BUG/MINOR: prevent possible panics when generating random string

Author: oktalz

misc/misc.go

@@ -274,12 +274,26 @@ func HasOSArg(short, long, env string) bool {
 }
 
 func RandomString(size int) (string, error) {
-	b := make([]byte, size)
+	str, err := randomString(size)
+	if err != nil {
+		return "", err
+	}
+	for len(str) < size {
+		str2, _ := randomString(size)
+		str += str2
+	}
+	return str[:size], nil
+}
+
+// randomString generates a random string of the recommended size.
+// Result is not guaranteed to be correct length.
+func randomString(recommendedSize int) (string, error) {
+	b := make([]byte, recommendedSize+8)
 	_, err := rand.Read(b)
 	result := strings.ReplaceAll(base64.URLEncoding.EncodeToString(b), `=`, ``)
 	result = strings.ReplaceAll(result, `-`, ``)
 	result = strings.ReplaceAll(result, `_`, ``)
-	return result[:size], err
+	return result, err
 }
 
 func IsNetworkErr(err error) bool {

misc/misc_test.go

@@ -0,0 +1,34 @@
+// Copyright 2019 HAProxy Technologies
+//
+// 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 misc
+
+import (
+	"math/rand"
+	"testing"
+)
+
+func TestRandomString(t *testing.T) {
+	for i := 0; i < 1024; i++ {
+		size := rand.Intn(512)
+		str, err := RandomString(size)
+		if err != nil {
+			t.Errorf("RandomString returned an error for size %d: %v", size, err)
+		}
+		if len(str) != size {
+			t.Errorf("RandomString returned a string of length %d for size %d", len(str), size)
+		}
+	}
+}