Rack::SlackRequestVerification

Rack middleware to verify Slack requests made using signed secrets.

Add this line to your application's Gemfile:

gem 'rack-slack_request_verification'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack-slack_request_verification

Inside your config.ru:

# Apply signed request verification to every path starting with "/slack/"
use Rack::SlackRequestVerification, path_pattern: %{^/slack/}
run MyApp

Will use a SLACK_SIGNING_SECRET environment variable by default.

You can override this with:

use Rack::SlackRequestVerification, path_pattern: %{^/slack/}, signing_secret: '...'

A 401 Not Authorized is returned in the following circumstances:

• When either or both of the X-Slack-Request-Timestamp or X-Slack-Signature headers are absent
• When the timestamp is more than five minutes old (to mitigate replay attacks)
• When the computed signature of the request does not match the X-Slack-Signature

A log message is also generated.

use Rack::SlackRequestVerification, {
    # A regular expression used to determine which requests to verify
    path_pattern: %r{^/slack/},

    # You can provide a signing secret directly, set a SLACK_SIGNING_SECRET
    # env var or customise the env var to something else
    signing_secret: nil,
    signing_secret_env_var: 'SLACK_SIGNING_SECRET',

    # Mitigates replay attacks by verifying the request was sent recently –
    # a better strategy is to record the signature header to ensure you only
    # process each request once
    max_staleness_in_secs: 60 * 5,

    # The entire request body must be loaded into memory to compute the hash.
    # To prevent a DDoS attack, the request body is limited to 1MB
    request_body_limit_in_bytes: 1024 ** 2,

    # Where to log error messages
    logger: Logger.new($stdout),

    # Settings as currently in use by Slack
    signing_version: 'v0',
    timestamp_header: 'X-Slack-Request-Timestamp',
    signature_header: 'X-Slack-Signature'
}

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/Aupajo/rack-slack_request_verification. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the Rack::SlackRequestVerification project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.