libbb/utmp.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * utmp/wtmp support routines.
   4  *
   5  * Copyright (C) 2010 Denys Vlasenko
   6  *
   7  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
   8  */
   9 #include "libbb.h"
  10 #include <utmp.h>
  11
  12 static void touch(const char *filename)
  13 {
  14         if (access(filename, R_OK | W_OK) == -1)
  15                 close(open(filename, O_WRONLY | O_CREAT, 0664));
  16 }
  17
  18 void FAST_FUNC write_new_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname)
  19 {
  20         struct utmp utent;
  21         char *id;
  22         unsigned width;
  23
  24         memset(&utent, 0, sizeof(utent));
  25         utent.ut_pid = pid;
  26         utent.ut_type = new_type;
  27         tty_name = skip_dev_pfx(tty_name);
  28         safe_strncpy(utent.ut_line, tty_name, sizeof(utent.ut_line));
  29         if (username)
  30                 safe_strncpy(utent.ut_user, username, sizeof(utent.ut_user));
  31         if (hostname)
  32                 safe_strncpy(utent.ut_host, hostname, sizeof(utent.ut_host));
  33         utent.ut_tv.tv_sec = time(NULL);
  34
  35         /* Invent our own ut_id. ut_id is only 4 chars wide.
  36          * Try to fit something remotely meaningful... */
  37         id = utent.ut_id;
  38         width = sizeof(utent.ut_id);
  39         if (tty_name[0] == 'p') {
  40                 /* if "ptyXXX", map to "pXXX" */
  41                 /* if "pts/XX", map to "p/XX" */
  42                 *id++ = 'p';
  43                 width--;
  44         } /* else: usually it's "ttyXXXX", map to "XXXX" */
  45         if (strlen(tty_name) > 3)
  46                 tty_name += 3;
  47         strncpy(id, tty_name, width);
  48
  49         touch(_PATH_UTMP);
  50         //utmpname(_PATH_UTMP);
  51         setutent();
  52         /* Append new one (hopefully, unless we collide on ut_id) */
  53         pututline(&utent);
  54         endutent();
  55
  56 #if ENABLE_FEATURE_WTMP
  57         /* "man utmp" says wtmp file should *not* be created automagically */
  58         /*touch(bb_path_wtmp_file);*/
  59         updwtmp(bb_path_wtmp_file, &utent);
  60 #endif
  61 }
  62
  63 /*
  64  * Read "man utmp" to make sense out of it.
  65  */
  66 void FAST_FUNC update_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname)
  67 {
  68         struct utmp utent;
  69         struct utmp *utp;
  70
  71         touch(_PATH_UTMP);
  72         //utmpname(_PATH_UTMP);
  73         setutent();
  74
  75         /* Did init/getty/telnetd/sshd/... create an entry for us?
  76          * It should be (new_type-1), but we'd also reuse
  77          * any other potentially stale xxx_PROCESS entry */
  78         while ((utp = getutent()) != NULL) {
  79                 if (utp->ut_pid == pid
  80                 // && ut->ut_line[0]
  81                  && utp->ut_id[0] /* must have nonzero id */
  82                  && (  utp->ut_type == INIT_PROCESS
  83                     || utp->ut_type == LOGIN_PROCESS
  84                     || utp->ut_type == USER_PROCESS
  85                     || utp->ut_type == DEAD_PROCESS
  86                     )
  87                 ) {
  88                         if (utp->ut_type >= new_type) {
  89                                 /* Stale record. Nuke hostname */
  90                                 memset(utp->ut_host, 0, sizeof(utp->ut_host));
  91                         }
  92                         /* NB: pututline (see later) searches for matching utent
  93                          * using getutid(utent) - we must not change ut_id
  94                          * if we want *exactly this* record to be overwritten!
  95                          */
  96                         break;
  97                 }
  98         }
  99         //endutent(); - no need, pututline can deal with (and actually likes)
 100         //the situation when utmp file is positioned on found record
 101
 102         if (!utp) {
 103                 if (new_type != DEAD_PROCESS)
 104                         write_new_utmp(pid, new_type, tty_name, username, hostname);
 105                 else
 106                         endutent();
 107                 return;
 108         }
 109
 110         /* Make a copy. We can't use *utp, pututline's internal getutid
 111          * will overwrite it before it is used! */
 112         utent = *utp;
 113
 114         utent.ut_type = new_type;
 115         if (tty_name)
 116                 safe_strncpy(utent.ut_line, skip_dev_pfx(tty_name), sizeof(utent.ut_line));
 117         if (username)
 118                 safe_strncpy(utent.ut_user, username, sizeof(utent.ut_user));
 119         if (hostname)
 120                 safe_strncpy(utent.ut_host, hostname, sizeof(utent.ut_host));
 121         utent.ut_tv.tv_sec = time(NULL);
 122
 123         /* Update, or append new one */
 124         //setutent();
 125         pututline(&utent);
 126         endutent();
 127
 128 #if ENABLE_FEATURE_WTMP
 129         /* "man utmp" says wtmp file should *not* be created automagically */
 130         /*touch(bb_path_wtmp_file);*/
 131         updwtmp(bb_path_wtmp_file, &utent);
 132 #endif
 133 }