mdw@git.distorted.org.uk Git - become/blob - src/daemon.c

   1 /* -*-c-*-
   2  *
   3  * $Id: daemon.c,v 1.15 2003/10/26 11:57:46 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 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: daemon.c,v $
  32  * Revision 1.15  2003/10/26 11:57:46  mdw
  33  * Fix key reloading core dumps.  Change advice on keys.
  34  *
  35  * Revision 1.14  2003/10/17 16:30:22  mdw
  36  * Reload keys and config files automatically.
  37  *
  38  * Revision 1.13  2003/10/12 10:00:06  mdw
  39  * Fix for daemon mode.  Oops.
  40  *
  41  * Revision 1.12  2003/10/12 00:14:55  mdw
  42  * Major overhaul.  Now uses DSA signatures rather than the bogus symmetric
  43  * encrypt-and-hope thing.  Integrated with mLib and Catacomb.
  44  *
  45  * Revision 1.11  1999/05/04 16:17:12  mdw
  46  * Change to header file name for parser.  See log for `parse.h' for
  47  * details.
  48  *
  49  * Revision 1.10  1998/04/23  13:23:09  mdw
  50  * Support new interface to configuration file parser.
  51  *
  52  * Revision 1.9  1998/01/12 16:45:59  mdw
  53  * Fix copyright date.
  54  *
  55  * Revision 1.8  1997/09/26 09:14:58  mdw
  56  * Merged blowfish branch into trunk.
  57  *
  58  * Revision 1.7.2.1  1997/09/26 09:08:05  mdw
  59  * Use the Blowfish encryption algorithm instead of IDEA.  This is partly
  60  * because I prefer Blowfish (without any particularly strong evidence) but
  61  * mainly because IDEA is patented and Blowfish isn't.
  62  *
  63  * Revision 1.7  1997/09/17 10:23:23  mdw
  64  * Fix a typo.  Port numbers are in network order now, so don't change them.
  65  *
  66  * Revision 1.6  1997/09/09 18:17:06  mdw
  67  * Allow default port to be given as a service name or port number.
  68  *
  69  * Revision 1.5  1997/08/20  16:17:10  mdw
  70  * More sensible restart routine: `_reinit' functions replaced by `_end' and
  71  * `_init' functions.
  72  *
  73  * Revision 1.4  1997/08/07 10:00:37  mdw
  74  * (Log entry for previous version is bogus.)  Read netgroups database.
  75  * Give up privileges permanently on startup.
  76  *
  77  * Revision 1.2  1997/08/04 10:24:21  mdw
  78  * Sources placed under CVS control.
  79  *
  80  * Revision 1.1  1997/07/21  13:47:50  mdw
  81  * Initial revision
  82  *
  83  */
  84
  85 /*----- Header files ------------------------------------------------------*/
  86
  87 /* --- ANSI headers --- */
  88
  89 #include <errno.h>
  90 #include <signal.h>
  91 #include <stdio.h>
  92 #include <stdlib.h>
  93 #include <string.h>
  94
  95 /* --- Unix headers --- */
  96
  97 #include <sys/types.h>
  98 #include <sys/time.h>
  99 #include <sys/socket.h>
 100
 101 #include <netinet/in.h>
 102
 103 #include <arpa/inet.h>
 104
 105 #include <netdb.h>
 106 #include <syslog.h>
 107 #include <unistd.h>
 108
 109 /* --- mLib headers --- */
 110
 111 #include <mLib/fwatch.h>
 112 #include <mLib/quis.h>
 113 #include <mLib/report.h>
 114 #include <mLib/sel.h>
 115 #include <mLib/sig.h>
 116 #include <mLib/sym.h>
 117 #include <mLib/trace.h>
 118
 119 /* --- Catacomb headers --- */
 120
 121 #include <catacomb/buf.h>
 122 #include <catacomb/dsa.h>
 123 #include <catacomb/key.h>
 124 #include <catacomb/mp.h>
 125 #include <catacomb/noise.h>
 126 #include <catacomb/paranoia.h>
 127 #include <catacomb/rand.h>
 128 #include <catacomb/sha.h>
 129
 130 /* --- Local headers --- */
 131
 132 #include "become.h"
 133 #include "config.h"
 134 #include "daemon.h"
 135 #include "lexer.h"
 136 #include "name.h"
 137 #include "netg.h"
 138 #include "parse.h"
 139 #include "rule.h"
 140 #include "userdb.h"
 141
 142 /*----- Arbitrary constants -----------------------------------------------*/
 143
 144 #define daemon__awakeEvery (10)         /* Awaken this often to rescan */
 145
 146 /*----- Static variables --------------------------------------------------*/
 147
 148 static int daemon__port = -1;           /* No particular port yet */
 149 static fwatch daemon__cwatch, daemon__kwatch; /* Watching key / config files */
 150 static sel_timer daemon__timer;         /* Timer for reading */
 151 static sel_state daemon__sel;           /* Select context */
 152 static sel_file daemon__listen;         /* Listening socket selector */
 153 static const char *daemon__config;      /* Configuration file for daemon */
 154 static const char *daemon__keyfile;     /* Keyring file for daemon */
 155 static dsa_priv daemon__key;            /* The key data */
 156
 157 /*----- Main code ---------------------------------------------------------*/
 158
 159 /* --- @daemon_usePort@ --- *
 160  *
 161  * Arguments:   @int port@ = port to use, please
 162  *
 163  * Returns:     ---
 164  *
 165  * Use:         Instructs the daemon to listen to the given port.
 166  */
 167
 168 void daemon_usePort(int port)
 169 {
 170   daemon__port = port;
 171 }
 172
 173 /* --- @daemon__moan@ --- *
 174  *
 175  * Arguments:   @const char *f@ = offending file name
 176  *              @int line@ = offending line of the file
 177  *              @const char *msg@ = message
 178  *              @void *p@ = ignored
 179  *
 180  * Returns:     ---
 181  *
 182  * Use:         Reports an error message about a key file.
 183  */
 184
 185 static void daemon__moan(const char *f, int line, const char *msg, void *p)
 186 {
 187   syslog(LOG_ERR, "key file error: %s: %d: %s", f, line, msg);
 188   T( trace(TRACE_DAEMON, "daemon: key file error: %s: %d: %s",
 189            f, line, msg); )
 190 }
 191
 192 /* --- @daemon_readKey@ --- *
 193  *
 194  * Arguments:   @const char *kf@ = pointer to key file name to use
 195  *
 196  * Returns:     ---
 197  *
 198  * Use:         Loads the private key from the key file.
 199  */
 200
 201 void daemon_readKey(const char *kf)
 202 {
 203   key_packstruct kps[DSA_PRIVFETCHSZ];
 204   key_packdef *kp;
 205   key_file f;
 206   key *k;
 207   int err;
 208
 209   if (daemon__keyfile)
 210     return;
 211   T( trace(TRACE_DAEMON, "daemon: reading key from `%s'", kf); )
 212   if (key_open(&f, kf, KOPEN_READ, daemon__moan, 0))
 213     return;
 214   kp = key_fetchinit(dsa_privfetch, kps, &daemon__key);
 215   if ((k = key_bytype(&f, "become-dsa")) == 0)
 216     err = KERR_NOTFOUND;
 217   else
 218     err = key_fetch(kp, k);
 219   if (err)
 220     syslog(LOG_ERR, "couldn't load key: %s", key_strerror(err));
 221   else {
 222     mp_copy(daemon__key.dp.p);
 223     mp_copy(daemon__key.dp.q);
 224     mp_copy(daemon__key.dp.g);
 225     mp_copy(daemon__key.x);
 226     mp_copy(daemon__key.y);
 227     daemon__keyfile = kf;
 228   }
 229   key_fetchdone(kp);
 230   key_close(&f);
 231 }
 232
 233 /* --- @daemon__readConfig@ --- *
 234  *
 235  * Arguments:   @const char *cf@ = pointer to configuration file to use
 236  *
 237  * Returns:     Zero if it worked, nonzero if it hurt...
 238  *
 239  * Use:         Reads the configuration file, and other things.
 240  */
 241
 242 static int daemon__readConfig(const char *cf)
 243 {
 244   FILE *fp;
 245
 246   daemon__keyfile = 0;
 247   if ((fp = fopen(cf, "r")) == 0)
 248     return (-1);
 249   lexer_scan(fp);
 250   parse();
 251   fclose(fp);
 252   if (!daemon__keyfile)
 253     daemon_readKey(file_KEY);
 254   T( trace(TRACE_DAEMON, "daemon: read config file"); )
 255   return (0);
 256 }
 257
 258 /* --- @daemon__read@ --- *
 259  *
 260  * Arguments:   @int fd@ = socket handle
 261  *              @unsigned mode@ = ignored
 262  *              @void *p@ = ignored
 263  *
 264  * Returns:     ---
 265  *
 266  * Use:         Examines a buffer, and returns a response.
 267  */
 268
 269 void daemon__read(int fd, unsigned mode, void *p)
 270 {
 271   unsigned char buff[65536];            /* Buffer for incoming packets */
 272   struct sockaddr_in sin;               /* Address of packet sender */
 273   char sender[64];                      /* Sender's hostname (resolved) */
 274   octet h[SHA_HASHSZ];                  /* Hash of the transmission buffer */
 275   sha_ctx hc;                           /* Hashing context */
 276   request rq;                           /* Request buffer for verification */
 277   ssize_t sz;                           /* Length of incoming message */
 278   socklen_t slen;                       /* Length of incoming address */
 279   uint32 u;                             /* Scratch integer */
 280   uint16 ul;                            /* And another */
 281   struct hostent *he;                   /* Resolve structure */
 282   mp *m, *k, *r, *s;                    /* Integers for signing */
 283   int ans;                              /* Answer from the check */
 284   buf b;                                /* Buffer for parsing request */
 285
 286   /* --- Kick some randomness in the pot --- */
 287
 288   noise_timer(RAND_GLOBAL);
 289
 290   /* --- Read the message --- */
 291
 292   slen = sizeof(sin);
 293   if ((sz = recvfrom(fd, (char *)buff, sizeof(buff), 0,
 294                      (struct sockaddr *)&sin, &slen)) < 0) {
 295     T( trace(TRACE_DAEMON, "daemon: error reading packet: %s",
 296              strerror(errno)); )
 297     syslog(LOG_INFO, "duff packet received: %e");
 298     return;
 299   }
 300
 301   /* --- Resolve the host name --- */
 302
 303   he = gethostbyaddr((char *)&sin.sin_addr, sizeof(sin.sin_addr), AF_INET);
 304   sender[0] = 0;
 305   strncat(sender, he ? he->h_name : inet_ntoa(sin.sin_addr),
 306           sizeof(sender) - 1);
 307   syslog(LOG_DEBUG, "packet received from %s", sender);
 308   T( trace(TRACE_DAEMON, "daemon: received request from %s", sender); )
 309
 310   /* --- Sanity check --- */
 311
 312   if (!daemon__keyfile) {
 313     syslog(LOG_NOTICE, "no key file: ignoring request");
 314     T( trace(TRACE_DAEMON, "daemon: no key file: ignoring request"); )
 315     return;
 316   }
 317
 318   /* --- Unpack the block --- */
 319
 320   rq.host = sin.sin_addr;
 321   buf_init(&b, buff, sz);
 322   if (buf_ensure(&b, SHA_HASHSZ)) goto fail;  BSTEP(&b, SHA_HASHSZ);
 323   if (buf_getu32(&b, &u)) goto fail;  rq.from = u;
 324   if (buf_getu32(&b, &u)) goto fail;  rq.to = u;
 325   if (buf_getu16(&b, &ul) || buf_ensure(&b, ul) || ul >= sizeof(rq.cmd))
 326     goto fail;
 327   memcpy(rq.cmd, BCUR(&b), ul);
 328   rq.cmd[ul] = 0;
 329   BSTEP(&b, ul);
 330   if (BLEFT(&b)) goto fail;
 331
 332   /* --- Hash the request block --- */
 333
 334   sha_init(&hc);
 335   sha_hash(&hc, buff, sz);
 336   sha_done(&hc, h);
 337
 338   /* --- Build a reply block --- */
 339
 340   ans = rule_check(&rq);
 341   syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s",
 342          sender, rq.from, rq.to, rq.cmd, ans ? "granted" : "denied");
 343   buf_init(&b, buff, sizeof(buff));
 344   if (buf_put(&b, h, sizeof(h)) || buf_putbyte(&b, ans))
 345     goto fail;
 346
 347   /* --- Sign the reply block --- */
 348
 349   sha_init(&hc);
 350   sha_hash(&hc, BBASE(&b), BLEN(&b));
 351   sha_done(&hc, h);
 352   m = mp_loadb(MP_NEW, h, sizeof(h));
 353   rand_get(RAND_GLOBAL, h, sizeof(h));
 354   k = mp_loadb(MP_NEWSEC, h, sizeof(h));
 355   r = s = MP_NEW;
 356   dsa_mksig(&daemon__key.dp, daemon__key.x, m, k, &r, &s);
 357   buf_putmp(&b, r);
 358   buf_putmp(&b, s);
 359   mp_drop(m);
 360   mp_drop(k);
 361   mp_drop(r);
 362   mp_drop(s);
 363   if (BBAD(&b))
 364     goto fail;
 365
 366   /* --- Send the reply off --- */
 367
 368   sendto(fd, BBASE(&b), BLEN(&b), 0, (struct sockaddr *)&sin, sizeof(sin));
 369   T( trace(TRACE_DAEMON, "daemon: reply sent"); )
 370   return;
 371
 372 fail:
 373   syslog(LOG_ERR, "couldn't respond to query");
 374   T( trace(TRACE_DAEMON, "daemon: failed to answer query"); )
 375 }
 376
 377 /* --- @daemon__die@ --- *
 378  *
 379  * Arguments:   @int n@ = signal number
 380  *              @void *p@ = ignored
 381  *
 382  * Returns:     Doesn't.
 383  *
 384  * Use:         Exits the daemon.
 385  */
 386
 387 static void daemon__die(int n, void *p)
 388 {
 389   T( trace(TRACE_DAEMON, "daemon: killed by signal %i", n); )
 390   syslog(LOG_NOTICE, "killed by signal type %i", n);
 391   remove(file_PID);
 392   exit(0);
 393 }
 394
 395 /* --- @daemon__setTimer@ --- *
 396  *
 397  * Arguments:   ---
 398  *
 399  * Returns:     ---
 400  *
 401  * Use:         Sets the interval timer up.
 402  */
 403
 404 static void daemon__wakeUp(struct timeval *tv, void *p);
 405
 406 static void daemon__setTimer(void)
 407 {
 408   struct timeval tv;
 409
 410   gettimeofday(&tv, 0);
 411   tv.tv_sec += daemon__awakeEvery;
 412   sel_addtimer(&daemon__sel, &daemon__timer, &tv, daemon__wakeUp, 0);
 413 }
 414
 415 /* --- @daemon__rescan@ --- *
 416  *
 417  * Arguments:   @int n@ = signal number
 418  *              @void *p@ = ignored
 419  *
 420  * Returns:     ---
 421  *
 422  * Use:         Forces a rescan of the daemon's configuration.
 423  */
 424
 425 static void daemon__rescan(int n, void *p)
 426 {
 427   syslog(LOG_INFO, "rescanning configuration file");
 428   name_end();
 429   rule_end();
 430   netg_end();
 431   userdb_end();
 432   dsa_privfree(&daemon__key);
 433   userdb_init();
 434   userdb_local();
 435   userdb_yp();
 436   netg_init();
 437   rule_init();
 438   name_init();
 439   if (daemon__readConfig(daemon__config))
 440     syslog(LOG_ERR, "error reading configuration file");
 441   sel_rmtimer(&daemon__timer);
 442   daemon__setTimer();
 443   fwatch_update(&daemon__cwatch, daemon__config);
 444   fwatch_update(&daemon__kwatch, daemon__keyfile);
 445 }
 446
 447 /* --- @daemon__wakeUp@ --- *
 448  *
 449  * Arguments:   @struct timeval *tv@ = ignored
 450  *              @void *p@ = ignored
 451  *
 452  * Returns:     ---
 453  *
 454  * Use:         Wakes up periodically to check the configuration file.
 455  */
 456
 457 static void daemon__wakeUp(struct timeval *tv, void *p)
 458 {
 459   T( trace(TRACE_DAEMON, "daemon: interval timer"); )
 460   rand_seed(RAND_GLOBAL, 160);
 461   daemon__setTimer();
 462   if (fwatch_update(&daemon__cwatch, daemon__config))
 463     daemon__rescan(0, 0);
 464   else if (fwatch_update(&daemon__kwatch, daemon__keyfile)) {
 465     const char *kf = daemon__keyfile;
 466     daemon__keyfile = 0;
 467     daemon_readKey(kf);
 468   }
 469 }
 470
 471 /* --- @daemon_init@ --- *
 472  *
 473  * Arguments:   @const char *cf@ = pointer to name of configuration file
 474  *              @int port@ = port to listen to, or %$-1$% for default
 475  *              @unsigned f@ = various flags
 476  *
 477  * Returns:     Never.
 478  *
 479  * Use:         Starts `become' up in daemon mode.
 480  */
 481
 482 void daemon_init(const char *cf, int port, unsigned f)
 483 {
 484   int s;
 485   int i;
 486
 487   static struct sigvec {
 488     int sig;
 489     void (*proc)(int n, void *p);
 490     sig s;
 491   } sigs[] = {
 492     { SIGHUP, daemon__rescan },
 493     { SIGINT, daemon__die },
 494     { SIGTERM, daemon__die },
 495     { SIGQUIT, daemon__die },
 496     { 0, 0 }
 497   };
 498
 499   /* --- Remove my root privileges --- *
 500    *
 501    * Just in case there's anything dodgy in my configuration file, or the
 502    * user wants me to start on a funny port.
 503    */
 504
 505   setuid(getuid());
 506
 507   /* --- Initialize the random number generator --- */
 508
 509   rand_noisesrc(RAND_GLOBAL, &noise_source);
 510   rand_seed(RAND_GLOBAL, 160);
 511
 512   /* --- Initialise bits of the program --- */
 513
 514   daemon__config = cf;
 515   daemon__port = port;
 516   sel_init(&daemon__sel);
 517   sig_init(&daemon__sel);
 518   userdb_init();
 519   userdb_local();
 520   userdb_yp();
 521   netg_init();
 522   name_init();
 523   rule_init();
 524   openlog(quis(), 0, LOG_DAEMON);
 525   syslog(LOG_NOTICE, "starting up");
 526
 527   if (daemon__readConfig(daemon__config))
 528     die(1, "couldn't read configuration file");
 529   fwatch_init(&daemon__cwatch, daemon__config);
 530   fwatch_init(&daemon__kwatch, daemon__keyfile);
 531
 532   /* --- Decide on a port to use --- *
 533    *
 534    * If I don't have a port yet (e.g., from the configuration file) then
 535    * look it up in /etc/services under whatever name I was started as.
 536    */
 537
 538   if (daemon__port == 0) {
 539     struct servent *se = getservbyname(quis(), "udp");
 540     if (!se)
 541       die(1, "no idea which port to listen to");
 542     daemon__port = se->s_port;
 543   }
 544
 545   /* --- Now set up a socket --- */
 546
 547   {
 548     struct sockaddr_in sin;
 549
 550     if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
 551       die(1, "couldn't create socket: %s", strerror(errno));
 552     sin.sin_family = AF_INET;
 553     sin.sin_port = daemon__port;
 554     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 555     if (bind(s, (struct sockaddr *)&sin, sizeof(sin))) {
 556       die(1, "couldn't bind socket to port %i: %s",
 557           ntohs(daemon__port), strerror(errno));
 558     }
 559   }
 560
 561   /* --- Fork off into the sunset --- */
 562
 563   if (!(f & df_nofork)) {
 564     int pid = fork();
 565     FILE *fp;
 566
 567     /* --- Make a background process --- */
 568
 569     if (pid == -1)
 570       die(1, "couldn't fork daemon: %s", strerror(errno));
 571     else if (pid != 0)
 572       return;
 573
 574     /* --- Disconnect from the terminal --- */
 575
 576     setsid();
 577
 578     /* --- Write my process id to a file --- */
 579
 580     if ((fp = fopen(file_PID, "w")) != 0) {
 581       fprintf(fp, "%lu\n", (unsigned long)getpid());
 582       fclose(fp);
 583     }
 584     T( trace(TRACE_DAEMON, "daemon: forked to pid %li", (long)getpid()); )
 585   }
 586
 587   /* --- Set signal handlers --- */
 588
 589   for (i = 0; sigs[i].proc; i++)
 590     sig_add(&sigs[i].s, sigs[i].sig, sigs[i].proc, 0);
 591
 592   /* --- Set the timer for rescanning the file --- */
 593
 594   daemon__setTimer();
 595
 596   /* --- Watch for input --- */
 597
 598   sel_initfile(&daemon__sel, &daemon__listen, s, SEL_READ,
 599                daemon__read, 0);
 600   sel_addfile(&daemon__listen);
 601
 602   /* --- Now wait for something exciting to happen --- */
 603
 604   for (;;) {
 605     if (sel_select(&daemon__sel)) {
 606       if (errno == EINTR || errno == EAGAIN)
 607         continue;
 608       syslog(LOG_ERR, "error from select: %s", strerror(errno));
 609       exit(1);
 610     }
 611   }
 612 }
 613
 614 /*----- That's all, folks -------------------------------------------------*/