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package common
import (
"errors"
"fmt"
"io/fs"
"maps"
"path"
"syscall"
"git.gensokyo.uk/security/hakurei/dbus"
"git.gensokyo.uk/security/hakurei/hst"
"git.gensokyo.uk/security/hakurei/internal/sys"
"git.gensokyo.uk/security/hakurei/sandbox"
"git.gensokyo.uk/security/hakurei/sandbox/seccomp"
)
// 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 [sandbox.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) (*sandbox.Params, map[string]string, error) {
if s == nil {
return nil, nil, syscall.EBADE
}
container := &sandbox.Params{
Hostname: s.Hostname,
Seccomp: s.Seccomp,
}
{
ops := make(sandbox.Ops, 0, preallocateOpsCount+len(s.Filesystem)+len(s.Link)+len(s.Cover))
container.Ops = &ops
}
if s.Multiarch {
container.Seccomp |= seccomp.FilterMultiarch
}
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 = os.Getuid()
*uid = container.Uid
container.Gid = os.Getgid()
*gid = container.Gid
} else {
*uid = sandbox.OverflowUid()
*gid = sandbox.OverflowGid()
}
container.
Proc("/proc").
Tmpfs(hst.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 := 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 |= 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(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
}
|
