1/* Utilities for reading/writing fstab, mtab, etc.
2 Copyright (C) 1995-2020 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 <https://www.gnu.org/licenses/>. */
18
19#include <alloca.h>
20#include <mntent.h>
21#include <stdbool.h>
22#include <stdio.h>
23#include <stdio_ext.h>
24#include <string.h>
25#include <sys/types.h>
26
27#define flockfile(s) _IO_flockfile (s)
28#define funlockfile(s) _IO_funlockfile (s)
29
30#undef __setmntent
31#undef __endmntent
32#undef __getmntent_r
33
34/* Prepare to begin reading and/or writing mount table entries from the
35 beginning of FILE. MODE is as for `fopen'. */
36FILE *
37__setmntent (const char *file, const char *mode)
38{
39 /* Extend the mode parameter with "c" to disable cancellation in the
40 I/O functions and "e" to set FD_CLOEXEC. */
41 size_t modelen = strlen (mode);
42 char newmode[modelen + 3];
43 memcpy (mempcpy (newmode, mode, modelen), "ce", 3);
44 FILE *result = fopen (file, newmode);
45
46 if (result != NULL)
47 /* We do the locking ourselves. */
48 __fsetlocking (result, FSETLOCKING_BYCALLER);
49
50 return result;
51}
52libc_hidden_def (__setmntent)
53weak_alias (__setmntent, setmntent)
54
55
56/* Close a stream opened with `setmntent'. */
57int
58__endmntent (FILE *stream)
59{
60 if (stream) /* SunOS 4.x allows for NULL stream */
61 fclose (stream);
62 return 1; /* SunOS 4.x says to always return 1 */
63}
64libc_hidden_def (__endmntent)
65weak_alias (__endmntent, endmntent)
66
67
68/* Since the values in a line are separated by spaces, a name cannot
69 contain a space. Therefore some programs encode spaces in names
70 by the strings "\040". We undo the encoding when reading an entry.
71 The decoding happens in place. */
72static char *
73decode_name (char *buf)
74{
75 char *rp = buf;
76 char *wp = buf;
77
78 do
79 if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '4' && rp[3] == '0')
80 {
81 /* \040 is a SPACE. */
82 *wp++ = ' ';
83 rp += 3;
84 }
85 else if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '1' && rp[3] == '1')
86 {
87 /* \011 is a TAB. */
88 *wp++ = '\t';
89 rp += 3;
90 }
91 else if (rp[0] == '\\' && rp[1] == '0' && rp[2] == '1' && rp[3] == '2')
92 {
93 /* \012 is a NEWLINE. */
94 *wp++ = '\n';
95 rp += 3;
96 }
97 else if (rp[0] == '\\' && rp[1] == '\\')
98 {
99 /* We have to escape \\ to be able to represent all characters. */
100 *wp++ = '\\';
101 rp += 1;
102 }
103 else if (rp[0] == '\\' && rp[1] == '1' && rp[2] == '3' && rp[3] == '4')
104 {
105 /* \134 is also \\. */
106 *wp++ = '\\';
107 rp += 3;
108 }
109 else
110 *wp++ = *rp;
111 while (*rp++ != '\0');
112
113 return buf;
114}
115
116static bool
117get_mnt_entry (FILE *stream, struct mntent *mp, char *buffer, int bufsiz)
118{
119 char *cp;
120 char *head;
121
122 do
123 {
124 char *end_ptr;
125
126 if (__fgets_unlocked (buffer, bufsiz, stream) == NULL)
127 return false;
128
129 end_ptr = strchr (buffer, '\n');
130 if (end_ptr != NULL) /* chop newline */
131 {
132 /* Do not walk past the start of buffer if it's all whitespace. */
133 while (end_ptr != buffer
134 && (end_ptr[-1] == ' ' || end_ptr[-1] == '\t'))
135 end_ptr--;
136 *end_ptr = '\0';
137 }
138 else
139 {
140 /* Not the whole line was read. Do it now but forget it. */
141 char tmp[1024];
142 while (__fgets_unlocked (tmp, sizeof tmp, stream) != NULL)
143 if (strchr (tmp, '\n') != NULL)
144 break;
145 }
146
147 head = buffer + strspn (buffer, " \t");
148 /* skip empty lines and comment lines: */
149 }
150 while (head[0] == '\0' || head[0] == '#');
151
152 cp = __strsep (&head, " \t");
153 mp->mnt_fsname = cp != NULL ? decode_name (cp) : (char *) "";
154 if (head)
155 head += strspn (head, " \t");
156 cp = __strsep (&head, " \t");
157 mp->mnt_dir = cp != NULL ? decode_name (cp) : (char *) "";
158 if (head)
159 head += strspn (head, " \t");
160 cp = __strsep (&head, " \t");
161 mp->mnt_type = cp != NULL ? decode_name (cp) : (char *) "";
162 if (head)
163 head += strspn (head, " \t");
164 cp = __strsep (&head, " \t");
165 mp->mnt_opts = cp != NULL ? decode_name (cp) : (char *) "";
166 switch (head ? sscanf (head, " %d %d ", &mp->mnt_freq, &mp->mnt_passno) : 0)
167 {
168 case 0:
169 mp->mnt_freq = 0;
170 /* Fall through. */
171 case 1:
172 mp->mnt_passno = 0;
173 /* Fall through. */
174 case 2:
175 break;
176 }
177
178 return true;
179}
180
181/* Read one mount table entry from STREAM. Returns a pointer to storage
182 reused on the next call, or null for EOF or error (use feof/ferror to
183 check). */
184struct mntent *
185__getmntent_r (FILE *stream, struct mntent *mp, char *buffer, int bufsiz)
186{
187 struct mntent *result;
188
189 flockfile (stream);
190 while (true)
191 if (get_mnt_entry (stream, mp, buffer, bufsiz))
192 {
193 /* If the file system is autofs look for a mount option hint
194 ("ignore") to skip the entry. */
195 if (strcmp (mp->mnt_type, "autofs") == 0 && __hasmntopt (mp, "ignore"))
196 memset (mp, 0, sizeof (*mp));
197 else
198 {
199 result = mp;
200 break;
201 }
202 }
203 else
204 {
205 result = NULL;
206 break;
207 }
208 funlockfile (stream);
209
210 return result;
211}
212libc_hidden_def (__getmntent_r)
213weak_alias (__getmntent_r, getmntent_r)
214
215
216/* We have to use an encoding for names if they contain spaces or tabs.
217 To be able to represent all characters we also have to escape the
218 backslash itself. This "function" must be a macro since we use
219 `alloca'. */
220#define encode_name(name) \
221 do { \
222 const char *rp = name; \
223 \
224 while (*rp != '\0') \
225 if (*rp == ' ' || *rp == '\t' || *rp == '\n' || *rp == '\\') \
226 break; \
227 else \
228 ++rp; \
229 \
230 if (*rp != '\0') \
231 { \
232 /* In the worst case the length of the string can increase to \
233 four times the current length. */ \
234 char *wp; \
235 \
236 rp = name; \
237 name = wp = (char *) alloca (strlen (name) * 4 + 1); \
238 \
239 do \
240 if (*rp == ' ') \
241 { \
242 *wp++ = '\\'; \
243 *wp++ = '0'; \
244 *wp++ = '4'; \
245 *wp++ = '0'; \
246 } \
247 else if (*rp == '\t') \
248 { \
249 *wp++ = '\\'; \
250 *wp++ = '0'; \
251 *wp++ = '1'; \
252 *wp++ = '1'; \
253 } \
254 else if (*rp == '\n') \
255 { \
256 *wp++ = '\\'; \
257 *wp++ = '0'; \
258 *wp++ = '1'; \
259 *wp++ = '2'; \
260 } \
261 else if (*rp == '\\') \
262 { \
263 *wp++ = '\\'; \
264 *wp++ = '\\'; \
265 } \
266 else \
267 *wp++ = *rp; \
268 while (*rp++ != '\0'); \
269 } \
270 } while (0)
271
272
273/* Write the mount table entry described by MNT to STREAM.
274 Return zero on success, nonzero on failure. */
275int
276__addmntent (FILE *stream, const struct mntent *mnt)
277{
278 struct mntent mntcopy = *mnt;
279 if (fseek (stream, 0, SEEK_END))
280 return 1;
281
282 /* Encode spaces and tabs in the names. */
283 encode_name (mntcopy.mnt_fsname);
284 encode_name (mntcopy.mnt_dir);
285 encode_name (mntcopy.mnt_type);
286 encode_name (mntcopy.mnt_opts);
287
288 return (fprintf (stream, "%s %s %s %s %d %d\n",
289 mntcopy.mnt_fsname,
290 mntcopy.mnt_dir,
291 mntcopy.mnt_type,
292 mntcopy.mnt_opts,
293 mntcopy.mnt_freq,
294 mntcopy.mnt_passno) < 0
295 || fflush (stream) != 0);
296}
297weak_alias (__addmntent, addmntent)
298
299
300/* Search MNT->mnt_opts for an option matching OPT.
301 Returns the address of the substring, or null if none found. */
302char *
303__hasmntopt (const struct mntent *mnt, const char *opt)
304{
305 const size_t optlen = strlen (opt);
306 char *rest = mnt->mnt_opts, *p;
307
308 while ((p = strstr (rest, opt)) != NULL)
309 {
310 if ((p == rest || p[-1] == ',')
311 && (p[optlen] == '\0' || p[optlen] == '=' || p[optlen] == ','))
312 return p;
313
314 rest = strchr (p, ',');
315 if (rest == NULL)
316 break;
317 ++rest;
318 }
319
320 return NULL;
321}
322libc_hidden_def (__hasmntopt)
323weak_alias (__hasmntopt, hasmntopt)
324