gitlab: support for group whitelist

Documentation/connectors/gitlab.md

@@ -28,4 +28,9 @@ connectors:
       clientID: $GITLAB_APPLICATION_ID
       clientSecret: $GITLAB_CLIENT_SECRET
       redirectURI: http://127.0.0.1:5556/dex/callback
+      # Optional groups whitelist, communicated through the "groups" scope.
+      # If `groups` is omitted, all of the user's GitLab groups are returned when the groups scope is present.
+      # If `groups` is provided, this acts as a whitelist - only the user's GitLab groups that are in the configured `groups` below will go into the groups claim.  Conversely, if the user is not in any of the configured `groups`, the user will not be authenticated.
+      groups:
+      - my-group
 ```

connector/gitlab/gitlab.go

@@ -30,6 +30,7 @@ type Config struct {
 	ClientID     string   `json:"clientID"`
 	ClientSecret string   `json:"clientSecret"`
 	RedirectURI  string   `json:"redirectURI"`
+	Groups       []string `json:"groups"`
 }
 
 type gitlabUser struct {
@@ -52,6 +53,7 @@ func (c *Config) Open(id string, logger log.Logger) (connector.Connector, error)
 		clientID:     c.ClientID,
 		clientSecret: c.ClientSecret,
 		logger:       logger,
+		groups:       c.Groups,
 	}, nil
 }
 
@@ -68,7 +70,7 @@ var (
 type gitlabConnector struct {
 	baseURL      string
 	redirectURI  string
-	org          string
+	groups       []string
 	clientID     string
 	clientSecret string
 	logger       log.Logger
@@ -142,7 +144,7 @@ func (c *gitlabConnector) HandleCallback(s connector.Scopes, r *http.Request) (i
 	}
 
 	if s.Groups {
-		groups, err := c.groups(ctx, client)
+		groups, err := c.getGroups(ctx, client, s.Groups, user.Username)
 		if err != nil {
 			return identity, fmt.Errorf("gitlab: get groups: %v", err)
 		}
@@ -185,7 +187,7 @@ func (c *gitlabConnector) Refresh(ctx context.Context, s connector.Scopes, ident
 	ident.Email = user.Email
 
 	if s.Groups {
-		groups, err := c.groups(ctx, client)
+		groups, err := c.getGroups(ctx, client, s.Groups, user.Username)
 		if err != nil {
 			return ident, fmt.Errorf("gitlab: get groups: %v", err)
 		}
@@ -224,11 +226,11 @@ func (c *gitlabConnector) user(ctx context.Context, client *http.Client) (gitlab
 	return u, nil
 }
 
-// groups queries the GitLab API for group membership.
+// userGroups queries the GitLab API for group membership.
 //
 // The HTTP passed client is expected to be constructed by the golang.org/x/oauth2 package,
 // which inserts a bearer token as part of the request.
-func (c *gitlabConnector) groups(ctx context.Context, client *http.Client) ([]string, error) {
+func (c *gitlabConnector) userGroups(ctx context.Context, client *http.Client) ([]string, error) {
 	req, err := http.NewRequest("GET", c.baseURL+"/oauth/userinfo", nil)
 	if err != nil {
 		return nil, fmt.Errorf("gitlab: new req: %v", err)
@@ -256,3 +258,37 @@ func (c *gitlabConnector) groups(ctx context.Context, client *http.Client) ([]st
 
 	return u.Groups, nil
 }
+
+func (c *gitlabConnector) getGroups(ctx context.Context, client *http.Client, groupScope bool, userLogin string) ([]string, error) {
+	gitlabGroups, err := c.userGroups(ctx, client)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(c.groups) > 0 {
+		filteredGroups := filterGroups(gitlabGroups, c.groups)
+		if len(filteredGroups) == 0 {
+			return nil, fmt.Errorf("gitlab: user %q is not in any of the required groups", userLogin)
+		}
+		return filteredGroups, nil
+	} else if groupScope {
+		return gitlabGroups, nil
+	}
+
+	return nil, nil
+}
+
+// Filter the users' group memberships by 'groups' from config.
+func filterGroups(userGroups, configGroups []string) []string {
+	groups := []string{}
+	groupFilter := make(map[string]struct{})
+	for _, group := range configGroups {
+		groupFilter[group] = struct{}{}
+	}
+	for _, group := range userGroups {
+		if _, ok := groupFilter[group]; ok {
+			groups = append(groups, group)
+		}
+	}
+	return groups
+}