mirror of
https://github.com/mjl-/mox.git
synced 2024-12-25 16:03:48 +03:00
daa908e9f4
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.
37 lines
1 KiB
Go
37 lines
1 KiB
Go
package smtpserver
|
|
|
|
import (
|
|
"context"
|
|
"net"
|
|
|
|
"github.com/mjl-/mox/dns"
|
|
)
|
|
|
|
// checks if domain can accept email.
|
|
// i.e. if it has no null mx record, regular mx records or resolve to an address.
|
|
func checkMXRecords(ctx context.Context, resolver dns.Resolver, d dns.Domain) (bool, error) {
|
|
// Note: LookupMX can return an error and still return records.
|
|
mx, _, err := resolver.LookupMX(ctx, d.ASCII+".")
|
|
if err == nil && len(mx) == 1 && mx[0].Host == "." {
|
|
// Null MX record, explicit signal that remote does not accept email.
|
|
return false, nil
|
|
}
|
|
// Treat all errors that are not "no mx record" as temporary. E.g. timeout, malformed record, remote server error.
|
|
if err != nil && !dns.IsNotFound(err) {
|
|
return false, err
|
|
}
|
|
if len(mx) == 0 {
|
|
mx = []*net.MX{{Host: d.ASCII + "."}}
|
|
}
|
|
var lastErr error
|
|
for _, x := range mx {
|
|
ips, _, err := resolver.LookupIPAddr(ctx, x.Host)
|
|
if len(ips) > 0 {
|
|
return true, nil
|
|
}
|
|
if err != nil && !dns.IsNotFound(err) {
|
|
lastErr = err
|
|
}
|
|
}
|
|
return false, lastErr
|
|
}
|