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

   1 /* -*-c-*-
   2  *
   3  * $Id: daemon.c,v 1.14 2003/10/17 16:30:22 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 1.14  2003/10/17 16:30:22  mdw
  33  * Reload keys and config files automatically.
  34  *
  35  * Revision 1.13  2003/10/12 10:00:06  mdw
  36  * Fix for daemon mode.  Oops.
  37  *
  38  * Revision 1.12  2003/10/12 00:14:55  mdw
  39  * Major overhaul.  Now uses DSA signatures rather than the bogus symmetric
  40  * encrypt-and-hope thing.  Integrated with mLib and Catacomb.
  41  *
  42  * Revision 1.11  1999/05/04 16:17:12  mdw
  43  * Change to header file name for parser.  See log for `parse.h' for
  44  * details.
  45  *
  46  * Revision 1.10  1998/04/23  13:23:09  mdw
  47  * Support new interface to configuration file parser.
  48  *
  49  * Revision 1.9  1998/01/12 16:45:59  mdw
  50  * Fix copyright date.
  51  *
  52  * Revision 1.8  1997/09/26 09:14:58  mdw
  53  * Merged blowfish branch into trunk.
  54  *
  55  * Revision 1.7.2.1  1997/09/26 09:08:05  mdw
  56  * Use the Blowfish encryption algorithm instead of IDEA.  This is partly
  57  * because I prefer Blowfish (without any particularly strong evidence) but
  58  * mainly because IDEA is patented and Blowfish isn't.
  59  *
  60  * Revision 1.7  1997/09/17 10:23:23  mdw
  61  * Fix a typo.  Port numbers are in network order now, so don't change them.
  62  *
  63  * Revision 1.6  1997/09/09 18:17:06  mdw
  64  * Allow default port to be given as a service name or port number.
  65  *
  66  * Revision 1.5  1997/08/20  16:17:10  mdw
  67  * More sensible restart routine: `_reinit' functions replaced by `_end' and
  68  * `_init' functions.
  69  *
  70  * Revision 1.4  1997/08/07 10:00:37  mdw
  71  * (Log entry for previous version is bogus.)  Read netgroups database.
  72  * Give up privileges permanently on startup.
  73  *
  74  * Revision 1.2  1997/08/04 10:24:21  mdw
  75  * Sources placed under CVS control.
  76  *
  77  * Revision 1.1  1997/07/21  13:47:50  mdw
  78  * Initial revision
  79  *
  80  */
  81
  82 /*----- Header files ------------------------------------------------------*/
  83
  84 /* --- ANSI headers --- */
  85
  86 #include <errno.h>
  87 #include <signal.h>
  88 #include <stdio.h>
  89 #include <stdlib.h>
  90 #include <string.h>
  91
  92 /* --- Unix headers --- */
  93
  94 #include <sys/types.h>
  95 #include <sys/time.h>
  96 #include <sys/socket.h>
  97
  98 #include <netinet/in.h>
  99
 100 #include <arpa/inet.h>
 101
 102 #include <netdb.h>
 103 #include <syslog.h>
 104 #include <unistd.h>
 105
 106 /* --- mLib headers --- */
 107
 108 #include <mLib/fwatch.h>
 109 #include <mLib/quis.h>
 110 #include <mLib/report.h>
 111 #include <mLib/sel.h>
 112 #include <mLib/sig.h>
 113 #include <mLib/sym.h>
 114 #include <mLib/trace.h>
 115
 116 /* --- Catacomb headers --- */
 117
 118 #include <catacomb/buf.h>
 119 #include <catacomb/dsa.h>
 120 #include <catacomb/key.h>
 121 #include <catacomb/mp.h>
 122 #include <catacomb/noise.h>
 123 #include <catacomb/paranoia.h>
 124 #include <catacomb/rand.h>
 125 #include <catacomb/sha.h>
 126
 127 /* --- Local headers --- */
 128
 129 #include "become.h"
 130 #include "config.h"
 131 #include "daemon.h"
 132 #include "lexer.h"
 133 #include "name.h"
 134 #include "netg.h"
 135 #include "parse.h"
 136 #include "rule.h"
 137 #include "userdb.h"
 138
 139 /*----- Arbitrary constants -----------------------------------------------*/
 140
 141 /* #define daemon__awakeEvery (5 * 60)  /\* Awaken this often to rescan *\/ */
 142 #define daemon__awakeEvery (10)         /* Awaken this often to rescan */
 143
 144 /*----- Static variables --------------------------------------------------*/
 145
 146 static int daemon__port = -1;           /* No particular port yet */
 147 static fwatch daemon__cwatch, daemon__kwatch; /* Watching key / config files */
 148 static sel_timer daemon__timer;         /* Timer for reading */
 149 static sel_state daemon__sel;           /* Select context */
 150 static sel_file daemon__listen;         /* Listening socket selector */
 151 static const char *daemon__config;      /* Configuration file for daemon */
 152 static const char *daemon__keyfile;     /* Keyring file for daemon */
 153 static dsa_priv daemon__key;            /* The key data */
 154
 155 /*----- Main code ---------------------------------------------------------*/
 156
 157 /* --- @daemon_usePort@ --- *
 158  *
 159  * Arguments:   @int port@ = port to use, please
 160  *
 161  * Returns:     ---
 162  *
 163  * Use:         Instructs the daemon to listen to the given port.
 164  */
 165
 166 void daemon_usePort(int port)
 167 {
 168   daemon__port = port;
 169 }
 170
 171 /* --- @daemon__moan@ --- *
 172  *
 173  * Arguments:   @const char *f@ = offending file name
 174  *              @int line@ = offending line of the file
 175  *              @const char *msg@ = message
 176  *              @void *p@ = ignored
 177  *
 178  * Returns:     ---
 179  *
 180  * Use:         Reports an error message about a key file.
 181  */
 182
 183 static void daemon__moan(const char *f, int line, const char *msg, void *p)
 184 {
 185   syslog(LOG_ERR, "key file error: %s: %d: %s", f, line, msg);
 186   T( trace(TRACE_DAEMON, "daemon: key file error: %s: %d: %s",
 187            f, line, msg); )
 188 }
 189
 190 /* --- @daemon_readKey@ --- *
 191  *
 192  * Arguments:   @const char *kf@ = pointer to key file name to use
 193  *
 194  * Returns:     ---
 195  *
 196  * Use:         Loads the private key from the key file.
 197  */
 198
 199 void daemon_readKey(const char *kf)
 200 {
 201   key_packstruct kps[DSA_PRIVFETCHSZ];
 202   key_packdef *kp;
 203   key_file f;
 204   key *k;
 205   int err;
 206
 207   if (daemon__keyfile)
 208     return;
 209   T( trace(TRACE_DAEMON, "daemon: reading key from `%s'", kf); )
 210   if (key_open(&f, kf, KOPEN_READ, daemon__moan, 0))
 211     return;
 212   kp = key_fetchinit(dsa_privfetch, kps, &daemon__key);
 213   if ((k = key_bytype(&f, "become-dsa")) == 0)
 214     err = KERR_NOTFOUND;
 215   else
 216     err = key_fetch(kp, k);
 217   if (err)
 218     syslog(LOG_ERR, "couldn't load key: %s", key_strerror(err));
 219   else {
 220     mp_copy(daemon__key.dp.p);
 221     mp_copy(daemon__key.dp.q);
 222     mp_copy(daemon__key.dp.g);
 223     mp_copy(daemon__key.x);
 224     mp_copy(daemon__key.y);
 225   }
 226   key_fetchdone(kp);
 227   key_close(&f);
 228   daemon__keyfile = kf;
 229 }
 230
 231 /* --- @daemon__readConfig@ --- *
 232  *
 233  * Arguments:   @const char *cf@ = pointer to configuration file to use
 234  *
 235  * Returns:     Zero if it worked, nonzero if it hurt...
 236  *
 237  * Use:         Reads the configuration file, and other things.
 238  */
 239
 240 static int daemon__readConfig(const char *cf)
 241 {
 242   FILE *fp;
 243
 244   daemon__keyfile = 0;
 245   if ((fp = fopen(cf, "r")) == 0)
 246     return (-1);
 247   lexer_scan(fp);
 248   parse();
 249   fclose(fp);
 250   if (!daemon__keyfile)
 251     daemon_readKey(file_KEY);
 252   T( trace(TRACE_DAEMON, "daemon: read config file"); )
 253   return (0);
 254 }
 255
 256 /* --- @daemon__read@ --- *
 257  *
 258  * Arguments:   @int fd@ = socket handle
 259  *              @unsigned mode@ = ignored
 260  *              @void *p@ = ignored
 261  *
 262  * Returns:     ---
 263  *
 264  * Use:         Examines a buffer, and returns a response.
 265  */
 266
 267 void daemon__read(int fd, unsigned mode, void *p)
 268 {
 269   unsigned char buff[65536];            /* Buffer for incoming packets */
 270   struct sockaddr_in sin;               /* Address of packet sender */
 271   char sender[64];                      /* Sender's hostname (resolved) */
 272   octet h[SHA_HASHSZ];                  /* Hash of the transmission buffer */
 273   sha_ctx hc;                           /* Hashing context */
 274   request rq;                           /* Request buffer for verification */
 275   ssize_t sz;                           /* Length of incoming message */
 276   socklen_t slen;                       /* Length of incoming address */
 277   uint32 u;                             /* Scratch integer */
 278   uint16 ul;                            /* And another */
 279   struct hostent *he;                   /* Resolve structure */
 280   mp *m, *k, *r, *s;                    /* Integers for signing */
 281   int ans;                              /* Answer from the check */
 282   buf b;                                /* Buffer for parsing request */
 283
 284   /* --- Kick some randomness in the pot --- */
 285
 286   noise_timer(RAND_GLOBAL);
 287
 288   /* --- Read the message --- */
 289
 290   slen = sizeof(sin);
 291   if ((sz = recvfrom(fd, (char *)buff, sizeof(buff), 0,
 292                      (struct sockaddr *)&sin, &slen)) < 0) {
 293     T( trace(TRACE_DAEMON, "daemon: error reading packet: %s",
 294              strerror(errno)); )
 295     syslog(LOG_INFO, "duff packet received: %e");
 296     return;
 297   }
 298
 299   /* --- Resolve the host name --- */
 300
 301   he = gethostbyaddr((char *)&sin.sin_addr, sizeof(sin.sin_addr), AF_INET);
 302   sender[0] = 0;
 303   strncat(sender, he ? he->h_name : inet_ntoa(sin.sin_addr),
 304           sizeof(sender) - 1);
 305   syslog(LOG_DEBUG, "packet received from %s", sender);
 306   T( trace(TRACE_DAEMON, "daemon: received request from %s", sender); )
 307
 308   /* --- Sanity check --- */
 309
 310   if (!daemon__keyfile) {
 311     syslog(LOG_NOTICE, "no key file: ignoring request");
 312     T( trace(TRACE_DAEMON, "daemon: no key file: ignoring request"); )
 313     return;
 314   }
 315
 316   /* --- Unpack the block --- */
 317
 318   rq.host = sin.sin_addr;
 319   buf_init(&b, buff, sz);
 320   if (buf_ensure(&b, SHA_HASHSZ)) goto fail;  BSTEP(&b, SHA_HASHSZ);
 321   if (buf_getu32(&b, &u)) goto fail;  rq.from = u;
 322   if (buf_getu32(&b, &u)) goto fail;  rq.to = u;
 323   if (buf_getu16(&b, &ul) || buf_ensure(&b, ul) || ul >= sizeof(rq.cmd))
 324     goto fail;
 325   memcpy(rq.cmd, BCUR(&b), ul);
 326   rq.cmd[ul] = 0;
 327   BSTEP(&b, ul);
 328   if (BLEFT(&b)) goto fail;
 329
 330   /* --- Hash the request block --- */
 331
 332   sha_init(&hc);
 333   sha_hash(&hc, buff, sz);
 334   sha_done(&hc, h);
 335
 336   /* --- Build a reply block --- */
 337
 338   ans = rule_check(&rq);
 339   syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s",
 340          sender, rq.from, rq.to, rq.cmd, ans ? "granted" : "denied");
 341   buf_init(&b, buff, sizeof(buff));
 342   if (buf_put(&b, h, sizeof(h)) || buf_putbyte(&b, ans))
 343     goto fail;
 344
 345   /* --- Sign the reply block --- */
 346
 347   sha_init(&hc);
 348   sha_hash(&hc, BBASE(&b), BLEN(&b));
 349   sha_done(&hc, h);
 350   m = mp_loadb(MP_NEW, h, sizeof(h));
 351   rand_get(RAND_GLOBAL, h, sizeof(h));
 352   k = mp_loadb(MP_NEWSEC, h, sizeof(h));
 353   r = s = MP_NEW;
 354   dsa_mksig(&daemon__key.dp, daemon__key.x, m, k, &r, &s);
 355   buf_putmp(&b, r);
 356   buf_putmp(&b, s);
 357   mp_drop(m);
 358   mp_drop(k);
 359   mp_drop(r);
 360   mp_drop(s);
 361   if (BBAD(&b))
 362     goto fail;
 363
 364   /* --- Send the reply off --- */
 365
 366   sendto(fd, BBASE(&b), BLEN(&b), 0, (struct sockaddr *)&sin, sizeof(sin));
 367   T( trace(TRACE_DAEMON, "daemon: reply sent"); )
 368   return;
 369
 370 fail:
 371   syslog(LOG_ERR, "couldn't respond to query");
 372   T( trace(TRACE_DAEMON, "daemon: failed to answer query"); )
 373 }
 374
 375 /* --- @daemon__die@ --- *
 376  *
 377  * Arguments:   @int n@ = signal number
 378  *              @void *p@ = ignored
 379  *
 380  * Returns:     Doesn't.
 381  *
 382  * Use:         Exits the daemon.
 383  */
 384
 385 static void daemon__die(int n, void *p)
 386 {
 387   T( trace(TRACE_DAEMON, "daemon: killed by signal %i", n); )
 388   syslog(LOG_NOTICE, "killed by signal type %i", n);
 389   remove(file_PID);
 390   exit(0);
 391 }
 392
 393 /* --- @daemon__setTimer@ --- *
 394  *
 395  * Arguments:   ---
 396  *
 397  * Returns:     ---
 398  *
 399  * Use:         Sets the interval timer up.
 400  */
 401
 402 static void daemon__wakeUp(struct timeval *tv, void *p);
 403
 404 static void daemon__setTimer(void)
 405 {
 406   struct timeval tv;
 407
 408   gettimeofday(&tv, 0);
 409   tv.tv_sec += daemon__awakeEvery;
 410   sel_addtimer(&daemon__sel, &daemon__timer, &tv, daemon__wakeUp, 0);
 411 }
 412
 413 /* --- @daemon__rescan@ --- *
 414  *
 415  * Arguments:   @int n@ = signal number
 416  *              @void *p@ = ignored
 417  *
 418  * Returns:     ---
 419  *
 420  * Use:         Forces a rescan of the daemon's configuration.
 421  */
 422
 423 static void daemon__rescan(int n, void *p)
 424 {
 425   syslog(LOG_INFO, "rescanning configuration file");
 426   name_end();
 427   rule_end();
 428   netg_end();
 429   userdb_end();
 430   dsa_privfree(&daemon__key);
 431   userdb_init();
 432   userdb_local();
 433   userdb_yp();
 434   netg_init();
 435   rule_init();
 436   name_init();
 437   if (daemon__readConfig(daemon__config))
 438     syslog(LOG_ERR, "error reading configuration file");
 439   sel_rmtimer(&daemon__timer);
 440   daemon__setTimer();
 441   fwatch_update(&daemon__cwatch, daemon__config);
 442   fwatch_update(&daemon__kwatch, daemon__keyfile);
 443 }
 444
 445 /* --- @daemon__wakeUp@ --- *
 446  *
 447  * Arguments:   @struct timeval *tv@ = ignored
 448  *              @void *p@ = ignored
 449  *
 450  * Returns:     ---
 451  *
 452  * Use:         Wakes up periodically to check the configuration file.
 453  */
 454
 455 static void daemon__wakeUp(struct timeval *tv, void *p)
 456 {
 457   T( trace(TRACE_DAEMON, "daemon: interval timer"); )
 458   rand_seed(RAND_GLOBAL, 160);
 459   daemon__setTimer();
 460   if (fwatch_update(&daemon__cwatch, daemon__config))
 461     daemon__rescan(0, 0);
 462   else if (fwatch_update(&daemon__kwatch, daemon__keyfile)) {
 463     const char *kf = daemon__keyfile;
 464     daemon__keyfile = 0;
 465     daemon_readKey(kf);
 466   }
 467 }
 468
 469 /* --- @daemon_init@ --- *
 470  *
 471  * Arguments:   @const char *cf@ = pointer to name of configuration file
 472  *              @int port@ = port to listen to, or %$-1$% for default
 473  *              @unsigned f@ = various flags
 474  *
 475  * Returns:     Never.
 476  *
 477  * Use:         Starts `become' up in daemon mode.
 478  */
 479
 480 void daemon_init(const char *cf, int port, unsigned f)
 481 {
 482   int s;
 483   int i;
 484
 485   static struct sigvec {
 486     int sig;
 487     void (*proc)(int n, void *p);
 488     sig s;
 489   } sigs[] = {
 490     { SIGHUP, daemon__rescan },
 491     { SIGINT, daemon__die },
 492     { SIGTERM, daemon__die },
 493     { SIGQUIT, daemon__die },
 494     { 0, 0 }
 495   };
 496
 497   /* --- Remove my root privileges --- *
 498    *
 499    * Just in case there's anything dodgy in my configuration file, or the
 500    * user wants me to start on a funny port.
 501    */
 502
 503   setuid(getuid());
 504
 505   /* --- Initialize the random number generator --- */
 506
 507   rand_noisesrc(RAND_GLOBAL, &noise_source);
 508   rand_seed(RAND_GLOBAL, 160);
 509
 510   /* --- Initialise bits of the program --- */
 511
 512   daemon__config = cf;
 513   daemon__port = port;
 514   sel_init(&daemon__sel);
 515   sig_init(&daemon__sel);
 516   userdb_init();
 517   userdb_local();
 518   userdb_yp();
 519   netg_init();
 520   name_init();
 521   rule_init();
 522   openlog(quis(), 0, LOG_DAEMON);
 523   syslog(LOG_NOTICE, "starting up");
 524
 525   if (daemon__readConfig(daemon__config))
 526     die(1, "couldn't read configuration file");
 527   fwatch_init(&daemon__cwatch, daemon__config);
 528   fwatch_init(&daemon__kwatch, daemon__keyfile);
 529
 530   /* --- Decide on a port to use --- *
 531    *
 532    * If I don't have a port yet (e.g., from the configuration file) then
 533    * look it up in /etc/services under whatever name I was started as.
 534    */
 535
 536   if (daemon__port == 0) {
 537     struct servent *se = getservbyname(quis(), "udp");
 538     if (!se)
 539       die(1, "no idea which port to listen to");
 540     daemon__port = se->s_port;
 541   }
 542
 543   /* --- Now set up a socket --- */
 544
 545   {
 546     struct sockaddr_in sin;
 547
 548     if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
 549       die(1, "couldn't create socket: %s", strerror(errno));
 550     sin.sin_family = AF_INET;
 551     sin.sin_port = daemon__port;
 552     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 553     if (bind(s, (struct sockaddr *)&sin, sizeof(sin))) {
 554       die(1, "couldn't bind socket to port %i: %s",
 555           ntohs(daemon__port), strerror(errno));
 556     }
 557   }
 558
 559   /* --- Fork off into the sunset --- */
 560
 561   if (!(f & df_nofork)) {
 562     int pid = fork();
 563     FILE *fp;
 564
 565     /* --- Make a background process --- */
 566
 567     if (pid == -1)
 568       die(1, "couldn't fork daemon: %s", strerror(errno));
 569     else if (pid != 0)
 570       return;
 571
 572     /* --- Disconnect from the terminal --- */
 573
 574     setsid();
 575
 576     /* --- Write my process id to a file --- */
 577
 578     if ((fp = fopen(file_PID, "w")) != 0) {
 579       fprintf(fp, "%lu\n", (unsigned long)getpid());
 580       fclose(fp);
 581     }
 582     T( trace(TRACE_DAEMON, "daemon: forked to pid %li", (long)getpid()); )
 583   }
 584
 585   /* --- Set signal handlers --- */
 586
 587   for (i = 0; sigs[i].proc; i++)
 588     sig_add(&sigs[i].s, sigs[i].sig, sigs[i].proc, 0);
 589
 590   /* --- Set the timer for rescanning the file --- */
 591
 592   daemon__setTimer();
 593
 594   /* --- Watch for input --- */
 595
 596   sel_initfile(&daemon__sel, &daemon__listen, s, SEL_READ,
 597                daemon__read, 0);
 598   sel_addfile(&daemon__listen);
 599
 600   /* --- Now wait for something exciting to happen --- */
 601
 602   for (;;) {
 603     if (sel_select(&daemon__sel)) {
 604       if (errno == EINTR || errno == EAGAIN)
 605         continue;
 606       syslog(LOG_ERR, "error from select: %s", strerror(errno));
 607       exit(1);
 608     }
 609   }
 610 }
 611
 612 /*----- That's all, folks -------------------------------------------------*/