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