My GPG Config

Tuesday, November 28th, 2017

About

Some notes about my current setup for GPG/PGP.

I’m currently using GnuPG: https://www.gnupg.org/ and in particular GPG4Win.

Portable mode

As usual, I like portable installs and GPG is no exception. I’ve uncompressed it in my tools folder (synchronized across my machines). By itself, the tool is portable, maybe Kleopatra isn’t but I don’t care too much.

By default, Gpg4win installs in two locations:

  • Gpg4win: C:\Program Files (x86)\Gpg4win
  • GnuPG: C:\Program Files (x86)\GnuPG

Bash profile

Here’s how my bash profile is configured to have GPG tools available:

# GPG/PGP
# where the tool is installed
export GPG4WIN_HOME=$TOOLS_HOME/Gpg4Win_3.0.1
export GPG_HOME=$GPG4WIN_HOME/GnuPG
export KLEOPATRA_HOME=$GPG4WIN_HOME/Gpg4win

append_to_path $GPG_HOME
append_to_path $GPG_HOME/bin
append_to_path $KLEOPATRA_HOME/bin_64
append_to_path $KLEOPATRA_HOME/bin

# where it puts its files and looks for its configuration
export GNUPGHOME=$HOME/.gnupg

# create it otherwise it complains
mkdir -p `echo $GNUPGHOME`
alias gpg='gpg.exe'
alias pgp='gpg' # who cares ;-)
alias kleopatra='kleopatra.exe'

GPG configuration

Here’s my current GPG configuration (~/.gnupg/gpg.conf). I’ve removed comments for stuff I don’t use for clarity, although I like to keep those in my actual configs):

# get rid of the copyright notice
no-greeting

# key server
keyserver hkp://keys.gnupg.net

# Ensure that stronger secure hash algorithms are used by default
default-preference-list SHA512 SHA384 SHA256 SHA224 AES256 AES192 AES CAMELLIA256 CAMELLIA192 CAMELLIA128 TWOFISH CAST5 ZLIB BZIP2 ZIP Uncompressed
personal-digest-preferences SHA512
cert-digest-algo SHA512
 
# Enable the passphrase agent
use-agent
 
# Avoid locking files
lock-never

# Armor when exporting
armor
 
# Keyserver options
keyserver-options auto-key-retrieve include-subkeys honor-keyserver-url honor-pka-record
 
# Import/export options
import-options import-clean
export-options export-clean

# Don't use key ids are those are unsafe (both short and long!)
keyid-format none

With this configuration, I’ve forced the usage of stronger secure hash algorithms by default and also disabled key ids (short & long) since those are insecure. There’s nothing much to it.

How I generated my keys

First of all, I didn’t reinvent the wheel, I’ve mostly applied what Alex Cabal has described here, so thanks to him!

You might ask “Why not a simple key that does it all?”. Because in general, mixing signing and encryption keys is not a good idea, management & security wise. Firstly, different key types have different lifecycles. Secondly, it might just not be safe to do so.

Also, without this setup, if the keys I use on a daily bases were to be compromised, I wouldn’t have any other choice but to re-create everything from scratch (i.e., new identity!). With the configuration below I can just revoke a specific sub-key and create a new one, while keeping my identity.

Here’s the whole shabang.

Create the keypair

First of all, create the key:

gpg --gen-key

Settings to use:

  • Kind of key: (1) RSA and RSA
  • Key size: 4096 (longer = safer?)
  • Valid for: 0 (never expires)
  • mail: [email protected]

When selecting the passphrase, use a tool like Keepass, don’t choose the passphrase yourself, you’re not smart enough ;-).

Set strong hash preferences on the keypair

Just to make sure:

gpg --edit-key [email protected]
...
gpg> setpref SHA512 SHA384 SHA256 SHA224 AES256 AES192 AES CAMELLIA256 CAMELLIA192 CAMELLIA128 TWOFISH CAST5 ZLIB BZIP2 ZIP Uncompressed
gpg> save

Add a signing sub-key

Next, create a signing sub-key for code signing:

gpg --edit-key [email protected]
...
gpg> addkey
...
gpg> save

Settings:

  • Key type: (4) RSA (sign only)
  • Key size: 4096 (longer = safer?)
  • Valid for: 0 (never expires)
  • mail: [email protected]

Add an authentication sub-key

Next, create an authentication sub-key for SSH authentication:

gpg --expert --edit-key [email protected]
gpg>addkey
...
gpg>save

Settings:

  • (8) RSA (set your own capabilities)
  • S: disable sign
  • E: disable encrypt
  • A: enable authenticate
  • –> now you must see “Currently allowed actions: Authenticate”
  • Q: finished
  • Key size: 4096
  • Expires: today + 365 days

Create a revocation certificate

Generating a revocation certificate will allow me to later revoke this keypair if it is compromised. It must be kept safe because it can render my keys useless ;-)

gpg --output ./[email protected] --gen-revoke [email protected]

Export the keypair/subkeys to a safe location and make the key safe to use

First export the private key:

gpg --export-secret-keys --armor [email protected] > [email protected]

Then export the public key:

gpg --export --armor [email protected] > [email protected]

Finally, you can export the sub-keys alone:

gpg --export-secret-subkeys [email protected] > /tmp/gpg/subkeys

We’ll see why afterwards.

Ideally, you should export your private key to a temporary in-memory file system. Alex proposed the following:

mkdir /tmp/gpg # create a temp folder
sudo mount -t tmpfs -o size=1M tmpfs /tmp/gpg

Once that’s mounted, you can safely write there and remove the folder once you’re done.

Once exported, back-up those keys in a safe location (e.g., Keepass).

Once you’re 100% it’s backed-up, delete the secret key from the gpg keyring:

gpg --delete-secret-key [email protected]

Now re-import the sub-keys. With this you’ll only have the sub-keys at your disposal (and you don’t need more than that on a daily basis):

gpg --import /tmp/gpg/subkeys

So simple steps:

  • create/mount the temporary in-memory file system
  • export your private key
  • back it up in a safe location
  • remove the temporary file system
  • bonus: burn the machine you’ve done this upon ;-)

To verify that you didn’t mess up, go ahead and try to add a new sub-key; you shouldn’t be able to:

gpg --edit-key [email protected]
gpg> addkey
Secret parts of primary key are not available.
gpg: Key generation failed: No secret key

That’s it!

How I can revoke a sub-key

Using Google! Err I mean like this: https://wiki.debian.org/Subkeys.

First re-import my whole key (i.e., master + sub-keys)

gpg --allow-secret-key-import --import 

Second, edit the key and revoke the sub-key that I don’t want anymore:

gpg --edit-key [email protected]
gpg> list # list the keys
gpg> xyz # select the unwanted key
gpg> revkey # generate a revocation certificate
gpg> save

Once done, I can export/back-up the result and finally make sure to send the updated key to the key servers.

Where I’ve published my key

Once my key was ready, I’ve published it at various locations.

For starters I needed the full fingerprint (the 40 chars beauty):

gpg --fingerprint

In my case: 9AEC 7595 2F0F 8E52 65A8 4364 6448 ABB4 AEAD 81A2.

Just to be in the clear, if you need to share your key, always try to use the full fingerprint, certainly never the short version (8 hex chars one) nor the “long” (16 hex chars) since those are really unsafe.

First I sent the public key to the MIT key server using gpg:

gpg --send-keys [email protected]

Then I exported my public key to a file (ASCII-armored):

gpg --export --armor > dsebastien-pgp-key.asc

I then uploaded that file to my FTP, updated my about page to add the full fingerprint and a link to my public key. Then I added a blog post with the same information.

I’ve also sent an update on twitter the same. After that I’ve updated my Twitter bio to link to that tweet (optimizing character count :p).

Next up, I’ve uploaded the public key manually on Ubuntu’s key server.

Finally, I’ve updated my GitHub profile to add my PGP key.

Git client configuration

I’ve also updated my git client configuration in order to make my life easier.

  • git config –global user.signingkey 9AEC75952F0F8E5265A843646448ABB4AEAD81A2

This tells git which key to use. BTW, don’t enable automatic commit signing. Sign tags instead.

Verifying signatures is a breeze with git.

Later

In a later post, I’ll explain how I use my PGP keys with SSH, git and my Yubikey.

That’s all folks!

New PGP key

Monday, November 27th, 2017

I’ve got a new PGP key.

My PGP key fingerprint is: 9AEC 7595 2F0F 8E52 65A8  4364 6448 ABB4 AEAD 81A2

You can find my public PGP key here: https://dsebastien.net/pgp/dsebastien-pgp-key.asc

Brittany’s portraits

Tuesday, August 1st, 2017

2017-07-06 - 16h14 - 173.jpg 2017-07-06 - 15h17 - 101.jpg 2017-07-06 - 15h18 - 109.jpg 2017-07-06 - 16h25 - 193-2.jpg 2017-07-08 - 17h49 - 050.jpg 2017-07-06 - 17h05 - 223.jpg

Brittany’s nature

Tuesday, August 1st, 2017

2017-07-06 - 14h09 - 036.jpg 2017-07-06 - 14h59 - 069.jpg 2017-07-06 - 15h54 - 154.jpg 2017-07-06 - 15h55 - 155.jpg 2017-07-06 - 15h56 - 156.jpg 2017-07-06 - 16h09 - 162.jpg 2017-07-06 - 16h14 - 172.jpg 2017-07-06 - 16h19 - 182.jpg 2017-07-06 - 16h24 - 185.jpg 2017-07-07 - 10h35 - 016.jpg 2017-07-07 - 10h38 - 019-Pano.jpg 2017-07-07 - 10h39 - 027.jpg 2017-07-08 - 15h15 - 009.jpg

Brittany’s animals :)

Tuesday, August 1st, 2017

2017-07-06 - 15h42 - 123.jpg 2017-07-06 - 16h27 - 201.jpg 2017-07-06 - 16h51 - 216.jpg

Boats

Tuesday, August 1st, 2017

2017-07-06 - 15h44 - 137.jpg 2017-07-06 - 16h01 - 158.jpg 2017-07-07 - 17h28 - 049.jpg 2017-07-08 - 14h58 - 002-Pano.jpg

Vannes

Tuesday, August 1st, 2017

2017-07-09 - 10h58 - 010-Pano.jpg

Mont Saint-Michel

Tuesday, August 1st, 2017

2017-07-05 - 12h50 - 024.jpg 2017-07-05 - 12h55 - 033-Pano.jpg 2017-07-05 - 13h25 - 043.jpg

Battling against the 4.7.0 CrashPlan Synology package update

Saturday, May 21st, 2016

If you’re using CrashPlan to backup data on your Synology NAS in headless mode, you’ve probably already had to go through this update nightmare. This is pretty regular unfortunately; each time an update arrives for CrashPlan, the package gets broken in various ways.

Basically, clicking the “update” button always leads to a couple of hours wasted :(

Here’s how I fixed the issue this time, just in case it could help other people! Before you start, make sure you have a good hour in front of you.. ;-)
The commands are assumed to be executed as root…

  • close your eyes and update the package
  • start the package, it’ll download the update file then will crash and burn
  • copy cpio from the CrashPlan package to /bin/cpio: cp /var/packages/CrashPlan/target/bin/cpio /bin/cpio
  • extract the “upgrade” file: 7z e -o./ /var/packages/CrashPlan/target/upgrade.cpi
  • move the upgrade file outside the Crashplan folder
  • uninstall the CrashPlan package
  • install the CrashPlan package again (don’t let it start)
  • move back the upgrade file and put it in the upgrade folder (/var/packages/CrashPlan/target/upgrade)
  • edit install.vars in the CrashPlan folder to point to the correct location of Java on your NAS. To find it, just use ‘which java’. Then put the correct path for the JAVACOMMON property
  • (optional) rename the upgrade file to upgrade.jar (or whatever you like)
  • extract the upgrade file: 7z e -o/var/packages/CrashPlan/target/lib /var/packages/CrashPlan/target/upgrade/upgrade.jar
  • remove the upgrade file (not needed anymore)
  • remove the upgrade.cpi file
  • IF you have enough memory, then add the USR_MAX_HEAP property to /var/packages/CrashPlan/target/syno_package.vars
  • start the CrashPlan package; it should now stay up and running
  • install the latest CrashPlan client version on your machine
  • disable the Crashplan service on your machine
  • get the new Crashplan GUID on your NAS: cat /var/lib/crashplan/.ui_info; echo
  • copy the guid (everything before “,0.0.0.0”) in the ‘.ui_info’ file under C:\ProgramData\CrashPlan (assuming you’re on Windows). You must edit the file from a notepad executed as admin. Make sure to replace the IP (127.0.0.1) by the one of your NAS
  • Start the CrashPlan client, enter your CrashPlan credentials and passphrase (you do have one, right? :p)
  • Now let CrashPlan sync all your files for a few days :o)

Hope this helps!

Enjoy :)

So you want to be safe(r) while accessing your online bank account?

Saturday, May 14th, 2016

Web browsers

One quick tip: if you want to access sensitive Websites safely (e.g., your online bank, your taxes, …), then:

  • do so in a different Web browser than the one you generally use.
  • make sure that the browser you use for sensitive sites is NOT your default browser (i.e., the one that opens when you click on links in e-mails for example)
  • make sure that your browser is up to date
  • make sure that you never use that browser for anything else
  • do NOT visit anything else (i.e., no other tabs) at the same time
  • quickly check that you don’t have weird extensions or plugins installed (you could very well have been p0wned by any application installed on your machine)
  • make sure that you configure very strict security rules on that browser (e.g., disable caching, passwords/form data storage, etc)

Why does this help? Well if your machine isn’t part of a botnet or infected with hundreds of malwares yet, then the above could still protect you against commonly found vulnerabilities (e.g., cross-site request forgery), vulnerabilities exploited through a different tab in your browser, etc.

Personally I use Google Chrome as my default Web browser and Mozilla Firefox whenever I need to access sensitive sites.

Do NOT consider this as bulletproof though, it’s nothing but ONE additional thing you can do to protect yourself; you’re still exposed to many security risks, the Web is a dangerous place ;-)