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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 <service.yml | \
        mail -s "Please do the needful!" jschauma

Decryption:

jass -d -k ~/.ssh/privkey <secret

Please see the manual page for further details.

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

jass(1) can query a GitHub server to retrieve public SSH keys by pointing the GITHUB_URL environment variable to the appropriate API end point (e.g. https://api.github.com/users/<user>/keys).

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

KeyKeeper Server

jass(1) can query a "KeyKeeper" server to retrieve public SSH keys. When doing so, it expects the server to respond with JSON data in the format of:

{
  "result" : {
    "keys" : {
      "key" : [
        {
          "trust"     : "string",
          "content"   : "ssh-rsa AAAAB3NzaC1...",
          "sudo"      : "string",
          "type"      : "string",
          "validated" : "string",
          "api"       : "string"
        },
        ...
      ]
    },
    "status" : "string",
    "user"   : "string"
  }
}

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 <service.yml | \
        mail -s "Please do the needful!" 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 <secret

Installing jass

If you run an x86-64 based RPM based Linux version, you can download an RPM of jass(1) from here (gpg signature).

If you run OS X, you can download a DMG installer from here (gpg signature).

The PGP signatures are created using this PGP key.

If you want to build jass(1) yourself, you can run:

git clone https://github.com/jschauma/jass.git
cd jass
make install

This will copy the binary and manual page under /usr/local or wherever PREFIX points to.

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 10.12.6
  • NetBSD 7.0.2

FAQ

Why don't we 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. If you're interested in getting an introduction to PGP, I'll gladly come and give you and your team a presentation.

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 (jschauma@netmeister.org) in April 2013.

You can read more about it here: