internal/app: remove seal interface

This further cleans up the package for the restructure.

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

1 files changed, 252 insertions, 0 deletions

diff --git a/internal/app/container.go b/internal/app/container.go
new file mode 100644
index 00000000..cdefe170
--- /dev/null
+++ b/internal/app/container.go
@@ -0,0 +1,252 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"maps"
+	"path"
+	"syscall"
+
+	"hakurei.app/container"
+	"hakurei.app/container/seccomp"
+	"hakurei.app/hst"
+	"hakurei.app/internal/hlog"
+	"hakurei.app/internal/sys"
+	"hakurei.app/system/dbus"
+)
+
+// in practice there should be less than 30 system mount points
+const preallocateOpsCount = 1 << 5
+
+// newContainer initialises [container.Params] via [hst.ContainerConfig].
+// Note that remaining container setup must be queued by the caller.
+func newContainer(s *hst.ContainerConfig, os sys.State, prefix string, uid, gid *int) (*container.Params, map[string]string, error) {
+	if s == nil {
+		return nil, nil, hlog.WrapErr(syscall.EBADE, "invalid container configuration")
+	}
+
+	params := &container.Params{
+		Hostname:       s.Hostname,
+		SeccompFlags:   s.SeccompFlags,
+		SeccompPresets: s.SeccompPresets,
+		RetainSession:  s.Tty,
+		HostNet:        s.HostNet,
+		HostAbstract:   s.HostAbstract,
+
+		// the container is canceled when shim is requested to exit or receives an interrupt or termination signal;
+		// this behaviour is implemented in the shim
+		ForwardCancel: s.WaitDelay >= 0,
+	}
+
+	as := &hst.ApplyState{
+		AutoEtcPrefix: prefix,
+	}
+	{
+		ops := make(container.Ops, 0, preallocateOpsCount+len(s.Filesystem))
+		params.Ops = &ops
+		as.Ops = &ops
+	}
+
+	if s.Multiarch {
+		params.SeccompFlags |= seccomp.AllowMultiarch
+	}
+
+	if !s.SeccompCompat {
+		params.SeccompPresets |= seccomp.PresetExt
+	}
+	if !s.Devel {
+		params.SeccompPresets |= seccomp.PresetDenyDevel
+	}
+	if !s.Userns {
+		params.SeccompPresets |= seccomp.PresetDenyNS
+	}
+	if !s.Tty {
+		params.SeccompPresets |= seccomp.PresetDenyTTY
+	}
+
+	if s.MapRealUID {
+		params.Uid = os.Getuid()
+		*uid = params.Uid
+		params.Gid = os.Getgid()
+		*gid = params.Gid
+	} else {
+		*uid = container.OverflowUid()
+		*gid = container.OverflowGid()
+	}
+
+	filesystem := s.Filesystem
+	var autoroot *hst.FSBind
+	// valid happens late, so root mount gets it here
+	if len(filesystem) > 0 && filesystem[0].Valid() && filesystem[0].Path().String() == container.FHSRoot {
+		// if the first element targets /, it is inserted early and excluded from path hiding
+		rootfs := filesystem[0].FilesystemConfig
+		filesystem = filesystem[1:]
+		rootfs.Apply(as)
+
+		// autoroot requires special handling during path hiding
+		if b, ok := rootfs.(*hst.FSBind); ok && b.IsAutoRoot() {
+			autoroot = b
+		}
+	}
+
+	params.
+		Proc(container.AbsFHSProc).
+		Tmpfs(hst.AbsTmp, 1<<12, 0755)
+
+	if !s.Device {
+		params.DevWritable(container.AbsFHSDev, true)
+	} else {
+		params.Bind(container.AbsFHSDev, container.AbsFHSDev, container.BindWritable|container.BindDevice)
+	}
+
+	/* retrieve paths and hide them if they're made available in the sandbox;
+
+	this feature tries to improve user experience of permissive defaults, and
+	to warn about issues in custom configuration; it is NOT a security feature
+	and should not be treated as such, ALWAYS be careful with what you bind */
+	var hidePaths []string
+	sc := os.Paths()
+	hidePaths = append(hidePaths, sc.RuntimePath.String(), sc.SharePath.String())
+	_, systemBusAddr := dbus.Address()
+	if entries, err := dbus.Parse([]byte(systemBusAddr)); err != nil {
+		return nil, nil, err
+	} else {
+		// there is usually only one, do not preallocate
+		for _, entry := range entries {
+			if entry.Method != "unix" {
+				continue
+			}
+			for _, pair := range entry.Values {
+				if pair[0] == "path" {
+					if path.IsAbs(pair[1]) {
+						// get parent dir of socket
+						dir := path.Dir(pair[1])
+						if dir == "." || dir == container.FHSRoot {
+							os.Printf("dbus socket %q is in an unusual location", pair[1])
+						}
+						hidePaths = append(hidePaths, dir)
+					} else {
+						os.Printf("dbus socket %q is not absolute", pair[1])
+					}
+				}
+			}
+		}
+	}
+	hidePathMatch := make([]bool, len(hidePaths))
+	for i := range hidePaths {
+		if err := evalSymlinks(os, &hidePaths[i]); err != nil {
+			return nil, nil, err
+		}
+	}
+
+	var hidePathSourceCount int
+	for i, c := range filesystem {
+		if !c.Valid() {
+			return nil, nil, fmt.Errorf("invalid filesystem at index %d", i)
+		}
+		c.Apply(as)
+
+		// fs counter
+		hidePathSourceCount += len(c.Host())
+	}
+
+	// AutoRootOp is a collection of many BindMountOp internally
+	var autoRootEntries []fs.DirEntry
+	if autoroot != nil {
+		if d, err := os.ReadDir(autoroot.Source.String()); err != nil {
+			return nil, nil, err
+		} else {
+			// autoroot counter
+			hidePathSourceCount += len(d)
+			autoRootEntries = d
+		}
+	}
+
+	hidePathSource := make([]*container.Absolute, 0, hidePathSourceCount)
+
+	// fs append
+	for _, c := range filesystem {
+		// all entries already checked above
+		hidePathSource = append(hidePathSource, c.Host()...)
+	}
+
+	// autoroot append
+	if autoroot != nil {
+		for _, ent := range autoRootEntries {
+			name := ent.Name()
+			if container.IsAutoRootBindable(name) {
+				hidePathSource = append(hidePathSource, autoroot.Source.Append(name))
+			}
+		}
+	}
+
+	// evaluated path, input path
+	hidePathSourceEval := make([][2]string, len(hidePathSource))
+	for i, a := range hidePathSource {
+		if a == nil {
+			// unreachable
+			return nil, nil, syscall.ENOTRECOVERABLE
+		}
+
+		hidePathSourceEval[i] = [2]string{a.String(), a.String()}
+		if err := evalSymlinks(os, &hidePathSourceEval[i][0]); err != nil {
+			return nil, nil, err
+		}
+	}
+
+	for _, p := range hidePathSourceEval {
+		for i := range hidePaths {
+			// skip matched entries
+			if hidePathMatch[i] {
+				continue
+			}
+
+			if ok, err := deepContainsH(p[0], hidePaths[i]); err != nil {
+				return nil, nil, err
+			} else if ok {
+				hidePathMatch[i] = true
+				os.Printf("hiding path %q from %q", hidePaths[i], p[1])
+			}
+		}
+	}
+
+	// cover matched paths
+	for i, ok := range hidePathMatch {
+		if ok {
+			if a, err := container.NewAbs(hidePaths[i]); err != nil {
+				var absoluteError *container.AbsoluteError
+				if !errors.As(err, &absoluteError) {
+					return nil, nil, err
+				}
+				if absoluteError == nil {
+					return nil, nil, syscall.ENOTRECOVERABLE
+				}
+				return nil, nil, fmt.Errorf("invalid path hiding candidate %q", absoluteError.Pathname)
+			} else {
+				params.Tmpfs(a, 1<<13, 0755)
+			}
+		}
+	}
+
+	// no more ContainerConfig paths beyond this point
+	if !s.Device {
+		params.
+			Remount(container.AbsFHSDev, syscall.MS_RDONLY).
+			Tmpfs(container.AbsFHSDev.Append("shm"), 0, 01777)
+	}
+
+	return params, maps.Clone(s.Env), nil
+}
+
+func evalSymlinks(os sys.State, v *string) error {
+	if p, err := os.EvalSymlinks(*v); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			return err
+		}
+		os.Printf("path %q does not yet exist", *v)
+	} else {
+		*v = p
+	}
+	return nil
+}