audit 2c: findings of the two reviews

Technical review (Opus, 11 findings, 2 medium) and security review (Fable,
no high or medium) of 3c86280..HEAD. Both confirm the port gives
dkim_mail_parse()'s result on every input it parses, and that no line the
check passes is signed with another domain's key.

- F1 (medium): OpenDKIM's parser takes lines no mail program reads as one
  address - "ceo@bank.com:me@mine.com", "Name <ceo@bank.com:me@mine.com>",
  "<b@evil.com, a@mine.com>", "ceo@bank.com <me@mine.com>",
  "ceo@bank.com@mine.com" - and signs for the last while a lenient reader
  shows the first. The line must now also be one address in RFC 5322's
  grammar (net/mail, display names in any charset passed through), at the
  domain OpenDKIM signs for. A quoted display name may still hold anything.
- F2 (medium): the bindings were asked about OpenDKIM's form of the
  address, quotes and all, so "x"@mine.com passed for an application
  holding @mine.com while x@mine.com belonged to another. They are now
  asked about the reader's address, its local part unquoted, as Postfix
  holds the envelope's.
- F3 / security (low): Bindings.Allowed and DomainOf fold case in ASCII
  only: Postfix folds as Unicode (casefold.c, ICU), but every key and
  login the panel writes is ASCII, and the Unicode fold let the Kelvin sign
  pass for "k" (net/mail then refuses such a line on the domain test).
- F4 (low): a TERM between "postfix start-fg &" and "child=$!" is no longer
  lost: the wrapper stops Postfix as soon as the pid is known.
- F5 (low): for startsecs after a start any failed reload passed as "not
  running". postfix-reload is now build/postfix-reload.sh: exit 75 when
  master -t says no master runs, else exec postfix reload; RunOnce returns
  EndError with the status, and only 75 is taken as done. supervisor.State
  goes.
- F6 (low): crashexit spares postfix-reload too - a reload that could not
  be spawned is reported to whoever asked, not a reason to stop the
  container.
- F7 (low): a certs/ that is itself a link is resolved before the walk
  (filepath.WalkDir does not follow its root).
- F8 (low): at shutdown the tailer reads what is left of the rotated
  file before saving its place. Not changed: a refusal line still waiting
  on the old file at shutdown is not kept - the panel writes refused rows
  itself, only a kill loses one, and that window is the minute's grace.
- F9 (low): pct read as text - empty or unreadable is 100, the rest held
  to 0..100.
- F10 (low): the directory is synced after sasldb2's rename.
- F11 (low): POSTFIX_STARTSECS by expr, so "010" or "08" in
  MILTER_WAIT_TIMEOUT are decimal, not octal or an error.
- Security (low): pagehide also empties defaultValue - the input's value
  attribute and the textarea's text - not only .value. A sasldb2.new left
  by a killed panel is removed at start (entrypoint) and never archived.
  security.md says that links under certs/ are followed and by whom they
  can be placed.

Tests: sender check cases for F1 (four lines), F2 (a bound address
quoted, for its owner and for another), F3; EndError's state and status;
pct cases. architecture.md and CHANGELOG describe the reader rule. Stand
(2026-10-15, make e2e, exit 0); go vet and go test ./... pass on the
server (24 packages).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/app/sasl.go

@@ -9,6 +9,7 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 	"sync"
 )
@@ -113,6 +114,14 @@ func replaceSASLDB(path string, edit func(path string) error) error {
 		_ = os.Remove(tmp)
 		return fmt.Errorf("rename %s -> %s: %w", tmp, path, err)
 	}
+	// The rename is the directory's change; without its own sync a power
+	// loss may bring the old database back, out of step with the panel's
+	// records (review of stage 2c, F10). A directory that cannot be synced
+	// - not on every system - leaves the change as durable as before.
+	if dir, err := os.Open(filepath.Dir(path)); err == nil {
+		_ = dir.Sync()
+		dir.Close()
+	}
 	return nil
 }
 

internal/backup/backup.go

@@ -200,9 +200,16 @@ func validateDeployRoot(deployRoot string) error {
 // left out of the archive. A directory left out is not descended into.
 type skipFunc func(path, rel string, d fs.DirEntry) bool
 
-// skipQueue leaves the Postfix queue out of every archive.
+// skipQueue leaves the Postfix queue out of every archive, and the copy of
+// sasldb2 a change is made on (internal/app, replaceSASLDB): a panel killed
+// mid-change leaves it, a second copy of every application's password, until
+// the next start removes it (build/entrypoint.sh; review of stage 2c).
 func skipQueue(_, rel string, _ fs.DirEntry) bool {
-	return filepath.ToSlash(rel) == QueueDir
+	switch filepath.ToSlash(rel) {
+	case QueueDir, "sasl/sasldb2.new":
+		return true
+	}
+	return false
 }
 
 // Check reads through everything Create would put into the archive, without
@@ -258,6 +265,13 @@ func addDeployFiles(tw *tar.Writer, deployRoot string, onWarn func(string)) erro
 	}
 
 	certsDir := filepath.Join(deployRoot, CertsDirName)
+	// certs/ itself may be a link - the guide once had it linked to
+	// certbot's live/<host> - and the walk below does not follow its root
+	// (path/filepath, WalkDir: "WalkDir does not follow symbolic links"), so
+	// the link is resolved first (review of stage 2c, F7).
+	if resolved, err := filepath.EvalSymlinks(certsDir); err == nil {
+		certsDir = resolved
+	}
 	if _, err := os.Stat(certsDir); err != nil {
 		if os.IsNotExist(err) {
 			if onWarn != nil {

internal/dmarc/parse.go

@@ -7,6 +7,7 @@ import (
 	"encoding/xml"
 	"fmt"
 	"io"
+	"strconv"
 	"strings"
 	"time"
 	"unicode/utf8"
@@ -57,12 +58,12 @@ type feedbackXML struct {
 		} `xml:"date_range"`
 	} `xml:"report_metadata"`
 	Policy struct {
-		Domain string `xml:"domain"`
-		P      string `xml:"p"`
-		SP     string `xml:"sp"`
-		Pct    *int   `xml:"pct"`
-		ADKIM  string `xml:"adkim"`
-		ASPF   string `xml:"aspf"`
+		Domain string  `xml:"domain"`
+		P      string  `xml:"p"`
+		SP     string  `xml:"sp"`
+		Pct    *string `xml:"pct"`
+		ADKIM  string  `xml:"adkim"`
+		ASPF   string  `xml:"aspf"`
 	} `xml:"policy_published"`
 	Records []struct {
 		Row struct {
@@ -139,11 +140,15 @@ func ParseAggregate(raw []byte) (ParsedReport, error) {
 		PolicyASPF:   field(doc.Policy.ASPF),
 	}
 	// RFC 7489 § 6.3: pct is "between 0 and 100, inclusive", 100 when absent.
-	// An explicit 0 is a policy applied to no message, and stays 0; only a
-	// report without the element gets the default (assumptions C-M7).
+	// An explicit 0 is a policy applied to no message, and stays 0; a report
+	// without the element, or with an empty or unreadable one, gets the
+	// default, and a value outside the range is held to it (assumptions
+	// C-M7; review of stage 2c, F9).
 	out.PolicyPct = 100
 	if doc.Policy.Pct != nil {
-		out.PolicyPct = *doc.Policy.Pct
+		if n, err := strconv.Atoi(strings.TrimSpace(*doc.Policy.Pct)); err == nil {
+			out.PolicyPct = min(max(n, 0), 100)
+		}
 	}
 	for _, rec := range doc.Records {
 		row := ParsedRecord{

internal/dmarc/parse_test.go

@@ -271,6 +271,11 @@ func TestPolicyPct(t *testing.T) {
 		{"<pct>0</pct>", 0},
 		{"<pct>25</pct>", 25},
 		{"", 100},
+		{"<pct/>", 100},
+		{"<pct> 50 </pct>", 50},
+		{"<pct>150</pct>", 100},
+		{"<pct>-5</pct>", 0},
+		{"<pct>x</pct>", 100},
 	} {
 		doc := strings.Replace(sampleXML, "<pct>100</pct>", c.pct, 1)
 		got, err := ParseAggregate([]byte(doc))

internal/logtail/logtail.go

@@ -758,6 +758,10 @@ func follow(ctx context.Context, path string, tr *tracker, caughtUp chan struct{
 		select {
 		case <-ctx.Done():
 			blind.see(time.Now(), false)
+			// What postlogd wrote to the rotated file since the last tick:
+			// the next start resumes in the new file only (review of stage
+			// 2c, F8).
+			drainOld(time.Now())
 			tr.record(f, read(), true) // shutdown: the next start resumes here
 			return nil
 		case <-ticker.C:

internal/milter/sender.go

@@ -3,8 +3,11 @@ package milter
 import (
 	"context"
 	"fmt"
+	"io"
 	"log"
+	"mime"
 	"net"
+	"net/mail"
 	"net/textproto"
 	"os"
 	"strings"
@@ -201,13 +204,19 @@ func splitTableLine(line string) (key, value string, ok bool) {
 // whole domain (assumptions B-PS1). The bare local part MA_FIND_DEFAULT also
 // tries for a local domain is never a key here: every key the panel writes
 // has an "@" (internal/postfix renderSenderLoginMaps).
+//
+// Case is folded in ASCII only. Postfix folds as Unicode (src/util/casefold.c
+// with ICU, which Debian builds with), but every key and login the panel
+// writes is ASCII; a Unicode fold would only let a look-alike pass - the
+// Kelvin sign for "k" - for an address OpenDKIM, folding ASCII, does not
+// sign (review of stage 2c).
 func (b *Bindings) Allowed(login, addr string) (bool, error) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 	if err := b.fresh(); err != nil {
 		return false, err
 	}
-	login, addr = strings.ToLower(login), strings.ToLower(addr)
+	login, addr = asciiLower(login), asciiLower(addr)
 	keys := []string{addr}
 	// recipient_delimiter is "+" (build/postfix-config.sh), so an
 	// application listed as invoices@ may also send as invoices+march@.
@@ -256,7 +265,7 @@ func (b *Bindings) DomainOf(login string) string {
 	if b.fresh() != nil {
 		return ""
 	}
-	return b.domainOf[strings.ToLower(login)]
+	return b.domainOf[asciiLower(login)]
 }
 
 // Refusals is where the check leaves the send-log rows of what it refused.
@@ -384,7 +393,8 @@ func (s *senderSession) judge() (shown, why string, err error) {
 		// OpenDKIM takes the first; a reader may show the others.
 		return shown, "it must be one address", nil
 	}
-	addr := r.user + "@" + asciiLower(r.domain)
+	signedDomain := asciiLower(r.domain)
+	addr := r.user + "@" + signedDomain
 	// OpenDKIM matches its SigningTable against "user@domain" as
 	// snprintf() leaves it in a buffer of MAXADDRESS + 1 = 257 bytes
 	// (opendkim.c, dkimf_apply_signtable(); libopendkim/dkim-internal.h).
@@ -394,8 +404,26 @@ func (s *senderSession) judge() (shown, why string, err error) {
 	if len(addr) > 256 {
 		return printable(addr), "the address is longer than OpenDKIM reads whole", nil
 	}
-	shown = printable(addr)
-	ok, err := s.bind.Allowed(s.login, asciiLower(addr))
+	// The address a mail program shows. OpenDKIM's parser reads lines no
+	// standard reader takes for one address - "ceo@bank.com:me@mine.com",
+	// "ceo@bank.com <me@mine.com>", "<b@evil.com, a@mine.com>" - and signs
+	// for the last of them while a lenient program shows the first. So the
+	// line must also be one address in RFC 5322's grammar (net/mail), at the
+	// domain OpenDKIM signs for; a quoted display name may say anything.
+	// And that address, its local part unquoted as Postfix holds the
+	// envelope's (Postfix 3.7.11, src/global/tok822_parse.c), is the one
+	// held against the bindings: "x"@mine.com is x@mine.com, which may be
+	// another application's (review of stage 2c, F1, F2).
+	list, perr := fromParser.ParseList(unfold(raw))
+	if perr != nil || len(list) != 1 {
+		return shown, "it must be one address, as a mail program reads it", nil
+	}
+	seen := asciiLower(list[0].Address)
+	if domainOf(seen) != signedDomain {
+		return shown, "a mail program would show another address than the one signed", nil
+	}
+	shown = printable(seen)
+	ok, err := s.bind.Allowed(s.login, seen)
 	if err != nil {
 		return shown, "", fmt.Errorf("sender bindings: %w", err)
 	}
@@ -405,6 +433,20 @@ func (s *senderSession) judge() (shown, why string, err error) {
 	return shown, "", nil
 }
 
+// fromParser reads the From: line as a mail program would. A display name
+// encoded in a charset Go does not convert (windows-1251, koi8-r, ...) is
+// still a display name: its bytes are passed through unread.
+var fromParser = mail.AddressParser{WordDecoder: &mime.WordDecoder{
+	CharsetReader: func(charset string, input io.Reader) (io.Reader, error) { return input, nil },
+}}
+
+// unfold joins the lines of a folded header value (RFC 5322 2.2.3): a line
+// break is dropped, the white space that follows it stays. Postfix hands a
+// milter the line breaks as LF (assumptions B-PM12).
+func unfold(v string) string {
+	return strings.NewReplacer("\r\n", "", "\n", "", "\r", "").Replace(v)
+}
+
 // asciiLower lower-cases A-Z only, as OpenDKIM's dkimf_lowercase() and
 // Postfix's table lookups do; strings.ToLower would also fold characters
 // outside ASCII - the Kelvin sign to "k" - into names they are not.

internal/milter/sender_test.go

@@ -20,6 +20,8 @@ import (
 // example.org, and two applications share shop.example.org.
 const senderMaps = `@news.example.net news
 @shop.example.org shop,shop2
+desk@shop.example.org shop2
+@kiosk.example.net kiosk
 invoices@example.org billing
 billing@example.org billing
 `
@@ -102,9 +104,24 @@ func TestSenderCheck(t *testing.T) {
 		{"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>")}, true, ""},
 		{"a stranger's address in a comment", "shop", [][2]string{from("a@shop.example.org (someone@gmail.example)")}, true, ""},
-		{"an unquoted address as the display name", "shop", [][2]string{from("director@example.org <a@shop.example.org>")}, true, ""},
+		{"an unquoted address as the display name", "shop", [][2]string{from("director@example.org <a@shop.example.org>")}, false, "as a mail program reads it"},
 		{"another domain inside a quoted local part", "shop", [][2]string{from(`"director@example.org"@shop.example.org`)}, true, ""},
-		{"no local part: OpenDKIM takes the domain for it", "shop", [][2]string{from("@shop.example.org")}, true, ""},
+		{"no local part: OpenDKIM takes the domain for it", "shop", [][2]string{from("@shop.example.org")}, false, "as a mail program reads it"},
+		// Lines OpenDKIM signs for the application's domain while a lenient
+		// mail program shows another address first (review of stage 2c, F1).
+		{"another address before a colon", "shop", [][2]string{from("ceo@bank.example:me@shop.example.org")}, false, "as a mail program reads it"},
+		{"a route-like colon inside the brackets", "shop", [][2]string{from("Name <ceo@bank.example:me@shop.example.org>")}, false, "as a mail program reads it"},
+		{"a list inside the brackets", "shop", [][2]string{from("<b@evil.example, a@shop.example.org>")}, false, "as a mail program reads it"},
+		{"an address with two @", "shop", [][2]string{from("ceo@bank.example@shop.example.org")}, false, "as a mail program reads it"},
+		// An address bound to another application, its local part quoted
+		// (F2): a reader and Postfix take "desk" for desk.
+		{"another application's address, quoted", "shop", [][2]string{from(`"desk"@shop.example.org`)}, false, "not an address this application sends as"},
+		{"its own bound address, quoted", "shop2", [][2]string{from(`"desk"@shop.example.org`)}, true, ""},
+		// A look-alike of the domain in a character a Unicode fold maps
+		// to ASCII (F3): OpenDKIM would not sign it, and it is not the
+		// application's.
+		{"the Kelvin sign for k in the domain", "kiosk", [][2]string{from("a@\u212Aiosk.example.net")}, false, "a mail program would show another address"},
+		{"the same domain in ASCII", "kiosk", [][2]string{from("a@kiosk.example.net")}, 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"},

internal/postfix/postfix.go

@@ -6,6 +6,7 @@
 package postfix
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"path/filepath"
@@ -194,18 +195,22 @@ func assertMapSafe(address, login string) error {
 // saved shows. Before, supervisorctl's start returned as the reload was
 // spawned, and a reload already running counted as done though it may have
 // read the files before this change (supervisor.RunOnce; assumptions B-U2).
-// A reload that fails while program postfix is not RUNNING - stopped, or
-// still in its start, the wrapper waiting for the milter sockets - is no
-// error: "the Postfix mail system is not running", and the master that starts
-// next reads the files as they are now.
+// A reload while no master runs - Postfix stopped, or still in its start,
+// the wrapper waiting for the milter sockets - is no error: the program exits
+// 75 then (build/postfix-reload.sh), and the master that starts next reads
+// the files as they are now. Before, the program's state stood in for that,
+// and for the whole of startsecs after a start any failed reload passed as
+// one (review of stage 2c, F5).
 func reloadViaSupervisor() error {
 	err := supervisor.RunOnce("postfix-reload")
-	if err == nil {
-		return nil
-	}
-	if state, serr := supervisor.State("postfix"); serr == nil && state != "RUNNING" {
-		log.Printf("postfix: reload while program postfix is %s, left to its start: %v", state, err)
+	var end *supervisor.EndError
+	if errors.As(err, &end) && end.State == "EXITED" && end.Status == reloadNotRunning {
+		log.Printf("postfix: no Postfix master runs; its start reads the files")
 		return nil
 	}
 	return err
 }
+
+// reloadNotRunning is build/postfix-reload.sh's exit status when no master
+// runs.
+const reloadNotRunning = 75

internal/supervisor/rpc.go

@@ -66,16 +66,6 @@ func RunOnce(program string) error {
 	return newRPC(socketPath).runOnce(program)
 }
 
-// State is the state supervisord gives a program, by its name: RUNNING,
-// STARTING, EXITED ... (supervisor 4.2.5, supervisor/states.py).
-func State(program string) (string, error) {
-	v, err := newRPC(socketPath).call("supervisor.getProcessInfo", program)
-	if err != nil {
-		return "", fmt.Errorf("supervisor: state of %s: %w", program, err)
-	}
-	return v.members()["statename"].str(), nil
-}
-
 type rpc struct {
 	client *http.Client
 }
@@ -125,11 +115,25 @@ func (c *rpc) runOnce(program string) error {
 	if info.state == stateExited && info.exitStatus == 0 {
 		return nil
 	}
-	msg := fmt.Sprintf("supervisor: %s ended %s, exit status %d", program, info.stateName, info.exitStatus)
-	if info.spawnErr != "" {
-		msg += ": " + info.spawnErr
+	return &EndError{Program: program, State: info.stateName, Status: info.exitStatus, SpawnErr: info.spawnErr}
+}
+
+// EndError is a run of RunOnce that did not end EXITED with status 0: the
+// state it ended in, its exit status, and supervisord's account of a failed
+// spawn.
+type EndError struct {
+	Program  string
+	State    string
+	Status   int
+	SpawnErr string
+}
+
+func (e *EndError) Error() string {
+	msg := fmt.Sprintf("supervisor: %s ended %s, exit status %d", e.Program, e.State, e.Status)
+	if e.SpawnErr != "" {
+		msg += ": " + e.SpawnErr
 	}
-	return errors.New(msg)
+	return msg
 }
 
 // processInfo is the part of getProcessInfo's struct RunOnce reads.

internal/supervisor/rpc_test.go

@@ -1,6 +1,7 @@
 package supervisor
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -120,6 +121,10 @@ func TestRunOnceReportsAFailedRun(t *testing.T) {
 	if err == nil || !strings.Contains(err.Error(), "ended EXITED, exit status 1") {
 		t.Fatalf("runOnce: %v; want the exit status 1", err)
 	}
+	var end *EndError
+	if !errors.As(err, &end) || end.State != "EXITED" || end.Status != 1 {
+		t.Fatalf("runOnce: %#v; want an EndError, EXITED, status 1", err)
+	}
 }
 
 // A run in progress may have read the files before the caller wrote them:

internal/web/view/static/panel.js

@@ -74,8 +74,14 @@
   // traversal (its salvageable state, the event's persisted).
   window.addEventListener("pagehide", function () {
     var secrets = document.querySelectorAll("[data-secret]");
+    // defaultValue too: it is the input's value attribute and the
+    // textarea's text, which the kept page still holds after .value is
+    // emptied (HTML, "The input element": defaultValue reflects the value
+    // content attribute; "The textarea element": its setter replaces the
+    // child text).
     for (var i = 0; i < secrets.length; i++) {
       secrets[i].value = "";
+      secrets[i].defaultValue = "";
     }
   });