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