c4f2d992 |
1 | /* -*-c-*- |
2 | * |
4c37c6af |
3 | * $Id: become.c,v 1.23 2003/10/12 10:00:06 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 $ |
4c37c6af |
32 | * Revision 1.23 2003/10/12 10:00:06 mdw |
33 | * Fix for daemon mode. Oops. |
34 | * |
f60a3434 |
35 | * Revision 1.22 2003/10/12 00:14:55 mdw |
36 | * Major overhaul. Now uses DSA signatures rather than the bogus symmetric |
37 | * encrypt-and-hope thing. Integrated with mLib and Catacomb. |
38 | * |
eb961767 |
39 | * Revision 1.21 1999/07/28 09:31:01 mdw |
40 | * Empty path components are equivalent to `.'. |
41 | * |
79fae27d |
42 | * Revision 1.20 1999/05/04 16:17:11 mdw |
43 | * Change to header file name for parser. See log for `parse.h' for |
44 | * details. |
45 | * |
46 | * Revision 1.19 1998/06/29 13:10:41 mdw |
59f147b0 |
47 | * Add some commentary regarding an issue in `sudo' which affects `become'; |
48 | * I'm not fixing it yet because I don't think it's important. |
49 | * |
50 | * Fixed the PATH lookup code to use the right binary name: `binary' rather |
51 | * than `todo[0]'. The two only differ when `style' is `l_login', in which |
52 | * case `binary' has an initial `/' anyway, and the PATH lookup code is |
53 | * never invoked. The name is used in a buffer-overflow precheck, though, |
54 | * and auditing is easier if the naming is consistent. |
55 | * |
7df38e1e |
56 | * Revision 1.18 1998/06/26 10:32:54 mdw |
57 | * Cosmetic change: use sizeof(destination) in memcpy. |
58 | * |
46a5b3c6 |
59 | * Revision 1.17 1998/06/18 15:06:59 mdw |
60 | * Close log before execing program to avoid leaving a socket open. |
61 | * |
f175e71b |
62 | * Revision 1.16 1998/04/23 13:21:04 mdw |
63 | * Small tweaks. Support no-network configuration option, and rearrange |
64 | * the help text a little. |
65 | * |
94455fbb |
66 | * Revision 1.15 1998/01/13 11:10:44 mdw |
67 | * Add `TZ' to the list of variables to be preserved. |
68 | * |
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69 | * Revision 1.14 1998/01/12 16:45:39 mdw |
70 | * Fix copyright date. |
71 | * |
9e5602f0 |
72 | * Revision 1.13 1997/09/26 09:14:57 mdw |
73 | * Merged blowfish branch into trunk. |
74 | * |
45df69ab |
75 | * Revision 1.12 1997/09/25 16:04:48 mdw |
76 | * Change directory after becoming someone else, instead of before. This |
77 | * avoids problems with root-squashed NFS mounts. |
78 | * |
9e5602f0 |
79 | * Revision 1.11.2.1 1997/09/26 09:07:58 mdw |
80 | * Use the Blowfish encryption algorithm instead of IDEA. This is partly |
81 | * because I prefer Blowfish (without any particularly strong evidence) but |
82 | * mainly because IDEA is patented and Blowfish isn't. |
83 | * |
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84 | * Revision 1.11 1997/09/24 09:48:45 mdw |
505f2736 |
85 | * Fix (scary) overrun bug in group allocation stuff. |
86 | * |
87 | * Revision 1.10 1997/09/17 10:14:10 mdw |
9df0c75d |
88 | * Fix a typo. Support service names in `--port' option. |
89 | * |
a5089273 |
90 | * Revision 1.9 1997/09/10 10:28:05 mdw |
91 | * Allow default port to be given as a service name or port number. Handle |
92 | * groups properly (lots of options here). |
93 | * |
94 | * Revision 1.8 1997/09/08 13:56:24 mdw |
6a4ec25c |
95 | * Change criteria for expunging items from the user's PATH: instead of |
96 | * removing things starting with `.', remove things not starting with `/'. |
97 | * |
98 | * Revision 1.7 1997/09/08 13:43:20 mdw |
c6885d5f |
99 | * Change userid when creating tracefiles rather than fiddling with |
100 | * `access': it works rather better. Also, insert some stdio buffer |
101 | * flushing to ensure tracedumps are completely written. |
102 | * |
103 | * Revision 1.6 1997/09/05 13:47:44 mdw |
d6683a48 |
104 | * Make the `-L' (trace-level) option's argument optional, like the long |
105 | * version is. |
106 | * |
107 | * Revision 1.5 1997/09/05 11:45:19 mdw |
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108 | * Add support for different login styles, and environment variable |
109 | * manipulation in a safe and useful way. |
110 | * |
111 | * Revision 1.4 1997/08/20 16:15:13 mdw |
569b8891 |
112 | * Overhaul of environment handling. Fix daft bug in path search code. |
113 | * |
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114 | * Revision 1.3 1997/08/07 16:28:59 mdw |
115 | * Do something useful when users attempt to become themselves. |
116 | * |
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117 | * Revision 1.2 1997/08/04 10:24:20 mdw |
118 | * Sources placed under CVS control. |
119 | * |
120 | * Revision 1.1 1997/07/21 13:47:54 mdw |
c4f2d992 |
121 | * Initial revision |
122 | * |
123 | */ |
124 | |
125 | /*----- Header files ------------------------------------------------------*/ |
126 | |
127 | /* --- ANSI headers --- */ |
128 | |
129 | #include <ctype.h> |
130 | #include <errno.h> |
a5089273 |
131 | #include <limits.h> |
c4f2d992 |
132 | #include <stdio.h> |
133 | #include <stdlib.h> |
134 | #include <string.h> |
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135 | #include <time.h> |
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136 | |
137 | /* --- Unix headers --- */ |
138 | |
139 | #include <sys/types.h> |
140 | #include <sys/stat.h> |
141 | #include <sys/socket.h> |
142 | #include <sys/utsname.h> |
143 | |
144 | #include <netinet/in.h> |
145 | |
146 | #include <arpa/inet.h> |
147 | |
148 | #include <netdb.h> |
a5089273 |
149 | #include <grp.h> |
c4f2d992 |
150 | #include <pwd.h> |
151 | #include <syslog.h> |
152 | #include <unistd.h> |
153 | |
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154 | extern char **environ; |
155 | |
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156 | /* --- mLib --- */ |
157 | |
158 | #include <mLib/alloc.h> |
159 | #include <mLib/mdwopt.h> |
160 | #include <mLib/quis.h> |
161 | #include <mLib/report.h> |
162 | #include <mLib/sym.h> |
163 | #include <mLib/trace.h> |
164 | |
c4f2d992 |
165 | /* --- Local headers --- */ |
166 | |
167 | #include "become.h" |
168 | #include "config.h" |
169 | #include "check.h" |
170 | #include "daemon.h" |
171 | #include "lexer.h" |
c4f2d992 |
172 | #include "name.h" |
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173 | #include "parse.h" |
c4f2d992 |
174 | #include "rule.h" |
03f996bd |
175 | #include "userdb.h" |
c4f2d992 |
176 | |
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177 | /*----- Type definitions --------------------------------------------------*/ |
178 | |
179 | /* --- Symbol table entry for an environment variable --- */ |
180 | |
181 | typedef struct sym_env { |
182 | sym_base _base; /* Symbol table information */ |
183 | unsigned f; /* Flags word (see below) */ |
184 | char *val; /* Pointer to variable value */ |
185 | } sym_env; |
186 | |
187 | /* --- Environment variable flags --- */ |
188 | |
189 | enum { |
190 | envFlag_preserve = 1 |
191 | }; |
192 | |
193 | /* --- Login behaviour types --- */ |
194 | |
f175e71b |
195 | #define l_preserve 0 /* Preserve the environment */ |
196 | #define l_setuser 1 /* Update who I am */ |
197 | #define l_login 2 /* Do a full login */ |
387501ae |
198 | |
a5089273 |
199 | /* --- Group behaviour types --- * |
200 | * |
201 | * Note that these make a handy bitfield. |
202 | */ |
203 | |
204 | #ifdef HAVE_SETGROUPS |
205 | |
206 | enum { |
207 | g_unset = 0, /* Nobody's set a preference */ |
208 | g_keep = 1, /* Leave the group memberships */ |
209 | g_replace = 2, /* Replace group memberships */ |
210 | g_merge = (g_keep | g_replace) /* Merge the group memberships */ |
211 | }; |
212 | |
213 | #endif |
214 | |
387501ae |
215 | /*----- Static variables --------------------------------------------------*/ |
216 | |
217 | static sym_table bc__env; |
218 | |
c4f2d992 |
219 | /*----- Main code ---------------------------------------------------------*/ |
220 | |
221 | /* --- @bc__write@ --- * |
222 | * |
223 | * Arguments: @FILE *fp@ = pointer to a stream to write on |
224 | * @const char *p@ = pointer to a string |
225 | * |
226 | * Returns: --- |
227 | * |
228 | * Use: Writes the string to the stream, substituting the program |
229 | * name (as returned by @quis@) for each occurrence of the |
230 | * character `$'. |
231 | */ |
232 | |
233 | static void bc__write(FILE *fp, const char *p) |
234 | { |
235 | const char *n = quis(); |
236 | size_t l; |
237 | size_t nl = strlen(n); |
238 | |
239 | /* --- Try to be a little efficient --- * |
240 | * |
569b8891 |
241 | * Gather up non-`$' characters using @strcspn@ and spew them out really |
c4f2d992 |
242 | * quickly. |
243 | */ |
244 | |
245 | for (;;) { |
246 | l = strcspn(p, "$"); |
247 | if (l) |
248 | fwrite(p, l, 1, fp); |
249 | p += l; |
250 | if (!*p) |
251 | break; |
252 | fwrite(n, nl, 1, fp); |
253 | p++; |
254 | } |
255 | } |
256 | |
387501ae |
257 | /* --- @bc__setenv@ --- * |
258 | * |
259 | * Arguments: @sym_env *e@ = pointer to environment variable block |
260 | * @const char *val@ = value to set |
261 | * |
262 | * Returns: --- |
263 | * |
264 | * Use: Sets an environment variable block to the right value. |
265 | */ |
266 | |
267 | static void bc__setenv(sym_env *e, const char *val) |
268 | { |
269 | e->val = xmalloc(strlen(e->_base.name) + 1 + strlen(val) + 1); |
270 | sprintf(e->val, "%s=%s", e->_base.name, val); |
271 | } |
272 | |
273 | /* --- @bc__putenv@ --- * |
274 | * |
275 | * Arguments: @const char *var@ = name of the variable to set, or 0 if |
276 | * this is embedded in the value string |
277 | * @const char *val@ = value to set, or 0 if the variable must |
278 | * be removed |
279 | * @unsigned int fl@ = flags to set |
280 | * @unsigned int force@ = force overwrite of preserved variables |
281 | * |
282 | * Returns: Pointer to symbol block, or zero if it was deleted. |
283 | * |
284 | * Use: Puts an item into the environment. |
285 | */ |
286 | |
287 | static sym_env *bc__putenv(const char *var, const char *val, |
288 | unsigned int fl, unsigned int force) |
289 | { |
290 | unsigned int f; |
291 | sym_env *e; |
292 | char *q = 0; |
293 | size_t sz; |
294 | |
295 | /* --- Sort out embedded variable names --- */ |
296 | |
297 | if (!var) { |
298 | const char *p = strchr(val, '='); |
299 | |
300 | if (p) { |
301 | sz = p - val; |
302 | q = xmalloc(sz + 1); |
303 | memcpy(q, val, sz); |
304 | q[sz] = 0; |
305 | var = q; |
306 | val = p + 1; |
307 | } else { |
308 | var = val; |
309 | val = 0; |
310 | } |
311 | } |
312 | |
313 | /* --- Find the variable block --- */ |
314 | |
315 | if (val) { |
316 | e = sym_find(&bc__env, var, -1, sizeof(*e), &f); |
a5089273 |
317 | if (!f || ~e->f & envFlag_preserve || force) { |
387501ae |
318 | if (f) |
319 | free(e->val); |
320 | bc__setenv(e, val); |
321 | } |
322 | } else { |
323 | e = sym_find(&bc__env, var, -1, 0, 0); |
324 | if (e && (force || ~e->f & envFlag_preserve)) |
325 | sym_remove(&bc__env, e); |
326 | e = 0; |
327 | } |
328 | |
329 | /* --- Tidy up and return --- */ |
330 | |
331 | if (q) |
332 | free(q); |
333 | if (e) |
334 | e->f = fl; |
335 | return (e); |
336 | } |
337 | |
a5089273 |
338 | /* --- @bc__addGroups@ --- * |
339 | * |
340 | * Arguments: @gid_t *g@ = pointer to a group array |
341 | * @int *png@ = pointer to number of entries in the array |
342 | * @const gid_t *a@ = pointer to groups to add |
343 | * @int na@ = number of groups to add |
344 | * |
345 | * Returns: Zero if it was OK, nonzero if we should stop now. |
346 | * |
347 | * Use: Adds groups to a groups array. |
348 | */ |
349 | |
350 | static int bc__addGroups(gid_t *g, int *png, const gid_t *a, int na) |
351 | { |
352 | int i, j; |
353 | int ng = *png; |
354 | |
355 | for (i = 0; i < na; i++) { |
356 | |
357 | /* --- Ensure this group isn't already in the list --- */ |
358 | |
359 | for (j = 0; j < ng; j++) { |
360 | if (a[i] == g[j]) |
361 | goto next_group; |
362 | } |
363 | |
364 | /* --- See if there's room for more --- */ |
365 | |
505f2736 |
366 | if (ng >= NGROUPS_MAX) { |
367 | moan("too many groups (system limit exceeded) -- some have been lost"); |
a5089273 |
368 | *png = ng; |
369 | return (-1); |
370 | } |
371 | |
372 | /* --- Add the group --- */ |
373 | |
374 | g[ng++] = a[i]; |
375 | next_group:; |
376 | } |
377 | |
378 | *png = ng; |
379 | return (0); |
380 | } |
381 | |
c4f2d992 |
382 | /* --- @bc__banner@ --- * |
383 | * |
384 | * Arguments: @FILE *fp@ = stream to write on |
385 | * |
386 | * Returns: --- |
387 | * |
388 | * Use: Writes a banner containing copyright information. |
389 | */ |
390 | |
391 | static void bc__banner(FILE *fp) |
392 | { |
393 | bc__write(fp, "$ version " VERSION "\n"); |
394 | } |
395 | |
396 | /* --- @bc__usage@ --- * |
397 | * |
398 | * Arguments: @FILE *fp@ = stream to write on |
399 | * |
400 | * Returns: --- |
401 | * |
402 | * Use: Writes a terse reminder of command line syntax. |
403 | */ |
404 | |
405 | static void bc__usage(FILE *fp) |
406 | { |
407 | bc__write(fp, |
408 | "Usage: \n" |
409 | " $ -c <shell-command> <user>\n" |
387501ae |
410 | " $ [<env-var>] <user> [<command> [<arguments>]...]\n" |
f175e71b |
411 | #ifndef NONETWORK |
412 | " $ -d [-p <port>] [-f <config-file>]\n" |
413 | #endif |
414 | ); |
c4f2d992 |
415 | } |
416 | |
417 | /* --- @bc__help@ --- * |
418 | * |
419 | * Arguments: @FILE *fp@ = stream to write on |
569b8891 |
420 | * @int suid@ = whether we're running set-uid |
c4f2d992 |
421 | * |
422 | * Returns: --- |
423 | * |
424 | * Use: Displays a help message for this excellent piece of software. |
425 | */ |
426 | |
569b8891 |
427 | static void bc__help(FILE *fp, int suid) |
c4f2d992 |
428 | { |
429 | bc__banner(fp); |
430 | putc('\n', fp); |
431 | bc__usage(fp); |
432 | putc('\n', fp); |
433 | bc__write(fp, |
434 | "The `$' program allows you to run a process as another user.\n" |
435 | "If a command name is given, this is the process executed. If the `-c'\n" |
436 | "option is used, the process is assumed to be `/bin/sh'. If no command is\n" |
437 | "given, your default login shell is used.\n" |
438 | "\n" |
439 | "Your user id, the user id you wish to become, the name of the process\n" |
440 | "you wish to run, and the identity of the current host are looked up to\n" |
441 | "ensure that you have permission to do this.\n" |
442 | "\n" |
443 | "Note that logs are kept of all uses of this program.\n" |
444 | "\n" |
445 | "Options available are:\n" |
446 | "\n" |
387501ae |
447 | "-h, --help Display this help text\n" |
448 | "-u, --usage Display a short usage summary\n" |
449 | "-v, --version Display $'s version number\n" |
450 | "\n" |
451 | "-e, --preserve-environment Try to preserve the current environment\n" |
452 | "-s, --su, --set-user Set environment variables to reflect USER\n" |
453 | "-l, --login Really log in as USER\n" |
f175e71b |
454 | " [Default is " |
455 | #if DEFAULT_LOGIN_STYLE == l_preserve |
456 | "preserve-environment" |
457 | #elif DEFAULT_LOGIN_STYLE == l_setuser |
458 | "set-user" |
459 | #elif DEFAULT_LOGIN_STYLE == l_login |
460 | "login" |
461 | #else |
462 | "poorly configured" |
463 | #endif |
464 | "]\n\n" |
a5089273 |
465 | "-g GROUP, --group=GROUP Set primary group-id to be GROUP\n" |
466 | #ifdef HAVE_SETGROUPS |
467 | "-k, --keep-groups Keep your current set of groups\n" |
468 | "-m, --merge-groups Merge the lists of groups\n" |
469 | "-r, --replace-groups Replace the list of groups\n" |
470 | #endif |
471 | "\n" |
387501ae |
472 | "-c CMD, --command=CMD Run the (Bourne) shell command CMD\n" |
f175e71b |
473 | #ifndef NONETWORK |
387501ae |
474 | "\n" |
475 | "-d, --daemon Start a daemon\n" |
4c37c6af |
476 | "-n, --nofork In daemon mode, don't fork into background\n" |
387501ae |
477 | "-p PORT, --port=PORT In daemon mode, listen on PORT\n" |
f175e71b |
478 | "-f FILE, --config-file=FILE In daemon mode, read config from FILE\n" |
479 | #endif |
480 | ); |
f60a3434 |
481 | #ifndef NTRACE |
387501ae |
482 | bc__write(fp, "\n"); |
569b8891 |
483 | if (!suid) { |
484 | bc__write(fp, |
387501ae |
485 | "-I USER, --impersonate=USER Claim to be USER when asking the server\n"); |
569b8891 |
486 | } |
487 | bc__write(fp, |
387501ae |
488 | "-T FILE, --trace=FILE Dump trace information to FILE (boring)\n" |
489 | "-L OPTS, --trace-level=OPTS Set level of tracing information\n"); |
03f996bd |
490 | #endif |
c4f2d992 |
491 | } |
492 | |
493 | /* --- @main@ --- * |
494 | * |
495 | * Arguments: @int argc@ = number of command line arguments |
496 | * @char *argv[]@ = pointer to the various arguments |
497 | * |
498 | * Returns: Zero if successful. |
499 | * |
500 | * Use: Allows a user to change UID. |
501 | */ |
502 | |
503 | int main(int argc, char *argv[]) |
504 | { |
03f996bd |
505 | /* --- Request block setup parameters --- */ |
c4f2d992 |
506 | |
03f996bd |
507 | request rq; /* Request buffer to build */ |
508 | char *cmd = 0; /* Shell command to execute */ |
509 | char *binary = "/bin/sh"; /* Default binary to execute */ |
510 | char **env = environ; /* Default environment to pass */ |
387501ae |
511 | char **todo = 0; /* Pointer to argument list */ |
512 | char *who = 0; /* Who we're meant to become */ |
03f996bd |
513 | struct passwd *from_pw = 0; /* User we are right now */ |
514 | struct passwd *to_pw = 0; /* User we want to become */ |
515 | |
516 | /* --- Become server setup parameters --- */ |
517 | |
f175e71b |
518 | #ifndef NONETWORK |
03f996bd |
519 | char *conffile = file_RULES; /* Default config file for daemon */ |
9df0c75d |
520 | int port = 0; /* Default port for daemon */ |
f175e71b |
521 | #endif |
03f996bd |
522 | |
523 | /* --- Miscellanous shared variables --- */ |
524 | |
525 | unsigned flags = 0; /* Various useful flags */ |
387501ae |
526 | int style = DEFAULT_LOGIN_STYLE; /* Login style */ |
a5089273 |
527 | gid_t group = -1; /* Default group to set */ |
528 | int gstyle = g_unset; /* No group style set yet */ |
529 | |
530 | #ifdef HAVE_SETGROUPS |
531 | gid_t groups[NGROUPS_MAX]; /* Set of groups */ |
532 | int ngroups; /* Number of groups in the set */ |
533 | #endif |
03f996bd |
534 | |
535 | /* --- Default argument list executes a shell command --- */ |
536 | |
537 | static char *shell[] = { |
538 | "/bin/sh", /* Bourne shell */ |
539 | "-c", /* Read from command line */ |
540 | 0, /* Pointer to shell command */ |
541 | 0 /* Terminator */ |
c4f2d992 |
542 | }; |
543 | |
03f996bd |
544 | /* --- Definitions for the various flags --- */ |
545 | |
4c37c6af |
546 | #define f_daemon 1u /* Start up in daemon mode */ |
547 | #define f_duff 2u /* Fault in arguments */ |
548 | #define f_shell 4u /* Run a default shell */ |
549 | #define f_dummy 8u /* Don't actually do anything */ |
550 | #define f_setuid 16u /* We're running setuid */ |
551 | #define f_havegroup 32u /* Set a default group */ |
552 | #define f_nofork 64u /* Don't fork into background */ |
c4f2d992 |
553 | |
554 | /* --- Set up the program name --- */ |
555 | |
556 | ego(argv[0]); |
03f996bd |
557 | clock(); |
558 | if (getuid() != geteuid()) |
559 | flags |= f_setuid; |
c4f2d992 |
560 | |
387501ae |
561 | /* --- Read the environment into a hashtable --- */ |
562 | |
563 | { |
564 | char **p; |
565 | |
f60a3434 |
566 | sym_create(&bc__env); |
387501ae |
567 | for (p = environ; *p; p++) |
568 | bc__putenv(0, *p, 0, 0); |
569 | } |
570 | |
c4f2d992 |
571 | /* --- Parse some command line arguments --- */ |
572 | |
573 | for (;;) { |
574 | int i; |
03f996bd |
575 | static struct option opts[] = { |
387501ae |
576 | |
577 | /* --- Asking for help --- */ |
578 | |
c4f2d992 |
579 | { "help", 0, 0, 'h' }, |
387501ae |
580 | { "usage", 0, 0, 'u' }, |
c4f2d992 |
581 | { "version", 0, 0, 'v' }, |
387501ae |
582 | |
583 | /* --- Login style options --- */ |
584 | |
585 | { "preserve-environment", 0, 0, 'e' }, |
586 | { "su", 0, 0, 's' }, |
587 | { "set-user", 0, 0, 's' }, |
03f996bd |
588 | { "login", 0, 0, 'l' }, |
387501ae |
589 | |
a5089273 |
590 | /* --- Group style options --- */ |
591 | |
592 | { "group", gFlag_argReq, 0, 'g' }, |
593 | #ifdef HAVE_SETGROUPS |
594 | { "keep-groups", 0, 0, 'k' }, |
595 | { "merge-groups", 0, 0, 'm' }, |
596 | { "replace-groups", 0, 0, 'r' }, |
597 | #endif |
598 | |
387501ae |
599 | /* --- Command to run options --- */ |
600 | |
c4f2d992 |
601 | { "command", gFlag_argReq, 0, 'c' }, |
387501ae |
602 | |
603 | /* --- Server options --- */ |
604 | |
f175e71b |
605 | #ifndef NONETWORK |
c4f2d992 |
606 | { "daemon", 0, 0, 'd' }, |
4c37c6af |
607 | { "nofork", 0, 0, 'n' }, |
c4f2d992 |
608 | { "port", gFlag_argReq, 0, 'p' }, |
609 | { "config-file", gFlag_argReq, 0, 'f' }, |
f175e71b |
610 | #endif |
387501ae |
611 | |
612 | /* --- Tracing options --- */ |
613 | |
f60a3434 |
614 | #ifndef NTRACE |
03f996bd |
615 | { "impersonate", gFlag_argReq, 0, 'I' }, |
616 | { "trace", gFlag_argOpt, 0, 'T' }, |
617 | { "trace-level", gFlag_argOpt, 0, 'L' }, |
618 | #endif |
387501ae |
619 | |
c4f2d992 |
620 | { 0, 0, 0, 0 } |
621 | }; |
622 | |
387501ae |
623 | i = mdwopt(argc, argv, |
a5089273 |
624 | "-" /* Return non-options as options */ |
625 | "huv" /* Asking for help */ |
626 | "esl" /* Login style options */ |
627 | #ifdef HAVE_SETGROUPS |
628 | "g:kmr" /* Group style options */ |
629 | #else |
630 | "g:" /* Group (without @setgroups@) */ |
631 | #endif |
632 | "c:" /* Command to run options */ |
f175e71b |
633 | #ifndef NONETWORK |
4c37c6af |
634 | "dnp:f:" /* Server options */ |
f175e71b |
635 | #endif |
f60a3434 |
636 | #ifndef NTRACE |
a5089273 |
637 | "I:T::L::" /* Tracing options */ |
638 | #endif |
639 | , |
387501ae |
640 | opts, 0, 0, gFlag_envVar); |
c4f2d992 |
641 | if (i < 0) |
387501ae |
642 | goto done_options; |
c4f2d992 |
643 | |
644 | switch (i) { |
03f996bd |
645 | |
387501ae |
646 | /* --- Asking for help --- */ |
03f996bd |
647 | |
c4f2d992 |
648 | case 'h': |
569b8891 |
649 | bc__help(stdout, flags & f_setuid); |
650 | exit(0); |
651 | break; |
387501ae |
652 | case 'u': |
569b8891 |
653 | bc__usage(stdout); |
c4f2d992 |
654 | exit(0); |
655 | break; |
656 | case 'v': |
657 | bc__banner(stdout); |
658 | exit(0); |
659 | break; |
03f996bd |
660 | |
387501ae |
661 | /* --- Login style options --- */ |
03f996bd |
662 | |
387501ae |
663 | case 'e': |
664 | style = l_preserve; |
665 | break; |
666 | case 's': |
a5089273 |
667 | style = l_setuser; |
387501ae |
668 | break; |
03f996bd |
669 | case 'l': |
387501ae |
670 | style = l_login; |
03f996bd |
671 | break; |
387501ae |
672 | |
a5089273 |
673 | /* --- Group style options --- */ |
674 | |
675 | case 'g': |
676 | if (isdigit((unsigned char)optarg[0])) |
677 | group = atoi(optarg); |
678 | else { |
679 | struct group *gr = getgrnam(optarg); |
680 | if (!gr) |
f60a3434 |
681 | die(1, "unknown group `%s'", optarg); |
a5089273 |
682 | group = gr->gr_gid; |
683 | } |
684 | flags |= f_havegroup; |
685 | break; |
686 | |
687 | case 'k': |
688 | gstyle = g_keep; |
689 | break; |
690 | case 'm': |
691 | gstyle = g_merge; |
692 | break; |
693 | case 'r': |
694 | gstyle = g_replace; |
695 | break; |
696 | |
387501ae |
697 | /* --- Command to run options --- */ |
698 | |
c4f2d992 |
699 | case 'c': |
700 | cmd = optarg; |
701 | break; |
387501ae |
702 | |
703 | /* --- Server options --- */ |
704 | |
f175e71b |
705 | #ifndef NONETWORK |
c4f2d992 |
706 | case 'p': |
a5089273 |
707 | if (isdigit((unsigned char)optarg[0])) |
708 | port = htons(atoi(optarg)); |
709 | else { |
710 | struct servent *s = getservbyname(optarg, "udp"); |
711 | if (!s) |
f60a3434 |
712 | die(1, "unknown service name `%s'", optarg); |
a5089273 |
713 | port = s->s_port; |
714 | } |
c4f2d992 |
715 | break; |
716 | case 'd': |
717 | flags |= f_daemon; |
718 | break; |
4c37c6af |
719 | case 'n': |
720 | flags |= f_nofork; |
721 | break; |
c4f2d992 |
722 | case 'f': |
723 | conffile = optarg; |
724 | break; |
f175e71b |
725 | #endif |
03f996bd |
726 | |
727 | /* --- Pretend to be a different user --- * |
728 | * |
729 | * There are all sorts of nasty implications for this option. Don't |
730 | * allow it if we're running setuid. Disable the actual login anyway. |
731 | */ |
732 | |
f60a3434 |
733 | #ifndef NTRACE |
569b8891 |
734 | |
03f996bd |
735 | case 'I': |
736 | if (flags & f_setuid) |
737 | moan("shan't allow impersonation while running setuid"); |
738 | else { |
739 | struct passwd *pw; |
740 | if (isdigit((unsigned char)optarg[0])) |
741 | pw = getpwuid(atoi(optarg)); |
742 | else |
743 | pw = getpwnam(optarg); |
744 | if (!pw) |
f60a3434 |
745 | die(1, "can't impersonate unknown user `%s'", optarg); |
03f996bd |
746 | from_pw = userdb_copyUser(pw); |
747 | rq.from = from_pw->pw_uid; |
748 | flags |= f_dummy; |
749 | } |
c4f2d992 |
750 | break; |
569b8891 |
751 | |
03f996bd |
752 | #endif |
753 | |
754 | /* --- Tracing support --- * |
755 | * |
756 | * Be careful not to zap a file I wouldn't normally be allowed to write |
757 | * to! |
758 | */ |
759 | |
f60a3434 |
760 | #ifndef TRACE |
03f996bd |
761 | |
762 | case 'T': { |
763 | FILE *fp; |
764 | |
765 | if (optarg == 0 || strcmp(optarg, "-") == 0) |
766 | fp = stdout; |
767 | else { |
c6885d5f |
768 | uid_t eu = geteuid(), ru = getuid(); |
769 | |
770 | #ifdef HAVE_SETREUID |
771 | if (setreuid(eu, ru)) |
772 | #else |
773 | if (seteuid(ru)) |
774 | #endif |
775 | { |
f60a3434 |
776 | die(1, "couldn't temporarily give up privileges: %s", |
c6885d5f |
777 | strerror(errno)); |
03f996bd |
778 | } |
c6885d5f |
779 | |
03f996bd |
780 | if ((fp = fopen(optarg, "w")) == 0) { |
f60a3434 |
781 | die(1, "couldn't open trace file `%s' for writing: %s", |
03f996bd |
782 | optarg, strerror(errno)); |
783 | } |
c6885d5f |
784 | |
785 | #ifdef HAVE_SETREUID |
786 | if (setreuid(ru, eu)) |
787 | #else |
788 | if (seteuid(eu)) |
789 | #endif |
f60a3434 |
790 | die(1, "couldn't regain privileges: %s", strerror(errno)); |
03f996bd |
791 | } |
f60a3434 |
792 | trace_on(fp, TRACE_DFL); |
03f996bd |
793 | trace(TRACE_MISC, "become: tracing enabled"); |
794 | } break; |
795 | |
796 | #endif |
797 | |
798 | /* --- Setting trace levels --- */ |
799 | |
f60a3434 |
800 | #ifndef NTRACE |
03f996bd |
801 | |
802 | case 'L': { |
03f996bd |
803 | |
804 | /* --- Table of tracing facilities --- */ |
805 | |
f60a3434 |
806 | static trace_opt lvltbl[] = { |
03f996bd |
807 | { 'm', TRACE_MISC, "miscellaneous messages" }, |
808 | { 's', TRACE_SETUP, "building the request block" }, |
03f996bd |
809 | { 'r', TRACE_RULE, "ruleset scanning" }, |
810 | { 'c', TRACE_CHECK, "request checking" }, |
f175e71b |
811 | #ifndef NONETWORK |
812 | { 'd', TRACE_DAEMON, "server process" }, |
03f996bd |
813 | { 'l', TRACE_CLIENT, "client process" }, |
814 | { 'R', TRACE_RAND, "random number generator" }, |
815 | { 'C', TRACE_CRYPTO, "cryptographic processing of requests" }, |
f175e71b |
816 | #endif |
03f996bd |
817 | { 'y', TRACE_YACC, "parsing configuration file" }, |
818 | { 'D', TRACE_DFL, "default tracing options" }, |
819 | { 'A', TRACE_ALL, "all tracing options" }, |
820 | { 0, 0, 0 } |
821 | }; |
03f996bd |
822 | |
823 | /* --- Output some help if there's no arguemnt --- */ |
824 | |
f60a3434 |
825 | trace_level(traceopt(lvltbl, optarg, TRACE_DFL, |
826 | (flags & f_setuid) ? TRACE_PRIV : 0)); |
03f996bd |
827 | } break; |
828 | |
829 | #endif |
830 | |
387501ae |
831 | /* --- Something that wasn't an option --- * |
832 | * |
833 | * The following nasties are supported: |
834 | * |
835 | * * NAME=VALUE -- preserve NAME, and give it a VALUE |
836 | * * NAME= -- preserve NAME, and give it an empty value |
837 | * * NAME- -- delete NAME |
838 | * * NAME! -- preserve NAME with existing value |
839 | * |
840 | * Anything else is either the user name (which is OK) or the start of |
841 | * the command (in which case I stop and read the rest of the command). |
842 | */ |
843 | |
844 | case 0: { |
845 | size_t sz = strcspn(optarg, "=-!"); |
846 | sym_env *e; |
847 | |
848 | /* --- None of the above --- */ |
849 | |
850 | if (optarg[sz] == 0 || (optarg[sz] != '=' && optarg[sz + 1] != 0)) { |
9df0c75d |
851 | if (!who) { |
387501ae |
852 | who = optarg; |
9df0c75d |
853 | break; |
854 | } else { |
387501ae |
855 | optind--; |
856 | goto done_options; |
857 | } |
858 | } |
859 | |
860 | /* --- Do the appropriate thing --- */ |
861 | |
862 | switch (optarg[sz]) { |
863 | case '=': |
864 | bc__putenv(0, optarg, envFlag_preserve, 1); |
865 | break; |
866 | case '-': |
867 | optarg[sz] = 0; |
868 | bc__putenv(optarg, 0, 0, 1); |
869 | break; |
870 | case '!': |
871 | optarg[sz] = 0; |
872 | if ((e = sym_find(&bc__env, optarg, -1, 0, 0)) != 0) |
873 | e->f |= envFlag_preserve; |
874 | break; |
875 | } |
876 | } break; |
877 | |
03f996bd |
878 | /* --- Something I didn't understand has occurred --- */ |
879 | |
c4f2d992 |
880 | case '?': |
881 | flags |= f_duff; |
882 | break; |
883 | } |
884 | } |
387501ae |
885 | |
886 | done_options: |
c4f2d992 |
887 | if (flags & f_duff) { |
888 | bc__usage(stderr); |
889 | exit(1); |
890 | } |
891 | |
892 | /* --- Switch to daemon mode if requested --- */ |
893 | |
f175e71b |
894 | #ifndef NONETWORK |
c4f2d992 |
895 | if (flags & f_daemon) { |
03f996bd |
896 | T( trace(TRACE_MISC, "become: daemon mode requested"); ) |
4c37c6af |
897 | daemon_init(conffile, port, (flags & f_nofork) ? df_nofork : 0); |
c4f2d992 |
898 | exit(0); |
899 | } |
f175e71b |
900 | #endif |
c4f2d992 |
901 | |
902 | /* --- Open a syslog --- */ |
903 | |
904 | openlog(quis(), 0, LOG_AUTH); |
905 | |
906 | /* --- Pick out the uid --- */ |
907 | |
908 | { |
c4f2d992 |
909 | struct passwd *pw; |
03f996bd |
910 | |
387501ae |
911 | if (!who) { |
c4f2d992 |
912 | bc__usage(stderr); |
913 | exit(1); |
914 | } |
03f996bd |
915 | |
387501ae |
916 | if (isdigit((unsigned char)who[0])) |
917 | pw = getpwuid(atoi(who)); |
03f996bd |
918 | else |
387501ae |
919 | pw = getpwnam(who); |
c4f2d992 |
920 | if (!pw) |
f60a3434 |
921 | die(1, "unknown user `%s'", who); |
03f996bd |
922 | to_pw = userdb_copyUser(pw); |
c4f2d992 |
923 | rq.to = pw->pw_uid; |
924 | } |
925 | |
926 | /* --- Fill in the easy bits of the request --- */ |
927 | |
03f996bd |
928 | if (!from_pw) { |
929 | struct passwd *pw; |
930 | |
931 | rq.from = getuid(); |
932 | pw = getpwuid(rq.from); |
933 | if (!pw) |
f60a3434 |
934 | die(1, "who are you? (can't find user %li)", (long)rq.from); |
03f996bd |
935 | from_pw = userdb_copyUser(pw); |
936 | } |
c4f2d992 |
937 | |
938 | /* --- Find the local host address --- */ |
939 | |
940 | { |
941 | struct utsname u; |
942 | struct hostent *he; |
943 | uname(&u); |
944 | if ((he = gethostbyname(u.nodename)) == 0) |
f60a3434 |
945 | die(1, "who am I? (can't resolve `%s')", u.nodename); |
7df38e1e |
946 | memcpy(&rq.host, he->h_addr, sizeof(rq.host)); |
c4f2d992 |
947 | } |
948 | |
a5089273 |
949 | /* --- Fiddle with group ownerships a bit --- */ |
950 | |
951 | { |
952 | #ifdef HAVE_SETGROUPS |
953 | gid_t from_gr[NGROUPS_MAX], to_gr[NGROUPS_MAX]; |
954 | int n_fgr, n_tgr; |
955 | #endif |
956 | |
957 | /* --- Set the default login group, if there is one --- */ |
958 | |
959 | if (~flags & f_havegroup) |
960 | group = (style == l_preserve) ? from_pw->pw_gid : to_pw->pw_gid; |
961 | |
962 | #ifndef HAVE_SETGROUPS |
963 | |
964 | /* --- Check that it's valid --- */ |
965 | |
966 | if (group != from_pw->pw_gid && group != to_pw->pw_gid) |
f60a3434 |
967 | die(1, "invalid default group"); |
a5089273 |
968 | |
969 | #else |
970 | |
971 | /* --- Set the default group style --- */ |
972 | |
973 | if (gstyle == g_unset) |
974 | gstyle = (style == l_login) ? g_replace : g_merge; |
975 | |
976 | /* --- Read in my current set of groups --- */ |
977 | |
978 | n_fgr = getgroups(NGROUPS_MAX, from_gr); |
979 | |
980 | /* --- Now read the groups for the target user --- * |
981 | * |
982 | * Do this even if I'm using the @g_keep@ style -- I'll use it for |
983 | * checking that @group@ is valid. |
984 | */ |
985 | |
986 | { |
987 | struct group *gr; |
988 | char **p; |
989 | |
990 | n_tgr = 0; |
991 | to_gr[n_tgr++] = to_pw->pw_gid; |
992 | |
993 | setgrent(); |
994 | while ((gr = getgrent()) != 0) { |
995 | if (gr->gr_gid == to_gr[0]) |
996 | continue; |
997 | for (p = gr->gr_mem; *p; p++) { |
998 | if (strcmp(to_pw->pw_name, *p) == 0) { |
999 | to_gr[n_tgr++] = gr->gr_gid; |
1000 | if (n_tgr >= NGROUPS_MAX) |
1001 | goto done_groups; |
1002 | break; |
1003 | } |
1004 | } |
1005 | } |
1006 | |
1007 | done_groups: |
1008 | endgrent(); |
1009 | } |
1010 | |
1011 | /* --- Check that @group@ is reasonable --- */ |
1012 | |
1013 | { |
1014 | int i; |
1015 | |
1016 | if (group == getgid() || group == from_pw->pw_gid) |
1017 | goto group_ok; |
1018 | for (i = 0; i < n_fgr; i++) { |
1019 | if (group == from_gr[i]) |
1020 | goto group_ok; |
1021 | } |
1022 | for (i = 0; i < n_tgr; i++) { |
1023 | if (group == to_gr[i]) |
1024 | goto group_ok; |
1025 | } |
f60a3434 |
1026 | die(1, "invalid default group"); |
a5089273 |
1027 | group_ok:; |
1028 | } |
1029 | |
1030 | /* --- Phew. Now comes the hard bit --- */ |
1031 | |
1032 | { |
1033 | gid_t ga[4]; |
1034 | int i; |
1035 | |
1036 | i = 0; |
1037 | ga[i++] = group; |
1038 | if (gstyle & g_keep) { |
1039 | ga[i++] = getgid(); |
1040 | ga[i++] = from_pw->pw_gid; |
1041 | } |
1042 | if (gstyle & g_replace) |
1043 | ga[i++] = to_pw->pw_gid; |
1044 | |
1045 | /* --- Style authorities will become apoplectic if shown this --- * |
1046 | * |
1047 | * As far as I can see, it's the neatest way of writing it. |
1048 | */ |
1049 | |
1050 | ngroups = 0; |
1051 | (void)(bc__addGroups(groups, &ngroups, ga, i) || |
1052 | ((gstyle & g_keep) && |
f175e71b |
1053 | bc__addGroups(groups, &ngroups, from_gr, n_fgr)) || |
a5089273 |
1054 | ((gstyle & g_replace) && |
1055 | bc__addGroups(groups, &ngroups, to_gr, n_tgr))); |
1056 | } |
1057 | |
1058 | #endif |
1059 | |
1060 | /* --- Trace the results of all this --- */ |
1061 | |
1062 | T( trace(TRACE_SETUP, "setup: default group == %i", (int)group); ) |
1063 | |
1064 | #ifdef HAVE_SETGROUPS |
1065 | IF_TRACING(TRACE_SETUP, { |
1066 | int i; |
1067 | |
1068 | for (i = 1; i < ngroups; i++) |
1069 | trace(TRACE_SETUP, "setup: subsidiary group %i", (int)groups[i]); |
1070 | }) |
1071 | #endif |
1072 | } |
1073 | |
03f996bd |
1074 | /* --- Shell commands are easy --- */ |
c4f2d992 |
1075 | |
1076 | if (cmd) { |
1077 | shell[2] = cmd; |
1078 | todo = shell; |
03f996bd |
1079 | } |
1080 | |
1081 | /* --- A command given on the command line isn't too hard --- */ |
1082 | |
1083 | else if (optind < argc) { |
c4f2d992 |
1084 | todo = argv + optind; |
03f996bd |
1085 | binary = todo[0]; |
1086 | } |
1087 | |
45df69ab |
1088 | else { |
1089 | flags |= f_shell; |
03f996bd |
1090 | |
45df69ab |
1091 | switch (style) { |
c4f2d992 |
1092 | |
45df69ab |
1093 | /* --- An unadorned becoming requires little work --- */ |
03f996bd |
1094 | |
45df69ab |
1095 | case l_preserve: |
1096 | shell[0] = getenv("SHELL"); |
1097 | if (!shell[0]) |
1098 | shell[0] = from_pw->pw_shell; |
1099 | shell[1] = 0; |
1100 | todo = shell; |
1101 | binary = todo[0]; |
1102 | break; |
387501ae |
1103 | |
45df69ab |
1104 | /* --- An su-like login needs slightly less effort --- */ |
1105 | |
1106 | case l_setuser: |
1107 | shell[0] = to_pw->pw_shell; |
1108 | shell[1] = 0; |
1109 | todo = shell; |
1110 | binary = todo[0]; |
1111 | break; |
1112 | |
1113 | /* --- A login request needs a little bit of work --- */ |
387501ae |
1114 | |
45df69ab |
1115 | case l_login: { |
1116 | const char *p = strrchr(to_pw->pw_shell, '/'); |
1117 | |
1118 | if (p) |
1119 | p++; |
1120 | else |
1121 | p = to_pw->pw_shell; |
1122 | shell[0] = xmalloc(strlen(p) + 2); |
1123 | shell[0][0] = '-'; |
1124 | strcpy(shell[0] + 1, p); |
1125 | shell[1] = 0; |
1126 | todo = shell; |
1127 | binary = to_pw->pw_shell; |
1128 | } break; |
1129 | } |
03f996bd |
1130 | } |
1131 | |
569b8891 |
1132 | /* --- Mangle the environment --- * |
1133 | * |
387501ae |
1134 | * This keeps getting more complicated all the time. (How true. Now I've |
1135 | * got all sorts of nasty environment mangling to do.) |
1136 | * |
1137 | * The environment stuff now happens in seven phases: |
1138 | * |
1139 | * 1. Mark very special variables to be preserved. Currently only TERM |
1140 | * and DISPLAY are treated in this way. |
1141 | * |
1142 | * 2. Set and preserve Become's own environment variables. |
1143 | * |
1144 | * 3. Set and preserve the user identity variables (USER, LOGNAME, HOME, |
1145 | * SHELL and MAIL) if we're being `su'-like or `login'-like. |
1146 | * |
1147 | * 4. If we're preserving the environment or being `su'-like, process the |
1148 | * PATH variable a little. Otherwise reset it to something |
1149 | * appropriate. |
1150 | * |
1151 | * 5. If we're being `login'-like, expunge all unpreserved variables. |
1152 | * |
1153 | * 6. Expunge any security-critical variables. |
1154 | * |
1155 | * 7. Build a new environment table to pass to child processes. |
569b8891 |
1156 | */ |
1157 | |
1158 | { |
387501ae |
1159 | /* --- Variables to be preserved always --- * |
1160 | * |
1161 | * A user can explicitly expunge a variable in this list, in which case |
1162 | * we never get to see it here. |
1163 | */ |
569b8891 |
1164 | |
387501ae |
1165 | static char *preserve[] = { |
94455fbb |
1166 | "TERM", "DISPLAY", "TZ", 0 |
387501ae |
1167 | }; |
c6885d5f |
1168 | |
387501ae |
1169 | /* --- Variables to be expunged --- * |
569b8891 |
1170 | * |
c6885d5f |
1171 | * Any environment string which has one of the following as a prefix will |
1172 | * be expunged from the environment passed to the called process. The |
1173 | * first line lists variables which have been used to list search paths |
1174 | * for shared libraries: by manipulating these, an attacker could replace |
1175 | * a standard library with one of his own. The second line lists other |
1176 | * well-known dangerous environment variables. |
569b8891 |
1177 | */ |
1178 | |
387501ae |
1179 | static char *banned[] = { |
1180 | "-LD_", "SHLIB_PATH", "LIBPATH", "-_RLD_", |
1181 | "IFS", "ENV", "BASH_ENV", "KRB_CONF", |
569b8891 |
1182 | 0 |
1183 | }; |
1184 | |
387501ae |
1185 | /* --- Other useful variables --- */ |
03f996bd |
1186 | |
387501ae |
1187 | sym_env *e; |
1188 | char *p, *q, *r; |
1189 | char **pp, **qq; |
1190 | size_t sz; |
1191 | unsigned f; |
1192 | sym_iter i; |
c6885d5f |
1193 | |
387501ae |
1194 | /* --- Stage one. Preserve display-specific variables --- */ |
569b8891 |
1195 | |
387501ae |
1196 | for (pp = preserve; *pp; pp++) { |
1197 | if ((e = sym_find(&bc__env, *pp, -1, 0, 0)) != 0) |
1198 | e->f |= envFlag_preserve; |
1199 | } |
569b8891 |
1200 | |
387501ae |
1201 | /* --- Stage two. Set Become's own variables --- */ |
569b8891 |
1202 | |
387501ae |
1203 | e = sym_find(&bc__env, "BECOME_ORIGINAL_USER", -1, sizeof(*e), &f); |
1204 | if (!f) |
1205 | bc__setenv(e, from_pw->pw_name); |
1206 | e->f |= envFlag_preserve; |
1207 | |
1208 | e = sym_find(&bc__env, "BECOME_ORIGINAL_HOME", -1, sizeof(*e), &f); |
1209 | if (!f) |
1210 | bc__setenv(e, from_pw->pw_dir); |
1211 | e->f |= envFlag_preserve; |
569b8891 |
1212 | |
387501ae |
1213 | bc__putenv("BECOME_OLD_USER", from_pw->pw_name, envFlag_preserve, 0); |
1214 | bc__putenv("BECOME_OLD_HOME", from_pw->pw_dir, envFlag_preserve, 0); |
1215 | bc__putenv("BECOME_USER", to_pw->pw_name, envFlag_preserve, 0); |
1216 | bc__putenv("BECOME_HOME", to_pw->pw_dir, envFlag_preserve, 0); |
569b8891 |
1217 | |
387501ae |
1218 | /* --- Stage three. Set user identity --- */ |
1219 | |
1220 | switch (style) { |
1221 | case l_login: { |
1222 | static char *maildirs[] = { |
1223 | "/var/spool/mail", "/var/mail", |
1224 | "/usr/spool/mail", "/usr/mail", |
1225 | 0 |
1226 | }; |
1227 | struct stat s; |
1228 | char b[128]; |
1229 | |
1230 | for (pp = maildirs; *pp; pp++) { |
1231 | if (stat(*pp, &s) == 0 && S_ISDIR(s.st_mode)) { |
1232 | sprintf(b, "%s/%s", *pp, to_pw->pw_name); |
1233 | bc__putenv("MAIL", b, envFlag_preserve, 0); |
1234 | break; |
569b8891 |
1235 | } |
569b8891 |
1236 | } |
387501ae |
1237 | } /* Fall through */ |
1238 | |
a5089273 |
1239 | case l_setuser: |
387501ae |
1240 | bc__putenv("USER", to_pw->pw_name, envFlag_preserve, 0); |
1241 | bc__putenv("LOGNAME", to_pw->pw_name, envFlag_preserve, 0); |
1242 | bc__putenv("HOME", to_pw->pw_dir, envFlag_preserve, 0); |
1243 | bc__putenv("SHELL", to_pw->pw_shell, envFlag_preserve, 0); |
1244 | break; |
1245 | } |
1246 | |
1247 | /* --- Stage four. Set the user's PATH properly --- */ |
569b8891 |
1248 | |
387501ae |
1249 | { |
1250 | /* --- Find an existing path --- * |
569b8891 |
1251 | * |
387501ae |
1252 | * If there's no path, or this is a login, then set a default path, |
1253 | * unless we're meant to preserve the existing one. Whew! |
569b8891 |
1254 | */ |
1255 | |
387501ae |
1256 | e = sym_find(&bc__env, "PATH", -1, sizeof(*e), &f); |
1257 | |
1258 | if (!f || (style == l_login && ~e->f & envFlag_preserve)) { |
1259 | bc__putenv("PATH", |
1260 | rq.to ? "/usr/bin:/bin" : "/usr/bin:/usr/sbin:/bin:/sbin", |
1261 | envFlag_preserve, 0); |
1262 | } else { |
1263 | |
1264 | /* --- Find the string --- */ |
1265 | |
1266 | e->f = envFlag_preserve; |
1267 | p = strchr(e->val, '=') + 1; |
1268 | r = e->val; |
1269 | |
1270 | /* --- Write the new version to a dynamically allocated buffer --- */ |
1271 | |
1272 | e->val = xmalloc(4 + 1 + strlen(p) + 1); |
1273 | strcpy(e->val, "PATH="); |
1274 | q = e->val + 5; |
1275 | |
1276 | for (p = strtok(p, ":"); p; p = strtok(0, ":")) { |
6a4ec25c |
1277 | if (p[0] != '/') |
387501ae |
1278 | continue; |
1279 | while (*p) |
1280 | *q++ = *p++; |
1281 | *q++ = ':'; |
1282 | } |
1283 | q[-1] = 0; |
1284 | |
1285 | /* --- Done! --- */ |
1286 | |
1287 | free(r); |
569b8891 |
1288 | } |
387501ae |
1289 | } |
1290 | |
1291 | /* --- Stages five and six. Expunge variables and count numbers --- * |
1292 | * |
1293 | * Folded together, so I only need one pass through the table. Also |
1294 | * count the number of variables needed at this time. |
1295 | */ |
1296 | |
1297 | sz = 0; |
569b8891 |
1298 | |
f60a3434 |
1299 | for (sym_mkiter(&i, &bc__env); (e = sym_next(&i)) != 0; ) { |
569b8891 |
1300 | |
387501ae |
1301 | /* --- Login style expunges all unpreserved variables --- */ |
569b8891 |
1302 | |
387501ae |
1303 | if (style == l_login && ~e->f & envFlag_preserve) |
1304 | goto expunge; |
1305 | |
1306 | /* --- Otherwise just check the name against the list --- */ |
1307 | |
1308 | for (pp = banned; *pp; pp++) { |
1309 | if (**pp == '-') { |
1310 | p = *pp + 1; |
1311 | if (memcmp(e->_base.name, p, strlen(p)) == 0) |
1312 | goto expunge; |
a5089273 |
1313 | } else if (strcmp(e->_base.name, *pp) == 0) |
387501ae |
1314 | goto expunge; |
1315 | } |
1316 | |
1317 | sz++; |
1318 | continue; |
1319 | |
1320 | expunge: |
1321 | sym_remove(&bc__env, e); |
569b8891 |
1322 | } |
387501ae |
1323 | |
1324 | /* --- Stage seven. Build the new environment block --- */ |
1325 | |
1326 | env = qq = xmalloc((sz + 1) * sizeof(*qq)); |
1327 | |
f60a3434 |
1328 | for (sym_mkiter(&i, &bc__env); (e = sym_next(&i)) != 0; ) |
387501ae |
1329 | *qq++ = e->val; |
1330 | *qq++ = 0; |
03f996bd |
1331 | } |
1332 | |
1333 | /* --- Trace the command --- */ |
1334 | |
1335 | IF_TRACING(TRACE_SETUP, { |
1336 | int i; |
1337 | |
1338 | trace(TRACE_SETUP, "setup: from user %s to user %s", |
1339 | from_pw->pw_name, to_pw->pw_name); |
1340 | trace(TRACE_SETUP, "setup: binary == `%s'", binary); |
1341 | for (i = 0; todo[i]; i++) |
1342 | trace(TRACE_SETUP, "setup: arg %i == `%s'", i, todo[i]); |
1343 | for (i = 0; env[i]; i++) |
1344 | trace(TRACE_SETUP, "setup: env %i == `%s'", i, env[i]); |
1345 | }) |
1346 | |
c4f2d992 |
1347 | /* --- If necessary, resolve the path to the command --- */ |
1348 | |
03f996bd |
1349 | if (!strchr(binary, '/')) { |
1350 | char *path, *p; |
c4f2d992 |
1351 | struct stat st; |
c4f2d992 |
1352 | |
1353 | if ((p = getenv("PATH")) == 0) |
1354 | p = "/bin:/usr/bin"; |
03f996bd |
1355 | path = xstrdup(p); |
c4f2d992 |
1356 | |
569b8891 |
1357 | for (p = strtok(path, ":"); p; p = strtok(0, ":")) { |
c4f2d992 |
1358 | |
569b8891 |
1359 | /* --- Check length of string before copying --- */ |
c4f2d992 |
1360 | |
03f996bd |
1361 | if (strlen(p) + strlen(binary) + 2 > sizeof(rq.cmd)) |
c4f2d992 |
1362 | continue; |
1363 | |
59f147b0 |
1364 | /* --- Now build the pathname and check it --- * |
1365 | * |
1366 | * Issue: user can take advantage of these privileges to decide whether |
1367 | * a program with a given name exists. I'm not sure that's |
1368 | * particularly significant: it only works on regular files with |
1369 | * execute permissions, and if you're relying on the names of these |
1370 | * being secret to keep your security up, then you're doing something |
1371 | * deeply wrong anyway. On the other hand, it's useful to allow people |
1372 | * to be able to execute programs and scripts which they wouldn't |
1373 | * otherwise have access to. [This problem was brought up on |
1374 | * Bugtraq, as a complaint against sudo.] |
1375 | */ |
c4f2d992 |
1376 | |
eb961767 |
1377 | if (!*p) p = "."; |
59f147b0 |
1378 | sprintf(rq.cmd, "%s/%s", p, binary); |
03f996bd |
1379 | if (stat(rq.cmd, &st) == 0 && /* Check it exists */ |
c4f2d992 |
1380 | st.st_mode & 0111 && /* Check it's executable */ |
c6885d5f |
1381 | S_ISREG(st.st_mode)) /* Check it's a file */ |
c4f2d992 |
1382 | break; |
1383 | } |
1384 | |
1385 | if (!p) |
f60a3434 |
1386 | die(1, "couldn't find `%s' in path", todo[0]); |
03f996bd |
1387 | binary = rq.cmd; |
c4f2d992 |
1388 | free(path); |
1389 | } |
03f996bd |
1390 | T( trace(TRACE_SETUP, "setup: resolve binary to `%s'", binary); ) |
c4f2d992 |
1391 | |
1392 | /* --- Canonicalise the path string, if necessary --- */ |
1393 | |
1394 | { |
1395 | char b[CMDLEN_MAX]; |
1396 | char *p; |
1397 | const char *q; |
1398 | |
1399 | /* --- Insert current directory name if path not absolute --- */ |
1400 | |
1401 | p = b; |
03f996bd |
1402 | q = binary; |
c4f2d992 |
1403 | if (*q != '/') { |
1404 | if (!getcwd(b, sizeof(b))) |
f60a3434 |
1405 | die(1, "couldn't read current directory: %s", strerror(errno)); |
c4f2d992 |
1406 | p += strlen(p); |
1407 | *p++ = '/'; |
1408 | } |
1409 | |
1410 | /* --- Now copy over characters from the path string --- */ |
1411 | |
1412 | while (*q) { |
1413 | |
569b8891 |
1414 | /* --- Check for buffer overflows here --- * |
c4f2d992 |
1415 | * |
1416 | * I write at most one byte per iteration so this is OK. Remember to |
1417 | * allow one for the null byte. |
1418 | */ |
1419 | |
1420 | if (p >= b + sizeof(b) - 1) |
f60a3434 |
1421 | die(1, "internal error: buffer overflow while canonifying path"); |
c4f2d992 |
1422 | |
1423 | /* --- Reduce multiple slashes to just one --- */ |
1424 | |
1425 | if (*q == '/') { |
1426 | while (*q == '/') |
1427 | q++; |
1428 | *p++ = '/'; |
1429 | } |
1430 | |
1431 | /* --- Handle dots in filenames --- * |
1432 | * |
1433 | * @p[-1]@ is valid here, because if @*q@ is not a `/' then either |
1434 | * we've just stuck the current directory on the end of the buffer, |
1435 | * or we've just put something else on the end. |
1436 | */ |
1437 | |
1438 | else if (*q == '.' && p[-1] == '/') { |
1439 | |
1440 | /* --- A simple `./' just gets removed --- */ |
1441 | |
1442 | if (q[1] == 0 || q[1] == '/') { |
1443 | q++; |
1444 | p--; |
1445 | continue; |
1446 | } |
1447 | |
1448 | /* --- A `../' needs to be peeled back to the previous `/' --- */ |
1449 | |
1450 | if (q[1] == '.' && (q[2] == 0 || q[2] == '/')) { |
1451 | q += 2; |
1452 | p--; |
1453 | while (p > b && p[-1] != '/') |
1454 | p--; |
1455 | if (p > b) |
1456 | p--; |
1457 | continue; |
1458 | } |
1459 | } else |
1460 | *p++ = *q++; |
1461 | } |
1462 | |
1463 | *p++ = 0; |
1464 | strcpy(rq.cmd, b); |
1465 | } |
03f996bd |
1466 | T( trace(TRACE_SETUP, "setup: canonify binary to `%s'", rq.cmd); ) |
c4f2d992 |
1467 | |
88e486d5 |
1468 | /* --- Run the check --- * |
1469 | * |
1470 | * If the user is already what she wants to be, then print a warning. |
1471 | * Then, if I was just going to spawn a shell, quit, to reduce user |
a5089273 |
1472 | * confusion. Otherwise, do what was wanted anyway. Also, don't bother |
1473 | * checking if we're already root -- root can do anything anyway, and at |
1474 | * least this way we get some logging done, and offer a more friendly |
1475 | * front-end. |
88e486d5 |
1476 | */ |
c4f2d992 |
1477 | |
88e486d5 |
1478 | if (rq.from == rq.to) { |
1479 | moan("you already are `%s'!", to_pw->pw_name); |
45df69ab |
1480 | if (flags & f_shell) { |
88e486d5 |
1481 | moan("(to prevent confusion, I'm not spawning a shell)"); |
1482 | exit(0); |
1483 | } |
1484 | } else { |
a5089273 |
1485 | int a = (rq.from == 0) || check(&rq); |
c4f2d992 |
1486 | |
1487 | syslog(LOG_INFO, |
1488 | "permission %s for %s to become %s to run `%s'", |
03f996bd |
1489 | a ? "granted" : "denied", from_pw->pw_name, to_pw->pw_name, |
1490 | rq.cmd); |
c4f2d992 |
1491 | |
1492 | if (!a) |
f60a3434 |
1493 | die(1, "permission denied"); |
c4f2d992 |
1494 | } |
1495 | |
1496 | /* --- Now do the job --- */ |
1497 | |
03f996bd |
1498 | T( trace(TRACE_MISC, "become: permission granted"); ) |
1499 | |
1500 | if (flags & f_dummy) { |
1501 | puts("permission granted"); |
1502 | return (0); |
03f996bd |
1503 | } |
a5089273 |
1504 | |
1505 | #ifdef HAVE_SETGROUPS |
1506 | if (setgroups(ngroups, groups) < 0) |
f60a3434 |
1507 | die(1, "couldn't set groups: %s", strerror(errno)); |
a5089273 |
1508 | #endif |
1509 | |
1510 | if (setgid(group) < 0) |
f60a3434 |
1511 | die(1, "couldn't set default group: %s", strerror(errno)); |
a5089273 |
1512 | if (setuid(rq.to) < 0) |
f60a3434 |
1513 | die(1, "couldn't set uid: %s", strerror(errno)); |
a5089273 |
1514 | |
45df69ab |
1515 | /* --- If this was a login, change current directory --- */ |
1516 | |
f175e71b |
1517 | if ((flags & f_shell) && |
1518 | style == l_login && |
1519 | chdir(to_pw->pw_dir) < 0) { |
45df69ab |
1520 | moan("couldn't change directory to `%s': %s", |
1521 | to_pw->pw_dir, strerror(errno)); |
1522 | } |
1523 | |
a5089273 |
1524 | /* --- Finally, call the program --- */ |
1525 | |
1526 | fflush(0); |
46a5b3c6 |
1527 | closelog(); |
a5089273 |
1528 | execve(rq.cmd, todo, env); |
f60a3434 |
1529 | die(1, "couldn't exec `%s': %s", rq.cmd, strerror(errno)); |
a5089273 |
1530 | return (127); |
c4f2d992 |
1531 | } |
1532 | |
1533 | /*----- That's all, folks -------------------------------------------------*/ |