If we fail to put the message in the queue (e.g. because we're out of
storage space, or the aliases-resolve hook errored out), it should be
considered a transient failure.
Currently we return a permanent error, which is misleading, as we want
clients to retry in these situations.
So this patch changes the error returned accordingly.
This patch implements two new hooks: alias-resolve and alias-exists.
They are called during the aliases resolution process, to allow for more
complex integration with other systems, such as storing the aliases in a
database.
See the included documentation for more details.
The spf library has gained support for macros, but to process them
properly, a new function needs to be called with the full sender
address, spf.CheckHostWithSender.
This patch updates chasquid's calls to the new API.
There are a few context.WithDeadline calls that can be simplified by
using context.WithTimeout.
At the time they were added, WithTimeout was too new so we didn't want
to depend on it. But now that the minimum Go version has been raised to
1.9, we can simplify the calls.
This patch does that simplification, which is purely mechanical, and
does not change the logic itself.
When handling a connection, today we only set a deadline after each
command received.
However, this does not cover our initial greeting, or the initial TLS
handshake (if the socket is TLS), so a connection can hang
indefininitely at that stage.
This patch fixes that by setting a deadline earlier, before we send or
receive anythong on the connection.
This patch contains some minor code style improvements, to leave the
linter happier and generally follow best practices in some areas where
things snuck through.
Despite its loose appearance, the "Received" header has a reasonably
standarized format.
We were not following the standard format as closely as we should; this
rarely causes problems in this particular case, but there's no need to
deviate from it.
This patch changes the Received header generation as follows:
- The "from" section now uses the remote address as canonical (for
non-authenticated users) which provides more valuable information
than the user-supplied EHLO address (which is also included).
- The remote authenticated user is now hidden, for additional privacy.
- Use the "with" optional clause.
- Use the standard way of printing TLS cipher suite.
- Use the standard way of printing address literals.
This patch makes chasquid reload domaininfo periodically, so it notices
any external changes made to it.
It is in line with what we do for aliases and authentication already,
and makes it possible for external removals an additions to the
domaininfo database to be picked up without a restart.
This patch adds a missing docstrings for exported identifiers, and
adjust some of the existing ones to match the standard style.
In some cases, the identifiers were un-exported after noticing they had
no external users.
Besides improving documentation, it also reduces the linter noise
significantly.
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.
For direct TLS connections, such as submission-over-TLS, we currently
don't get the TLS information so it appears in the headers as "plain
text", which is misleading.
This patch fixes the problem by getting the connection information
early. Note it explicitly triggers the handshake, which would otherwise
happen transparently on the first read/write, so we can use the hostname
(if any) in our hello message.
We have many places in our tests where we create temporary directories,
which we later remove (most of the time). We have at least 3 helpers to
do this, and various places where it's done ad-hoc (and the cleanup is
not always present).
To try to reduce the clutter, and make the tests more uniform and
readable, this patch introduces two helpers in a new "testutil" package:
one for creating and one for removing temporary directories.
These new functions are safer, better tested, and make the tests more
consistent. All the tests are updated to use them.
This patch adds support for TLS-wrapped submission connections.
Instead of clients establishing a connection over plain text and then
using STARTTLS to switch over a TLS connection, this new mode allows the
clients to connect directly over TLS, like it's done in HTTPS.
This is not an official standard yet, but it's reasonably common in
practice, and provides some advantages over the traditional submission
port.
The default port is 465, commonly used for this; chasquid defaults to
systemd file descriptor passing as for the other protocols (for now).
The server is written assuming there's at least one valid SSL/TLS
certificate. For example, it unconditionally advertises STARTTLS, and
only supports AUTH over TLS.
This patch makes the server fail to listen if there are no certificates
configured, so the users don't accidentally run an unsupported
configuration.
When testing, we don't want the server to do SPF lookups, as those cause
real DNS queries which can be problematic and add a dependency on the
environment.
This patch adds an internal boolean to disable the SPF lookups, which is
only set from the tests.
Picking the domain used in the DSN message "From" header is more
complicated than it needs to be, causing confusing code paths and having
different uses for the hostname, which should be purely aesthetic.
This patch makes the queue pick the DSN "From" domain from the message
itself, by looking for a local domain in either the sender or the
original recipients. We should find at least one, otherwise it'd be
relaying.
This allows the code to be simplified, and we can narrow the scope of
the hostname option even further.
The loop test can be quite slow, specially on computers without
cryptography-friendly instructions.
This patch introduces a new flag for testing, so that we can bring the
threshold down to 5. The test is just as useful but now runs in a few
seconds, as opposed to a few minutes.
glog works fine and has great features, but it does not play along well
with systemd or standard log rotators (as it does the rotation itself).
So this patch replaces glog with a new logging module "log", which by
default logs to stderr, in a systemd-friendly manner.
Logging to files or syslog is still supported.
This patch makes the hooks always have a complete set of environment
varuables, set to 0/1 or whatever is appropriate, to make it easier to
write the checks for them.
It is can be convenient for hooks to indicate that an error is
permanent; for example if the anti-virus found something.
This patch makes it so that if the hook exits with code 20, then it's
considered permanent. Otherwise it is considered transient, to help
prevent accidental errors cause final delivery issues.
The default INFO logs are more oriented towards debugging and can be
a bit too verbose when looking for high-level information.
This patch introduces a new "maillog" package, used to log messages of
particular relevance to mail transmission at a higher level.
This patch implements a post-DATA hook, which is run after receiving the
data but before sending a reply.
It can be used to implement content filtering when receiving email, for
example for passing the email through an anti-spam or an anti-virus.
Unknown commands can fill the logs, traces and expvars with a lot of
noise; this patch sanitizes them a bit down to 6 bytes, as a compromise
to maintain some information for troubleshooting.
The submission port is expected to be used only by authenticated
clients, so this patch makes chasquid enforce this, which also helps
to reduce spam.
https://www.rfc-editor.org/rfc/rfc6409.txt
Today, we pick the domain used to send the DSN from based on what we
presented to the client at EHLO time, which itself may be based on the
TLS negotiation (which is not necessarily trusted).
This is complex, not necessarily correct, and involves passing the
domain around through the queue and persisting it in the items.
So this patch simplifies that handling by always using the main domain
as specified by the configuration.
This patch moves chasquid's Server and Conn structures to their own
smtpsrv package, to make chasquid.go a bit more readable. It also helps
clarify the relation between Server and Conn.
There are no functional changes.
Note that git can still track the history across this commit (e.g. git
gui blame shows the right data).
