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loginx.c
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loginx.c
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// This file is part of the loginx project
//
// Copyright (c) 2013 by Mike Sharov <[email protected]>
// This file is free software, distributed under the MIT License.
#include "ui.h"
#include "pw.h"
#include <pwd.h>
#include <signal.h>
#include <time.h>
#include <locale.h>
#include <termios.h>
#include <sys/ioctl.h>
#include <sys/kd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
//----------------------------------------------------------------------
static void ExitWithError (const char* fn) __attribute__((noreturn));
static void ExitWithMessage (const char* msg) __attribute__((noreturn));
static void InitEnvironment (void);
static int OpenTTYFd (const char* ttypath);
static void OpenTTY (const char* ttypath);
static void ResetTerminal (void);
//----------------------------------------------------------------------
static pid_t _pgrp = 0;
//{{{ Signal handling --------------------------------------------------
#define S(s) (1u<<(s))
enum {
sigset_Quit = S(SIGINT)|S(SIGQUIT)|S(SIGTERM)|S(SIGPWR)|
S(SIGILL)|S(SIGABRT)|S(SIGBUS)|S(SIGFPE)|
S(SIGSYS)|S(SIGSEGV)|S(SIGALRM)|S(SIGXCPU),
qc_ShellSignalQuitOffset = 128
};
static void OnSignal (int s)
{
static bool s_DoubleSignal = false;
if (!s_DoubleSignal) {
s_DoubleSignal = true;
alarm(1);
psignal (s, "[S] Error");
exit (s+qc_ShellSignalQuitOffset);
}
_exit (s+qc_ShellSignalQuitOffset);
}
static void InstallCleanupHandlers (void)
{
for (unsigned i = 0; i < NSIG; ++i)
if (S(i) & sigset_Quit)
signal (i, OnSignal);
}
#undef S
//}}}-------------------------------------------------------------------
//{{{ Utility functions
void* xmalloc (size_t n)
{
void* p = calloc (1, n);
if (!p) {
puts ("Error: out of memory");
exit (EXIT_FAILURE);
}
return (p);
}
void xfree (void* p)
{
if (p)
free (p);
}
static void ExitWithError (const char* fn)
{
printf ("Error: %s: %s\n", fn, strerror(errno));
exit (EXIT_FAILURE);
}
static void ExitWithMessage (const char* msg)
{
printf ("Error: %s\n", msg);
exit (EXIT_FAILURE);
}
#if 0
//}}}-------------------------------------------------------------------
//{{{ Shell
static void LaunchShell (const char* username)
{
struct passwd* pwn = getpwnam (username);
fprintf (stderr, "The user [%s,%hu,%hu] has been authenticated and `logged in'\n", username, pwn->pw_uid, pwn->pw_gid);
setuid (pwn->pw_uid);
setgid (pwn->pw_gid);
setsid();
setpgrp();
/* this is always a really bad thing for security! */
system("/bin/sh");
}
//}}}-------------------------------------------------------------------
#endif
int main (void)
{
char ttypath [16];
ttyname_r (STDIN_FILENO, ttypath, sizeof(ttypath));
InstallCleanupHandlers();
InitEnvironment();
OpenTTY (ttypath);
ResetTerminal();
#if 0
acclist_t al = ReadAccounts();
ReadLastlog();
char password [MAX_PW_LEN];
unsigned ali = LoginBox (al, password);
PamOpen();
const char* username = PamLogin();
LaunchShell (username);
PamLogout();
PamClose();
time_t ltime = al[ali]->ltime;
printf ("Logging in user '%s', password '%s', lastlog %s", al[ali]->name, password, ctime(<ime));
#endif
return (0);
}
static void InitEnvironment (void)
{
if ((_pgrp = setsid()) < 0)
ExitWithError ("setsid");
for (unsigned f = STDERR_FILENO+1, fend = getdtablesize(); f < fend; ++f)
close (f);
}
static int OpenTTYFd (const char* ttypath)
{
// O_NOCTTY is needed to use TIOCSCTTY, which will steal the tty control from any other pgrp
int fd = open (ttypath, O_RDWR| O_NOCTTY| O_NONBLOCK, 0);
if (fd < 0)
ExitWithError ("open");
if (!isatty (fd))
ExitWithMessage (LOGINX_NAME " must run on a tty");
struct stat ttyst;
if (fstat (fd, &ttyst))
ExitWithError ("fstat");
if (!S_ISCHR(ttyst.st_mode))
ExitWithMessage ("the tty is not a character device");
// Establish as session leader and tty owner
//if (_pgrp != tcgetsid(fd))
//if (ioctl (fd, TIOCSCTTY, 1) < 0)
//ExitWithError ("failed to take tty control");
return (fd);
}
static void OpenTTY (const char* ttypath)
{
// First time open tty to make it controlling terminal and vhangup
int fd = OpenTTYFd (ttypath);
// Now close it and vhangup to eliminate all other processes on this tty
close (fd);
for (unsigned f = STDIN_FILENO; f <= STDERR_FILENO; ++f)
close (f);
signal (SIGHUP, SIG_IGN); // To not be killed by vhangup
//vhangup();
signal (SIGHUP, OnSignal); // To be killed by init
// Reopen the tty and establish standard fds
fd = OpenTTYFd (ttypath);
if (fd != STDIN_FILENO) // All fds, except syslog, must be closed at this point
ExitWithError ("open stdin");
if (dup(fd) != STDOUT_FILENO || dup(fd) != STDERR_FILENO)
ExitWithError ("open stdout");
//if (_pgrp != tcgetsid(fd))
//if (ioctl (fd, TIOCSCTTY, 1) < 0)
//ExitWithError ("failed to take tty control");
//if (tcsetpgrp (STDIN_FILENO, _pgrp))
//ExitWithError ("tcsetpgrp");
}
static void ResetTerminal (void)
{
//
// If keyboard is in raw state, unset it
//
int kbmode = K_XLATE;
if (0 == ioctl (STDIN_FILENO, KDGKBMODE, &kbmode))
if (kbmode != K_XLATE && kbmode != K_UNICODE)
ioctl (STDIN_FILENO, KDSKBMODE, kbmode = K_XLATE);
setlocale (LC_ALL, kbmode == K_XLATE ? "C" : "C.UTF-8");
//
// Reset normal terminal settings.
//
struct termios ti;
if (0 > tcgetattr (STDIN_FILENO, &ti))
ExitWithError ("tcgetattr");
// Overwrite known fields with sane defaults
ti.c_iflag = ICRNL| IXON| BRKINT| IUTF8;
ti.c_oflag = ONLCR| OPOST;
ti.c_cflag = HUPCL| CREAD| CS8| B38400;
ti.c_lflag = ISIG| ICANON| ECHO| ECHOE| ECHOK| ECHOCTL| ECHOKE| IEXTEN;
#define TCTRL(k) k-('A'-1)
static const cc_t c_CtrlChar[NCCS] = {
[VINTR] = TCTRL('C'),
[VQUIT] = TCTRL('\\'),
[VERASE] = 127,
[VKILL] = TCTRL('U'),
[VEOF] = TCTRL('D'),
[VMIN] = 1,
[VSUSP] = TCTRL('Z'),
[VREPRINT] = TCTRL('R'),
[VDISCARD] = TCTRL('O'),
[VWERASE] = TCTRL('W'),
[VLNEXT] = TCTRL('V'),
};
memcpy (ti.c_cc, c_CtrlChar, sizeof(ti.c_cc));
// Remove this when non-vc terminals are not supported
const char* termname = getenv("TERM");
if (!termname || 0 != strcmp (termname, "linux"))
ti.c_cc[VERASE] = TCTRL('H');
#undef TCTRL
if (0 > tcsetattr (STDIN_FILENO, TCSANOW, &ti))
ExitWithError ("tcsetattr");
// Clear the screen; [r resets scroll region, [H homes cursor, [J erases
printf ("\e[r\e[H\e[J");
}