Sign in through the server's single sign-on, with a code

The sign-in screen asks the server how it can be signed in to (GET /api/auth/config) and offers what it finds: the password form, and "Sign in with <provider>" when the server can do a device login. The TUI shows a link and a short code, the person approves it in any browser, and the next poll hands over the ordinary session, so it works over SSH where no browser can be opened. The terminal never talks to the identity provider. The password form is hidden when the server has turned password login off. `auth: sso` in config.yaml starts the SSO login straight away, but not right after signing out, where that would sign the person straight back in; any other value is refused when the config is read. Polling honours the server's interval, backs off on slow_down, and gives up after repeated failures rather than retrying forever. A server without /api/auth/config answers 404 and is treated as passwords only, so the sign-in screen is the one it had. Needs terdut-server v0.29.0 for SSO.
2026-09-26 21:47:13 +02:00
parent 057302cb39
commit ee25552a53
11 changed files with 970 additions and 12 deletions
@@ -79,6 +79,98 @@ func (c *Client) Login(username, password string) (string, error) {
 	return "", fmt.Errorf("server signed us in but sent no %s cookie", SessionCookie)
 }

+// AuthConfig asks how the server can be signed in to. It is unauthenticated, so
+// it works before anybody has signed in.
+func (c *Client) AuthConfig() (AuthConfig, error) {
+	var cfg AuthConfig
+	req, err := http.NewRequest(http.MethodGet, c.baseURL+"/api/auth/config", nil)
+	if err != nil {
+		return cfg, err
+	}
+	req.Header.Set("Accept", "application/json")
+	err = c.do(req, &cfg)
+	return cfg, err
+}
+
+// The ways a device login poll can end other than with a session.
+var (
+	// ErrDevicePending means nobody has approved yet: poll again after the
+	// interval.
+	ErrDevicePending = errors.New("waiting for approval")
+
+	// ErrDeviceSlowDown means the server was polled faster than it asked. It is
+	// not a failure; poll again, a little slower.
+	ErrDeviceSlowDown = errors.New("polling too fast")
+
+	// ErrDeviceExpired means the person took too long, or the server forgot the
+	// login. ErrDeviceDenied means they refused it.
+	ErrDeviceExpired = errors.New("the sign-in expired")
+	ErrDeviceDenied  = errors.New("the sign-in was refused")
+)
+
+// StartDeviceLogin asks the server to begin a device login.
+func (c *Client) StartDeviceLogin() (*DeviceLogin, error) {
+	req, err := c.newRequestWithBody(http.MethodPost, "/api/oidc/device", struct{}{})
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Del("Cookie")
+	var d DeviceLogin
+	if err := c.do(req, &d); err != nil {
+		return nil, err
+	}
+	if d.DeviceCode == "" || d.UserCode == "" || d.VerificationURL == "" {
+		return nil, errors.New("server started a sign-in but sent no code")
+	}
+	return &d, nil
+}
+
+// PollDeviceLogin asks whether the person has approved. On approval it returns
+// the session token, which the client also keeps; until then it returns one of
+// the ErrDevice* errors.
+func (c *Client) PollDeviceLogin(deviceCode string) (string, error) {
+	req, err := c.newRequestWithBody(http.MethodPost, "/api/oidc/device/token",
+		struct {
+			DeviceCode string `json:"device_code"`
+		}{deviceCode})
+	if err != nil {
+		return "", err
+	}
+	req.Header.Del("Cookie")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	switch resp.StatusCode {
+	case http.StatusAccepted:
+		return "", ErrDevicePending
+	case http.StatusTooManyRequests:
+		return "", ErrDeviceSlowDown
+	case http.StatusGone:
+		var e struct {
+			Error string `json:"error"`
+		}
+		_ = json.NewDecoder(resp.Body).Decode(&e)
+		if e.Error == "denied" {
+			return "", ErrDeviceDenied
+		}
+		return "", ErrDeviceExpired
+	}
+	if resp.StatusCode >= 400 {
+		return "", statusError(resp)
+	}
+	for _, ck := range resp.Cookies() {
+		if ck.Name == SessionCookie && ck.Value != "" {
+			c.session = ck.Value
+			return ck.Value, nil
+		}
+	}
+	return "", fmt.Errorf("server signed us in but sent no %s cookie", SessionCookie)
+}
+
 // Logout ends the session on the server and forgets it here.
 func (c *Client) Logout() error {
 	req, err := c.newRequest(http.MethodPost, "/api/logout")
@@ -584,3 +584,106 @@ func TestClient_StatusErrorKeepsCodeAndMessage(t *testing.T) {
 		t.Errorf("message changed: %q", err.Error())
 	}
 }
+
+func TestAuthConfig_ReadsWhatTheServerOffers(t *testing.T) {
+	c, got := stub(t, http.StatusOK,
+		`{"password_login":false,"oidc":{"enabled":true,"name":"Authentik"},"device_login":true}`)
+	cfg, err := c.AuthConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.method != http.MethodGet || got.path != "/api/auth/config" {
+		t.Errorf("wrong request: %s %s", got.method, got.path)
+	}
+	if cfg.PasswordLogin || !cfg.OIDC.Enabled || cfg.OIDC.Name != "Authentik" || !cfg.DeviceLogin {
+		t.Errorf("config: %+v", cfg)
+	}
+}
+
+func TestAuthConfig_OldServerAnswers404(t *testing.T) {
+	c, _ := stub(t, http.StatusNotFound, `{"error":"not found"}`)
+	_, err := c.AuthConfig()
+	var se *StatusError
+	if !errors.As(err, &se) || se.Code != http.StatusNotFound {
+		t.Errorf("want a 404 StatusError, got %v", err)
+	}
+}
+
+func TestStartDeviceLogin_SendsNoSessionAndReturnsTheCodes(t *testing.T) {
+	c, got := stub(t, http.StatusOK, `{"device_code":"dev","user_code":"BCDF-GHJK",
+		"verification_url":"https://terdut.example.com/device?code=BCDF-GHJK","interval":5,"expires_in":600}`)
+	d, err := c.StartDeviceLogin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.method != http.MethodPost || got.path != "/api/oidc/device" {
+		t.Errorf("wrong request: %s %s", got.method, got.path)
+	}
+	// A stale session must not ride along on a request that replaces it.
+	if got.cookie != "" {
+		t.Errorf("sent the old session %q", got.cookie)
+	}
+	if d.DeviceCode != "dev" || d.UserCode != "BCDF-GHJK" || d.Interval != 5 || d.ExpiresIn != 600 ||
+		d.VerificationURL != "https://terdut.example.com/device?code=BCDF-GHJK" {
+		t.Errorf("login: %+v", d)
+	}
+}
+
+func TestStartDeviceLogin_AReplyWithoutCodesIsAnError(t *testing.T) {
+	c, _ := stub(t, http.StatusOK, `{}`)
+	if _, err := c.StartDeviceLogin(); err == nil {
+		t.Error("an empty reply must not be taken for a started login")
+	}
+}
+
+func TestPollDeviceLogin_Outcomes(t *testing.T) {
+	for _, tc := range []struct {
+		name   string
+		status int
+		body   string
+		want   error
+	}{
+		{"pending", http.StatusAccepted, `{"status":"pending"}`, ErrDevicePending},
+		{"slow down", http.StatusTooManyRequests, `{"error":"slow_down"}`, ErrDeviceSlowDown},
+		{"expired", http.StatusGone, `{"error":"expired"}`, ErrDeviceExpired},
+		{"denied", http.StatusGone, `{"error":"denied"}`, ErrDeviceDenied},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			c, got := stub(t, tc.status, tc.body)
+			tok, err := c.PollDeviceLogin("dev")
+			if !errors.Is(err, tc.want) || tok != "" {
+				t.Errorf("got %q, %v; want %v", tok, err, tc.want)
+			}
+			if got.path != "/api/oidc/device/token" || !strings.Contains(got.body, `"device_code":"dev"`) {
+				t.Errorf("wrong request: %s %s", got.path, got.body)
+			}
+			if c.HasSession() && c.session == "" {
+				t.Error("session state corrupted")
+			}
+		})
+	}
+}
+
+func TestPollDeviceLogin_ApprovalKeepsTheSessionFromTheCookie(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.SetCookie(w, &http.Cookie{Name: SessionCookie, Value: "granted"})
+		io.WriteString(w, `{"user":{}}`)
+	}))
+	t.Cleanup(srv.Close)
+	c := NewClient(srv.URL)
+	tok, err := c.PollDeviceLogin("dev")
+	if err != nil || tok != "granted" {
+		t.Fatalf("got %q, %v", tok, err)
+	}
+	if !c.HasSession() {
+		t.Error("the client must keep the session it was given")
+	}
+}
+
+func TestPollDeviceLogin_ApprovalWithoutACookieIsAnError(t *testing.T) {
+	c, _ := stub(t, http.StatusOK, `{"user":{}}`)
+	c.SetSession("")
+	if _, err := c.PollDeviceLogin("dev"); err == nil {
+		t.Error("a 200 with no session cookie is not a sign-in")
+	}
+}
@@ -32,6 +32,35 @@ type Alert struct {
 	ResolutionSource *string `json:"resolution_source,omitempty"`
 }

+// AuthConfig is how the server can be signed in to, from the unauthenticated
+// GET /api/auth/config. A server too old to have the endpoint answers 404, which
+// callers treat as "passwords only".
+type AuthConfig struct {
+	PasswordLogin bool `json:"password_login"`
+	OIDC          struct {
+		Enabled bool   `json:"enabled"`
+		Name    string `json:"name"`
+	} `json:"oidc"`
+
+	// DeviceLogin is whether the server can sign in a client that has no browser,
+	// by showing a code (see StartDeviceLogin).
+	DeviceLogin bool `json:"device_login"`
+}
+
+// DeviceLogin is a sign-in the server has started for this client: the person
+// opens VerificationURL, checks UserCode, and approves; the client polls with
+// DeviceCode until the server hands over a session.
+type DeviceLogin struct {
+	DeviceCode      string `json:"device_code"`
+	UserCode        string `json:"user_code"`
+	VerificationURL string `json:"verification_url"`
+
+	// Interval is how many seconds to wait between polls, and ExpiresIn how many
+	// the person has to approve.
+	Interval  int `json:"interval"`
+	ExpiresIn int `json:"expires_in"`
+}
+
 // Incident statuses.
 const (
 	StatusTriggered    = "triggered"