app/instance: wrap internal implementation

This reduces the scope of the fst package, which was growing questionably large.

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

1 files changed, 0 insertions, 192 deletions

diff --git a/fst/sandbox.go b/fst/sandbox.go
index 194fcb76..c4936a2e 100644
--- a/fst/sandbox.go
+++ b/fst/sandbox.go
@@ -1,16 +1,6 @@
 package fst
 
 import (
-	"errors"
-	"fmt"
-	"io/fs"
-	"maps"
-	"path"
-	"slices"
-	"syscall"
-
-	"git.gensokyo.uk/security/fortify/dbus"
-	"git.gensokyo.uk/security/fortify/sandbox"
 	"git.gensokyo.uk/security/fortify/sandbox/seccomp"
 )
 
@@ -57,18 +47,6 @@ type (
 		Cover []string `json:"cover"`
 	}
 
-	// SandboxSys encapsulates system functions used during [sandbox.Container] initialisation.
-	SandboxSys interface {
-		Getuid() int
-		Getgid() int
-		Paths() Paths
-		ReadDir(name string) ([]fs.DirEntry, error)
-		EvalSymlinks(path string) (string, error)
-
-		Println(v ...any)
-		Printf(format string, v ...any)
-	}
-
 	// FilesystemConfig is a representation of [sandbox.BindMount].
 	FilesystemConfig struct {
 		// mount point in container, same as src if empty
@@ -83,173 +61,3 @@ type (
 		Must bool `json:"require,omitempty"`
 	}
 )
-
-// ToContainer initialises [sandbox.Params] via [SandboxConfig].
-// Note that remaining container setup must be queued by the [App] implementation.
-func (s *SandboxConfig) ToContainer(sys SandboxSys, uid, gid *int) (*sandbox.Params, map[string]string, error) {
-	if s == nil {
-		return nil, nil, syscall.EBADE
-	}
-
-	container := &sandbox.Params{
-		Hostname: s.Hostname,
-		Ops:      new(sandbox.Ops),
-		Seccomp:  s.Seccomp,
-	}
-
-	if s.Multiarch {
-		container.Seccomp |= seccomp.FilterMultiarch
-	}
-
-	/* this is only 4 KiB of memory on a 64-bit system,
-	permissive defaults on NixOS results in around 100 entries
-	so this capacity should eliminate copies for most setups */
-	*container.Ops = slices.Grow(*container.Ops, 1<<8)
-
-	if s.Devel {
-		container.Flags |= sandbox.FAllowDevel
-	}
-	if s.Userns {
-		container.Flags |= sandbox.FAllowUserns
-	}
-	if s.Net {
-		container.Flags |= sandbox.FAllowNet
-	}
-	if s.Tty {
-		container.Flags |= sandbox.FAllowTTY
-	}
-
-	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 */
-		container.Uid = sys.Getuid()
-		*uid = container.Uid
-		container.Gid = sys.Getgid()
-		*gid = container.Gid
-	} else {
-		*uid = sandbox.OverflowUid()
-		*gid = sandbox.OverflowGid()
-	}
-
-	container.
-		Proc("/proc").
-		Tmpfs(Tmp, 1<<12, 0755)
-
-	if !s.Device {
-		container.Dev("/dev").Mqueue("/dev/mqueue")
-	} else {
-		container.Bind("/dev", "/dev", sandbox.BindWritable|sandbox.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 := sys.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 == "/" {
-							sys.Printf("dbus socket %q is in an unusual location", pair[1])
-						}
-						hidePaths = append(hidePaths, dir)
-					} else {
-						sys.Printf("dbus socket %q is not absolute", pair[1])
-					}
-				}
-			}
-		}
-	}
-	hidePathMatch := make([]bool, len(hidePaths))
-	for i := range hidePaths {
-		if err := evalSymlinks(sys, &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(sys, &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
-				sys.Printf("hiding paths from %q", c.Src)
-			}
-		}
-
-		var flags int
-		if c.Write {
-			flags |= sandbox.BindWritable
-		}
-		if c.Device {
-			flags |= sandbox.BindDevice | sandbox.BindWritable
-		}
-		if !c.Must {
-			flags |= sandbox.BindOptional
-		}
-		container.Bind(c.Src, dest, flags)
-	}
-
-	// cover matched paths
-	for i, ok := range hidePathMatch {
-		if ok {
-			container.Tmpfs(hidePaths[i], 1<<13, 0755)
-		}
-	}
-
-	for _, l := range s.Link {
-		container.Link(l[0], l[1])
-	}
-
-	return container, maps.Clone(s.Env), nil
-}
-
-func evalSymlinks(sys SandboxSys, v *string) error {
-	if p, err := sys.EvalSymlinks(*v); err != nil {
-		if !errors.Is(err, fs.ErrNotExist) {
-			return err
-		}
-		sys.Printf("path %q does not yet exist", *v)
-	} else {
-		*v = p
-	}
-	return nil
-}