misc/mntent_r.c

   1 /* Utilities for reading/writing fstab, mtab, etc.
   2    Copyright (C) 1995-2019 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <alloca.h>
  20 #include <mntent.h>
  21 #include <stdio.h>
  22 #include <stdio_ext.h>
  23 #include <string.h>
  24 #include <sys/types.h>
  25
  26 #define flockfile(s) _IO_flockfile (s)
  27 #define funlockfile(s) _IO_funlockfile (s)
  28
  29 #undef __setmntent
  30 #undef __endmntent
  31 #undef __getmntent_r
  32
  33 /* Prepare to begin reading and/or writing mount table entries from the
  34    beginning of FILE.  MODE is as for `fopen'.  */
  35 FILE *
  36 __setmntent (const char *file, const char *mode)
  37 {
  38   /* Extend the mode parameter with "c" to disable cancellation in the
  39      I/O functions and "e" to set FD_CLOEXEC.  */
  40   size_t modelen = strlen (mode);
  41   char newmode[modelen + 3];
  42   memcpy (mempcpy (newmode, mode, modelen), "ce", 3);
  43   FILE *result = fopen (file, newmode);
  44
  45   if (result != NULL)
  46     /* We do the locking ourselves.  */
  47     __fsetlocking (result, FSETLOCKING_BYCALLER);
  48
  49   return result;
  50 }
  51 libc_hidden_def (__setmntent)
  52 weak_alias (__setmntent, setmntent)
  53
  54
  55 /* Close a stream opened with `setmntent'.  */
  56 int
  57 __endmntent (FILE *stream)
  58 {
  59   if (stream)           /* SunOS 4.x allows for NULL stream */
  60     fclose (stream);
  61   return 1;             /* SunOS 4.x says to always return 1 */
  62 }
  63 libc_hidden_def (__endmntent)
  64 weak_alias (__endmntent, endmntent)
  65
  66
  67 /* Since the values in a line are separated by spaces, a name cannot
  68    contain a space.  Therefore some programs encode spaces in names
  69    by the strings "\040".  We undo the encoding when reading an entry.
  70    The decoding happens in place.  */
  71 static char *
  72 decode_name (char *buf)
  73 {
  74   char *rp = buf;
  75   char *wp = buf;
  76
  77   do
  78     if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '4' && rp[3] == '0')
  79       {
  80         /* \040 is a SPACE.  */
  81         *wp++ = ' ';
  82         rp += 3;
  83       }
  84     else if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '1' && rp[3] == '1')
  85       {
  86         /* \011 is a TAB.  */
  87         *wp++ = '\t';
  88         rp += 3;
  89       }
  90     else if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '1' && rp[3] == '2')
  91       {
  92         /* \012 is a NEWLINE.  */
  93         *wp++ = '\n';
  94         rp += 3;
  95       }
  96     else if (rp[0] == '\\' && rp[1] == '\\')
  97       {
  98         /* We have to escape \\ to be able to represent all characters.  */
  99         *wp++ = '\\';
 100         rp += 1;
 101       }
 102     else if (rp[0] == '\\' && rp[1] == '1' && rp[2] == '3' && rp[3] == '4')
 103       {
 104         /* \134 is also \\.  */
 105         *wp++ = '\\';
 106         rp += 3;
 107       }
 108     else
 109       *wp++ = *rp;
 110   while (*rp++ != '\0');
 111
 112   return buf;
 113 }
 114
 115
 116 /* Read one mount table entry from STREAM.  Returns a pointer to storage
 117    reused on the next call, or null for EOF or error (use feof/ferror to
 118    check).  */
 119 struct mntent *
 120 __getmntent_r (FILE *stream, struct mntent *mp, char *buffer, int bufsiz)
 121 {
 122   char *cp;
 123   char *head;
 124
 125   flockfile (stream);
 126   do
 127     {
 128       char *end_ptr;
 129
 130       if (__fgets_unlocked (buffer, bufsiz, stream) == NULL)
 131         {
 132           funlockfile (stream);
 133           return NULL;
 134         }
 135
 136       end_ptr = strchr (buffer, '\n');
 137       if (end_ptr != NULL)      /* chop newline */
 138         {
 139           /* Do not walk past the start of buffer if it's all whitespace.  */
 140           while (end_ptr != buffer
 141                  && (end_ptr[-1] == ' ' || end_ptr[-1] == '\t'))
 142             end_ptr--;
 143           *end_ptr = '\0';
 144         }
 145       else
 146         {
 147           /* Not the whole line was read.  Do it now but forget it.  */
 148           char tmp[1024];
 149           while (__fgets_unlocked (tmp, sizeof tmp, stream) != NULL)
 150             if (strchr (tmp, '\n') != NULL)
 151               break;
 152         }
 153
 154       head = buffer + strspn (buffer, " \t");
 155       /* skip empty lines and comment lines:  */
 156     }
 157   while (head[0] == '\0' || head[0] == '#');
 158
 159   cp = __strsep (&head, " \t");
 160   mp->mnt_fsname = cp != NULL ? decode_name (cp) : (char *) "";
 161   if (head)
 162     head += strspn (head, " \t");
 163   cp = __strsep (&head, " \t");
 164   mp->mnt_dir = cp != NULL ? decode_name (cp) : (char *) "";
 165   if (head)
 166     head += strspn (head, " \t");
 167   cp = __strsep (&head, " \t");
 168   mp->mnt_type = cp != NULL ? decode_name (cp) : (char *) "";
 169   if (head)
 170     head += strspn (head, " \t");
 171   cp = __strsep (&head, " \t");
 172   mp->mnt_opts = cp != NULL ? decode_name (cp) : (char *) "";
 173   switch (head ? sscanf (head, " %d %d ", &mp->mnt_freq, &mp->mnt_passno) : 0)
 174     {
 175     case 0:
 176       mp->mnt_freq = 0;
 177       /* Fall through.  */
 178     case 1:
 179       mp->mnt_passno = 0;
 180       /* Fall through.  */
 181     case 2:
 182       break;
 183     }
 184   funlockfile (stream);
 185
 186   return mp;
 187 }
 188 libc_hidden_def (__getmntent_r)
 189 weak_alias (__getmntent_r, getmntent_r)
 190
 191
 192 /* We have to use an encoding for names if they contain spaces or tabs.
 193    To be able to represent all characters we also have to escape the
 194    backslash itself.  This "function" must be a macro since we use
 195    `alloca'.  */
 196 #define encode_name(name) \
 197   do {                                                                        \
 198     const char *rp = name;                                                    \
 199                                                                               \
 200     while (*rp != '\0')                                                       \
 201       if (*rp == ' ' || *rp == '\t' || *rp == '\n' || *rp == '\\')            \
 202         break;                                                                \
 203       else                                                                    \
 204         ++rp;                                                                 \
 205                                                                               \
 206     if (*rp != '\0')                                                          \
 207       {                                                                       \
 208         /* In the worst case the length of the string can increase to         \
 209            four times the current length.  */                                 \
 210         char *wp;                                                             \
 211                                                                               \
 212         rp = name;                                                            \
 213         name = wp = (char *) alloca (strlen (name) * 4 + 1);                  \
 214                                                                               \
 215         do                                                                    \
 216           if (*rp == ' ')                                                     \
 217             {                                                                 \
 218               *wp++ = '\\';                                                   \
 219               *wp++ = '0';                                                    \
 220               *wp++ = '4';                                                    \
 221               *wp++ = '0';                                                    \
 222             }                                                                 \
 223           else if (*rp == '\t')                                               \
 224             {                                                                 \
 225               *wp++ = '\\';                                                   \
 226               *wp++ = '0';                                                    \
 227               *wp++ = '1';                                                    \
 228               *wp++ = '1';                                                    \
 229             }                                                                 \
 230           else if (*rp == '\n')                                               \
 231             {                                                                 \
 232               *wp++ = '\\';                                                   \
 233               *wp++ = '0';                                                    \
 234               *wp++ = '1';                                                    \
 235               *wp++ = '2';                                                    \
 236             }                                                                 \
 237           else if (*rp == '\\')                                               \
 238             {                                                                 \
 239               *wp++ = '\\';                                                   \
 240               *wp++ = '\\';                                                   \
 241             }                                                                 \
 242           else                                                                \
 243             *wp++ = *rp;                                                      \
 244         while (*rp++ != '\0');                                                \
 245       }                                                                       \
 246   } while (0)
 247
 248
 249 /* Write the mount table entry described by MNT to STREAM.
 250    Return zero on success, nonzero on failure.  */
 251 int
 252 __addmntent (FILE *stream, const struct mntent *mnt)
 253 {
 254   struct mntent mntcopy = *mnt;
 255   if (fseek (stream, 0, SEEK_END))
 256     return 1;
 257
 258   /* Encode spaces and tabs in the names.  */
 259   encode_name (mntcopy.mnt_fsname);
 260   encode_name (mntcopy.mnt_dir);
 261   encode_name (mntcopy.mnt_type);
 262   encode_name (mntcopy.mnt_opts);
 263
 264   return (fprintf (stream, "%s %s %s %s %d %d\n",
 265                    mntcopy.mnt_fsname,
 266                    mntcopy.mnt_dir,
 267                    mntcopy.mnt_type,
 268                    mntcopy.mnt_opts,
 269                    mntcopy.mnt_freq,
 270                    mntcopy.mnt_passno) < 0
 271           || fflush (stream) != 0);
 272 }
 273 weak_alias (__addmntent, addmntent)
 274
 275
 276 /* Search MNT->mnt_opts for an option matching OPT.
 277    Returns the address of the substring, or null if none found.  */
 278 char *
 279 __hasmntopt (const struct mntent *mnt, const char *opt)
 280 {
 281   const size_t optlen = strlen (opt);
 282   char *rest = mnt->mnt_opts, *p;
 283
 284   while ((p = strstr (rest, opt)) != NULL)
 285     {
 286       if ((p == rest || p[-1] == ',')
 287           && (p[optlen] == '\0' || p[optlen] == '=' || p[optlen] == ','))
 288         return p;
 289
 290       rest = strchr (p, ',');
 291       if (rest == NULL)
 292         break;
 293       ++rest;
 294     }
 295
 296   return NULL;
 297 }
 298 libc_hidden_def (__hasmntopt)
 299 weak_alias (__hasmntopt, hasmntopt)