c4f2d992 |
1 | /* -*-c-*- |
2 | * |
569b8891 |
3 | * $Id: become.c,v 1.4 1997/08/20 16:15:13 mdw Exp $ |
c4f2d992 |
4 | * |
5 | * Main code for `become' |
6 | * |
7 | * (c) 1997 EBI |
8 | */ |
9 | |
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10 | /*----- Licensing notice --------------------------------------------------* |
c4f2d992 |
11 | * |
12 | * This file is part of `become' |
13 | * |
14 | * `Become' is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU General Public License as published by |
16 | * the Free Software Foundation; either version 2 of the License, or |
17 | * (at your option) any later version. |
18 | * |
19 | * `Become' is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU General Public License |
03f996bd |
25 | * along with `become'; if not, write to the Free Software Foundation, |
26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
c4f2d992 |
27 | */ |
28 | |
29 | /*----- Revision history --------------------------------------------------* |
30 | * |
31 | * $Log: become.c,v $ |
569b8891 |
32 | * Revision 1.4 1997/08/20 16:15:13 mdw |
33 | * Overhaul of environment handling. Fix daft bug in path search code. |
34 | * |
88e486d5 |
35 | * Revision 1.3 1997/08/07 16:28:59 mdw |
36 | * Do something useful when users attempt to become themselves. |
37 | * |
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38 | * Revision 1.2 1997/08/04 10:24:20 mdw |
39 | * Sources placed under CVS control. |
40 | * |
41 | * Revision 1.1 1997/07/21 13:47:54 mdw |
c4f2d992 |
42 | * Initial revision |
43 | * |
44 | */ |
45 | |
46 | /*----- Header files ------------------------------------------------------*/ |
47 | |
48 | /* --- ANSI headers --- */ |
49 | |
50 | #include <ctype.h> |
51 | #include <errno.h> |
52 | #include <stdio.h> |
53 | #include <stdlib.h> |
54 | #include <string.h> |
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55 | #include <time.h> |
c4f2d992 |
56 | |
57 | /* --- Unix headers --- */ |
58 | |
59 | #include <sys/types.h> |
60 | #include <sys/stat.h> |
61 | #include <sys/socket.h> |
62 | #include <sys/utsname.h> |
63 | |
64 | #include <netinet/in.h> |
65 | |
66 | #include <arpa/inet.h> |
67 | |
68 | #include <netdb.h> |
69 | #include <pwd.h> |
70 | #include <syslog.h> |
71 | #include <unistd.h> |
72 | |
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73 | extern char **environ; |
74 | |
c4f2d992 |
75 | /* --- Local headers --- */ |
76 | |
77 | #include "become.h" |
78 | #include "config.h" |
79 | #include "check.h" |
80 | #include "daemon.h" |
81 | #include "lexer.h" |
82 | #include "mdwopt.h" |
83 | #include "name.h" |
84 | #include "parser.h" |
85 | #include "rule.h" |
86 | #include "utils.h" |
03f996bd |
87 | #include "userdb.h" |
c4f2d992 |
88 | |
89 | /*----- Main code ---------------------------------------------------------*/ |
90 | |
91 | /* --- @bc__write@ --- * |
92 | * |
93 | * Arguments: @FILE *fp@ = pointer to a stream to write on |
94 | * @const char *p@ = pointer to a string |
95 | * |
96 | * Returns: --- |
97 | * |
98 | * Use: Writes the string to the stream, substituting the program |
99 | * name (as returned by @quis@) for each occurrence of the |
100 | * character `$'. |
101 | */ |
102 | |
103 | static void bc__write(FILE *fp, const char *p) |
104 | { |
105 | const char *n = quis(); |
106 | size_t l; |
107 | size_t nl = strlen(n); |
108 | |
109 | /* --- Try to be a little efficient --- * |
110 | * |
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111 | * Gather up non-`$' characters using @strcspn@ and spew them out really |
c4f2d992 |
112 | * quickly. |
113 | */ |
114 | |
115 | for (;;) { |
116 | l = strcspn(p, "$"); |
117 | if (l) |
118 | fwrite(p, l, 1, fp); |
119 | p += l; |
120 | if (!*p) |
121 | break; |
122 | fwrite(n, nl, 1, fp); |
123 | p++; |
124 | } |
125 | } |
126 | |
127 | /* --- @bc__banner@ --- * |
128 | * |
129 | * Arguments: @FILE *fp@ = stream to write on |
130 | * |
131 | * Returns: --- |
132 | * |
133 | * Use: Writes a banner containing copyright information. |
134 | */ |
135 | |
136 | static void bc__banner(FILE *fp) |
137 | { |
138 | bc__write(fp, "$ version " VERSION "\n"); |
139 | } |
140 | |
141 | /* --- @bc__usage@ --- * |
142 | * |
143 | * Arguments: @FILE *fp@ = stream to write on |
144 | * |
145 | * Returns: --- |
146 | * |
147 | * Use: Writes a terse reminder of command line syntax. |
148 | */ |
149 | |
150 | static void bc__usage(FILE *fp) |
151 | { |
152 | bc__write(fp, |
153 | "Usage: \n" |
154 | " $ -c <shell-command> <user>\n" |
155 | " $ <user> [<command> [<arguments>]...]\n" |
156 | " $ -d [-p <port>] [-f <config-file>]\n"); |
157 | } |
158 | |
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159 | /* --- @bc__makeEnv@ --- * |
160 | * |
161 | * Arguments: @const char *var@ = name of an environment variable |
162 | * @const char *value@ = value of the variable |
163 | * |
164 | * Returns: A pointer to an allocated block assigning the value to the |
165 | * name. |
166 | * |
167 | * Use: Constructs environment mappings. |
168 | */ |
169 | |
170 | static char *bc__makeEnv(const char *var, const char *value) |
171 | { |
172 | char *p = xmalloc(strlen(var) + strlen(value) + 2); |
173 | sprintf(p, "%s=%s", var, value); |
174 | return (p); |
175 | } |
176 | |
c4f2d992 |
177 | /* --- @bc__help@ --- * |
178 | * |
179 | * Arguments: @FILE *fp@ = stream to write on |
569b8891 |
180 | * @int suid@ = whether we're running set-uid |
c4f2d992 |
181 | * |
182 | * Returns: --- |
183 | * |
184 | * Use: Displays a help message for this excellent piece of software. |
185 | */ |
186 | |
569b8891 |
187 | static void bc__help(FILE *fp, int suid) |
c4f2d992 |
188 | { |
189 | bc__banner(fp); |
190 | putc('\n', fp); |
191 | bc__usage(fp); |
192 | putc('\n', fp); |
193 | bc__write(fp, |
194 | "The `$' program allows you to run a process as another user.\n" |
195 | "If a command name is given, this is the process executed. If the `-c'\n" |
196 | "option is used, the process is assumed to be `/bin/sh'. If no command is\n" |
197 | "given, your default login shell is used.\n" |
198 | "\n" |
199 | "Your user id, the user id you wish to become, the name of the process\n" |
200 | "you wish to run, and the identity of the current host are looked up to\n" |
201 | "ensure that you have permission to do this.\n" |
202 | "\n" |
203 | "Note that logs are kept of all uses of this program.\n" |
204 | "\n" |
205 | "Options available are:\n" |
206 | "\n" |
207 | "-h, --help Display this help text\n" |
208 | "-v, --version Display the version number of this copy of $\n" |
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209 | "-l, --login Really log in as the user\n" |
c4f2d992 |
210 | "-c, --command=CMD Run the (Bourne) shell command CMD\n" |
211 | "-d, --daemon Start up a daemon, to accept requests from clients\n" |
212 | "-p, --port=PORT In daemon mode, listen on PORT\n" |
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213 | "-f, --config-file=FILE In daemon mode, read config from FILE\n"); |
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214 | #ifdef TRACING |
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215 | if (!suid) { |
216 | bc__write(fp, |
217 | "--impersonate=USER Claim to be USER when asking the server\n"); |
218 | } |
219 | bc__write(fp, |
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220 | "--trace=FILE Dump trace information to FILE (boring)\n" |
569b8891 |
221 | "--trace-level=OPTS Set level of tracing information\n"); |
03f996bd |
222 | #endif |
c4f2d992 |
223 | } |
224 | |
225 | /* --- @main@ --- * |
226 | * |
227 | * Arguments: @int argc@ = number of command line arguments |
228 | * @char *argv[]@ = pointer to the various arguments |
229 | * |
230 | * Returns: Zero if successful. |
231 | * |
232 | * Use: Allows a user to change UID. |
233 | */ |
234 | |
235 | int main(int argc, char *argv[]) |
236 | { |
03f996bd |
237 | /* --- Request block setup parameters --- */ |
c4f2d992 |
238 | |
03f996bd |
239 | request rq; /* Request buffer to build */ |
240 | char *cmd = 0; /* Shell command to execute */ |
241 | char *binary = "/bin/sh"; /* Default binary to execute */ |
242 | char **env = environ; /* Default environment to pass */ |
243 | char **todo; /* Pointer to argument list */ |
244 | struct passwd *from_pw = 0; /* User we are right now */ |
245 | struct passwd *to_pw = 0; /* User we want to become */ |
246 | |
247 | /* --- Become server setup parameters --- */ |
248 | |
249 | char *conffile = file_RULES; /* Default config file for daemon */ |
250 | int port = -1; /* Default port for daemon */ |
251 | |
252 | /* --- Miscellanous shared variables --- */ |
253 | |
254 | unsigned flags = 0; /* Various useful flags */ |
255 | |
256 | /* --- Default argument list executes a shell command --- */ |
257 | |
258 | static char *shell[] = { |
259 | "/bin/sh", /* Bourne shell */ |
260 | "-c", /* Read from command line */ |
261 | 0, /* Pointer to shell command */ |
262 | 0 /* Terminator */ |
c4f2d992 |
263 | }; |
264 | |
03f996bd |
265 | /* --- Definitions for the various flags --- */ |
266 | |
267 | enum { |
268 | f_daemon = 1, /* Start up in daemon mode */ |
269 | f_duff = 2, /* Fault in arguments */ |
270 | f_login = 4, /* Execute as a login shell */ |
271 | f_dummy = 8, /* Don't actually do anything */ |
272 | f_setuid = 16 /* We're running setuid */ |
273 | }; |
c4f2d992 |
274 | |
275 | /* --- Set up the program name --- */ |
276 | |
277 | ego(argv[0]); |
03f996bd |
278 | clock(); |
279 | if (getuid() != geteuid()) |
280 | flags |= f_setuid; |
c4f2d992 |
281 | |
282 | /* --- Parse some command line arguments --- */ |
283 | |
284 | for (;;) { |
285 | int i; |
03f996bd |
286 | static struct option opts[] = { |
c4f2d992 |
287 | { "help", 0, 0, 'h' }, |
569b8891 |
288 | { "usage", 0, 0, 'U' }, |
c4f2d992 |
289 | { "version", 0, 0, 'v' }, |
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290 | { "login", 0, 0, 'l' }, |
c4f2d992 |
291 | { "command", gFlag_argReq, 0, 'c' }, |
292 | { "daemon", 0, 0, 'd' }, |
293 | { "port", gFlag_argReq, 0, 'p' }, |
294 | { "config-file", gFlag_argReq, 0, 'f' }, |
03f996bd |
295 | #ifdef TRACING |
296 | { "impersonate", gFlag_argReq, 0, 'I' }, |
297 | { "trace", gFlag_argOpt, 0, 'T' }, |
298 | { "trace-level", gFlag_argOpt, 0, 'L' }, |
299 | #endif |
c4f2d992 |
300 | { 0, 0, 0, 0 } |
301 | }; |
302 | |
03f996bd |
303 | i = mdwopt(argc, argv, "+hvlc:p:df:", opts, 0, 0, 0); |
c4f2d992 |
304 | if (i < 0) |
305 | break; |
306 | |
307 | switch (i) { |
03f996bd |
308 | |
309 | /* --- Standard help and version options --- */ |
310 | |
c4f2d992 |
311 | case 'h': |
569b8891 |
312 | bc__help(stdout, flags & f_setuid); |
313 | exit(0); |
314 | break; |
315 | case 'U': |
316 | bc__usage(stdout); |
c4f2d992 |
317 | exit(0); |
318 | break; |
319 | case 'v': |
320 | bc__banner(stdout); |
321 | exit(0); |
322 | break; |
03f996bd |
323 | |
324 | /* --- Various simple options --- */ |
325 | |
326 | case 'l': |
327 | flags |= f_login; |
328 | break; |
c4f2d992 |
329 | case 'c': |
330 | cmd = optarg; |
331 | break; |
332 | case 'p': |
333 | port = atoi(optarg); |
334 | break; |
335 | case 'd': |
336 | flags |= f_daemon; |
337 | break; |
338 | case 'f': |
339 | conffile = optarg; |
340 | break; |
03f996bd |
341 | |
342 | /* --- Pretend to be a different user --- * |
343 | * |
344 | * There are all sorts of nasty implications for this option. Don't |
345 | * allow it if we're running setuid. Disable the actual login anyway. |
346 | */ |
347 | |
348 | #ifdef TRACING |
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349 | |
03f996bd |
350 | case 'I': |
351 | if (flags & f_setuid) |
352 | moan("shan't allow impersonation while running setuid"); |
353 | else { |
354 | struct passwd *pw; |
355 | if (isdigit((unsigned char)optarg[0])) |
356 | pw = getpwuid(atoi(optarg)); |
357 | else |
358 | pw = getpwnam(optarg); |
359 | if (!pw) |
360 | die("can't impersonate unknown user `%s'", optarg); |
361 | from_pw = userdb_copyUser(pw); |
362 | rq.from = from_pw->pw_uid; |
363 | flags |= f_dummy; |
364 | } |
c4f2d992 |
365 | break; |
569b8891 |
366 | |
03f996bd |
367 | #endif |
368 | |
369 | /* --- Tracing support --- * |
370 | * |
371 | * Be careful not to zap a file I wouldn't normally be allowed to write |
372 | * to! |
373 | */ |
374 | |
375 | #ifdef TRACING |
376 | |
377 | case 'T': { |
378 | FILE *fp; |
379 | |
380 | if (optarg == 0 || strcmp(optarg, "-") == 0) |
381 | fp = stdout; |
382 | else { |
383 | if ((flags & f_setuid) && access(optarg, W_OK)) { |
384 | die("no write permission for trace file file `%s': %s", |
385 | optarg, strerror(errno)); |
386 | } |
387 | if ((fp = fopen(optarg, "w")) == 0) { |
388 | die("couldn't open trace file `%s' for writing: %s", |
389 | optarg, strerror(errno)); |
390 | } |
391 | } |
392 | traceon(fp, TRACE_DFL); |
393 | trace(TRACE_MISC, "become: tracing enabled"); |
394 | } break; |
395 | |
396 | #endif |
397 | |
398 | /* --- Setting trace levels --- */ |
399 | |
400 | #ifdef TRACING |
401 | |
402 | case 'L': { |
403 | int sense = 1; |
404 | unsigned int lvl = 0, l; |
405 | const char *p = optarg; |
406 | |
407 | /* --- Table of tracing facilities --- */ |
408 | |
409 | typedef struct tr { |
410 | char ch; |
411 | unsigned int l; |
412 | const char *help; |
413 | } tr; |
414 | |
415 | static tr lvltbl[] = { |
416 | { 'm', TRACE_MISC, "miscellaneous messages" }, |
417 | { 's', TRACE_SETUP, "building the request block" }, |
418 | { 'd', TRACE_DAEMON, "server process" }, |
419 | { 'r', TRACE_RULE, "ruleset scanning" }, |
420 | { 'c', TRACE_CHECK, "request checking" }, |
421 | { 'l', TRACE_CLIENT, "client process" }, |
422 | { 'R', TRACE_RAND, "random number generator" }, |
423 | { 'C', TRACE_CRYPTO, "cryptographic processing of requests" }, |
424 | { 'y', TRACE_YACC, "parsing configuration file" }, |
425 | { 'D', TRACE_DFL, "default tracing options" }, |
426 | { 'A', TRACE_ALL, "all tracing options" }, |
427 | { 0, 0, 0 } |
428 | }; |
429 | tr *tp; |
430 | |
431 | /* --- Output some help if there's no arguemnt --- */ |
432 | |
433 | if (!optarg) { |
434 | bc__banner(stdout); |
435 | bc__write(stdout, |
436 | "\n" |
437 | "Tracing options:\n" |
438 | "\n"); |
439 | for (tp = lvltbl; tp->l; tp++) { |
440 | if ((flags & f_setuid) == 0 || tp->l & ~TRACE_PRIV) |
441 | printf("%c -- %s\n", tp->ch, tp->help); |
442 | } |
443 | bc__write(stdout, |
444 | "\n" |
445 | "Also, `+' and `-' options are recognised to turn on and off vavrious\n" |
446 | "tracing options. For example, `A-r' enables everything except ruleset\n" |
447 | "tracing, and `A-D+c' is everything except the defaults, but with request\n" |
448 | "check tracing.\n" |
449 | ); |
450 | exit(0); |
451 | } |
452 | |
453 | while (*p) { |
454 | if (*p == '+') |
455 | sense = 1; |
456 | else if (*p == '-') |
457 | sense = 0; |
458 | else { |
459 | for (tp = lvltbl; tp->l && *p != tp->ch; tp++) |
460 | ; |
461 | l = tp->l; |
462 | if (flags & f_setuid) |
463 | l &= ~TRACE_PRIV; |
464 | if (l) |
465 | lvl = sense ? (lvl | l) : (lvl & ~l); |
466 | else |
467 | moan("unknown trace option `%c'", *p); |
468 | } |
469 | p++; |
470 | } |
471 | |
472 | tracesetlvl(lvl); |
473 | yydebug = ((lvl & TRACE_YACC) != 0); |
474 | } break; |
475 | |
476 | #endif |
477 | |
478 | /* --- Something I didn't understand has occurred --- */ |
479 | |
c4f2d992 |
480 | case '?': |
481 | flags |= f_duff; |
482 | break; |
483 | } |
484 | } |
485 | if (flags & f_duff) { |
486 | bc__usage(stderr); |
487 | exit(1); |
488 | } |
489 | |
490 | /* --- Switch to daemon mode if requested --- */ |
491 | |
492 | if (flags & f_daemon) { |
03f996bd |
493 | T( trace(TRACE_MISC, "become: daemon mode requested"); ) |
c4f2d992 |
494 | daemon_init(conffile, port); |
495 | exit(0); |
496 | } |
497 | |
498 | /* --- Open a syslog --- */ |
499 | |
500 | openlog(quis(), 0, LOG_AUTH); |
501 | |
502 | /* --- Pick out the uid --- */ |
503 | |
504 | { |
505 | const char *u; |
506 | struct passwd *pw; |
03f996bd |
507 | |
c4f2d992 |
508 | if (optind >= argc) { |
509 | bc__usage(stderr); |
510 | exit(1); |
511 | } |
512 | u = argv[optind++]; |
03f996bd |
513 | |
514 | if (isdigit((unsigned char)u[0])) |
c4f2d992 |
515 | pw = getpwuid(atoi(u)); |
03f996bd |
516 | else |
517 | pw = getpwnam(u); |
c4f2d992 |
518 | if (!pw) |
519 | die("unknown user `%s'", u); |
03f996bd |
520 | to_pw = userdb_copyUser(pw); |
c4f2d992 |
521 | rq.to = pw->pw_uid; |
522 | } |
523 | |
524 | /* --- Fill in the easy bits of the request --- */ |
525 | |
03f996bd |
526 | if (!from_pw) { |
527 | struct passwd *pw; |
528 | |
529 | rq.from = getuid(); |
530 | pw = getpwuid(rq.from); |
531 | if (!pw) |
532 | die("who are you? (can't find user %li)", (long)rq.from); |
533 | from_pw = userdb_copyUser(pw); |
534 | } |
c4f2d992 |
535 | |
536 | /* --- Find the local host address --- */ |
537 | |
538 | { |
539 | struct utsname u; |
540 | struct hostent *he; |
541 | uname(&u); |
542 | if ((he = gethostbyname(u.nodename)) == 0) |
543 | die("who am I? (can't resolve `%s')", u.nodename); |
544 | memcpy(&rq.host, he->h_addr, sizeof(struct in_addr)); |
545 | } |
546 | |
03f996bd |
547 | /* --- Shell commands are easy --- */ |
c4f2d992 |
548 | |
549 | if (cmd) { |
550 | shell[2] = cmd; |
551 | todo = shell; |
03f996bd |
552 | } |
553 | |
554 | /* --- A command given on the command line isn't too hard --- */ |
555 | |
556 | else if (optind < argc) { |
c4f2d992 |
557 | todo = argv + optind; |
03f996bd |
558 | binary = todo[0]; |
559 | } |
560 | |
561 | /* --- A login request needs a little bit of work --- */ |
562 | |
563 | else if (flags & f_login) { |
564 | const char *p = strrchr(to_pw->pw_shell, '/'); |
565 | if (p) |
566 | p++; |
567 | else |
568 | p = to_pw->pw_shell; |
569 | shell[0] = xmalloc(strlen(p) + 2); |
570 | shell[0][0] = '-'; |
571 | strcpy(shell[0] + 1, p); |
c4f2d992 |
572 | shell[1] = 0; |
573 | todo = shell; |
03f996bd |
574 | binary = to_pw->pw_shell; |
c4f2d992 |
575 | } |
576 | |
03f996bd |
577 | /* --- An unadorned becoming requires little work --- */ |
578 | |
579 | else { |
569b8891 |
580 | shell[0] = getenv("SHELL"); |
581 | if (!shell[0]) |
582 | shell[0] = from_pw->pw_shell; |
03f996bd |
583 | shell[1] = 0; |
584 | todo = shell; |
585 | binary = todo[0]; |
586 | } |
587 | |
569b8891 |
588 | /* --- Mangle the environment --- * |
589 | * |
590 | * This keeps getting more complicated all the time. |
591 | */ |
592 | |
593 | { |
594 | size_t i, j, b; |
595 | int pass; |
596 | |
597 | /* --- Expunge some environment variables --- * |
598 | * |
599 | * Any environment string which has one of the following as a prefix |
600 | * will be expunged from the environment passed to the called process. |
601 | * The first line lists variables which have been used to list search |
602 | * paths for shared libraries: by manipulating these, an attacker could |
603 | * replace a standard library with one of his own. The second line lists |
604 | * other well-known dangerous environment variables. |
605 | */ |
606 | |
607 | static const char *banned[] = { |
608 | "LD_", "SHLIB_PATH=", "LIBPATH=", "_RLD_", |
609 | "IFS=", "ENV=", "BASH_ENV=", "KRB_CONF=", |
610 | 0 |
611 | }; |
612 | |
613 | /* --- Do this in two passes --- * |
614 | * |
615 | * The first pass works out how big the environment block needs to be. |
616 | * The second actually fills it. |
617 | */ |
03f996bd |
618 | |
569b8891 |
619 | for (pass = 0; pass < 2; pass++) { |
620 | i = j = 0; |
621 | |
622 | if (flags & f_login) { |
623 | |
624 | /* --- This is a login request --- * |
625 | * |
626 | * Erase the existing environment and build a new one. |
627 | */ |
628 | |
629 | if (!pass) |
630 | i += 4; |
631 | else { |
632 | env[i++] = "PATH=/usr/bin:/bin"; |
633 | env[i++] = bc__makeEnv("USER", to_pw->pw_name); |
634 | env[i++] = bc__makeEnv("LOGNAME", to_pw->pw_name); |
635 | env[i++] = bc__makeEnv("HOME", to_pw->pw_dir); |
636 | } |
637 | } else { |
638 | |
639 | /* --- Normal request --- * |
640 | * |
641 | * Remove dangerous variables from the list. |
642 | */ |
643 | |
644 | for (j = 0; environ[j]; j++) { |
645 | for (b = 0; banned[b]; b++) { |
646 | if (memcmp(environ[j], banned[b], strlen(banned[b])) == 0) |
647 | goto skip_var; |
648 | } |
649 | if (pass) |
650 | env[i] = environ[j]; |
651 | i++; |
652 | skip_var:; |
653 | } |
654 | } |
655 | |
656 | /* --- Now add our own variables --- * |
657 | * |
658 | * The following are supplied only to help people construct startup |
659 | * scripts. Anyone who relies on them being accurate for |
660 | * authentication purposes will get exactly what they deserve. |
661 | */ |
662 | |
663 | if (!pass) |
664 | i += 4; |
665 | else { |
666 | env[i++] = bc__makeEnv("BECOME_OLDUSER", from_pw->pw_name); |
667 | env[i++] = bc__makeEnv("BECOME_OLDHOME", from_pw->pw_dir); |
668 | env[i++] = bc__makeEnv("BECOME_USER", to_pw->pw_name); |
669 | env[i++] = bc__makeEnv("BECOME_HOME", to_pw->pw_dir); |
670 | } |
671 | |
672 | /* --- Allocate memory after the first pass is complete --- */ |
673 | |
674 | if (pass) |
675 | env[i] = 0; |
676 | i++; |
677 | |
678 | if (!pass) |
679 | env = xmalloc(i * sizeof(env[0])); |
680 | } |
03f996bd |
681 | } |
682 | |
683 | /* --- Trace the command --- */ |
684 | |
685 | IF_TRACING(TRACE_SETUP, { |
686 | int i; |
687 | |
688 | trace(TRACE_SETUP, "setup: from user %s to user %s", |
689 | from_pw->pw_name, to_pw->pw_name); |
690 | trace(TRACE_SETUP, "setup: binary == `%s'", binary); |
691 | for (i = 0; todo[i]; i++) |
692 | trace(TRACE_SETUP, "setup: arg %i == `%s'", i, todo[i]); |
693 | for (i = 0; env[i]; i++) |
694 | trace(TRACE_SETUP, "setup: env %i == `%s'", i, env[i]); |
695 | }) |
696 | |
c4f2d992 |
697 | /* --- If necessary, resolve the path to the command --- */ |
698 | |
03f996bd |
699 | if (!strchr(binary, '/')) { |
700 | char *path, *p; |
c4f2d992 |
701 | struct stat st; |
c4f2d992 |
702 | |
703 | if ((p = getenv("PATH")) == 0) |
704 | p = "/bin:/usr/bin"; |
03f996bd |
705 | path = xstrdup(p); |
c4f2d992 |
706 | |
569b8891 |
707 | for (p = strtok(path, ":"); p; p = strtok(0, ":")) { |
c4f2d992 |
708 | |
569b8891 |
709 | /* --- Check length of string before copying --- */ |
c4f2d992 |
710 | |
03f996bd |
711 | if (strlen(p) + strlen(binary) + 2 > sizeof(rq.cmd)) |
c4f2d992 |
712 | continue; |
713 | |
714 | /* --- Now build the pathname and check it --- */ |
715 | |
03f996bd |
716 | sprintf(rq.cmd, "%s/%s", p, todo[0]); |
717 | if (stat(rq.cmd, &st) == 0 && /* Check it exists */ |
c4f2d992 |
718 | st.st_mode & 0111 && /* Check it's executable */ |
719 | (st.st_mode & S_IFMT) == S_IFREG) /* Check it's a file */ |
720 | break; |
721 | } |
722 | |
723 | if (!p) |
724 | die("couldn't find `%s' in path", todo[0]); |
03f996bd |
725 | binary = rq.cmd; |
c4f2d992 |
726 | free(path); |
727 | } |
03f996bd |
728 | T( trace(TRACE_SETUP, "setup: resolve binary to `%s'", binary); ) |
c4f2d992 |
729 | |
730 | /* --- Canonicalise the path string, if necessary --- */ |
731 | |
732 | { |
733 | char b[CMDLEN_MAX]; |
734 | char *p; |
735 | const char *q; |
736 | |
737 | /* --- Insert current directory name if path not absolute --- */ |
738 | |
739 | p = b; |
03f996bd |
740 | q = binary; |
c4f2d992 |
741 | if (*q != '/') { |
742 | if (!getcwd(b, sizeof(b))) |
743 | die("couldn't read current directory: %s", strerror(errno)); |
744 | p += strlen(p); |
745 | *p++ = '/'; |
746 | } |
747 | |
748 | /* --- Now copy over characters from the path string --- */ |
749 | |
750 | while (*q) { |
751 | |
569b8891 |
752 | /* --- Check for buffer overflows here --- * |
c4f2d992 |
753 | * |
754 | * I write at most one byte per iteration so this is OK. Remember to |
755 | * allow one for the null byte. |
756 | */ |
757 | |
758 | if (p >= b + sizeof(b) - 1) |
03f996bd |
759 | die("internal error: buffer overflow while canonifying path"); |
c4f2d992 |
760 | |
761 | /* --- Reduce multiple slashes to just one --- */ |
762 | |
763 | if (*q == '/') { |
764 | while (*q == '/') |
765 | q++; |
766 | *p++ = '/'; |
767 | } |
768 | |
769 | /* --- Handle dots in filenames --- * |
770 | * |
771 | * @p[-1]@ is valid here, because if @*q@ is not a `/' then either |
772 | * we've just stuck the current directory on the end of the buffer, |
773 | * or we've just put something else on the end. |
774 | */ |
775 | |
776 | else if (*q == '.' && p[-1] == '/') { |
777 | |
778 | /* --- A simple `./' just gets removed --- */ |
779 | |
780 | if (q[1] == 0 || q[1] == '/') { |
781 | q++; |
782 | p--; |
783 | continue; |
784 | } |
785 | |
786 | /* --- A `../' needs to be peeled back to the previous `/' --- */ |
787 | |
788 | if (q[1] == '.' && (q[2] == 0 || q[2] == '/')) { |
789 | q += 2; |
790 | p--; |
791 | while (p > b && p[-1] != '/') |
792 | p--; |
793 | if (p > b) |
794 | p--; |
795 | continue; |
796 | } |
797 | } else |
798 | *p++ = *q++; |
799 | } |
800 | |
801 | *p++ = 0; |
802 | strcpy(rq.cmd, b); |
803 | } |
03f996bd |
804 | T( trace(TRACE_SETUP, "setup: canonify binary to `%s'", rq.cmd); ) |
c4f2d992 |
805 | |
88e486d5 |
806 | /* --- Run the check --- * |
807 | * |
808 | * If the user is already what she wants to be, then print a warning. |
809 | * Then, if I was just going to spawn a shell, quit, to reduce user |
810 | * confusion. Otherwise, do what was wanted anyway. |
811 | */ |
c4f2d992 |
812 | |
88e486d5 |
813 | if (rq.from == rq.to) { |
814 | moan("you already are `%s'!", to_pw->pw_name); |
815 | if (!cmd && todo == shell) { |
816 | moan("(to prevent confusion, I'm not spawning a shell)"); |
817 | exit(0); |
818 | } |
819 | } else { |
c4f2d992 |
820 | int a = check(&rq); |
c4f2d992 |
821 | |
822 | syslog(LOG_INFO, |
823 | "permission %s for %s to become %s to run `%s'", |
03f996bd |
824 | a ? "granted" : "denied", from_pw->pw_name, to_pw->pw_name, |
825 | rq.cmd); |
c4f2d992 |
826 | |
827 | if (!a) |
828 | die("permission denied"); |
829 | } |
830 | |
831 | /* --- Now do the job --- */ |
832 | |
03f996bd |
833 | T( trace(TRACE_MISC, "become: permission granted"); ) |
834 | |
835 | if (flags & f_dummy) { |
836 | puts("permission granted"); |
837 | return (0); |
838 | } else { |
88e486d5 |
839 | if (setuid(rq.to) == -1) |
03f996bd |
840 | die("couldn't set uid: %s", strerror(errno)); |
841 | execve(rq.cmd, todo, env); |
842 | die("couldn't exec `%s': %s", rq.cmd, strerror(errno)); |
843 | return (127); |
844 | } |
c4f2d992 |
845 | } |
846 | |
847 | /*----- That's all, folks -------------------------------------------------*/ |