From 5fbdd70de9ec878246536dc7fd052a364db65393 Mon Sep 17 00:00:00 2001
From: Praveen raj Mani <hackerpraveen@gmail.com>
Date: Tue, 26 Jun 2018 01:05:43 +0530
Subject: [PATCH] Minio handle for list_objects_v2 with a blank
 ContinuationToken (#5940)

minio will now return an error for a blank continuation token in list_objects_v2,so as in s3.

Fixes #5931
---
 cmd/api-errors.go                  |  7 ++++++-
 cmd/api-resources.go               | 12 +++++++++++-
 cmd/api-resources_test.go          | 27 ++++++++++++++++++++++++++-
 cmd/bucket-handlers-listobjects.go |  9 ++++++++-
 4 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/cmd/api-errors.go b/cmd/api-errors.go
index 8e9f520d7..6c4f1c988 100644
--- a/cmd/api-errors.go
+++ b/cmd/api-errors.go
@@ -193,6 +193,7 @@ const (
 	ErrHealMissingBucket
 	ErrHealAlreadyRunning
 	ErrHealOverlappingPaths
+	ErrIncorrectContinuationToken
 )
 
 // error code to APIError structure, these fields carry respective
@@ -842,7 +843,11 @@ var errorCodeResponse = map[APIErrorCode]APIError{
 		Description:    "Object storage backend is unreachable",
 		HTTPStatusCode: http.StatusServiceUnavailable,
 	},
-
+	ErrIncorrectContinuationToken: {
+		Code:           "InvalidArgument",
+		Description:    "The continuation token provided is incorrect",
+		HTTPStatusCode: http.StatusBadRequest,
+	},
 	// Add your error structure here.
 }
 
diff --git a/cmd/api-resources.go b/cmd/api-resources.go
index 55ee0dcd3..b5f2757c1 100644
--- a/cmd/api-resources.go
+++ b/cmd/api-resources.go
@@ -36,7 +36,17 @@ func getListObjectsV1Args(values url.Values) (prefix, marker, delimiter string,
 }
 
 // Parse bucket url queries for ListObjects V2.
-func getListObjectsV2Args(values url.Values) (prefix, token, startAfter, delimiter string, fetchOwner bool, maxkeys int, encodingType string) {
+func getListObjectsV2Args(values url.Values) (prefix, token, startAfter, delimiter string, fetchOwner bool, maxkeys int, encodingType string, errCode APIErrorCode) {
+	errCode = ErrNone
+
+	// The continuation-token cannot be empty.
+	if val, ok := values["continuation-token"]; ok {
+		if len(val[0]) == 0 {
+			errCode = ErrIncorrectContinuationToken
+			return
+		}
+	}
+
 	prefix = values.Get("prefix")
 	token = values.Get("continuation-token")
 	startAfter = values.Get("start-after")
diff --git a/cmd/api-resources_test.go b/cmd/api-resources_test.go
index b76fb18ca..7dc91bcd5 100644
--- a/cmd/api-resources_test.go
+++ b/cmd/api-resources_test.go
@@ -29,6 +29,7 @@ func TestListObjectsV2Resources(t *testing.T) {
 		fetchOwner                           bool
 		maxKeys                              int
 		encodingType                         string
+		errCode                              APIErrorCode
 	}{
 		{
 			values: url.Values{
@@ -47,6 +48,7 @@ func TestListObjectsV2Resources(t *testing.T) {
 			fetchOwner:   true,
 			maxKeys:      100,
 			encodingType: "gzip",
+			errCode:      ErrNone,
 		},
 		{
 			values: url.Values{
@@ -64,11 +66,34 @@ func TestListObjectsV2Resources(t *testing.T) {
 			fetchOwner:   true,
 			maxKeys:      1000,
 			encodingType: "gzip",
+			errCode:      ErrNone,
+		},
+		{
+			values: url.Values{
+				"prefix":             []string{"photos/"},
+				"continuation-token": []string{""},
+				"start-after":        []string{"start-after"},
+				"delimiter":          []string{"/"},
+				"fetch-owner":        []string{"true"},
+				"encoding-type":      []string{"gzip"},
+			},
+			prefix:       "",
+			token:        "",
+			startAfter:   "",
+			delimiter:    "",
+			fetchOwner:   false,
+			maxKeys:      0,
+			encodingType: "",
+			errCode:      ErrIncorrectContinuationToken,
 		},
 	}
 
 	for i, testCase := range testCases {
-		prefix, token, startAfter, delimiter, fetchOwner, maxKeys, encodingType := getListObjectsV2Args(testCase.values)
+		prefix, token, startAfter, delimiter, fetchOwner, maxKeys, encodingType, errCode := getListObjectsV2Args(testCase.values)
+
+		if errCode != testCase.errCode {
+			t.Errorf("Test %d: Expected error code:%d, got %d", i+1, testCase.errCode, errCode)
+		}
 		if prefix != testCase.prefix {
 			t.Errorf("Test %d: Expected %s, got %s", i+1, testCase.prefix, prefix)
 		}
diff --git a/cmd/bucket-handlers-listobjects.go b/cmd/bucket-handlers-listobjects.go
index f320eed11..da91fd238 100644
--- a/cmd/bucket-handlers-listobjects.go
+++ b/cmd/bucket-handlers-listobjects.go
@@ -70,8 +70,15 @@ func (api objectAPIHandlers) ListObjectsV2Handler(w http.ResponseWriter, r *http
 		return
 	}
 
+	urlValues := r.URL.Query()
+
 	// Extract all the listObjectsV2 query params to their native values.
-	prefix, token, startAfter, delimiter, fetchOwner, maxKeys, _ := getListObjectsV2Args(r.URL.Query())
+	prefix, token, startAfter, delimiter, fetchOwner, maxKeys, _, errCode := getListObjectsV2Args(urlValues)
+
+	if errCode != ErrNone {
+		writeErrorResponse(w, errCode, r.URL)
+		return
+	}
 
 	// In ListObjectsV2 'continuation-token' is the marker.
 	marker := token