| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: become.c,v 1.7 1997/09/08 13:43:20 mdw Exp $ |
| 4 | * |
| 5 | * Main code for `become' |
| 6 | * |
| 7 | * (c) 1997 EBI |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 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 |
| 25 | * along with `become'; if not, write to the Free Software Foundation, |
| 26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 27 | */ |
| 28 | |
| 29 | /*----- Revision history --------------------------------------------------* |
| 30 | * |
| 31 | * $Log: become.c,v $ |
| 32 | * Revision 1.7 1997/09/08 13:43:20 mdw |
| 33 | * Change userid when creating tracefiles rather than fiddling with |
| 34 | * `access': it works rather better. Also, insert some stdio buffer |
| 35 | * flushing to ensure tracedumps are completely written. |
| 36 | * |
| 37 | * Revision 1.6 1997/09/05 13:47:44 mdw |
| 38 | * Make the `-L' (trace-level) option's argument optional, like the long |
| 39 | * version is. |
| 40 | * |
| 41 | * Revision 1.5 1997/09/05 11:45:19 mdw |
| 42 | * Add support for different login styles, and environment variable |
| 43 | * manipulation in a safe and useful way. |
| 44 | * |
| 45 | * Revision 1.4 1997/08/20 16:15:13 mdw |
| 46 | * Overhaul of environment handling. Fix daft bug in path search code. |
| 47 | * |
| 48 | * Revision 1.3 1997/08/07 16:28:59 mdw |
| 49 | * Do something useful when users attempt to become themselves. |
| 50 | * |
| 51 | * Revision 1.2 1997/08/04 10:24:20 mdw |
| 52 | * Sources placed under CVS control. |
| 53 | * |
| 54 | * Revision 1.1 1997/07/21 13:47:54 mdw |
| 55 | * Initial revision |
| 56 | * |
| 57 | */ |
| 58 | |
| 59 | /*----- Header files ------------------------------------------------------*/ |
| 60 | |
| 61 | /* --- ANSI headers --- */ |
| 62 | |
| 63 | #include <ctype.h> |
| 64 | #include <errno.h> |
| 65 | #include <stdio.h> |
| 66 | #include <stdlib.h> |
| 67 | #include <string.h> |
| 68 | #include <time.h> |
| 69 | |
| 70 | /* --- Unix headers --- */ |
| 71 | |
| 72 | #include <sys/types.h> |
| 73 | #include <sys/stat.h> |
| 74 | #include <sys/socket.h> |
| 75 | #include <sys/utsname.h> |
| 76 | |
| 77 | #include <netinet/in.h> |
| 78 | |
| 79 | #include <arpa/inet.h> |
| 80 | |
| 81 | #include <netdb.h> |
| 82 | #include <pwd.h> |
| 83 | #include <syslog.h> |
| 84 | #include <unistd.h> |
| 85 | |
| 86 | extern char **environ; |
| 87 | |
| 88 | /* --- Local headers --- */ |
| 89 | |
| 90 | #include "become.h" |
| 91 | #include "config.h" |
| 92 | #include "check.h" |
| 93 | #include "daemon.h" |
| 94 | #include "lexer.h" |
| 95 | #include "mdwopt.h" |
| 96 | #include "name.h" |
| 97 | #include "parser.h" |
| 98 | #include "rule.h" |
| 99 | #include "sym.h" |
| 100 | #include "utils.h" |
| 101 | #include "userdb.h" |
| 102 | |
| 103 | /*----- Type definitions --------------------------------------------------*/ |
| 104 | |
| 105 | /* --- Symbol table entry for an environment variable --- */ |
| 106 | |
| 107 | typedef struct sym_env { |
| 108 | sym_base _base; /* Symbol table information */ |
| 109 | unsigned f; /* Flags word (see below) */ |
| 110 | char *val; /* Pointer to variable value */ |
| 111 | } sym_env; |
| 112 | |
| 113 | /* --- Environment variable flags --- */ |
| 114 | |
| 115 | enum { |
| 116 | envFlag_preserve = 1 |
| 117 | }; |
| 118 | |
| 119 | /* --- Login behaviour types --- */ |
| 120 | |
| 121 | enum { |
| 122 | l_preserve, /* Preserve the environment */ |
| 123 | l_user, /* Update who I am */ |
| 124 | l_login /* Do a full login */ |
| 125 | }; |
| 126 | |
| 127 | /*----- Static variables --------------------------------------------------*/ |
| 128 | |
| 129 | static sym_table bc__env; |
| 130 | |
| 131 | /*----- Main code ---------------------------------------------------------*/ |
| 132 | |
| 133 | /* --- @bc__write@ --- * |
| 134 | * |
| 135 | * Arguments: @FILE *fp@ = pointer to a stream to write on |
| 136 | * @const char *p@ = pointer to a string |
| 137 | * |
| 138 | * Returns: --- |
| 139 | * |
| 140 | * Use: Writes the string to the stream, substituting the program |
| 141 | * name (as returned by @quis@) for each occurrence of the |
| 142 | * character `$'. |
| 143 | */ |
| 144 | |
| 145 | static void bc__write(FILE *fp, const char *p) |
| 146 | { |
| 147 | const char *n = quis(); |
| 148 | size_t l; |
| 149 | size_t nl = strlen(n); |
| 150 | |
| 151 | /* --- Try to be a little efficient --- * |
| 152 | * |
| 153 | * Gather up non-`$' characters using @strcspn@ and spew them out really |
| 154 | * quickly. |
| 155 | */ |
| 156 | |
| 157 | for (;;) { |
| 158 | l = strcspn(p, "$"); |
| 159 | if (l) |
| 160 | fwrite(p, l, 1, fp); |
| 161 | p += l; |
| 162 | if (!*p) |
| 163 | break; |
| 164 | fwrite(n, nl, 1, fp); |
| 165 | p++; |
| 166 | } |
| 167 | } |
| 168 | |
| 169 | /* --- @bc__setenv@ --- * |
| 170 | * |
| 171 | * Arguments: @sym_env *e@ = pointer to environment variable block |
| 172 | * @const char *val@ = value to set |
| 173 | * |
| 174 | * Returns: --- |
| 175 | * |
| 176 | * Use: Sets an environment variable block to the right value. |
| 177 | */ |
| 178 | |
| 179 | static void bc__setenv(sym_env *e, const char *val) |
| 180 | { |
| 181 | e->val = xmalloc(strlen(e->_base.name) + 1 + strlen(val) + 1); |
| 182 | sprintf(e->val, "%s=%s", e->_base.name, val); |
| 183 | } |
| 184 | |
| 185 | /* --- @bc__putenv@ --- * |
| 186 | * |
| 187 | * Arguments: @const char *var@ = name of the variable to set, or 0 if |
| 188 | * this is embedded in the value string |
| 189 | * @const char *val@ = value to set, or 0 if the variable must |
| 190 | * be removed |
| 191 | * @unsigned int fl@ = flags to set |
| 192 | * @unsigned int force@ = force overwrite of preserved variables |
| 193 | * |
| 194 | * Returns: Pointer to symbol block, or zero if it was deleted. |
| 195 | * |
| 196 | * Use: Puts an item into the environment. |
| 197 | */ |
| 198 | |
| 199 | static sym_env *bc__putenv(const char *var, const char *val, |
| 200 | unsigned int fl, unsigned int force) |
| 201 | { |
| 202 | unsigned int f; |
| 203 | sym_env *e; |
| 204 | char *q = 0; |
| 205 | size_t sz; |
| 206 | |
| 207 | /* --- Sort out embedded variable names --- */ |
| 208 | |
| 209 | if (!var) { |
| 210 | const char *p = strchr(val, '='); |
| 211 | |
| 212 | if (p) { |
| 213 | sz = p - val; |
| 214 | q = xmalloc(sz + 1); |
| 215 | memcpy(q, val, sz); |
| 216 | q[sz] = 0; |
| 217 | var = q; |
| 218 | val = p + 1; |
| 219 | } else { |
| 220 | var = val; |
| 221 | val = 0; |
| 222 | } |
| 223 | } |
| 224 | |
| 225 | /* --- Find the variable block --- */ |
| 226 | |
| 227 | if (val) { |
| 228 | e = sym_find(&bc__env, var, -1, sizeof(*e), &f); |
| 229 | if (~e->f & envFlag_preserve || force) { |
| 230 | if (f) |
| 231 | free(e->val); |
| 232 | bc__setenv(e, val); |
| 233 | } |
| 234 | } else { |
| 235 | e = sym_find(&bc__env, var, -1, 0, 0); |
| 236 | if (e && (force || ~e->f & envFlag_preserve)) |
| 237 | sym_remove(&bc__env, e); |
| 238 | e = 0; |
| 239 | } |
| 240 | |
| 241 | /* --- Tidy up and return --- */ |
| 242 | |
| 243 | if (q) |
| 244 | free(q); |
| 245 | if (e) |
| 246 | e->f = fl; |
| 247 | return (e); |
| 248 | } |
| 249 | |
| 250 | /* --- @bc__banner@ --- * |
| 251 | * |
| 252 | * Arguments: @FILE *fp@ = stream to write on |
| 253 | * |
| 254 | * Returns: --- |
| 255 | * |
| 256 | * Use: Writes a banner containing copyright information. |
| 257 | */ |
| 258 | |
| 259 | static void bc__banner(FILE *fp) |
| 260 | { |
| 261 | bc__write(fp, "$ version " VERSION "\n"); |
| 262 | } |
| 263 | |
| 264 | /* --- @bc__usage@ --- * |
| 265 | * |
| 266 | * Arguments: @FILE *fp@ = stream to write on |
| 267 | * |
| 268 | * Returns: --- |
| 269 | * |
| 270 | * Use: Writes a terse reminder of command line syntax. |
| 271 | */ |
| 272 | |
| 273 | static void bc__usage(FILE *fp) |
| 274 | { |
| 275 | bc__write(fp, |
| 276 | "Usage: \n" |
| 277 | " $ -c <shell-command> <user>\n" |
| 278 | " $ [<env-var>] <user> [<command> [<arguments>]...]\n" |
| 279 | " $ -d [-p <port>] [-f <config-file>]\n"); |
| 280 | } |
| 281 | |
| 282 | /* --- @bc__help@ --- * |
| 283 | * |
| 284 | * Arguments: @FILE *fp@ = stream to write on |
| 285 | * @int suid@ = whether we're running set-uid |
| 286 | * |
| 287 | * Returns: --- |
| 288 | * |
| 289 | * Use: Displays a help message for this excellent piece of software. |
| 290 | */ |
| 291 | |
| 292 | static void bc__help(FILE *fp, int suid) |
| 293 | { |
| 294 | bc__banner(fp); |
| 295 | putc('\n', fp); |
| 296 | bc__usage(fp); |
| 297 | putc('\n', fp); |
| 298 | bc__write(fp, |
| 299 | "The `$' program allows you to run a process as another user.\n" |
| 300 | "If a command name is given, this is the process executed. If the `-c'\n" |
| 301 | "option is used, the process is assumed to be `/bin/sh'. If no command is\n" |
| 302 | "given, your default login shell is used.\n" |
| 303 | "\n" |
| 304 | "Your user id, the user id you wish to become, the name of the process\n" |
| 305 | "you wish to run, and the identity of the current host are looked up to\n" |
| 306 | "ensure that you have permission to do this.\n" |
| 307 | "\n" |
| 308 | "Note that logs are kept of all uses of this program.\n" |
| 309 | "\n" |
| 310 | "Options available are:\n" |
| 311 | "\n" |
| 312 | "-h, --help Display this help text\n" |
| 313 | "-u, --usage Display a short usage summary\n" |
| 314 | "-v, --version Display $'s version number\n" |
| 315 | "\n" |
| 316 | "-e, --preserve-environment Try to preserve the current environment\n" |
| 317 | "-s, --su, --set-user Set environment variables to reflect USER\n" |
| 318 | "-l, --login Really log in as USER\n" |
| 319 | "\n" |
| 320 | "-c CMD, --command=CMD Run the (Bourne) shell command CMD\n" |
| 321 | "\n" |
| 322 | "-d, --daemon Start a daemon\n" |
| 323 | "-p PORT, --port=PORT In daemon mode, listen on PORT\n" |
| 324 | "-f FILE, --config-file=FILE In daemon mode, read config from FILE\n"); |
| 325 | #ifdef TRACING |
| 326 | bc__write(fp, "\n"); |
| 327 | if (!suid) { |
| 328 | bc__write(fp, |
| 329 | "-I USER, --impersonate=USER Claim to be USER when asking the server\n"); |
| 330 | } |
| 331 | bc__write(fp, |
| 332 | "-T FILE, --trace=FILE Dump trace information to FILE (boring)\n" |
| 333 | "-L OPTS, --trace-level=OPTS Set level of tracing information\n"); |
| 334 | #endif |
| 335 | } |
| 336 | |
| 337 | /* --- @main@ --- * |
| 338 | * |
| 339 | * Arguments: @int argc@ = number of command line arguments |
| 340 | * @char *argv[]@ = pointer to the various arguments |
| 341 | * |
| 342 | * Returns: Zero if successful. |
| 343 | * |
| 344 | * Use: Allows a user to change UID. |
| 345 | */ |
| 346 | |
| 347 | int main(int argc, char *argv[]) |
| 348 | { |
| 349 | /* --- Request block setup parameters --- */ |
| 350 | |
| 351 | request rq; /* Request buffer to build */ |
| 352 | char *cmd = 0; /* Shell command to execute */ |
| 353 | char *binary = "/bin/sh"; /* Default binary to execute */ |
| 354 | char **env = environ; /* Default environment to pass */ |
| 355 | char **todo = 0; /* Pointer to argument list */ |
| 356 | char *who = 0; /* Who we're meant to become */ |
| 357 | struct passwd *from_pw = 0; /* User we are right now */ |
| 358 | struct passwd *to_pw = 0; /* User we want to become */ |
| 359 | |
| 360 | /* --- Become server setup parameters --- */ |
| 361 | |
| 362 | char *conffile = file_RULES; /* Default config file for daemon */ |
| 363 | int port = -1; /* Default port for daemon */ |
| 364 | |
| 365 | /* --- Miscellanous shared variables --- */ |
| 366 | |
| 367 | unsigned flags = 0; /* Various useful flags */ |
| 368 | int style = DEFAULT_LOGIN_STYLE; /* Login style */ |
| 369 | |
| 370 | /* --- Default argument list executes a shell command --- */ |
| 371 | |
| 372 | static char *shell[] = { |
| 373 | "/bin/sh", /* Bourne shell */ |
| 374 | "-c", /* Read from command line */ |
| 375 | 0, /* Pointer to shell command */ |
| 376 | 0 /* Terminator */ |
| 377 | }; |
| 378 | |
| 379 | /* --- Definitions for the various flags --- */ |
| 380 | |
| 381 | enum { |
| 382 | f_daemon = 1, /* Start up in daemon mode */ |
| 383 | f_duff = 2, /* Fault in arguments */ |
| 384 | f_login = 4, /* Execute as a login shell */ |
| 385 | f_dummy = 8, /* Don't actually do anything */ |
| 386 | f_setuid = 16 /* We're running setuid */ |
| 387 | }; |
| 388 | |
| 389 | /* --- Set up the program name --- */ |
| 390 | |
| 391 | ego(argv[0]); |
| 392 | clock(); |
| 393 | if (getuid() != geteuid()) |
| 394 | flags |= f_setuid; |
| 395 | |
| 396 | /* --- Read the environment into a hashtable --- */ |
| 397 | |
| 398 | { |
| 399 | char **p; |
| 400 | |
| 401 | sym_createTable(&bc__env); |
| 402 | for (p = environ; *p; p++) |
| 403 | bc__putenv(0, *p, 0, 0); |
| 404 | } |
| 405 | |
| 406 | /* --- Parse some command line arguments --- */ |
| 407 | |
| 408 | for (;;) { |
| 409 | int i; |
| 410 | static struct option opts[] = { |
| 411 | |
| 412 | /* --- Asking for help --- */ |
| 413 | |
| 414 | { "help", 0, 0, 'h' }, |
| 415 | { "usage", 0, 0, 'u' }, |
| 416 | { "version", 0, 0, 'v' }, |
| 417 | |
| 418 | /* --- Login style options --- */ |
| 419 | |
| 420 | { "preserve-environment", 0, 0, 'e' }, |
| 421 | { "su", 0, 0, 's' }, |
| 422 | { "set-user", 0, 0, 's' }, |
| 423 | { "login", 0, 0, 'l' }, |
| 424 | |
| 425 | /* --- Command to run options --- */ |
| 426 | |
| 427 | { "command", gFlag_argReq, 0, 'c' }, |
| 428 | |
| 429 | /* --- Server options --- */ |
| 430 | |
| 431 | { "daemon", 0, 0, 'd' }, |
| 432 | { "port", gFlag_argReq, 0, 'p' }, |
| 433 | { "config-file", gFlag_argReq, 0, 'f' }, |
| 434 | |
| 435 | /* --- Tracing options --- */ |
| 436 | |
| 437 | #ifdef TRACING |
| 438 | { "impersonate", gFlag_argReq, 0, 'I' }, |
| 439 | { "trace", gFlag_argOpt, 0, 'T' }, |
| 440 | { "trace-level", gFlag_argOpt, 0, 'L' }, |
| 441 | #endif |
| 442 | |
| 443 | { 0, 0, 0, 0 } |
| 444 | }; |
| 445 | |
| 446 | i = mdwopt(argc, argv, |
| 447 | "-" "huv" "esl" "c:" "dp:f:" T("I:T::L::"), |
| 448 | opts, 0, 0, gFlag_envVar); |
| 449 | if (i < 0) |
| 450 | goto done_options; |
| 451 | |
| 452 | switch (i) { |
| 453 | |
| 454 | /* --- Asking for help --- */ |
| 455 | |
| 456 | case 'h': |
| 457 | bc__help(stdout, flags & f_setuid); |
| 458 | exit(0); |
| 459 | break; |
| 460 | case 'u': |
| 461 | bc__usage(stdout); |
| 462 | exit(0); |
| 463 | break; |
| 464 | case 'v': |
| 465 | bc__banner(stdout); |
| 466 | exit(0); |
| 467 | break; |
| 468 | |
| 469 | /* --- Login style options --- */ |
| 470 | |
| 471 | case 'e': |
| 472 | style = l_preserve; |
| 473 | break; |
| 474 | case 's': |
| 475 | style = l_user; |
| 476 | break; |
| 477 | case 'l': |
| 478 | style = l_login; |
| 479 | break; |
| 480 | |
| 481 | /* --- Command to run options --- */ |
| 482 | |
| 483 | case 'c': |
| 484 | cmd = optarg; |
| 485 | break; |
| 486 | |
| 487 | /* --- Server options --- */ |
| 488 | |
| 489 | case 'p': |
| 490 | port = atoi(optarg); |
| 491 | break; |
| 492 | case 'd': |
| 493 | flags |= f_daemon; |
| 494 | break; |
| 495 | case 'f': |
| 496 | conffile = optarg; |
| 497 | break; |
| 498 | |
| 499 | /* --- Pretend to be a different user --- * |
| 500 | * |
| 501 | * There are all sorts of nasty implications for this option. Don't |
| 502 | * allow it if we're running setuid. Disable the actual login anyway. |
| 503 | */ |
| 504 | |
| 505 | #ifdef TRACING |
| 506 | |
| 507 | case 'I': |
| 508 | if (flags & f_setuid) |
| 509 | moan("shan't allow impersonation while running setuid"); |
| 510 | else { |
| 511 | struct passwd *pw; |
| 512 | if (isdigit((unsigned char)optarg[0])) |
| 513 | pw = getpwuid(atoi(optarg)); |
| 514 | else |
| 515 | pw = getpwnam(optarg); |
| 516 | if (!pw) |
| 517 | die("can't impersonate unknown user `%s'", optarg); |
| 518 | from_pw = userdb_copyUser(pw); |
| 519 | rq.from = from_pw->pw_uid; |
| 520 | flags |= f_dummy; |
| 521 | } |
| 522 | break; |
| 523 | |
| 524 | #endif |
| 525 | |
| 526 | /* --- Tracing support --- * |
| 527 | * |
| 528 | * Be careful not to zap a file I wouldn't normally be allowed to write |
| 529 | * to! |
| 530 | */ |
| 531 | |
| 532 | #ifdef TRACING |
| 533 | |
| 534 | case 'T': { |
| 535 | FILE *fp; |
| 536 | |
| 537 | if (optarg == 0 || strcmp(optarg, "-") == 0) |
| 538 | fp = stdout; |
| 539 | else { |
| 540 | uid_t eu = geteuid(), ru = getuid(); |
| 541 | |
| 542 | #ifdef HAVE_SETREUID |
| 543 | if (setreuid(eu, ru)) |
| 544 | #else |
| 545 | if (seteuid(ru)) |
| 546 | #endif |
| 547 | { |
| 548 | die("couldn't temporarily give up privileges: %s", |
| 549 | strerror(errno)); |
| 550 | } |
| 551 | |
| 552 | if ((fp = fopen(optarg, "w")) == 0) { |
| 553 | die("couldn't open trace file `%s' for writing: %s", |
| 554 | optarg, strerror(errno)); |
| 555 | } |
| 556 | |
| 557 | #ifdef HAVE_SETREUID |
| 558 | if (setreuid(ru, eu)) |
| 559 | #else |
| 560 | if (seteuid(eu)) |
| 561 | #endif |
| 562 | die("couldn't regain privileges: %s", strerror(errno)); |
| 563 | } |
| 564 | traceon(fp, TRACE_DFL); |
| 565 | trace(TRACE_MISC, "become: tracing enabled"); |
| 566 | } break; |
| 567 | |
| 568 | #endif |
| 569 | |
| 570 | /* --- Setting trace levels --- */ |
| 571 | |
| 572 | #ifdef TRACING |
| 573 | |
| 574 | case 'L': { |
| 575 | int sense = 1; |
| 576 | unsigned int lvl = 0, l; |
| 577 | const char *p = optarg; |
| 578 | |
| 579 | /* --- Table of tracing facilities --- */ |
| 580 | |
| 581 | typedef struct tr { |
| 582 | char ch; |
| 583 | unsigned int l; |
| 584 | const char *help; |
| 585 | } tr; |
| 586 | |
| 587 | static tr lvltbl[] = { |
| 588 | { 'm', TRACE_MISC, "miscellaneous messages" }, |
| 589 | { 's', TRACE_SETUP, "building the request block" }, |
| 590 | { 'd', TRACE_DAEMON, "server process" }, |
| 591 | { 'r', TRACE_RULE, "ruleset scanning" }, |
| 592 | { 'c', TRACE_CHECK, "request checking" }, |
| 593 | { 'l', TRACE_CLIENT, "client process" }, |
| 594 | { 'R', TRACE_RAND, "random number generator" }, |
| 595 | { 'C', TRACE_CRYPTO, "cryptographic processing of requests" }, |
| 596 | { 'y', TRACE_YACC, "parsing configuration file" }, |
| 597 | { 'D', TRACE_DFL, "default tracing options" }, |
| 598 | { 'A', TRACE_ALL, "all tracing options" }, |
| 599 | { 0, 0, 0 } |
| 600 | }; |
| 601 | tr *tp; |
| 602 | |
| 603 | /* --- Output some help if there's no arguemnt --- */ |
| 604 | |
| 605 | if (!optarg) { |
| 606 | bc__banner(stdout); |
| 607 | bc__write(stdout, |
| 608 | "\n" |
| 609 | "Tracing options:\n" |
| 610 | "\n"); |
| 611 | for (tp = lvltbl; tp->l; tp++) { |
| 612 | if ((flags & f_setuid) == 0 || tp->l & ~TRACE_PRIV) |
| 613 | printf("%c -- %s\n", tp->ch, tp->help); |
| 614 | } |
| 615 | bc__write(stdout, |
| 616 | "\n" |
| 617 | "Also, `+' and `-' options are recognised to turn on and off vavrious\n" |
| 618 | "tracing options. For example, `A-r' enables everything except ruleset\n" |
| 619 | "tracing, and `A-D+c' is everything except the defaults, but with request\n" |
| 620 | "check tracing.\n" |
| 621 | ); |
| 622 | exit(0); |
| 623 | } |
| 624 | |
| 625 | while (*p) { |
| 626 | if (*p == '+') |
| 627 | sense = 1; |
| 628 | else if (*p == '-') |
| 629 | sense = 0; |
| 630 | else { |
| 631 | for (tp = lvltbl; tp->l && *p != tp->ch; tp++) |
| 632 | ; |
| 633 | l = tp->l; |
| 634 | if (flags & f_setuid) |
| 635 | l &= ~TRACE_PRIV; |
| 636 | if (l) |
| 637 | lvl = sense ? (lvl | l) : (lvl & ~l); |
| 638 | else |
| 639 | moan("unknown trace option `%c'", *p); |
| 640 | } |
| 641 | p++; |
| 642 | } |
| 643 | |
| 644 | tracesetlvl(lvl); |
| 645 | yydebug = ((lvl & TRACE_YACC) != 0); |
| 646 | } break; |
| 647 | |
| 648 | #endif |
| 649 | |
| 650 | /* --- Something that wasn't an option --- * |
| 651 | * |
| 652 | * The following nasties are supported: |
| 653 | * |
| 654 | * * NAME=VALUE -- preserve NAME, and give it a VALUE |
| 655 | * * NAME= -- preserve NAME, and give it an empty value |
| 656 | * * NAME- -- delete NAME |
| 657 | * * NAME! -- preserve NAME with existing value |
| 658 | * |
| 659 | * Anything else is either the user name (which is OK) or the start of |
| 660 | * the command (in which case I stop and read the rest of the command). |
| 661 | */ |
| 662 | |
| 663 | case 0: { |
| 664 | size_t sz = strcspn(optarg, "=-!"); |
| 665 | sym_env *e; |
| 666 | |
| 667 | /* --- None of the above --- */ |
| 668 | |
| 669 | if (optarg[sz] == 0 || (optarg[sz] != '=' && optarg[sz + 1] != 0)) { |
| 670 | if (who == 0) |
| 671 | who = optarg; |
| 672 | else { |
| 673 | optind--; |
| 674 | goto done_options; |
| 675 | } |
| 676 | } |
| 677 | |
| 678 | /* --- Do the appropriate thing --- */ |
| 679 | |
| 680 | switch (optarg[sz]) { |
| 681 | case '=': |
| 682 | bc__putenv(0, optarg, envFlag_preserve, 1); |
| 683 | break; |
| 684 | case '-': |
| 685 | optarg[sz] = 0; |
| 686 | bc__putenv(optarg, 0, 0, 1); |
| 687 | break; |
| 688 | case '!': |
| 689 | optarg[sz] = 0; |
| 690 | if ((e = sym_find(&bc__env, optarg, -1, 0, 0)) != 0) |
| 691 | e->f |= envFlag_preserve; |
| 692 | break; |
| 693 | } |
| 694 | } break; |
| 695 | |
| 696 | /* --- Something I didn't understand has occurred --- */ |
| 697 | |
| 698 | case '?': |
| 699 | flags |= f_duff; |
| 700 | break; |
| 701 | } |
| 702 | } |
| 703 | |
| 704 | done_options: |
| 705 | if (flags & f_duff) { |
| 706 | bc__usage(stderr); |
| 707 | exit(1); |
| 708 | } |
| 709 | |
| 710 | /* --- Switch to daemon mode if requested --- */ |
| 711 | |
| 712 | if (flags & f_daemon) { |
| 713 | T( trace(TRACE_MISC, "become: daemon mode requested"); ) |
| 714 | daemon_init(conffile, port); |
| 715 | exit(0); |
| 716 | } |
| 717 | |
| 718 | /* --- Open a syslog --- */ |
| 719 | |
| 720 | openlog(quis(), 0, LOG_AUTH); |
| 721 | |
| 722 | /* --- Pick out the uid --- */ |
| 723 | |
| 724 | { |
| 725 | struct passwd *pw; |
| 726 | |
| 727 | if (!who) { |
| 728 | bc__usage(stderr); |
| 729 | exit(1); |
| 730 | } |
| 731 | |
| 732 | if (isdigit((unsigned char)who[0])) |
| 733 | pw = getpwuid(atoi(who)); |
| 734 | else |
| 735 | pw = getpwnam(who); |
| 736 | if (!pw) |
| 737 | die("unknown user `%s'", who); |
| 738 | to_pw = userdb_copyUser(pw); |
| 739 | rq.to = pw->pw_uid; |
| 740 | } |
| 741 | |
| 742 | /* --- Fill in the easy bits of the request --- */ |
| 743 | |
| 744 | if (!from_pw) { |
| 745 | struct passwd *pw; |
| 746 | |
| 747 | rq.from = getuid(); |
| 748 | pw = getpwuid(rq.from); |
| 749 | if (!pw) |
| 750 | die("who are you? (can't find user %li)", (long)rq.from); |
| 751 | from_pw = userdb_copyUser(pw); |
| 752 | } |
| 753 | |
| 754 | /* --- Find the local host address --- */ |
| 755 | |
| 756 | { |
| 757 | struct utsname u; |
| 758 | struct hostent *he; |
| 759 | uname(&u); |
| 760 | if ((he = gethostbyname(u.nodename)) == 0) |
| 761 | die("who am I? (can't resolve `%s')", u.nodename); |
| 762 | memcpy(&rq.host, he->h_addr, sizeof(struct in_addr)); |
| 763 | } |
| 764 | |
| 765 | /* --- Shell commands are easy --- */ |
| 766 | |
| 767 | if (cmd) { |
| 768 | shell[2] = cmd; |
| 769 | todo = shell; |
| 770 | } |
| 771 | |
| 772 | /* --- A command given on the command line isn't too hard --- */ |
| 773 | |
| 774 | else if (optind < argc) { |
| 775 | todo = argv + optind; |
| 776 | binary = todo[0]; |
| 777 | } |
| 778 | |
| 779 | else switch (style) { |
| 780 | |
| 781 | /* --- An unadorned becoming requires little work --- */ |
| 782 | |
| 783 | case l_preserve: |
| 784 | shell[0] = getenv("SHELL"); |
| 785 | if (!shell[0]) |
| 786 | shell[0] = from_pw->pw_shell; |
| 787 | shell[1] = 0; |
| 788 | todo = shell; |
| 789 | binary = todo[0]; |
| 790 | break; |
| 791 | |
| 792 | /* --- An su-like login needs slightly less effort --- */ |
| 793 | |
| 794 | case l_user: |
| 795 | shell[0] = to_pw->pw_shell; |
| 796 | shell[1] = 0; |
| 797 | todo = shell; |
| 798 | binary = todo[0]; |
| 799 | break; |
| 800 | |
| 801 | /* --- A login request needs a little bit of work --- */ |
| 802 | |
| 803 | case l_login: { |
| 804 | const char *p = strrchr(to_pw->pw_shell, '/'); |
| 805 | |
| 806 | if (p) |
| 807 | p++; |
| 808 | else |
| 809 | p = to_pw->pw_shell; |
| 810 | shell[0] = xmalloc(strlen(p) + 2); |
| 811 | shell[0][0] = '-'; |
| 812 | strcpy(shell[0] + 1, p); |
| 813 | shell[1] = 0; |
| 814 | todo = shell; |
| 815 | binary = to_pw->pw_shell; |
| 816 | chdir(to_pw->pw_dir); |
| 817 | } break; |
| 818 | } |
| 819 | |
| 820 | /* --- Mangle the environment --- * |
| 821 | * |
| 822 | * This keeps getting more complicated all the time. (How true. Now I've |
| 823 | * got all sorts of nasty environment mangling to do.) |
| 824 | * |
| 825 | * The environment stuff now happens in seven phases: |
| 826 | * |
| 827 | * 1. Mark very special variables to be preserved. Currently only TERM |
| 828 | * and DISPLAY are treated in this way. |
| 829 | * |
| 830 | * 2. Set and preserve Become's own environment variables. |
| 831 | * |
| 832 | * 3. Set and preserve the user identity variables (USER, LOGNAME, HOME, |
| 833 | * SHELL and MAIL) if we're being `su'-like or `login'-like. |
| 834 | * |
| 835 | * 4. If we're preserving the environment or being `su'-like, process the |
| 836 | * PATH variable a little. Otherwise reset it to something |
| 837 | * appropriate. |
| 838 | * |
| 839 | * 5. If we're being `login'-like, expunge all unpreserved variables. |
| 840 | * |
| 841 | * 6. Expunge any security-critical variables. |
| 842 | * |
| 843 | * 7. Build a new environment table to pass to child processes. |
| 844 | */ |
| 845 | |
| 846 | { |
| 847 | /* --- Variables to be preserved always --- * |
| 848 | * |
| 849 | * A user can explicitly expunge a variable in this list, in which case |
| 850 | * we never get to see it here. |
| 851 | */ |
| 852 | |
| 853 | static char *preserve[] = { |
| 854 | "TERM", "DISPLAY", 0 |
| 855 | }; |
| 856 | |
| 857 | /* --- Variables to be expunged --- * |
| 858 | * |
| 859 | * Any environment string which has one of the following as a prefix will |
| 860 | * be expunged from the environment passed to the called process. The |
| 861 | * first line lists variables which have been used to list search paths |
| 862 | * for shared libraries: by manipulating these, an attacker could replace |
| 863 | * a standard library with one of his own. The second line lists other |
| 864 | * well-known dangerous environment variables. |
| 865 | */ |
| 866 | |
| 867 | static char *banned[] = { |
| 868 | "-LD_", "SHLIB_PATH", "LIBPATH", "-_RLD_", |
| 869 | "IFS", "ENV", "BASH_ENV", "KRB_CONF", |
| 870 | 0 |
| 871 | }; |
| 872 | |
| 873 | /* --- Other useful variables --- */ |
| 874 | |
| 875 | sym_env *e; |
| 876 | char *p, *q, *r; |
| 877 | char **pp, **qq; |
| 878 | size_t sz; |
| 879 | unsigned f; |
| 880 | sym_iter i; |
| 881 | |
| 882 | /* --- Stage one. Preserve display-specific variables --- */ |
| 883 | |
| 884 | for (pp = preserve; *pp; pp++) { |
| 885 | if ((e = sym_find(&bc__env, *pp, -1, 0, 0)) != 0) |
| 886 | e->f |= envFlag_preserve; |
| 887 | } |
| 888 | |
| 889 | /* --- Stage two. Set Become's own variables --- */ |
| 890 | |
| 891 | e = sym_find(&bc__env, "BECOME_ORIGINAL_USER", -1, sizeof(*e), &f); |
| 892 | if (!f) |
| 893 | bc__setenv(e, from_pw->pw_name); |
| 894 | e->f |= envFlag_preserve; |
| 895 | |
| 896 | e = sym_find(&bc__env, "BECOME_ORIGINAL_HOME", -1, sizeof(*e), &f); |
| 897 | if (!f) |
| 898 | bc__setenv(e, from_pw->pw_dir); |
| 899 | e->f |= envFlag_preserve; |
| 900 | |
| 901 | bc__putenv("BECOME_OLD_USER", from_pw->pw_name, envFlag_preserve, 0); |
| 902 | bc__putenv("BECOME_OLD_HOME", from_pw->pw_dir, envFlag_preserve, 0); |
| 903 | bc__putenv("BECOME_USER", to_pw->pw_name, envFlag_preserve, 0); |
| 904 | bc__putenv("BECOME_HOME", to_pw->pw_dir, envFlag_preserve, 0); |
| 905 | |
| 906 | /* --- Stage three. Set user identity --- */ |
| 907 | |
| 908 | switch (style) { |
| 909 | case l_login: { |
| 910 | static char *maildirs[] = { |
| 911 | "/var/spool/mail", "/var/mail", |
| 912 | "/usr/spool/mail", "/usr/mail", |
| 913 | 0 |
| 914 | }; |
| 915 | struct stat s; |
| 916 | char b[128]; |
| 917 | |
| 918 | for (pp = maildirs; *pp; pp++) { |
| 919 | if (stat(*pp, &s) == 0 && S_ISDIR(s.st_mode)) { |
| 920 | sprintf(b, "%s/%s", *pp, to_pw->pw_name); |
| 921 | bc__putenv("MAIL", b, envFlag_preserve, 0); |
| 922 | break; |
| 923 | } |
| 924 | } |
| 925 | } /* Fall through */ |
| 926 | |
| 927 | case l_user: |
| 928 | bc__putenv("USER", to_pw->pw_name, envFlag_preserve, 0); |
| 929 | bc__putenv("LOGNAME", to_pw->pw_name, envFlag_preserve, 0); |
| 930 | bc__putenv("HOME", to_pw->pw_dir, envFlag_preserve, 0); |
| 931 | bc__putenv("SHELL", to_pw->pw_shell, envFlag_preserve, 0); |
| 932 | break; |
| 933 | } |
| 934 | |
| 935 | /* --- Stage four. Set the user's PATH properly --- */ |
| 936 | |
| 937 | { |
| 938 | /* --- Find an existing path --- * |
| 939 | * |
| 940 | * If there's no path, or this is a login, then set a default path, |
| 941 | * unless we're meant to preserve the existing one. Whew! |
| 942 | */ |
| 943 | |
| 944 | e = sym_find(&bc__env, "PATH", -1, sizeof(*e), &f); |
| 945 | |
| 946 | if (!f || (style == l_login && ~e->f & envFlag_preserve)) { |
| 947 | bc__putenv("PATH", |
| 948 | rq.to ? "/usr/bin:/bin" : "/usr/bin:/usr/sbin:/bin:/sbin", |
| 949 | envFlag_preserve, 0); |
| 950 | } else { |
| 951 | |
| 952 | /* --- Find the string --- */ |
| 953 | |
| 954 | e->f = envFlag_preserve; |
| 955 | p = strchr(e->val, '=') + 1; |
| 956 | r = e->val; |
| 957 | |
| 958 | /* --- Write the new version to a dynamically allocated buffer --- */ |
| 959 | |
| 960 | e->val = xmalloc(4 + 1 + strlen(p) + 1); |
| 961 | strcpy(e->val, "PATH="); |
| 962 | q = e->val + 5; |
| 963 | |
| 964 | for (p = strtok(p, ":"); p; p = strtok(0, ":")) { |
| 965 | if (p[0] == '.') |
| 966 | continue; |
| 967 | while (*p) |
| 968 | *q++ = *p++; |
| 969 | *q++ = ':'; |
| 970 | } |
| 971 | q[-1] = 0; |
| 972 | |
| 973 | /* --- Done! --- */ |
| 974 | |
| 975 | free(r); |
| 976 | } |
| 977 | } |
| 978 | |
| 979 | /* --- Stages five and six. Expunge variables and count numbers --- * |
| 980 | * |
| 981 | * Folded together, so I only need one pass through the table. Also |
| 982 | * count the number of variables needed at this time. |
| 983 | */ |
| 984 | |
| 985 | sz = 0; |
| 986 | |
| 987 | for (sym_createIter(&i, &bc__env); (e = sym_next(&i)) != 0; ) { |
| 988 | |
| 989 | /* --- Login style expunges all unpreserved variables --- */ |
| 990 | |
| 991 | if (style == l_login && ~e->f & envFlag_preserve) |
| 992 | goto expunge; |
| 993 | |
| 994 | /* --- Otherwise just check the name against the list --- */ |
| 995 | |
| 996 | for (pp = banned; *pp; pp++) { |
| 997 | if (**pp == '-') { |
| 998 | p = *pp + 1; |
| 999 | if (memcmp(e->_base.name, p, strlen(p)) == 0) |
| 1000 | goto expunge; |
| 1001 | } else if (strcmp(e->_base.name, p) == 0) |
| 1002 | goto expunge; |
| 1003 | } |
| 1004 | |
| 1005 | sz++; |
| 1006 | continue; |
| 1007 | |
| 1008 | expunge: |
| 1009 | sym_remove(&bc__env, e); |
| 1010 | } |
| 1011 | |
| 1012 | /* --- Stage seven. Build the new environment block --- */ |
| 1013 | |
| 1014 | env = qq = xmalloc((sz + 1) * sizeof(*qq)); |
| 1015 | |
| 1016 | for (sym_createIter(&i, &bc__env); (e = sym_next(&i)) != 0; ) |
| 1017 | *qq++ = e->val; |
| 1018 | *qq++ = 0; |
| 1019 | } |
| 1020 | |
| 1021 | /* --- Trace the command --- */ |
| 1022 | |
| 1023 | IF_TRACING(TRACE_SETUP, { |
| 1024 | int i; |
| 1025 | |
| 1026 | trace(TRACE_SETUP, "setup: from user %s to user %s", |
| 1027 | from_pw->pw_name, to_pw->pw_name); |
| 1028 | trace(TRACE_SETUP, "setup: binary == `%s'", binary); |
| 1029 | for (i = 0; todo[i]; i++) |
| 1030 | trace(TRACE_SETUP, "setup: arg %i == `%s'", i, todo[i]); |
| 1031 | for (i = 0; env[i]; i++) |
| 1032 | trace(TRACE_SETUP, "setup: env %i == `%s'", i, env[i]); |
| 1033 | }) |
| 1034 | |
| 1035 | /* --- If necessary, resolve the path to the command --- */ |
| 1036 | |
| 1037 | if (!strchr(binary, '/')) { |
| 1038 | char *path, *p; |
| 1039 | struct stat st; |
| 1040 | |
| 1041 | if ((p = getenv("PATH")) == 0) |
| 1042 | p = "/bin:/usr/bin"; |
| 1043 | path = xstrdup(p); |
| 1044 | |
| 1045 | for (p = strtok(path, ":"); p; p = strtok(0, ":")) { |
| 1046 | |
| 1047 | /* --- Check length of string before copying --- */ |
| 1048 | |
| 1049 | if (strlen(p) + strlen(binary) + 2 > sizeof(rq.cmd)) |
| 1050 | continue; |
| 1051 | |
| 1052 | /* --- Now build the pathname and check it --- */ |
| 1053 | |
| 1054 | sprintf(rq.cmd, "%s/%s", p, todo[0]); |
| 1055 | if (stat(rq.cmd, &st) == 0 && /* Check it exists */ |
| 1056 | st.st_mode & 0111 && /* Check it's executable */ |
| 1057 | S_ISREG(st.st_mode)) /* Check it's a file */ |
| 1058 | break; |
| 1059 | } |
| 1060 | |
| 1061 | if (!p) |
| 1062 | die("couldn't find `%s' in path", todo[0]); |
| 1063 | binary = rq.cmd; |
| 1064 | free(path); |
| 1065 | } |
| 1066 | T( trace(TRACE_SETUP, "setup: resolve binary to `%s'", binary); ) |
| 1067 | |
| 1068 | /* --- Canonicalise the path string, if necessary --- */ |
| 1069 | |
| 1070 | { |
| 1071 | char b[CMDLEN_MAX]; |
| 1072 | char *p; |
| 1073 | const char *q; |
| 1074 | |
| 1075 | /* --- Insert current directory name if path not absolute --- */ |
| 1076 | |
| 1077 | p = b; |
| 1078 | q = binary; |
| 1079 | if (*q != '/') { |
| 1080 | if (!getcwd(b, sizeof(b))) |
| 1081 | die("couldn't read current directory: %s", strerror(errno)); |
| 1082 | p += strlen(p); |
| 1083 | *p++ = '/'; |
| 1084 | } |
| 1085 | |
| 1086 | /* --- Now copy over characters from the path string --- */ |
| 1087 | |
| 1088 | while (*q) { |
| 1089 | |
| 1090 | /* --- Check for buffer overflows here --- * |
| 1091 | * |
| 1092 | * I write at most one byte per iteration so this is OK. Remember to |
| 1093 | * allow one for the null byte. |
| 1094 | */ |
| 1095 | |
| 1096 | if (p >= b + sizeof(b) - 1) |
| 1097 | die("internal error: buffer overflow while canonifying path"); |
| 1098 | |
| 1099 | /* --- Reduce multiple slashes to just one --- */ |
| 1100 | |
| 1101 | if (*q == '/') { |
| 1102 | while (*q == '/') |
| 1103 | q++; |
| 1104 | *p++ = '/'; |
| 1105 | } |
| 1106 | |
| 1107 | /* --- Handle dots in filenames --- * |
| 1108 | * |
| 1109 | * @p[-1]@ is valid here, because if @*q@ is not a `/' then either |
| 1110 | * we've just stuck the current directory on the end of the buffer, |
| 1111 | * or we've just put something else on the end. |
| 1112 | */ |
| 1113 | |
| 1114 | else if (*q == '.' && p[-1] == '/') { |
| 1115 | |
| 1116 | /* --- A simple `./' just gets removed --- */ |
| 1117 | |
| 1118 | if (q[1] == 0 || q[1] == '/') { |
| 1119 | q++; |
| 1120 | p--; |
| 1121 | continue; |
| 1122 | } |
| 1123 | |
| 1124 | /* --- A `../' needs to be peeled back to the previous `/' --- */ |
| 1125 | |
| 1126 | if (q[1] == '.' && (q[2] == 0 || q[2] == '/')) { |
| 1127 | q += 2; |
| 1128 | p--; |
| 1129 | while (p > b && p[-1] != '/') |
| 1130 | p--; |
| 1131 | if (p > b) |
| 1132 | p--; |
| 1133 | continue; |
| 1134 | } |
| 1135 | } else |
| 1136 | *p++ = *q++; |
| 1137 | } |
| 1138 | |
| 1139 | *p++ = 0; |
| 1140 | strcpy(rq.cmd, b); |
| 1141 | } |
| 1142 | T( trace(TRACE_SETUP, "setup: canonify binary to `%s'", rq.cmd); ) |
| 1143 | |
| 1144 | /* --- Run the check --- * |
| 1145 | * |
| 1146 | * If the user is already what she wants to be, then print a warning. |
| 1147 | * Then, if I was just going to spawn a shell, quit, to reduce user |
| 1148 | * confusion. Otherwise, do what was wanted anyway. |
| 1149 | */ |
| 1150 | |
| 1151 | if (rq.from == rq.to) { |
| 1152 | moan("you already are `%s'!", to_pw->pw_name); |
| 1153 | if (!cmd && todo == shell) { |
| 1154 | moan("(to prevent confusion, I'm not spawning a shell)"); |
| 1155 | exit(0); |
| 1156 | } |
| 1157 | } else { |
| 1158 | int a = check(&rq); |
| 1159 | |
| 1160 | syslog(LOG_INFO, |
| 1161 | "permission %s for %s to become %s to run `%s'", |
| 1162 | a ? "granted" : "denied", from_pw->pw_name, to_pw->pw_name, |
| 1163 | rq.cmd); |
| 1164 | |
| 1165 | if (!a) |
| 1166 | die("permission denied"); |
| 1167 | } |
| 1168 | |
| 1169 | /* --- Now do the job --- */ |
| 1170 | |
| 1171 | T( trace(TRACE_MISC, "become: permission granted"); ) |
| 1172 | |
| 1173 | if (flags & f_dummy) { |
| 1174 | puts("permission granted"); |
| 1175 | return (0); |
| 1176 | } else { |
| 1177 | if (setuid(rq.to) == -1) |
| 1178 | die("couldn't set uid: %s", strerror(errno)); |
| 1179 | fflush(0); |
| 1180 | execve(rq.cmd, todo, env); |
| 1181 | die("couldn't exec `%s': %s", rq.cmd, strerror(errno)); |
| 1182 | return (127); |
| 1183 | } |
| 1184 | } |
| 1185 | |
| 1186 | /*----- That's all, folks -------------------------------------------------*/ |