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package sys
import (
"errors"
"fmt"
"io/fs"
"os"
"os/exec"
"os/user"
"path/filepath"
"strconv"
"sync"
"syscall"
"git.gensokyo.uk/security/hakurei/internal"
"git.gensokyo.uk/security/hakurei/internal/app"
"git.gensokyo.uk/security/hakurei/internal/hlog"
"git.gensokyo.uk/security/hakurei/sandbox"
)
// Std implements System using the standard library.
type Std struct {
paths app.Paths
pathsOnce sync.Once
uidOnce sync.Once
uidCopy map[int]struct {
uid int
err error
}
uidMu sync.RWMutex
}
func (s *Std) Getuid() int { return os.Getuid() }
func (s *Std) Getgid() int { return os.Getgid() }
func (s *Std) LookupEnv(key string) (string, bool) { return os.LookupEnv(key) }
func (s *Std) TempDir() string { return os.TempDir() }
func (s *Std) LookPath(file string) (string, error) { return exec.LookPath(file) }
func (s *Std) MustExecutable() string { return sandbox.MustExecutable() }
func (s *Std) LookupGroup(name string) (*user.Group, error) { return user.LookupGroup(name) }
func (s *Std) ReadDir(name string) ([]os.DirEntry, error) { return os.ReadDir(name) }
func (s *Std) Stat(name string) (fs.FileInfo, error) { return os.Stat(name) }
func (s *Std) Open(name string) (fs.File, error) { return os.Open(name) }
func (s *Std) EvalSymlinks(path string) (string, error) { return filepath.EvalSymlinks(path) }
func (s *Std) Exit(code int) { internal.Exit(code) }
func (s *Std) Println(v ...any) { hlog.Verbose(v...) }
func (s *Std) Printf(format string, v ...any) { hlog.Verbosef(format, v...) }
const xdgRuntimeDir = "XDG_RUNTIME_DIR"
func (s *Std) Paths() app.Paths {
s.pathsOnce.Do(func() { CopyPaths(s, &s.paths) })
return s.paths
}
func (s *Std) Uid(aid int) (int, error) {
s.uidOnce.Do(func() {
s.uidCopy = make(map[int]struct {
uid int
err error
})
})
{
s.uidMu.RLock()
u, ok := s.uidCopy[aid]
s.uidMu.RUnlock()
if ok {
return u.uid, u.err
}
}
s.uidMu.Lock()
defer s.uidMu.Unlock()
u := struct {
uid int
err error
}{}
defer func() { s.uidCopy[aid] = u }()
u.uid = -1
hsuPath := internal.MustHsuPath()
cmd := exec.Command(hsuPath)
cmd.Path = hsuPath
cmd.Stderr = os.Stderr // pass through fatal messages
cmd.Env = []string{"HAKUREI_APP_ID=" + strconv.Itoa(aid)}
cmd.Dir = "/"
var (
p []byte
exitError *exec.ExitError
)
if p, u.err = cmd.Output(); u.err == nil {
u.uid, u.err = strconv.Atoi(string(p))
if u.err != nil {
u.err = hlog.WrapErrSuffix(u.err, "cannot parse uid from hsu:")
}
} else if errors.As(u.err, &exitError) && exitError != nil && exitError.ExitCode() == 1 {
u.err = hlog.WrapErr(syscall.EACCES, "") // hsu prints to stderr in this case
} else if os.IsNotExist(u.err) {
u.err = hlog.WrapErr(os.ErrNotExist, fmt.Sprintf("the setuid helper is missing: %s", hsuPath))
}
return u.uid, u.err
}
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