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package sandbox
import (
"encoding/gob"
"errors"
"fmt"
"math"
"os"
"path"
"strings"
"syscall"
"git.gensokyo.uk/security/fortify/internal/fmsg"
)
func init() { gob.Register(new(BindMount)) }
const (
BindOptional = 1 << iota
BindRecursive
BindWritable
BindDevices
)
// BindMount bind mounts host path Source on container path Target.
type BindMount struct {
Source, Target string
Flags int
}
func (b *BindMount) apply() error {
if !path.IsAbs(b.Source) || !path.IsAbs(b.Target) {
return syscall.EBADE
}
target := toSysroot(b.Target)
var source string
// this is what bwrap does, so the behaviour is kept for now,
// however recursively resolving links might improve user experience
if rp, err := realpathHost(b.Source); err != nil {
if os.IsNotExist(err) {
if b.Flags&BindOptional != 0 {
return nil
} else {
return fmsg.WrapError(err,
fmt.Sprintf("path %q does not exist", b.Source))
}
}
return fmsg.WrapError(err, err.Error())
} else {
source = toHost(rp)
}
if fi, err := os.Stat(source); err != nil {
return fmsg.WrapError(err, err.Error())
} else if fi.IsDir() {
if err = os.MkdirAll(target, 0755); err != nil {
return fmsg.WrapErrorSuffix(err,
fmt.Sprintf("cannot create directory %q:", b.Target))
}
} else if err = ensureFile(target, 0444); err != nil {
if errors.Is(err, syscall.EISDIR) {
return fmsg.WrapError(err,
fmt.Sprintf("path %q is a directory", b.Target))
}
return fmsg.WrapErrorSuffix(err,
fmt.Sprintf("cannot create %q:", b.Target))
}
var flags uintptr = syscall.MS_SILENT | syscall.MS_BIND
if b.Flags&BindRecursive != 0 {
flags |= syscall.MS_REC
}
if b.Flags&BindWritable == 0 {
flags |= syscall.MS_RDONLY
}
if b.Flags&BindDevices == 0 {
flags |= syscall.MS_NODEV
}
if fmsg.Load() {
if strings.TrimPrefix(source, hostPath) == strings.TrimPrefix(target, sysrootPath) {
fmsg.Verbosef("resolved %q flags %#x", target, flags)
} else {
fmsg.Verbosef("resolved %q on %q flags %#x", source, target, flags)
}
}
return fmsg.WrapErrorSuffix(syscall.Mount(source, target, "", flags, ""),
fmt.Sprintf("cannot bind %q on %q:", b.Source, b.Target))
}
func (b *BindMount) Is(op Op) bool { vb, ok := op.(*BindMount); return ok && *b == *vb }
func (b *BindMount) String() string {
if b.Source == b.Target {
return fmt.Sprintf("%q flags %#x", b.Source, b.Flags)
}
return fmt.Sprintf("%q on %q flags %#x", b.Source, b.Target, b.Flags&BindWritable)
}
func (f *Ops) Bind(source, target string, flags int) *Ops {
*f = append(*f, &BindMount{source, target, flags | BindRecursive})
return f
}
func init() { gob.Register(new(MountProc)) }
// MountProc mounts a private proc instance on container Path.
type MountProc struct {
Path string
}
func (p *MountProc) apply() error {
if !path.IsAbs(p.Path) {
return fmsg.WrapError(syscall.EBADE,
fmt.Sprintf("path %q is not absolute", p.Path))
}
target := toSysroot(p.Path)
if err := os.MkdirAll(target, 0755); err != nil {
return fmsg.WrapError(err, err.Error())
}
return fmsg.WrapErrorSuffix(syscall.Mount("proc", target, "proc",
syscall.MS_NOSUID|syscall.MS_NOEXEC|syscall.MS_NODEV, ""),
fmt.Sprintf("cannot mount proc on %q:", p.Path))
}
func (p *MountProc) Is(op Op) bool { vp, ok := op.(*MountProc); return ok && *p == *vp }
func (p *MountProc) String() string { return fmt.Sprintf("proc on %q", p.Path) }
func (f *Ops) Proc(dest string) *Ops {
*f = append(*f, &MountProc{dest})
return f
}
func init() { gob.Register(new(MountTmpfs)) }
// MountTmpfs mounts tmpfs on container Path.
type MountTmpfs struct {
Path string
Size int
Mode os.FileMode
}
func (t *MountTmpfs) apply() error {
if !path.IsAbs(t.Path) {
return fmsg.WrapError(syscall.EBADE,
fmt.Sprintf("path %q is not absolute", t.Path))
}
if t.Size < 0 || t.Size > math.MaxUint>>1 {
return fmsg.WrapError(syscall.EBADE,
fmt.Sprintf("size %d out of bounds", t.Size))
}
target := toSysroot(t.Path)
if err := os.MkdirAll(target, 0755); err != nil {
return err
}
opt := fmt.Sprintf("mode=%#o", t.Mode)
if t.Size > 0 {
opt += fmt.Sprintf(",size=%d", t.Mode)
}
return fmsg.WrapErrorSuffix(syscall.Mount("tmpfs", target, "tmpfs",
syscall.MS_NOSUID|syscall.MS_NODEV, opt),
fmt.Sprintf("cannot mount tmpfs on %q:", t.Path))
}
func (t *MountTmpfs) Is(op Op) bool { vt, ok := op.(*MountTmpfs); return ok && *t == *vt }
func (t *MountTmpfs) String() string { return fmt.Sprintf("tmpfs on %q size %d", t.Path, t.Size) }
func (f *Ops) Tmpfs(dest string, size int, mode os.FileMode) *Ops {
*f = append(*f, &MountTmpfs{dest, size, mode})
return f
}
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