| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: daemon.c,v 1.17 2004/04/08 01:36:20 mdw Exp $ |
| 4 | * |
| 5 | * Running a `become' daemon |
| 6 | * |
| 7 | * (c) 1998 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 | /*----- Header files ------------------------------------------------------*/ |
| 30 | |
| 31 | /* --- ANSI headers --- */ |
| 32 | |
| 33 | #include <errno.h> |
| 34 | #include <signal.h> |
| 35 | #include <stdio.h> |
| 36 | #include <stdlib.h> |
| 37 | #include <string.h> |
| 38 | |
| 39 | /* --- Unix headers --- */ |
| 40 | |
| 41 | #include <sys/types.h> |
| 42 | #include <sys/time.h> |
| 43 | #include <sys/socket.h> |
| 44 | |
| 45 | #include <netinet/in.h> |
| 46 | |
| 47 | #include <arpa/inet.h> |
| 48 | |
| 49 | #include <netdb.h> |
| 50 | #include <syslog.h> |
| 51 | #include <unistd.h> |
| 52 | |
| 53 | /* --- mLib headers --- */ |
| 54 | |
| 55 | #include <mLib/fwatch.h> |
| 56 | #include <mLib/quis.h> |
| 57 | #include <mLib/report.h> |
| 58 | #include <mLib/sel.h> |
| 59 | #include <mLib/sig.h> |
| 60 | #include <mLib/sym.h> |
| 61 | #include <mLib/trace.h> |
| 62 | |
| 63 | /* --- Catacomb headers --- */ |
| 64 | |
| 65 | #include <catacomb/buf.h> |
| 66 | #include <catacomb/dsa.h> |
| 67 | #include <catacomb/key.h> |
| 68 | #include <catacomb/mp.h> |
| 69 | #include <catacomb/noise.h> |
| 70 | #include <catacomb/paranoia.h> |
| 71 | #include <catacomb/rand.h> |
| 72 | #include <catacomb/sha.h> |
| 73 | |
| 74 | /* --- Local headers --- */ |
| 75 | |
| 76 | #include "become.h" |
| 77 | #include "config.h" |
| 78 | #include "daemon.h" |
| 79 | #include "lexer.h" |
| 80 | #include "name.h" |
| 81 | #include "netg.h" |
| 82 | #include "parse.h" |
| 83 | #include "rule.h" |
| 84 | #include "userdb.h" |
| 85 | |
| 86 | /*----- Arbitrary constants -----------------------------------------------*/ |
| 87 | |
| 88 | #define daemon__awakeEvery (10) /* Awaken this often to rescan */ |
| 89 | |
| 90 | /*----- Static variables --------------------------------------------------*/ |
| 91 | |
| 92 | static int daemon__port = -1; /* No particular port yet */ |
| 93 | static fwatch daemon__cwatch, daemon__kwatch; /* Watching key/config files */ |
| 94 | static sel_timer daemon__timer; /* Timer for reading */ |
| 95 | static sel_state daemon__sel; /* Select context */ |
| 96 | static sel_file daemon__listen; /* Listening socket selector */ |
| 97 | static const char *daemon__config; /* Configuration file for daemon */ |
| 98 | static const char *daemon__keyfile; /* Keyring file for daemon */ |
| 99 | static dsa_priv daemon__key; /* The key data */ |
| 100 | |
| 101 | /*----- Main code ---------------------------------------------------------*/ |
| 102 | |
| 103 | /* --- @daemon_usePort@ --- * |
| 104 | * |
| 105 | * Arguments: @int port@ = port to use, please |
| 106 | * |
| 107 | * Returns: --- |
| 108 | * |
| 109 | * Use: Instructs the daemon to listen to the given port. |
| 110 | */ |
| 111 | |
| 112 | void daemon_usePort(int port) |
| 113 | { |
| 114 | daemon__port = port; |
| 115 | } |
| 116 | |
| 117 | /* --- @daemon__moan@ --- * |
| 118 | * |
| 119 | * Arguments: @const char *f@ = offending file name |
| 120 | * @int line@ = offending line of the file |
| 121 | * @const char *msg@ = message |
| 122 | * @void *p@ = ignored |
| 123 | * |
| 124 | * Returns: --- |
| 125 | * |
| 126 | * Use: Reports an error message about a key file. |
| 127 | */ |
| 128 | |
| 129 | static void daemon__moan(const char *f, int line, const char *msg, void *p) |
| 130 | { |
| 131 | syslog(LOG_ERR, "key file error: %s: %d: %s", f, line, msg); |
| 132 | T( trace(TRACE_DAEMON, "daemon: key file error: %s: %d: %s", |
| 133 | f, line, msg); ) |
| 134 | } |
| 135 | |
| 136 | /* --- @daemon_readKey@ --- * |
| 137 | * |
| 138 | * Arguments: @const char *kf@ = pointer to key file name to use |
| 139 | * |
| 140 | * Returns: --- |
| 141 | * |
| 142 | * Use: Loads the private key from the key file. |
| 143 | */ |
| 144 | |
| 145 | void daemon_readKey(const char *kf) |
| 146 | { |
| 147 | key_packstruct kps[DSA_PRIVFETCHSZ]; |
| 148 | key_packdef *kp; |
| 149 | key_file f; |
| 150 | key *k; |
| 151 | int err; |
| 152 | |
| 153 | if (daemon__keyfile) |
| 154 | return; |
| 155 | T( trace(TRACE_DAEMON, "daemon: reading key from `%s'", kf); ) |
| 156 | if (key_open(&f, kf, KOPEN_READ, daemon__moan, 0)) |
| 157 | return; |
| 158 | kp = key_fetchinit(dsa_privfetch, kps, &daemon__key); |
| 159 | if ((k = key_bytype(&f, "become-dsa")) == 0) |
| 160 | err = KERR_NOTFOUND; |
| 161 | else |
| 162 | err = key_fetch(kp, k); |
| 163 | if (err) |
| 164 | syslog(LOG_ERR, "couldn't load key: %s", key_strerror(err)); |
| 165 | else { |
| 166 | mp_copy(daemon__key.dp.p); |
| 167 | mp_copy(daemon__key.dp.q); |
| 168 | mp_copy(daemon__key.dp.g); |
| 169 | mp_copy(daemon__key.x); |
| 170 | mp_copy(daemon__key.y); |
| 171 | daemon__keyfile = kf; |
| 172 | } |
| 173 | key_fetchdone(kp); |
| 174 | key_close(&f); |
| 175 | } |
| 176 | |
| 177 | /* --- @daemon__readConfig@ --- * |
| 178 | * |
| 179 | * Arguments: @const char *cf@ = pointer to configuration file to use |
| 180 | * |
| 181 | * Returns: Zero if it worked, nonzero if it hurt... |
| 182 | * |
| 183 | * Use: Reads the configuration file, and other things. |
| 184 | */ |
| 185 | |
| 186 | static int daemon__readConfig(const char *cf) |
| 187 | { |
| 188 | FILE *fp; |
| 189 | |
| 190 | daemon__keyfile = 0; |
| 191 | if ((fp = fopen(cf, "r")) == 0) |
| 192 | return (-1); |
| 193 | lexer_scan(fp); |
| 194 | parse(); |
| 195 | fclose(fp); |
| 196 | if (!daemon__keyfile) |
| 197 | daemon_readKey(file_KEY); |
| 198 | T( trace(TRACE_DAEMON, "daemon: read config file"); ) |
| 199 | return (0); |
| 200 | } |
| 201 | |
| 202 | /* --- @daemon__read@ --- * |
| 203 | * |
| 204 | * Arguments: @int fd@ = socket handle |
| 205 | * @unsigned mode@ = ignored |
| 206 | * @void *p@ = ignored |
| 207 | * |
| 208 | * Returns: --- |
| 209 | * |
| 210 | * Use: Examines a buffer, and returns a response. |
| 211 | */ |
| 212 | |
| 213 | void daemon__read(int fd, unsigned mode, void *p) |
| 214 | { |
| 215 | unsigned char buff[65536]; /* Buffer for incoming packets */ |
| 216 | struct sockaddr_in sin; /* Address of packet sender */ |
| 217 | char sender[64]; /* Sender's hostname (resolved) */ |
| 218 | octet h[SHA_HASHSZ]; /* Hash of the transmission buffer */ |
| 219 | sha_ctx hc; /* Hashing context */ |
| 220 | request rq; /* Request buffer for verification */ |
| 221 | ssize_t sz; /* Length of incoming message */ |
| 222 | socklen_t slen; /* Length of incoming address */ |
| 223 | uint32 u; /* Scratch integer */ |
| 224 | uint16 ul; /* And another */ |
| 225 | struct hostent *he; /* Resolve structure */ |
| 226 | mp *m, *k, *r, *s; /* Integers for signing */ |
| 227 | int ans; /* Answer from the check */ |
| 228 | buf b; /* Buffer for parsing request */ |
| 229 | |
| 230 | /* --- Kick some randomness in the pot --- */ |
| 231 | |
| 232 | noise_timer(RAND_GLOBAL); |
| 233 | |
| 234 | /* --- Read the message --- */ |
| 235 | |
| 236 | slen = sizeof(sin); |
| 237 | if ((sz = recvfrom(fd, (char *)buff, sizeof(buff), 0, |
| 238 | (struct sockaddr *)&sin, &slen)) < 0) { |
| 239 | T( trace(TRACE_DAEMON, "daemon: error reading packet: %s", |
| 240 | strerror(errno)); ) |
| 241 | syslog(LOG_INFO, "duff packet received: %e"); |
| 242 | return; |
| 243 | } |
| 244 | |
| 245 | /* --- Resolve the host name --- */ |
| 246 | |
| 247 | he = gethostbyaddr((char *)&sin.sin_addr, sizeof(sin.sin_addr), AF_INET); |
| 248 | sender[0] = 0; |
| 249 | strncat(sender, he ? he->h_name : inet_ntoa(sin.sin_addr), |
| 250 | sizeof(sender) - 1); |
| 251 | syslog(LOG_DEBUG, "packet received from %s", sender); |
| 252 | T( trace(TRACE_DAEMON, "daemon: received request from %s", sender); ) |
| 253 | |
| 254 | /* --- Sanity check --- */ |
| 255 | |
| 256 | if (!daemon__keyfile) { |
| 257 | syslog(LOG_NOTICE, "no key file: ignoring request"); |
| 258 | T( trace(TRACE_DAEMON, "daemon: no key file: ignoring request"); ) |
| 259 | return; |
| 260 | } |
| 261 | |
| 262 | /* --- Unpack the block --- */ |
| 263 | |
| 264 | rq.host = sin.sin_addr; |
| 265 | buf_init(&b, buff, sz); |
| 266 | if (buf_ensure(&b, SHA_HASHSZ)) goto fail; BSTEP(&b, SHA_HASHSZ); |
| 267 | if (buf_getu32(&b, &u)) goto fail; rq.from = u; |
| 268 | if (buf_getu32(&b, &u)) goto fail; rq.to = u; |
| 269 | if (buf_getu16(&b, &ul) || buf_ensure(&b, ul) || ul >= sizeof(rq.cmd)) |
| 270 | goto fail; |
| 271 | memcpy(rq.cmd, BCUR(&b), ul); |
| 272 | rq.cmd[ul] = 0; |
| 273 | BSTEP(&b, ul); |
| 274 | if (BLEFT(&b)) goto fail; |
| 275 | |
| 276 | /* --- Hash the request block --- */ |
| 277 | |
| 278 | sha_init(&hc); |
| 279 | sha_hash(&hc, buff, sz); |
| 280 | sha_done(&hc, h); |
| 281 | |
| 282 | /* --- Build a reply block --- */ |
| 283 | |
| 284 | ans = rule_check(&rq); |
| 285 | syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s", |
| 286 | sender, rq.from, rq.to, rq.cmd, ans ? "granted" : "denied"); |
| 287 | buf_init(&b, buff, sizeof(buff)); |
| 288 | if (buf_put(&b, h, sizeof(h)) || buf_putbyte(&b, ans)) |
| 289 | goto fail; |
| 290 | |
| 291 | /* --- Sign the reply block --- */ |
| 292 | |
| 293 | sha_init(&hc); |
| 294 | sha_hash(&hc, BBASE(&b), BLEN(&b)); |
| 295 | sha_done(&hc, h); |
| 296 | m = mp_loadb(MP_NEW, h, sizeof(h)); |
| 297 | rand_get(RAND_GLOBAL, h, sizeof(h)); |
| 298 | k = mp_loadb(MP_NEWSEC, h, sizeof(h)); |
| 299 | r = s = MP_NEW; |
| 300 | dsa_mksig(&daemon__key.dp, daemon__key.x, m, k, &r, &s); |
| 301 | buf_putmp(&b, r); |
| 302 | buf_putmp(&b, s); |
| 303 | mp_drop(m); |
| 304 | mp_drop(k); |
| 305 | mp_drop(r); |
| 306 | mp_drop(s); |
| 307 | if (BBAD(&b)) |
| 308 | goto fail; |
| 309 | |
| 310 | /* --- Send the reply off --- */ |
| 311 | |
| 312 | sendto(fd, BBASE(&b), BLEN(&b), 0, (struct sockaddr *)&sin, sizeof(sin)); |
| 313 | T( trace(TRACE_DAEMON, "daemon: reply sent"); ) |
| 314 | return; |
| 315 | |
| 316 | fail: |
| 317 | syslog(LOG_ERR, "couldn't respond to query"); |
| 318 | T( trace(TRACE_DAEMON, "daemon: failed to answer query"); ) |
| 319 | } |
| 320 | |
| 321 | /* --- @daemon__die@ --- * |
| 322 | * |
| 323 | * Arguments: @int n@ = signal number |
| 324 | * @void *p@ = ignored |
| 325 | * |
| 326 | * Returns: Doesn't. |
| 327 | * |
| 328 | * Use: Exits the daemon. |
| 329 | */ |
| 330 | |
| 331 | static void daemon__die(int n, void *p) |
| 332 | { |
| 333 | T( trace(TRACE_DAEMON, "daemon: killed by signal %i", n); ) |
| 334 | syslog(LOG_NOTICE, "killed by signal type %i", n); |
| 335 | remove(file_PID); |
| 336 | exit(0); |
| 337 | } |
| 338 | |
| 339 | /* --- @daemon__setTimer@ --- * |
| 340 | * |
| 341 | * Arguments: --- |
| 342 | * |
| 343 | * Returns: --- |
| 344 | * |
| 345 | * Use: Sets the interval timer up. |
| 346 | */ |
| 347 | |
| 348 | static void daemon__wakeUp(struct timeval *tv, void *p); |
| 349 | |
| 350 | static void daemon__setTimer(void) |
| 351 | { |
| 352 | struct timeval tv; |
| 353 | |
| 354 | gettimeofday(&tv, 0); |
| 355 | tv.tv_sec += daemon__awakeEvery; |
| 356 | sel_addtimer(&daemon__sel, &daemon__timer, &tv, daemon__wakeUp, 0); |
| 357 | } |
| 358 | |
| 359 | /* --- @daemon__rescan@ --- * |
| 360 | * |
| 361 | * Arguments: @int n@ = signal number |
| 362 | * @void *p@ = ignored |
| 363 | * |
| 364 | * Returns: --- |
| 365 | * |
| 366 | * Use: Forces a rescan of the daemon's configuration. |
| 367 | */ |
| 368 | |
| 369 | static void daemon__rescan(int n, void *p) |
| 370 | { |
| 371 | syslog(LOG_INFO, "rescanning configuration file"); |
| 372 | name_end(); |
| 373 | rule_end(); |
| 374 | netg_end(); |
| 375 | userdb_end(); |
| 376 | dsa_privfree(&daemon__key); |
| 377 | userdb_init(); |
| 378 | userdb_local(); |
| 379 | userdb_yp(); |
| 380 | netg_init(); |
| 381 | rule_init(); |
| 382 | name_init(); |
| 383 | if (daemon__readConfig(daemon__config)) |
| 384 | syslog(LOG_ERR, "error reading configuration file"); |
| 385 | sel_rmtimer(&daemon__timer); |
| 386 | daemon__setTimer(); |
| 387 | fwatch_update(&daemon__cwatch, daemon__config); |
| 388 | fwatch_update(&daemon__kwatch, daemon__keyfile); |
| 389 | } |
| 390 | |
| 391 | /* --- @daemon__wakeUp@ --- * |
| 392 | * |
| 393 | * Arguments: @struct timeval *tv@ = ignored |
| 394 | * @void *p@ = ignored |
| 395 | * |
| 396 | * Returns: --- |
| 397 | * |
| 398 | * Use: Wakes up periodically to check the configuration file. |
| 399 | */ |
| 400 | |
| 401 | static void daemon__wakeUp(struct timeval *tv, void *p) |
| 402 | { |
| 403 | T( trace(TRACE_DAEMON, "daemon: interval timer"); ) |
| 404 | rand_seed(RAND_GLOBAL, 160); |
| 405 | daemon__setTimer(); |
| 406 | if (fwatch_update(&daemon__cwatch, daemon__config)) |
| 407 | daemon__rescan(0, 0); |
| 408 | else if (fwatch_update(&daemon__kwatch, daemon__keyfile)) { |
| 409 | const char *kf = daemon__keyfile; |
| 410 | daemon__keyfile = 0; |
| 411 | daemon_readKey(kf); |
| 412 | } |
| 413 | } |
| 414 | |
| 415 | /* --- @daemon_init@ --- * |
| 416 | * |
| 417 | * Arguments: @const char *cf@ = pointer to name of configuration file |
| 418 | * @int port@ = port to listen to, or %$-1$% for default |
| 419 | * @unsigned f@ = various flags |
| 420 | * |
| 421 | * Returns: Never. |
| 422 | * |
| 423 | * Use: Starts `become' up in daemon mode. |
| 424 | */ |
| 425 | |
| 426 | void daemon_init(const char *cf, int port, unsigned f) |
| 427 | { |
| 428 | int s; |
| 429 | int i; |
| 430 | |
| 431 | static struct sigvec { |
| 432 | int sig; |
| 433 | void (*proc)(int n, void *p); |
| 434 | sig s; |
| 435 | } sigs[] = { |
| 436 | { SIGHUP, daemon__rescan }, |
| 437 | { SIGINT, daemon__die }, |
| 438 | { SIGTERM, daemon__die }, |
| 439 | { SIGQUIT, daemon__die }, |
| 440 | { 0, 0 } |
| 441 | }; |
| 442 | |
| 443 | /* --- Remove my root privileges --- * |
| 444 | * |
| 445 | * Just in case there's anything dodgy in my configuration file, or the |
| 446 | * user wants me to start on a funny port. |
| 447 | */ |
| 448 | |
| 449 | setuid(getuid()); |
| 450 | |
| 451 | /* --- Initialize the random number generator --- */ |
| 452 | |
| 453 | rand_noisesrc(RAND_GLOBAL, &noise_source); |
| 454 | rand_seed(RAND_GLOBAL, 160); |
| 455 | |
| 456 | /* --- Initialise bits of the program --- */ |
| 457 | |
| 458 | daemon__config = cf; |
| 459 | daemon__port = port; |
| 460 | sel_init(&daemon__sel); |
| 461 | sig_init(&daemon__sel); |
| 462 | userdb_init(); |
| 463 | userdb_local(); |
| 464 | userdb_yp(); |
| 465 | netg_init(); |
| 466 | name_init(); |
| 467 | rule_init(); |
| 468 | openlog(quis(), 0, LOG_DAEMON); |
| 469 | syslog(LOG_NOTICE, "starting up"); |
| 470 | |
| 471 | if (daemon__readConfig(daemon__config)) |
| 472 | die(1, "couldn't read configuration file"); |
| 473 | fwatch_init(&daemon__cwatch, daemon__config); |
| 474 | fwatch_init(&daemon__kwatch, daemon__keyfile); |
| 475 | |
| 476 | /* --- Decide on a port to use --- * |
| 477 | * |
| 478 | * If I don't have a port yet (e.g., from the configuration file) then |
| 479 | * look it up in /etc/services under whatever name I was started as. |
| 480 | */ |
| 481 | |
| 482 | if (daemon__port == 0) { |
| 483 | struct servent *se = getservbyname(quis(), "udp"); |
| 484 | if (se) |
| 485 | daemon__port = se->s_port; |
| 486 | else |
| 487 | daemon__port = htons(SERVER_PORT); |
| 488 | } |
| 489 | |
| 490 | /* --- Now set up a socket --- */ |
| 491 | |
| 492 | { |
| 493 | struct sockaddr_in sin; |
| 494 | |
| 495 | if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1) |
| 496 | die(1, "couldn't create socket: %s", strerror(errno)); |
| 497 | sin.sin_family = AF_INET; |
| 498 | sin.sin_port = daemon__port; |
| 499 | sin.sin_addr.s_addr = htonl(INADDR_ANY); |
| 500 | if (bind(s, (struct sockaddr *)&sin, sizeof(sin))) { |
| 501 | die(1, "couldn't bind socket to port %i: %s", |
| 502 | ntohs(daemon__port), strerror(errno)); |
| 503 | } |
| 504 | } |
| 505 | |
| 506 | /* --- Fork off into the sunset --- */ |
| 507 | |
| 508 | if (!(f & df_nofork)) { |
| 509 | int pid = fork(); |
| 510 | FILE *fp; |
| 511 | |
| 512 | /* --- Make a background process --- */ |
| 513 | |
| 514 | if (pid == -1) |
| 515 | die(1, "couldn't fork daemon: %s", strerror(errno)); |
| 516 | else if (pid != 0) |
| 517 | return; |
| 518 | |
| 519 | /* --- Disconnect from the terminal --- */ |
| 520 | |
| 521 | setsid(); |
| 522 | |
| 523 | /* --- Write my process id to a file --- */ |
| 524 | |
| 525 | if ((fp = fopen(file_PID, "w")) != 0) { |
| 526 | fprintf(fp, "%lu\n", (unsigned long)getpid()); |
| 527 | fclose(fp); |
| 528 | } |
| 529 | T( trace(TRACE_DAEMON, "daemon: forked to pid %li", (long)getpid()); ) |
| 530 | } |
| 531 | |
| 532 | /* --- Set signal handlers --- */ |
| 533 | |
| 534 | for (i = 0; sigs[i].proc; i++) |
| 535 | sig_add(&sigs[i].s, sigs[i].sig, sigs[i].proc, 0); |
| 536 | |
| 537 | /* --- Set the timer for rescanning the file --- */ |
| 538 | |
| 539 | daemon__setTimer(); |
| 540 | |
| 541 | /* --- Watch for input --- */ |
| 542 | |
| 543 | sel_initfile(&daemon__sel, &daemon__listen, s, SEL_READ, |
| 544 | daemon__read, 0); |
| 545 | sel_addfile(&daemon__listen); |
| 546 | |
| 547 | /* --- Now wait for something exciting to happen --- */ |
| 548 | |
| 549 | for (;;) { |
| 550 | if (sel_select(&daemon__sel)) { |
| 551 | if (errno == EINTR || errno == EAGAIN) |
| 552 | continue; |
| 553 | syslog(LOG_ERR, "error from select: %s", strerror(errno)); |
| 554 | exit(1); |
| 555 | } |
| 556 | } |
| 557 | } |
| 558 | |
| 559 | /*----- That's all, folks -------------------------------------------------*/ |