Add two-factor login (TOTP) with recovery codes

Users can set up an authenticator app from their account page; login
then asks for a code after the password, with one-time recovery codes
as a fallback. Sensitive actions (tokens, user changes, 2FA resets)
need a code from the last 5 minutes. totp.require (none/admins/all)
forces setup, and admins can reset a user's 2FA from the UI, the jarl
CLI or jarld on the server. The dashboard and jarl status flag users
missing 2FA and a shared "admin" account still in use.

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

internal/totp/totp_test.go

@@ -0,0 +1,82 @@
+package totp
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+// The SHA-1 test vectors of RFC 6238 appendix B, cut to 6 digits.
+func TestCodeRFC6238(t *testing.T) {
+	secret := b32.EncodeToString([]byte("12345678901234567890"))
+	for _, c := range []struct {
+		unix int64
+		want string
+	}{
+		{59, "287082"},
+		{1111111109, "081804"},
+		{1111111111, "050471"},
+		{1234567890, "005924"},
+		{2000000000, "279037"},
+		{20000000000, "353130"},
+	} {
+		got, err := Code(secret, Step(time.Unix(c.unix, 0)))
+		if err != nil || got != c.want {
+			t.Errorf("T=%d: %q, %v; want %q", c.unix, got, err, c.want)
+		}
+	}
+}
+
+func TestVerify(t *testing.T) {
+	secret := NewSecret()
+	now := time.Unix(1_800_000_000, 0)
+	cur := Step(now)
+	code := func(step int64) string { c, _ := Code(secret, step); return c }
+	if step, ok := Verify(secret, code(cur), now, 0); !ok || step != cur {
+		t.Fatal("current code refused")
+	}
+	if _, ok := Verify(secret, code(cur - 1)[:3]+" "+code(cur - 1)[3:], now, 0); !ok {
+		t.Error("previous step (with a space) refused")
+	}
+	if _, ok := Verify(secret, code(cur+1), now, 0); !ok {
+		t.Error("next step refused")
+	}
+	if _, ok := Verify(secret, code(cur-2), now, 0); ok {
+		t.Error("code from a minute ago accepted")
+	}
+	// Replay: a step at or before the last used one is refused.
+	if _, ok := Verify(secret, code(cur), now, cur); ok {
+		t.Error("reused code accepted")
+	}
+	if _, ok := Verify(secret, code(cur+1), now, cur); !ok {
+		t.Error("newer code refused after a used one")
+	}
+	if _, ok := Verify(secret, "abcdef", now, 0); ok {
+		t.Error("letters accepted")
+	}
+}
+
+func TestURIAndQR(t *testing.T) {
+	u := URI("Jarl ns1", "adam", "JBSWY3DPEHPK3PXP")
+	if !strings.HasPrefix(u, "otpauth://totp/Jarl%20ns1:adam?") || !strings.Contains(u, "secret=JBSWY3DPEHPK3PXP") || !strings.Contains(u, "issuer=Jarl+ns1") {
+		t.Errorf("uri = %s", u)
+	}
+	img, err := QRDataURI(u)
+	if err != nil || !strings.HasPrefix(img, "data:image/svg+xml;base64,") {
+		t.Errorf("qr = %.60s, %v", img, err)
+	}
+}
+
+func TestRecoveryCodes(t *testing.T) {
+	codes := NewRecoveryCodes(RecoveryCodes)
+	seen := map[string]bool{}
+	for _, c := range codes {
+		if len(c) != 11 || c[5] != '-' || seen[c] || IsCode(c) {
+			t.Errorf("bad code %q", c)
+		}
+		seen[c] = true
+	}
+	if NormalizeRecovery(" K7DM2-XQ9PW ") != "k7dm2xq9pw" {
+		t.Error("normalize")
+	}
+}