net.maurus.authserver 0.1.77

A Python 3 Django-based OAuth2/Docker Auth/JWT SSO server with additional mail routing.

maurus.networks Authentication server

This is a Python Django based server application that provides single sign-on services for my own setup. It has OAuth2 endpoints and for applications that don’t support any of these: a SQL stored procedure database abstraction.

As a second application it provides dkimsigner, a daemon that speaks SMTP and receives mail, then forwards it to another SMTP port after signing it with a DKIM key from its database.

The third included application is mailforwarder. As OpenSMTPD 6.x does not offer a stable filter API and my OpenSMTPD setup already relies on the “stored procedure API”, mailforwarder provides a daemon speaking SMTP that resolves domains and email-addresses in authserver’s database and can then forward email to one-or-more other email addresses. Basically a .forward or .qmail implementation based on authserver’s database schema as a Python daemon.

It also provides Django manage.py commands for registering OAuth2 applications, users, domains and Docker registries. Those are useful for creating configuration entries through configuration management systems.

It also includes an implementation of the Docker Token Authentication protocol and can therefore be used to secure Docker registries for push and pull with SSO credentials. The included manage.py command: manage.py dockerauth registry add ... allows script based setup.

Finally, it includes a checkpassword compatible client application that can be used to integrate Apache2 mod_authnz_external or DJB checkpassword compatible clients with authserver.

Users can use the admin interface to create “service users” which are specific aliases for user accounts that can be used with applications that don’t support OAuth2 so users don’t have to share their passwords with the service (equivalent to the same feature on Google Gmail).

Planned features

• OAuth2 applications can use a SSL client certificate to authenticate for a non-standard HTTP API to register as an OAuth2 client and get their OAuth2 credentials, cutting down on manual configuration.

• OpenID Connect support

• Service-specific username and passwords for systems that don’t support OAuth2/OIDC

• CAS support through mama-cas

• add Google Authenticator support via django-otp

Installation

There is no widely available Docker container available yet, but you can install from this repository:

$ virtualenv -p python3 authserver
$ authserver/bin/pip install net.maurus.authserver

Or for Debian 9.0 Stretch:

$ echo "deb http://repo.maurus.net/release/stretch mn-release main" >> /etc/apt/sources.list.d/maurusnet.list
$ apt update
$ apt install authserver authclient

APPCONFIG FOLDER

This application uses 12factor and in its systemd configuration loads its configuration from a appconfig folder.

Canonical reserved configuration folders for this app:

• /etc/appconfig/authserver

• /etc/appconfig/dkimsigner

• /etc/appconfig/mailforwarder

Run django-admin.py like this:

bin/envdir /etc/appconfig/authserver/env bin/django-admin.py [command]
    --settings=authserver.settings

12factor Environment configuration

Managed configuration

These environment variables must be placed in the appconfig folder manually (or through configuration management). You can just leave VAULT_* empty and set DATABASE_URL if you’re not planning on using Vault.

Variable	Description
VAULT_CA	Pinned CA to use to validate that we’re talking to the right Vault.
VAULT_DATABASE_PATH	The key path to read from Vault to get database credentials for a full access role.
DATABASE_PARENTROLE	The role that authserver should “sudo” into (via SET ROLE) after connecting to the database, i.e. the primary access role (only used with Vault).
DATABASE_NAME	The name of the database to connect to (only used with Vault).
DATABASE_URL	When client SSL certificates or usernames and passwords are used to connect to the database instead of Vault, then this URL (parsed by dj-database-url) is used to connect (only used without Vault).

Smartstack services

This application relies on the following smartstack services being available on localhost:

Port	Service	SSL Hostname
5432	PostgreSQL	postgresql.local
8200	Vault	vault.local

Smartstack registration and loadbalancing

Building

Build script

This application is meant to be built using GoPythonGo.

export REPO=maurusnet
export APTLY_DISTRIBUTION=mn-nightly
export APTLY_PUBLISH_ENDPOINT=s3:maurusnet:nightly/stretch
export GNUPGHOME=/etc/gpg-managed-keyring/
export VAULTWRAPPER_READ_PATH=secret/gpg/packaging_passphrase
/opt/gopythongo/bin/gopythongo -v /usr/local/authserver /path/to/source

Access methods

There are multiple ways to authenticate user accounts against this program. Offered APIs include OAuth2, CAS and a “if nothing else works” abstraction layer for direct user database access based on stored procedures.

Stored Procedure API

Since some applications (like OpenSMTPD and Dovecot) which are used by my saltshaker need lowest common denominator authentication, authserver includes a pgplsql stored procedure API tailored to OpenSMTPD to validate user accounts.

N	Function Name	Description
1	authserver_get_credentials( varchar)	Gets a username password pair for the provided email address together with the primary delivery email address. (Users can log in with every email alias and their account password.)
2	authserver_check_domain( varchar)	Checks whether the passed domain is a valid delivery domain.
3	authserver_resolve_alias(varchar, boolean)	Resolves email addresses to known MNUser or MailingList instances. Resolving a primary delivery address will return the “magic” value “virtmail” pointing to the system user normally handling email delivery if the boolean parameter is true. If the boolean parameter is false it will return the primary delivery address again. If the resolved address is a MailingList it will return the input unchanged.
4	authserver_iterate_users()	Returns a list of all valid delivery mailboxes.

Access to the stored procedure API is managed by the django-admin.py spapi command which allows you to grant access to database users, install the stored procedures on the database and check whether the stored procedures have been installed or if a specific database user has execute access to the stored procedures. For more information, please run:

/usr/local/authserver/bin/envdir /etc/appconfig/authserver/env/ \
    /usr/local/authserver/bin/django-admin.py spapi --help

OAuth2

authserver delivers OAuth2 support over the following endpoints:

• /o2/authorize/

• /o2/token/

• /o2/revoke_token/

You can create client applications and authorization scopes via the Django admin interface or manage.py oauth2|permissions and assign scopes to users and groups respectively. The authorization view will list the scopes for the user to approve unless automatic authorization is turned on for the OAuth2 client.

Docker Auth

authserver supports Docker-compatible JWTs using the “resource owner” OAuth2 flow via docker login at https://your.authserver.domain/docker/token/. You can generally just use docker login https://your.authserver.domain/ and create Docker registry instances and access rights to namespaces on that registry via the Django admin interface or the manage.py dockerauth command.

Propietary endpoints and mod_authnz_external

The checkpassword.py command-line script, also shipped in the authclient Debian package is compatible with djb checkpassword and Apache2 mod_authnz_external. It uses two proprietary API endpoints:

• /checkpassword/ which takes a username and optionally a list of scopes and password (for something akin to the “resource owner” OAuth2 flow) and issues a JWT that has the user’s assigned scopes and validates the password (if transmitted).

• /getkey/ exports a RSA public key for a domain registered with authserver to allow a client to validate an issued JWT.

You should prefer OAuth2 where possible as this solution will bring the client into possession of the user’s password. However, if you trust the client this is an alternative solution. Obviously it’s also an easy way to integrate legacy systems.

checkpassword.py can operate in 5 modes:

• -m init uses the getkey API to load a RSA public key for the authserver’s domain and output it to stdout or into a file.

• -m check behaves like init but makes no changes, it’s useful to check whether a domain has a JWT key to export or that key is readable to checkpassword on the file system.

• -m authext and -m checkpassword read username and password from stdin (either in the way specified by mod_authnz_external or djb checkpassword) and send them to the server to be validated. The program then either exits with exit code 0 (success), 1 if the auth domain is invalid, 2 if there are API connection problems and 3 for anything else.

• -m authextgroup validates a list of scopes for a username. This does not validate the user’s password. This is useful for mod_authnz_external’s GroupExternal configuration, but you must additionally authenticate the user.

The API endpoints respond with a JSON Web Token (JWT) with the following claims:

{
    "sub": "the provided username"
    "canonical_username": "the user's delivery_mailbox name"
    "authenticated": true or false depending on the status of the password check
    "authorized": true or false depending on whether the user has all submitted scopes,
    "scopes": ["a list of", "all the scopes", "assigned to this user"],
    "nbf": int(Unix Epoch timestamp of now minus 5 seconds),
    "exp": int(Unix Epoch timestamp of now plus 3600 seconds),
    "iss": "the auth domain name",
    "aud": "net.maurus.authclient"
}

TODO

• refactor Vault fullaccess role into actually granting access to new tables

Licensing

Please see the LICENSE document for the terms under which this source code is licensed.

This program includes a copy of django12factor which is licensed under The MIT License (MIT) Copyright (c) 2013-2017 Kristian Glass.

This program includes a copy of Select2 JavaScript library which is licensed user the MIT License (MIT) Copyright (c) 2012-2017 Kevin Brown, Igor Vaynberg, and Select2 contributors