This is an extract from PR #9175, which can be reviewed in isolation to
reduce the volume of changes to review all at once in #9175. There are
about to be several services and API handlers that read and set cookies
and session state, so this abstraction will prove helpful.
In particular a motivating cause for this is that with the current
architecture in PR #9175, in `api.go` the [`webauthnService` needs to
access the
session](https://github.com/syncthing/syncthing/pull/9175/files#diff-e2e14f22d818b8e635572ef0ee7718dee875c365e07225d760a6faae8be7772dR309-R310)
for authentication purposes but needs to be instantiated before the
`configMuxBuilder` for config purposes, because the WebAuthn additions
to config management need to perform WebAuthn registration ceremonies,
but currently the session management is embedded in the
`basicAuthAndSessionMiddleware` which is [instantiated much
later](https://github.com/syncthing/syncthing/pull/9175/files#diff-e2e14f22d818b8e635572ef0ee7718dee875c365e07225d760a6faae8be7772dL371-R380)
and only if authentication is enabled in `guiCfg`. This refactorization
extracts the session management out from `basicAuthAndSessionMiddleware`
so that `basicAuthAndSessionMiddleware` and `webauthnService` can both
use the same shared session management service to perform session
management logic.
### Testing
This is a refactorization intended to not change any externally
observable behaviour, so existing tests (e.g., `api_auth_test.go`)
should cover this where appropriate. I have manually verified that:
- Appending `+ "foo"` to the cookie name in `createSession` causes
`TestHtmlFormLogin/invalid_URL_returns_403_before_auth_and_404_after_auth`
and `TestHtmlFormLogin/UTF-8_auth_works` to fail
- Inverting the return value of `hasValidSession` cases a whole bunch of
tests in `TestHTTPLogin` and `TestHtmlFormLogin` to fail
- (Fixed) Changing the cookie to `MaxAge: 1000` in `destroySession` does
NOT cause any tests to fail!
- Added tests `TestHtmlFormLogin/Logout_removes_the_session_cookie`,
`TestHTTPLogin/*/Logout_removes_the_session_cookie`,
`TestHtmlFormLogin/Session_cookie_is_invalid_after_logout` and
`TestHTTPLogin/200_path#01/Session_cookie_is_invalid_after_logout` to
cover this.
- Manually verified that these tests pass both before and after the
changes in this PR, and that changing the cookie to `MaxAge: 1000` or
not calling `m.tokens.Delete(cookie.Value)` in `destroySession` makes
the respective pair of tests fail.
This adds a "token manager" which handles storing and checking expired
tokens, used for both sessions and CSRF tokens. It removes the old,
corresponding functionality for CSRFs which saved things in a file. The
result is less crap in the state directory, and active login sessions
now survive a Syncthing restart (this really annoyed me).
It also adds a boolean on login to create a longer-lived session cookie,
which is now possible and useful. Thus we can remain logged in over
browser restarts, which was also annoying... :)
<img width="1001" alt="Screenshot 2023-12-12 at 09 56 34"
src="https://github.com/syncthing/syncthing/assets/125426/55cb20c8-78fc-453e-825d-655b94c8623b">
Best viewed with whitespace-insensitive diff, as a bunch of the auth
functions became methods instead of closures which changed indentation.
