lib/readutmp.c

   1 /* GNU's read utmp module.
   2
   3    Copyright (C) 1992-2001, 2003-2006, 2009-2011 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by jla; revised by djm */
  19
  20 #include <config.h>
  21
  22 #include "readutmp.h"
  23
  24 #include <errno.h>
  25 #include <stdio.h>
  26
  27 #include <sys/types.h>
  28 #include <sys/stat.h>
  29 #include <signal.h>
  30 #include <stdbool.h>
  31 #include <string.h>
  32 #include <stdlib.h>
  33 #include <stdint.h>
  34
  35 #include "xalloc.h"
  36
  37 #if USE_UNLOCKED_IO
  38 # include "unlocked-io.h"
  39 #endif
  40
  41 /* Copy UT->ut_name into storage obtained from malloc.  Then remove any
  42    trailing spaces from the copy, NUL terminate it, and return the copy.  */
  43
  44 char *
  45 extract_trimmed_name (const STRUCT_UTMP *ut)
  46 {
  47   char *p, *trimmed_name;
  48
  49   trimmed_name = xmalloc (sizeof (UT_USER (ut)) + 1);
  50   strncpy (trimmed_name, UT_USER (ut), sizeof (UT_USER (ut)));
  51   /* Append a trailing NUL.  Some systems pad names shorter than the
  52      maximum with spaces, others pad with NULs.  Remove any trailing
  53      spaces.  */
  54   trimmed_name[sizeof (UT_USER (ut))] = '\0';
  55   for (p = trimmed_name + strlen (trimmed_name);
  56        trimmed_name < p && p[-1] == ' ';
  57        *--p = '\0')
  58     continue;
  59   return trimmed_name;
  60 }
  61
  62 /* Is the utmp entry U desired by the user who asked for OPTIONS?  */
  63
  64 static inline bool
  65 desirable_utmp_entry (STRUCT_UTMP const *u, int options)
  66 {
  67   bool user_proc = IS_USER_PROCESS (u);
  68   if ((options & READ_UTMP_USER_PROCESS) && !user_proc)
  69     return false;
  70   if ((options & READ_UTMP_CHECK_PIDS)
  71       && user_proc
  72       && (UT_PID (u) <= 0
  73           || (kill (UT_PID (u), 0) < 0 && errno == ESRCH)))
  74     return false;
  75   return true;
  76 }
  77
  78 /* Read the utmp entries corresponding to file FILE into freshly-
  79    malloc'd storage, set *UTMP_BUF to that pointer, set *N_ENTRIES to
  80    the number of entries, and return zero.  If there is any error,
  81    return -1, setting errno, and don't modify the parameters.
  82    If OPTIONS & READ_UTMP_CHECK_PIDS is nonzero, omit entries whose
  83    process-IDs do not currently exist.  */
  84
  85 #ifdef UTMP_NAME_FUNCTION
  86
  87 int
  88 read_utmp (char const *file, size_t *n_entries, STRUCT_UTMP **utmp_buf,
  89            int options)
  90 {
  91   size_t n_read = 0;
  92   size_t n_alloc = 0;
  93   STRUCT_UTMP *utmp = NULL;
  94   STRUCT_UTMP *u;
  95
  96   /* Ignore the return value for now.
  97      Solaris' utmpname returns 1 upon success -- which is contrary
  98      to what the GNU libc version does.  In addition, older GNU libc
  99      versions are actually void.   */
 100   UTMP_NAME_FUNCTION (file);
 101
 102   SET_UTMP_ENT ();
 103
 104   while ((u = GET_UTMP_ENT ()) != NULL)
 105     if (desirable_utmp_entry (u, options))
 106       {
 107         if (n_read == n_alloc)
 108           utmp = x2nrealloc (utmp, &n_alloc, sizeof *utmp);
 109
 110         utmp[n_read++] = *u;
 111       }
 112
 113   END_UTMP_ENT ();
 114
 115   *n_entries = n_read;
 116   *utmp_buf = utmp;
 117
 118   return 0;
 119 }
 120
 121 #else
 122
 123 int
 124 read_utmp (char const *file, size_t *n_entries, STRUCT_UTMP **utmp_buf,
 125            int options)
 126 {
 127   size_t n_read = 0;
 128   size_t n_alloc = 0;
 129   STRUCT_UTMP *utmp = NULL;
 130   int saved_errno;
 131   FILE *f = fopen (file, "r");
 132
 133   if (! f)
 134     return -1;
 135
 136   for (;;)
 137     {
 138       if (n_read == n_alloc)
 139         utmp = x2nrealloc (utmp, &n_alloc, sizeof *utmp);
 140       if (fread (&utmp[n_read], sizeof utmp[n_read], 1, f) == 0)
 141         break;
 142       n_read += desirable_utmp_entry (&utmp[n_read], options);
 143     }
 144
 145   saved_errno = ferror (f) ? errno : 0;
 146   if (fclose (f) != 0)
 147     saved_errno = errno;
 148   if (saved_errno != 0)
 149     {
 150       free (utmp);
 151       errno = saved_errno;
 152       return -1;
 153     }
 154
 155   *n_entries = n_read;
 156   *utmp_buf = utmp;
 157
 158   return 0;
 159 }
 160
 161 #endif