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