Before this change, the authorize hook was invoked twice: once before
authentication and again after (if settings.requireAuthorization is
true). Now pre-authentication authorization is instead handled by a
new preAuthorize hook, and the authorize hook is only invoked after
the user has authenticated.
Rationale: Without this change it is too easy to write an
authorization plugin that is too permissive. Specifically:
* If the plugin does not check the path for /admin then a non-admin
user might be able to access /admin pages.
* If the plugin assumes that the user has already been authenticated
by the time the authorize function is called then unauthenticated
users might be able to gain access to restricted resources.
This change also avoids calling the plugin's authorize function twice
per access, which makes it easier for plugin authors to write an
authorization plugin that is easy to understand.
This change may break existing authorization plugins: After this
change, the authorize hook will no longer be able to authorize
non-admin access to /admin pages. This is intentional. Access to admin
pages should instead be controlled via the `is_admin` user setting,
which can be set in the config file or by an authentication plugin.
Also:
* Add tests for the authenticate and authorize hooks.
* Disable the authentication failure delay when testing.
This loses some of the granularity of the default HTTP basic auth
(unknown username vs. bad password), but there is considerable value
in having logging that is consistent no matter what authentication
plugins are installed.
This makes it possible for reverse proxies to transform 403 errors
into something like "upgrade to a premium account to access this
pad".
Also add some webaccess tests.
Before, a malicious user could bypass authorization restrictions
imposed by the authorize hook:
* Step 1: Fetch any resource that the malicious user is authorized to
access (e.g., static content).
* Step 2: Use the signed express_sid cookie generated in step 1 to
create a socket.io connection.
* Step 3: Perform the CLIENT_READY handshake for the desired pad.
* Step 4: Profit!
Now the authorization decision made by the authorize hook is
propagated to SecurityManager so that it can approve or reject
socket.io messages as appropriate.
This also sets up future support for per-user read-only and
modify-only (no create) authorization levels.
Authentication plugins almost always want to read and modify
`settings.users`. The settings can already be accessed in a few other
ways, but this is much more convenient.
The authorization logic determines whether the user has already
successfully authenticated by looking to see if `req.session.user`
exists. If an authentication plugin says that it successfully
authenticated the user but it did not create `req.session.user` then
authentication will re-run for every access, and authorization plugins
will be unable to determine whether the user has been authenticated.
Return a 500 internal server error to prevent these problems.
Not all authentication plugins require the Authorization header, so it
might not be present in subsequent attempts. (In particular, a reverse
proxy might strip it.)
* Improve the comment describing how the access check works.
* Move the `authenticate` logic to where it is used so that people
don't have to keep jumping back and forth to understand how the
access check works.
* Break up the three steps to reduce the number of indentation
levels and improve readability. This should also make it easier to
implement and review planned future changes.
The mechanism used for determining if the application is being served over SSL
is wrapped by the "express-session" library for "express_sid", and manual for
the "language" cookie, but it's very similar in both cases.
The "secure" flag is set if one of these is true:
1. we are directly serving Etherpad over SSL using the native nodejs
functionality, via the "ssl" options in settings.json
2. Etherpad is being served in plaintext by nodejs, but we are using a reverse
proxy for terminating the SSL for us;
In this case, the user has to be instructed to properly set trustProxy: true
in settings.json, and the information wheter the application is over SSL or
not will be extracted from the X-Forwarded-Proto HTTP header.
Please note that this will not be compatible with applications being served over
http and https at the same time.
The change on webaccess.js amends 009b61b338, which did not work when the SSL
termination was performed by a reverse proxy.
Reference for automatic "express_sid" configuration:
https://github.com/expressjs/session/blob/v1.17.0/README.md#cookiesecureCloses#3561.
