connector: add uaa connector

This commit adds support for dex to authenticate users from a
CloudFoundry User Account and Authentication (UAA) Server.

Fixes: #538

Documentation/connectors-configuration.md

@@ -237,3 +237,38 @@ To set a connectors configuration in dex, put it in some temporary file, then us
 ```
 dexctl --db-url=$DEX_DB_URL set-connector-configs /tmp/dex_connectors.json
 ```
+
+### `uaa` connector
+
+This connector config lets users authenticate through the
+[CloudFoundry User Account and Authentication (UAA) Server](https://github.com/cloudfoundry/uaa). In addition to `id`
+and `type`, the `uaa` connector takes the following additional fields:
+
+* clientID: a `string`. The UAA OAuth application client ID.
+* clientSecret: a `string`. The UAA OAuth application client secret.
+* serverURL: a `string`. The full URL to the UAA service.
+
+To begin, register an OAuth application with UAA. To register dex as a client of your UAA application, there are two
+things your OAuth application needs to have configured properly:
+
+* Make sure dex's redirect URL _(`ISSUER_URL/auth/$CONNECTOR_ID/callback`)_ is in the application's `redirect_uri` list
+* Make sure the `openid` scope is in the application's `scope` list
+
+Regarding the `redirect_uri` list, as an example if you were running dex at `https://auth.example.com/bar`, the UAA
+OAuth application's `redirect_uri` list would need to contain `https://auth.example.com/bar/auth/uaa/callback`.
+
+Here's an example of a `uaa` connector _(The `clientID` and `clientSecret` should be replaced by values provided to UAA
+and the `serverURL` should be the fully-qualified URL to your UAA server)_:
+
+```
+    {
+        "type": "uaa",
+        "id": "example-uaa",
+        "clientID": "$UAA_OAUTH_APPLICATION_CLIENT_ID",
+        "clientSecret": "$UAA_OAUTH_APPLICATION_CLIENT_SECRET",
+        "serverURL": "$UAA_SERVER_URL"
+    }
+```
+
+The `uaa` connector requests only the `openid` scope which allows dex the ability to query the user's identity
+information.

connector/connector_uaa.go

+package connector
+
+import (
+	"encoding/json"
+	"fmt"
+	"html/template"
+	"net/http"
+	"net/url"
+	"path"
+
+	chttp "github.com/coreos/go-oidc/http"
+	"github.com/coreos/go-oidc/oauth2"
+	"github.com/coreos/go-oidc/oidc"
+)
+
+const (
+	UAAConnectorType = "uaa"
+)
+
+type UAAConnectorConfig struct {
+	ID           string `json:"id"`
+	ClientID     string `json:"clientID"`
+	ClientSecret string `json:"clientSecret"`
+	ServerURL    string `json:"serverURL"`
+}
+
+// standard error form returned by UAA
+type uaaError struct {
+	ErrorDescription string `json:"error_description"`
+	ErrorType        string `json:"error"`
+}
+
+type uaaOAuth2Connector struct {
+	clientID     string
+	clientSecret string
+	client       *oauth2.Client
+	uaaBaseURL   *url.URL
+}
+
+func init() {
+	RegisterConnectorConfigType(UAAConnectorType, func() ConnectorConfig { return &UAAConnectorConfig{} })
+}
+
+func (cfg *UAAConnectorConfig) ConnectorID() string {
+	return cfg.ID
+}
+
+func (cfg *UAAConnectorConfig) ConnectorType() string {
+	return UAAConnectorType
+}
+
+func (cfg *UAAConnectorConfig) Connector(ns url.URL, lf oidc.LoginFunc, tpls *template.Template) (Connector, error) {
+	uaaBaseURL, err := url.ParseRequestURI(cfg.ServerURL)
+	if err != nil {
+		return nil, fmt.Errorf("Invalid configuration. UAA URL is invalid: %v", err)
+	}
+	if !uaaBaseURL.IsAbs() {
+		return nil, fmt.Errorf("Invalid configuration. UAA URL must be absolute")
+	}
+	ns.Path = path.Join(ns.Path, httpPathCallback)
+	oauth2Conn, err := newUAAConnector(cfg, uaaBaseURL, ns.String())
+	if err != nil {
+		return nil, err
+	}
+	return &OAuth2Connector{
+		id:        cfg.ID,
+		loginFunc: lf,
+		cbURL:     ns,
+		conn:      oauth2Conn,
+	}, nil
+}
+
+func (err uaaError) Error() string {
+	return fmt.Sprintf("uaa (%s): %s", err.ErrorType, err.ErrorDescription)
+}
+
+func (c *uaaOAuth2Connector) Client() *oauth2.Client {
+	return c.client
+}
+
+func (c *uaaOAuth2Connector) Healthy() error {
+	return nil
+}
+
+func (c *uaaOAuth2Connector) Identity(cli chttp.Client) (oidc.Identity, error) {
+	uaaUserInfoURL := *c.uaaBaseURL
+	uaaUserInfoURL.Path = path.Join(uaaUserInfoURL.Path, "/userinfo")
+	req, err := http.NewRequest("GET", uaaUserInfoURL.String(), nil)
+	if err != nil {
+		return oidc.Identity{}, err
+	}
+	resp, err := cli.Do(req)
+	if err != nil {
+		return oidc.Identity{}, fmt.Errorf("get: %v", err)
+	}
+	defer resp.Body.Close()
+	switch {
+	case resp.StatusCode >= 400 && resp.StatusCode < 600:
+		// attempt to decode error from UAA
+		var authErr uaaError
+		if err := json.NewDecoder(resp.Body).Decode(&authErr); err != nil {
+			return oidc.Identity{}, oauth2.NewError(oauth2.ErrorAccessDenied)
+		}
+		return oidc.Identity{}, authErr
+	case resp.StatusCode == http.StatusOK:
+	default:
+		return oidc.Identity{}, fmt.Errorf("unexpected status from providor %s", resp.Status)
+	}
+	var user struct {
+		UserID   string `json:"user_id"`
+		Email    string `json:"email"`
+		Name     string `json:"name"`
+		UserName string `json:"user_name"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&user); err != nil {
+		return oidc.Identity{}, fmt.Errorf("getting user info: %v", err)
+	}
+	name := user.Name
+	if name == "" {
+		name = user.UserName
+	}
+	return oidc.Identity{
+		ID:    user.UserID,
+		Name:  name,
+		Email: user.Email,
+	}, nil
+}
+
+func (c *uaaOAuth2Connector) TrustedEmailProvider() bool {
+	return false
+}
+
+func newUAAConnector(cfg *UAAConnectorConfig, uaaBaseURL *url.URL, cbURL string) (oauth2Connector, error) {
+	uaaAuthURL := *uaaBaseURL
+	uaaTokenURL := *uaaBaseURL
+	uaaAuthURL.Path = path.Join(uaaAuthURL.Path, "/oauth/authorize")
+	uaaTokenURL.Path = path.Join(uaaTokenURL.Path, "/oauth/token")
+	config := oauth2.Config{
+		Credentials: oauth2.ClientCredentials{ID: cfg.ClientID, Secret: cfg.ClientSecret},
+		AuthURL:     uaaAuthURL.String(),
+		TokenURL:    uaaTokenURL.String(),
+		Scope:       []string{"openid"},
+		AuthMethod:  oauth2.AuthMethodClientSecretPost,
+		RedirectURL: cbURL,
+	}
+
+	cli, err := oauth2.NewClient(http.DefaultClient, config)
+	if err != nil {
+		return nil, err
+	}
+
+	return &uaaOAuth2Connector{
+		clientID:     cfg.ClientID,
+		clientSecret: cfg.ClientSecret,
+		client:       cli,
+		uaaBaseURL:   uaaBaseURL,
+	}, nil
+}

connector/connector_uaa_test.go

+package connector
+
+import (
+	"testing"
+)
+
+func TestUAAConnectorConfigInvalidserverURLNotAValidURL(t *testing.T) {
+	cc := UAAConnectorConfig{
+		ID:           "uaa",
+		ClientID:     "test-client",
+		ClientSecret: "test-client-secret",
+		ServerURL:    "https//login.apigee.com",
+	}
+
+	_, err := cc.Connector(ns, lf, templates)
+	if err == nil {
+		t.Fatal("Expected UAAConnector initialization to fail when UAA URL is an invalid URL")
+	}
+}
+
+func TestUAAConnectorConfigInvalidserverURLNotAbsolute(t *testing.T) {
+	cc := UAAConnectorConfig{
+		ID:           "uaa",
+		ClientID:     "test-client",
+		ClientSecret: "test-client-secret",
+		ServerURL:    "/uaa",
+	}
+
+	_, err := cc.Connector(ns, lf, templates)
+	if err == nil {
+		t.Fatal("Expected UAAConnector initialization to fail when UAA URL is not an aboslute URL")
+	}
+}
+
+func TestUAAConnectorConfigValidserverURL(t *testing.T) {
+	cc := UAAConnectorConfig{
+		ID:           "uaa",
+		ClientID:     "test-client",
+		ClientSecret: "test-client-secret",
+		ServerURL:    "https://login.apigee.com",
+	}
+
+	_, err := cc.Connector(ns, lf, templates)
+	if err != nil {
+		t.Fatal(err)
+	}
+}

server/http.go

@@ -131,6 +131,7 @@ var connectorDisplayNameMap = map[string]string{
 	"local":     "Email",
 	"github":    "GitHub",
 	"bitbucket": "Bitbucket",
+	"uaa":       "CloudFoundry User Account and Authentication (UAA)",
 }
 
 type Template interface {