expose fewer internals in packages, for easier software reuse

- 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-".

dsn/dsn.go

@@ -5,7 +5,6 @@ package dsn
 import (
 	"bufio"
 	"bytes"
-	"context"
 	"encoding/base64"
 	"errors"
 	"fmt"
@@ -16,13 +15,8 @@ import (
 	"strings"
 	"time"
 
-	"golang.org/x/exp/slog"
-
-	"github.com/mjl-/mox/dkim"
-	"github.com/mjl-/mox/dns"
 	"github.com/mjl-/mox/message"
 	"github.com/mjl-/mox/mlog"
-	"github.com/mjl-/mox/mox-"
 	"github.com/mjl-/mox/smtp"
 )
 
@@ -48,7 +42,6 @@ type Message struct {
 	// Message subject header, e.g. describing mail delivery failure.
 	Subject string
 
-	// Set when message is composed.
 	MessageID string
 
 	// References header, with Message-ID of original message this DSN is about. So
@@ -136,7 +129,7 @@ type Recipient struct {
 // supports smtputf8. This influences the message media (sub)types used for the
 // DSN.
 //
-// DKIM signatures are added if DKIM signing is configured for the "from" domain.
+// Called may want to add DKIM-Signature headers.
 func (m *Message) Compose(log mlog.Log, smtputf8 bool) ([]byte, error) {
 	// ../rfc/3462:119
 	// ../rfc/3464:377
@@ -168,7 +161,9 @@ func (m *Message) Compose(log mlog.Log, smtputf8 bool) ([]byte, error) {
 	header("From", fmt.Sprintf("<%s>", m.From.XString(smtputf8))) // todo: would be good to have a local ascii-only name for this address.
 	header("To", fmt.Sprintf("<%s>", m.To.XString(smtputf8)))     // todo: we could just leave this out if it has utf-8 and remote does not support utf-8.
 	header("Subject", m.Subject)
-	m.MessageID = mox.MessageIDGen(smtputf8)
+	if m.MessageID == "" {
+		return nil, fmt.Errorf("missing message-id")
+	}
 	header("Message-Id", fmt.Sprintf("<%s>", m.MessageID))
 	if m.References != "" {
 		header("References", m.References)
@@ -367,31 +362,6 @@ func (m *Message) Compose(log mlog.Log, smtputf8 bool) ([]byte, error) {
 	}
 
 	data := msgw.w.Bytes()
-
-	// Add DKIM signature for domain, even if higher up than the full mail hostname.
-	// This helps with an assumed (because default) relaxed DKIM policy. If the DMARC
-	// policy happens to be strict, the signature won't help, but won't hurt either.
-	fd := m.From.IPDomain.Domain
-	var zerodom dns.Domain
-	for fd != zerodom {
-		confDom, ok := mox.Conf.Domain(fd)
-		if !ok {
-			var nfd dns.Domain
-			_, nfd.ASCII, _ = strings.Cut(fd.ASCII, ".")
-			_, nfd.Unicode, _ = strings.Cut(fd.Unicode, ".")
-			fd = nfd
-			continue
-		}
-
-		dkimHeaders, err := dkim.Sign(context.Background(), log.Logger, m.From.Localpart, fd, confDom.DKIM, smtputf8, bytes.NewReader(data))
-		if err != nil {
-			log.Errorx("dsn: dkim sign for domain, returning unsigned dsn", err, slog.Any("domain", fd))
-		} else {
-			data = append([]byte(dkimHeaders), data...)
-		}
-		break
-	}
-
 	return data, nil
 }
 

dsn/dsn_test.go

@@ -2,21 +2,17 @@ package dsn
 
 import (
 	"bytes"
-	"context"
 	"fmt"
 	"io"
 	"net"
-	"path/filepath"
 	"reflect"
 	"strings"
 	"testing"
 	"time"
 
-	"github.com/mjl-/mox/dkim"
 	"github.com/mjl-/mox/dns"
 	"github.com/mjl-/mox/message"
 	"github.com/mjl-/mox/mlog"
-	"github.com/mjl-/mox/mox-"
 	"github.com/mjl-/mox/smtp"
 )
 
@@ -83,10 +79,11 @@ func TestDSN(t *testing.T) {
 	m := Message{
 		SMTPUTF8: false,
 
-		From:     smtp.Path{Localpart: "postmaster", IPDomain: xparseIPDomain("mox.example")},
-		To:       smtp.Path{Localpart: "mjl", IPDomain: xparseIPDomain("remote.example")},
-		Subject:  "dsn",
-		TextBody: "delivery failure\n",
+		From:      smtp.Path{Localpart: "postmaster", IPDomain: xparseIPDomain("mox.example")},
+		To:        smtp.Path{Localpart: "mjl", IPDomain: xparseIPDomain("remote.example")},
+		Subject:   "dsn",
+		MessageID: "test@localhost",
+		TextBody:  "delivery failure\n",
 
 		ReportingMTA:    "mox.example",
 		ReceivedFromMTA: smtp.Ehlo{Name: xparseIPDomain("relay.example"), ConnIP: net.ParseIP("10.10.10.10")},
@@ -107,6 +104,7 @@ func TestDSN(t *testing.T) {
 	if err != nil {
 		t.Fatalf("composing dsn: %v", err)
 	}
+
 	pmsg, part := tparseMessage(t, msgbuf, 3)
 	tcheckType(t, part, "multipart", "report", "")
 	tcheckType(t, &part.Parts[0], "text", "plain", "7bit")
@@ -130,35 +128,15 @@ func TestDSN(t *testing.T) {
 	tcompareReader(t, part.Parts[2].Reader(), m.Original)
 	tcompare(t, pmsg.Recipients[0].FinalRecipient, m.Recipients[0].FinalRecipient)
 
-	// Test for valid DKIM signature.
-	mox.Context = context.Background()
-	mox.ConfigStaticPath = filepath.FromSlash("../testdata/dsn/mox.conf")
-	mox.MustLoadConfig(true, false)
-	msgbuf, err = m.Compose(log, false)
-	if err != nil {
-		t.Fatalf("composing utf-8 dsn with utf-8 support: %v", err)
-	}
-	resolver := &dns.MockResolver{
-		TXT: map[string][]string{
-			"testsel._domainkey.mox.example.": {"v=DKIM1;h=sha256;t=s;p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3ZId3ys70VFspp/VMFaxMOrNjHNPg04NOE1iShih16b3Ex7hHBOgC1UvTGSmrMlbCB1OxTXkvf6jW6S4oYRnZYVNygH6zKUwYYhaSaGIg1xA/fDn+IgcTRyLoXizMUgUgpTGyxhNrwIIWv+i7jjbs3TKpP3NU4owQ/rxowmSNqg+fHIF1likSvXvljYS" + "jaFXXnWfYibW7TdDCFFpN4sB5o13+as0u4vLw6MvOi59B1tLype1LcHpi1b9PfxNtznTTdet3kL0paxIcWtKHT0LDPUos8YYmiPa5nGbUqlC7d+4YT2jQPvwGxCws1oo2Tw6nj1UaihneYGAyvEky49FBwIDAQAB"},
-		},
-	}
-	results, err := dkim.Verify(context.Background(), log.Logger, resolver, false, func(*dkim.Sig) error { return nil }, bytes.NewReader(msgbuf), false)
-	if err != nil {
-		t.Fatalf("dkim verify: %v", err)
-	}
-	if len(results) != 1 || results[0].Status != dkim.StatusPass {
-		t.Fatalf("dkim result not pass, %#v", results)
-	}
-
 	// An utf-8 message.
 	m = Message{
 		SMTPUTF8: true,
 
-		From:     smtp.Path{Localpart: "postmæster", IPDomain: xparseIPDomain("møx.example")},
-		To:       smtp.Path{Localpart: "møx", IPDomain: xparseIPDomain("remøte.example")},
-		Subject:  "dsn¡",
-		TextBody: "delivery failure¿\n",
+		From:      smtp.Path{Localpart: "postmæster", IPDomain: xparseIPDomain("møx.example")},
+		To:        smtp.Path{Localpart: "møx", IPDomain: xparseIPDomain("remøte.example")},
+		Subject:   "dsn¡",
+		MessageID: "test@localhost",
+		TextBody:  "delivery failure¿\n",
 
 		ReportingMTA:    "mox.example",
 		ReceivedFromMTA: smtp.Ehlo{Name: xparseIPDomain("reläy.example"), ConnIP: net.ParseIP("10.10.10.10")},