3 Commits

Author	SHA1	Message	Date
Mechiel Lukkien	893a6f8911	implement outgoing tls reports ... we were already accepting, processing and displaying incoming tls reports. now we start tracking TLS connection and security-policy-related errors for outgoing message deliveries as well. we send reports once a day, to the reporting addresses specified in TLSRPT records (rua) of a policy domain. these reports are about MTA-STS policies and/or DANE policies, and about STARTTLS-related failures. sending reports is enabled by default, but can be disabled through setting NoOutgoingTLSReports in mox.conf. only at the end of the implementation process came the realization that the TLSRPT policy domain for DANE (MX) hosts are separate from the TLSRPT policy for the recipient domain, and that MTA-STS and DANE TLS/policy results are typically delivered in separate reports. so MX hosts need their own TLSRPT policies. config for the per-host TLSRPT policy should be added to mox.conf for existing installs, in field HostTLSRPT. it is automatically configured by quickstart for new installs. with a HostTLSRPT config, the "dns records" and "dns check" admin pages now suggest the per-host TLSRPT record. by creating that record, you're requesting TLS reports about your MX host. gathering all the TLS/policy results is somewhat tricky. the tentacles go throughout the code. the positive result is that the TLS/policy-related code had to be cleaned up a bit. for example, the smtpclient TLS modes now reflect reality better, with independent settings about whether PKIX and/or DANE verification has to be done, and/or whether verification errors have to be ignored (e.g. for tls-required: no header). also, cached mtasts policies of mode "none" are now cleaned up once the MTA-STS DNS record goes away.	2023-11-09 19:47:26 +01:00
Mechiel Lukkien	28fae96a9b	make mox compile on windows, without "mox serve" but with working "mox localserve" ... getting mox to compile required changing code in only a few places where package "syscall" was used: for accessing file access times and for umask handling. an open problem is how to start a process as an unprivileged user on windows. that's why "mox serve" isn't implemented yet. and just finding a way to implement it now may not be good enough in the near future: we may want to starting using a more complete privilege separation approach, with a process handling sensitive tasks (handling private keys, authentication), where we may want to pass file descriptors between processes. how would that work on windows? anyway, getting mox to compile for windows doesn't mean it works properly on windows. the largest issue: mox would normally open a file, rename or remove it, and finally close it. this happens during message delivery. that doesn't work on windows, the rename/remove would fail because the file is still open. so this commit swaps many "remove" and "close" calls. renames are a longer story: message delivery had two ways to deliver: with "consuming" the (temporary) message file (which would rename it to its final destination), and without consuming (by hardlinking the file, falling back to copying). the last delivery to a recipient of a message (and the only one in the common case of a single recipient) would consume the message, and the earlier recipients would not. during delivery, the already open message file was used, to parse the message. we still want to use that open message file, and the caller now stays responsible for closing it, but we no longer try to rename (consume) the file. we always hardlink (or copy) during delivery (this works on windows), and the caller is responsible for closing and removing (in that order) the original temporary file. this does cost one syscall more. but it makes the delivery code (responsibilities) a bit simpler. there is one more obvious issue: the file system path separator. mox already used the "filepath" package to join paths in many places, but not everywhere. and it still used strings with slashes for local file access. with this commit, the code now uses filepath.FromSlash for path strings with slashes, uses "filepath" in a few more places where it previously didn't. also switches from "filepath" to regular "path" package when handling mailbox names in a few places, because those always use forward slashes, regardless of local file system conventions. windows can handle forward slashes when opening files, so test code that passes path strings with forward slashes straight to go stdlib file i/o functions are left unchanged to reduce code churn. the regular non-test code, or test code that uses path strings in places other than standard i/o functions, does have the paths converted for consistent paths (otherwise we would end up with paths with mixed forward/backward slashes in log messages). windows cannot dup a listening socket. for "mox localserve", it isn't important, and we can work around the issue. the current approach for "mox serve" (forking a process and passing file descriptors of listening sockets on "privileged" ports) won't work on windows. perhaps it isn't needed on windows, and any user can listen on "privileged" ports? that would be welcome. on windows, os.Open cannot open a directory, so we cannot call Sync on it after message delivery. a cursory internet search indicates that directories cannot be synced on windows. the story is probably much more nuanced than that, with long deep technical details/discussions/disagreement/confusion, like on unix. for "mox localserve" we can get away with making syncdir a no-op.	2023-10-14 10:54:07 +02:00
Mechiel Lukkien	daa908e9f4	implement dnssec-awareness throughout code, and dane for incoming/outgoing mail delivery ... 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.	2023-10-10 12:09:35 +02:00