discourse/lib/second_factor/auth_manager.rb
David Taylor 1bfccdd4f2
DEV: Allow run_second_factor! to be used before login ()
In a handful of situations, we need to verify a user's 2fa credentials before `current_user` is assigned. For example: login, email_login and change-email confirmation. This commit adds an explicit `target_user:` parameter to the centralized 2fa system so that it can be used for those situations.

For safety and clarity, this new parameter only works for anon. If some user is logged in, and target_user is set to a different user, an exception will be raised.
2024-01-29 12:28:47 +00:00

237 lines
9.0 KiB
Ruby

# frozen_string_literal: true
=begin
This class is responsible for managing any actions that require second factor
authentication before a user is allowed to perform them. Such actions include
granting another user admin access, changing password and signing in. In a more
technical sense, an action is the logic encapsulated in a Rails controller
action without the logic related to 2fa enforcement/handling.
When a user attempts to perform a 2fa-protected action, there are 3 possible
outcomes:
1. the user doesn't have any suitable 2fa methods enabled, so they should be
allowed to perform the action right away.
2. the user has a suitable 2fa method enabled, in which case there are 2
possibilities:
a. the user hasn't done 2fa for the action so they should be redirected to
the 2fa page and complete the 2fa before they are allowed to proceed.
b. the user has done 2fa for the action so they should be allowed to perform
the action.
This class, the auth manager, contains the logic for deciding which outcome
should happen and performing it.
To use the auth manager for requiring 2fa for an action, it needs to be invoked
from the controller action using the `run_second_factor!` method which is
available in all controllers. This method takes a single argument which is a
class that inherits from the `SecondFactor::Actions::Base` class and implements
at least the following methods:
1. no_second_factors_enabled!(params):
This method corresponds to outcome (1) above, i.e. it's called when the user
performing the action has no suitable 2fa method enabled. It receives the
request params of the controller action. Return value is insignificant.
2. second_factor_auth_required!(params):
This method corresponds to outcome (2a) above. It also receives the request
params of the controller action. The purpose of this method is to keep track
of the params that are needed to perform the action and where they should be
redirected after the user completes the 2fa.
To communicate this information to the auth manager, the return value of this
method is utilized for this purpose. This method must return a Hash that
should have 2 keys:
:callback_params => another Hash containing the params that are needed to
finish the action once 2fa is completed. Everything in this Hash must be
serializable to JSON.
:redirect_url => where the user should be redirected after they confirm 2fa.
A relative path (must be subfolder-aware) is a valid value for this key.
:description => optional action-specific description message that's shown on
the 2FA page.
After this method is called, the auth manager will send a 403 response with a
JSON body. It does that by raising an exception that's then rescued by a
`rescue_from` handler. The JSON response contains a challenge nonce which the
client/frontend will need to complete the 2fa. More on this later.
3. second_factor_auth_completed!(callback_params):
This method corresponds to outcome (2b) above. It's called after the user has
successfully completed the 2fa for the 2fa-protected action and the purpose
of this method is to actually perform that action.
The `callback_params` param of this method is the `callback_params` Hash from
the return value of the previous method.
There are 2 additionals methods in the base class that can be overridden, but
they're optional:
4. skip_second_factor_auth?(params):
This method returns false by default. As the name implies, this method can be
used to skip the 2FA for the action entirely. For example, if your action
deletes a user, then you may want to require 2FA only if the deleted user has
more than a specific number of posts. If you override this method in your
action, you must implement the following method as well.
5. second_factor_auth_skipped!(params):
This method is called when the `skip_second_factor_auth?` method above
returns true.
If there are permission/security checks that the current user must pass in
order to perform the 2fa-protected action, it's important to run the checks in
all of the 3 methods of the action class and raise errors if the user doesn't
pass the checks.
Rendering a response to the client in the outcomes (1) and (2b) is a task for
the controller action. The return value of the `run_second_factor!` method,
which is an instance of `SecondFactor::AuthManagerResult`, can be used to know
which outcome the auth manager has picked and render a different response based
on the outcome.
The results object also has a `data` method that returns the return value of
the hook/method of your action class. For example, if
`second_factor_auth_required!` is called and it returns a hash object, you can
get that hash object by calling the `data` method of the results object.
For a real example where the auth manager is used, please refer to:
* The `lib/second_factor/actions` directory where all existing actions live.
* `Admin::UsersController#grant_admin` controller action.
* `SessionController#sso_provider` controller action.
=end
class SecondFactor::AuthManager
MAX_CHALLENGE_AGE = 5.minutes
class SecondFactorRequired < StandardError
attr_reader :nonce
def initialize(nonce:)
@nonce = nonce
end
end
attr_reader :allowed_methods
def self.find_second_factor_challenge(nonce:, secure_session:, target_user:)
challenge_json = secure_session["current_second_factor_auth_challenge"]
if challenge_json.blank?
raise SecondFactor::BadChallenge.new(
"second_factor_auth.challenge_not_found",
status_code: 404,
)
end
challenge = JSON.parse(challenge_json).deep_symbolize_keys
if challenge[:nonce] != nonce
raise SecondFactor::BadChallenge.new(
"second_factor_auth.challenge_not_found",
status_code: 404,
)
end
if target_user && (challenge[:target_user_id] != target_user.id)
raise SecondFactor::BadChallenge.new(
"second_factor_auth.challenge_not_found",
status_code: 404,
)
end
generated_at = challenge[:generated_at]
if generated_at < MAX_CHALLENGE_AGE.ago.to_i
raise SecondFactor::BadChallenge.new("second_factor_auth.challenge_expired", status_code: 401)
end
challenge
end
def initialize(guardian, action, target_user:)
@guardian = guardian
@current_user = guardian.user
@target_user = target_user
@action = action
@allowed_methods =
Set.new([UserSecondFactor.methods[:totp], UserSecondFactor.methods[:security_key]]).freeze
end
def allow_backup_codes!
add_method(UserSecondFactor.methods[:backup_codes])
end
def run!(request, params, secure_session)
if nonce = params[:second_factor_nonce].presence
data = verify_second_factor_auth_completed(nonce, secure_session)
create_result(:second_factor_auth_completed, data)
elsif @action.skip_second_factor_auth?(params)
data = @action.second_factor_auth_skipped!(params)
create_result(:second_factor_auth_skipped, data)
elsif !allowed_methods.any? { |m| @target_user.valid_second_factor_method_for_user?(m) }
data = @action.no_second_factors_enabled!(params)
create_result(:no_second_factor, data)
else
nonce = initiate_second_factor_auth(params, secure_session, request)
raise SecondFactorRequired.new(nonce: nonce)
end
end
private
def initiate_second_factor_auth(params, secure_session, request)
config = @action.second_factor_auth_required!(params)
nonce = SecureRandom.alphanumeric(32)
callback_params = config[:callback_params] || {}
challenge = {
nonce: nonce,
callback_method: config[:callback_method] || request.request_method,
callback_path: config[:callback_path] || request.path,
callback_params: callback_params,
allowed_methods: allowed_methods.to_a,
generated_at: Time.zone.now.to_i,
target_user_id: @target_user.id,
}
challenge[:description] = config[:description] if config[:description]
challenge[:redirect_url] = config[:redirect_url] if config[:redirect_url].present?
secure_session["current_second_factor_auth_challenge"] = challenge.to_json
nonce
end
def verify_second_factor_auth_completed(nonce, secure_session)
challenge =
self.class.find_second_factor_challenge(
nonce: nonce,
secure_session: secure_session,
target_user: @target_user,
)
if !challenge[:successful]
raise SecondFactor::BadChallenge.new(
"second_factor_auth.challenge_not_completed",
status_code: 401,
)
end
secure_session["current_second_factor_auth_challenge"] = nil
callback_params = challenge[:callback_params]
data = @action.second_factor_auth_completed!(callback_params)
data
end
def add_method(id)
if !@allowed_methods.include?(id)
@allowed_methods = Set.new(@allowed_methods)
@allowed_methods.add(id)
@allowed_methods.freeze
end
end
def create_result(status, data = nil)
SecondFactor::AuthManagerResult.new(status, data)
end
end