Cross Platform lock + windows encryption

.vscode/launch.json

@@ -0,0 +1,15 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "Launch Package",
+            "type": "go",
+            "request": "launch",
+            "mode": "auto",
+            "program": "${fileDirname}"
+        }
+    ]
+}

cross_platform_lock.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/AzureAD/microsoft-authentication-extensions-for-go/flock"
+)
+
+type CrossPlatLock struct {
+	retryNumber            int
+	retryDelayMilliseconds time.Duration
+
+	lockFile *os.File
+
+	fileLock *flock.Flock
+
+	lockfileName string
+	locked       bool
+}
+
+func NewLock(lockFileName string, retryNumber int, retryDelayMilliseconds time.Duration) (CrossPlatLock, error) {
+	lockfile, err := os.Create(lockFileName)
+	if err != nil {
+		return CrossPlatLock{}, err
+	}
+	return CrossPlatLock{
+		lockfileName: lockFileName,
+		retryNumber:  retryNumber,
+		lockFile:     lockfile,
+		fileLock:     flock.New(lockfile.Name()),
+	}, nil
+}
+
+func (c CrossPlatLock) Lock() error {
+	for tryCount := 0; tryCount < c.retryNumber; tryCount++ {
+		err := c.fileLock.Lock()
+		if err != nil {
+			time.Sleep(c.retryDelayMilliseconds * time.Millisecond)
+			continue
+		} else {
+			if c.fileLock.Locked() {
+				c.fileLock.Fh.WriteString(fmt.Sprintf("{%d} {%s}", os.Getpid(), os.Args[0]))
+			}
+			c.locked = true
+			return nil
+		}
+	}
+	return errors.New("Failed to acquire lock")
+}
+
+func (c CrossPlatLock) UnLock() error {
+	if c.fileLock != nil {
+		if err := c.fileLock.Unlock(); err != nil {
+			return err
+		}
+		c.lockFile.Close()
+		if err := os.Remove(c.fileLock.Path()); err != nil {
+			return err
+		}
+		c.locked = false
+	}
+	return nil
+}

cross_platform_lock_test.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/AzureAD/microsoft-authentication-extensions-for-go/internal"
+)
+
+func spinThreads(noOfThreads int, sleepInterval time.Duration, t *testing.T) int {
+	cacheFile := "cache.txt"
+	var wg sync.WaitGroup
+	wg.Add(noOfThreads)
+	for i := 0; i < noOfThreads; i++ {
+		go func(i int) {
+			defer wg.Done()
+			acquireLockAndWriteToCache(i, sleepInterval, cacheFile)
+		}(i)
+	}
+	wg.Wait()
+	t.Cleanup(func() {
+		if err := os.Remove(cacheFile); err != nil {
+			log.Println("Failed to remove cache file", err)
+		}
+	})
+	return validateResult(cacheFile, t)
+}
+
+func acquireLockAndWriteToCache(threadNo int, sleepInterval time.Duration, cacheFile string) {
+	cacheAccessor := internal.NewFileAccessor(cacheFile)
+	lockfileName := cacheFile + ".lockfile"
+	lock, err := NewLock(lockfileName, 60, 100)
+	if err := lock.Lock(); err != nil {
+		log.Println("Couldn't acquire lock", err.Error())
+		return
+	}
+	defer lock.UnLock()
+	data, err := cacheAccessor.Read()
+	if err != nil {
+		log.Println(err)
+	}
+	var buffer bytes.Buffer
+	buffer.Write(data)
+	buffer.WriteString(fmt.Sprintf("< %d \n", threadNo))
+	time.Sleep(sleepInterval * time.Millisecond)
+	buffer.WriteString(fmt.Sprintf("> %d \n", threadNo))
+	cacheAccessor.Write(buffer.Bytes())
+}
+
+func validateResult(cacheFile string, t *testing.T) int {
+	count := 0
+	var prevProc string = ""
+	var tag string
+	var proc string
+	data, err := os.ReadFile(cacheFile)
+	if err != nil {
+		log.Println(err)
+	}
+	dat := string(data)
+	temp := strings.Split(dat, "\n")
+	for _, ele := range temp {
+		if ele != "" {
+			count += 1
+			split := strings.Split(ele, " ")
+			tag = split[0]
+			proc = split[1]
+			if prevProc != "" {
+				if proc != prevProc {
+					t.Fatal("Process overlap found")
+				}
+				if tag != ">" {
+					t.Fatal("Process overlap found")
+				}
+				prevProc = ""
+
+			} else {
+				if tag != "<" {
+					t.Fatal("Opening bracket not found")
+				}
+				prevProc = proc
+			}
+		}
+	}
+	return count
+}
+func TestForNormalWorkload(t *testing.T) {
+	noOfThreads := 4
+	sleepInterval := 100
+	n := spinThreads(noOfThreads, time.Duration(sleepInterval), t)
+	if n != 4*2 {
+		t.Fatalf("Should not observe starvation")
+	}
+}
+
+func TestForHighWorkload(t *testing.T) {
+	noOfThreads := 80
+	sleepInterval := 100
+	n := spinThreads(noOfThreads, time.Duration(sleepInterval), t)
+	if n > 80*2 {
+		t.Fatalf("Starvation or not, we should not observe garbled payload")
+	}
+}

flock/.gitignore

@@ -0,0 +1,24 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof

flock/.travis.yml

@@ -0,0 +1,10 @@
+language: go
+go:
+  - 1.14.x
+  - 1.15.x
+script: go test -v -check.vv -race ./...
+sudo: false
+notifications:
+  email:
+    on_success: never
+    on_failure: always

flock/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2015-2020, Tim Heckman
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+* Neither the name of gofrs nor the names of its contributors may be used
+  to endorse or promote products derived from this software without
+  specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

flock/README.md

@@ -0,0 +1,41 @@
+# flock
+[![TravisCI Build Status](https://img.shields.io/travis/gofrs/flock/master.svg?style=flat)](https://travis-ci.org/gofrs/flock)
+[![GoDoc](https://img.shields.io/badge/godoc-flock-blue.svg?style=flat)](https://godoc.org/github.com/gofrs/flock)
+[![License](https://img.shields.io/badge/license-BSD_3--Clause-brightgreen.svg?style=flat)](https://github.com/gofrs/flock/blob/master/LICENSE)
+[![Go Report Card](https://goreportcard.com/badge/github.com/gofrs/flock)](https://goreportcard.com/report/github.com/gofrs/flock)
+
+`flock` implements a thread-safe sync.Locker interface for file locking. It also
+includes a non-blocking TryLock() function to allow locking without blocking execution.
+
+## License
+`flock` is released under the BSD 3-Clause License. See the `LICENSE` file for more details.
+
+## Go Compatibility
+This package makes use of the `context` package that was introduced in Go 1.7. As such, this
+package has an implicit dependency on Go 1.7+.
+
+## Installation
+```
+go get -u github.com/gofrs/flock
+```
+
+## Usage
+```Go
+import "github.com/gofrs/flock"
+
+fileLock := flock.New("/var/lock/go-lock.lock")
+
+locked, err := fileLock.TryLock()
+
+if err != nil {
+	// handle locking error
+}
+
+if locked {
+	// do work
+	fileLock.Unlock()
+}
+```
+
+For more detailed usage information take a look at the package API docs on
+[GoDoc](https://godoc.org/github.com/gofrs/flock).

flock/appveyor.yml

@@ -0,0 +1,25 @@
+version: '{build}'
+
+build: false
+deploy: false
+
+clone_folder: 'c:\gopath\src\github.com\gofrs\flock'
+
+environment:
+  GOPATH: 'c:\gopath'
+  GOVERSION: '1.15'
+
+init:
+  - git config --global core.autocrlf input
+
+install:
+  - rmdir c:\go /s /q
+  - appveyor DownloadFile https://storage.googleapis.com/golang/go%GOVERSION%.windows-amd64.msi
+  - msiexec /i go%GOVERSION%.windows-amd64.msi /q
+  - set Path=c:\go\bin;c:\gopath\bin;%Path%
+  - go version
+  - go env
+
+test_script:
+  - go get -t ./...
+  - go test -race -v ./...