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package syscallcompat
import (
"runtime"
"syscall"
"github.com/hanwen/go-fuse/v2/fuse"
)
// asUser runs `f()` under the effective uid, gid, groups specified
// in `context`.
//
// If `context` is nil, `f()` is executed directly without switching user id.
func asUser(f func() (int, error), context *fuse.Context) (int, error) {
if context == nil {
return f()
}
runtime.LockOSThread()
defer runtime.UnlockOSThread()
err := pthread_setugid_np(context.Owner.Uid, context.Owner.Gid)
if err != nil {
return -1, err
}
const (
// KAUTH_UID_NONE and KAUTH_GID_NONE are special values to
// revert permissions to the process credentials.
KAUTH_UID_NONE = ^uint32(0) - 100
KAUTH_GID_NONE = ^uint32(0) - 100
)
defer pthread_setugid_np(KAUTH_UID_NONE, KAUTH_GID_NONE)
return f()
}
// Unfortunately pthread_setugid_np does not have a syscall wrapper yet.
func pthread_setugid_np(uid uint32, gid uint32) (err error) {
_, _, e1 := syscall.RawSyscall(syscall.SYS_SETTID, uintptr(uid), uintptr(gid), 0)
if e1 != 0 {
err = e1
}
return
}
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