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