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package dbus
import (
"context"
"errors"
"io"
"os"
"os/exec"
"path"
"path/filepath"
"slices"
"strconv"
"strings"
"syscall"
"git.gensokyo.uk/security/fortify/helper"
"git.gensokyo.uk/security/fortify/helper/bwrap"
"git.gensokyo.uk/security/fortify/ldd"
)
// Start launches the D-Bus proxy.
func (p *Proxy) Start(ctx context.Context, output io.Writer, sandbox bool) error {
p.lock.Lock()
defer p.lock.Unlock()
if p.seal == nil {
return errors.New("proxy not sealed")
}
var h helper.Helper
c, cancel := context.WithCancelCause(ctx)
if !sandbox {
h = helper.NewDirect(c, p.name, p.seal, true, argF, func(cmd *exec.Cmd) {
cmdF(cmd, output, p.CmdF)
// xdg-dbus-proxy does not need to inherit the environment
cmd.Env = make([]string, 0)
}, nil)
} else {
// look up absolute path if name is just a file name
toolPath := p.name
if filepath.Base(p.name) == p.name {
if s, err := exec.LookPath(p.name); err != nil {
return err
} else {
toolPath = s
}
}
// resolve libraries by parsing ldd output
var proxyDeps []*ldd.Entry
if toolPath != os.Args[0] {
if l, err := ldd.Exec(ctx, toolPath); err != nil {
return err
} else {
proxyDeps = l
}
}
bc := &bwrap.Config{
Hostname: "fortify-dbus",
Chdir: "/",
Syscall: &bwrap.SyscallPolicy{DenyDevel: true, Multiarch: true},
Clearenv: true,
NewSession: true,
DieWithParent: true,
}
// resolve proxy socket directories
bindTargetM := make(map[string]struct{}, 2)
for _, ps := range []string{p.session[1], p.system[1]} {
if pd := path.Dir(ps); len(pd) > 0 {
if pd[0] == '/' {
bindTargetM[pd] = struct{}{}
}
}
}
bindTarget := make([]string, 0, len(bindTargetM))
for k := range bindTargetM {
bindTarget = append(bindTarget, k)
}
slices.Sort(bindTarget)
for _, name := range bindTarget {
bc.Bind(name, name, false, true)
}
roBindTargetM := make(map[string]struct{}, 2+1+len(proxyDeps))
// xdb-dbus-proxy bin and dependencies
roBindTargetM[path.Dir(toolPath)] = struct{}{}
for _, ent := range proxyDeps {
if path.IsAbs(ent.Path) {
roBindTargetM[path.Dir(ent.Path)] = struct{}{}
}
if path.IsAbs(ent.Name) {
roBindTargetM[path.Dir(ent.Name)] = struct{}{}
}
}
// resolve upstream bus directories
for _, as := range []string{p.session[0], p.system[0]} {
if len(as) > 0 && strings.HasPrefix(as, "unix:path=/") {
// leave / intact
roBindTargetM[path.Dir(as[10:])] = struct{}{}
}
}
roBindTarget := make([]string, 0, len(roBindTargetM))
for k := range roBindTargetM {
roBindTarget = append(roBindTarget, k)
}
slices.Sort(roBindTarget)
for _, name := range roBindTarget {
bc.Bind(name, name)
}
h = helper.MustNewBwrap(c, toolPath,
p.seal, true,
argF, func(cmd *exec.Cmd) { cmdF(cmd, output, p.CmdF) },
nil,
bc, nil,
)
p.bwrap = bc
}
if err := h.Start(); err != nil {
cancel(err)
return err
}
p.helper = h
p.ctx = c
p.cancel = cancel
return nil
}
var proxyClosed = errors.New("proxy closed")
// Wait blocks until xdg-dbus-proxy exits and releases resources.
func (p *Proxy) Wait() error {
p.lock.RLock()
defer p.lock.RUnlock()
if p.helper == nil {
return errors.New("dbus: not started")
}
errs := make([]error, 3)
errs[0] = p.helper.Wait()
if p.cancel == nil &&
errors.Is(errs[0], context.Canceled) &&
errors.Is(context.Cause(p.ctx), proxyClosed) {
errs[0] = nil
}
// ensure socket removal so ephemeral directory is empty at revert
if err := os.Remove(p.session[1]); err != nil && !errors.Is(err, os.ErrNotExist) {
errs[1] = err
}
if p.sysP {
if err := os.Remove(p.system[1]); err != nil && !errors.Is(err, os.ErrNotExist) {
errs[2] = err
}
}
return errors.Join(errs...)
}
// Close cancels the context passed to the helper instance attached to xdg-dbus-proxy.
func (p *Proxy) Close() {
p.lock.Lock()
defer p.lock.Unlock()
if p.cancel == nil {
panic("dbus: not started")
}
p.cancel(proxyClosed)
p.cancel = nil
}
func argF(argsFd, statFd int) []string {
if statFd == -1 {
return []string{"--args=" + strconv.Itoa(argsFd)}
} else {
return []string{"--args=" + strconv.Itoa(argsFd), "--fd=" + strconv.Itoa(statFd)}
}
}
func cmdF(cmd *exec.Cmd, output io.Writer, cmdF func(cmd *exec.Cmd)) {
cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
if output != nil {
cmd.Stdout, cmd.Stderr = output, output
}
if cmdF != nil {
cmdF(cmd)
}
}
|
