A small tool for injecting files into new GitLab repos
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GitLab Boilerplate Injector


Read the blog post here to get the background.

What it does

This is a tool to help you make the initial commit in new GitLab repos. This allows you to inject helpful files, such as CI configuration, README, and .gitignore. It is configurable so you can have different groups/subgroups get different files injected into them.

Configuring and deploying the injector

Here are the tasks you should do to deploy the injector:

  1. Repo setup
  2. Edit the injectables
  3. Edit the group injection configs
  4. Setup GitLab API tokens
  5. Configure Serverless and GitLab CI
  6. Configure AWS IAM
  7. Push and deploy

Repo setup

Make a new repo in your GitLab instance to hold your copy of this injector and clone it to your system. Download a copy of this repo and put it in the local clone of your repo. DO NOT push yet! Because we use GitLab CI to deploy the injector, pushing now will attempt to trigger a deployment that will fail miserably. Hold off until the last step. If you must push, branch first to something other than master, as dev CI is currently disabled by default.

Edit the injectables

The actual files that get injected into the new repos are stored in the injectables folder. We have included some starter files that apply if you are using Node.js and Serverless. Feel free to change them to meet your needs.

Edit the group injection configs

What gets injected can be configured using regex. Let's say you have one group for Node.js projects and another for Python projects. New repos in each group can get appropriate files injected. The group-injection-configs.js file contains an array of these configurations. Each configuration is an object with a RegExp literal used to match the path and an array of paths that map local files to their destination in the new repo. See the default example below:

    regex: /.*/,
    paths: [
      { source: 'injectables/.gitignore', target: '.gitignore' },
      { source: 'injectables/.gitlab-ci.yml', target: '.gitlab-ci.yml' },
      { source: 'injectables/README.md', target: 'README.md' }

It is worth noting that you could even use this with an empty paths array to disable the injector for certain projects or groups.

GitLab API Tokens

You're going to need 2 different tokens for this to work. One is a system hook token (to validate that the request came from your GitLab instance) and the other is a personal access token for the GitLab API. Once we have these, we will add them to the repo where you will keep your copy of the injector.

Getting the System Hook Token

Go to /admin/hooks on your GitLab instance. You should see something like this:

System Hook Token Interface

Now, the only problem is that we don't have the URL yet. That's ok. Just create a complex and secure Secret Token value and make a note of it for later. It is also important to note that you do not need any extra triggers checked. We will have to circle back and finish this at the end.

Getting the Personal Access Token

Go to profile/personal_access_tokens on your GitLab instance. You should see something like this:

Personal Access Token Interface

To create one, give it a name, leave the Expires at blank (never expires), and check the api box under Scopes. Then click the Create personal access token button. After the page load, you will have a new token at the top of the page. Copy this and put it with your chosen System Hook Token from the last section.

Note: You may want to do this step with a unique account that doesn't belong to an actual user. This prevents problems if the token holder's user leaves your org and their account has to be deleted.

Storing the tokens securely

Go to <some group>/<your copy of the injector>/settings/ci_cd on your GitLab instance. Scroll to the Secret Variables section. You should see something like this:

Secret Variables Interface

Add the Personal Access Token with a key of GITLAB_API_TOKEN. Then add your chosen System Hook Token with a key of GITLAB_SYSHOOK_TOKEN. These variables will be securely passed into the CI process as environment variables, which will be picked up by Serverless and attached to the deployed Lambda function.

Configure Serverless and GitLab CI

We use Serverless Framework and GitLab CI for the deployment process. You'll find some todo!!!s in the serverless.yml and .gitlab-ci.yml (see below). If you don't fill those it, you're going to have a bad time. If you have any access restrictions (such as an IP filter) on your GitLab instance, you may need to deploy the injector into the same account and VPC as the GitLab instance. Just uncomment the vpc section of the serverless.yml and fill it in. The GITLAB_INSTANCE_ADDRESS can be an IP or domain name. If you are using the VPC functionality, you'll want to use the private IP of the instance here.

#  vpc: # uncomment and fill in as needed
#    securityGroupIds:
#      - # todo!!!
#    subnetIds:
#      - # todo!!!
    PROD_ACCOUNT: "AWS Account Number Here!!!" # todo!!!
    STAGING_ACCOUNT: "AWS Account Number Here!!!" # todo!!!
    DEV_ACCOUNT: "AWS Account Number Here!!!" # todo!!!

image: trek10/ci:3.4 # todo: swap in your CI docker image as needed

Configure AWS IAM

If you are working in an account or region that has not been used with GitLab CI, you must do some IAM work to get things going. There are 2 parts to doing this in a secure manner:

  1. Create/update an EC2 role in the account hosting the GitLab CI runner instance.
  2. Create a cross-account access role in the account hosting the deployed services.

The GitLab CI runner EC2 role

If the gitlab-ci-role EC2 role below does not exist in the account hosting the GitLab CI runner instance, create one and attach an inline policy like the one below.

gitlab-ci-role inline policy
    "Version": "2012-10-17",
    "Statement": [
            "Effect": "Allow",
            "Action": "sts:AssumeRole",
            "Resource": [

Retrieve the Role ID of this EC2 role with the following CLI command:

aws iam get-role --role-name gitlab-ci-role --query Role.RoleId --output text

The deployment cross-account trust role

Finally, create a gitlab-ci-deployment (or some other name ending in ci-deployment) cross account access role in the account hosting that will host the deployed services. This role should have the AdministratorAccess managed policy. In addition, it needs to have the trust relationship policy below. Be sure to fill in the GitLab CI host account number, the EC2 Role ID from the last step, and the GitLab CI runner's EC2 Instance ID (found in EC2 console).

gitlab-ci-deployment trust relationship policy document
  "Version": "2012-10-17",
  "Statement": [
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::<GitLabCIHostAcctNumber>:root"
      "Action": "sts:AssumeRole",
      "Condition": {
        "StringEquals": {
          "aws:userid": "<RoleId>:<EC2InstanceId>"

Push and deploy

If you have done everything correctly, you should be able to deploy the staging version by pushing/merging everything to master in your GitLab repo. If that succeeds, create a tag in GitLab to run the production deployment. View the log output from that deployment to get the API Gateway URL. It should look something like this: https://someuniquevaluehere.execute-api.us-east-1.amazonaws.com/prod/inject. Copy this URL and circle back to the System Hook interface. Now you can add a system hook with this URL and the Secret Token value that you created earlier.

Congrats! You're all done!