Nexus3 Gitlab Auth Plugin

This plugin adds a Gitlab realm to Sonatype Nexus OSS and enables you to authenticate with Gitlab Users and authorize with Gitlab Groups.

The plugin does not implement a full OAuth flow, instead you use your gitlab user name + an gitlab read_user token you generated in your account to log in to the nexus. This works through the web as well as through tools like maven, gradle etc.

Setup

1. Activate the Realm

Log in to your nexus and go to Administration > Security > Realms. Move the Gitlab Realm to the right. The realm order in the form determines the order of the realms in your authentication flow. We recommend putting Gitlab after the built-in realms:

2. Group / Roles Mapping

When logged in through Gitlab, all groups the user is a member of will be mapped into roles :

You need to manually create these roles in Administration > Security > Roles > (+) Create Role > Nexus Role in order to assign them the desired privileges. The Role ID should map to the group name. Note that by default nobody is allowed to login (authenticate).

Usage

The following steps need to be done by every developer who wants to login to your nexus with Gitlab.

1. Generate API Token

In your Gitlab account under generate a new token with read_user privilege.

2. Login to nexus

When logging in to nexus, use your gitlab user name as the username and the token you just generated as the password. This also works through maven, gradle etc.

Installation

0. Prerequisites

Directory naming convention:

For the following commands we assume your nexus installation resides in /opt/sonatype/nexus. See https://books.sonatype.com/nexus-book/reference3/install.html#directories for reference.

1. Download and install

The following lines will:

• create a directory in the nexus / kafka maven repository
• download the latest release from gitlab
• unzip the releae to the maven repository
• add the plugin to the karaf startup.properties.

mkdir -p /opt/sonatype/nexus/system/fr/auchan/ &&\
wget -O /opt/sonatype/nexus/system/fr/auchan/nexus3-gitlabauth-plugin-1.1.0.jar https://github.com/auchanretailfrance/nexus3-gitlabauth-plugin/releases/download/1.1.0/nexus3-gitlabauth-plugin-1.1.0.jar &&\
echo "mvn\:fr.auchan/nexus3-gitlabauth-plugin/1.1.0 = 200" >> /opt/sonatype/nexus/etc/karaf/startup.properties

2. Create configuration

Create /opt/sonatype/nexus/etc/gitlabauth.properties

Within the file you can configure the following properties:

Property	Description	Default
gitlab.api.url	URL of the Gitlab API to operate against.	https://gitlab.com
gitlab.api.key	An admin sudo API key to list groups of users.
gitlab.principal.cache.ttl	Java Duration for how long a given Access will be cached for. This is a tradeoff of how quickly access can be revoked and how quickly a Gitlab API will be called!	PT1M (1 Minute)

This is what an example file would look like:

gitlab.api.url=https://gitlab.com
gitlab.api.key=XXXXXXXXXXXXXXXXXXXXX
gitlab.principal.cache.ttl=PT1M

3. Restart Nexus

Restart your Nexus instance to let it pick up your changes.

Development

You can build the project with the integrated maven wrapper like so: ./mvnw clean package

You can also build locally using Docker by running docker run --rm -it -v $(pwd):/data -w /data maven:3.5.2 mvn clean package

You can build a ready to run docker image using the Dockerfile to quickly spin up a nexus with the plugin already preinstalled.

Credits

The whole project is heavily influenced by the, nexus3-github-oauth-plugin itself influenced by the nexus3-crowd-plugin.