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