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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: key-file.c,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
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4 | * |
5 | * System-dependent key filing operations |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
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30 | /*----- Header files ------------------------------------------------------*/ |
31 | |
32 | #include <errno.h> |
33 | #include <stdio.h> |
34 | #include <stdlib.h> |
35 | #include <string.h> |
36 | |
37 | #include <sys/types.h> |
38 | #include <sys/time.h> |
39 | #include <sys/stat.h> |
40 | #include <unistd.h> |
41 | #include <fcntl.h> |
42 | |
43 | #include <mLib/dstr.h> |
44 | #include <mLib/lock.h> |
45 | |
46 | #include "key.h" |
47 | |
48 | /*----- Main code ---------------------------------------------------------*/ |
49 | |
50 | /* --- @fdcopy@ --- * |
51 | * |
52 | * Arguments: @int source@ = source file descriptor |
53 | * @int dest@ = destination file descriptor |
54 | * |
55 | * Returns: Zero if OK, nonzero otherwise. |
56 | * |
57 | * Use: Copies data from one file descriptor to another. |
58 | */ |
59 | |
60 | static int fdcopy(int source, int dest) |
61 | { |
62 | char buf[4096]; |
63 | |
64 | if (lseek(source, 0, SEEK_SET) < 0|| |
65 | lseek(dest, 0, SEEK_SET) < 0 || |
66 | ftruncate(dest, 0) < 0) |
67 | return (-1); |
68 | for (;;) { |
69 | int n = read(source, buf, sizeof(buf)); |
70 | if (n < 0) |
71 | return (-1); |
72 | else if (n == 0) |
73 | break; |
74 | else if (write(dest, buf, n) < 0) |
75 | return (-1); |
76 | } |
77 | return (0); |
78 | } |
79 | |
80 | /* --- @key_save@ --- * |
81 | * |
82 | * Arguments: @key_file *f@ = pointer to key file block |
83 | * |
84 | * Returns: A @KWRITE_@ code indicating how well it worked. |
85 | * |
86 | * Use: Writes a key file's data back to the actual file. This code |
87 | * is extremely careful about error handling. It should usually |
88 | * be able to back out somewhere sensible, but it can tell when |
89 | * it's got itself into a real pickle and starts leaving well |
90 | * alone. |
91 | * |
92 | * Callers, please make sure that you ring alarm bells when this |
93 | * function returns @KWRITE_BROKEN@. |
94 | */ |
95 | |
96 | int key_save(key_file *f) |
97 | { |
98 | dstr n_older = DSTR_INIT, n_old = DSTR_INIT, n_new = DSTR_INIT; |
99 | int rc = KWRITE_FAIL; |
100 | |
101 | if (!(f->f & KF_MODIFIED)) |
102 | return (KWRITE_OK); |
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103 | if (!f->fp) |
104 | return (KWRITE_FAIL); |
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105 | |
106 | /* --- Write a new key file out --- * |
107 | * |
108 | * Check for an error after each key line. This ought to be enough. |
109 | * Checking after each individual byte write and @fprintf@ isn't much fun. |
110 | */ |
111 | |
112 | dstr_putf(&n_new, "%s.new", f->name); |
113 | |
114 | { |
115 | key *k; |
116 | key_iter i; |
117 | FILE *fp; |
118 | |
119 | if ((fp = fopen(n_new.buf, "w")) == 0) |
120 | goto fail_open; |
121 | |
122 | for (key_mkiter(&i, f); (k = key_next(&i)) != 0; ) { |
123 | if (key_extract(f, k, fp, 0)) { |
124 | fclose(fp); |
125 | goto fail_write; |
126 | } |
127 | } |
128 | |
129 | if (fclose(fp)) |
130 | goto fail_write; |
131 | } |
132 | |
133 | /* --- Set up the other filenames --- */ |
134 | |
135 | dstr_putf(&n_older, "%s.older", f->name); |
136 | dstr_putf(&n_old, "%s.old", f->name); |
137 | |
138 | /* --- Move the current backup on one --- * |
139 | * |
140 | * If the `older' file exists, then we're in need of attention. |
141 | */ |
142 | |
143 | { |
144 | struct stat st; |
145 | if (stat(n_older.buf, &st) == 0 || errno != ENOENT) { |
146 | errno = EEXIST; |
147 | rc = KWRITE_BROKEN; |
148 | goto fail_shift; |
149 | } |
150 | if (rename(n_old.buf, n_older.buf) && errno != ENOENT) |
151 | goto fail_shift; |
152 | } |
153 | |
154 | /* --- Copy the current file to the backup --- */ |
155 | |
156 | { |
157 | int fd; |
158 | if ((fd = open(n_old.buf, O_WRONLY | O_CREAT | O_EXCL, 0600)) < 0) |
159 | goto fail_backup; |
160 | if (fdcopy(fileno(f->fp), fd)) { |
161 | close(fd); |
162 | goto fail_backup; |
163 | } |
164 | if (close(fd)) |
165 | goto fail_backup; |
166 | } |
167 | |
168 | /* --- Copy the newly created file to the current one --- * |
169 | * |
170 | * This is the dangerous bit. |
171 | */ |
172 | |
173 | { |
174 | int fd; |
175 | if ((fd = open(n_new.buf, O_RDONLY)) < 0) |
176 | goto fail_update; |
177 | if (fdcopy(fd, fileno(f->fp))) { |
178 | close(fd); |
179 | goto fail_update; |
180 | } |
181 | close(fd); |
182 | if (fsync(fileno(f->fp))) |
183 | goto fail_update; |
184 | } |
185 | |
186 | /* --- Clean up --- * |
187 | * |
188 | * Remove the `new' file and the `older' backup. Then we're done. |
189 | */ |
190 | |
191 | unlink(n_new.buf); |
192 | unlink(n_older.buf); |
193 | return (KWRITE_OK); |
194 | |
195 | /* --- Failure while writing the new key file --- * |
196 | * |
197 | * I need to copy the backup back. If that fails then I'm really stuffed. |
198 | * If not, then I might as well try to get the backups sorted back out |
199 | * again. |
200 | */ |
201 | |
202 | fail_update: |
203 | { |
204 | int fd; |
205 | int e = errno; |
206 | |
207 | if ((fd = open(n_old.buf, O_RDONLY)) < 0) |
208 | rc = KWRITE_BROKEN; |
209 | else if (fdcopy(fd, fileno(f->fp))) { |
210 | close(fd); |
211 | rc = KWRITE_BROKEN; |
212 | } else { |
213 | close(fd); |
214 | if (fsync(fileno(f->fp))) |
215 | rc = KWRITE_BROKEN; |
216 | } |
217 | |
218 | errno = e; |
219 | if (rc == KWRITE_BROKEN) |
220 | goto fail_shift; |
221 | } |
222 | /* Now drop through */ |
223 | |
224 | /* --- Failure while writing the new backup --- * |
225 | * |
226 | * The new backup isn't any use. Try to recover the old one. |
227 | */ |
228 | |
229 | fail_backup: |
230 | { |
231 | int e = errno; |
232 | unlink(n_old.buf); |
233 | if (rename(n_older.buf, n_old.buf) && errno != ENOENT) |
234 | rc = KWRITE_BROKEN; |
235 | errno = e; |
236 | } |
237 | /* Now drop through */ |
238 | |
239 | /* --- Failure while demoting the current backup --- * |
240 | * |
241 | * Leave the completed output file there for the operator in case he wants |
242 | * to clean up. |
243 | */ |
244 | |
245 | fail_shift: |
246 | dstr_destroy(&n_new); |
247 | dstr_destroy(&n_old); |
248 | dstr_destroy(&n_older); |
249 | return (rc); |
250 | |
251 | /* --- Failure during write of new data --- * |
252 | * |
253 | * Clean up the new file and return. These errors can never cause |
254 | * breakage. |
255 | */ |
256 | |
257 | fail_write: |
258 | unlink(n_new.buf); |
259 | fail_open: |
260 | dstr_destroy(&n_new); |
261 | return (rc); |
262 | } |
263 | |
264 | /* --- @key_lockfile@ --- * |
265 | * |
266 | * Arguments: @key_file *f@ = pointer to file structure to initialize |
267 | * @const char *file@ = pointer to the file name |
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268 | * @unsigned how@ = opening options (@KOPEN_*@). |
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269 | * |
270 | * Returns: Zero if it worked, nonzero otherwise. |
271 | * |
272 | * Use: Opens a keyfile and stores the information needed for |
273 | * continued access in the structure. |
274 | * |
275 | * If the file is opened with @KOPEN_WRITE@, it's created if |
276 | * necessary with read and write permissions for owner only, and |
277 | * locked for update while it's open. |
278 | * |
279 | * This is a system-dependent routine, and only really intended |
280 | * for the private use of @key_open@. |
281 | */ |
282 | |
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283 | int key_lockfile(key_file *f, const char *file, unsigned how) |
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284 | { |
285 | int of, lf; |
286 | const char *ff; |
287 | int fd; |
288 | |
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289 | /* --- Handle the magic no-file option --- */ |
290 | |
291 | if (how & KOPEN_NOFILE) { |
292 | f->fp = 0; |
293 | return (0); |
294 | } |
295 | |
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296 | /* --- Lots of things depend on whether we're writing --- */ |
297 | |
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298 | switch (how & KOPEN_MASK) { |
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299 | case KOPEN_READ: |
300 | of = O_RDONLY; |
301 | lf = LOCK_NONEXCL; |
302 | ff = "r"; |
303 | break; |
304 | case KOPEN_WRITE: |
305 | of = O_RDWR | O_CREAT; |
306 | lf = LOCK_EXCL; |
307 | ff = "r+"; |
308 | break; |
309 | default: |
310 | errno = EINVAL; |
311 | return (-1); |
312 | } |
313 | |
314 | /* --- Open and lock the file --- */ |
315 | |
316 | if ((fd = open(file, of, 0600)) < 0) |
317 | return (-1); |
318 | if (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0 || |
319 | lock_file(fd, lf) < 0 || |
320 | (f->fp = fdopen(fd, ff)) == 0) { |
321 | close(fd); |
322 | return (-1); |
323 | } |
324 | |
325 | return (0); |
326 | } |
327 | |
328 | /*----- That's all, folks -------------------------------------------------*/ |