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