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

   1 /* -*-c-*-
   2  *
   3  * $Id: daemon.c,v 1.9 1998/01/12 16:45:59 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 1.9  1998/01/12 16:45:59  mdw
  33  * Fix copyright date.
  34  *
  35  * Revision 1.8  1997/09/26 09:14:58  mdw
  36  * Merged blowfish branch into trunk.
  37  *
  38  * Revision 1.7.2.1  1997/09/26 09:08:05  mdw
  39  * Use the Blowfish encryption algorithm instead of IDEA.  This is partly
  40  * because I prefer Blowfish (without any particularly strong evidence) but
  41  * mainly because IDEA is patented and Blowfish isn't.
  42  *
  43  * Revision 1.7  1997/09/17 10:23:23  mdw
  44  * Fix a typo.  Port numbers are in network order now, so don't change them.
  45  *
  46  * Revision 1.6  1997/09/09 18:17:06  mdw
  47  * Allow default port to be given as a service name or port number.
  48  *
  49  * Revision 1.5  1997/08/20  16:17:10  mdw
  50  * More sensible restart routine: `_reinit' functions replaced by `_end' and
  51  * `_init' functions.
  52  *
  53  * Revision 1.4  1997/08/07 10:00:37  mdw
  54  * (Log entry for previous version is bogus.)  Read netgroups database.
  55  * Give up privileges permanently on startup.
  56  *
  57  * Revision 1.2  1997/08/04 10:24:21  mdw
  58  * Sources placed under CVS control.
  59  *
  60  * Revision 1.1  1997/07/21  13:47:50  mdw
  61  * Initial revision
  62  *
  63  */
  64
  65 /*----- Header files ------------------------------------------------------*/
  66
  67 /* --- ANSI headers --- */
  68
  69 #include <errno.h>
  70 #include <signal.h>
  71 #include <setjmp.h>
  72 #include <stdio.h>
  73 #include <stdlib.h>
  74 #include <string.h>
  75
  76 /* --- Unix headers --- */
  77
  78 #include <sys/types.h>
  79 #include <sys/time.h>
  80 #include <sys/socket.h>
  81
  82 #include <netinet/in.h>
  83
  84 #include <arpa/inet.h>
  85
  86 #include <netdb.h>
  87 #include <syslog.h>
  88 #include <unistd.h>
  89
  90 /* --- Local headers --- */
  91
  92 #include "become.h"
  93 #include "blowfish.h"
  94 #include "config.h"
  95 #include "crypt.h"
  96 #include "daemon.h"
  97 #include "lexer.h"
  98 #include "name.h"
  99 #include "netg.h"
 100 #include "parser.h"
 101 #include "rule.h"
 102 #include "tx.h"
 103 #include "userdb.h"
 104 #include "utils.h"
 105
 106 /*----- Arbitrary constants -----------------------------------------------*/
 107
 108 #define daemon__awakeEvery (30 * 60)    /* Awaken this often to rescan */
 109
 110 /*----- Static variables --------------------------------------------------*/
 111
 112 static int daemon__running = 0;         /* Am I running as a daemon? */
 113 static int daemon__port = -1;           /* No particular port yet */
 114 static volatile sig_atomic_t daemon__rescan = 0; /* Rescan as soon as poss */
 115 #define daemon__signum daemon__rescan   /* Alias for readbility */
 116 static int daemon__readKey = 0;         /* Have I read a key? */
 117 static unsigned char daemon__key[BLOWFISH_KEYSIZE]; /* Encryption key */
 118 static jmp_buf daemon__dieBuf;          /* Jump here to kill the daemon */
 119
 120 /*----- Main code ---------------------------------------------------------*/
 121
 122 /* --- @daemon_usePort@ --- *
 123  *
 124  * Arguments:   @int port@ = port to use, please
 125  *
 126  * Returns:     ---
 127  *
 128  * Use:         Instructs the daemon to listen to the given port.
 129  */
 130
 131 void daemon_usePort(int port)
 132 {
 133   daemon__port = port;
 134 }
 135
 136 /* --- @daemon_readKey@ --- *
 137  *
 138  * Arguments:   @const char *kf@ = name of file containing key
 139  *
 140  * Returns:     ---
 141  *
 142  * Use:         Instructs the daemon to read the named key file.
 143  */
 144
 145 void daemon_readKey(const char *kf)
 146 {
 147   FILE *fp;
 148
 149   if (!daemon__running)
 150     return;
 151
 152   if ((fp = fopen(kf, "r")) == 0) {
 153     syslog(LOG_WARNING, "couldn't read key file: %e");
 154     return;
 155   }
 156   tx_getBits(daemon__key, 128, fp);
 157   fclose(fp);
 158   daemon__readKey = 1;
 159   return;
 160 }
 161
 162 /* --- @daemon__readConfig@ --- *
 163  *
 164  * Arguments:   @const char *cf@ = pointer to configuration file to use
 165  *
 166  * Returns:     Zero if it worked, nonzero if it hurt...
 167  *
 168  * Use:         Reads the configuration file, and other things.
 169  */
 170
 171 static int daemon__readConfig(const char *cf)
 172 {
 173   FILE *fp;
 174
 175   daemon__readKey = 0;
 176   if ((fp = fopen(cf, "r")) == 0)
 177     return (-1);
 178   lexer_scan(fp);
 179   yyparse();
 180   fclose(fp);
 181   if (!daemon__readKey)
 182     daemon_readKey(file_KEY);
 183   daemon__rescan = 0;
 184   T( trace(TRACE_DAEMON, "daemon: read config file"); )
 185   return (0);
 186 }
 187
 188 /* --- @daemon__restart@ --- *
 189  *
 190  * Arguments:   @int sig@ = the signal number
 191  *
 192  * Returns:     ---
 193  *
 194  * Use:         Handles signals.  Causes the configuration file to be reread.
 195  */
 196
 197 static void daemon__restart(int sig)
 198 {
 199   daemon__rescan = 1;
 200   signal(sig, daemon__restart);
 201 }
 202
 203 /* --- @daemon__die@ --- *
 204  *
 205  * Arguments:   @int sig@ = the signal number
 206  *
 207  * Returns:     via @longjmp@
 208  *
 209  * Use:         Handles other signals.  Causes the daemon to die.
 210  */
 211
 212 static void daemon__die(int sig)
 213 {
 214   daemon__signum = sig;
 215   longjmp(daemon__dieBuf, 1);
 216 }
 217
 218 /* --- @daemon__read@ --- *
 219  *
 220  * Arguments:   @int fd@ = socket handle
 221  *
 222  * Returns:     ---
 223  *
 224  * Use:         Examines a buffer, and returns a response.
 225  */
 226
 227 void daemon__read(int fd)
 228 {
 229   unsigned char buff[65536];            /* Buffer for incoming packets */
 230   unsigned char rpl[crp_size];          /* Buffer for outgoing replies */
 231   struct sockaddr_in sin;               /* Address of packet sender */
 232   char sender[64];                      /* Sender's hostname (resolved) */
 233   unsigned char sk[BLOWFISH_KEYSIZE];   /* Session key for reply */
 234   request rq;                           /* Request buffer for verification */
 235
 236   /* --- Read the message --- */
 237
 238   {
 239     int slen = sizeof(sin);
 240
 241     if (recvfrom(fd, (char *)buff, sizeof(buff), 0,
 242                  (struct sockaddr *)&sin, &slen) < 0) {
 243       T( trace(TRACE_DAEMON, "daemon: error reading packet: %s",
 244                strerror(errno)); )
 245       syslog(LOG_INFO, "duff packet received: %e");
 246       return;
 247     }
 248   }
 249
 250   /* --- Resolve the host name --- */
 251
 252   {
 253     struct hostent *he = gethostbyaddr((char *)&sin.sin_addr,
 254                                        sizeof(sin.sin_addr),
 255                                        AF_INET);
 256     sender[0] = 0;
 257     strncat(sender,
 258             he ? he->h_name : inet_ntoa(sin.sin_addr),
 259             sizeof(sender));
 260     syslog(LOG_DEBUG, "packet received from %s", sender);
 261     T( trace(TRACE_DAEMON, "daemon: received request from %s", sender); )
 262   }
 263
 264   /* --- Unpack the block --- */
 265
 266   if (crypt_unpackRequest(&rq, buff, daemon__key, sk, rpl) == 0) {
 267     burn(buff);
 268     T( trace(TRACE_DAEMON, "daemon: received corrupt or invalid request"); )
 269     syslog(LOG_INFO, "packet from %s rejected", sender);
 270     return;
 271   }
 272   burn(buff);
 273
 274   /* --- Fill in the sender's address in the request block --- */
 275
 276   rq.host = sin.sin_addr;
 277
 278   /* --- Build a reply block --- */
 279
 280   {
 281     int answer = rule_check(&rq);
 282     syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s",
 283            sender, rq.from, rq.to, rq.cmd, answer ? "granted" : "denied");
 284     crypt_packReply(rpl, sk, answer);
 285     burn(sk);
 286   }
 287
 288   /* --- Send the reply off --- */
 289
 290   sendto(fd, (char *)rpl, crp_size, 0, (struct sockaddr *)&sin, sizeof(sin));
 291   T( trace(TRACE_DAEMON, "daemon: reply sent"); )
 292   burn(rpl);
 293 }
 294
 295 /* --- @daemon_init@ --- *
 296  *
 297  * Arguments:   @const char *cf@ = pointer to name of configuration file
 298  *              @int port@ = port to listen to, or %$-1$% for default
 299  *
 300  * Returns:     Never.
 301  *
 302  * Use:         Starts `become' up in daemon mode.
 303  */
 304
 305 void daemon_init(const char *cf, int port)
 306 {
 307   int s;
 308
 309   /* --- Remove my root privileges --- *
 310    *
 311    * Just in case there's anything dodgy in my configuration file, or the
 312    * user wants me to start on a funny port.
 313    */
 314
 315   setuid(getuid());
 316
 317   /* --- Initialise bits of the program --- */
 318
 319   daemon__running = 1;
 320   daemon__port = port;
 321   userdb_init();
 322   userdb_local();
 323   userdb_yp();
 324   netg_init();
 325   name_init();
 326   rule_init();
 327   openlog(quis(), 0, LOG_DAEMON);
 328   syslog(LOG_NOTICE, "starting up");
 329
 330   if (daemon__readConfig(cf))
 331     die("couldn't read configuration file");
 332
 333   /* --- Decide on a port to use --- *
 334    *
 335    * If I don't have a port yet (e.g., from the configuration file) then
 336    * look it up in /etc/services under whatever name I was started as.
 337    */
 338
 339   if (daemon__port == 0) {
 340     struct servent *se = getservbyname(quis(), "udp");
 341     if (!se)
 342       die("no idea which port to listen to");
 343     daemon__port = se->s_port;
 344   }
 345
 346   /* --- Now set up a socket --- */
 347
 348   {
 349     struct sockaddr_in sin;
 350
 351     if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
 352       die("couldn't create socket: %s", strerror(errno));
 353     sin.sin_family = AF_INET;
 354     sin.sin_port = daemon__port;
 355     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 356     if (bind(s, (struct sockaddr *)&sin, sizeof(sin))) {
 357       die("couldn't bind socket to port %i: %s",
 358           ntohs(daemon__port), strerror(errno));
 359     }
 360   }
 361
 362   /* --- Fork off into the sunset --- */
 363
 364 #ifdef NDEBUG
 365   {
 366     int pid = fork();
 367     FILE *fp;
 368
 369     /* --- Make a background process --- */
 370
 371     if (pid == -1)
 372       die("couldn't fork daemon: %s", strerror(errno));
 373     else if (pid != 0)
 374       return;
 375
 376     /* --- Disconnect from the terminal --- */
 377
 378     setsid();
 379
 380     /* --- Write my process id to a file --- */
 381
 382     if ((fp = fopen(file_PID, "w")) != 0) {
 383       fprintf(fp, "%lu\n", (unsigned long)getpid());
 384       fclose(fp);
 385     }
 386     T( trace(TRACE_DAEMON, "daemon: forked to pid %li", (long)getpid()); )
 387   }
 388 #endif
 389
 390   /* --- Program in daemon death mode --- */
 391
 392   if (setjmp(daemon__dieBuf)) {
 393 #ifdef TRACING
 394     if (daemon__signum == SIGQUIT && tracing() & TRACE_RULE) {
 395       T( rule_dump(); )
 396       signal(SIGQUIT, daemon__die);
 397     } else
 398 #endif
 399     {
 400       T( trace(TRACE_DAEMON, "daemon: killed by signal %i",
 401                daemon__signum); )
 402       syslog(LOG_NOTICE, "killed by signal type %i", daemon__signum);
 403       remove(file_PID);
 404       exit(0);
 405     }
 406   } else {
 407
 408     /* --- Set signal handlers --- */
 409
 410     signal(SIGHUP, daemon__restart);
 411     signal(SIGQUIT, daemon__die);
 412     signal(SIGINT, daemon__die);
 413     signal(SIGTERM, daemon__die);
 414     signal(SIGSEGV, daemon__die);
 415     signal(SIGFPE, daemon__die);
 416     signal(SIGBUS, daemon__die);
 417   }
 418
 419   /* --- Now wait for something exciting to happen --- *
 420    *
 421    * Actually, every so often (5 minutes, perhaps) I need to wake up and
 422    * rescan the users to see whether they've changed.  Time to play with
 423    * @select@.
 424    */
 425
 426   {
 427     time_t when;
 428
 429     /* --- Find when I am, and thus when I need to be awoken again --- */
 430
 431     when = time(0) + daemon__awakeEvery;
 432
 433     for (;;) {
 434       fd_set fds;
 435       int i;
 436
 437       /* --- Set up the file descriptor tables --- */
 438
 439       FD_ZERO(&fds);
 440       FD_SET(s, &fds);
 441
 442       /* --- Now wait for something interesting --- */
 443
 444       T( trace(TRACE_DAEMON, "daemon: waiting for requests"); )
 445       i = select(FD_SETSIZE, &fds, 0, 0, 0);
 446
 447       /* --- Now, see if I need to rescan the config --- */
 448
 449       if (daemon__rescan || time(0) - when > 0) {
 450         daemon__rescan = 0;
 451         syslog(LOG_INFO, "rescanning configuration file");
 452         name_end();
 453         rule_end();
 454         netg_end();
 455         userdb_end();
 456         userdb_init();
 457         userdb_local();
 458         userdb_yp();
 459         netg_init();
 460         rule_init();
 461         name_init();
 462         if (daemon__readConfig(cf))
 463           syslog(LOG_ERR, "error reading configuration file");
 464         when = time(0) + daemon__awakeEvery;
 465       }
 466
 467       /* --- Read the data from the request --- */
 468
 469       if (i > 0)
 470         daemon__read(s);
 471     }
 472   }
 473 }
 474
 475 /*----- That's all, folks -------------------------------------------------*/