if admin has disabled mta-sts for a domain, we still check for records &
policies, but won't mark it as error when they don't exist. we do now keep
warning that mta-sts isn't enabled, otherwise we would start showing a green
"ok".
this also fixes the mta-sts code returning ErrNoPolicy when mtasts.<domain>
doesn't exist. the dns lookup is done with the reguler "net" package dns lookup
code, not through adns, so we look for two types of DNSError's.
noticed a while ago when testing with MTA-STS while debugging TLS connection
issues with MS.
both when parsing our configs, and for incoming on smtp or in messages.
so we properly compare things like é and e+accent as equal, and accept the
different encodings of that same address.
- prometheus is now behind an interface, they aren't dependencies for the
reusable components anymore.
- some dependencies have been inverted: instead of packages importing a main
package to get configuration, the main package now sets configuration in
these packages. that means fewer internals are pulled in.
- some functions now have new parameters for values that were retrieved from
package "mox-".
we don't want external software to include internal details like mlog.
slog.Logger is/will be the standard.
we still have mlog for its helper functions, and its handler that logs in
concise logfmt used by mox.
packages that are not meant for reuse still pass around mlog.Log for
convenience.
we use golang.org/x/exp/slog because we also support the previous Go toolchain
version. with the next Go release, we'll switch to the builtin slog.
the underscores aren't valid, but have been seen in the wild, so we have a
workaround for them. there are limitations, it won't work with idna domains.
and if the domain has other policies, like mta-sts, the mx host won't pass
either.
after report from richard g about delivery issue, thanks!
because the txt would already follow cnames.
the additional cname lookup didn't hurt, it just didn't do anything.
i probably didn't realize that before looking deeper into dns.
the vendored dns resolver code is a copy of the go stdlib dns resolver, with
awareness of the "authentic data" (i.e. dnssec secure) added, as well as support
for enhanced dns errors, and looking up tlsa records (for dane). ideally it
would be upstreamed, but the chances seem slim.
dnssec-awareness is added to all packages, e.g. spf, dkim, dmarc, iprev. their
dnssec status is added to the Received message headers for incoming email.
but the main reason to add dnssec was for implementing dane. with dane, the
verification of tls certificates can be done through certificates/public keys
published in dns (in the tlsa records). this only makes sense (is trustworthy)
if those dns records can be verified to be authentic.
mox now applies dane to delivering messages over smtp. mox already implemented
mta-sts for webpki/pkix-verification of certificates against the (large) pool
of CA's, and still enforces those policies when present. but it now also checks
for dane records, and will verify those if present. if dane and mta-sts are
both absent, the regular opportunistic tls with starttls is still done. and the
fallback to plaintext is also still done.
mox also makes it easy to setup dane for incoming deliveries, so other servers
can deliver with dane tls certificate verification. the quickstart now
generates private keys that are used when requesting certificates with acme.
the private keys are pre-generated because they must be static and known during
setup, because their public keys must be published in tlsa records in dns.
autocert would generate private keys on its own, so had to be forked to add the
option to provide the private key when requesting a new certificate. hopefully
upstream will accept the change and we can drop the fork.
with this change, using the quickstart to setup a new mox instance, the checks
at internet.nl result in a 100% score, provided the domain is dnssec-signed and
the network doesn't have any issues.
it seems linux machines with systemd-resolved don't always set up
/etc/resolv.conf correctly. there may be no "nameserver" entry, causing Go's
net resolver to fallback to 127.0.0.1 and ::1. Systemd-resolved is listening on
127.0.0.53, so users will likely get a "connection refused". So point users to
the systemd-resolved manual page.
for issue #38 by ArnoSen
such deliveries would fail because a canceled "context" was reused, so the dns
lookups would fail.
the tests didn't catch it before because they ignored their context parameters.
the idea is to make it clear from the logging if non-ascii characters are used.
this is implemented by making mlog recognize if a field value that will be
logged has a LogString method. if so, that value is logged. dns.Domain,
smtp.Address, smtp.Localpart, smtp.Path now have a LogString method.
some explicit calls to String have been replaced to LogString, and some %q
formatting have been replaced with %s, because the escaped localpart would
already have double quotes, and double doublequotes aren't easy to read.
