Domains in addresses had very lax validation, which allowed them to
include characters like "/".
That could be exploited to trigger a daemon panic: a MAIL FROM
"x@evil/foo" could be accepted and, on failed delivery, a DSN queued.
Attempting to deliver the DSN would cause an MTA-STS cache lookup, which
would panic because the domain includes a "/" and crash the server.
Because the DSN would be queued, the server would crash again on
restarts, and only self-recover after give_up_send_after (20h by
default).
To fix this, we now explicitly validate the domain when normalizing it,
make MTA-STS cache not panic on invalid domains, and also make the SMTP
courier fail permanently on invalid domains.
Thanks to John JEAN <john@wargan.com> for finding and reporting this
problem. The detailed report can be found in
https://johnjean.io/advisories/chasquid-unauthenticated-remote-dos/.
Many of our tests rely on helpers that predate features which are now
available in the standard library.
This patch replaces them with the standard equivalents:
- MustTempDir/RemoveIfOk -> t.ArtifactDir() or t.TempDir() (depending on
whether it is useful to keep the data on request).
- GetFreePort + waitForServer -> opening the listeners before starting
the servers. To support this, localrpc.Server gains a Serve method. We
may re-introduce these in the future if more use cases appear.
- WaitFor and real-time timing checks -> testing/synctest.
- context.Background() -> t.Context().
- Benchmark b.N loops -> b.Loop().
- reflect.DeepEqual -> cmp.Diff, and proto.Equal for protobufs.
This patch changes several internal packages to receive and pass tracing
annotations, making use of the new tracing library, so we can have
better debugging information.
Some deployments already have users that authenticate without a domain.
Today, we refuse to even consider those, and reject them at parsing time.
However, it is a use-case worth supporting, at least with some
restrictions that make the complexity manageable.
This patch changes the auth package to support authenticating users
without an "@domain" part.
Those requests will always be directly passed on to the fallback
authenticator, if available.
The dovecot fallback authenticator can already handle this case just fine.
This patch adds a new package which implements two basic primitives for
authenticating against dovecot ("user exists", and "check password").
It is still experimental/work in progress.
This patch implements an Authenticator type, which connections use to
do authentication and user existence checks.
It simplifies the abstractions (the server doesn't need to know about
userdb, or keep track of domain-userdb maps), and lays the foundation
for other types of authentication backends which will come in later
patches.
This patch implements the AUTH SMTP command, using per-domain user databases.
Note that we don't really use or check the validation for anything, this is
just implementing the command itself.
Alberto Bertogli