django-sshkey

django-sshkey allows you to associate multiple SSH public keys with Django user accounts. It provides views to list, add, edit, and delete keys, each of which is intended for end-user consumption. It also provides a lookup view and corresponding lookup commands that are suitable for use with the AuthorizedKeysCommand feature in OpenSSH 6.2 and above.

The Django app

To use django-sshkey in your Django project, simply add django_sshkey to INSTALLED_APPS in settings.py, map the URLs into your project, and provide templates for the views (example templates are provided in the source).

In order to associate an incoming public key with a user you must define SSHKEY_AUTHORIZED_KEYS_OPTIONS in your project's settings.py. This should be a string containing options accepted by sshd, with {username} being replaced with the username of the user associated with the incoming public key.

django-sshkey can also help you keep track of when a key was last used. SSHKEY_AUTHORIZED_KEYS_OPTIONS also replaces {key_id} with the key's id. The command that is run can then notify django-sshkey that the key was used by issuing a HTTP POST to the lookup URL, placing the key_id in the request body.

For instance:

SSHKEY_AUTHORIZED_KEYS_OPTIONS = 'command="my-command {username} {key_id}",no-pty'

in settings.py will cause keys produced by the below commands to look similar to:

command="my-command fred 15",no-pty ssh-rsa AAAAB3NzaC1yc2E...

sshd would then verify the key is correct and run my-command. my-command would then know that this is fred and that he is using key 15, and could tell django-sshkey to update the last_used field of that key by running the equivalent of this command:

curl -d 15 http://localhost:8000/sshkey/lookup

Your URL may vary depending upon your configuration.

URL Configuration

This text assumes that your project's urls.py maps django_sshkey.urls into the URL namespace as follows:

import django_sshkey.urls
urlpatterns = patterns('',
  ...
  url('^sshkey/', include(django_sshkey.urls)),
  ...
)

You will need to adjust your URLs in the examples below if you use a different mapping.

Warning

The /sshkey/lookup URL can expose all public keys that have been uploaded to your site. Although they are public keys, it is probably a good idea to limit what systems can access this URL via your web server's configuration. Most of the lookup methods below require access to this URL, and only the systems that need to run the lookup commands should have access to it.

Settings

SSHKEY_AUTHORIZED_KEYS_OPTIONS

String, optional. Defines the SSH options that will be prepended to each public key. {username} will be replaced by the username; {key_id} will be replaced by the key's id. New in version 2.3.

SSHKEY_ALLOW_EDIT

Boolean, defaults to False. Whether or not editing keys is allowed. Note that no email will be sent in any case when a key is edited, hence the reason that editing keys is disabled by default. New in version 2.3.

SSHKEY_DEFAULT_HASH

String, either sha256, md5, or legacy (the default). The default hash algorithm to use for calculating the finger print of keys. Legacy behavior enforces OpenSSH's pre-6.8 behavior of MD5 without the MD5: prefix. New in version 2.5.

SSHKEY_EMAIL_ADD_KEY

Boolean, defaults to True. Whether or not an email should be sent to the user when a new key is added to their account. New in version 2.3.

SSHKEY_EMAIL_ADD_KEY_SUBJECT

String, defaults to "A new key was added to your account". The subject of the email that gets sent out when a new key is added. New in version 2.3.

SSHKEY_FROM_EMAIL

String, defaults to DEFAULT_FROM_EMAIL. New in version 2.3.

SSHKEY_SEND_HTML_EMAIL

Boolean, defaults to False. Whether or not multipart HTML emails should be sent. New in version 2.3.

Templates

Example templates are available in the templates.example directory.

sshkey/userkey_list.html

Used when listing a user's keys.

sshkey/userkey_detail.html

Used when adding or editing a user's keys.

sshkey/add_key.txt

The plain text body of the email sent when a new key is added. New in version 2.3.

sshkey/add_key.html

The HTML body of the email sent when a new key is added. New in version 2.3.

Management commands

import_sshkey [--auto-resolve] [--prefix PREFIX] [--name NAME] USERNAME KEY_PATH ...

Imports SSH public keys to tie to a user. If --auto-resolve/-a are given, attempt to generate unique key names using a UUID. The prefix used during this process is the key name, but can be changed using --prefix/-p.

normalize_sshkeys [USERNAME KEY_NAME]

Recalculates key data to reflect a changed setting, for instance, if you have changed SSHKEY_DEFAULT_HASH and some keys have incorrect fingerprints in your database. Given no arguments, all keys will be normalized. The username asnd key name are optional, and if specified, will limit affected keys to those owned by a user, or a particular key of a user. This can also be done via the administration panel, but if you have a large key database the request could end up timing out.

Tying OpenSSH to django-sshkey

There are multiple methods of connecting OpenSSH to django-sshkey. All of the methods listed here require the use of the AuthorizedKeysCommand directive in sshd_config present in OpenSSH 6.2 and above. Please note that the command that is referenced by this directive and its ancestor directories must be owned by root and writable only by owner.

Unless otherwise stated, all of the methods below use the SSHKEY_LOOKUP_URL environment variable to determine the URL of the /sshkey/lookup URL. If this environment variable is not defined then it will default to http://localhost:8000/sshkey/lookup. If this environment variable is defined in the sshd process then it will be inherited by the AuthorizedKeysCommand.

Additionally, all of the methods below use either curl (preferred) or wget. Some commands also use ssh-keygen. These commands must be present in PATH.

If you would prefer not to use these external commands then there are variants of the lookup commands implemented purely in Python. However, they are much slower. To use the variants, replace lookup with pylookup. For example, use django-sshkey-pylookup-all instead of django-sshkey-lookup-all.

Using django-sshkey-lookup

Usage: django-sshkey-lookup -a URL
       django-sshkey-lookup -u URL USERNAME
       django-sshkey-lookup -f URL FINGERPRINT
       django-sshkey-lookup URL [USERNAME]

This program has different modes of operation:

-a

Print all public keys.

-u

Print all public keys owned by the specified user.

-f

Print all public keys matching the specified fingerprint.

Default

Compatibility mode. If the username parameter is given then print all public keys owned by the specified user; otherwise perform the same functionality as django-sshkey-lookup-by-fingerprint (see below).

Starting with OpenSSH 6.9 and above, the AuthorizedKeysCommand directive supports the use of user-specified command line arguments, and different details about the authentication attempt are available to pass to the program. This makes django-sshkey-lookup a good fit for later versions of the OpenSSH server.

# Show all available public keys
AuthorizedKeysCommand /usr/local/bin/django-sshkey-lookup -a URL

# Filter keys owned by Django user (assuming the user matches)
AuthorizedKeysCommand /usr/local/bin/django-sshkey-lookup -u URL %u

# Filter keys matching a sha256 fingerprint
AuthorizedKeysCommand /usr/local/bin/django-sshkey-lookup -f URL %f

Note

If you choose to use OpenSSH's %f to filter by key fingerprint, know that it provides the sha256 fingerprint of the key by default. You can change the FingerprintHash directive in sshd_config to md5, but in either case you will need to set django-sshkey's SSHKEY_DEFAULT_HASH setting to sha256 or md5 to match. By default, django-sshkey emulates OpenSSH's pre-6.8 fingerprint behavior, which is a slightly different representation of an md5 hash. This is so it is backwards-compatible with its pre-2.5 behavior.

All modes expect that the lookup URL be specified as the first non-option parameter.

This command is compatible with the old script lookup.sh but was renamed to have a less ambiguous name when installed system-wide. A symlink is left in its place for backwards compatibility.

Using django-sshkey-lookup-all

Usage: django-sshkey-lookup-all

This program prints all SSH public keys that are defined on your site. sshd will have to scan through all of them to find the first match, so with many keys this method will be slow. However, it does not require a patched OpenSSH server.

This program:

• can be used directly with pre-6.9 AuthorizedKeysCommand (the username parameter is ignored).
• does not require a patched OpenSSH server.
• does not scale well to a large number of user keys.

Using django-sshkey-lookup-by-username

Usage: django-sshkey-lookup-by-username USERNAME

This program prints all SSH public keys that are associated with the specified user.

This program:

• can be used directly with pre-6.9 AuthorizedKeysCommand.
• does not require a patched OpenSSH server.
• is ideal if each Django user corresponds to a system user account.

Using django-sshkey-lookup-by-fingerprint

Usage: django-sshkey-lookup-by-fingerprint

This program prints all SSH public keys that match the given fingerprint. The fingerprint is determined by the first of the following that is found:

1. The SSH_KEY_FINGERPRINT environment variable, which should contain the MD5 fingerprint of the key (this is the second field generated by ssh-keygen -l).
2. The SSH_KEY environment variable, which should contain the key in standard openssh format (the same format as ~/.ssh/id_rsa.pub), is sent to ssh-keygen -l to determine the fingerprint.
3. The key in standard openssh format is read from standard input and is sent to ssh-keygen -l to determine the fingerprint.

This program:

• can be used directly with AuthorizedKeysCommand (the username parameter is ignored).
• requires a patched OpenSSH server; compatible patches can be found at one of the following locations:
  • openssh-akcenv (this is the preferred patch)
  • openssh-stdinkey
• is ideal if you want all Django users to access SSH via a shared system user account and be identified by their SSH public key.