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1 | /* -*-c-*- |
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2 | * |
3 | * System-dependent key filing operations |
4 | * |
5 | * (c) 1999 Straylight/Edgeware |
6 | */ |
7 | |
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8 | /*----- Licensing notice --------------------------------------------------* |
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9 | * |
10 | * This file is part of Catacomb. |
11 | * |
12 | * Catacomb is free software; you can redistribute it and/or modify |
13 | * it under the terms of the GNU Library General Public License as |
14 | * published by the Free Software Foundation; either version 2 of the |
15 | * License, or (at your option) any later version. |
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16 | * |
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17 | * Catacomb is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
20 | * GNU Library General Public License for more details. |
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21 | * |
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22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with Catacomb; if not, write to the Free |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
25 | * MA 02111-1307, USA. |
26 | */ |
27 | |
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28 | /*----- Header files ------------------------------------------------------*/ |
29 | |
30 | #include <errno.h> |
31 | #include <stdio.h> |
32 | #include <stdlib.h> |
33 | #include <string.h> |
34 | |
35 | #include <sys/types.h> |
36 | #include <sys/time.h> |
37 | #include <sys/stat.h> |
38 | #include <unistd.h> |
39 | #include <fcntl.h> |
40 | |
41 | #include <mLib/dstr.h> |
42 | #include <mLib/lock.h> |
43 | |
44 | #include "key.h" |
45 | |
46 | /*----- Main code ---------------------------------------------------------*/ |
47 | |
48 | /* --- @fdcopy@ --- * |
49 | * |
50 | * Arguments: @int source@ = source file descriptor |
51 | * @int dest@ = destination file descriptor |
52 | * |
53 | * Returns: Zero if OK, nonzero otherwise. |
54 | * |
55 | * Use: Copies data from one file descriptor to another. |
56 | */ |
57 | |
58 | static int fdcopy(int source, int dest) |
59 | { |
60 | char buf[4096]; |
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61 | char *p; |
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62 | |
63 | if (lseek(source, 0, SEEK_SET) < 0|| |
64 | lseek(dest, 0, SEEK_SET) < 0 || |
65 | ftruncate(dest, 0) < 0) |
66 | return (-1); |
67 | for (;;) { |
68 | int n = read(source, buf, sizeof(buf)); |
69 | if (n < 0) |
70 | return (-1); |
71 | else if (n == 0) |
72 | break; |
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73 | p = buf; |
74 | while (n) { |
75 | int nn = write(dest, p, n); |
76 | if (nn < 0) |
77 | return (-1); |
78 | p += nn; |
79 | n -= nn; |
80 | } |
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81 | } |
82 | return (0); |
83 | } |
84 | |
85 | /* --- @key_save@ --- * |
86 | * |
87 | * Arguments: @key_file *f@ = pointer to key file block |
88 | * |
89 | * Returns: A @KWRITE_@ code indicating how well it worked. |
90 | * |
91 | * Use: Writes a key file's data back to the actual file. This code |
92 | * is extremely careful about error handling. It should usually |
93 | * be able to back out somewhere sensible, but it can tell when |
94 | * it's got itself into a real pickle and starts leaving well |
95 | * alone. |
96 | * |
97 | * Callers, please make sure that you ring alarm bells when this |
98 | * function returns @KWRITE_BROKEN@. |
99 | */ |
100 | |
101 | int key_save(key_file *f) |
102 | { |
103 | dstr n_older = DSTR_INIT, n_old = DSTR_INIT, n_new = DSTR_INIT; |
104 | int rc = KWRITE_FAIL; |
105 | |
106 | if (!(f->f & KF_MODIFIED)) |
107 | return (KWRITE_OK); |
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108 | if (!f->fp) |
109 | return (KWRITE_FAIL); |
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110 | |
111 | /* --- Write a new key file out --- * |
112 | * |
113 | * Check for an error after each key line. This ought to be enough. |
114 | * Checking after each individual byte write and @fprintf@ isn't much fun. |
115 | */ |
116 | |
117 | dstr_putf(&n_new, "%s.new", f->name); |
118 | |
119 | { |
120 | key *k; |
121 | key_iter i; |
122 | FILE *fp; |
123 | |
124 | if ((fp = fopen(n_new.buf, "w")) == 0) |
125 | goto fail_open; |
126 | |
127 | for (key_mkiter(&i, f); (k = key_next(&i)) != 0; ) { |
128 | if (key_extract(f, k, fp, 0)) { |
129 | fclose(fp); |
130 | goto fail_write; |
131 | } |
132 | } |
133 | |
134 | if (fclose(fp)) |
135 | goto fail_write; |
136 | } |
137 | |
138 | /* --- Set up the other filenames --- */ |
139 | |
140 | dstr_putf(&n_older, "%s.older", f->name); |
141 | dstr_putf(&n_old, "%s.old", f->name); |
142 | |
143 | /* --- Move the current backup on one --- * |
144 | * |
145 | * If the `older' file exists, then we're in need of attention. |
146 | */ |
147 | |
148 | { |
149 | struct stat st; |
150 | if (stat(n_older.buf, &st) == 0 || errno != ENOENT) { |
151 | errno = EEXIST; |
152 | rc = KWRITE_BROKEN; |
153 | goto fail_shift; |
154 | } |
155 | if (rename(n_old.buf, n_older.buf) && errno != ENOENT) |
156 | goto fail_shift; |
157 | } |
158 | |
159 | /* --- Copy the current file to the backup --- */ |
160 | |
161 | { |
162 | int fd; |
163 | if ((fd = open(n_old.buf, O_WRONLY | O_CREAT | O_EXCL, 0600)) < 0) |
164 | goto fail_backup; |
165 | if (fdcopy(fileno(f->fp), fd)) { |
166 | close(fd); |
167 | goto fail_backup; |
168 | } |
169 | if (close(fd)) |
170 | goto fail_backup; |
171 | } |
172 | |
173 | /* --- Copy the newly created file to the current one --- * |
174 | * |
175 | * This is the dangerous bit. |
176 | */ |
177 | |
178 | { |
179 | int fd; |
180 | if ((fd = open(n_new.buf, O_RDONLY)) < 0) |
181 | goto fail_update; |
182 | if (fdcopy(fd, fileno(f->fp))) { |
183 | close(fd); |
184 | goto fail_update; |
185 | } |
186 | close(fd); |
187 | if (fsync(fileno(f->fp))) |
188 | goto fail_update; |
189 | } |
190 | |
191 | /* --- Clean up --- * |
192 | * |
193 | * Remove the `new' file and the `older' backup. Then we're done. |
194 | */ |
195 | |
196 | unlink(n_new.buf); |
197 | unlink(n_older.buf); |
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198 | dstr_destroy(&n_new); |
199 | dstr_destroy(&n_old); |
200 | dstr_destroy(&n_older); |
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201 | return (KWRITE_OK); |
202 | |
203 | /* --- Failure while writing the new key file --- * |
204 | * |
205 | * I need to copy the backup back. If that fails then I'm really stuffed. |
206 | * If not, then I might as well try to get the backups sorted back out |
207 | * again. |
208 | */ |
209 | |
210 | fail_update: |
211 | { |
212 | int fd; |
213 | int e = errno; |
214 | |
215 | if ((fd = open(n_old.buf, O_RDONLY)) < 0) |
216 | rc = KWRITE_BROKEN; |
217 | else if (fdcopy(fd, fileno(f->fp))) { |
218 | close(fd); |
219 | rc = KWRITE_BROKEN; |
220 | } else { |
221 | close(fd); |
222 | if (fsync(fileno(f->fp))) |
223 | rc = KWRITE_BROKEN; |
224 | } |
225 | |
226 | errno = e; |
227 | if (rc == KWRITE_BROKEN) |
228 | goto fail_shift; |
229 | } |
230 | /* Now drop through */ |
231 | |
232 | /* --- Failure while writing the new backup --- * |
233 | * |
234 | * The new backup isn't any use. Try to recover the old one. |
235 | */ |
236 | |
237 | fail_backup: |
238 | { |
239 | int e = errno; |
240 | unlink(n_old.buf); |
241 | if (rename(n_older.buf, n_old.buf) && errno != ENOENT) |
242 | rc = KWRITE_BROKEN; |
243 | errno = e; |
244 | } |
245 | /* Now drop through */ |
246 | |
247 | /* --- Failure while demoting the current backup --- * |
248 | * |
249 | * Leave the completed output file there for the operator in case he wants |
250 | * to clean up. |
251 | */ |
252 | |
253 | fail_shift: |
254 | dstr_destroy(&n_new); |
255 | dstr_destroy(&n_old); |
256 | dstr_destroy(&n_older); |
257 | return (rc); |
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258 | |
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259 | /* --- Failure during write of new data --- * |
260 | * |
261 | * Clean up the new file and return. These errors can never cause |
262 | * breakage. |
263 | */ |
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264 | |
265 | fail_write: |
266 | unlink(n_new.buf); |
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267 | fail_open: |
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268 | dstr_destroy(&n_new); |
269 | return (rc); |
270 | } |
271 | |
272 | /* --- @key_lockfile@ --- * |
273 | * |
274 | * Arguments: @key_file *f@ = pointer to file structure to initialize |
275 | * @const char *file@ = pointer to the file name |
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276 | * @unsigned how@ = opening options (@KOPEN_*@). |
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277 | * |
278 | * Returns: Zero if it worked, nonzero otherwise. |
279 | * |
280 | * Use: Opens a keyfile and stores the information needed for |
281 | * continued access in the structure. |
282 | * |
283 | * If the file is opened with @KOPEN_WRITE@, it's created if |
284 | * necessary with read and write permissions for owner only, and |
285 | * locked for update while it's open. |
286 | * |
287 | * This is a system-dependent routine, and only really intended |
288 | * for the private use of @key_open@. |
289 | */ |
290 | |
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291 | int key_lockfile(key_file *f, const char *file, unsigned how) |
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292 | { |
293 | int of, lf; |
294 | const char *ff; |
295 | int fd; |
296 | |
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297 | /* --- Handle the magic no-file option --- */ |
298 | |
299 | if (how & KOPEN_NOFILE) { |
300 | f->fp = 0; |
301 | return (0); |
302 | } |
303 | |
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304 | /* --- Lots of things depend on whether we're writing --- */ |
305 | |
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306 | switch (how & KOPEN_MASK) { |
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307 | case KOPEN_READ: |
308 | of = O_RDONLY; |
309 | lf = LOCK_NONEXCL; |
310 | ff = "r"; |
311 | break; |
312 | case KOPEN_WRITE: |
313 | of = O_RDWR | O_CREAT; |
314 | lf = LOCK_EXCL; |
315 | ff = "r+"; |
316 | break; |
317 | default: |
318 | errno = EINVAL; |
319 | return (-1); |
320 | } |
321 | |
322 | /* --- Open and lock the file --- */ |
323 | |
324 | if ((fd = open(file, of, 0600)) < 0) |
325 | return (-1); |
326 | if (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0 || |
327 | lock_file(fd, lf) < 0 || |
328 | (f->fp = fdopen(fd, ff)) == 0) { |
329 | close(fd); |
330 | return (-1); |
331 | } |
332 | |
333 | return (0); |
334 | } |
335 | |
336 | /*----- That's all, folks -------------------------------------------------*/ |