c4f2d992 |
1 | /* -*-c-*- |
2 | * |
03f996bd |
3 | * $Id: become.c,v 1.2 1997/08/04 10:24:20 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 $ |
03f996bd |
32 | * Revision 1.2 1997/08/04 10:24:20 mdw |
33 | * Sources placed under CVS control. |
34 | * |
35 | * Revision 1.1 1997/07/21 13:47:54 mdw |
c4f2d992 |
36 | * Initial revision |
37 | * |
38 | */ |
39 | |
40 | /*----- Header files ------------------------------------------------------*/ |
41 | |
42 | /* --- ANSI headers --- */ |
43 | |
44 | #include <ctype.h> |
45 | #include <errno.h> |
46 | #include <stdio.h> |
47 | #include <stdlib.h> |
48 | #include <string.h> |
03f996bd |
49 | #include <time.h> |
c4f2d992 |
50 | |
51 | /* --- Unix headers --- */ |
52 | |
53 | #include <sys/types.h> |
54 | #include <sys/stat.h> |
55 | #include <sys/socket.h> |
56 | #include <sys/utsname.h> |
57 | |
58 | #include <netinet/in.h> |
59 | |
60 | #include <arpa/inet.h> |
61 | |
62 | #include <netdb.h> |
63 | #include <pwd.h> |
64 | #include <syslog.h> |
65 | #include <unistd.h> |
66 | |
03f996bd |
67 | extern char **environ; |
68 | |
c4f2d992 |
69 | /* --- Local headers --- */ |
70 | |
71 | #include "become.h" |
72 | #include "config.h" |
73 | #include "check.h" |
74 | #include "daemon.h" |
75 | #include "lexer.h" |
76 | #include "mdwopt.h" |
77 | #include "name.h" |
78 | #include "parser.h" |
79 | #include "rule.h" |
80 | #include "utils.h" |
03f996bd |
81 | #include "userdb.h" |
c4f2d992 |
82 | |
83 | /*----- Main code ---------------------------------------------------------*/ |
84 | |
85 | /* --- @bc__write@ --- * |
86 | * |
87 | * Arguments: @FILE *fp@ = pointer to a stream to write on |
88 | * @const char *p@ = pointer to a string |
89 | * |
90 | * Returns: --- |
91 | * |
92 | * Use: Writes the string to the stream, substituting the program |
93 | * name (as returned by @quis@) for each occurrence of the |
94 | * character `$'. |
95 | */ |
96 | |
97 | static void bc__write(FILE *fp, const char *p) |
98 | { |
99 | const char *n = quis(); |
100 | size_t l; |
101 | size_t nl = strlen(n); |
102 | |
103 | /* --- Try to be a little efficient --- * |
104 | * |
105 | * Gather up non-`$' characters using @strcpn@ and spew them out really |
106 | * quickly. |
107 | */ |
108 | |
109 | for (;;) { |
110 | l = strcspn(p, "$"); |
111 | if (l) |
112 | fwrite(p, l, 1, fp); |
113 | p += l; |
114 | if (!*p) |
115 | break; |
116 | fwrite(n, nl, 1, fp); |
117 | p++; |
118 | } |
119 | } |
120 | |
121 | /* --- @bc__banner@ --- * |
122 | * |
123 | * Arguments: @FILE *fp@ = stream to write on |
124 | * |
125 | * Returns: --- |
126 | * |
127 | * Use: Writes a banner containing copyright information. |
128 | */ |
129 | |
130 | static void bc__banner(FILE *fp) |
131 | { |
132 | bc__write(fp, "$ version " VERSION "\n"); |
133 | } |
134 | |
135 | /* --- @bc__usage@ --- * |
136 | * |
137 | * Arguments: @FILE *fp@ = stream to write on |
138 | * |
139 | * Returns: --- |
140 | * |
141 | * Use: Writes a terse reminder of command line syntax. |
142 | */ |
143 | |
144 | static void bc__usage(FILE *fp) |
145 | { |
146 | bc__write(fp, |
147 | "Usage: \n" |
148 | " $ -c <shell-command> <user>\n" |
149 | " $ <user> [<command> [<arguments>]...]\n" |
150 | " $ -d [-p <port>] [-f <config-file>]\n"); |
151 | } |
152 | |
03f996bd |
153 | /* --- @bc__makeEnv@ --- * |
154 | * |
155 | * Arguments: @const char *var@ = name of an environment variable |
156 | * @const char *value@ = value of the variable |
157 | * |
158 | * Returns: A pointer to an allocated block assigning the value to the |
159 | * name. |
160 | * |
161 | * Use: Constructs environment mappings. |
162 | */ |
163 | |
164 | static char *bc__makeEnv(const char *var, const char *value) |
165 | { |
166 | char *p = xmalloc(strlen(var) + strlen(value) + 2); |
167 | sprintf(p, "%s=%s", var, value); |
168 | return (p); |
169 | } |
170 | |
c4f2d992 |
171 | /* --- @bc__help@ --- * |
172 | * |
173 | * Arguments: @FILE *fp@ = stream to write on |
174 | * |
175 | * Returns: --- |
176 | * |
177 | * Use: Displays a help message for this excellent piece of software. |
178 | */ |
179 | |
180 | static void bc__help(FILE *fp) |
181 | { |
182 | bc__banner(fp); |
183 | putc('\n', fp); |
184 | bc__usage(fp); |
185 | putc('\n', fp); |
186 | bc__write(fp, |
187 | "The `$' program allows you to run a process as another user.\n" |
188 | "If a command name is given, this is the process executed. If the `-c'\n" |
189 | "option is used, the process is assumed to be `/bin/sh'. If no command is\n" |
190 | "given, your default login shell is used.\n" |
191 | "\n" |
192 | "Your user id, the user id you wish to become, the name of the process\n" |
193 | "you wish to run, and the identity of the current host are looked up to\n" |
194 | "ensure that you have permission to do this.\n" |
195 | "\n" |
196 | "Note that logs are kept of all uses of this program.\n" |
197 | "\n" |
198 | "Options available are:\n" |
199 | "\n" |
200 | "-h, --help Display this help text\n" |
201 | "-v, --version Display the version number of this copy of $\n" |
03f996bd |
202 | "-l, --login Really log in as the user\n" |
c4f2d992 |
203 | "-c, --command=CMD Run the (Bourne) shell command CMD\n" |
204 | "-d, --daemon Start up a daemon, to accept requests from clients\n" |
205 | "-p, --port=PORT In daemon mode, listen on PORT\n" |
206 | "-f, --config-file=FILE In daemon mode, read config from FILE\n" |
03f996bd |
207 | #ifdef TRACING |
208 | "--impersonate=USER Claim to be USER when asking the server\n" |
209 | "--trace=FILE Dump trace information to FILE (boring)\n" |
210 | "--trace-level=OPTS Set level of tracing information\n" |
211 | #endif |
212 | ); |
c4f2d992 |
213 | } |
214 | |
215 | /* --- @main@ --- * |
216 | * |
217 | * Arguments: @int argc@ = number of command line arguments |
218 | * @char *argv[]@ = pointer to the various arguments |
219 | * |
220 | * Returns: Zero if successful. |
221 | * |
222 | * Use: Allows a user to change UID. |
223 | */ |
224 | |
225 | int main(int argc, char *argv[]) |
226 | { |
03f996bd |
227 | /* --- Request block setup parameters --- */ |
c4f2d992 |
228 | |
03f996bd |
229 | request rq; /* Request buffer to build */ |
230 | char *cmd = 0; /* Shell command to execute */ |
231 | char *binary = "/bin/sh"; /* Default binary to execute */ |
232 | char **env = environ; /* Default environment to pass */ |
233 | char **todo; /* Pointer to argument list */ |
234 | struct passwd *from_pw = 0; /* User we are right now */ |
235 | struct passwd *to_pw = 0; /* User we want to become */ |
236 | |
237 | /* --- Become server setup parameters --- */ |
238 | |
239 | char *conffile = file_RULES; /* Default config file for daemon */ |
240 | int port = -1; /* Default port for daemon */ |
241 | |
242 | /* --- Miscellanous shared variables --- */ |
243 | |
244 | unsigned flags = 0; /* Various useful flags */ |
245 | |
246 | /* --- Default argument list executes a shell command --- */ |
247 | |
248 | static char *shell[] = { |
249 | "/bin/sh", /* Bourne shell */ |
250 | "-c", /* Read from command line */ |
251 | 0, /* Pointer to shell command */ |
252 | 0 /* Terminator */ |
c4f2d992 |
253 | }; |
254 | |
03f996bd |
255 | /* --- Login request replaces the environment with this --- */ |
256 | |
257 | static char *mangled_env[] = { |
258 | "PATH=/bin:/usr/bin", /* Default `clean' path*/ |
259 | 0, /* User's name (`USER') */ |
260 | 0, /* User's name (`LOGNAME') */ |
261 | 0, /* Home directory (`HOME') */ |
262 | 0 /* Terminator */ |
263 | }; |
264 | |
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' }, |
288 | { "version", 0, 0, 'v' }, |
03f996bd |
289 | { "login", 0, 0, 'l' }, |
c4f2d992 |
290 | { "command", gFlag_argReq, 0, 'c' }, |
291 | { "daemon", 0, 0, 'd' }, |
292 | { "port", gFlag_argReq, 0, 'p' }, |
293 | { "config-file", gFlag_argReq, 0, 'f' }, |
03f996bd |
294 | #ifdef TRACING |
295 | { "impersonate", gFlag_argReq, 0, 'I' }, |
296 | { "trace", gFlag_argOpt, 0, 'T' }, |
297 | { "trace-level", gFlag_argOpt, 0, 'L' }, |
298 | #endif |
c4f2d992 |
299 | { 0, 0, 0, 0 } |
300 | }; |
301 | |
03f996bd |
302 | i = mdwopt(argc, argv, "+hvlc:p:df:", opts, 0, 0, 0); |
c4f2d992 |
303 | if (i < 0) |
304 | break; |
305 | |
306 | switch (i) { |
03f996bd |
307 | |
308 | /* --- Standard help and version options --- */ |
309 | |
c4f2d992 |
310 | case 'h': |
311 | bc__help(stdout); |
312 | exit(0); |
313 | break; |
314 | case 'v': |
315 | bc__banner(stdout); |
316 | exit(0); |
317 | break; |
03f996bd |
318 | |
319 | /* --- Various simple options --- */ |
320 | |
321 | case 'l': |
322 | flags |= f_login; |
323 | break; |
c4f2d992 |
324 | case 'c': |
325 | cmd = optarg; |
326 | break; |
327 | case 'p': |
328 | port = atoi(optarg); |
329 | break; |
330 | case 'd': |
331 | flags |= f_daemon; |
332 | break; |
333 | case 'f': |
334 | conffile = optarg; |
335 | break; |
03f996bd |
336 | |
337 | /* --- Pretend to be a different user --- * |
338 | * |
339 | * There are all sorts of nasty implications for this option. Don't |
340 | * allow it if we're running setuid. Disable the actual login anyway. |
341 | */ |
342 | |
343 | #ifdef TRACING |
344 | case 'I': |
345 | if (flags & f_setuid) |
346 | moan("shan't allow impersonation while running setuid"); |
347 | else { |
348 | struct passwd *pw; |
349 | if (isdigit((unsigned char)optarg[0])) |
350 | pw = getpwuid(atoi(optarg)); |
351 | else |
352 | pw = getpwnam(optarg); |
353 | if (!pw) |
354 | die("can't impersonate unknown user `%s'", optarg); |
355 | from_pw = userdb_copyUser(pw); |
356 | rq.from = from_pw->pw_uid; |
357 | flags |= f_dummy; |
358 | } |
c4f2d992 |
359 | break; |
03f996bd |
360 | #endif |
361 | |
362 | /* --- Tracing support --- * |
363 | * |
364 | * Be careful not to zap a file I wouldn't normally be allowed to write |
365 | * to! |
366 | */ |
367 | |
368 | #ifdef TRACING |
369 | |
370 | case 'T': { |
371 | FILE *fp; |
372 | |
373 | if (optarg == 0 || strcmp(optarg, "-") == 0) |
374 | fp = stdout; |
375 | else { |
376 | if ((flags & f_setuid) && access(optarg, W_OK)) { |
377 | die("no write permission for trace file file `%s': %s", |
378 | optarg, strerror(errno)); |
379 | } |
380 | if ((fp = fopen(optarg, "w")) == 0) { |
381 | die("couldn't open trace file `%s' for writing: %s", |
382 | optarg, strerror(errno)); |
383 | } |
384 | } |
385 | traceon(fp, TRACE_DFL); |
386 | trace(TRACE_MISC, "become: tracing enabled"); |
387 | } break; |
388 | |
389 | #endif |
390 | |
391 | /* --- Setting trace levels --- */ |
392 | |
393 | #ifdef TRACING |
394 | |
395 | case 'L': { |
396 | int sense = 1; |
397 | unsigned int lvl = 0, l; |
398 | const char *p = optarg; |
399 | |
400 | /* --- Table of tracing facilities --- */ |
401 | |
402 | typedef struct tr { |
403 | char ch; |
404 | unsigned int l; |
405 | const char *help; |
406 | } tr; |
407 | |
408 | static tr lvltbl[] = { |
409 | { 'm', TRACE_MISC, "miscellaneous messages" }, |
410 | { 's', TRACE_SETUP, "building the request block" }, |
411 | { 'd', TRACE_DAEMON, "server process" }, |
412 | { 'r', TRACE_RULE, "ruleset scanning" }, |
413 | { 'c', TRACE_CHECK, "request checking" }, |
414 | { 'l', TRACE_CLIENT, "client process" }, |
415 | { 'R', TRACE_RAND, "random number generator" }, |
416 | { 'C', TRACE_CRYPTO, "cryptographic processing of requests" }, |
417 | { 'y', TRACE_YACC, "parsing configuration file" }, |
418 | { 'D', TRACE_DFL, "default tracing options" }, |
419 | { 'A', TRACE_ALL, "all tracing options" }, |
420 | { 0, 0, 0 } |
421 | }; |
422 | tr *tp; |
423 | |
424 | /* --- Output some help if there's no arguemnt --- */ |
425 | |
426 | if (!optarg) { |
427 | bc__banner(stdout); |
428 | bc__write(stdout, |
429 | "\n" |
430 | "Tracing options:\n" |
431 | "\n"); |
432 | for (tp = lvltbl; tp->l; tp++) { |
433 | if ((flags & f_setuid) == 0 || tp->l & ~TRACE_PRIV) |
434 | printf("%c -- %s\n", tp->ch, tp->help); |
435 | } |
436 | bc__write(stdout, |
437 | "\n" |
438 | "Also, `+' and `-' options are recognised to turn on and off vavrious\n" |
439 | "tracing options. For example, `A-r' enables everything except ruleset\n" |
440 | "tracing, and `A-D+c' is everything except the defaults, but with request\n" |
441 | "check tracing.\n" |
442 | ); |
443 | exit(0); |
444 | } |
445 | |
446 | while (*p) { |
447 | if (*p == '+') |
448 | sense = 1; |
449 | else if (*p == '-') |
450 | sense = 0; |
451 | else { |
452 | for (tp = lvltbl; tp->l && *p != tp->ch; tp++) |
453 | ; |
454 | l = tp->l; |
455 | if (flags & f_setuid) |
456 | l &= ~TRACE_PRIV; |
457 | if (l) |
458 | lvl = sense ? (lvl | l) : (lvl & ~l); |
459 | else |
460 | moan("unknown trace option `%c'", *p); |
461 | } |
462 | p++; |
463 | } |
464 | |
465 | tracesetlvl(lvl); |
466 | yydebug = ((lvl & TRACE_YACC) != 0); |
467 | } break; |
468 | |
469 | #endif |
470 | |
471 | /* --- Something I didn't understand has occurred --- */ |
472 | |
c4f2d992 |
473 | case '?': |
474 | flags |= f_duff; |
475 | break; |
476 | } |
477 | } |
478 | if (flags & f_duff) { |
479 | bc__usage(stderr); |
480 | exit(1); |
481 | } |
482 | |
483 | /* --- Switch to daemon mode if requested --- */ |
484 | |
485 | if (flags & f_daemon) { |
03f996bd |
486 | T( trace(TRACE_MISC, "become: daemon mode requested"); ) |
c4f2d992 |
487 | daemon_init(conffile, port); |
488 | exit(0); |
489 | } |
490 | |
491 | /* --- Open a syslog --- */ |
492 | |
493 | openlog(quis(), 0, LOG_AUTH); |
494 | |
495 | /* --- Pick out the uid --- */ |
496 | |
497 | { |
498 | const char *u; |
499 | struct passwd *pw; |
03f996bd |
500 | |
c4f2d992 |
501 | if (optind >= argc) { |
502 | bc__usage(stderr); |
503 | exit(1); |
504 | } |
505 | u = argv[optind++]; |
03f996bd |
506 | |
507 | if (isdigit((unsigned char)u[0])) |
c4f2d992 |
508 | pw = getpwuid(atoi(u)); |
03f996bd |
509 | else |
510 | pw = getpwnam(u); |
c4f2d992 |
511 | if (!pw) |
512 | die("unknown user `%s'", u); |
03f996bd |
513 | to_pw = userdb_copyUser(pw); |
c4f2d992 |
514 | rq.to = pw->pw_uid; |
515 | } |
516 | |
517 | /* --- Fill in the easy bits of the request --- */ |
518 | |
03f996bd |
519 | if (!from_pw) { |
520 | struct passwd *pw; |
521 | |
522 | rq.from = getuid(); |
523 | pw = getpwuid(rq.from); |
524 | if (!pw) |
525 | die("who are you? (can't find user %li)", (long)rq.from); |
526 | from_pw = userdb_copyUser(pw); |
527 | } |
c4f2d992 |
528 | |
529 | /* --- Find the local host address --- */ |
530 | |
531 | { |
532 | struct utsname u; |
533 | struct hostent *he; |
534 | uname(&u); |
535 | if ((he = gethostbyname(u.nodename)) == 0) |
536 | die("who am I? (can't resolve `%s')", u.nodename); |
537 | memcpy(&rq.host, he->h_addr, sizeof(struct in_addr)); |
538 | } |
539 | |
03f996bd |
540 | /* --- Shell commands are easy --- */ |
c4f2d992 |
541 | |
542 | if (cmd) { |
543 | shell[2] = cmd; |
544 | todo = shell; |
03f996bd |
545 | } |
546 | |
547 | /* --- A command given on the command line isn't too hard --- */ |
548 | |
549 | else if (optind < argc) { |
c4f2d992 |
550 | todo = argv + optind; |
03f996bd |
551 | binary = todo[0]; |
552 | } |
553 | |
554 | /* --- A login request needs a little bit of work --- */ |
555 | |
556 | else if (flags & f_login) { |
557 | const char *p = strrchr(to_pw->pw_shell, '/'); |
558 | if (p) |
559 | p++; |
560 | else |
561 | p = to_pw->pw_shell; |
562 | shell[0] = xmalloc(strlen(p) + 2); |
563 | shell[0][0] = '-'; |
564 | strcpy(shell[0] + 1, p); |
c4f2d992 |
565 | shell[1] = 0; |
566 | todo = shell; |
03f996bd |
567 | binary = to_pw->pw_shell; |
c4f2d992 |
568 | } |
569 | |
03f996bd |
570 | /* --- An unadorned becoming requires little work --- */ |
571 | |
572 | else { |
573 | shell[0] = from_pw->pw_shell; |
574 | shell[1] = 0; |
575 | todo = shell; |
576 | binary = todo[0]; |
577 | } |
578 | |
579 | /* --- Mangle the environment if login flag given --- */ |
580 | |
581 | if (flags & f_login) { |
582 | env = mangled_env; |
583 | env[1] = bc__makeEnv("USER", to_pw->pw_name); |
584 | env[2] = bc__makeEnv("LOGNAME", to_pw->pw_name); |
585 | env[3] = bc__makeEnv("HOME", to_pw->pw_dir); |
586 | } |
587 | |
588 | /* --- Trace the command --- */ |
589 | |
590 | IF_TRACING(TRACE_SETUP, { |
591 | int i; |
592 | |
593 | trace(TRACE_SETUP, "setup: from user %s to user %s", |
594 | from_pw->pw_name, to_pw->pw_name); |
595 | trace(TRACE_SETUP, "setup: binary == `%s'", binary); |
596 | for (i = 0; todo[i]; i++) |
597 | trace(TRACE_SETUP, "setup: arg %i == `%s'", i, todo[i]); |
598 | for (i = 0; env[i]; i++) |
599 | trace(TRACE_SETUP, "setup: env %i == `%s'", i, env[i]); |
600 | }) |
601 | |
c4f2d992 |
602 | /* --- If necessary, resolve the path to the command --- */ |
603 | |
03f996bd |
604 | if (!strchr(binary, '/')) { |
605 | char *path, *p; |
c4f2d992 |
606 | struct stat st; |
c4f2d992 |
607 | |
608 | if ((p = getenv("PATH")) == 0) |
609 | p = "/bin:/usr/bin"; |
03f996bd |
610 | path = xstrdup(p); |
c4f2d992 |
611 | |
612 | for (p = strtok(path, ":"); (p = strtok(0, ":")) != 0; ) { |
613 | |
614 | /* --- SECURITY: check length of string before copying --- */ |
615 | |
03f996bd |
616 | if (strlen(p) + strlen(binary) + 2 > sizeof(rq.cmd)) |
c4f2d992 |
617 | continue; |
618 | |
619 | /* --- Now build the pathname and check it --- */ |
620 | |
03f996bd |
621 | sprintf(rq.cmd, "%s/%s", p, todo[0]); |
622 | if (stat(rq.cmd, &st) == 0 && /* Check it exists */ |
c4f2d992 |
623 | st.st_mode & 0111 && /* Check it's executable */ |
624 | (st.st_mode & S_IFMT) == S_IFREG) /* Check it's a file */ |
625 | break; |
626 | } |
627 | |
628 | if (!p) |
629 | die("couldn't find `%s' in path", todo[0]); |
03f996bd |
630 | binary = rq.cmd; |
c4f2d992 |
631 | free(path); |
632 | } |
03f996bd |
633 | T( trace(TRACE_SETUP, "setup: resolve binary to `%s'", binary); ) |
c4f2d992 |
634 | |
635 | /* --- Canonicalise the path string, if necessary --- */ |
636 | |
637 | { |
638 | char b[CMDLEN_MAX]; |
639 | char *p; |
640 | const char *q; |
641 | |
642 | /* --- Insert current directory name if path not absolute --- */ |
643 | |
644 | p = b; |
03f996bd |
645 | q = binary; |
c4f2d992 |
646 | if (*q != '/') { |
647 | if (!getcwd(b, sizeof(b))) |
648 | die("couldn't read current directory: %s", strerror(errno)); |
649 | p += strlen(p); |
650 | *p++ = '/'; |
651 | } |
652 | |
653 | /* --- Now copy over characters from the path string --- */ |
654 | |
655 | while (*q) { |
656 | |
657 | /* --- SECURITY: check for buffer overflows here --- * |
658 | * |
659 | * I write at most one byte per iteration so this is OK. Remember to |
660 | * allow one for the null byte. |
661 | */ |
662 | |
663 | if (p >= b + sizeof(b) - 1) |
03f996bd |
664 | die("internal error: buffer overflow while canonifying path"); |
c4f2d992 |
665 | |
666 | /* --- Reduce multiple slashes to just one --- */ |
667 | |
668 | if (*q == '/') { |
669 | while (*q == '/') |
670 | q++; |
671 | *p++ = '/'; |
672 | } |
673 | |
674 | /* --- Handle dots in filenames --- * |
675 | * |
676 | * @p[-1]@ is valid here, because if @*q@ is not a `/' then either |
677 | * we've just stuck the current directory on the end of the buffer, |
678 | * or we've just put something else on the end. |
679 | */ |
680 | |
681 | else if (*q == '.' && p[-1] == '/') { |
682 | |
683 | /* --- A simple `./' just gets removed --- */ |
684 | |
685 | if (q[1] == 0 || q[1] == '/') { |
686 | q++; |
687 | p--; |
688 | continue; |
689 | } |
690 | |
691 | /* --- A `../' needs to be peeled back to the previous `/' --- */ |
692 | |
693 | if (q[1] == '.' && (q[2] == 0 || q[2] == '/')) { |
694 | q += 2; |
695 | p--; |
696 | while (p > b && p[-1] != '/') |
697 | p--; |
698 | if (p > b) |
699 | p--; |
700 | continue; |
701 | } |
702 | } else |
703 | *p++ = *q++; |
704 | } |
705 | |
706 | *p++ = 0; |
707 | strcpy(rq.cmd, b); |
708 | } |
03f996bd |
709 | T( trace(TRACE_SETUP, "setup: canonify binary to `%s'", rq.cmd); ) |
c4f2d992 |
710 | |
711 | /* --- Run the check --- */ |
712 | |
713 | { |
714 | int a = check(&rq); |
c4f2d992 |
715 | |
716 | syslog(LOG_INFO, |
717 | "permission %s for %s to become %s to run `%s'", |
03f996bd |
718 | a ? "granted" : "denied", from_pw->pw_name, to_pw->pw_name, |
719 | rq.cmd); |
c4f2d992 |
720 | |
721 | if (!a) |
722 | die("permission denied"); |
723 | } |
724 | |
725 | /* --- Now do the job --- */ |
726 | |
03f996bd |
727 | T( trace(TRACE_MISC, "become: permission granted"); ) |
728 | |
729 | if (flags & f_dummy) { |
730 | puts("permission granted"); |
731 | return (0); |
732 | } else { |
733 | if (setuid(rq.to) == -1 || seteuid(rq.to) == -1) |
734 | die("couldn't set uid: %s", strerror(errno)); |
735 | execve(rq.cmd, todo, env); |
736 | die("couldn't exec `%s': %s", rq.cmd, strerror(errno)); |
737 | return (127); |
738 | } |
c4f2d992 |
739 | } |
740 | |
741 | /*----- That's all, folks -------------------------------------------------*/ |