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A simple automatic update system, written in C# for a blog post.
using System;
using System.Net;
using System.IO;
using System.IO.Compression;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Diagnostics;
using System.Text;
using System.Security.Cryptography;
using System.Security.Permissions;
class Program
{
static string remoteVersionURL = "http://localhost:8090/program-version.txt";
static void Main(string[] args)
{
if(args.Length == 0)
{
Console.WriteLine("This helper program updates the main program. Call it like this:");
Console.WriteLine("\thelper.exe update");
return;
}
WebClient webClient = new WebClient();
switch(args[0].Trim().ToLower())
{
case "update":
Console.WriteLine("Checking for updates...");
// Format:
// <version> <url> <hash>
string remoteVersionText = webClient.DownloadString(remoteVersionURL).Trim();
string[] remoteVersionParts = (new Regex(@"\s+")).Split(remoteVersionText);
string remoteUrl = remoteVersionParts[1];
string remoteHash = remoteVersionParts[2];
if(!File.Exists("version.txt"))
{
Console.Write("No version file detected. Calling program to obtain version - ");
ProcessStartInfo startInfo = new ProcessStartInfo("program.exe");
startInfo.Arguments = "writeversion";
Process versionWriter = new Process();
versionWriter.StartInfo = startInfo;
versionWriter.Start();
versionWriter.WaitForExit();
Console.WriteLine("done.");
}
Version localVersion = new Version(File.ReadAllText("version.txt").Trim());
Version remoteVersion = new Version(remoteVersionParts[0]);
if(remoteVersion > localVersion)
{
// There is a new version on the server!
Console.WriteLine("There is a new version available on the server.");
Console.WriteLine("Current Version: {0}, New version: {1}", localVersion, remoteVersion);
while (true)
{
Console.Write("Perform update? ");
string response = Console.ReadLine().Trim().ToLower();
if (response.StartsWith("y"))
{
PerformUpdate(remoteUrl, remoteHash);
break;
}
else if (response.StartsWith("n"))
{
Console.WriteLine("Abort.");
break;
}
}
}
break;
default:
Console.WriteLine("Unknown command.");
break;
}
}
static bool PerformUpdate(string remoteUrl, string expectedHash)
{
Console.WriteLine("Beginning update.");
string downloadDestination = Path.GetTempFileName();
Console.Write("Downloading {0} to {1} - ", remoteUrl, downloadDestination);
WebClient downloadifier = new WebClient();
downloadifier.DownloadFile(remoteUrl, downloadDestination);
Console.WriteLine("done.");
Console.Write("Validating download - ");
string downloadHash = GetSHA1HashFromFile(downloadDestination);
if (downloadHash.Trim().ToLower() != expectedHash.Trim().ToLower()) {
// The downloaded file looks bad!
// Destroy it quick before it can do any more damage!
File.Delete(downloadDestination);
// Tell the user about what has happened
Console.WriteLine("Fail!");
Console.WriteLine("Expected {0}, but actually got {1}).", expectedHash, downloadHash);
Console.WriteLine("The downloaded update may have been modified by an attacker in transit!");
Console.WriteLine("Nothing has been changed, and the downloaded file deleted.");
return false;
}
else
Console.WriteLine("ok.");
// Since the download doesn't appear to be bad at first sight, let's extract it
Console.Write("Extracting archive - ");
string extractTarget = @"./downloadedFiles";
ZipFile.ExtractToDirectory(downloadDestination, extractTarget);
// Copy the extracted files and replace everything in the current directory to finish the update
// C# doesn't easily let us extract & replace at the same time
// From http://stackoverflow.com/a/3822913/1460422
foreach (string newPath in Directory.GetFiles(extractTarget, "*.*", SearchOption.AllDirectories))
File.Copy(newPath, newPath.Replace(extractTarget, "."), true);
Console.WriteLine("done.");
// Clean up the temporary files
Console.Write("Cleaning up - ");
Directory.Delete(extractTarget, true);
Console.WriteLine("done.");
return true;
}
/// <summary>
/// Gets the SHA1 hash from file.
/// Adapted from https://stackoverflow.com/a/16318156/1460422
/// </summary>
/// <param name="fileName">The filename to hash.</param>
/// <returns>The SHA1 hash from file.</returns>
static string GetSHA1HashFromFile(string fileName)
{
FileStream file = new FileStream(fileName, FileMode.Open);
SHA1 sha1 = new SHA1CryptoServiceProvider();
byte[] byteHash = sha1.ComputeHash(file);
file.Close();
StringBuilder hashString = new StringBuilder();
for (int i = 0; i < byteHash.Length; i++)
hashString.Append(byteHash[i].ToString("x2"));
return hashString.ToString();
}
}
using System;
using System.IO;
class Program
{
static string version = "0.1";
static void Main(string[] args)
{
// Write out our current version
File.WriteAllText("version.txt", version);
// Exit now if we were just asked for our version
if (args.Length > 0 && args[0].Trim().ToLower() == "writeversion")
return;
// Continue on with the main body of the program
Console.WriteLine("Rockets are cool.");
}
}
@r3xakead0

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commented Mar 6, 2018

Great!!

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