Self-service credentials, the About page and Files all keyed off
`urn:stalwart:jmap`, and all three looked for it in the session-level
`capabilities`. Stalwart has never put it there. `Session::new` builds that
list from a fixed set the capability is not part of, in any 0.16.x from
0.16.0 to 0.16.19; it is handed out per-account instead, so it arrives in
`primaryAccounts` and in each account's `accountCapabilities`.
So every real 0.16 server read as pre-0.16. Password changes, 2FA and app
passwords fell back to `POST /api/account/auth`, which 0.16 removed, and
reported that the server offers no self-service credential management. About
named the wrong generation. Files ran the pre-0.16 path, omitting `nodeType`
and listing the tree through get.
Look in all three places, on both sides. Two nearby soft spots go with it: a
transport error while probing the registry no longer downgrades a server to
the legacy path -- which would have posted the current password to an
endpoint that is not there -- and a locale request that is merely refused no
longer discards a generation the capability had already settled.
The mock advertised the capability in the session, which is why no test ever
caught this; it now advertises it where the real server does, and validates
`using` by the urn rather than by the session, as Stalwart does. Put the old
lookup back and nine tests fail.
Stalwart still publishes no version number to clients -- VERSION_PUBLIC is a
fixed "1.0.0" -- so About continues to report the generation and edition,
which are now the right ones.
**The login rate limiter could be sidestepped.** X-Forwarded-For is a list each
hop appends to, and nginx's $proxy_add_x_forwarded_for appends ours — so a
client sending "X-Forwarded-For: 1.2.3.4" arrives as "1.2.3.4, <their real
address>". Reading the leftmost entry, as we did, handed the caller a
rate-limit key they could change per request: unlimited password guessing
against a deployment that looks correctly configured. Read from the right
instead, skip hops that are themselves trusted proxies, and believe the header
only when the peer is one (loopback and the private ranges by default,
TRUSTED_PROXIES to be explicit).
**The upload cap was a suggestion.** It read content-length, which a chunked
request simply omits. Count the bytes through a stream, as the image proxy
already does.
**App password secrets were drawn with a modulo.** 256 is not a multiple of 33,
so the first 25 characters of the alphabet came up on 8 byte values and the
last 8 on only 7. Rejection sampling instead. The test weighs the whole tail of
the alphabet rather than single characters, because a 7/8 skew is invisible
per character against the noise — and it does fail when the bias is put back.
**Upstream headers were relayed wholesale.** Anything the mail server set —
cookies, auth challenges, CORS grants — landed on our origin, where it means
something else. Allowlist what is actually wanted.
Stalwart before 0.16 does not know urn:stalwart:jmap, and rejects the whole
request rather than the one call when `using` names a capability it cannot
parse. The probe is only sent when the session advertises that capability, so
this should not arise — but if it ever does, throwing turns a server we can
still manage credentials on into a Security page that only shows an error.
Fall through to the endpoint those servers do have.
Settings › Security grows three working sections instead of a note telling
people to use Stalwart's own portal.
Stalwart moved this API between releases, so ihasmail speaks both: 0.16+ has
the x:AccountPassword singleton and x:AppPassword registry objects over JMAP,
while 0.15.x has the /api/account/auth REST endpoint. Which one answers the
probe is the only reliable way to tell them apart, and the result is cached
per session. The built-in `user` role already grants sysAccountPassword* and
sysAppPassword*, so no administrator setup is needed.
Two problems are worth calling out, because both would bite a user hard:
Stalwart validates the credentials already on the account when 2FA is turned
on and never checks the new secret, so an authenticator that was mistyped or
out of step would lock someone out of their mailbox at the next sign-in. We
verify a code against the new secret ourselves first (RFC 6238, tested against
the spec's vectors) and only then ask the server to store anything.
Every proxied call re-authenticates with the credential sealed into the
session, and from the moment 2FA is on Stalwart wants a fresh TOTP code with
it — which we cannot produce between requests. Turning 2FA on would therefore
sign the user out of the browser they just turned it on in. App passwords
authenticate without a second factor, so the session is moved onto one minted
for this browser, and the session cookie is re-sealed with it. The order
matters: it is minted while the old credential still works, and revoked again
if enabling then fails.
Password changes re-seal this session too and drop the others, whose sealed
copies of the old password would fail on their next call.
The mock now enforces what a real server does — current password, password
policy, a TOTP code on every request once 2FA is on, app passwords exempt —
so the whole flow is exercised in tests rather than only by hand.
jcoffey-dev