src/vlock-new.c

   1 /* vlock-new.c -- console allocation routine for vlock,
   2  *                the VT locking program for linux
   3  *
   4  * This program is copyright (C) 2007 Frank Benkstein, and is free
   5  * software which is freely distributable under the terms of the
   6  * GNU General Public License version 2, included as the file COPYING in this
   7  * distribution.  It is NOT public domain software, and any
   8  * redistribution not permitted by the GNU General Public License is
   9  * expressly forbidden without prior written permission from
  10  * the author.
  11  *
  12  */
  13
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <unistd.h>
  17 #include <fcntl.h>
  18 #include <sys/ioctl.h>
  19 #include <sys/wait.h>
  20 #include <sys/types.h>
  21
  22 #ifdef __FreeBSD__
  23 #include <sys/consio.h>
  24 #else
  25 #include <sys/vt.h>
  26 #endif /* __FreeBSD__ */
  27
  28 #include "vlock.h"
  29
  30 /* Get the currently active console from the given
  31  * console file descriptor.  Returns console number
  32  * (starting from 1) on success, -1 on error. */
  33 #ifdef __FreeBSD__
  34 static int get_active_console(int consfd) {
  35   int n;
  36
  37   if (ioctl(consfd, VT_GETACTIVE, &n) == 0)
  38     return n;
  39   else
  40     return -1;
  41 }
  42 #else
  43 static int get_active_console(int consfd) {
  44   struct vt_stat vtstate;
  45
  46   /* get the virtual console status */
  47   if (ioctl(consfd, VT_GETSTATE, &vtstate) == 0)
  48     return vtstate.v_active;
  49   else
  50     return -1;
  51 }
  52 #endif
  53
  54 /* Get the device name for the given console number.
  55  * Returns the device name or NULL on error. */
  56 static char *get_console_name(int n) {
  57   static char name[sizeof VTNAME + 2];
  58   size_t namelen;
  59
  60   if (n <= 0)
  61     return NULL;
  62
  63   /* format the virtual terminal filename from the number */
  64 #ifdef __FreeBSD__
  65   namelen = snprintf(name, sizeof name, VTNAME, n-1);
  66 #else
  67   namelen = snprintf(name, sizeof name, VTNAME, n);
  68 #endif
  69
  70   if (namelen > sizeof name) {
  71     fprintf(stderr, "vlock-new: virtual terminal number too large\n");
  72     return NULL;
  73   }
  74   else {
  75     return name;
  76   }
  77 }
  78
  79 /* Run vlock-all on a new console. */
  80 int main(void) {
  81   int consfd = STDIN_FILENO;
  82   int old_vtno;
  83   int vtno;
  84   int vtfd;
  85   char *vtname;
  86   int pid = -1;
  87   int status;
  88
  89   /* get the number of the currently active console */
  90   old_vtno = get_active_console(consfd);
  91
  92   if (old_vtno < 0) {
  93     /* stdin is does not a virtual console */
  94     (void) close(consfd);
  95
  96     /* XXX: add optional PAM check here */
  97
  98     /* open the virtual console directly */
  99     if ((consfd = open(CONSOLE, O_RDWR)) < 0) {
 100       perror("vlock-new: cannot open virtual console");
 101       exit (111);
 102     }
 103
 104     /* get the number of the currently active console, again */
 105     old_vtno = get_active_console(consfd);
 106
 107     if (old_vtno < 0) {
 108       perror("vlock-new: could not find out currently active console");
 109       exit (111);
 110     }
 111   }
 112
 113   /* get a free virtual terminal number */
 114   if (ioctl(consfd, VT_OPENQRY, &vtno) < 0)  {
 115     perror("vlock-new: could not find a free virtual terminal");
 116     exit (111);
 117   }
 118
 119   /* get the device name for the new virtual console */
 120   vtname = get_console_name(vtno);
 121
 122   /* open the free virtual terminal */
 123   if ((vtfd = open(vtname, O_RDWR)) < 0) {
 124     perror("vlock-new: cannot open new console");
 125     exit (111);
 126   }
 127
 128   /* switch to the virtual terminal */
 129   if (ioctl(consfd, VT_ACTIVATE, vtno) < 0
 130       || ioctl(consfd, VT_WAITACTIVE, vtno) < 0) {
 131     perror("vlock-new: could not activate new terminal");
 132     exit (111);
 133   }
 134
 135   pid = fork();
 136
 137   if (pid == 0) {
 138     /* child */
 139
 140     /* close the virtual console file descriptor */
 141     (void) close(consfd);
 142
 143     /* drop privleges */
 144     (void) setuid(getuid());
 145
 146     /* make this process a session leader */
 147     (void) setsid();
 148
 149     /* make new virtual terminal controlling tty of this process */
 150     if (ioctl(vtfd, TIOCSCTTY, 1) < 0) {
 151       perror("vlock-new: could not set controlling terminal");
 152       _exit(111);
 153     }
 154
 155     /* redirect stdio */
 156     dup2(vtfd, STDIN_FILENO);
 157     dup2(vtfd, STDOUT_FILENO);
 158     dup2(vtfd, STDERR_FILENO);
 159     close(vtfd);
 160
 161     /* run child */
 162     execl(VLOCK_ALL, VLOCK_ALL, (char *) NULL);
 163     perror("vlock-new: exec of vlock-all failed");
 164     _exit(127);
 165   } else if (pid < 0) {
 166     perror("vlock-new: could not create child process");
 167   }
 168
 169   /* close virtual terminal file descriptor */
 170   (void) close(vtfd);
 171
 172   if (pid > 0 && waitpid(pid, &status, 0) < 0) {
 173     perror("vlock-new: child process missing");
 174     pid = -1;
 175   }
 176
 177   /* switch back to former virtual terminal */
 178   if (ioctl(consfd, VT_ACTIVATE, old_vtno) < 0
 179       || ioctl(consfd, VT_WAITACTIVE, old_vtno) < 0)
 180     perror("vlock-new: could not activate previous console");
 181
 182 #ifndef __FreeBSD__
 183   /* deallocate virtual terminal */
 184   if (ioctl(consfd, VT_DISALLOCATE, vtno) < 0)
 185     perror("vlock-new: could not disallocate console");
 186 #endif
 187
 188   (void) close(consfd);
 189
 190   /* exit with the exit status of the child or 128+signal if it was killed */
 191   if (pid > 0) {
 192     if (WIFEXITED(status))
 193       exit (WEXITSTATUS(status));
 194     else if (WIFSIGNALED(status))
 195       exit (128+WTERMSIG(status));
 196   }
 197
 198   return 0;
 199 }