Fix three exploits that allowed one to keep using their account after it was deleted:
* It was possible to use session cookies from another computer to login after you deleted your account.
* It was possible to use API keys to make API requests after you deleted your account.
* It was possible to request a password reset, delete your account, then use the password reset link
to change your password and login to your deleted account.
Add tracking of certain important user actions. These events include:
* Logins
* Logouts
* Failed login attempts
* Account creations
* Account deletions
* Password reset requests
* Password changes
* Email address changes
This is similar to the mod actions log, except for account activity
related to a single user.
The information tracked includes the user, the event type (login,
logout, etc), the timestamp, the user's IP address, IP geolocation
information, the user's browser user agent, and the user's session ID
from their session cookie. This information is visible to mods only.
This is done with three models. The UserEvent model tracks the event
type (login, logout, password change, etc) and the user. The UserEvent
is tied to a UserSession, which contains the user's IP address and
browser metadata. Finally, the IpGeolocation model contains the
geolocation information for IPs, including the city, country, ISP, and
whether the IP is a proxy.
This tracking will be used for a few purposes:
* Letting users view their account history, to detect things like logins
from unrecognized IPs, failed logins attempts, password changes, etc.
* Rate limiting failed login attempts.
* Detecting sockpuppet accounts using their login history.
* Detecting unauthorized account sharing.
* Make authentication methods into User instance methods instead of
class methods.
* Fix API key authentication to use a secure string comparison. Fixes a
hypothetical (unlikely to be exploitable) timing attack.
* Move login logic from SessionCreator to SessionLoader.
Pull the password reauthentication logic out of the user model and put
it in the password update controller where it belongs.
This fixes an issue where when a new user was created the user model had
an incorrect password error set on it by `encrypt_password_on_update`.
It was trying to verify the old password even though we don't have one
when creating a new user. This error caused the user create action to
redirect back to the signup page because `respond_with` thought that
creating the user failed.
* Fix users being redirected back to the change password page after
successfully changing their password.
* Move passwords controller out of /maintenance/ namespace.
* Add tests.
