining
+// rangeReader returns a Reader that reads from r
+// but returns error after Max bytes read as errDataTooLarge.
+// but returns error if reader exits before reading Min bytes
+// errDataTooSmall.
+type rangeReader struct {
+	Reader io.Reader // underlying reader
+	Min    int64     // min bytes remaining
+	Max    int64     // max bytes remaining
 }
 
-func limitReader(r io.Reader, m, n int64) io.Reader { return &limitedReader{r, m, n} }
-
-func (l *limitedReader) Read(p []byte) (n int, err error) {
-	n, err = l.R.Read(p)
-	l.N -= int64(n)
-	l.M -= int64(n)
-	if l.N < 0 {
+func (l *rangeReader) Read(p []byte) (n int, err error) {
+	n, err = l.Reader.Read(p)
+	l.Max -= int64(n)
+	l.Min -= int64(n)
+	if l.Max < 0 {
 		// If more data is available than what is expected we return error.
 		return 0, errDataTooLarge
 	}
-	if err == io.EOF && l.M > 0 {
+	if err == io.EOF && l.Min > 0 {
 		return 0, errDataTooSmall
 	}
 	return

cmd/object-utils_test.go

@@ -116,8 +116,8 @@ func TestIsValidObjectName(t *testing.T) {
 	}
 }
 
-// Tests limitReader
-func TestLimitReader(t *testing.T) {
+// Tests rangeReader.
+func TestRangeReader(t *testing.T) {
 	testCases := []struct {
 		data   string
 		minLen int64
@@ -126,15 +126,19 @@ func TestLimitReader(t *testing.T) {
 	}{
 		{"1234567890", 0, 15, nil},
 		{"1234567890", 0, 10, nil},
-		{"1234567890", 0, 5, errDataTooLarge},
-		{"123", 5, 10, errDataTooSmall},
+		{"1234567890", 0, 5, toObjectErr(errDataTooLarge, "test", "test")},
+		{"123", 5, 10, toObjectErr(errDataTooSmall, "test", "test")},
 		{"123", 2, 10, nil},
 	}
 
 	for i, test := range testCases {
 		r := strings.NewReader(test.data)
-		_, err := ioutil.ReadAll(limitReader(r, test.minLen, test.maxLen))
-		if err != test.err {
+		_, err := ioutil.ReadAll(&rangeReader{
+			Reader: r,
+			Min:    test.minLen,
+			Max:    test.maxLen,
+		})
+		if toObjectErr(err, "test", "test") != test.err {
 			t.Fatalf("test %d failed: expected %v, got %v", i+1, test.err, err)
 		}
 	}

cmd/post-policy_test.go

@@ -33,6 +33,34 @@ const (
 	iso8601DateFormat    = "20060102T150405Z"
 )
 
+func newPostPolicyBytesV4WithContentRange(credential, bucketName, objectKey string, expiration time.Time) []byte {
+	t := time.Now().UTC()
+	// Add the expiration date.
+	expirationStr := fmt.Sprintf(`"expiration": "%s"`, expiration.Format(expirationDateFormat))
+	// Add the bucket condition, only accept buckets equal to the one passed.
+	bucketConditionStr := fmt.Sprintf(`["eq", "$bucket", "%s"]`, bucketName)
+	// Add the key condition, only accept keys equal to the one passed.
+	keyConditionStr := fmt.Sprintf(`["eq", "$key", "%s"]`, objectKey)
+	// Add content length condition, only accept content sizes of a given length.
+	contentLengthCondStr := `["content-length-range", 1024, 1048576]`
+	// Add the algorithm condition, only accept AWS SignV4 Sha256.
+	algorithmConditionStr := `["eq", "$x-amz-algorithm", "AWS4-HMAC-SHA256"]`
+	// Add the date condition, only accept the current date.
+	dateConditionStr := fmt.Sprintf(`["eq", "$x-amz-date", "%s"]`, t.Format(iso8601DateFormat))
+	// Add the credential string, only accept the credential passed.
+	credentialConditionStr := fmt.Sprintf(`["eq", "$x-amz-credential", "%s"]`, credential)
+
+	// Combine all conditions into one string.
+	conditionStr := fmt.Sprintf(`"conditions":[%s, %s, %s, %s, %s, %s]`, bucketConditionStr,
+		keyConditionStr, contentLengthCondStr, algorithmConditionStr, dateConditionStr, credentialConditionStr)
+	retStr := "{"
+	retStr = retStr + expirationStr + ","
+	retStr = retStr + conditionStr
+	retStr = retStr + "}"
+
+	return []byte(retStr)
+}
+
 // newPostPolicyBytesV4 - creates a bare bones postpolicy string with key and bucket matches.
 func newPostPolicyBytesV4(credential, bucketName, objectKey string, expiration time.Time) []byte {
 	t := time.Now().UTC()
@@ -206,6 +234,59 @@ func testPostPolicyHandler(obj ObjectLayer, instanceType string, t TestErrHandle
 			t.Errorf("Test %d: %s: Expected the response status to be `%d`, but instead found `%d`", i+1, instanceType, testCase.expectedRespStatus, rec.Code)
 		}
 	}
+
+	testCases2 := []struct {
+		objectName         string
+		data               []byte
+		expectedRespStatus int
+		accessKey          string
+		secretKey          string
+		malformedBody      bool
+	}{
+		// Success case.
+		{
+			objectName:         "test",
+			data:               bytes.Repeat([]byte("a"), 1025),
+			expectedRespStatus: http.StatusNoContent,
+			accessKey:          credentials.AccessKeyID,
+			secretKey:          credentials.SecretAccessKey,
+			malformedBody:      false,
+		},
+		// Failed with entity too small.
+		{
+			objectName:         "test",
+			data:               bytes.Repeat([]byte("a"), 1023),
+			expectedRespStatus: http.StatusBadRequest,
+			accessKey:          credentials.AccessKeyID,
+			secretKey:          credentials.SecretAccessKey,
+			malformedBody:      false,
+		},
+		// Failed with entity too large.
+		{
+			objectName:         "test",
+			data:               bytes.Repeat([]byte("a"), 1024*1024+1),
+			expectedRespStatus: http.StatusBadRequest,
+			accessKey:          credentials.AccessKeyID,
+			secretKey:          credentials.SecretAccessKey,
+			malformedBody:      false,
+		},
+	}
+
+	for i, testCase := range testCases2 {
+		// initialize HTTP NewRecorder, this records any mutations to response writer inside the handler.
+		rec := httptest.NewRecorder()
+		req, perr := newPostRequestV4WithContentLength("", bucketName, testCase.objectName, testCase.data, testCase.accessKey, testCase.secretKey)
+		if perr != nil {
+			t.Fatalf("Test %d: %s: Failed to create HTTP request for PostPolicyHandler: <ERROR> %v", i+1, instanceType, perr)
+		}
+		// Since `apiRouter` satisfies `http.Handler` it has a ServeHTTP to execute the logic ofthe handler.
+		// Call the ServeHTTP to execute the handler.
+		apiRouter.ServeHTTP(rec, req)
+		if rec.Code != testCase.expectedRespStatus {
+			t.Errorf("Test %d: %s: Expected the response status to be `%d`, but instead found `%d`", i+1, instanceType, testCase.expectedRespStatus, rec.Code)
+		}
+	}
+
 }
 
 // postPresignSignatureV4 - presigned signature for PostPolicy requests.
@@ -267,7 +348,7 @@ func newPostRequestV2(endPoint, bucketName, objectName string, accessKey, secret
 	return req, nil
 }
 
-func newPostRequestV4(endPoint, bucketName, objectName string, objData []byte, accessKey, secretKey string) (*http.Request, error) {
+func newPostRequestV4Generic(endPoint, bucketName, objectName string, objData []byte, accessKey, secretKey string, contentLengthRange bool) (*http.Request, error) {
 	// Keep time.
 	t := time.Now().UTC()
 	// Expire the request five minutes from now.
@@ -276,6 +357,9 @@ func newPostRequestV4(endPoint, bucketName, objectName string, objData []byte, a
 	credStr := getCredential(accessKey, serverConfig.GetRegion(), t)
 	// Create a new post policy.
 	policy := newPostPolicyBytesV4(credStr, bucketName, objectName, expirationTime)
+	if contentLengthRange {
+		policy = newPostPolicyBytesV4WithContentRange(credStr, bucketName, objectName, expirationTime)
+	}
 	// Only need the encoding.
 	encodedPolicy := base64.StdEncoding.EncodeToString(policy)
 
@@ -322,3 +406,11 @@ func newPostRequestV4(endPoint, bucketName, objectName string, objData []byte, a
 	req.Header.Set("Content-Type", w.FormDataContentType())
 	return req, nil
 }
+
+func newPostRequestV4WithContentLength(endPoint, bucketName, objectName string, objData []byte, accessKey, secretKey string) (*http.Request, error) {
+	return newPostRequestV4Generic(endPoint, bucketName, objectName, objData, accessKey, secretKey, true)
+}
+
+func newPostRequestV4(endPoint, bucketName, objectName string, objData []byte, accessKey, secretKey string) (*http.Request, error) {
+	return newPostRequestV4Generic(endPoint, bucketName, objectName, objData, accessKey, secretKey, false)
+}

cmd/postpolicyform.go

@@ -34,10 +34,14 @@ func toString(val interface{}) string {
 }
 
 // toInteger _ Safely convert interface to integer without causing panic.
-func toInteger(val interface{}) int {
+func toInteger(val interface{}) int64 {
 	switch v := val.(type) {
-	case int:
+	case float64:
+		return int64(v)
+	case int64:
 		return v
+	case int:
+		return int64(v)
 	}
 	return 0
 }
@@ -53,8 +57,8 @@ func isString(val interface{}) bool {
 
 // ContentLengthRange - policy content-length-range field.
 type contentLengthRange struct {
-	Min   int
-	Max   int
+	Min   int64
+	Max   int64
 	Valid bool // If content-length-range was part of policy
 }
 
@@ -136,7 +140,11 @@ func parsePostPolicyForm(policy string) (PostPolicyForm, error) {
 					Value:    value,
 				}
 			case "content-length-range":
-				parsedPolicy.Conditions.ContentLengthRange = contentLengthRange{toInteger(condt[1]), toInteger(condt[2]), true}
+				parsedPolicy.Conditions.ContentLengthRange = contentLengthRange{
+					Min:   toInteger(condt[1]),
+					Max:   toInteger(condt[2]),
+					Valid: true,
+				}
 			default:
 				// Condition should be valid.
 				return parsedPolicy, fmt.Errorf("Unknown type %s of conditional field value %s found in POST policy form",