feat: add ability to mount generated passwd files to containers (#197)

This PR will add an option to mount:
- `/etc/group`
- `/etc/passwd`

Signed-off-by: Matthew Penner <me@matthewp.io>

cmd/root.go

@@ -112,6 +112,9 @@ func rootCmdRun(cmd *cobra.Command, _ []string) {
 	if err := config.EnsurePterodactylUser(); err != nil {
 		log.WithField("error", err).Fatal("failed to create pterodactyl system user")
 	}
+	if err := config.ConfigurePasswd(); err != nil {
+		log.WithField("error", err).Fatal("failed to configure container passwd file")
+	}
 	log.WithFields(log.Fields{
 		"username": config.Get().System.Username,
 		"uid":      config.Get().System.User.Uid,

config/config.go

@@ -172,6 +172,25 @@ type SystemConfiguration struct {
 		Gid int `yaml:"gid"`
 	} `yaml:"user"`
 
+	// Passwd controls the mounting of a generated passwd files into containers started by Wings.
+	Passwd struct {
+		// Enable controls whether generated passwd files should be mounted into containers.
+		//
+		// By default this option is disabled and Wings will not mount any additional passwd
+		// files into containers.
+		Enable bool `yaml:"enabled" default:"false"`
+
+		// Directory is the directory on disk where the generated files will be stored.
+		// This directory may be temporary as it will be re-created whenever Wings is started.
+		//
+		// This path **WILL** be both written to by Wings and mounted into containers created by
+		// Wings. If you are running Wings itself in a container, this path will need to be mounted
+		// into the Wings container as the exact path on the host, which should match the value
+		// specified here. If you are using SELinux, you will need to make sure this file has the
+		// correct SELinux context in order for containers to use it.
+		Directory string `yaml:"directory" default:"/run/wings/etc"`
+	} `yaml:"passwd"`
+
 	// The amount of time in seconds that can elapse before a server's disk space calculation is
 	// considered stale and a re-check should occur. DANGER: setting this value too low can seriously
 	// impact system performance and cause massive I/O bottlenecks and high CPU usage for the Wings
@@ -497,6 +516,37 @@ func EnsurePterodactylUser() error {
 	return nil
 }
 
+// ConfigurePasswd generates required passwd files for use with containers started by Wings.
+func ConfigurePasswd() error {
+	passwd := _config.System.Passwd
+	if !passwd.Enable {
+		return nil
+	}
+
+	v := []byte(fmt.Sprintf(
+		`root:x:0:
+container:x:%d:
+nogroup:x:65534:`,
+		_config.System.User.Gid,
+	))
+	if err := os.WriteFile(filepath.Join(passwd.Directory, "group"), v, 0o644); err != nil {
+		return fmt.Errorf("failed to write file to %s/group: %v", passwd.Directory, err)
+	}
+
+	v = []byte(fmt.Sprintf(
+		`root:x:0:0::/root:/bin/sh
+container:x:%d:%d::/home/container:/bin/sh
+nobody:x:65534:65534::/var/empty:/bin/sh
+`,
+		_config.System.User.Uid,
+		_config.System.User.Gid,
+	))
+	if err := os.WriteFile(filepath.Join(passwd.Directory, "passwd"), v, 0o644); err != nil {
+		return fmt.Errorf("failed to write file to %s/passwd: %v", passwd.Directory, err)
+	}
+	return nil
+}
+
 // FromFile reads the configuration from the provided file and stores it in the
 // global singleton for this instance.
 func FromFile(path string) error {
@@ -561,6 +611,13 @@ func ConfigureDirectories() error {
 		return err
 	}
 
+	if _config.System.Passwd.Enable {
+		log.WithField("path", _config.System.Passwd.Directory).Debug("ensuring passwd directory exists")
+		if err := os.MkdirAll(_config.System.Passwd.Directory, 0o755); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 

server/mounts.go

@@ -29,6 +29,21 @@ func (s *Server) Mounts() []environment.Mount {
 		},
 	}
 
+	// Handle mounting a generated `/etc/passwd` if the feature is enabled.
+	if passwd := config.Get().System.Passwd; passwd.Enable {
+		s.Log().WithFields(log.Fields{"source_path": passwd.Directory}).Info("mouting generated /etc/{group,passwd} to workaround UID/GID issues")
+		m = append(m, environment.Mount{
+			Source:   filepath.Join(passwd.Directory, "group"),
+			Target:   "/etc/group",
+			ReadOnly: true,
+		})
+		m = append(m, environment.Mount{
+			Source:   filepath.Join(passwd.Directory, "passwd"),
+			Target:   "/etc/passwd",
+			ReadOnly: true,
+		})
+	}
+
 	// Also include any of this server's custom mounts when returning them.
 	return append(m, s.customMounts()...)
 }
@@ -56,14 +71,12 @@ func (s *Server) customMounts() []environment.Mount {
 			if !strings.HasPrefix(source, filepath.Clean(allowed)) {
 				continue
 			}
-
 			mounted = true
 			mounts = append(mounts, environment.Mount{
 				Source:   source,
 				Target:   target,
 				ReadOnly: m.ReadOnly,
 			})
-
 			break
 		}