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

   1 /* -*-c-*-
   2  *
   3  * $Id: daemon.c,v 1.16 2003/11/29 23:39:16 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 1.16  2003/11/29 23:39:16  mdw
  33  * Debianization.
  34  *
  35  * Revision 1.15  2003/10/26 11:57:46  mdw
  36  * Fix key reloading core dumps.  Change advice on keys.
  37  *
  38  * Revision 1.14  2003/10/17 16:30:22  mdw
  39  * Reload keys and config files automatically.
  40  *
  41  * Revision 1.13  2003/10/12 10:00:06  mdw
  42  * Fix for daemon mode.  Oops.
  43  *
  44  * Revision 1.12  2003/10/12 00:14:55  mdw
  45  * Major overhaul.  Now uses DSA signatures rather than the bogus symmetric
  46  * encrypt-and-hope thing.  Integrated with mLib and Catacomb.
  47  *
  48  * Revision 1.11  1999/05/04 16:17:12  mdw
  49  * Change to header file name for parser.  See log for `parse.h' for
  50  * details.
  51  *
  52  * Revision 1.10  1998/04/23  13:23:09  mdw
  53  * Support new interface to configuration file parser.
  54  *
  55  * Revision 1.9  1998/01/12 16:45:59  mdw
  56  * Fix copyright date.
  57  *
  58  * Revision 1.8  1997/09/26 09:14:58  mdw
  59  * Merged blowfish branch into trunk.
  60  *
  61  * Revision 1.7.2.1  1997/09/26 09:08:05  mdw
  62  * Use the Blowfish encryption algorithm instead of IDEA.  This is partly
  63  * because I prefer Blowfish (without any particularly strong evidence) but
  64  * mainly because IDEA is patented and Blowfish isn't.
  65  *
  66  * Revision 1.7  1997/09/17 10:23:23  mdw
  67  * Fix a typo.  Port numbers are in network order now, so don't change them.
  68  *
  69  * Revision 1.6  1997/09/09 18:17:06  mdw
  70  * Allow default port to be given as a service name or port number.
  71  *
  72  * Revision 1.5  1997/08/20  16:17:10  mdw
  73  * More sensible restart routine: `_reinit' functions replaced by `_end' and
  74  * `_init' functions.
  75  *
  76  * Revision 1.4  1997/08/07 10:00:37  mdw
  77  * (Log entry for previous version is bogus.)  Read netgroups database.
  78  * Give up privileges permanently on startup.
  79  *
  80  * Revision 1.2  1997/08/04 10:24:21  mdw
  81  * Sources placed under CVS control.
  82  *
  83  * Revision 1.1  1997/07/21  13:47:50  mdw
  84  * Initial revision
  85  *
  86  */
  87
  88 /*----- Header files ------------------------------------------------------*/
  89
  90 /* --- ANSI headers --- */
  91
  92 #include <errno.h>
  93 #include <signal.h>
  94 #include <stdio.h>
  95 #include <stdlib.h>
  96 #include <string.h>
  97
  98 /* --- Unix headers --- */
  99
 100 #include <sys/types.h>
 101 #include <sys/time.h>
 102 #include <sys/socket.h>
 103
 104 #include <netinet/in.h>
 105
 106 #include <arpa/inet.h>
 107
 108 #include <netdb.h>
 109 #include <syslog.h>
 110 #include <unistd.h>
 111
 112 /* --- mLib headers --- */
 113
 114 #include <mLib/fwatch.h>
 115 #include <mLib/quis.h>
 116 #include <mLib/report.h>
 117 #include <mLib/sel.h>
 118 #include <mLib/sig.h>
 119 #include <mLib/sym.h>
 120 #include <mLib/trace.h>
 121
 122 /* --- Catacomb headers --- */
 123
 124 #include <catacomb/buf.h>
 125 #include <catacomb/dsa.h>
 126 #include <catacomb/key.h>
 127 #include <catacomb/mp.h>
 128 #include <catacomb/noise.h>
 129 #include <catacomb/paranoia.h>
 130 #include <catacomb/rand.h>
 131 #include <catacomb/sha.h>
 132
 133 /* --- Local headers --- */
 134
 135 #include "become.h"
 136 #include "config.h"
 137 #include "daemon.h"
 138 #include "lexer.h"
 139 #include "name.h"
 140 #include "netg.h"
 141 #include "parse.h"
 142 #include "rule.h"
 143 #include "userdb.h"
 144
 145 /*----- Arbitrary constants -----------------------------------------------*/
 146
 147 #define daemon__awakeEvery (10)         /* Awaken this often to rescan */
 148
 149 /*----- Static variables --------------------------------------------------*/
 150
 151 static int daemon__port = -1;           /* No particular port yet */
 152 static fwatch daemon__cwatch, daemon__kwatch; /* Watching key/config files */
 153 static sel_timer daemon__timer;         /* Timer for reading */
 154 static sel_state daemon__sel;           /* Select context */
 155 static sel_file daemon__listen;         /* Listening socket selector */
 156 static const char *daemon__config;      /* Configuration file for daemon */
 157 static const char *daemon__keyfile;     /* Keyring file for daemon */
 158 static dsa_priv daemon__key;            /* The key data */
 159
 160 /*----- Main code ---------------------------------------------------------*/
 161
 162 /* --- @daemon_usePort@ --- *
 163  *
 164  * Arguments:   @int port@ = port to use, please
 165  *
 166  * Returns:     ---
 167  *
 168  * Use:         Instructs the daemon to listen to the given port.
 169  */
 170
 171 void daemon_usePort(int port)
 172 {
 173   daemon__port = port;
 174 }
 175
 176 /* --- @daemon__moan@ --- *
 177  *
 178  * Arguments:   @const char *f@ = offending file name
 179  *              @int line@ = offending line of the file
 180  *              @const char *msg@ = message
 181  *              @void *p@ = ignored
 182  *
 183  * Returns:     ---
 184  *
 185  * Use:         Reports an error message about a key file.
 186  */
 187
 188 static void daemon__moan(const char *f, int line, const char *msg, void *p)
 189 {
 190   syslog(LOG_ERR, "key file error: %s: %d: %s", f, line, msg);
 191   T( trace(TRACE_DAEMON, "daemon: key file error: %s: %d: %s",
 192            f, line, msg); )
 193 }
 194
 195 /* --- @daemon_readKey@ --- *
 196  *
 197  * Arguments:   @const char *kf@ = pointer to key file name to use
 198  *
 199  * Returns:     ---
 200  *
 201  * Use:         Loads the private key from the key file.
 202  */
 203
 204 void daemon_readKey(const char *kf)
 205 {
 206   key_packstruct kps[DSA_PRIVFETCHSZ];
 207   key_packdef *kp;
 208   key_file f;
 209   key *k;
 210   int err;
 211
 212   if (daemon__keyfile)
 213     return;
 214   T( trace(TRACE_DAEMON, "daemon: reading key from `%s'", kf); )
 215   if (key_open(&f, kf, KOPEN_READ, daemon__moan, 0))
 216     return;
 217   kp = key_fetchinit(dsa_privfetch, kps, &daemon__key);
 218   if ((k = key_bytype(&f, "become-dsa")) == 0)
 219     err = KERR_NOTFOUND;
 220   else
 221     err = key_fetch(kp, k);
 222   if (err)
 223     syslog(LOG_ERR, "couldn't load key: %s", key_strerror(err));
 224   else {
 225     mp_copy(daemon__key.dp.p);
 226     mp_copy(daemon__key.dp.q);
 227     mp_copy(daemon__key.dp.g);
 228     mp_copy(daemon__key.x);
 229     mp_copy(daemon__key.y);
 230     daemon__keyfile = kf;
 231   }
 232   key_fetchdone(kp);
 233   key_close(&f);
 234 }
 235
 236 /* --- @daemon__readConfig@ --- *
 237  *
 238  * Arguments:   @const char *cf@ = pointer to configuration file to use
 239  *
 240  * Returns:     Zero if it worked, nonzero if it hurt...
 241  *
 242  * Use:         Reads the configuration file, and other things.
 243  */
 244
 245 static int daemon__readConfig(const char *cf)
 246 {
 247   FILE *fp;
 248
 249   daemon__keyfile = 0;
 250   if ((fp = fopen(cf, "r")) == 0)
 251     return (-1);
 252   lexer_scan(fp);
 253   parse();
 254   fclose(fp);
 255   if (!daemon__keyfile)
 256     daemon_readKey(file_KEY);
 257   T( trace(TRACE_DAEMON, "daemon: read config file"); )
 258   return (0);
 259 }
 260
 261 /* --- @daemon__read@ --- *
 262  *
 263  * Arguments:   @int fd@ = socket handle
 264  *              @unsigned mode@ = ignored
 265  *              @void *p@ = ignored
 266  *
 267  * Returns:     ---
 268  *
 269  * Use:         Examines a buffer, and returns a response.
 270  */
 271
 272 void daemon__read(int fd, unsigned mode, void *p)
 273 {
 274   unsigned char buff[65536];            /* Buffer for incoming packets */
 275   struct sockaddr_in sin;               /* Address of packet sender */
 276   char sender[64];                      /* Sender's hostname (resolved) */
 277   octet h[SHA_HASHSZ];                  /* Hash of the transmission buffer */
 278   sha_ctx hc;                           /* Hashing context */
 279   request rq;                           /* Request buffer for verification */
 280   ssize_t sz;                           /* Length of incoming message */
 281   socklen_t slen;                       /* Length of incoming address */
 282   uint32 u;                             /* Scratch integer */
 283   uint16 ul;                            /* And another */
 284   struct hostent *he;                   /* Resolve structure */
 285   mp *m, *k, *r, *s;                    /* Integers for signing */
 286   int ans;                              /* Answer from the check */
 287   buf b;                                /* Buffer for parsing request */
 288
 289   /* --- Kick some randomness in the pot --- */
 290
 291   noise_timer(RAND_GLOBAL);
 292
 293   /* --- Read the message --- */
 294
 295   slen = sizeof(sin);
 296   if ((sz = recvfrom(fd, (char *)buff, sizeof(buff), 0,
 297                      (struct sockaddr *)&sin, &slen)) < 0) {
 298     T( trace(TRACE_DAEMON, "daemon: error reading packet: %s",
 299              strerror(errno)); )
 300     syslog(LOG_INFO, "duff packet received: %e");
 301     return;
 302   }
 303
 304   /* --- Resolve the host name --- */
 305
 306   he = gethostbyaddr((char *)&sin.sin_addr, sizeof(sin.sin_addr), AF_INET);
 307   sender[0] = 0;
 308   strncat(sender, he ? he->h_name : inet_ntoa(sin.sin_addr),
 309           sizeof(sender) - 1);
 310   syslog(LOG_DEBUG, "packet received from %s", sender);
 311   T( trace(TRACE_DAEMON, "daemon: received request from %s", sender); )
 312
 313   /* --- Sanity check --- */
 314
 315   if (!daemon__keyfile) {
 316     syslog(LOG_NOTICE, "no key file: ignoring request");
 317     T( trace(TRACE_DAEMON, "daemon: no key file: ignoring request"); )
 318     return;
 319   }
 320
 321   /* --- Unpack the block --- */
 322
 323   rq.host = sin.sin_addr;
 324   buf_init(&b, buff, sz);
 325   if (buf_ensure(&b, SHA_HASHSZ)) goto fail;  BSTEP(&b, SHA_HASHSZ);
 326   if (buf_getu32(&b, &u)) goto fail;  rq.from = u;
 327   if (buf_getu32(&b, &u)) goto fail;  rq.to = u;
 328   if (buf_getu16(&b, &ul) || buf_ensure(&b, ul) || ul >= sizeof(rq.cmd))
 329     goto fail;
 330   memcpy(rq.cmd, BCUR(&b), ul);
 331   rq.cmd[ul] = 0;
 332   BSTEP(&b, ul);
 333   if (BLEFT(&b)) goto fail;
 334
 335   /* --- Hash the request block --- */
 336
 337   sha_init(&hc);
 338   sha_hash(&hc, buff, sz);
 339   sha_done(&hc, h);
 340
 341   /* --- Build a reply block --- */
 342
 343   ans = rule_check(&rq);
 344   syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s",
 345          sender, rq.from, rq.to, rq.cmd, ans ? "granted" : "denied");
 346   buf_init(&b, buff, sizeof(buff));
 347   if (buf_put(&b, h, sizeof(h)) || buf_putbyte(&b, ans))
 348     goto fail;
 349
 350   /* --- Sign the reply block --- */
 351
 352   sha_init(&hc);
 353   sha_hash(&hc, BBASE(&b), BLEN(&b));
 354   sha_done(&hc, h);
 355   m = mp_loadb(MP_NEW, h, sizeof(h));
 356   rand_get(RAND_GLOBAL, h, sizeof(h));
 357   k = mp_loadb(MP_NEWSEC, h, sizeof(h));
 358   r = s = MP_NEW;
 359   dsa_mksig(&daemon__key.dp, daemon__key.x, m, k, &r, &s);
 360   buf_putmp(&b, r);
 361   buf_putmp(&b, s);
 362   mp_drop(m);
 363   mp_drop(k);
 364   mp_drop(r);
 365   mp_drop(s);
 366   if (BBAD(&b))
 367     goto fail;
 368
 369   /* --- Send the reply off --- */
 370
 371   sendto(fd, BBASE(&b), BLEN(&b), 0, (struct sockaddr *)&sin, sizeof(sin));
 372   T( trace(TRACE_DAEMON, "daemon: reply sent"); )
 373   return;
 374
 375 fail:
 376   syslog(LOG_ERR, "couldn't respond to query");
 377   T( trace(TRACE_DAEMON, "daemon: failed to answer query"); )
 378 }
 379
 380 /* --- @daemon__die@ --- *
 381  *
 382  * Arguments:   @int n@ = signal number
 383  *              @void *p@ = ignored
 384  *
 385  * Returns:     Doesn't.
 386  *
 387  * Use:         Exits the daemon.
 388  */
 389
 390 static void daemon__die(int n, void *p)
 391 {
 392   T( trace(TRACE_DAEMON, "daemon: killed by signal %i", n); )
 393   syslog(LOG_NOTICE, "killed by signal type %i", n);
 394   remove(file_PID);
 395   exit(0);
 396 }
 397
 398 /* --- @daemon__setTimer@ --- *
 399  *
 400  * Arguments:   ---
 401  *
 402  * Returns:     ---
 403  *
 404  * Use:         Sets the interval timer up.
 405  */
 406
 407 static void daemon__wakeUp(struct timeval *tv, void *p);
 408
 409 static void daemon__setTimer(void)
 410 {
 411   struct timeval tv;
 412
 413   gettimeofday(&tv, 0);
 414   tv.tv_sec += daemon__awakeEvery;
 415   sel_addtimer(&daemon__sel, &daemon__timer, &tv, daemon__wakeUp, 0);
 416 }
 417
 418 /* --- @daemon__rescan@ --- *
 419  *
 420  * Arguments:   @int n@ = signal number
 421  *              @void *p@ = ignored
 422  *
 423  * Returns:     ---
 424  *
 425  * Use:         Forces a rescan of the daemon's configuration.
 426  */
 427
 428 static void daemon__rescan(int n, void *p)
 429 {
 430   syslog(LOG_INFO, "rescanning configuration file");
 431   name_end();
 432   rule_end();
 433   netg_end();
 434   userdb_end();
 435   dsa_privfree(&daemon__key);
 436   userdb_init();
 437   userdb_local();
 438   userdb_yp();
 439   netg_init();
 440   rule_init();
 441   name_init();
 442   if (daemon__readConfig(daemon__config))
 443     syslog(LOG_ERR, "error reading configuration file");
 444   sel_rmtimer(&daemon__timer);
 445   daemon__setTimer();
 446   fwatch_update(&daemon__cwatch, daemon__config);
 447   fwatch_update(&daemon__kwatch, daemon__keyfile);
 448 }
 449
 450 /* --- @daemon__wakeUp@ --- *
 451  *
 452  * Arguments:   @struct timeval *tv@ = ignored
 453  *              @void *p@ = ignored
 454  *
 455  * Returns:     ---
 456  *
 457  * Use:         Wakes up periodically to check the configuration file.
 458  */
 459
 460 static void daemon__wakeUp(struct timeval *tv, void *p)
 461 {
 462   T( trace(TRACE_DAEMON, "daemon: interval timer"); )
 463   rand_seed(RAND_GLOBAL, 160);
 464   daemon__setTimer();
 465   if (fwatch_update(&daemon__cwatch, daemon__config))
 466     daemon__rescan(0, 0);
 467   else if (fwatch_update(&daemon__kwatch, daemon__keyfile)) {
 468     const char *kf = daemon__keyfile;
 469     daemon__keyfile = 0;
 470     daemon_readKey(kf);
 471   }
 472 }
 473
 474 /* --- @daemon_init@ --- *
 475  *
 476  * Arguments:   @const char *cf@ = pointer to name of configuration file
 477  *              @int port@ = port to listen to, or %$-1$% for default
 478  *              @unsigned f@ = various flags
 479  *
 480  * Returns:     Never.
 481  *
 482  * Use:         Starts `become' up in daemon mode.
 483  */
 484
 485 void daemon_init(const char *cf, int port, unsigned f)
 486 {
 487   int s;
 488   int i;
 489
 490   static struct sigvec {
 491     int sig;
 492     void (*proc)(int n, void *p);
 493     sig s;
 494   } sigs[] = {
 495     { SIGHUP, daemon__rescan },
 496     { SIGINT, daemon__die },
 497     { SIGTERM, daemon__die },
 498     { SIGQUIT, daemon__die },
 499     { 0, 0 }
 500   };
 501
 502   /* --- Remove my root privileges --- *
 503    *
 504    * Just in case there's anything dodgy in my configuration file, or the
 505    * user wants me to start on a funny port.
 506    */
 507
 508   setuid(getuid());
 509
 510   /* --- Initialize the random number generator --- */
 511
 512   rand_noisesrc(RAND_GLOBAL, &noise_source);
 513   rand_seed(RAND_GLOBAL, 160);
 514
 515   /* --- Initialise bits of the program --- */
 516
 517   daemon__config = cf;
 518   daemon__port = port;
 519   sel_init(&daemon__sel);
 520   sig_init(&daemon__sel);
 521   userdb_init();
 522   userdb_local();
 523   userdb_yp();
 524   netg_init();
 525   name_init();
 526   rule_init();
 527   openlog(quis(), 0, LOG_DAEMON);
 528   syslog(LOG_NOTICE, "starting up");
 529
 530   if (daemon__readConfig(daemon__config))
 531     die(1, "couldn't read configuration file");
 532   fwatch_init(&daemon__cwatch, daemon__config);
 533   fwatch_init(&daemon__kwatch, daemon__keyfile);
 534
 535   /* --- Decide on a port to use --- *
 536    *
 537    * If I don't have a port yet (e.g., from the configuration file) then
 538    * look it up in /etc/services under whatever name I was started as.
 539    */
 540
 541   if (daemon__port == 0) {
 542     struct servent *se = getservbyname(quis(), "udp");
 543     if (se)
 544       daemon__port = se->s_port;
 545     else
 546       daemon__port = htons(SERVER_PORT);
 547   }
 548
 549   /* --- Now set up a socket --- */
 550
 551   {
 552     struct sockaddr_in sin;
 553
 554     if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
 555       die(1, "couldn't create socket: %s", strerror(errno));
 556     sin.sin_family = AF_INET;
 557     sin.sin_port = daemon__port;
 558     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 559     if (bind(s, (struct sockaddr *)&sin, sizeof(sin))) {
 560       die(1, "couldn't bind socket to port %i: %s",
 561           ntohs(daemon__port), strerror(errno));
 562     }
 563   }
 564
 565   /* --- Fork off into the sunset --- */
 566
 567   if (!(f & df_nofork)) {
 568     int pid = fork();
 569     FILE *fp;
 570
 571     /* --- Make a background process --- */
 572
 573     if (pid == -1)
 574       die(1, "couldn't fork daemon: %s", strerror(errno));
 575     else if (pid != 0)
 576       return;
 577
 578     /* --- Disconnect from the terminal --- */
 579
 580     setsid();
 581
 582     /* --- Write my process id to a file --- */
 583
 584     if ((fp = fopen(file_PID, "w")) != 0) {
 585       fprintf(fp, "%lu\n", (unsigned long)getpid());
 586       fclose(fp);
 587     }
 588     T( trace(TRACE_DAEMON, "daemon: forked to pid %li", (long)getpid()); )
 589   }
 590
 591   /* --- Set signal handlers --- */
 592
 593   for (i = 0; sigs[i].proc; i++)
 594     sig_add(&sigs[i].s, sigs[i].sig, sigs[i].proc, 0);
 595
 596   /* --- Set the timer for rescanning the file --- */
 597
 598   daemon__setTimer();
 599
 600   /* --- Watch for input --- */
 601
 602   sel_initfile(&daemon__sel, &daemon__listen, s, SEL_READ,
 603                daemon__read, 0);
 604   sel_addfile(&daemon__listen);
 605
 606   /* --- Now wait for something exciting to happen --- */
 607
 608   for (;;) {
 609     if (sel_select(&daemon__sel)) {
 610       if (errno == EINTR || errno == EAGAIN)
 611         continue;
 612       syslog(LOG_ERR, "error from select: %s", strerror(errno));
 613       exit(1);
 614     }
 615   }
 616 }
 617
 618 /*----- That's all, folks -------------------------------------------------*/