release/src/router/busybox/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 GPLv2, see file LICENSE in this source tree.
   8  */
   9 #include "libbb.h"
  10
  11 static void touch(const char *filename)
  12 {
  13         if (access(filename, R_OK | W_OK) == -1)
  14                 close(open(filename, O_WRONLY | O_CREAT, 0664));
  15 }
  16
  17 void FAST_FUNC write_new_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname)
  18 {
  19         struct utmpx utent;
  20         char *id;
  21         unsigned width;
  22
  23         memset(&utent, 0, sizeof(utent));
  24         utent.ut_pid = pid;
  25         utent.ut_type = new_type;
  26         tty_name = skip_dev_pfx(tty_name);
  27         safe_strncpy(utent.ut_line, tty_name, sizeof(utent.ut_line));
  28         if (username)
  29                 safe_strncpy(utent.ut_user, username, sizeof(utent.ut_user));
  30         if (hostname)
  31                 safe_strncpy(utent.ut_host, hostname, sizeof(utent.ut_host));
  32         utent.ut_tv.tv_sec = time(NULL);
  33
  34         /* Invent our own ut_id. ut_id is only 4 chars wide.
  35          * Try to fit something remotely meaningful... */
  36         id = utent.ut_id;
  37         width = sizeof(utent.ut_id);
  38         if (tty_name[0] == 'p') {
  39                 /* if "ptyXXX", map to "pXXX" */
  40                 /* if "pts/XX", map to "p/XX" */
  41                 *id++ = 'p';
  42                 width--;
  43         } /* else: usually it's "ttyXXXX", map to "XXXX" */
  44         if (strlen(tty_name) > 3)
  45                 tty_name += 3;
  46         strncpy(id, tty_name, width);
  47
  48         touch(_PATH_UTMPX);
  49         //utmpxname(_PATH_UTMPX);
  50         setutxent();
  51         /* Append new one (hopefully, unless we collide on ut_id) */
  52         pututxline(&utent);
  53         endutxent();
  54
  55 #if ENABLE_FEATURE_WTMP
  56         /* "man utmp" says wtmp file should *not* be created automagically */
  57         /*touch(bb_path_wtmp_file);*/
  58         updwtmpx(bb_path_wtmp_file, &utent);
  59 #endif
  60 }
  61
  62 /*
  63  * Read "man utmp" to make sense out of it.
  64  */
  65 void FAST_FUNC update_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname)
  66 {
  67         struct utmpx utent;
  68         struct utmpx *utp;
  69
  70         touch(_PATH_UTMPX);
  71         //utmpxname(_PATH_UTMPX);
  72         setutxent();
  73
  74         /* Did init/getty/telnetd/sshd/... create an entry for us?
  75          * It should be (new_type-1), but we'd also reuse
  76          * any other potentially stale xxx_PROCESS entry */
  77         while ((utp = getutxent()) != NULL) {
  78                 if (utp->ut_pid == pid
  79                 // && ut->ut_line[0]
  80                  && utp->ut_id[0] /* must have nonzero id */
  81                  && (  utp->ut_type == INIT_PROCESS
  82                     || utp->ut_type == LOGIN_PROCESS
  83                     || utp->ut_type == USER_PROCESS
  84                     || utp->ut_type == DEAD_PROCESS
  85                     )
  86                 ) {
  87                         if (utp->ut_type >= new_type) {
  88                                 /* Stale record. Nuke hostname */
  89                                 memset(utp->ut_host, 0, sizeof(utp->ut_host));
  90                         }
  91                         /* NB: pututxline (see later) searches for matching utxent
  92                          * using getutxid(utent) - we must not change ut_id
  93                          * if we want *exactly this* record to be overwritten!
  94                          */
  95                         break;
  96                 }
  97         }
  98         //endutxent(); - no need, pututxline can deal with (and actually likes)
  99         //the situation when utmp file is positioned on found record
 100
 101         if (!utp) {
 102                 if (new_type != DEAD_PROCESS)
 103                         write_new_utmp(pid, new_type, tty_name, username, hostname);
 104                 else
 105                         endutxent();
 106                 return;
 107         }
 108
 109         /* Make a copy. We can't use *utp, pututxline's internal getutxid
 110          * will overwrite it before it is used! */
 111         utent = *utp;
 112
 113         utent.ut_type = new_type;
 114         if (tty_name)
 115                 safe_strncpy(utent.ut_line, skip_dev_pfx(tty_name), sizeof(utent.ut_line));
 116         if (username)
 117                 safe_strncpy(utent.ut_user, username, sizeof(utent.ut_user));
 118         if (hostname)
 119                 safe_strncpy(utent.ut_host, hostname, sizeof(utent.ut_host));
 120         utent.ut_tv.tv_sec = time(NULL);
 121
 122         /* Update, or append new one */
 123         //setutxent();
 124         pututxline(&utent);
 125         endutxent();
 126
 127 #if ENABLE_FEATURE_WTMP
 128         /* "man utmp" says wtmp file should *not* be created automagically */
 129         /*touch(bb_path_wtmp_file);*/
 130         updwtmpx(bb_path_wtmp_file, &utent);
 131 #endif
 132 }
 133
 134 /* man utmp:
 135  * When init(8) finds that a process has exited, it locates its utmp entry
 136  * by ut_pid, sets ut_type to DEAD_PROCESS, and clears ut_user, ut_host
 137  * and ut_time with null bytes.
 138  * [same applies to other processes which maintain utmp entries, like telnetd]
 139  *
 140  * We do not bother actually clearing fields:
 141  * it might be interesting to know who was logged in and from where
 142  */
 143 void FAST_FUNC update_utmp_DEAD_PROCESS(pid_t pid)
 144 {
 145         update_utmp(pid, DEAD_PROCESS, NULL, NULL, NULL);
 146 }