cosmopolitan/libc/runtime/login_tty.c
2023-09-10 08:17:44 -07:00

68 lines
3.2 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/strace.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/utmp.h"
#include "libc/sysv/consts/termios.h"
#include "libc/sysv/errfuns.h"
/**
* Prepares terminal for login.
*
* After this operation `fd` will be used for all stdio handles.
*
* @return 0 on success, or -1 w/ errno
* @raise EPERM if terminal is already controlling another sid?
* @raise EPERM if pledge() was used without tty
* @raise ENOTTY if `fd` isn't a teletypewriter
* @raise ENOSYS on Windows and Metal
* @raise EBADF if `fd` isn't open
*/
int login_tty(int fd) {
int rc;
if (!IsLinux() && !IsBsd()) {
rc = enosys();
} else if (!isatty(fd)) {
rc = -1; // validate before changing the process's state
} else {
// become session leader
// we don't care if it fails due to already being the one
int e = errno;
sys_setsid();
errno = e;
// take control of teletypewriter (requires being leader)
if ((rc = sys_ioctl(fd, TIOCSCTTY, 0)) != -1) {
unassert(!sys_dup2(fd, 0, 0));
unassert(!sys_dup2(fd, 1, 0));
unassert(!sys_dup2(fd, 2, 0));
if (fd > 2) {
unassert(!sys_close(fd));
}
rc = 0;
}
}
STRACE("login_tty(%d) → %d% m", fd, rc);
return rc;
}