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