Month: June 2014

As part of my new SafePad 1.3 release, I added a simple tool to help users generate passwords. I looked into many ways of generating secure passwords, but in the end I settled on a technique that was very simple, quick to implement, and produces complex to crack random passwords.

Safepad is commonly used as a password vault for storing passwords for multiple sites in one document. The document is then protected with up to 2 passwords. One feature that was requested was that of generating complex passwords straight into a SafePad document.

The solution I picked is demonstrated below. In SafePad, the maximum password length is restricted to 64 characters.

using System;
using System.Security.Cryptography;

namespace HauntedHouseSoftware.SecureNotePad.Tools
{
    public static class PasswordGenerator
    {
        public static string Generate(int passwordLength, bool singleCase)
        {
            if (passwordLength == 0)
            {
                throw new InvalidOperationException("passwordLength");
            }

            string password;

            using (var randomNumberGenerator = new RNGCryptoServiceProvider())
            {
                var randomNumber = new byte[64];
                randomNumberGenerator.GetBytes(randomNumber);

                password = Convert.ToBase64String(randomNumber);
            }

            password = password.Substring(0, passwordLength);

            if (singleCase)
            {
                password = password.ToLower();
            }

            return password;
        }
    }
}

A coding requirement was to generate passwords that where not repeatable, and to do this I used the RNGCryptoServiceProvider class in .NET. I have already discussed using RNGCryptoServiceProvider in a previous article.

Sometimes it is useful to be able to check for the existence of a windows service on a local or remote machine and also check the running status of that service. Doing this is very easy in .NET. The following snippets are taken from the windows services tests in the Post Deployment Smoke Tester.

var ctl = ServiceController.GetServices().FirstOrDefault(s => s.ServiceName == "MyService");
if (ctl == null) throw new AssertionException(string.Format("Service with name [{0}] was not found", "MyService"));

The snippet above will check for a named service on the local machine. You can also look for the existence of a service on a remote machine, but supplying the machine name in the call to GetServices, as shown below.

var ctl = ServiceController.GetServices("CENTLPBZBHV1").FirstOrDefault(s => s.ServiceName == "MyService");
if (ctl == null) throw new AssertionException(string.Format("Service with name [{0}] was not found on {1}", "MyService", "CENTLPBZBHV1"));

In this short article I want to show a useful code snippet that allows you to ping a remote computer, much like the command line tool ping.exe. This particular code snippet was taken from a Smoke Test from the Post Deployment Smoke Testing tool that I am the open source moderator for.

Usage of the PingHost method is very straight forward. You just call it and pass in a host name. In the example below that is “www.google.co.uk”, but it could be a server name or ip address.

using System;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;

namespace PingTester
{
    class Program
    {
        static void Main(string[] args)
        {
            string reply = PingHost("www.google.co.uk");
            Console.WriteLine(reply);
        }

        private static string PingHost(string host)
        {
            if (string.IsNullOrEmpty(host))
            {
                throw new ArgumentNullException("host");
            }

            var returnMessage = string.Empty;

            try
            {
                var address = GetIpFromHost(host);
                var pingOptions = new PingOptions(128, true);
                var ping = new Ping();
                var buffer = new byte[32];

                for (var i = 0; i < 4; i++)
                {
                    try
                    {
                        var pingReply = ping.Send(address, 5000, buffer, pingOptions);

                        if (pingReply != null)
                        {
                            switch (pingReply.Status)
                            {
                                case IPStatus.Success:
                                    returnMessage = string.Format("Reply from {0}: bytes={1} time={2}ms TTL={3}",
                                        pingReply.Address, pingReply.Buffer.Length, pingReply.RoundtripTime,
                                        pingReply.Options.Ttl);
                                    break;
                                case IPStatus.TimedOut:
                                    returnMessage = "Connection has timed out...";
                                    break;
                                default:
                                    returnMessage = string.Format("Ping failed: {0}", pingReply.Status);
                                    break;
                            }
                        }
                        else
                            returnMessage = "Connection failed for an unknown reason...";
                    }
                    catch (PingException ex)
                    {
                        returnMessage = string.Format("Connection Error: {0}", ex.Message);
                    }
                    catch (SocketException ex)
                    {
                        returnMessage = string.Format("Connection Error: {0}", ex.Message);
                    }
                }
            }
            catch (Exception ex)
            {
                throw new InvalidOperationException("Connection failed for an unknown reason...");
            }

            return returnMessage;
        }

        private static IPAddress GetIpFromHost(string host)
        {
            var address = Dns.GetHostEntry(host).AddressList[0];
            return address;
        }
    }
}

First of all a call is made to GetIpFromHost, which in turn call the .NET Dns.GetHostEntry method to resolve to an IP address. Then a call is made to Ping.Send(). At this point you will either get a success status or a timeout.  One thing to note though is that some enterprises have Ping disabled using group policy. If this is the case then you will get a “Connection has timed out error.”