container: optionally isolate host abstract UNIX domain sockets via landlock

container/container.go

@@ -189,11 +189,10 @@ func (p *Container) Start() error {
 
 			// landlock: depends on per-thread state but acts on a process group
 			{
-				scoped := LANDLOCK_SCOPE_SIGNAL
+				rulesetAttr := &RulesetAttr{Scoped: LANDLOCK_SCOPE_SIGNAL}
 				if !p.HostAbstract {
-					scoped |= LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET
+					rulesetAttr.Scoped |= LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET
 				}
-				rulesetAttr := NewRulesetAttr(scoped)
 
 				if abi, err := LandlockGetABI(); err != nil {
 					if p.HostAbstract {
@@ -214,12 +213,11 @@ func (p *Container) Start() error {
 					msg.Verbosef("landlock abi version %d", abi)
 				}
 
-				msg.Verbosef("creating landlock ruleset scoped %#x", int(scoped))
+				if rulesetFd, err := rulesetAttr.Create(0); err != nil {
-				if rulesetFd, err := LandlockCreateRuleset(&rulesetAttr, 0); err != nil {
 					return wrapErrSuffix(err,
 						"cannot create landlock ruleset:")
 				} else {
-					msg.Verbose("enforcing landlock ruleset")
+					msg.Verbosef("enforcing landlock ruleset %s", rulesetAttr)
 					if err = LandlockRestrictSelf(rulesetFd, 0); err != nil {
 						_ = Close(rulesetFd)
 						return wrapErrSuffix(err,

container/landlock.go

@@ -1,30 +1,210 @@
 package container
 
-/*
-#include <linux/landlock.h>
-#include <sys/syscall.h>
-*/
-import "C"
 import (
+	"strings"
 	"syscall"
 	"unsafe"
 
 	"hakurei.app/container/seccomp"
 )
 
+// include/uapi/linux/landlock.h
+
 const (
-	LANDLOCK_CREATE_RULESET_VERSION     = C.LANDLOCK_CREATE_RULESET_VERSION
+	LANDLOCK_CREATE_RULESET_VERSION = 1 << iota
-	LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET = C.LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET
-	LANDLOCK_SCOPE_SIGNAL               = C.LANDLOCK_SCOPE_SIGNAL
 )
 
-type RulesetAttr = C.struct_landlock_ruleset_attr
+type LandlockAccessFS uintptr
 
-func NewRulesetAttr(scoped int) RulesetAttr { return RulesetAttr{scoped: C.__u64(scoped)} }
+const (
+	LANDLOCK_ACCESS_FS_EXECUTE LandlockAccessFS = 1 << iota
+	LANDLOCK_ACCESS_FS_WRITE_FILE
+	LANDLOCK_ACCESS_FS_READ_FILE
+	LANDLOCK_ACCESS_FS_READ_DIR
+	LANDLOCK_ACCESS_FS_REMOVE_DIR
+	LANDLOCK_ACCESS_FS_REMOVE_FILE
+	LANDLOCK_ACCESS_FS_MAKE_CHAR
+	LANDLOCK_ACCESS_FS_MAKE_DIR
+	LANDLOCK_ACCESS_FS_MAKE_REG
+	LANDLOCK_ACCESS_FS_MAKE_SOCK
+	LANDLOCK_ACCESS_FS_MAKE_FIFO
+	LANDLOCK_ACCESS_FS_MAKE_BLOCK
+	LANDLOCK_ACCESS_FS_MAKE_SYM
+	LANDLOCK_ACCESS_FS_REFER
+	LANDLOCK_ACCESS_FS_TRUNCATE
+	LANDLOCK_ACCESS_FS_IOCTL_DEV
 
-/* TODO: remove everything above this */
+	_LANDLOCK_ACCESS_FS_DELIM
+)
 
-func LandlockCreateRuleset(rulesetAttr *RulesetAttr, flags uintptr) (fd int, err error) {
+func (f LandlockAccessFS) String() string {
+	switch f {
+	case LANDLOCK_ACCESS_FS_EXECUTE:
+		return "execute"
+
+	case LANDLOCK_ACCESS_FS_WRITE_FILE:
+		return "write_file"
+
+	case LANDLOCK_ACCESS_FS_READ_FILE:
+		return "read_file"
+
+	case LANDLOCK_ACCESS_FS_READ_DIR:
+		return "read_dir"
+
+	case LANDLOCK_ACCESS_FS_REMOVE_DIR:
+		return "remove_dir"
+
+	case LANDLOCK_ACCESS_FS_REMOVE_FILE:
+		return "remove_file"
+
+	case LANDLOCK_ACCESS_FS_MAKE_CHAR:
+		return "make_char"
+
+	case LANDLOCK_ACCESS_FS_MAKE_DIR:
+		return "make_dir"
+
+	case LANDLOCK_ACCESS_FS_MAKE_REG:
+		return "make_reg"
+
+	case LANDLOCK_ACCESS_FS_MAKE_SOCK:
+		return "make_sock"
+
+	case LANDLOCK_ACCESS_FS_MAKE_FIFO:
+		return "make_fifo"
+
+	case LANDLOCK_ACCESS_FS_MAKE_BLOCK:
+		return "make_block"
+
+	case LANDLOCK_ACCESS_FS_MAKE_SYM:
+		return "make_sym"
+
+	case LANDLOCK_ACCESS_FS_REFER:
+		return "fs_refer"
+
+	case LANDLOCK_ACCESS_FS_TRUNCATE:
+		return "fs_truncate"
+
+	case LANDLOCK_ACCESS_FS_IOCTL_DEV:
+		return "fs_ioctl_dev"
+
+	default:
+		var c []LandlockAccessFS
+		for i := LandlockAccessFS(1); i < _LANDLOCK_ACCESS_FS_DELIM; i <<= 1 {
+			if f&i != 0 {
+				c = append(c, i)
+			}
+		}
+		if len(c) == 0 {
+			return "NULL"
+		}
+		s := make([]string, len(c))
+		for i, v := range c {
+			s[i] = v.String()
+		}
+		return strings.Join(s, " ")
+	}
+}
+
+type LandlockAccessNet uintptr
+
+const (
+	LANDLOCK_ACCESS_NET_BIND_TCP LandlockAccessNet = 1 << iota
+	LANDLOCK_ACCESS_NET_CONNECT_TCP
+
+	_LANDLOCK_ACCESS_NET_DELIM
+)
+
+func (f LandlockAccessNet) String() string {
+	switch f {
+	case LANDLOCK_ACCESS_NET_BIND_TCP:
+		return "bind_tcp"
+
+	case LANDLOCK_ACCESS_NET_CONNECT_TCP:
+		return "connect_tcp"
+
+	default:
+		var c []LandlockAccessNet
+		for i := LandlockAccessNet(1); i < _LANDLOCK_ACCESS_NET_DELIM; i <<= 1 {
+			if f&i != 0 {
+				c = append(c, i)
+			}
+		}
+		if len(c) == 0 {
+			return "NULL"
+		}
+		s := make([]string, len(c))
+		for i, v := range c {
+			s[i] = v.String()
+		}
+		return strings.Join(s, " ")
+	}
+}
+
+type LandlockScope uintptr
+
+const (
+	LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET LandlockScope = 1 << iota
+	LANDLOCK_SCOPE_SIGNAL
+
+	_LANDLOCK_SCOPE_DELIM
+)
+
+func (f LandlockScope) String() string {
+	switch f {
+	case LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET:
+		return "abstract_unix_socket"
+
+	case LANDLOCK_SCOPE_SIGNAL:
+		return "signal"
+
+	default:
+		var c []LandlockScope
+		for i := LandlockScope(1); i < _LANDLOCK_SCOPE_DELIM; i <<= 1 {
+			if f&i != 0 {
+				c = append(c, i)
+			}
+		}
+		if len(c) == 0 {
+			return "NULL"
+		}
+		s := make([]string, len(c))
+		for i, v := range c {
+			s[i] = v.String()
+		}
+		return strings.Join(s, " ")
+	}
+}
+
+type RulesetAttr struct {
+	// Bitmask of handled filesystem actions.
+	HandledAccessFS LandlockAccessFS
+	// Bitmask of handled network actions.
+	HandledAccessNet LandlockAccessNet
+	// Bitmask of scopes restricting a Landlock domain from accessing outside resources (e.g. IPCs).
+	Scoped LandlockScope
+}
+
+func (rulesetAttr *RulesetAttr) String() string {
+	if rulesetAttr == nil {
+		return "NULL"
+	}
+	elems := make([]string, 0, 3)
+	if rulesetAttr.HandledAccessFS > 0 {
+		elems = append(elems, "fs: "+rulesetAttr.HandledAccessFS.String())
+	}
+	if rulesetAttr.HandledAccessNet > 0 {
+		elems = append(elems, "net: "+rulesetAttr.HandledAccessNet.String())
+	}
+	if rulesetAttr.Scoped > 0 {
+		elems = append(elems, "scoped: "+rulesetAttr.Scoped.String())
+	}
+	if len(elems) == 0 {
+		return "0"
+	}
+	return strings.Join(elems, ", ")
+}
+
+func (rulesetAttr *RulesetAttr) Create(flags uintptr) (fd int, err error) {
 	var pointer, size uintptr
 	// NULL needed for abi version
 	if rulesetAttr != nil {
@@ -47,7 +227,7 @@ func LandlockCreateRuleset(rulesetAttr *RulesetAttr, flags uintptr) (fd int, err
 }
 
 func LandlockGetABI() (int, error) {
-	return LandlockCreateRuleset(nil, LANDLOCK_CREATE_RULESET_VERSION)
+	return (*RulesetAttr)(nil).Create(LANDLOCK_CREATE_RULESET_VERSION)
 }
 
 func LandlockRestrictSelf(rulesetFd int, flags uintptr) error {

container/landlock_test.go

@@ -0,0 +1,61 @@
+package container_test
+
+import (
+	"testing"
+	"unsafe"
+
+	"hakurei.app/container"
+)
+
+func TestLandlockString(t *testing.T) {
+	testCases := []struct {
+		name        string
+		rulesetAttr *container.RulesetAttr
+		want        string
+	}{
+		{"nil", nil, "NULL"},
+		{"zero", new(container.RulesetAttr), "0"},
+		{"some", &container.RulesetAttr{Scoped: container.LANDLOCK_SCOPE_SIGNAL}, "scoped: signal"},
+		{"set", &container.RulesetAttr{
+			HandledAccessFS:  container.LANDLOCK_ACCESS_FS_MAKE_SYM | container.LANDLOCK_ACCESS_FS_IOCTL_DEV | container.LANDLOCK_ACCESS_FS_WRITE_FILE,
+			HandledAccessNet: container.LANDLOCK_ACCESS_NET_BIND_TCP,
+			Scoped:           container.LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET | container.LANDLOCK_SCOPE_SIGNAL,
+		}, "fs: write_file make_sym fs_ioctl_dev, net: bind_tcp, scoped: abstract_unix_socket signal"},
+		{"all", &container.RulesetAttr{
+			HandledAccessFS: container.LANDLOCK_ACCESS_FS_EXECUTE |
+				container.LANDLOCK_ACCESS_FS_WRITE_FILE |
+				container.LANDLOCK_ACCESS_FS_READ_FILE |
+				container.LANDLOCK_ACCESS_FS_READ_DIR |
+				container.LANDLOCK_ACCESS_FS_REMOVE_DIR |
+				container.LANDLOCK_ACCESS_FS_REMOVE_FILE |
+				container.LANDLOCK_ACCESS_FS_MAKE_CHAR |
+				container.LANDLOCK_ACCESS_FS_MAKE_DIR |
+				container.LANDLOCK_ACCESS_FS_MAKE_REG |
+				container.LANDLOCK_ACCESS_FS_MAKE_SOCK |
+				container.LANDLOCK_ACCESS_FS_MAKE_FIFO |
+				container.LANDLOCK_ACCESS_FS_MAKE_BLOCK |
+				container.LANDLOCK_ACCESS_FS_MAKE_SYM |
+				container.LANDLOCK_ACCESS_FS_REFER |
+				container.LANDLOCK_ACCESS_FS_TRUNCATE |
+				container.LANDLOCK_ACCESS_FS_IOCTL_DEV,
+			HandledAccessNet: container.LANDLOCK_ACCESS_NET_BIND_TCP |
+				container.LANDLOCK_ACCESS_NET_CONNECT_TCP,
+			Scoped: container.LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |
+				container.LANDLOCK_SCOPE_SIGNAL,
+		}, "fs: execute write_file read_file read_dir remove_dir remove_file make_char make_dir make_reg make_sock make_fifo make_block make_sym fs_refer fs_truncate fs_ioctl_dev, net: bind_tcp connect_tcp, scoped: abstract_unix_socket signal"},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := tc.rulesetAttr.String(); got != tc.want {
+				t.Errorf("String: %s, want %s", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestLandlockAttrSize(t *testing.T) {
+	want := 24
+	if got := unsafe.Sizeof(container.RulesetAttr{}); got != uintptr(want) {
+		t.Errorf("Sizeof: %d, want %d", got, want)
+	}
+}