hst/container: pack boolean options

The memory saving is relatively insignificant, however this increases serialisation efficiency.

Signed-off-by: Ophestra <cat@gensokyo.uk>

4 files changed, 244 insertions, 51 deletions

diff --git a/hst/container.go b/hst/container.go
index ca75c17b..69909389 100644
--- a/hst/container.go
+++ b/hst/container.go
@@ -1,6 +1,8 @@
 package hst
 
 import (
+	"encoding/json"
+	"syscall"
 	"time"
 
 	"hakurei.app/container/check"
@@ -29,6 +31,37 @@ const (
 	ShimExitOrphan = 3
 )
 
+const (
+	// FMultiarch unblocks syscalls required for multiarch to work on applicable targets.
+	FMultiarch uintptr = 1 << iota
+
+	// FSeccompCompat causes emitted seccomp filter programs to be identical to Flatpak.
+	FSeccompCompat
+	// FDevel unblocks ptrace and friends.
+	FDevel
+	// FUserns unblocks userns creation and container setup syscalls.
+	FUserns
+	// FHostNet skips net namespace creation.
+	FHostNet
+	// FHostAbstract skips setting up abstract unix socket scope.
+	FHostAbstract
+	// FTty unblocks dangerous terminal I/O (faking input).
+	FTty
+
+	// FMapRealUID maps the target user uid to the privileged user uid in the container user namespace.
+	//	Some programs fail to connect to dbus session running as a different uid,
+	//	this option works around it by mapping priv-side caller uid in container.
+	FMapRealUID
+
+	// FDevice mount /dev/ from the init mount namespace as-is in the container mount namespace.
+	FDevice
+
+	fMax
+
+	// FAll is [ContainerConfig.Flags] with all currently defined bits set.
+	FAll = fMax - 1
+)
+
 // ContainerConfig describes the container configuration to be applied to an underlying [container].
 type ContainerConfig struct {
 	// Container UTS namespace hostname.
@@ -39,33 +72,9 @@ type ContainerConfig struct {
 	// Values lesser than zero is equivalent to zero, bypassing [WaitDelayDefault].
 	WaitDelay time.Duration `json:"wait_delay,omitempty"`
 
-	// Emit Flatpak-compatible seccomp filter programs.
-	SeccompCompat bool `json:"seccomp_compat,omitempty"`
-	// Allow ptrace and friends.
-	Devel bool `json:"devel,omitempty"`
-	// Allow userns creation and container setup syscalls.
-	Userns bool `json:"userns,omitempty"`
-	// Share host net namespace.
-	HostNet bool `json:"host_net,omitempty"`
-	// Share abstract unix socket scope.
-	HostAbstract bool `json:"host_abstract,omitempty"`
-	// Allow dangerous terminal I/O (faking input).
-	Tty bool `json:"tty,omitempty"`
-	// Allow multiarch.
-	Multiarch bool `json:"multiarch,omitempty"`
-
 	// Initial process environment variables.
 	Env map[string]string `json:"env"`
 
-	/* Map target user uid to privileged user uid in the container user namespace.
-
-	Some programs fail to connect to dbus session running as a different uid,
-	this option works around it by mapping priv-side caller uid in container. */
-	MapRealUID bool `json:"map_real_uid"`
-
-	// Mount /dev/ from the init mount namespace as-is in the container mount namespace.
-	Device bool `json:"device,omitempty"`
-
 	/* Container mount points.
 
 	If the first element targets /, it is inserted early and excluded from path hiding. */
@@ -83,4 +92,98 @@ type ContainerConfig struct {
 	Path *check.Absolute `json:"path,omitempty"`
 	// Final args passed to the initial program.
 	Args []string `json:"args"`
+
+	// Flags holds boolean options of [ContainerConfig].
+	Flags uintptr `json:"-"`
+}
+
+// ContainerConfigF is [ContainerConfig] stripped of its methods.
+// The [ContainerConfig.Flags] field does not survive a [json] round trip.
+type ContainerConfigF ContainerConfig
+
+// containerConfigJSON is the [json] representation of [ContainerConfig].
+type containerConfigJSON = struct {
+	*ContainerConfigF
+
+	// Corresponds to [FSeccompCompat].
+	SeccompCompat bool `json:"seccomp_compat,omitempty"`
+	// Corresponds to [FDevel].
+	Devel bool `json:"devel,omitempty"`
+	// Corresponds to [FUserns].
+	Userns bool `json:"userns,omitempty"`
+	// Corresponds to [FHostNet].
+	HostNet bool `json:"host_net,omitempty"`
+	// Corresponds to [FHostAbstract].
+	HostAbstract bool `json:"host_abstract,omitempty"`
+	// Corresponds to [FTty].
+	Tty bool `json:"tty,omitempty"`
+
+	// Corresponds to [FMultiarch].
+	Multiarch bool `json:"multiarch,omitempty"`
+
+	// Corresponds to [FMapRealUID].
+	MapRealUID bool `json:"map_real_uid"`
+
+	// Corresponds to [FDevice].
+	Device bool `json:"device,omitempty"`
+}
+
+func (c *ContainerConfig) MarshalJSON() ([]byte, error) {
+	if c == nil {
+		return nil, syscall.EINVAL
+	}
+	return json.Marshal(&containerConfigJSON{
+		ContainerConfigF: (*ContainerConfigF)(c),
+
+		SeccompCompat: c.Flags&FSeccompCompat != 0,
+		Devel:         c.Flags&FDevel != 0,
+		Userns:        c.Flags&FUserns != 0,
+		HostNet:       c.Flags&FHostNet != 0,
+		HostAbstract:  c.Flags&FHostAbstract != 0,
+		Tty:           c.Flags&FTty != 0,
+		Multiarch:     c.Flags&FMultiarch != 0,
+		MapRealUID:    c.Flags&FMapRealUID != 0,
+		Device:        c.Flags&FDevice != 0,
+	})
+}
+
+func (c *ContainerConfig) UnmarshalJSON(data []byte) error {
+	if c == nil {
+		return syscall.EINVAL
+	}
+
+	v := new(containerConfigJSON)
+	if err := json.Unmarshal(data, &v); err != nil {
+		return err
+	}
+
+	*c = *(*ContainerConfig)(v.ContainerConfigF)
+	if v.SeccompCompat {
+		c.Flags |= FSeccompCompat
+	}
+	if v.Devel {
+		c.Flags |= FDevel
+	}
+	if v.Userns {
+		c.Flags |= FUserns
+	}
+	if v.HostNet {
+		c.Flags |= FHostNet
+	}
+	if v.HostAbstract {
+		c.Flags |= FHostAbstract
+	}
+	if v.Tty {
+		c.Flags |= FTty
+	}
+	if v.Multiarch {
+		c.Flags |= FMultiarch
+	}
+	if v.MapRealUID {
+		c.Flags |= FMapRealUID
+	}
+	if v.Device {
+		c.Flags |= FDevice
+	}
+	return nil
 }
diff --git a/hst/container_test.go b/hst/container_test.go
new file mode 100644
index 00000000..049d3540
--- /dev/null
+++ b/hst/container_test.go
@@ -0,0 +1,76 @@
+package hst_test
+
+import (
+	"encoding/json"
+	"errors"
+	"reflect"
+	"syscall"
+	"testing"
+
+	"hakurei.app/hst"
+)
+
+func TestContainerConfig(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name string
+		c    *hst.ContainerConfig
+		data string
+	}{
+		{"nil", nil, "null"},
+		{"zero", new(hst.ContainerConfig),
+			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"map_real_uid":false}`},
+		{"seccomp compat", &hst.ContainerConfig{Flags: hst.FSeccompCompat},
+			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"seccomp_compat":true,"map_real_uid":false}`},
+		{"hostnet hostabstract", &hst.ContainerConfig{Flags: hst.FHostNet | hst.FHostAbstract},
+			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"host_net":true,"host_abstract":true,"map_real_uid":false}`},
+		{"hostnet hostabstract mapuid", &hst.ContainerConfig{Flags: hst.FHostNet | hst.FHostAbstract | hst.FMapRealUID},
+			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"host_net":true,"host_abstract":true,"map_real_uid":true}`},
+		{"all", &hst.ContainerConfig{Flags: hst.FAll},
+			`{"env":null,"filesystem":null,"shell":null,"home":null,"args":null,"seccomp_compat":true,"devel":true,"userns":true,"host_net":true,"host_abstract":true,"tty":true,"multiarch":true,"map_real_uid":true,"device":true}`},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			t.Run("marshal", func(t *testing.T) {
+				t.Parallel()
+				if got, err := json.Marshal(tc.c); err != nil {
+					t.Fatalf("Marshal: error = %v", err)
+				} else if string(got) != tc.data {
+					t.Errorf("Marshal:\n%s, want\n%s", string(got), tc.data)
+				}
+			})
+
+			t.Run("unmarshal", func(t *testing.T) {
+				t.Parallel()
+
+				{
+					got := new(hst.ContainerConfig)
+					if err := json.Unmarshal([]byte(tc.data), &got); err != nil {
+						t.Fatalf("Unmarshal: error = %v", err)
+					}
+					if !reflect.DeepEqual(got, tc.c) {
+						t.Errorf("Unmarshal: %v, want %v", got, tc.c)
+					}
+				}
+			})
+		})
+	}
+
+	t.Run("passthrough", func(t *testing.T) {
+		t.Parallel()
+
+		if _, err := (*hst.ContainerConfig)(nil).MarshalJSON(); !errors.Is(err, syscall.EINVAL) {
+			t.Errorf("MarshalJSON: error = %v", err)
+		}
+		if err := (*hst.ContainerConfig)(nil).UnmarshalJSON(nil); !errors.Is(err, syscall.EINVAL) {
+			t.Errorf("UnmarshalJSON: error = %v", err)
+		}
+		if err := new(hst.ContainerConfig).UnmarshalJSON([]byte{}); err == nil {
+			t.Errorf("UnmarshalJSON: error = %v", err)
+		}
+	})
+}
diff --git a/hst/hst.go b/hst/hst.go
index 11e91e7b..11b2b279 100644
--- a/hst/hst.go
+++ b/hst/hst.go
@@ -3,6 +3,7 @@ package hst
 
 import (
 	"errors"
+	"math"
 	"net"
 	"os"
 
@@ -96,17 +97,8 @@ func Template() *Config {
 		Groups:   []string{"video", "dialout", "plugdev"},
 
 		Container: &ContainerConfig{
-			Hostname:      "localhost",
-			Devel:         true,
-			Userns:        true,
-			HostNet:       true,
-			HostAbstract:  true,
-			Device:        true,
-			WaitDelay:     -1,
-			SeccompCompat: true,
-			Tty:           true,
-			Multiarch:     true,
-			MapRealUID:    true,
+			Hostname:  "localhost",
+			WaitDelay: -1,
 			// example API credentials pulled from Google Chrome
 			// DO NOT USE THESE IN A REAL BROWSER
 			Env: map[string]string{
@@ -143,6 +135,9 @@ func Template() *Config {
 				"--enable-features=UseOzonePlatform",
 				"--ozone-platform=wayland",
 			},
+
+			// Set all bits here so new flags trip the template test.
+			Flags: math.MaxUint,
 		},
 	}
 }
diff --git a/hst/hst_test.go b/hst/hst_test.go
index 8bca8d6e..0dd74886 100644
--- a/hst/hst_test.go
+++ b/hst/hst_test.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"net"
 	"os"
+	"reflect"
 	"syscall"
 	"testing"
 
@@ -164,20 +165,11 @@ func TestTemplate(t *testing.T) {
 	"container": {
 		"hostname": "localhost",
 		"wait_delay": -1,
-		"seccomp_compat": true,
-		"devel": true,
-		"userns": true,
-		"host_net": true,
-		"host_abstract": true,
-		"tty": true,
-		"multiarch": true,
 		"env": {
 			"GOOGLE_API_KEY": "AIzaSyBHDrl33hwRp4rMQY0ziRbj8K9LPA6vUCY",
 			"GOOGLE_DEFAULT_CLIENT_ID": "77185425430.apps.googleusercontent.com",
 			"GOOGLE_DEFAULT_CLIENT_SECRET": "OTJgUOQcT7lO7GsGZq2G4IlT"
 		},
-		"map_real_uid": true,
-		"device": true,
 		"filesystem": [
 			{
 				"type": "bind",
@@ -243,14 +235,41 @@ func TestTemplate(t *testing.T) {
 			"--disable-smooth-scrolling",
 			"--enable-features=UseOzonePlatform",
 			"--ozone-platform=wayland"
-		]
+		],
+		"seccomp_compat": true,
+		"devel": true,
+		"userns": true,
+		"host_net": true,
+		"host_abstract": true,
+		"tty": true,
+		"multiarch": true,
+		"map_real_uid": true,
+		"device": true
 	}
 }`
 
-	if p, err := json.MarshalIndent(hst.Template(), "", "\t"); err != nil {
-		t.Fatalf("cannot marshal: %v", err)
-	} else if s := string(p); s != want {
-		t.Fatalf("Template:\n%s\nwant:\n%s",
-			s, want)
-	}
+	t.Run("marshal", func(t *testing.T) {
+		t.Parallel()
+		if p, err := json.MarshalIndent(hst.Template(), "", "\t"); err != nil {
+			t.Fatalf("cannot marshal: %v", err)
+		} else if s := string(p); s != want {
+			t.Fatalf("Template:\n%s\nwant:\n%s",
+				s, want)
+		}
+	})
+
+	t.Run("unmarshal", func(t *testing.T) {
+		t.Parallel()
+
+		var got *hst.Config
+		if err := json.Unmarshal([]byte(want), &got); err != nil {
+			t.Fatalf("Unmarshal: error = %v", err)
+		}
+
+		wantVal := hst.Template()
+		wantVal.Container.Flags = hst.FAll
+		if !reflect.DeepEqual(got, wantVal) {
+			t.Fatalf("Unmarshal: %#v, want %#v", got, wantVal)
+		}
+	})
 }