selfpost/internal/milter/sender_test.go

package milter

import (
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"testing"
	"time"

	"github.com/emersion/go-milter"

	"github.com/mixeme/selfpost/internal/store"
)

// senderMaps is a sender_login_maps file as internal/postfix writes it: shop
// and news send as any address of their domains, billing only as two listed
// addresses of example.org, and two applications share shop.example.org.
const senderMaps = `@news.example.net news
@shop.example.org shop,shop2
invoices@example.org billing
billing@example.org billing
`

// signingTable is OpenDKIM's SigningTable for the same server: the three
// sending domains, one more that has no application yet, and the server's own
// name.
const signingTable = `*@news.example.net selfpost._domainkey.news.example.net
*@shop.example.org selfpost._domainkey.shop.example.org
*@example.org selfpost._domainkey.example.org
*@empty.example.com selfpost._domainkey.empty.example.com
*@mail.example.org selfpost._domainkey.mail.example.org
`

func signers(t *testing.T) *Signers {
	t.Helper()
	return NewSigners(writeMaps(t, signingTable))
}

func writeMaps(t *testing.T, content string) string {
	t.Helper()
	p := filepath.Join(t.TempDir(), "table")
	if err := os.WriteFile(p, []byte(content), 0o644); err != nil {
		t.Fatal(err)
	}
	return p
}

// offer plays one message to the check and returns the reply at the end of
// the headers, with what was left for the log.
func offer(t *testing.T, bind *Bindings, login, envelope string, headers ...[2]string) (milter.Response, []store.SendLogEntry) {
	t.Helper()
	refused := make(chan store.SendLogEntry, 8)
	s := &senderSession{bind: bind, signers: signers(t), refused: refused}
	if _, err := s.MailFrom(envelope, mods(map[string]string{"{auth_authen}": login})); err != nil {
		t.Fatal(err)
	}
	if _, err := s.RcptTo("someone@elsewhere.example", mods(nil)); err != nil {
		t.Fatal(err)
	}
	for _, h := range headers {
		if _, err := s.Header(h[0], h[1], mods(nil)); err != nil {
			t.Fatal(err)
		}
	}
	resp, err := s.Headers(nil, mods(nil))
	if err != nil {
		t.Fatal(err)
	}
	close(refused)
	var rows []store.SendLogEntry
	for e := range refused {
		rows = append(rows, e)
	}
	return resp, rows
}

func replyText(r milter.Response) string {
	m := r.Response()
	return string(rune(m.Code)) + " " + strings.TrimRight(string(m.Data), "\x00")
}

func TestSenderCheck(t *testing.T) {
	bind := NewBindings(writeMaps(t, senderMaps))
	from := func(v string) [2]string { return [2]string{"From", v} }

	cases := []struct {
		name     string
		login    string
		headers  [][2]string
		pass     bool
		wantText string // a part of the refusal
	}{
		{"own address", "shop", [][2]string{from("shop@shop.example.org")}, true, ""},
		{"own domain, any address, with a name", "shop", [][2]string{from(`"The Shop" <Orders@Shop.Example.Org>`)}, true, ""},
		{"second application of the domain", "shop2", [][2]string{from("x@shop.example.org")}, true, ""},
		{"a listed address", "billing", [][2]string{from("Invoices <invoices@example.org>")}, true, ""},
		{"a listed address with an extension", "billing", [][2]string{from("invoices+2026-march@example.org")}, true, ""},
		{"an extension, any address of the domain", "shop", [][2]string{from("orders+48213@shop.example.org")}, true, ""},
		{"header name in another case", "shop", [][2]string{{"FROM", "a@shop.example.org"}}, true, ""},
		{"its own name inside the display name", "shop", [][2]string{from(`"shop@shop.example.org" <a@shop.example.org>`)}, true, ""},
		{"an encoded display name", "shop", [][2]string{from("=?utf-8?b?0JzQsNCz0LDQt9C40L0=?= <a@shop.example.org>")}, true, ""},
		{"a folded line", "shop", [][2]string{from("\"A very long display name of the shop\"\r\n <a@shop.example.org>")}, true, ""},
		{"an encoded name, folded", "shop", [][2]string{from("=?utf-8?b?0JzQsNCz0LDQt9C40L0=?=\n\t<a@shop.example.org>")}, true, ""},
		{"a name in windows-1251", "shop", [][2]string{from("=?windows-1251?B?zODj4Ofo7Q==?= <a@shop.example.org>")}, true, ""},
		{"a name in koi8-r, quoted-printable", "shop", [][2]string{from("=?koi8-r?Q?=ED=C1=C7=C1=DA=C9=CE?= <a@shop.example.org>")}, true, ""},
		{"a comment after the address", "shop", [][2]string{from("a@shop.example.org (the shop)")}, true, ""},

		{"another registered domain", "shop", [][2]string{from("director@example.org")}, false, "not an address this application sends as"},
		{"the server's own name", "shop", [][2]string{from("postmaster@mail.example.org")}, false, "not an address this application sends as"},
		{"a stranger's domain", "shop", [][2]string{from("someone@gmail.example")}, false, "not an address this application sends as"},
		{"an address off the list", "billing", [][2]string{from("director@example.org")}, false, "not an address this application sends as"},
		{"an address off the list, with an extension", "billing", [][2]string{from("director+invoices@example.org")}, false, "not an address this application sends as"},
		{"a listed name as the extension of another", "billing", [][2]string{from("+invoices@example.org")}, false, "not an address this application sends as"},
		{"a subdomain of its own", "shop", [][2]string{from("a@sub.shop.example.org")}, false, "not an address this application sends as"},
		{"no From: line", "shop", [][2]string{{"Subject", "hello"}}, false, "no From: line"},
		{"two From: lines", "shop", [][2]string{from("a@shop.example.org"), from("director@example.org")}, false, "more than one From: line"},
		{"two addresses in one line", "shop", [][2]string{from("a@shop.example.org, director@example.org")}, false, "one address"},
		{"not an address", "shop", [][2]string{from("the shop")}, false, "one address"},
		{"a group", "shop", [][2]string{from("friends: a@shop.example.org, b@shop.example.org;")}, false, "one address"},
		{"another sender in the display name", "shop", [][2]string{from(`"director@example.org" <a@shop.example.org>`)}, false, "names another sender of this server"},
		{"the server's name in a comment", "shop", [][2]string{from("a@shop.example.org (postmaster@mail.example.org)")}, false, "names another sender of this server"},
		{"a domain with a key and no application, in the display name", "shop", [][2]string{from(`"x@empty.example.com" <a@shop.example.org>`)}, false, "names another sender of this server"},
		{"a stranger's address in the display name", "shop", [][2]string{from(`"someone@gmail.example" <a@shop.example.org>`)}, true, ""},
		{"another sender in an encoded display name", "shop", [][2]string{from("=?utf-8?q?director=40example=2Eorg?= <a@shop.example.org>")}, false, "names another sender of this server"},
		{"a stranger's address in a comment", "shop", [][2]string{from("a@shop.example.org (someone@gmail.example)")}, false, "one @"},
		{"another sender folded onto the next line", "shop", [][2]string{from("\"x\"\r\n <director@example.org>")}, false, "not an address this application sends as"},
		{"a quote left open before another address", "shop", [][2]string{from(`"a@shop.example.org <director@example.org>`)}, false, "one address"},
		{"no login", "", [][2]string{from("a@shop.example.org")}, false, "no authenticated application"},
		{"an unknown login", "ghost", [][2]string{from("a@shop.example.org")}, false, "not an address this application sends as"},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			resp, rows := offer(t, bind, c.login, "shop@shop.example.org", c.headers...)
			if c.pass {
				if resp != milter.RespContinue {
					t.Fatalf("refused: %s", replyText(resp))
				}
				if len(rows) != 0 {
					t.Fatalf("a passed message left rows: %+v", rows)
				}
				return
			}
			text := replyText(resp)
			if !strings.HasPrefix(text, "y 550 5.7.1 From: ") || !strings.Contains(text, c.wantText) {
				t.Fatalf("reply %q, want a 550 5.7.1 saying %q", text, c.wantText)
			}
			// The reason names no other domain of the server (audit L8); the
			// From: line before it is what the client wrote itself.
			reason := text[strings.LastIndex(text, " - ")+3:]
			for _, other := range []string{"example.com", "mail.example.org", "example.org"} {
				if strings.Contains(reason, other) {
					t.Fatalf("the reason %q names %s", reason, other)
				}
			}
			if len(rows) != 1 || rows[0].Reason != store.ReasonFrom || rows[0].To != "someone@elsewhere.example" || rows[0].AppLogin != c.login {
				t.Fatalf("log rows: %+v", rows)
			}
		})
	}
}

// What the client wrote is said back to it, logged and stored: it must not
// be able to put a line break or a control character there.
func TestSenderCheckPrintsNothingRaw(t *testing.T) {
	bind := NewBindings(writeMaps(t, senderMaps))
	evil := "x@gmail.example\r\n250 ok %s \x00\x1b[31m " + strings.Repeat("a", 400)
	resp, rows := offer(t, bind, "shop", "shop@shop.example.org", [2]string{"From", evil})
	text := replyText(resp)
	for _, bad := range []string{"\r", "\n", "%", "\x1b"} {
		if strings.Contains(text, bad) || strings.Contains(rows[0].HeaderFrom, bad) {
			t.Fatalf("%q got through: %q / %q", bad, text, rows[0].HeaderFrom)
		}
	}
	if len(rows[0].HeaderFrom) > 130 {
		t.Fatalf("stored %d bytes of the header", len(rows[0].HeaderFrom))
	}
}

// Without its file the check knows nothing, and what cannot be checked is
// deferred - neither passed nor refused for good.
func TestSenderCheckDefersWithoutBindings(t *testing.T) {
	bind := NewBindings(filepath.Join(t.TempDir(), "absent"))
	resp, rows := offer(t, bind, "shop", "shop@shop.example.org", [2]string{"From", "a@shop.example.org"})
	if resp != milter.RespTempFail {
		t.Fatalf("reply %s, want a temporary failure", replyText(resp))
	}
	if len(rows) != 0 {
		t.Fatalf("a deferred message left rows: %+v", rows)
	}
}

// The panel rewrites the file when an application is added or deleted; the
// check has to follow without a restart.
func TestBindingsFollowTheFile(t *testing.T) {
	p := writeMaps(t, senderMaps)
	bind := NewBindings(p)
	if ok, err := bind.Allowed("shop", "a@shop.example.org"); err != nil || !ok {
		t.Fatalf("before: %v %v", ok, err)
	}
	if err := os.WriteFile(p, []byte("@news.example.net news\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	// A rewrite within the clock's resolution that keeps the size would not be
	// seen; the panel replaces the file by rename, which gives it a new time.
	later := time.Now().Add(2 * time.Second)
	if err := os.Chtimes(p, later, later); err != nil {
		t.Fatal(err)
	}
	if ok, err := bind.Allowed("shop", "a@shop.example.org"); err != nil || ok {
		t.Fatalf("after the application was deleted: %v %v", ok, err)
	}
}

// Without the signing table the second look cannot be taken, and a line it
// would have to judge is deferred; a line that names nobody else is not held
// up by it.
func TestSenderCheckDefersWithoutSigningTable(t *testing.T) {
	bind := NewBindings(writeMaps(t, senderMaps))
	play := func(v string) milter.Response {
		s := &senderSession{bind: bind, signers: NewSigners(filepath.Join(t.TempDir(), "absent"))}
		_, _ = s.MailFrom("shop@shop.example.org", mods(map[string]string{"{auth_authen}": "shop"}))
		_, _ = s.Header("From", v, mods(nil))
		resp, _ := s.Headers(nil, mods(nil))
		return resp
	}
	if resp := play(`"x@example.org" <a@shop.example.org>`); resp != milter.RespTempFail {
		t.Fatalf("reply %s, want a temporary failure", replyText(resp))
	}
	if resp := play(`a@shop.example.org`); resp != milter.RespContinue {
		t.Fatalf("a plain own address: %s", replyText(resp))
	}
}

// A second message on the connection is judged by its own headers.
func TestSenderCheckResetsBetweenMessages(t *testing.T) {
	bind := NewBindings(writeMaps(t, senderMaps))
	s := &senderSession{bind: bind, signers: signers(t)}
	auth := mods(map[string]string{"{auth_authen}": "shop"})
	for i, v := range []string{"director@example.org", "a@shop.example.org", "director@example.org"} {
		_, _ = s.MailFrom("shop@shop.example.org", auth)
		_, _ = s.Header("From", v, mods(nil))
		resp, _ := s.Headers(nil, mods(nil))
		if passed := resp == milter.RespContinue; passed != (i == 1) {
			t.Fatalf("message %d (From: %s): passed=%v", i, v, passed)
		}
	}
}

// A refused message is one row of the log however many recipients it had.
func TestSenderCheckRefusalIsOneRow(t *testing.T) {
	bind := NewBindings(writeMaps(t, senderMaps))
	refused := make(chan store.SendLogEntry, 8)
	s := &senderSession{bind: bind, signers: signers(t), refused: refused}
	_, _ = s.MailFrom("shop@shop.example.org", mods(map[string]string{"{auth_authen}": "shop"}))
	for _, r := range []string{"a@x.example", "b@x.example", "c@x.example"} {
		_, _ = s.RcptTo(r, mods(nil))
	}
	_, _ = s.Header("From", "director@example.org", mods(nil))
	_, _ = s.Headers(nil, mods(nil))
	close(refused)
	var rows []store.SendLogEntry
	for e := range refused {
		rows = append(rows, e)
	}
	if len(rows) != 1 || rows[0].To != "a@x.example and 2 more" {
		t.Fatalf("rows = %+v", rows)
	}
}

// A message with the null envelope sender - a bounce an application writes
// itself - is judged like any other, and its row belongs to the domain the
// login is bound to.
func TestSenderCheckRefusalWithNullSenderHasItsDomain(t *testing.T) {
	bind := NewBindings(writeMaps(t, senderMaps))
	for login, want := range map[string]string{"shop": "shop.example.org", "billing": "example.org"} {
		_, rows := offer(t, bind, login, "", [2]string{"From", "someone@gmail.example"})
		if len(rows) != 1 || rows[0].Domain != want || rows[0].From != "" {
			t.Errorf("%s: rows = %+v, want one of domain %s", login, rows, want)
		}
	}
}

// passedFromLines reads testdata/from-lines-passed.txt with {domain} put in.
func passedFromLines(t *testing.T, domain string) []string {
	t.Helper()
	raw, err := os.ReadFile(filepath.Join("testdata", "from-lines-passed.txt"))
	if err != nil {
		t.Fatal(err)
	}
	var out []string
	for _, line := range strings.Split(string(raw), "\n") {
		line = strings.TrimSpace(line)
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		s, err := strconv.Unquote(line)
		if err != nil {
			t.Fatalf("%s: %v", line, err)
		}
		out = append(out, strings.ReplaceAll(s, "{domain}", domain))
	}
	return out
}

// Every line of the shared file is passed for the domain's application; the
// e2e then checks OpenDKIM signs each for that domain alone.
func TestSenderCheckPassesTheSharedLines(t *testing.T) {
	bind := NewBindings(writeMaps(t, senderMaps))
	for _, line := range passedFromLines(t, "shop.example.org") {
		resp, rows := offer(t, bind, "shop", "shop@shop.example.org", [2]string{"From", line})
		if resp != milter.RespContinue || len(rows) != 0 {
			t.Errorf("From: %q refused: %s", line, replyText(resp))
		}
	}
}