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

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