app: integrate bwrap into environment setup

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

internal/app/config.go

@@ -24,9 +24,7 @@ type Config struct {
 // ConfinementConfig defines fortified child's confinement
 type ConfinementConfig struct {
 	// bwrap sandbox confinement configuration
-	Sandbox *bwrap.Config `json:"sandbox"`
-	// mediated access to wayland socket
-	Wayland bool `json:"wayland"`
+	Sandbox *SandboxConfig `json:"sandbox"`
 
 	// reference to a system D-Bus proxy configuration,
 	// nil value disables system bus proxy
@@ -38,3 +36,56 @@ type ConfinementConfig struct {
 	// child capability enablements
 	Enablements state.Enablements `json:"enablements"`
 }
+
+// SandboxConfig describes resources made available to the sandbox.
+type SandboxConfig struct {
+	// unix hostname within sandbox
+	Hostname string `json:"hostname,omitempty"`
+	// userns availability within sandbox
+	UserNS bool `json:"userns,omitempty"`
+	// share net namespace
+	Net bool `json:"net,omitempty"`
+	// do not run in new session
+	NoNewSession bool `json:"no_new_session,omitempty"`
+	// mediated access to wayland socket
+	Wayland bool `json:"wayland,omitempty"`
+
+	UID int `json:"uid,omitempty"`
+	GID int `json:"gid,omitempty"`
+	// final environment variables
+	Env map[string]string `json:"env"`
+
+	// paths made available within the sandbox
+	Bind [][2]string `json:"bind"`
+	// paths made available read-only within the sandbox
+	ROBind [][2]string `json:"ro-bind"`
+}
+
+func (s *SandboxConfig) Bwrap() *bwrap.Config {
+	if s == nil {
+		return nil
+	}
+
+	conf := &bwrap.Config{
+		Net:           s.Net,
+		UserNS:        s.UserNS,
+		Hostname:      s.Hostname,
+		Clearenv:      true,
+		SetEnv:        s.Env,
+		Bind:          s.Bind,
+		ROBind:        s.ROBind,
+		Procfs:        []string{"/proc"},
+		DevTmpfs:      []string{"/dev"},
+		Mqueue:        []string{"/dev/mqueue"},
+		NewSession:    !s.NoNewSession,
+		DieWithParent: true,
+	}
+	if s.UID > 0 {
+		conf.UID = &s.UID
+	}
+	if s.GID > 0 {
+		conf.GID = &s.GID
+	}
+
+	return conf
+}