jass

by jschauma

jschauma / jass

a tool to facilitate sharing of secrets using SSH keys

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Quick Summary

jass(1) is a tool to let you encrypt/decrypt data using SSH keys. Keys can be provided locally, fetched from LDAP, or retrieved from GitHub or another external keyserver.

Encryption:

$ jass -u jschauma 

Decryption:

jass -d -k ~/.ssh/privkey 

Please see the manual page for further details.

Installation

If you like to live fast and fetch binaries from the internet, you can install jass(1) via e.g.:

$ curl -s https://raw.githubusercontent.com/jschauma/jass/master/src/install.sh | sh

This will fetch the binary and manual page and attempt to install it under

${PREFIX}
. If you don't have write access to
${PREFIX}
, add sudo(8) before
sh
.

If you're on Mac OS X, you can install this package; that package is signed with my PGP key 6F6BD3D7 with the signature here.

$ cd packages/dmgs
$ gpg --verify jass.dmg.asc jass.dmg
gpg: Signature made Wed Oct 23 16:55:04 2019 EDT using RSA key ID 6F6BD3D7
gpg: Good signature from "Jan Schaumann "
gpg:                 aka "Jan Schaumann (@jschauma) "
gpg:                 aka "Jan Schaumann "
$ hdiutil mount -quiet jass.dmg
$ sudo installer -pkg /Volumes/Jass/jass-6.0.pkg -target /
installer: Package name is jass-6.0
installer: Upgrading at base path /
installer: The upgrade was successful.
$ hdiutil unmount /Volumes/Jass
"/Volumes/Jass" unmounted successfully.
$

Manual installation

$ make build

If you like, you can install the binary and the manual page somewhere convenient; the Makefile defaults to '/usr/local' but you can change the PREFIX:

$ make PREFIX=~ install

Details

Sharing Secrets

Every now and then we have a need to share a "secret" with some co-workers. Coordinating this can be problematic, since you would either need to be in the same physical space at the same time, or you would need to be able to talk over the phone (and know that who you're talking to is in fact the person you think you're talking to) etc. etc.

Wouldn't it be nice if you could just attach the file in question to an email, insert it into a ticketing system, or drop it on a shared host?

Using SSH Keys

Many organizations already use SSH keys for access to their hosts. That is, you have a central place (local file systems on shared hosts as well as, perhaps, LDAP) where you have public keys that you already trust to belong to the given person. Most engineers are familiar with ssh(1) and the use of ssh keys for authentication, but what not everybody might be aware of is that by their very nature these keys can also be used for encryption of non-SSH related data.

jass(1) does just that. It supports encryption for multiple keys and should generally be reasonably "user friendly".

Finding keys

You can specify the public key(s) to encrypt data for on the command-line. Alternatively, jass(1) can try to fetch the key(s) for a given user or members of a Unix group from LDAP or a keyserver.

You can specify the default method in the sources prior to building jass(1); support for a configuration file may be added in the future.

GitHub Service

By default, jass(1) will look for keys for the recipients on GitHub. It does so by retrieving the URL

https://api.github.com/users//keys
. If you prefer this not to happen, set the GITHUB_URL environment variable to the empty string.

Alternatively, you can set GITHUB_URL to e.g., an internal GitHub service endpoint such as

https://git.your.domain.com/api/v3
, and jass(1) will look for keys there. This also will work for specifying a GitHub "team" instead of a group, either in the format "org/team" or as a numeric team-id.

If you are using an internal GitHub service and require authentication, you can set the GITHUBAPITOKEN environment variable to enable Basic HTTP Auth. This token will require

read:org
and
read:user
privileges.

How to use jass(1)

Encrypting data

To encrypt the file service.yml for the local user jschauma and send it via email:

$ jass -u jschauma 

If you do not have a user named 'jschauma' on your local systems, nor in LDAP (if you set that up), then you can ask jass(1) to look that user's key on GitHub by specifying the '-G' flag:

For example, to encrypt a message for Linus Torvalds using his GitHub key, you might run:

$ echo "0-day in ext4, ping me for details" | jass -u torvalds

Please see the manual page for details and other examples.

Decrypting data

To decrypt data, you need to have access to the private ssh key in question. This means that this should not happen on a shared box but instead is likely to occur on your desktop, laptop or other private system:

jass -d -k ~/.ssh/privkey 

Supported Platforms

jass(1) is written in Go, so it should run pretty much anywhere that you can build a binary for. (An older version of jass(1) written in shell is also available in the 'src' directory.)

jass(1) was tested on the following systems:

  • RedHat Enterprise Linux 6.8
  • Mac OS X 10.15.2
  • NetBSD 8.0

FAQ

Why don't you just use PGP?

Why indeed. PGP has many advantages and more widespread use would make things a lot easier, but very few people appear to use it. SSH keys, on the other hand, are used nearly everywhere.

Why does this ask me for my passphrase when decrypting? Can't it get it from my ssh agent?

Unfortunately the key available in any possible ssh agent cannot be used by jass(1), since we are not actually using ssh(1) at all: we just happen to use an ssh key. If the key is encrypted, then we need to prompt the user for the passphrase.

Who wrote this tool?

jass(1) was originally written by Jan Schaumann ([email protected]) in April 2013.

You can read more about it here: * http://www.netmeister.org/blog/sharing-secrets-using-ssh-keys.html * http://www.netmeister.org/blog/jass.html * https://www.netmeister.org/blog/ssh2pkcs8.html

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