GitHub Safe-Settings

Safe-settings– an app to manage policy-as-code and apply repository settings to repositories across an organization.

1. In safe-settings all the settings are stored centrally in an admin repo within the organization. This is important. Unlike Settings Probot, the settings files cannot be in individual repositories.
2. There are 3 levels at which the settings could be managed:
   1. Org-level settings are defined in .github/settings.yml
   2. Suborg level settings. A suborg is an arbitrary collection of repos belonging to projects, business units, or teams. The suborg settings reside in a yaml file for each suborg in the .github/suborgs folder.
   3. Repo level settings. They reside in a repo specific yaml in .github/repos folder
3. It is recommended to break the settings into org-level, suborg-level, and repo-level units. This will allow different teams to be define and manage policies for their specific projects or business units.With CODEOWNERS, this will allow different people to be responsible for approving changes in different projects.

Note: The settings file must have a .ymlextension only. .yaml extension is ignored, for now.

How it works

Events

The App listens to the following webhook events:

• push: If the settings are created or modified, that is, if push happens in the default branch of the admin repo and the file added or changed is .github/settings.yml or .github/repos/*.ymlor .github/suborgs/*.yml, then the settings would be applied either globally to all the repos, or specific repos. For each repo, the settings that is actually applied depend on the default settings for the org, overlayed with settings for the suborg that the repo belongs to, overlayed with the settings for that specific repo.

• repository.created: If a repository is created in the org, the settings for the repo - the default settings for the org, overlayed with settings for the suborg that the repo belongs to, overlayed with the settings for that specific repo - is applied.

• branch_protection_rule: If a branch protection rule is modified or deleted, safe-settings will sync the settings to prevent any unauthorized changes.

• repository.edited: If the default branch is changed if the the settings that would be applied for the repo

• pull_request.opened, pull_request.reopened, check_suite.requested: If the settings are changed, but it is not in the default branch, and there is an existing PR, the code will validate the settings changes by running safe-settings in nop mode and update the PR with the dry-run status.

Restricting safe-settings to specific repos

safe-settings can be turned on only to a subset of repos by specifying them in the runtime settings file, deployment-settings.yml.
If no file is specified, then the following repositories - 'admin', '.github', 'safe-settings' are exempted by default.
A sample of deployment-settings file is found here.

To apply safe-settings only to a specific list of repos, add them to the restrictedRepos section as include array.

To ignore safe-settings for a specific list of repos, add them to the restrictedRepos section as exclude array.

Custom rules

Admins setting up safe-settings can include custom rules that would be used to validate before applying a setting or overridding a broader scoped setting.

The code has to return true if validation is successful, or false if it isn't.

If the validation fails, the error attribute specified would be used to create the error message in the logs or in the PR checks.

The first use case is where a custom rule has to be applied for a setting on its own. For e.g. No collaborator should be given admin permissions.

For this type of validations, admins can provide custom code as configvalidators which validates the setting by itself.

For e.g. for the case above, it would look like:

configvalidators:
  - plugin: collaborators
    error: |
      `Admin role cannot be assigned to collaborators`
    script: |
      console.log(`baseConfig ${JSON.stringify(baseconfig)}`)
      return baseconfig.permission != 'admin'

For convenience this script has access to a variable, baseconfig, that contains the setting that is be applied.

The second use case is where custom rule has to be applied when a setting in the org or suborg level is being overridden. Such as, when default branch protection is being overridden.

For this type of validations, admins can provide custom code as overridevalidators. The script can access two variables, baseconfig and overrideconfig which represent the base setting and the setting that is overridding it.

A sample would look like:

overridevalidators:
  - plugin: branches   
    error: |
      `Branch protection required_approving_review_count cannot be overidden to a lower value`
    script: |
      console.log(`baseConfig ${JSON.stringify(baseconfig)}`)
      console.log(`overrideConfig ${JSON.stringify(overrideconfig)}`)
      if (baseconfig.protection.required_pull_request_reviews.required_approving_review_count && overrideconfig.protection.required_pull_request_reviews.required_approving_review_count ) {
        return overrideconfig.protection.required_pull_request_reviews.required_approving_review_count >= baseconfig.protection.required_pull_request_reviews.required_approving_review_count 
      }
      return true

A sample of deployment-settings file is found here.

Performance

When there are 1000s of repos to be managed -- and there is a global settings change -- safe-settings will have to work efficiently and only make the neccessary API calls.

The app also has to complete the work within an hour: the lifetime of the GitHub app token.

To address these constraints the following design decisions have been implemented:

1. Probot automatically handles rate and abuse limits.
2. Instead of loading all the repo contents from .github/repos/*, it will selectively load the specific repo file based on which repo settings has changed, or a subset of the repo files associated with suborg settings that has changed. The only time all the repo files will be loaded is if there is a global settings file change.
3. The PR check will only provide a summary of errors and changes. (Providing the details of changes for 1000s of repos will error out.)
4. To ensure it handles updates to GitHub intelligently, it will compare the changes with the settings in GitHub, and will call the API only if there are real changes.

Comparing changes with GitHub

To determine if there are real changes, the code will generate a detailed list of additions, modifications, and deletions compared to the settings in GitHub:

For e.g:

If the settings is:

{
  "branches": [
    {
      "name": "master",
      "protection": {
        "required_pull_request_reviews": {
          "required_approving_review_count": 2,
          "dismiss_stale_reviews": false,
          "require_code_owner_reviews": true,
          "dismissal_restrictions": {}
        },
        "required_status_checks": {
          "strict": true,
          "contexts": []
        },
        "enforce_admins": false
      }
    }
  ]
}

and the settings in GitHub is:

{
     "branches": [
       {
         "name": "master",
         "protection": {
            url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection",
           "required_status_checks": {
              url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/required_status_checks",
             "strict": true,
             "contexts": [],
              contexts_url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/required_status_checks/contexts",
             "checks": []
           },
           "restrictions": {
              url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/restrictions",
              users_url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/restrictions/users",
              teams_url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/restrictions/teams",
              apps_url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/restrictions/apps",
             "users": [],
             "teams": [],
             "apps": []
           },
           "required_pull_request_reviews": {
              url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/required_pull_request_reviews",
             "dismiss_stale_reviews": true,
             "require_code_owner_reviews": true,
             "required_approving_review_count": 2,
             "dismissal_restrictions": {
                url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/dismissal_restrictions",
                users_url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/dismissal_restrictions/users",
                teams_url": "https://api.github.com/repos/decyjphr-org/test/branches/develop/protection/dismissal_restrictions/teams",
               "users": [],
               "teams": []
             }
           },
           "required_signatures": false,
           "enforce_admins": false,
           "required_linear_history": false,
           "allow_force_pushes": {
             "enabled": false
           },
           "allow_deletions": false,
           "required_conversation_resolution": false
         }
       }
     ]
   }

the results of comparison would be:

{
      "additions": {},
      "modifications": {
        "branches": [
          {
            "protection": {
              "required_pull_request_reviews": {
                "dismiss_stale_reviews": false
              }
            },
            "name": "master"
          }
        ]
      },
      "hasChanges": true
    }

Schedule

The App can be configured to apply the settings on a schedule. This could a way to address configuration drift since webhooks have not always guaranteed to be delivered.

To set periodically converge the settings to the configuration, set the CRON environment variable. This is based on node-cron and details on the possible values can be found [here](#Env variables).

Pull Request Workflow

Safe-settings explicitly looks in the admin repo in the organization for the settings files. The admin repo could be a restricted repository with branch protections and codeowners

In that set up, when a changes happen to the settings files and there is a PR for merging the changes back to the default branch in the admin repo, safe-settings will run checks – which will run in nop mode and produce a report of the changes that would happen, including the API calls and the payload.

The checks will fail if org-levelbranch protections are overridden at the repo or suborg level with a lesser number of required approvers.

The Settings file

The settings file can be used to set the policies at the Org, suborg or repo level.

Using the settings, the following things could be configured:

• Repository settings - home page, url, visibility, has_issues, has_projects, wikis, etc.
• default branchnaming and renaming
• Repository Topics
• Teams and permissions
• Collaborators and permissions
• Issue labels
• Branch protections. If the name of the branch is default in the settings, it is applied to the default branch of the repo.
• Autolinks
• repository name validation using regex pattern

It is possible to provide an include or exclude settings to restrict the collaborators, teams, labels to a list of repos or exclude a set of repos for a collaborator.

Here is an example settings file:

# These settings are synced to GitHub by https://github.com/github/safe-settings

repository: 
  # This is the settings that need to be applied to all repositories in the org 
  # See https://docs.github.com/en/rest/reference/repos#create-an-organization-repository for all available settings for a repository  
  # A short description of the repository that will show up on GitHub
  description: description of the repo
  
  # A URL with more information about the repository
  homepage: https://example.github.io/
    
  # Keep this as true for most cases
  # A lot of the policies below cannot be implemented on bare repos
  # Pass true to create an initial commit with empty README.
  auto_init: true
    
  # A list of topics to set on the repository - can alternatively set like this: [github, probot, new-topic, another-topic, topic-12]
  topics:
  - github
  - probot
  - new-topic
  - another-topic
  - topic-12
  
  # Either `true` to make the repository private, or `false` to make it public. 
  # If this value is changed and if Org members cannot change the visibility of repos
  # it would result in an error when updating a repo
  private: true
  
  # Can be public or private. If your organization is associated with an enterprise account using 
  # GitHub Enterprise Cloud or GitHub Enterprise Server 2.20+, visibility can also be internal. 
  visibility: private
  
  # Either `true` to enable issues for this repository, `false` to disable them.
  has_issues: true
  
  # Either `true` to enable projects for this repository, or `false` to disable them.
  # If projects are disabled for the organization, passing `true` will cause an API error.
  has_projects: true
  
  # Either `true` to enable the wiki for this repository, `false` to disable it.
  has_wiki: true
  
  # The default branch for this repository.
  default_branch: main-enterprise
  
  # Desired language or platform [.gitignore template](https://github.com/github/gitignore) 
  # to apply. Use the name of the template without the extension. 
  # For example, "Haskell".
  gitignore_template: node
  
  # Choose an [open source license template](https://choosealicense.com/) 
  # that best suits your needs, and then use the 
  # [license keyword](https://help.github.com/articles/licensing-a-repository/#searching-github-by-license-type) 
  # as the `license_template` string. For example, "mit" or "mpl-2.0".
  license_template: mit
  
  # Either `true` to allow squash-merging pull requests, or `false` to prevent
  # squash-merging.
  allow_squash_merge: true
  
  # Either `true` to allow merging pull requests with a merge commit, or `false`
  # to prevent merging pull requests with merge commits.
  allow_merge_commit: true
  
  # Either `true` to allow rebase-merging pull requests, or `false` to prevent
  # rebase-merging.
  allow_rebase_merge: true
  
  # Either `true` to allow auto-merge on pull requests, 
  # or `false` to disallow auto-merge.
  # Default: `false`
  allow_auto_merge: true
  
  # Either `true` to allow automatically deleting head branches 
  # when pull requests are merged, or `false` to prevent automatic deletion.
  # Default: `false`
  delete_branch_on_merge: true  
      
# The following attributes are applied to any repo within the org
# So if a repo is not listed above is created or edited
# The app will apply the following settings to it
labels:
  # Labels: define labels for Issues and Pull Requests
  - name: bug
    color: CC0000
    description: An issue with the system

  - name: feature
    # If including a `#`, make sure to wrap it with quotes!
    color: '#336699'
    description: New functionality.

  - name: first-timers-only
    # include the old name to rename an existing label
    oldname: Help Wanted
    color: '#326699'

  - name: new-label
    # include the old name to rename an existing label
    oldname: Help Wanted
    color: '#326699'

milestones:
# Milestones: define milestones for Issues and Pull Requests
  - title: milestone-title
    description: milestone-description
    # The state of the milestone. Either `open` or `closed`
    state: open

collaborators:
# Collaborators: give specific users access to any repository.
# See https://docs.github.com/en/rest/reference/collaborators#add-a-repository-collaborator for available options
- username: regpaco
  permission: push
# The permission to grant the collaborator. Can be one of:
# * `pull` - can pull, but not push to or administer this repository.
# * `push` - can pull and push, but not administer this repository.
# * `admin` - can pull, push and administer this repository.
- username: beetlejuice
  permission: pull
# You can exclude a list of repos for this collaborator and all repos except these repos would have this collaborator
  exclude:
  - actions-demo
- username: thor
  permission: push
# You can include a list of repos for this collaborator and only those repos would have this collaborator
  include:
  - actions-demo
  - another-repo

teams:
# Teams See https://docs.github.com/en/rest/reference/teams#create-a-team for available options
  - name: core
    # The permission to grant the team. Can be one of:
    # * `pull` - can pull, but not push to or administer this repository.
    # * `push` - can pull and push, but not administer this repository.
    # * `admin` - can pull, push and administer this repository.
    permission: admin
  - name: docss
    permission: push
  - name: docs
    permission: pull
  # Visibility is only honored when the team is created not for existing teams.
  # It can be either secret (default) or closed (visible to all members of the org)
  - name: globalteam
    permission: push
    visibility: closed

branches:
  # If the name of the branch value is specified as `default`, then the app will create a branch protection rule to apply against the default branch in the repo
  - name: default
    # https://docs.github.com/en/rest/reference/branches#update-branch-protection
    # Branch Protection settings. Set to null to disable
    protection:
      # Required. Require at least one approving review on a pull request, before merging. Set to null to disable.
      required_pull_request_reviews:
        # The number of approvals required. (1-6)
        required_approving_review_count: 1
        # Dismiss approved reviews automatically when a new commit is pushed.
        dismiss_stale_reviews: true
        # Blocks merge until code owners have reviewed.
        require_code_owner_reviews: true
        # Specify which users and teams can dismiss pull request reviews. Pass an empty dismissal_restrictions object to disable. User and team dismissal_restrictions are only available for organization-owned repositories. Omit this parameter for personal repositories.
        dismissal_restrictions:
          users: []
          teams: []
      # Required. Require status checks to pass before merging. Set to null to disable
      required_status_checks:
        # Required. Require branches to be up to date before merging.
        strict: true
        # Required. The list of status checks to require in order to merge into this branch
        contexts: []
      # Required. Enforce all configured restrictions for administrators. Set to true to enforce required status checks for repository administrators. Set to null to disable.
      enforce_admins: true
      # Required. Restrict who can push to this branch. Team and user restrictions are only available for organization-owned repositories. Set to null to disable.
      restrictions:
        apps: []
        users: []
        teams: []

# See the docs (https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/managing-repository-settings/configuring-autolinks-to-reference-external-resources) for a description of autolinks and replacement values.
autolinks:
  - key_prefix: 'JIRA-'
    url_template: 'https://jira.github.com/browse/JIRA-<num>'
  - key_prefix: 'MYLINK-'
    url_template: 'https://mywebsite.com/<num>'
        
validator:
  #pattern: '[a-zA-Z0-9_-]+_[a-zA-Z0-9_-]+.*' 
  pattern: '[a-zA-Z0-9_-]+'

Additional values

In addition to these values above, the settings file can have some addtional values

1. force_create: This is set in the repo-level settings to force create the repo if the repo does not exist.
2. template: This is set in the repo-level settings, and is used with the force_createflag to use a specific repo template when creating the repo
3. suborgrepos: This is set in the suborg-level settings to define an array of repos. This field can also take a glob pattern to allow wild-card expression to specify repos in a suborg. For e.g. test*would include test, test1, testing, etc.
4. The suborgteams section contains a list of teams, and all the repos belonging to the teams would be part of the suborg

Env variables

You can pass environment variables; easiest way to do it is in a .envfile.

1. CRON you can pass a cron input to run safe-settings at a regular schedule. This is based on node-cron. For eg.

# ┌────────────── second (optional)
# │ ┌──────────── minute
# │ │ ┌────────── hour
# │ │ │ ┌──────── day of month
# │ │ │ │ ┌────── month
# │ │ │ │ │ ┌──── day of week
# │ │ │ │ │ │
# │ │ │ │ │ │
# * * * * * *
CRON=* * * * * # Run every minute

1. Logging level could be set using LOG_LEVEL. For e.g.

LOG_LEVEL=trace

Runtime Settings

1. Besides the above settings files, the application can be bootstrapped with runtime settings.
2. The runtime settings are configured in deployment-settings.yml that is in the directory from where the GitHub app is running.
3. Currently the only setting that is possible are restrictedRepos: [... ] which allows you to configure a list of repos within your org that are excluded from the settings. If the deployment-settings.yml is not present, the following repos are added by default to the restrictedrepos list: 'admin', '.github', 'safe-settings'

Notes

1. Label color can also start with #, e.g. color: '#F341B2'. Make sure to wrap it with quotes!
2. Each top-level element under branch protection must be filled (eg: required_pull_request_reviews, required_status_checks, enforce_admins and restrictions). If you don't want to use one of them you must set it to null (see comments in the example above). Otherwise, none of the settings will be applied.
3. The precedence order is repository > suborg > org (.github/repos/.yml > .github/suborgs/.yml > .github/settings.yml

How to use

1. Install the app.

2. Create an admin repo within your organization (the repository must be called admin).

3. Add the settings for the org, suborgs, and repos . List of sample files could be found here.

Deployment

See docs/deploy.md if you would like to run your own instance of this plugin.

License

safe-settings is licensed under the ISC license

safe-settings uses 3rd party libraries, each with their own license. These are found here.