misc/mntent_r.c

   1 /* Utilities for reading/writing fstab, mtab, etc.
   2    Copyright (C) 1995-2018 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     case 1:
 178       mp->mnt_passno = 0;
 179     case 2:
 180       break;
 181     }
 182   funlockfile (stream);
 183
 184   return mp;
 185 }
 186 libc_hidden_def (__getmntent_r)
 187 weak_alias (__getmntent_r, getmntent_r)
 188
 189
 190 /* We have to use an encoding for names if they contain spaces or tabs.
 191    To be able to represent all characters we also have to escape the
 192    backslash itself.  This "function" must be a macro since we use
 193    `alloca'.  */
 194 #define encode_name(name) \
 195   do {                                                                        \
 196     const char *rp = name;                                                    \
 197                                                                               \
 198     while (*rp != '\0')                                                       \
 199       if (*rp == ' ' || *rp == '\t' || *rp == '\n' || *rp == '\\')            \
 200         break;                                                                \
 201       else                                                                    \
 202         ++rp;                                                                 \
 203                                                                               \
 204     if (*rp != '\0')                                                          \
 205       {                                                                       \
 206         /* In the worst case the length of the string can increase to         \
 207            four times the current length.  */                                 \
 208         char *wp;                                                             \
 209                                                                               \
 210         rp = name;                                                            \
 211         name = wp = (char *) alloca (strlen (name) * 4 + 1);                  \
 212                                                                               \
 213         do                                                                    \
 214           if (*rp == ' ')                                                     \
 215             {                                                                 \
 216               *wp++ = '\\';                                                   \
 217               *wp++ = '0';                                                    \
 218               *wp++ = '4';                                                    \
 219               *wp++ = '0';                                                    \
 220             }                                                                 \
 221           else if (*rp == '\t')                                               \
 222             {                                                                 \
 223               *wp++ = '\\';                                                   \
 224               *wp++ = '0';                                                    \
 225               *wp++ = '1';                                                    \
 226               *wp++ = '1';                                                    \
 227             }                                                                 \
 228           else if (*rp == '\n')                                               \
 229             {                                                                 \
 230               *wp++ = '\\';                                                   \
 231               *wp++ = '0';                                                    \
 232               *wp++ = '1';                                                    \
 233               *wp++ = '2';                                                    \
 234             }                                                                 \
 235           else if (*rp == '\\')                                               \
 236             {                                                                 \
 237               *wp++ = '\\';                                                   \
 238               *wp++ = '\\';                                                   \
 239             }                                                                 \
 240           else                                                                \
 241             *wp++ = *rp;                                                      \
 242         while (*rp++ != '\0');                                                \
 243       }                                                                       \
 244   } while (0)
 245
 246
 247 /* Write the mount table entry described by MNT to STREAM.
 248    Return zero on success, nonzero on failure.  */
 249 int
 250 __addmntent (FILE *stream, const struct mntent *mnt)
 251 {
 252   struct mntent mntcopy = *mnt;
 253   if (fseek (stream, 0, SEEK_END))
 254     return 1;
 255
 256   /* Encode spaces and tabs in the names.  */
 257   encode_name (mntcopy.mnt_fsname);
 258   encode_name (mntcopy.mnt_dir);
 259   encode_name (mntcopy.mnt_type);
 260   encode_name (mntcopy.mnt_opts);
 261
 262   return (fprintf (stream, "%s %s %s %s %d %d\n",
 263                    mntcopy.mnt_fsname,
 264                    mntcopy.mnt_dir,
 265                    mntcopy.mnt_type,
 266                    mntcopy.mnt_opts,
 267                    mntcopy.mnt_freq,
 268                    mntcopy.mnt_passno) < 0
 269           || fflush (stream) != 0);
 270 }
 271 weak_alias (__addmntent, addmntent)
 272
 273
 274 /* Search MNT->mnt_opts for an option matching OPT.
 275    Returns the address of the substring, or null if none found.  */
 276 char *
 277 __hasmntopt (const struct mntent *mnt, const char *opt)
 278 {
 279   const size_t optlen = strlen (opt);
 280   char *rest = mnt->mnt_opts, *p;
 281
 282   while ((p = strstr (rest, opt)) != NULL)
 283     {
 284       if ((p == rest || p[-1] == ',')
 285           && (p[optlen] == '\0' || p[optlen] == '=' || p[optlen] == ','))
 286         return p;
 287
 288       rest = strchr (p, ',');
 289       if (rest == NULL)
 290         break;
 291       ++rest;
 292     }
 293
 294   return NULL;
 295 }
 296 libc_hidden_def (__hasmntopt)
 297 weak_alias (__hasmntopt, hasmntopt)