app: remove split implementation

It is completely nonsensical and highly error-prone to have multiple implementations of this in the same build. This should be switched at compile time instead therefore the split packages are pointless.

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

1 files changed, 192 insertions, 0 deletions

diff --git a/internal/app/container_linux.go b/internal/app/container_linux.go
new file mode 100644
index 00000000..98cddc7a
--- /dev/null
+++ b/internal/app/container_linux.go
@@ -0,0 +1,192 @@
+package app
+
+import (
+	"errors"
+	"fmt"
+	"io/fs"
+	"maps"
+	"path"
+	"syscall"
+
+	"hakurei.app/container"
+	"hakurei.app/container/seccomp"
+	"hakurei.app/hst"
+	"hakurei.app/internal/sys"
+	"hakurei.app/system/dbus"
+)
+
+// in practice there should be less than 30 entries added by the runtime;
+// allocating slightly more as a margin for future expansion
+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, uid, gid *int) (*container.Params, map[string]string, error) {
+	if s == nil {
+		return nil, nil, syscall.EBADE
+	}
+
+	params := &container.Params{
+		Hostname:       s.Hostname,
+		SeccompFlags:   s.SeccompFlags,
+		SeccompPresets: s.SeccompPresets,
+		RetainSession:  s.Tty,
+		HostNet:        s.Net,
+	}
+
+	{
+		ops := make(container.Ops, 0, preallocateOpsCount+len(s.Filesystem)+len(s.Link)+len(s.Cover))
+		params.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 {
+		/* some programs fail to connect to dbus session running as a different uid
+		so this workaround is introduced to map priv-side caller uid in container */
+		params.Uid = os.Getuid()
+		*uid = params.Uid
+		params.Gid = os.Getgid()
+		*gid = params.Gid
+	} else {
+		*uid = container.OverflowUid()
+		*gid = container.OverflowGid()
+	}
+
+	params.
+		Proc("/proc").
+		Tmpfs(hst.Tmp, 1<<12, 0755)
+
+	if !s.Device {
+		params.Dev("/dev").Mqueue("/dev/mqueue")
+	} else {
+		params.Bind("/dev", "/dev", 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, sc.SharePath)
+	_, 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 == "/" {
+							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
+		}
+	}
+
+	for _, c := range s.Filesystem {
+		if c == nil {
+			continue
+		}
+
+		if !path.IsAbs(c.Src) {
+			return nil, nil, fmt.Errorf("src path %q is not absolute", c.Src)
+		}
+
+		dest := c.Dst
+		if c.Dst == "" {
+			dest = c.Src
+		} else if !path.IsAbs(dest) {
+			return nil, nil, fmt.Errorf("dst path %q is not absolute", dest)
+		}
+
+		srcH := c.Src
+		if err := evalSymlinks(os, &srcH); err != nil {
+			return nil, nil, err
+		}
+
+		for i := range hidePaths {
+			// skip matched entries
+			if hidePathMatch[i] {
+				continue
+			}
+
+			if ok, err := deepContainsH(srcH, hidePaths[i]); err != nil {
+				return nil, nil, err
+			} else if ok {
+				hidePathMatch[i] = true
+				os.Printf("hiding paths from %q", c.Src)
+			}
+		}
+
+		var flags int
+		if c.Write {
+			flags |= container.BindWritable
+		}
+		if c.Device {
+			flags |= container.BindDevice | container.BindWritable
+		}
+		if !c.Must {
+			flags |= container.BindOptional
+		}
+		params.Bind(c.Src, dest, flags)
+	}
+
+	// cover matched paths
+	for i, ok := range hidePathMatch {
+		if ok {
+			params.Tmpfs(hidePaths[i], 1<<13, 0755)
+		}
+	}
+
+	for _, l := range s.Link {
+		params.Link(l[0], l[1])
+	}
+
+	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
+}