Let the (Casino) Chips Fall Where They May

March 25th, 2020

MGM Drops

It has been more than 10 years since the Great Recession.

TypeScript: readonly vs. const

March 10th, 2020
Posted in TypeScript | No Comments

From The TypeScript Handbook:

The easiest way to remember whether to use readonly or const is to ask whether your using it on a variable or a property. Variables use const whereas properties use readonly.

Backup Procedure Using WSL

February 1st, 2020

Using Microsoft Windows Subsystem for Linux (WSL) to gain access to Linux command line tools within Microsoft Windows 10, I was able to create a consistent backup procedure that can be performed in Windows and Linux environments. I used SyncToy and File Checksum Integrity Verifier (FCIV) to perform backups before adopting this standard approach.

Except where noted, the following procedure can be performed in both Windows and Linux environments.

  1. Navigate to Desired Folder’s Parent.
    $ cd /mnt/c/myfolderparent

  2. Generate SHA1 Digest File.
    $ find ./myfolder -type f \
    -exec sha1sum -b "{}" + > ~/myfolder.sha1

  3. Verify SHA1 Digest File (optional).
    $ sha1sum -c ~/myfolder.sha1

    or

    $ sha1sum -c --quiet ~/myfolder.sha1

    Note: myfolder.sha1 contains relative paths. The above command requires execution from a directory where relative paths lead to the files desired for integrity checks.

  4. Mount Destination (optional)
    1. Create Mount Point
      $ mkdir /mnt/usbdrive

    2. Review Mount Options of Mounted Fixed Drives
      $ mount

    3. Mount Drive
      $ sudo mount -t drvfs f: /mnt/usbdrive \
      -o noatime,uid=1000,gid=1000

      This command is specific to Microsoft Windows; a similar command is available in the Linux environment. “f:” is the drive letter that Microsoft Windows assigned to the inserted USB drive in this example. Options are specified to match those highlighted above for the already mounted fixed drives.

  5. Perform Copy
    1. Dry Run
      $ rsync -n -av --delete --force --progress \
      --human-readable ./myfolder/ /mnt/usbdrive/myfolder

    2. Live Run
      $ rsync -av --delete --force --progress \
      --human-readable ./myfolder/ /mnt/usbdrive/myfolder

      The trailing ‘/’ of the source folder is important to the command’s correctness.

  6. Move Checksum File
    $ cp ~/myfolder.sha1 /mnt/usbdrive/.

  7. Verify File Integrity
    $ cd /mnt/usbdrive
    $ sha1sum -c myfolder.sha1

C#: Using Declaration

January 7th, 2020
Posted in C# | No Comments

Introduced in C# 8.0, the using-declaration language enhancement eliminates nested using-statements. The following code:

using System.IO;
class Program
{
  static void Main(string[] args)
  {
    var filename = "hello.txt";
    using (var stream = new FileStream(filename, FileMode.Create))
    {
      using (var writer = new StreamWriter(stream))
      {
        writer.WriteLine("Hello, World!");
      }
    }
  }
}

is improved with using declarations to the following:

using System.IO;
class Program
{
  static void Main(string[] args)
  {
    var filename = "hello.txt";
    using var stream = new FileStream(filename, FileMode.Create);
    using var writer = new StreamWriter(stream);

    writer.WriteLine("Hello, World!");
  }
}

Encrypting /home on Dell XPS 13 7390

November 28th, 2019
Posted in Security | 1 Comment

The following procedure adds encryption to pre-installed Ubuntu 18.04 on Dell XPS 13 7390:

  1. Within a console or terminal, sudo into root.
  2. $ sudo su -

  3. Create LUKS encrypted file container (20,000 Megabytes or 20GB, for example).
  4. # dd status=progress if=/dev/zero bs=1M count=20000 of=/.hostname-home.img
    # cryptsetup luksFormat /.hostname-home.img

  5. Open LUKS encrypted file container.
  6. # cryptsetup luksOpen /.hostname-home.img hostname-home

  7. Format encrypted filesystem.
  8. # mkfs.ext4 /dev/mapper/hostname-home

  9. Move original /home content to temporary location.
  10. # mkdir /root/home
    # mv /home/* /root/home/.

  11. Mount the encrypted filesystem.
  12. # mount /dev/mapper/hostname-home /home

  13. Move /home content into encrypted filesystem.
  14. # mv /root/home/* /home/.
    # rmdir /root/home

  15. Unmount the encrypted container, potentially flushing (writing) pending data to disk.
  16. # umount /home

  17. Close the LUKS encrypted file container, potentially flushing (writing) pending data to disk.
  18. # cryptsetup luksClose hostname-home

  19. Add entry into /etc/crypttab.
  20. # echo \
    "hostname-home /.hostname-home.img - tries=0" \
    >> /etc/crypttab

  21. Add entry into /etc/fstab.
  22. # echo \
    "/dev/mapper/hostname-home /home ext4 defaults 0 0" \
    >> /etc/fstab

I recently received my Dell XPS 13 7390 with pre-installed Ubuntu 18.04. My top concern is securing data such as private SSH keys and passwords saved by Internet browsers from the real possibility of losing my laptop to absent-mindedness or theft. My purist side insists on configuring full disk encryption by performing a fresh install from a publicly available Ubuntu download. My pragmatic side pushed me toward adopting the above procedure. Without the needed transparency from Dell on their additions to Ubuntu, it is difficult to determine whether a publicly available Ubuntu download will fully support the features of my new Dell XPS 7390. The above procedure encrypts any data writable by unprivileged users while remaining unprivileged. It introduces a basic layer of security while allowing enjoyment of a system configured by Dell.