Refuse passwords over 72 bytes and confirm only stored ones (closes #144)

bcrypt cannot hash a password longer than 72 bytes. PASS over the HTTP
API answered one with a 500, and the IRC listener confirmed it without
storing it.

Both transports now refuse a password outside 8 to 72 bytes with the
reply a short one already got: 461 over the HTTP API, a NOTICE over the
IRC listener. setPassword returns its error, and "Password set" is sent
only when the password was stored. A PASS given before registration is
checked after the welcome burst and gets the same NOTICE.

Model: opus-5-5

internal/ircserver/commands.go

@@ -1216,15 +1216,14 @@ func (c *Conn) handlePassPostReg(
 	}
 
 	password := msg.Params[0]
-	if len(password) < minPasswordLen {
-		c.sendFromServer("NOTICE", c.nick,
-			"Password must be at least 8 characters",
-		)
-
+	if !c.checkPasswordLength(password) {
 		return
 	}
 
-	c.setPassword(ctx, password)
+	err := c.setPassword(ctx, password)
+	if err != nil {
+		return
+	}
 
 	c.sendFromServer("NOTICE", c.nick,
 		"Password set. You can reconnect using "+

internal/ircserver/conn.go

@@ -27,6 +27,7 @@ const (
 	pingInterval    = 90 * time.Second
 	pongDeadline    = 30 * time.Second
 	minPasswordLen  = 8
+	maxPasswordLen  = 72 // bcrypt cannot hash a longer one
 	maxHashcashBits = 40
 )
 
@@ -550,17 +551,18 @@ func (c *Conn) completeRegistration(ctx context.Context) {
 	// So that KILL, from either transport, can close it.
 	c.svc.RegisterWireConn(sessionID, c)
 
-	// If PASS was provided before registration, set the
-	// session password.
-	if c.passWord != "" && len(c.passWord) >= minPasswordLen {
-		c.setPassword(ctx, c.passWord)
-	}
-
 	// Send welcome burst.
 	c.deliverWelcome()
 	c.deliverLusers(ctx)
 	c.deliverMOTD()
 
+	// If PASS was provided before registration, set the
+	// session password now. A failure to store it is only
+	// logged, as it is for PASS after registration.
+	if c.passWord != "" && c.checkPasswordLength(c.passWord) {
+		_ = c.setPassword(ctx, c.passWord)
+	}
+
 	// Start the message relay goroutine.
 	go c.relayMessages(ctx)
 }
@@ -643,13 +645,33 @@ func (c *Conn) deliverMOTD() {
 	)
 }
 
-// setPassword sets a bcrypt password on the session.
-func (c *Conn) setPassword(ctx context.Context, pw string) {
+// checkPasswordLength reports whether pw is 8 to 72 bytes
+// long, and sends the client a NOTICE saying so when it is
+// not.
+func (c *Conn) checkPasswordLength(pw string) bool {
+	if len(pw) >= minPasswordLen && len(pw) <= maxPasswordLen {
+		return true
+	}
+
+	c.sendFromServer("NOTICE", c.nick,
+		"Password must be 8 to 72 bytes",
+	)
+
+	return false
+}
+
+// setPassword sets a bcrypt password on the session, and
+// logs and returns the error when it was not stored.
+func (c *Conn) setPassword(ctx context.Context, pw string) error {
 	// Use the database's auth module to hash and store.
 	err := c.database.SetPassword(ctx, c.sessionID, pw)
 	if err != nil {
 		c.log.Error(
 			"failed to set password", "error", err,
 		)
+
+		return err
 	}
+
+	return nil
 }

internal/ircserver/server_test.go

@@ -1158,6 +1158,131 @@ func TestHandlePassPostRegistration(t *testing.T) {
 	)
 }
 
+// maxPasswordBytes is the longest password bcrypt can hash.
+const maxPasswordBytes = 72
+
+// passwordLengthNotice is the NOTICE text for a password that
+// is too short or too long.
+const passwordLengthNotice = "Password must be 8 to 72 bytes"
+
+// assertCanLogin fails the test if nick cannot log in with
+// password.
+func assertCanLogin(t *testing.T, env *testEnv, nick, password string) {
+	t.Helper()
+
+	_, _, token, err := env.database.LoginUser(
+		t.Context(), nick, password, "127.0.0.1", "localhost",
+	)
+	if err != nil || token == "" {
+		t.Errorf("log in as %s: token %q, %v", nick, token, err)
+	}
+}
+
+// TestPassPostRegistrationLength checks that a PASS over
+// maxPasswordBytes after registration is refused with a
+// NOTICE, and that one of exactly maxPasswordBytes is stored
+// and confirmed.
+func TestPassPostRegistrationLength(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+	client := env.dial(t)
+
+	client.register("longpass")
+
+	client.sendAndExpect(
+		"PASS :"+strings.Repeat("a", maxPasswordBytes+1),
+		passwordLengthNotice,
+	)
+
+	longest := strings.Repeat("a", maxPasswordBytes)
+	client.sendAndExpect("PASS :"+longest, "Password set")
+
+	assertCanLogin(t, env, "longpass", longest)
+}
+
+// TestPassPostRegistrationNotStored checks that PASS is not
+// confirmed when the password could not be stored.
+func TestPassPostRegistrationNotStored(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+	client := env.dial(t)
+
+	client.register("failpass")
+
+	_, err := env.database.GetDB().ExecContext(t.Context(),
+		`CREATE TRIGGER refuse_password
+		 BEFORE UPDATE OF password_hash ON sessions
+		 BEGIN SELECT RAISE(ABORT, 'refused'); END`,
+	)
+	if err != nil {
+		t.Fatalf("create trigger: %v", err)
+	}
+
+	client.send("PASS :mypassword123")
+
+	// The server answers commands in order, so anything it
+	// sent about PASS comes before the PONG.
+	lines := client.sendAndExpect("PING :after", "PONG")
+
+	assertNotContains(
+		t, lines, "Password set",
+		"confirmation of a password that was not stored",
+	)
+}
+
+// TestPassBeforeRegistrationLength checks that a PASS before
+// registration that is too short or too long is refused with
+// a NOTICE once registration completes.
+func TestPassBeforeRegistrationLength(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		nick, password string
+	}{
+		{"preshort", "short"},
+		{"prelong", strings.Repeat("a", maxPasswordBytes+1)},
+	}
+
+	env := newTestEnv(t)
+
+	for _, tc := range cases {
+		t.Run(tc.nick, func(t *testing.T) {
+			t.Parallel()
+
+			client := env.dial(t)
+
+			client.send("PASS :" + tc.password)
+			client.register(tc.nick)
+
+			client.readUntil(func(line string) bool {
+				return strings.Contains(line, passwordLengthNotice)
+			})
+		})
+	}
+}
+
+// TestPassBeforeRegistrationStored checks that a PASS of
+// exactly maxPasswordBytes before registration is stored.
+func TestPassBeforeRegistrationStored(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnv(t)
+	client := env.dial(t)
+
+	longest := strings.Repeat("a", maxPasswordBytes)
+
+	client.send("PASS :" + longest)
+	client.register("prestored")
+
+	// The password is stored after the welcome burst; the
+	// PONG comes after that.
+	client.sendAndExpect("PING :after", "PONG")
+
+	assertCanLogin(t, env, "prestored", longest)
+}
+
 func TestPreRegistrationNotRegistered(t *testing.T) {
 	t.Parallel()