Updating security groups

NuGet packages:

Programming elements:

using System;
using System.Threading.Tasks;
using System.Collections.Generic;
using Amazon.EC2;
using Amazon.EC2.Model;

namespace EC2AddRuleForRDP
{
  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class to add a rule that allows inbound traffic on TCP a port
  class Program
  {
    private const int DefaultPort = 3389;

    static async Task Main(string[] args)
    {
      // Parse the command line and show help if necessary
      var parsedArgs = CommandLine.Parse(args);
      if(parsedArgs.Count == 0)
      {
        PrintHelp();
        return;
      }

      // Get the application arguments from the parsed list
      var groupID = CommandLine.GetArgument(parsedArgs, null, "-g", "--group-id");
      var ipAddress = CommandLine.GetArgument(parsedArgs, null, "-i", "--ip-address");
      var portStr = CommandLine.GetArgument(parsedArgs, DefaultPort.ToString(), "-p", "--port");
      if(string.IsNullOrEmpty(ipAddress))
        CommandLine.ErrorExit("\nYou must supply an IP address in CIDR format.");
      if(string.IsNullOrEmpty(groupID) || !groupID.StartsWith("sg-"))
        CommandLine.ErrorExit("\nThe ID for a security group is missing or incorrect.");
      if(int.Parse(portStr) == 0)
        CommandLine.ErrorExit($"\nThe given TCP port number, {portStr}, isn't allowed.");

      // Add a rule to the given security group that allows
      // inbound traffic on a TCP port
      await AddIngressRule(
        new AmazonEC2Client(), groupID, ipAddress, int.Parse(portStr));
    }


    //
    // Method that adds a TCP ingress rule to a security group
    private static async Task AddIngressRule(
      IAmazonEC2 eC2Client, string groupID, string ipAddress, int port)
    {
      // Create an object to hold the request information for the rule.
      // It uses an IpPermission object to hold the IP information for the rule.
      var ingressRequest = new AuthorizeSecurityGroupIngressRequest{
        GroupId = groupID};
      ingressRequest.IpPermissions.Add(new IpPermission{
        IpProtocol = "tcp",
        FromPort = port,
        ToPort = port,
        Ipv4Ranges = new List<IpRange>() { new IpRange { CidrIp = ipAddress } }
      });

      // Create the inbound rule for the security group
      AuthorizeSecurityGroupIngressResponse responseIngress =
        await eC2Client.AuthorizeSecurityGroupIngressAsync(ingressRequest);
      Console.WriteLine($"\nNew RDP rule was written in {groupID} for {ipAddress}.");
      Console.WriteLine($"Result: {responseIngress.HttpStatusCode}");
    }


    //
    // Command-line help
    private static void PrintHelp()
    {
      Console.WriteLine(
        "\nUsage: EC2AddRuleForRDP -g <group-id> -i <ip-address> [-p <port>]" +
        "\n  -g, --group-id: The ID of the security group to which you want to add the inbound rule." +
        "\n  -i, --ip-address: An IP address or address range in CIDR format." +
        "\n  -p, --port: The TCP port number. Defaults to 3389.");
    }
  }


  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class that represents a command line on the console or terminal.
  // (This is the same for all examples. When you have seen it once, you can ignore it.)
  static class CommandLine
  {
    //
    // Method to parse a command line of the form: "--key value" or "-k value".
    //
    // Parameters:
    // - args: The command-line arguments passed into the application by the system.
    //
    // Returns:
    // A Dictionary with string Keys and Values.
    //
    // If a key is found without a matching value, Dictionary.Value is set to the key
    //  (including the dashes).
    // If a value is found without a matching key, Dictionary.Key is set to "--NoKeyN",
    //  where "N" represents sequential numbers.
    public static Dictionary<string,string> Parse(string[] args)
    {
      var parsedArgs = new Dictionary<string,string>();
      int i = 0, n = 0;
      while(i < args.Length)
      {
        // If the first argument in this iteration starts with a dash it's an option.
        if(args[i].StartsWith("-"))
        {
          var key = args[i++];
          var value = key;

          // Check to see if there's a value that goes with this option?
          if((i < args.Length) && (!args[i].StartsWith("-"))) value = args[i++];
          parsedArgs.Add(key, value);
        }

        // If the first argument in this iteration doesn't start with a dash, it's a value
        else
        {
          parsedArgs.Add("--NoKey" + n.ToString(), args[i++]);
          n++;
        }
      }

      return parsedArgs;
    }

    //
    // Method to get an argument from the parsed command-line arguments
    //
    // Parameters:
    // - parsedArgs: The Dictionary object returned from the Parse() method (shown above).
    // - defaultValue: The default string to return if the specified key isn't in parsedArgs.
    // - keys: An array of keys to look for in parsedArgs.
    public static string GetArgument(
      Dictionary<string,string> parsedArgs, string defaultReturn, params string[] keys)
    {
      string retval = null;
      foreach(var key in keys)
        if(parsedArgs.TryGetValue(key, out retval)) break;
      return retval ?? defaultReturn;
    }

    //
    // Method to exit the application with an error.
    public static void ErrorExit(string msg, int code=1)
    {
      Console.WriteLine("\nError");
      Console.WriteLine(msg);
      Environment.Exit(code);
    }
  }

}