discourse/lib/discourse_connect_provider.rb

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# frozen_string_literal: true
class DiscourseConnectProvider < DiscourseConnectBase
class BlankSecret < RuntimeError
end
FEATURE: Add 2FA support to the Discourse Connect Provider protocol (#16386) Discourse has the Discourse Connect Provider protocol that makes it possible to use a Discourse instance as an identity provider for external sites. As a natural extension to this protocol, this PR adds a new feature that makes it possible to use Discourse as a 2FA provider as well as an identity provider. The rationale for this change is that it's very difficult to implement 2FA support in a website and if you have multiple websites that need to have 2FA, it's unrealistic to build and maintain a separate 2FA implementation for each one. But with this change, you can piggyback on Discourse to take care of all the 2FA details for you for as many sites as you wish. To use Discourse as a 2FA provider, you'll need to follow this guide: https://meta.discourse.org/t/-/32974. It walks you through what you need to implement on your end/site and how to configure your Discourse instance. Once you're done, there is only one additional thing you need to do which is to include `require_2fa=true` in the payload that you send to Discourse. When Discourse sees `require_2fa=true`, it'll prompt the user to confirm their 2FA using whatever methods they've enabled (TOTP or security keys), and once they confirm they'll be redirected back to the return URL you've configured and the payload will contain `confirmed_2fa=true`. If the user has no 2FA methods enabled however, the payload will not contain `confirmed_2fa`, but it will contain `no_2fa_methods=true`. You'll need to be careful to re-run all the security checks and ensure the user can still access the resource on your site after they return from Discourse. This is very important because there's nothing that guarantees the user that will come back from Discourse after they confirm 2FA is the same user that you've redirected to Discourse. Internal ticket: t62183.
2022-04-13 08:04:09 -04:00
class BlankReturnUrl < RuntimeError
end
def self.parse(payload, sso_secret = nil, **init_kwargs)
parsed_payload = Rack::Utils.parse_query(payload)
return_sso_url = lookup_return_sso_url(parsed_payload)
raise ParseError if !return_sso_url
sso_secret ||= lookup_sso_secret(return_sso_url, parsed_payload)
if sso_secret.blank?
begin
host = URI.parse(return_sso_url).host
Rails.logger.warn(
"SSO failed; website #{host} is not in the `discourse_connect_provider_secrets` site settings",
)
rescue StandardError => e
# going for StandardError cause URI::Error may not be enough, eg it parses to something not
# responding to host
Discourse.warn_exception(
e,
message: "SSO failed; invalid or missing return_sso_url in SSO payload",
)
end
raise BlankSecret
end
super(payload, sso_secret, **init_kwargs)
end
def self.lookup_return_sso_url(parsed_payload)
decoded = Base64.decode64(parsed_payload["sso"])
decoded_hash = Rack::Utils.parse_query(decoded)
decoded_hash["return_sso_url"]
end
def self.lookup_sso_secret(return_sso_url, parsed_payload)
return nil unless return_sso_url && SiteSetting.enable_discourse_connect_provider
return_url_host = URI.parse(return_sso_url).host
provider_secrets =
SiteSetting
.discourse_connect_provider_secrets
.split("\n")
.map { |row| row.split("|", 2) }
.sort_by { |k, _| k }
.reverse
first_domain_match = nil
pair =
provider_secrets.find do |domain, configured_secret|
if WildcardDomainChecker.check_domain(domain, return_url_host)
first_domain_match ||= configured_secret
sign(parsed_payload["sso"], configured_secret) == parsed_payload["sig"]
end
end
# falls back to a secret which will fail to validate in DiscourseConnectBase
# this ensures error flow is correct
pair.present? ? pair[1] : first_domain_match
end
end