c4f2d992 |
1 | /* -*-c-*- |
2 | * |
eb961767 |
3 | * $Id: become.c,v 1.21 1999/07/28 09:31:01 mdw Exp $ |
c4f2d992 |
4 | * |
5 | * Main code for `become' |
6 | * |
c758e654 |
7 | * (c) 1998 EBI |
c4f2d992 |
8 | */ |
9 | |
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10 | /*----- Licensing notice --------------------------------------------------* |
c4f2d992 |
11 | * |
12 | * This file is part of `become' |
13 | * |
14 | * `Become' is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * `Become' 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 General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
03f996bd |
25 | * along with `become'; if not, write to the Free Software Foundation, |
26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
c4f2d992 |
27 | */ |
28 | |
29 | /*----- Revision history --------------------------------------------------* |
30 | * |
31 | * $Log: become.c,v $ |
eb961767 |
32 | * Revision 1.21 1999/07/28 09:31:01 mdw |
33 | * Empty path components are equivalent to `.'. |
34 | * |
79fae27d |
35 | * Revision 1.20 1999/05/04 16:17:11 mdw |
36 | * Change to header file name for parser. See log for `parse.h' for |
37 | * details. |
38 | * |
39 | * Revision 1.19 1998/06/29 13:10:41 mdw |
59f147b0 |
40 | * Add some commentary regarding an issue in `sudo' which affects `become'; |
41 | * I'm not fixing it yet because I don't think it's important. |
42 | * |
43 | * Fixed the PATH lookup code to use the right binary name: `binary' rather |
44 | * than `todo[0]'. The two only differ when `style' is `l_login', in which |
45 | * case `binary' has an initial `/' anyway, and the PATH lookup code is |
46 | * never invoked. The name is used in a buffer-overflow precheck, though, |
47 | * and auditing is easier if the naming is consistent. |
48 | * |
7df38e1e |
49 | * Revision 1.18 1998/06/26 10:32:54 mdw |
50 | * Cosmetic change: use sizeof(destination) in memcpy. |
51 | * |
46a5b3c6 |
52 | * Revision 1.17 1998/06/18 15:06:59 mdw |
53 | * Close log before execing program to avoid leaving a socket open. |
54 | * |
f175e71b |
55 | * Revision 1.16 1998/04/23 13:21:04 mdw |
56 | * Small tweaks. Support no-network configuration option, and rearrange |
57 | * the help text a little. |
58 | * |
94455fbb |
59 | * Revision 1.15 1998/01/13 11:10:44 mdw |
60 | * Add `TZ' to the list of variables to be preserved. |
61 | * |
c758e654 |
62 | * Revision 1.14 1998/01/12 16:45:39 mdw |
63 | * Fix copyright date. |
64 | * |
9e5602f0 |
65 | * Revision 1.13 1997/09/26 09:14:57 mdw |
66 | * Merged blowfish branch into trunk. |
67 | * |
45df69ab |
68 | * Revision 1.12 1997/09/25 16:04:48 mdw |
69 | * Change directory after becoming someone else, instead of before. This |
70 | * avoids problems with root-squashed NFS mounts. |
71 | * |
9e5602f0 |
72 | * Revision 1.11.2.1 1997/09/26 09:07:58 mdw |
73 | * Use the Blowfish encryption algorithm instead of IDEA. This is partly |
74 | * because I prefer Blowfish (without any particularly strong evidence) but |
75 | * mainly because IDEA is patented and Blowfish isn't. |
76 | * |
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77 | * Revision 1.11 1997/09/24 09:48:45 mdw |
505f2736 |
78 | * Fix (scary) overrun bug in group allocation stuff. |
79 | * |
80 | * Revision 1.10 1997/09/17 10:14:10 mdw |
9df0c75d |
81 | * Fix a typo. Support service names in `--port' option. |
82 | * |
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83 | * Revision 1.9 1997/09/10 10:28:05 mdw |
84 | * Allow default port to be given as a service name or port number. Handle |
85 | * groups properly (lots of options here). |
86 | * |
87 | * Revision 1.8 1997/09/08 13:56:24 mdw |
6a4ec25c |
88 | * Change criteria for expunging items from the user's PATH: instead of |
89 | * removing things starting with `.', remove things not starting with `/'. |
90 | * |
91 | * Revision 1.7 1997/09/08 13:43:20 mdw |
c6885d5f |
92 | * Change userid when creating tracefiles rather than fiddling with |
93 | * `access': it works rather better. Also, insert some stdio buffer |
94 | * flushing to ensure tracedumps are completely written. |
95 | * |
96 | * Revision 1.6 1997/09/05 13:47:44 mdw |
d6683a48 |
97 | * Make the `-L' (trace-level) option's argument optional, like the long |
98 | * version is. |
99 | * |
100 | * Revision 1.5 1997/09/05 11:45:19 mdw |
387501ae |
101 | * Add support for different login styles, and environment variable |
102 | * manipulation in a safe and useful way. |
103 | * |
104 | * Revision 1.4 1997/08/20 16:15:13 mdw |
569b8891 |
105 | * Overhaul of environment handling. Fix daft bug in path search code. |
106 | * |
88e486d5 |
107 | * Revision 1.3 1997/08/07 16:28:59 mdw |
108 | * Do something useful when users attempt to become themselves. |
109 | * |
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110 | * Revision 1.2 1997/08/04 10:24:20 mdw |
111 | * Sources placed under CVS control. |
112 | * |
113 | * Revision 1.1 1997/07/21 13:47:54 mdw |
c4f2d992 |
114 | * Initial revision |
115 | * |
116 | */ |
117 | |
118 | /*----- Header files ------------------------------------------------------*/ |
119 | |
120 | /* --- ANSI headers --- */ |
121 | |
122 | #include <ctype.h> |
123 | #include <errno.h> |
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124 | #include <limits.h> |
c4f2d992 |
125 | #include <stdio.h> |
126 | #include <stdlib.h> |
127 | #include <string.h> |
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128 | #include <time.h> |
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129 | |
130 | /* --- Unix headers --- */ |
131 | |
132 | #include <sys/types.h> |
133 | #include <sys/stat.h> |
134 | #include <sys/socket.h> |
135 | #include <sys/utsname.h> |
136 | |
137 | #include <netinet/in.h> |
138 | |
139 | #include <arpa/inet.h> |
140 | |
141 | #include <netdb.h> |
a5089273 |
142 | #include <grp.h> |
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143 | #include <pwd.h> |
144 | #include <syslog.h> |
145 | #include <unistd.h> |
146 | |
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147 | extern char **environ; |
148 | |
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149 | /* --- Local headers --- */ |
150 | |
151 | #include "become.h" |
152 | #include "config.h" |
153 | #include "check.h" |
154 | #include "daemon.h" |
155 | #include "lexer.h" |
156 | #include "mdwopt.h" |
157 | #include "name.h" |
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158 | #include "parse.h" |
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159 | #include "rule.h" |
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160 | #include "sym.h" |
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161 | #include "utils.h" |
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162 | #include "userdb.h" |
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163 | |
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164 | /*----- Type definitions --------------------------------------------------*/ |
165 | |
166 | /* --- Symbol table entry for an environment variable --- */ |
167 | |
168 | typedef struct sym_env { |
169 | sym_base _base; /* Symbol table information */ |
170 | unsigned f; /* Flags word (see below) */ |
171 | char *val; /* Pointer to variable value */ |
172 | } sym_env; |
173 | |
174 | /* --- Environment variable flags --- */ |
175 | |
176 | enum { |
177 | envFlag_preserve = 1 |
178 | }; |
179 | |
180 | /* --- Login behaviour types --- */ |
181 | |
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182 | #define l_preserve 0 /* Preserve the environment */ |
183 | #define l_setuser 1 /* Update who I am */ |
184 | #define l_login 2 /* Do a full login */ |
387501ae |
185 | |
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186 | /* --- Group behaviour types --- * |
187 | * |
188 | * Note that these make a handy bitfield. |
189 | */ |
190 | |
191 | #ifdef HAVE_SETGROUPS |
192 | |
193 | enum { |
194 | g_unset = 0, /* Nobody's set a preference */ |
195 | g_keep = 1, /* Leave the group memberships */ |
196 | g_replace = 2, /* Replace group memberships */ |
197 | g_merge = (g_keep | g_replace) /* Merge the group memberships */ |
198 | }; |
199 | |
200 | #endif |
201 | |
387501ae |
202 | /*----- Static variables --------------------------------------------------*/ |
203 | |
204 | static sym_table bc__env; |
205 | |
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206 | /*----- Main code ---------------------------------------------------------*/ |
207 | |
208 | /* --- @bc__write@ --- * |
209 | * |
210 | * Arguments: @FILE *fp@ = pointer to a stream to write on |
211 | * @const char *p@ = pointer to a string |
212 | * |
213 | * Returns: --- |
214 | * |
215 | * Use: Writes the string to the stream, substituting the program |
216 | * name (as returned by @quis@) for each occurrence of the |
217 | * character `$'. |
218 | */ |
219 | |
220 | static void bc__write(FILE *fp, const char *p) |
221 | { |
222 | const char *n = quis(); |
223 | size_t l; |
224 | size_t nl = strlen(n); |
225 | |
226 | /* --- Try to be a little efficient --- * |
227 | * |
569b8891 |
228 | * Gather up non-`$' characters using @strcspn@ and spew them out really |
c4f2d992 |
229 | * quickly. |
230 | */ |
231 | |
232 | for (;;) { |
233 | l = strcspn(p, "$"); |
234 | if (l) |
235 | fwrite(p, l, 1, fp); |
236 | p += l; |
237 | if (!*p) |
238 | break; |
239 | fwrite(n, nl, 1, fp); |
240 | p++; |
241 | } |
242 | } |
243 | |
387501ae |
244 | /* --- @bc__setenv@ --- * |
245 | * |
246 | * Arguments: @sym_env *e@ = pointer to environment variable block |
247 | * @const char *val@ = value to set |
248 | * |
249 | * Returns: --- |
250 | * |
251 | * Use: Sets an environment variable block to the right value. |
252 | */ |
253 | |
254 | static void bc__setenv(sym_env *e, const char *val) |
255 | { |
256 | e->val = xmalloc(strlen(e->_base.name) + 1 + strlen(val) + 1); |
257 | sprintf(e->val, "%s=%s", e->_base.name, val); |
258 | } |
259 | |
260 | /* --- @bc__putenv@ --- * |
261 | * |
262 | * Arguments: @const char *var@ = name of the variable to set, or 0 if |
263 | * this is embedded in the value string |
264 | * @const char *val@ = value to set, or 0 if the variable must |
265 | * be removed |
266 | * @unsigned int fl@ = flags to set |
267 | * @unsigned int force@ = force overwrite of preserved variables |
268 | * |
269 | * Returns: Pointer to symbol block, or zero if it was deleted. |
270 | * |
271 | * Use: Puts an item into the environment. |
272 | */ |
273 | |
274 | static sym_env *bc__putenv(const char *var, const char *val, |
275 | unsigned int fl, unsigned int force) |
276 | { |
277 | unsigned int f; |
278 | sym_env *e; |
279 | char *q = 0; |
280 | size_t sz; |
281 | |
282 | /* --- Sort out embedded variable names --- */ |
283 | |
284 | if (!var) { |
285 | const char *p = strchr(val, '='); |
286 | |
287 | if (p) { |
288 | sz = p - val; |
289 | q = xmalloc(sz + 1); |
290 | memcpy(q, val, sz); |
291 | q[sz] = 0; |
292 | var = q; |
293 | val = p + 1; |
294 | } else { |
295 | var = val; |
296 | val = 0; |
297 | } |
298 | } |
299 | |
300 | /* --- Find the variable block --- */ |
301 | |
302 | if (val) { |
303 | e = sym_find(&bc__env, var, -1, sizeof(*e), &f); |
a5089273 |
304 | if (!f || ~e->f & envFlag_preserve || force) { |
387501ae |
305 | if (f) |
306 | free(e->val); |
307 | bc__setenv(e, val); |
308 | } |
309 | } else { |
310 | e = sym_find(&bc__env, var, -1, 0, 0); |
311 | if (e && (force || ~e->f & envFlag_preserve)) |
312 | sym_remove(&bc__env, e); |
313 | e = 0; |
314 | } |
315 | |
316 | /* --- Tidy up and return --- */ |
317 | |
318 | if (q) |
319 | free(q); |
320 | if (e) |
321 | e->f = fl; |
322 | return (e); |
323 | } |
324 | |
a5089273 |
325 | /* --- @bc__addGroups@ --- * |
326 | * |
327 | * Arguments: @gid_t *g@ = pointer to a group array |
328 | * @int *png@ = pointer to number of entries in the array |
329 | * @const gid_t *a@ = pointer to groups to add |
330 | * @int na@ = number of groups to add |
331 | * |
332 | * Returns: Zero if it was OK, nonzero if we should stop now. |
333 | * |
334 | * Use: Adds groups to a groups array. |
335 | */ |
336 | |
337 | static int bc__addGroups(gid_t *g, int *png, const gid_t *a, int na) |
338 | { |
339 | int i, j; |
340 | int ng = *png; |
341 | |
342 | for (i = 0; i < na; i++) { |
343 | |
344 | /* --- Ensure this group isn't already in the list --- */ |
345 | |
346 | for (j = 0; j < ng; j++) { |
347 | if (a[i] == g[j]) |
348 | goto next_group; |
349 | } |
350 | |
351 | /* --- See if there's room for more --- */ |
352 | |
505f2736 |
353 | if (ng >= NGROUPS_MAX) { |
354 | moan("too many groups (system limit exceeded) -- some have been lost"); |
a5089273 |
355 | *png = ng; |
356 | return (-1); |
357 | } |
358 | |
359 | /* --- Add the group --- */ |
360 | |
361 | g[ng++] = a[i]; |
362 | next_group:; |
363 | } |
364 | |
365 | *png = ng; |
366 | return (0); |
367 | } |
368 | |
c4f2d992 |
369 | /* --- @bc__banner@ --- * |
370 | * |
371 | * Arguments: @FILE *fp@ = stream to write on |
372 | * |
373 | * Returns: --- |
374 | * |
375 | * Use: Writes a banner containing copyright information. |
376 | */ |
377 | |
378 | static void bc__banner(FILE *fp) |
379 | { |
380 | bc__write(fp, "$ version " VERSION "\n"); |
381 | } |
382 | |
383 | /* --- @bc__usage@ --- * |
384 | * |
385 | * Arguments: @FILE *fp@ = stream to write on |
386 | * |
387 | * Returns: --- |
388 | * |
389 | * Use: Writes a terse reminder of command line syntax. |
390 | */ |
391 | |
392 | static void bc__usage(FILE *fp) |
393 | { |
394 | bc__write(fp, |
395 | "Usage: \n" |
396 | " $ -c <shell-command> <user>\n" |
387501ae |
397 | " $ [<env-var>] <user> [<command> [<arguments>]...]\n" |
f175e71b |
398 | #ifndef NONETWORK |
399 | " $ -d [-p <port>] [-f <config-file>]\n" |
400 | #endif |
401 | ); |
c4f2d992 |
402 | } |
403 | |
404 | /* --- @bc__help@ --- * |
405 | * |
406 | * Arguments: @FILE *fp@ = stream to write on |
569b8891 |
407 | * @int suid@ = whether we're running set-uid |
c4f2d992 |
408 | * |
409 | * Returns: --- |
410 | * |
411 | * Use: Displays a help message for this excellent piece of software. |
412 | */ |
413 | |
569b8891 |
414 | static void bc__help(FILE *fp, int suid) |
c4f2d992 |
415 | { |
416 | bc__banner(fp); |
417 | putc('\n', fp); |
418 | bc__usage(fp); |
419 | putc('\n', fp); |
420 | bc__write(fp, |
421 | "The `$' program allows you to run a process as another user.\n" |
422 | "If a command name is given, this is the process executed. If the `-c'\n" |
423 | "option is used, the process is assumed to be `/bin/sh'. If no command is\n" |
424 | "given, your default login shell is used.\n" |
425 | "\n" |
426 | "Your user id, the user id you wish to become, the name of the process\n" |
427 | "you wish to run, and the identity of the current host are looked up to\n" |
428 | "ensure that you have permission to do this.\n" |
429 | "\n" |
430 | "Note that logs are kept of all uses of this program.\n" |
431 | "\n" |
432 | "Options available are:\n" |
433 | "\n" |
387501ae |
434 | "-h, --help Display this help text\n" |
435 | "-u, --usage Display a short usage summary\n" |
436 | "-v, --version Display $'s version number\n" |
437 | "\n" |
438 | "-e, --preserve-environment Try to preserve the current environment\n" |
439 | "-s, --su, --set-user Set environment variables to reflect USER\n" |
440 | "-l, --login Really log in as USER\n" |
f175e71b |
441 | " [Default is " |
442 | #if DEFAULT_LOGIN_STYLE == l_preserve |
443 | "preserve-environment" |
444 | #elif DEFAULT_LOGIN_STYLE == l_setuser |
445 | "set-user" |
446 | #elif DEFAULT_LOGIN_STYLE == l_login |
447 | "login" |
448 | #else |
449 | "poorly configured" |
450 | #endif |
451 | "]\n\n" |
a5089273 |
452 | "-g GROUP, --group=GROUP Set primary group-id to be GROUP\n" |
453 | #ifdef HAVE_SETGROUPS |
454 | "-k, --keep-groups Keep your current set of groups\n" |
455 | "-m, --merge-groups Merge the lists of groups\n" |
456 | "-r, --replace-groups Replace the list of groups\n" |
457 | #endif |
458 | "\n" |
387501ae |
459 | "-c CMD, --command=CMD Run the (Bourne) shell command CMD\n" |
f175e71b |
460 | #ifndef NONETWORK |
387501ae |
461 | "\n" |
462 | "-d, --daemon Start a daemon\n" |
463 | "-p PORT, --port=PORT In daemon mode, listen on PORT\n" |
f175e71b |
464 | "-f FILE, --config-file=FILE In daemon mode, read config from FILE\n" |
465 | #endif |
466 | ); |
03f996bd |
467 | #ifdef TRACING |
387501ae |
468 | bc__write(fp, "\n"); |
569b8891 |
469 | if (!suid) { |
470 | bc__write(fp, |
387501ae |
471 | "-I USER, --impersonate=USER Claim to be USER when asking the server\n"); |
569b8891 |
472 | } |
473 | bc__write(fp, |
387501ae |
474 | "-T FILE, --trace=FILE Dump trace information to FILE (boring)\n" |
475 | "-L OPTS, --trace-level=OPTS Set level of tracing information\n"); |
03f996bd |
476 | #endif |
c4f2d992 |
477 | } |
478 | |
479 | /* --- @main@ --- * |
480 | * |
481 | * Arguments: @int argc@ = number of command line arguments |
482 | * @char *argv[]@ = pointer to the various arguments |
483 | * |
484 | * Returns: Zero if successful. |
485 | * |
486 | * Use: Allows a user to change UID. |
487 | */ |
488 | |
489 | int main(int argc, char *argv[]) |
490 | { |
03f996bd |
491 | /* --- Request block setup parameters --- */ |
c4f2d992 |
492 | |
03f996bd |
493 | request rq; /* Request buffer to build */ |
494 | char *cmd = 0; /* Shell command to execute */ |
495 | char *binary = "/bin/sh"; /* Default binary to execute */ |
496 | char **env = environ; /* Default environment to pass */ |
387501ae |
497 | char **todo = 0; /* Pointer to argument list */ |
498 | char *who = 0; /* Who we're meant to become */ |
03f996bd |
499 | struct passwd *from_pw = 0; /* User we are right now */ |
500 | struct passwd *to_pw = 0; /* User we want to become */ |
501 | |
502 | /* --- Become server setup parameters --- */ |
503 | |
f175e71b |
504 | #ifndef NONETWORK |
03f996bd |
505 | char *conffile = file_RULES; /* Default config file for daemon */ |
9df0c75d |
506 | int port = 0; /* Default port for daemon */ |
f175e71b |
507 | #endif |
03f996bd |
508 | |
509 | /* --- Miscellanous shared variables --- */ |
510 | |
511 | unsigned flags = 0; /* Various useful flags */ |
387501ae |
512 | int style = DEFAULT_LOGIN_STYLE; /* Login style */ |
a5089273 |
513 | gid_t group = -1; /* Default group to set */ |
514 | int gstyle = g_unset; /* No group style set yet */ |
515 | |
516 | #ifdef HAVE_SETGROUPS |
517 | gid_t groups[NGROUPS_MAX]; /* Set of groups */ |
518 | int ngroups; /* Number of groups in the set */ |
519 | #endif |
03f996bd |
520 | |
521 | /* --- Default argument list executes a shell command --- */ |
522 | |
523 | static char *shell[] = { |
524 | "/bin/sh", /* Bourne shell */ |
525 | "-c", /* Read from command line */ |
526 | 0, /* Pointer to shell command */ |
527 | 0 /* Terminator */ |
c4f2d992 |
528 | }; |
529 | |
03f996bd |
530 | /* --- Definitions for the various flags --- */ |
531 | |
532 | enum { |
533 | f_daemon = 1, /* Start up in daemon mode */ |
534 | f_duff = 2, /* Fault in arguments */ |
45df69ab |
535 | f_shell = 4, /* Run a default shell */ |
03f996bd |
536 | f_dummy = 8, /* Don't actually do anything */ |
a5089273 |
537 | f_setuid = 16, /* We're running setuid */ |
538 | f_havegroup = 32 /* Set a default group */ |
03f996bd |
539 | }; |
c4f2d992 |
540 | |
541 | /* --- Set up the program name --- */ |
542 | |
543 | ego(argv[0]); |
03f996bd |
544 | clock(); |
545 | if (getuid() != geteuid()) |
546 | flags |= f_setuid; |
c4f2d992 |
547 | |
387501ae |
548 | /* --- Read the environment into a hashtable --- */ |
549 | |
550 | { |
551 | char **p; |
552 | |
553 | sym_createTable(&bc__env); |
554 | for (p = environ; *p; p++) |
555 | bc__putenv(0, *p, 0, 0); |
556 | } |
557 | |
c4f2d992 |
558 | /* --- Parse some command line arguments --- */ |
559 | |
560 | for (;;) { |
561 | int i; |
03f996bd |
562 | static struct option opts[] = { |
387501ae |
563 | |
564 | /* --- Asking for help --- */ |
565 | |
c4f2d992 |
566 | { "help", 0, 0, 'h' }, |
387501ae |
567 | { "usage", 0, 0, 'u' }, |
c4f2d992 |
568 | { "version", 0, 0, 'v' }, |
387501ae |
569 | |
570 | /* --- Login style options --- */ |
571 | |
572 | { "preserve-environment", 0, 0, 'e' }, |
573 | { "su", 0, 0, 's' }, |
574 | { "set-user", 0, 0, 's' }, |
03f996bd |
575 | { "login", 0, 0, 'l' }, |
387501ae |
576 | |
a5089273 |
577 | /* --- Group style options --- */ |
578 | |
579 | { "group", gFlag_argReq, 0, 'g' }, |
580 | #ifdef HAVE_SETGROUPS |
581 | { "keep-groups", 0, 0, 'k' }, |
582 | { "merge-groups", 0, 0, 'm' }, |
583 | { "replace-groups", 0, 0, 'r' }, |
584 | #endif |
585 | |
387501ae |
586 | /* --- Command to run options --- */ |
587 | |
c4f2d992 |
588 | { "command", gFlag_argReq, 0, 'c' }, |
387501ae |
589 | |
590 | /* --- Server options --- */ |
591 | |
f175e71b |
592 | #ifndef NONETWORK |
c4f2d992 |
593 | { "daemon", 0, 0, 'd' }, |
594 | { "port", gFlag_argReq, 0, 'p' }, |
595 | { "config-file", gFlag_argReq, 0, 'f' }, |
f175e71b |
596 | #endif |
387501ae |
597 | |
598 | /* --- Tracing options --- */ |
599 | |
03f996bd |
600 | #ifdef TRACING |
601 | { "impersonate", gFlag_argReq, 0, 'I' }, |
602 | { "trace", gFlag_argOpt, 0, 'T' }, |
603 | { "trace-level", gFlag_argOpt, 0, 'L' }, |
604 | #endif |
387501ae |
605 | |
c4f2d992 |
606 | { 0, 0, 0, 0 } |
607 | }; |
608 | |
387501ae |
609 | i = mdwopt(argc, argv, |
a5089273 |
610 | "-" /* Return non-options as options */ |
611 | "huv" /* Asking for help */ |
612 | "esl" /* Login style options */ |
613 | #ifdef HAVE_SETGROUPS |
614 | "g:kmr" /* Group style options */ |
615 | #else |
616 | "g:" /* Group (without @setgroups@) */ |
617 | #endif |
618 | "c:" /* Command to run options */ |
f175e71b |
619 | #ifndef NONETWORK |
a5089273 |
620 | "dp:f:" /* Server options */ |
f175e71b |
621 | #endif |
a5089273 |
622 | #ifdef TRACING |
623 | "I:T::L::" /* Tracing options */ |
624 | #endif |
625 | , |
387501ae |
626 | opts, 0, 0, gFlag_envVar); |
c4f2d992 |
627 | if (i < 0) |
387501ae |
628 | goto done_options; |
c4f2d992 |
629 | |
630 | switch (i) { |
03f996bd |
631 | |
387501ae |
632 | /* --- Asking for help --- */ |
03f996bd |
633 | |
c4f2d992 |
634 | case 'h': |
569b8891 |
635 | bc__help(stdout, flags & f_setuid); |
636 | exit(0); |
637 | break; |
387501ae |
638 | case 'u': |
569b8891 |
639 | bc__usage(stdout); |
c4f2d992 |
640 | exit(0); |
641 | break; |
642 | case 'v': |
643 | bc__banner(stdout); |
644 | exit(0); |
645 | break; |
03f996bd |
646 | |
387501ae |
647 | /* --- Login style options --- */ |
03f996bd |
648 | |
387501ae |
649 | case 'e': |
650 | style = l_preserve; |
651 | break; |
652 | case 's': |
a5089273 |
653 | style = l_setuser; |
387501ae |
654 | break; |
03f996bd |
655 | case 'l': |
387501ae |
656 | style = l_login; |
03f996bd |
657 | break; |
387501ae |
658 | |
a5089273 |
659 | /* --- Group style options --- */ |
660 | |
661 | case 'g': |
662 | if (isdigit((unsigned char)optarg[0])) |
663 | group = atoi(optarg); |
664 | else { |
665 | struct group *gr = getgrnam(optarg); |
666 | if (!gr) |
667 | die("unknown group `%s'", optarg); |
668 | group = gr->gr_gid; |
669 | } |
670 | flags |= f_havegroup; |
671 | break; |
672 | |
673 | case 'k': |
674 | gstyle = g_keep; |
675 | break; |
676 | case 'm': |
677 | gstyle = g_merge; |
678 | break; |
679 | case 'r': |
680 | gstyle = g_replace; |
681 | break; |
682 | |
387501ae |
683 | /* --- Command to run options --- */ |
684 | |
c4f2d992 |
685 | case 'c': |
686 | cmd = optarg; |
687 | break; |
387501ae |
688 | |
689 | /* --- Server options --- */ |
690 | |
f175e71b |
691 | #ifndef NONETWORK |
c4f2d992 |
692 | case 'p': |
a5089273 |
693 | if (isdigit((unsigned char)optarg[0])) |
694 | port = htons(atoi(optarg)); |
695 | else { |
696 | struct servent *s = getservbyname(optarg, "udp"); |
697 | if (!s) |
698 | die("unknown service name `%s'", optarg); |
699 | port = s->s_port; |
700 | } |
c4f2d992 |
701 | break; |
702 | case 'd': |
703 | flags |= f_daemon; |
704 | break; |
705 | case 'f': |
706 | conffile = optarg; |
707 | break; |
f175e71b |
708 | #endif |
03f996bd |
709 | |
710 | /* --- Pretend to be a different user --- * |
711 | * |
712 | * There are all sorts of nasty implications for this option. Don't |
713 | * allow it if we're running setuid. Disable the actual login anyway. |
714 | */ |
715 | |
716 | #ifdef TRACING |
569b8891 |
717 | |
03f996bd |
718 | case 'I': |
719 | if (flags & f_setuid) |
720 | moan("shan't allow impersonation while running setuid"); |
721 | else { |
722 | struct passwd *pw; |
723 | if (isdigit((unsigned char)optarg[0])) |
724 | pw = getpwuid(atoi(optarg)); |
725 | else |
726 | pw = getpwnam(optarg); |
727 | if (!pw) |
728 | die("can't impersonate unknown user `%s'", optarg); |
729 | from_pw = userdb_copyUser(pw); |
730 | rq.from = from_pw->pw_uid; |
731 | flags |= f_dummy; |
732 | } |
c4f2d992 |
733 | break; |
569b8891 |
734 | |
03f996bd |
735 | #endif |
736 | |
737 | /* --- Tracing support --- * |
738 | * |
739 | * Be careful not to zap a file I wouldn't normally be allowed to write |
740 | * to! |
741 | */ |
742 | |
743 | #ifdef TRACING |
744 | |
745 | case 'T': { |
746 | FILE *fp; |
747 | |
748 | if (optarg == 0 || strcmp(optarg, "-") == 0) |
749 | fp = stdout; |
750 | else { |
c6885d5f |
751 | uid_t eu = geteuid(), ru = getuid(); |
752 | |
753 | #ifdef HAVE_SETREUID |
754 | if (setreuid(eu, ru)) |
755 | #else |
756 | if (seteuid(ru)) |
757 | #endif |
758 | { |
759 | die("couldn't temporarily give up privileges: %s", |
760 | strerror(errno)); |
03f996bd |
761 | } |
c6885d5f |
762 | |
03f996bd |
763 | if ((fp = fopen(optarg, "w")) == 0) { |
764 | die("couldn't open trace file `%s' for writing: %s", |
765 | optarg, strerror(errno)); |
766 | } |
c6885d5f |
767 | |
768 | #ifdef HAVE_SETREUID |
769 | if (setreuid(ru, eu)) |
770 | #else |
771 | if (seteuid(eu)) |
772 | #endif |
773 | die("couldn't regain privileges: %s", strerror(errno)); |
03f996bd |
774 | } |
775 | traceon(fp, TRACE_DFL); |
776 | trace(TRACE_MISC, "become: tracing enabled"); |
777 | } break; |
778 | |
779 | #endif |
780 | |
781 | /* --- Setting trace levels --- */ |
782 | |
783 | #ifdef TRACING |
784 | |
785 | case 'L': { |
786 | int sense = 1; |
787 | unsigned int lvl = 0, l; |
788 | const char *p = optarg; |
789 | |
790 | /* --- Table of tracing facilities --- */ |
791 | |
792 | typedef struct tr { |
793 | char ch; |
794 | unsigned int l; |
795 | const char *help; |
796 | } tr; |
797 | |
798 | static tr lvltbl[] = { |
799 | { 'm', TRACE_MISC, "miscellaneous messages" }, |
800 | { 's', TRACE_SETUP, "building the request block" }, |
03f996bd |
801 | { 'r', TRACE_RULE, "ruleset scanning" }, |
802 | { 'c', TRACE_CHECK, "request checking" }, |
f175e71b |
803 | #ifndef NONETWORK |
804 | { 'd', TRACE_DAEMON, "server process" }, |
03f996bd |
805 | { 'l', TRACE_CLIENT, "client process" }, |
806 | { 'R', TRACE_RAND, "random number generator" }, |
807 | { 'C', TRACE_CRYPTO, "cryptographic processing of requests" }, |
f175e71b |
808 | #endif |
03f996bd |
809 | { 'y', TRACE_YACC, "parsing configuration file" }, |
810 | { 'D', TRACE_DFL, "default tracing options" }, |
811 | { 'A', TRACE_ALL, "all tracing options" }, |
812 | { 0, 0, 0 } |
813 | }; |
814 | tr *tp; |
815 | |
816 | /* --- Output some help if there's no arguemnt --- */ |
817 | |
818 | if (!optarg) { |
819 | bc__banner(stdout); |
820 | bc__write(stdout, |
821 | "\n" |
822 | "Tracing options:\n" |
823 | "\n"); |
824 | for (tp = lvltbl; tp->l; tp++) { |
825 | if ((flags & f_setuid) == 0 || tp->l & ~TRACE_PRIV) |
826 | printf("%c -- %s\n", tp->ch, tp->help); |
827 | } |
828 | bc__write(stdout, |
829 | "\n" |
9df0c75d |
830 | "Also, `+' and `-' options are recognised to turn on and off various\n" |
03f996bd |
831 | "tracing options. For example, `A-r' enables everything except ruleset\n" |
832 | "tracing, and `A-D+c' is everything except the defaults, but with request\n" |
833 | "check tracing.\n" |
834 | ); |
835 | exit(0); |
836 | } |
837 | |
838 | while (*p) { |
839 | if (*p == '+') |
840 | sense = 1; |
841 | else if (*p == '-') |
842 | sense = 0; |
843 | else { |
844 | for (tp = lvltbl; tp->l && *p != tp->ch; tp++) |
845 | ; |
846 | l = tp->l; |
847 | if (flags & f_setuid) |
848 | l &= ~TRACE_PRIV; |
849 | if (l) |
850 | lvl = sense ? (lvl | l) : (lvl & ~l); |
851 | else |
852 | moan("unknown trace option `%c'", *p); |
853 | } |
854 | p++; |
855 | } |
856 | |
857 | tracesetlvl(lvl); |
858 | yydebug = ((lvl & TRACE_YACC) != 0); |
859 | } break; |
860 | |
861 | #endif |
862 | |
387501ae |
863 | /* --- Something that wasn't an option --- * |
864 | * |
865 | * The following nasties are supported: |
866 | * |
867 | * * NAME=VALUE -- preserve NAME, and give it a VALUE |
868 | * * NAME= -- preserve NAME, and give it an empty value |
869 | * * NAME- -- delete NAME |
870 | * * NAME! -- preserve NAME with existing value |
871 | * |
872 | * Anything else is either the user name (which is OK) or the start of |
873 | * the command (in which case I stop and read the rest of the command). |
874 | */ |
875 | |
876 | case 0: { |
877 | size_t sz = strcspn(optarg, "=-!"); |
878 | sym_env *e; |
879 | |
880 | /* --- None of the above --- */ |
881 | |
882 | if (optarg[sz] == 0 || (optarg[sz] != '=' && optarg[sz + 1] != 0)) { |
9df0c75d |
883 | if (!who) { |
387501ae |
884 | who = optarg; |
9df0c75d |
885 | break; |
886 | } else { |
387501ae |
887 | optind--; |
888 | goto done_options; |
889 | } |
890 | } |
891 | |
892 | /* --- Do the appropriate thing --- */ |
893 | |
894 | switch (optarg[sz]) { |
895 | case '=': |
896 | bc__putenv(0, optarg, envFlag_preserve, 1); |
897 | break; |
898 | case '-': |
899 | optarg[sz] = 0; |
900 | bc__putenv(optarg, 0, 0, 1); |
901 | break; |
902 | case '!': |
903 | optarg[sz] = 0; |
904 | if ((e = sym_find(&bc__env, optarg, -1, 0, 0)) != 0) |
905 | e->f |= envFlag_preserve; |
906 | break; |
907 | } |
908 | } break; |
909 | |
03f996bd |
910 | /* --- Something I didn't understand has occurred --- */ |
911 | |
c4f2d992 |
912 | case '?': |
913 | flags |= f_duff; |
914 | break; |
915 | } |
916 | } |
387501ae |
917 | |
918 | done_options: |
c4f2d992 |
919 | if (flags & f_duff) { |
920 | bc__usage(stderr); |
921 | exit(1); |
922 | } |
923 | |
924 | /* --- Switch to daemon mode if requested --- */ |
925 | |
f175e71b |
926 | #ifndef NONETWORK |
c4f2d992 |
927 | if (flags & f_daemon) { |
03f996bd |
928 | T( trace(TRACE_MISC, "become: daemon mode requested"); ) |
c4f2d992 |
929 | daemon_init(conffile, port); |
930 | exit(0); |
931 | } |
f175e71b |
932 | #endif |
c4f2d992 |
933 | |
934 | /* --- Open a syslog --- */ |
935 | |
936 | openlog(quis(), 0, LOG_AUTH); |
937 | |
938 | /* --- Pick out the uid --- */ |
939 | |
940 | { |
c4f2d992 |
941 | struct passwd *pw; |
03f996bd |
942 | |
387501ae |
943 | if (!who) { |
c4f2d992 |
944 | bc__usage(stderr); |
945 | exit(1); |
946 | } |
03f996bd |
947 | |
387501ae |
948 | if (isdigit((unsigned char)who[0])) |
949 | pw = getpwuid(atoi(who)); |
03f996bd |
950 | else |
387501ae |
951 | pw = getpwnam(who); |
c4f2d992 |
952 | if (!pw) |
387501ae |
953 | die("unknown user `%s'", who); |
03f996bd |
954 | to_pw = userdb_copyUser(pw); |
c4f2d992 |
955 | rq.to = pw->pw_uid; |
956 | } |
957 | |
958 | /* --- Fill in the easy bits of the request --- */ |
959 | |
03f996bd |
960 | if (!from_pw) { |
961 | struct passwd *pw; |
962 | |
963 | rq.from = getuid(); |
964 | pw = getpwuid(rq.from); |
965 | if (!pw) |
966 | die("who are you? (can't find user %li)", (long)rq.from); |
967 | from_pw = userdb_copyUser(pw); |
968 | } |
c4f2d992 |
969 | |
970 | /* --- Find the local host address --- */ |
971 | |
972 | { |
973 | struct utsname u; |
974 | struct hostent *he; |
975 | uname(&u); |
976 | if ((he = gethostbyname(u.nodename)) == 0) |
977 | die("who am I? (can't resolve `%s')", u.nodename); |
7df38e1e |
978 | memcpy(&rq.host, he->h_addr, sizeof(rq.host)); |
c4f2d992 |
979 | } |
980 | |
a5089273 |
981 | /* --- Fiddle with group ownerships a bit --- */ |
982 | |
983 | { |
984 | #ifdef HAVE_SETGROUPS |
985 | gid_t from_gr[NGROUPS_MAX], to_gr[NGROUPS_MAX]; |
986 | int n_fgr, n_tgr; |
987 | #endif |
988 | |
989 | /* --- Set the default login group, if there is one --- */ |
990 | |
991 | if (~flags & f_havegroup) |
992 | group = (style == l_preserve) ? from_pw->pw_gid : to_pw->pw_gid; |
993 | |
994 | #ifndef HAVE_SETGROUPS |
995 | |
996 | /* --- Check that it's valid --- */ |
997 | |
998 | if (group != from_pw->pw_gid && group != to_pw->pw_gid) |
999 | die("invalid default group"); |
1000 | |
1001 | #else |
1002 | |
1003 | /* --- Set the default group style --- */ |
1004 | |
1005 | if (gstyle == g_unset) |
1006 | gstyle = (style == l_login) ? g_replace : g_merge; |
1007 | |
1008 | /* --- Read in my current set of groups --- */ |
1009 | |
1010 | n_fgr = getgroups(NGROUPS_MAX, from_gr); |
1011 | |
1012 | /* --- Now read the groups for the target user --- * |
1013 | * |
1014 | * Do this even if I'm using the @g_keep@ style -- I'll use it for |
1015 | * checking that @group@ is valid. |
1016 | */ |
1017 | |
1018 | { |
1019 | struct group *gr; |
1020 | char **p; |
1021 | |
1022 | n_tgr = 0; |
1023 | to_gr[n_tgr++] = to_pw->pw_gid; |
1024 | |
1025 | setgrent(); |
1026 | while ((gr = getgrent()) != 0) { |
1027 | if (gr->gr_gid == to_gr[0]) |
1028 | continue; |
1029 | for (p = gr->gr_mem; *p; p++) { |
1030 | if (strcmp(to_pw->pw_name, *p) == 0) { |
1031 | to_gr[n_tgr++] = gr->gr_gid; |
1032 | if (n_tgr >= NGROUPS_MAX) |
1033 | goto done_groups; |
1034 | break; |
1035 | } |
1036 | } |
1037 | } |
1038 | |
1039 | done_groups: |
1040 | endgrent(); |
1041 | } |
1042 | |
1043 | /* --- Check that @group@ is reasonable --- */ |
1044 | |
1045 | { |
1046 | int i; |
1047 | |
1048 | if (group == getgid() || group == from_pw->pw_gid) |
1049 | goto group_ok; |
1050 | for (i = 0; i < n_fgr; i++) { |
1051 | if (group == from_gr[i]) |
1052 | goto group_ok; |
1053 | } |
1054 | for (i = 0; i < n_tgr; i++) { |
1055 | if (group == to_gr[i]) |
1056 | goto group_ok; |
1057 | } |
1058 | die("invalid default group"); |
1059 | group_ok:; |
1060 | } |
1061 | |
1062 | /* --- Phew. Now comes the hard bit --- */ |
1063 | |
1064 | { |
1065 | gid_t ga[4]; |
1066 | int i; |
1067 | |
1068 | i = 0; |
1069 | ga[i++] = group; |
1070 | if (gstyle & g_keep) { |
1071 | ga[i++] = getgid(); |
1072 | ga[i++] = from_pw->pw_gid; |
1073 | } |
1074 | if (gstyle & g_replace) |
1075 | ga[i++] = to_pw->pw_gid; |
1076 | |
1077 | /* --- Style authorities will become apoplectic if shown this --- * |
1078 | * |
1079 | * As far as I can see, it's the neatest way of writing it. |
1080 | */ |
1081 | |
1082 | ngroups = 0; |
1083 | (void)(bc__addGroups(groups, &ngroups, ga, i) || |
1084 | ((gstyle & g_keep) && |
f175e71b |
1085 | bc__addGroups(groups, &ngroups, from_gr, n_fgr)) || |
a5089273 |
1086 | ((gstyle & g_replace) && |
1087 | bc__addGroups(groups, &ngroups, to_gr, n_tgr))); |
1088 | } |
1089 | |
1090 | #endif |
1091 | |
1092 | /* --- Trace the results of all this --- */ |
1093 | |
1094 | T( trace(TRACE_SETUP, "setup: default group == %i", (int)group); ) |
1095 | |
1096 | #ifdef HAVE_SETGROUPS |
1097 | IF_TRACING(TRACE_SETUP, { |
1098 | int i; |
1099 | |
1100 | for (i = 1; i < ngroups; i++) |
1101 | trace(TRACE_SETUP, "setup: subsidiary group %i", (int)groups[i]); |
1102 | }) |
1103 | #endif |
1104 | } |
1105 | |
03f996bd |
1106 | /* --- Shell commands are easy --- */ |
c4f2d992 |
1107 | |
1108 | if (cmd) { |
1109 | shell[2] = cmd; |
1110 | todo = shell; |
03f996bd |
1111 | } |
1112 | |
1113 | /* --- A command given on the command line isn't too hard --- */ |
1114 | |
1115 | else if (optind < argc) { |
c4f2d992 |
1116 | todo = argv + optind; |
03f996bd |
1117 | binary = todo[0]; |
1118 | } |
1119 | |
45df69ab |
1120 | else { |
1121 | flags |= f_shell; |
03f996bd |
1122 | |
45df69ab |
1123 | switch (style) { |
c4f2d992 |
1124 | |
45df69ab |
1125 | /* --- An unadorned becoming requires little work --- */ |
03f996bd |
1126 | |
45df69ab |
1127 | case l_preserve: |
1128 | shell[0] = getenv("SHELL"); |
1129 | if (!shell[0]) |
1130 | shell[0] = from_pw->pw_shell; |
1131 | shell[1] = 0; |
1132 | todo = shell; |
1133 | binary = todo[0]; |
1134 | break; |
387501ae |
1135 | |
45df69ab |
1136 | /* --- An su-like login needs slightly less effort --- */ |
1137 | |
1138 | case l_setuser: |
1139 | shell[0] = to_pw->pw_shell; |
1140 | shell[1] = 0; |
1141 | todo = shell; |
1142 | binary = todo[0]; |
1143 | break; |
1144 | |
1145 | /* --- A login request needs a little bit of work --- */ |
387501ae |
1146 | |
45df69ab |
1147 | case l_login: { |
1148 | const char *p = strrchr(to_pw->pw_shell, '/'); |
1149 | |
1150 | if (p) |
1151 | p++; |
1152 | else |
1153 | p = to_pw->pw_shell; |
1154 | shell[0] = xmalloc(strlen(p) + 2); |
1155 | shell[0][0] = '-'; |
1156 | strcpy(shell[0] + 1, p); |
1157 | shell[1] = 0; |
1158 | todo = shell; |
1159 | binary = to_pw->pw_shell; |
1160 | } break; |
1161 | } |
03f996bd |
1162 | } |
1163 | |
569b8891 |
1164 | /* --- Mangle the environment --- * |
1165 | * |
387501ae |
1166 | * This keeps getting more complicated all the time. (How true. Now I've |
1167 | * got all sorts of nasty environment mangling to do.) |
1168 | * |
1169 | * The environment stuff now happens in seven phases: |
1170 | * |
1171 | * 1. Mark very special variables to be preserved. Currently only TERM |
1172 | * and DISPLAY are treated in this way. |
1173 | * |
1174 | * 2. Set and preserve Become's own environment variables. |
1175 | * |
1176 | * 3. Set and preserve the user identity variables (USER, LOGNAME, HOME, |
1177 | * SHELL and MAIL) if we're being `su'-like or `login'-like. |
1178 | * |
1179 | * 4. If we're preserving the environment or being `su'-like, process the |
1180 | * PATH variable a little. Otherwise reset it to something |
1181 | * appropriate. |
1182 | * |
1183 | * 5. If we're being `login'-like, expunge all unpreserved variables. |
1184 | * |
1185 | * 6. Expunge any security-critical variables. |
1186 | * |
1187 | * 7. Build a new environment table to pass to child processes. |
569b8891 |
1188 | */ |
1189 | |
1190 | { |
387501ae |
1191 | /* --- Variables to be preserved always --- * |
1192 | * |
1193 | * A user can explicitly expunge a variable in this list, in which case |
1194 | * we never get to see it here. |
1195 | */ |
569b8891 |
1196 | |
387501ae |
1197 | static char *preserve[] = { |
94455fbb |
1198 | "TERM", "DISPLAY", "TZ", 0 |
387501ae |
1199 | }; |
c6885d5f |
1200 | |
387501ae |
1201 | /* --- Variables to be expunged --- * |
569b8891 |
1202 | * |
c6885d5f |
1203 | * Any environment string which has one of the following as a prefix will |
1204 | * be expunged from the environment passed to the called process. The |
1205 | * first line lists variables which have been used to list search paths |
1206 | * for shared libraries: by manipulating these, an attacker could replace |
1207 | * a standard library with one of his own. The second line lists other |
1208 | * well-known dangerous environment variables. |
569b8891 |
1209 | */ |
1210 | |
387501ae |
1211 | static char *banned[] = { |
1212 | "-LD_", "SHLIB_PATH", "LIBPATH", "-_RLD_", |
1213 | "IFS", "ENV", "BASH_ENV", "KRB_CONF", |
569b8891 |
1214 | 0 |
1215 | }; |
1216 | |
387501ae |
1217 | /* --- Other useful variables --- */ |
03f996bd |
1218 | |
387501ae |
1219 | sym_env *e; |
1220 | char *p, *q, *r; |
1221 | char **pp, **qq; |
1222 | size_t sz; |
1223 | unsigned f; |
1224 | sym_iter i; |
c6885d5f |
1225 | |
387501ae |
1226 | /* --- Stage one. Preserve display-specific variables --- */ |
569b8891 |
1227 | |
387501ae |
1228 | for (pp = preserve; *pp; pp++) { |
1229 | if ((e = sym_find(&bc__env, *pp, -1, 0, 0)) != 0) |
1230 | e->f |= envFlag_preserve; |
1231 | } |
569b8891 |
1232 | |
387501ae |
1233 | /* --- Stage two. Set Become's own variables --- */ |
569b8891 |
1234 | |
387501ae |
1235 | e = sym_find(&bc__env, "BECOME_ORIGINAL_USER", -1, sizeof(*e), &f); |
1236 | if (!f) |
1237 | bc__setenv(e, from_pw->pw_name); |
1238 | e->f |= envFlag_preserve; |
1239 | |
1240 | e = sym_find(&bc__env, "BECOME_ORIGINAL_HOME", -1, sizeof(*e), &f); |
1241 | if (!f) |
1242 | bc__setenv(e, from_pw->pw_dir); |
1243 | e->f |= envFlag_preserve; |
569b8891 |
1244 | |
387501ae |
1245 | bc__putenv("BECOME_OLD_USER", from_pw->pw_name, envFlag_preserve, 0); |
1246 | bc__putenv("BECOME_OLD_HOME", from_pw->pw_dir, envFlag_preserve, 0); |
1247 | bc__putenv("BECOME_USER", to_pw->pw_name, envFlag_preserve, 0); |
1248 | bc__putenv("BECOME_HOME", to_pw->pw_dir, envFlag_preserve, 0); |
569b8891 |
1249 | |
387501ae |
1250 | /* --- Stage three. Set user identity --- */ |
1251 | |
1252 | switch (style) { |
1253 | case l_login: { |
1254 | static char *maildirs[] = { |
1255 | "/var/spool/mail", "/var/mail", |
1256 | "/usr/spool/mail", "/usr/mail", |
1257 | 0 |
1258 | }; |
1259 | struct stat s; |
1260 | char b[128]; |
1261 | |
1262 | for (pp = maildirs; *pp; pp++) { |
1263 | if (stat(*pp, &s) == 0 && S_ISDIR(s.st_mode)) { |
1264 | sprintf(b, "%s/%s", *pp, to_pw->pw_name); |
1265 | bc__putenv("MAIL", b, envFlag_preserve, 0); |
1266 | break; |
569b8891 |
1267 | } |
569b8891 |
1268 | } |
387501ae |
1269 | } /* Fall through */ |
1270 | |
a5089273 |
1271 | case l_setuser: |
387501ae |
1272 | bc__putenv("USER", to_pw->pw_name, envFlag_preserve, 0); |
1273 | bc__putenv("LOGNAME", to_pw->pw_name, envFlag_preserve, 0); |
1274 | bc__putenv("HOME", to_pw->pw_dir, envFlag_preserve, 0); |
1275 | bc__putenv("SHELL", to_pw->pw_shell, envFlag_preserve, 0); |
1276 | break; |
1277 | } |
1278 | |
1279 | /* --- Stage four. Set the user's PATH properly --- */ |
569b8891 |
1280 | |
387501ae |
1281 | { |
1282 | /* --- Find an existing path --- * |
569b8891 |
1283 | * |
387501ae |
1284 | * If there's no path, or this is a login, then set a default path, |
1285 | * unless we're meant to preserve the existing one. Whew! |
569b8891 |
1286 | */ |
1287 | |
387501ae |
1288 | e = sym_find(&bc__env, "PATH", -1, sizeof(*e), &f); |
1289 | |
1290 | if (!f || (style == l_login && ~e->f & envFlag_preserve)) { |
1291 | bc__putenv("PATH", |
1292 | rq.to ? "/usr/bin:/bin" : "/usr/bin:/usr/sbin:/bin:/sbin", |
1293 | envFlag_preserve, 0); |
1294 | } else { |
1295 | |
1296 | /* --- Find the string --- */ |
1297 | |
1298 | e->f = envFlag_preserve; |
1299 | p = strchr(e->val, '=') + 1; |
1300 | r = e->val; |
1301 | |
1302 | /* --- Write the new version to a dynamically allocated buffer --- */ |
1303 | |
1304 | e->val = xmalloc(4 + 1 + strlen(p) + 1); |
1305 | strcpy(e->val, "PATH="); |
1306 | q = e->val + 5; |
1307 | |
1308 | for (p = strtok(p, ":"); p; p = strtok(0, ":")) { |
6a4ec25c |
1309 | if (p[0] != '/') |
387501ae |
1310 | continue; |
1311 | while (*p) |
1312 | *q++ = *p++; |
1313 | *q++ = ':'; |
1314 | } |
1315 | q[-1] = 0; |
1316 | |
1317 | /* --- Done! --- */ |
1318 | |
1319 | free(r); |
569b8891 |
1320 | } |
387501ae |
1321 | } |
1322 | |
1323 | /* --- Stages five and six. Expunge variables and count numbers --- * |
1324 | * |
1325 | * Folded together, so I only need one pass through the table. Also |
1326 | * count the number of variables needed at this time. |
1327 | */ |
1328 | |
1329 | sz = 0; |
569b8891 |
1330 | |
387501ae |
1331 | for (sym_createIter(&i, &bc__env); (e = sym_next(&i)) != 0; ) { |
569b8891 |
1332 | |
387501ae |
1333 | /* --- Login style expunges all unpreserved variables --- */ |
569b8891 |
1334 | |
387501ae |
1335 | if (style == l_login && ~e->f & envFlag_preserve) |
1336 | goto expunge; |
1337 | |
1338 | /* --- Otherwise just check the name against the list --- */ |
1339 | |
1340 | for (pp = banned; *pp; pp++) { |
1341 | if (**pp == '-') { |
1342 | p = *pp + 1; |
1343 | if (memcmp(e->_base.name, p, strlen(p)) == 0) |
1344 | goto expunge; |
a5089273 |
1345 | } else if (strcmp(e->_base.name, *pp) == 0) |
387501ae |
1346 | goto expunge; |
1347 | } |
1348 | |
1349 | sz++; |
1350 | continue; |
1351 | |
1352 | expunge: |
1353 | sym_remove(&bc__env, e); |
569b8891 |
1354 | } |
387501ae |
1355 | |
1356 | /* --- Stage seven. Build the new environment block --- */ |
1357 | |
1358 | env = qq = xmalloc((sz + 1) * sizeof(*qq)); |
1359 | |
1360 | for (sym_createIter(&i, &bc__env); (e = sym_next(&i)) != 0; ) |
1361 | *qq++ = e->val; |
1362 | *qq++ = 0; |
03f996bd |
1363 | } |
1364 | |
1365 | /* --- Trace the command --- */ |
1366 | |
1367 | IF_TRACING(TRACE_SETUP, { |
1368 | int i; |
1369 | |
1370 | trace(TRACE_SETUP, "setup: from user %s to user %s", |
1371 | from_pw->pw_name, to_pw->pw_name); |
1372 | trace(TRACE_SETUP, "setup: binary == `%s'", binary); |
1373 | for (i = 0; todo[i]; i++) |
1374 | trace(TRACE_SETUP, "setup: arg %i == `%s'", i, todo[i]); |
1375 | for (i = 0; env[i]; i++) |
1376 | trace(TRACE_SETUP, "setup: env %i == `%s'", i, env[i]); |
1377 | }) |
1378 | |
c4f2d992 |
1379 | /* --- If necessary, resolve the path to the command --- */ |
1380 | |
03f996bd |
1381 | if (!strchr(binary, '/')) { |
1382 | char *path, *p; |
c4f2d992 |
1383 | struct stat st; |
c4f2d992 |
1384 | |
1385 | if ((p = getenv("PATH")) == 0) |
1386 | p = "/bin:/usr/bin"; |
03f996bd |
1387 | path = xstrdup(p); |
c4f2d992 |
1388 | |
569b8891 |
1389 | for (p = strtok(path, ":"); p; p = strtok(0, ":")) { |
c4f2d992 |
1390 | |
569b8891 |
1391 | /* --- Check length of string before copying --- */ |
c4f2d992 |
1392 | |
03f996bd |
1393 | if (strlen(p) + strlen(binary) + 2 > sizeof(rq.cmd)) |
c4f2d992 |
1394 | continue; |
1395 | |
59f147b0 |
1396 | /* --- Now build the pathname and check it --- * |
1397 | * |
1398 | * Issue: user can take advantage of these privileges to decide whether |
1399 | * a program with a given name exists. I'm not sure that's |
1400 | * particularly significant: it only works on regular files with |
1401 | * execute permissions, and if you're relying on the names of these |
1402 | * being secret to keep your security up, then you're doing something |
1403 | * deeply wrong anyway. On the other hand, it's useful to allow people |
1404 | * to be able to execute programs and scripts which they wouldn't |
1405 | * otherwise have access to. [This problem was brought up on |
1406 | * Bugtraq, as a complaint against sudo.] |
1407 | */ |
c4f2d992 |
1408 | |
eb961767 |
1409 | if (!*p) p = "."; |
59f147b0 |
1410 | sprintf(rq.cmd, "%s/%s", p, binary); |
03f996bd |
1411 | if (stat(rq.cmd, &st) == 0 && /* Check it exists */ |
c4f2d992 |
1412 | st.st_mode & 0111 && /* Check it's executable */ |
c6885d5f |
1413 | S_ISREG(st.st_mode)) /* Check it's a file */ |
c4f2d992 |
1414 | break; |
1415 | } |
1416 | |
1417 | if (!p) |
1418 | die("couldn't find `%s' in path", todo[0]); |
03f996bd |
1419 | binary = rq.cmd; |
c4f2d992 |
1420 | free(path); |
1421 | } |
03f996bd |
1422 | T( trace(TRACE_SETUP, "setup: resolve binary to `%s'", binary); ) |
c4f2d992 |
1423 | |
1424 | /* --- Canonicalise the path string, if necessary --- */ |
1425 | |
1426 | { |
1427 | char b[CMDLEN_MAX]; |
1428 | char *p; |
1429 | const char *q; |
1430 | |
1431 | /* --- Insert current directory name if path not absolute --- */ |
1432 | |
1433 | p = b; |
03f996bd |
1434 | q = binary; |
c4f2d992 |
1435 | if (*q != '/') { |
1436 | if (!getcwd(b, sizeof(b))) |
1437 | die("couldn't read current directory: %s", strerror(errno)); |
1438 | p += strlen(p); |
1439 | *p++ = '/'; |
1440 | } |
1441 | |
1442 | /* --- Now copy over characters from the path string --- */ |
1443 | |
1444 | while (*q) { |
1445 | |
569b8891 |
1446 | /* --- Check for buffer overflows here --- * |
c4f2d992 |
1447 | * |
1448 | * I write at most one byte per iteration so this is OK. Remember to |
1449 | * allow one for the null byte. |
1450 | */ |
1451 | |
1452 | if (p >= b + sizeof(b) - 1) |
03f996bd |
1453 | die("internal error: buffer overflow while canonifying path"); |
c4f2d992 |
1454 | |
1455 | /* --- Reduce multiple slashes to just one --- */ |
1456 | |
1457 | if (*q == '/') { |
1458 | while (*q == '/') |
1459 | q++; |
1460 | *p++ = '/'; |
1461 | } |
1462 | |
1463 | /* --- Handle dots in filenames --- * |
1464 | * |
1465 | * @p[-1]@ is valid here, because if @*q@ is not a `/' then either |
1466 | * we've just stuck the current directory on the end of the buffer, |
1467 | * or we've just put something else on the end. |
1468 | */ |
1469 | |
1470 | else if (*q == '.' && p[-1] == '/') { |
1471 | |
1472 | /* --- A simple `./' just gets removed --- */ |
1473 | |
1474 | if (q[1] == 0 || q[1] == '/') { |
1475 | q++; |
1476 | p--; |
1477 | continue; |
1478 | } |
1479 | |
1480 | /* --- A `../' needs to be peeled back to the previous `/' --- */ |
1481 | |
1482 | if (q[1] == '.' && (q[2] == 0 || q[2] == '/')) { |
1483 | q += 2; |
1484 | p--; |
1485 | while (p > b && p[-1] != '/') |
1486 | p--; |
1487 | if (p > b) |
1488 | p--; |
1489 | continue; |
1490 | } |
1491 | } else |
1492 | *p++ = *q++; |
1493 | } |
1494 | |
1495 | *p++ = 0; |
1496 | strcpy(rq.cmd, b); |
1497 | } |
03f996bd |
1498 | T( trace(TRACE_SETUP, "setup: canonify binary to `%s'", rq.cmd); ) |
c4f2d992 |
1499 | |
88e486d5 |
1500 | /* --- Run the check --- * |
1501 | * |
1502 | * If the user is already what she wants to be, then print a warning. |
1503 | * Then, if I was just going to spawn a shell, quit, to reduce user |
a5089273 |
1504 | * confusion. Otherwise, do what was wanted anyway. Also, don't bother |
1505 | * checking if we're already root -- root can do anything anyway, and at |
1506 | * least this way we get some logging done, and offer a more friendly |
1507 | * front-end. |
88e486d5 |
1508 | */ |
c4f2d992 |
1509 | |
88e486d5 |
1510 | if (rq.from == rq.to) { |
1511 | moan("you already are `%s'!", to_pw->pw_name); |
45df69ab |
1512 | if (flags & f_shell) { |
88e486d5 |
1513 | moan("(to prevent confusion, I'm not spawning a shell)"); |
1514 | exit(0); |
1515 | } |
1516 | } else { |
a5089273 |
1517 | int a = (rq.from == 0) || check(&rq); |
c4f2d992 |
1518 | |
1519 | syslog(LOG_INFO, |
1520 | "permission %s for %s to become %s to run `%s'", |
03f996bd |
1521 | a ? "granted" : "denied", from_pw->pw_name, to_pw->pw_name, |
1522 | rq.cmd); |
c4f2d992 |
1523 | |
1524 | if (!a) |
1525 | die("permission denied"); |
1526 | } |
1527 | |
1528 | /* --- Now do the job --- */ |
1529 | |
03f996bd |
1530 | T( trace(TRACE_MISC, "become: permission granted"); ) |
1531 | |
1532 | if (flags & f_dummy) { |
1533 | puts("permission granted"); |
1534 | return (0); |
03f996bd |
1535 | } |
a5089273 |
1536 | |
1537 | #ifdef HAVE_SETGROUPS |
1538 | if (setgroups(ngroups, groups) < 0) |
1539 | die("couldn't set groups: %s", strerror(errno)); |
1540 | #endif |
1541 | |
1542 | if (setgid(group) < 0) |
1543 | die("couldn't set default group: %s", strerror(errno)); |
1544 | if (setuid(rq.to) < 0) |
1545 | die("couldn't set uid: %s", strerror(errno)); |
1546 | |
45df69ab |
1547 | /* --- If this was a login, change current directory --- */ |
1548 | |
f175e71b |
1549 | if ((flags & f_shell) && |
1550 | style == l_login && |
1551 | chdir(to_pw->pw_dir) < 0) { |
45df69ab |
1552 | moan("couldn't change directory to `%s': %s", |
1553 | to_pw->pw_dir, strerror(errno)); |
1554 | } |
1555 | |
a5089273 |
1556 | /* --- Finally, call the program --- */ |
1557 | |
1558 | fflush(0); |
46a5b3c6 |
1559 | closelog(); |
a5089273 |
1560 | execve(rq.cmd, todo, env); |
1561 | die("couldn't exec `%s': %s", rq.cmd, strerror(errno)); |
1562 | return (127); |
c4f2d992 |
1563 | } |
1564 | |
1565 | /*----- That's all, folks -------------------------------------------------*/ |