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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/ldd"
"git.gensokyo.uk/security/fortify/sandbox"
"git.gensokyo.uk/security/fortify/sandbox/seccomp"
)
// Start launches the D-Bus proxy.
func (p *Proxy) Start(ctx context.Context, output io.Writer, useSandbox 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 !useSandbox {
h = helper.NewDirect(c, p.name, p.seal, true, argF, func(cmd *exec.Cmd) {
if p.CmdF != nil {
p.CmdF(cmd)
}
if output != nil {
cmd.Stdout, cmd.Stderr = output, output
}
cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
cmd.Env = make([]string, 0)
}, nil)
} else {
toolPath := p.name
if filepath.Base(p.name) == p.name {
if s, err := exec.LookPath(p.name); err != nil {
return err
} else {
toolPath = s
}
}
var libPaths []string
if entries, err := ldd.ExecFilter(ctx, p.CommandContext, p.FilterF, toolPath); err != nil {
return err
} else {
libPaths = ldd.Path(entries)
}
h = helper.New(
c, toolPath,
p.seal, true,
argF, func(container *sandbox.Container) {
container.Seccomp |= seccomp.FlagMultiarch
container.Hostname = "fortify-dbus"
container.CommandContext = p.CommandContext
if output != nil {
container.Stdout, container.Stderr = output, output
}
if p.CmdF != nil {
p.CmdF(container)
}
// these lib paths are unpredictable, so mount them first so they cannot cover anything
for _, name := range libPaths {
container.Bind(name, name, 0)
}
// upstream bus directories
upstreamPaths := make([]string, 0, 2)
for _, as := range []string{p.session[0], p.system[0]} {
if len(as) > 0 && strings.HasPrefix(as, "unix:path=/") {
// leave / intact
upstreamPaths = append(upstreamPaths, path.Dir(as[10:]))
}
}
slices.Sort(upstreamPaths)
upstreamPaths = slices.Compact(upstreamPaths)
for _, name := range upstreamPaths {
container.Bind(name, name, 0)
}
// parent directories of bind paths
sockDirPaths := make([]string, 0, 2)
if d := path.Dir(p.session[1]); path.IsAbs(d) {
sockDirPaths = append(sockDirPaths, d)
}
if d := path.Dir(p.system[1]); path.IsAbs(d) {
sockDirPaths = append(sockDirPaths, d)
}
slices.Sort(sockDirPaths)
sockDirPaths = slices.Compact(sockDirPaths)
for _, name := range sockDirPaths {
container.Bind(name, name, sandbox.BindWritable)
}
// xdg-dbus-proxy bin path
binPath := path.Dir(toolPath)
container.Bind(binPath, binPath, 0)
}, nil)
}
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)}
}
}
|
