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

   1 /* -*-c-*-
   2  *
   3  * $Id: daemon.c,v 1.7.2.1 1997/09/26 09:08:05 mdw Exp $
   4  *
   5  * Running a `become' daemon
   6  *
   7  * (c) 1997 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 1.7.2.1  1997/09/26 09:08:05  mdw
  33  * Use the Blowfish encryption algorithm instead of IDEA.  This is partly
  34  * because I prefer Blowfish (without any particularly strong evidence) but
  35  * mainly because IDEA is patented and Blowfish isn't.
  36  *
  37  * Revision 1.7  1997/09/17 10:23:23  mdw
  38  * Fix a typo.  Port numbers are in network order now, so don't change them.
  39  *
  40  * Revision 1.6  1997/09/09 18:17:06  mdw
  41  * Allow default port to be given as a service name or port number.
  42  *
  43  * Revision 1.5  1997/08/20  16:17:10  mdw
  44  * More sensible restart routine: `_reinit' functions replaced by `_end' and
  45  * `_init' functions.
  46  *
  47  * Revision 1.4  1997/08/07 10:00:37  mdw
  48  * (Log entry for previous version is bogus.)  Read netgroups database.
  49  * Give up privileges permanently on startup.
  50  *
  51  * Revision 1.2  1997/08/04 10:24:21  mdw
  52  * Sources placed under CVS control.
  53  *
  54  * Revision 1.1  1997/07/21  13:47:50  mdw
  55  * Initial revision
  56  *
  57  */
  58
  59 /*----- Header files ------------------------------------------------------*/
  60
  61 /* --- ANSI headers --- */
  62
  63 #include <errno.h>
  64 #include <signal.h>
  65 #include <setjmp.h>
  66 #include <stdio.h>
  67 #include <stdlib.h>
  68 #include <string.h>
  69
  70 /* --- Unix headers --- */
  71
  72 #include <sys/types.h>
  73 #include <sys/time.h>
  74 #include <sys/socket.h>
  75
  76 #include <netinet/in.h>
  77
  78 #include <arpa/inet.h>
  79
  80 #include <netdb.h>
  81 #include <syslog.h>
  82 #include <unistd.h>
  83
  84 /* --- Local headers --- */
  85
  86 #include "become.h"
  87 #include "blowfish.h"
  88 #include "config.h"
  89 #include "crypt.h"
  90 #include "daemon.h"
  91 #include "lexer.h"
  92 #include "name.h"
  93 #include "netg.h"
  94 #include "parser.h"
  95 #include "rule.h"
  96 #include "tx.h"
  97 #include "userdb.h"
  98 #include "utils.h"
  99
 100 /*----- Arbitrary constants -----------------------------------------------*/
 101
 102 #define daemon__awakeEvery (30 * 60)    /* Awaken this often to rescan */
 103
 104 /*----- Static variables --------------------------------------------------*/
 105
 106 static int daemon__running = 0;         /* Am I running as a daemon? */
 107 static int daemon__port = -1;           /* No particular port yet */
 108 static volatile sig_atomic_t daemon__rescan = 0; /* Rescan as soon as poss */
 109 #define daemon__signum daemon__rescan   /* Alias for readbility */
 110 static int daemon__readKey = 0;         /* Have I read a key? */
 111 static unsigned char daemon__key[BLOWFISH_KEYSIZE]; /* Encryption key */
 112 static jmp_buf daemon__dieBuf;          /* Jump here to kill the daemon */
 113
 114 /*----- Main code ---------------------------------------------------------*/
 115
 116 /* --- @daemon_usePort@ --- *
 117  *
 118  * Arguments:   @int port@ = port to use, please
 119  *
 120  * Returns:     ---
 121  *
 122  * Use:         Instructs the daemon to listen to the given port.
 123  */
 124
 125 void daemon_usePort(int port)
 126 {
 127   daemon__port = port;
 128 }
 129
 130 /* --- @daemon_readKey@ --- *
 131  *
 132  * Arguments:   @const char *kf@ = name of file containing key
 133  *
 134  * Returns:     ---
 135  *
 136  * Use:         Instructs the daemon to read the named key file.
 137  */
 138
 139 void daemon_readKey(const char *kf)
 140 {
 141   FILE *fp;
 142
 143   if (!daemon__running)
 144     return;
 145
 146   if ((fp = fopen(kf, "r")) == 0) {
 147     syslog(LOG_WARNING, "couldn't read key file: %e");
 148     return;
 149   }
 150   tx_getBits(daemon__key, 128, fp);
 151   fclose(fp);
 152   daemon__readKey = 1;
 153   return;
 154 }
 155
 156 /* --- @daemon__readConfig@ --- *
 157  *
 158  * Arguments:   @const char *cf@ = pointer to configuration file to use
 159  *
 160  * Returns:     Zero if it worked, nonzero if it hurt...
 161  *
 162  * Use:         Reads the configuration file, and other things.
 163  */
 164
 165 static int daemon__readConfig(const char *cf)
 166 {
 167   FILE *fp;
 168
 169   daemon__readKey = 0;
 170   if ((fp = fopen(cf, "r")) == 0)
 171     return (-1);
 172   lexer_scan(fp);
 173   yyparse();
 174   fclose(fp);
 175   if (!daemon__readKey)
 176     daemon_readKey(file_KEY);
 177   daemon__rescan = 0;
 178   T( trace(TRACE_DAEMON, "daemon: read config file"); )
 179   return (0);
 180 }
 181
 182 /* --- @daemon__restart@ --- *
 183  *
 184  * Arguments:   @int sig@ = the signal number
 185  *
 186  * Returns:     ---
 187  *
 188  * Use:         Handles signals.  Causes the configuration file to be reread.
 189  */
 190
 191 static void daemon__restart(int sig)
 192 {
 193   daemon__rescan = 1;
 194   signal(sig, daemon__restart);
 195 }
 196
 197 /* --- @daemon__die@ --- *
 198  *
 199  * Arguments:   @int sig@ = the signal number
 200  *
 201  * Returns:     via @longjmp@
 202  *
 203  * Use:         Handles other signals.  Causes the daemon to die.
 204  */
 205
 206 static void daemon__die(int sig)
 207 {
 208   daemon__signum = sig;
 209   longjmp(daemon__dieBuf, 1);
 210 }
 211
 212 /* --- @daemon__read@ --- *
 213  *
 214  * Arguments:   @int fd@ = socket handle
 215  *
 216  * Returns:     ---
 217  *
 218  * Use:         Examines a buffer, and returns a response.
 219  */
 220
 221 void daemon__read(int fd)
 222 {
 223   unsigned char buff[65536];            /* Buffer for incoming packets */
 224   unsigned char rpl[crp_size];          /* Buffer for outgoing replies */
 225   struct sockaddr_in sin;               /* Address of packet sender */
 226   char sender[64];                      /* Sender's hostname (resolved) */
 227   unsigned char sk[BLOWFISH_KEYSIZE];   /* Session key for reply */
 228   request rq;                           /* Request buffer for verification */
 229
 230   /* --- Read the message --- */
 231
 232   {
 233     int slen = sizeof(sin);
 234
 235     if (recvfrom(fd, (char *)buff, sizeof(buff), 0,
 236                  (struct sockaddr *)&sin, &slen) < 0) {
 237       T( trace(TRACE_DAEMON, "daemon: error reading packet: %s",
 238                strerror(errno)); )
 239       syslog(LOG_INFO, "duff packet received: %e");
 240       return;
 241     }
 242   }
 243
 244   /* --- Resolve the host name --- */
 245
 246   {
 247     struct hostent *he = gethostbyaddr((char *)&sin.sin_addr,
 248                                        sizeof(sin.sin_addr),
 249                                        AF_INET);
 250     sender[0] = 0;
 251     strncat(sender,
 252             he ? he->h_name : inet_ntoa(sin.sin_addr),
 253             sizeof(sender));
 254     syslog(LOG_DEBUG, "packet received from %s", sender);
 255     T( trace(TRACE_DAEMON, "daemon: received request from %s", sender); )
 256   }
 257
 258   /* --- Unpack the block --- */
 259
 260   if (crypt_unpackRequest(&rq, buff, daemon__key, sk, rpl) == 0) {
 261     burn(buff);
 262     T( trace(TRACE_DAEMON, "daemon: received corrupt or invalid request"); )
 263     syslog(LOG_INFO, "packet from %s rejected", sender);
 264     return;
 265   }
 266   burn(buff);
 267
 268   /* --- Fill in the sender's address in the request block --- */
 269
 270   rq.host = sin.sin_addr;
 271
 272   /* --- Build a reply block --- */
 273
 274   {
 275     int answer = rule_check(&rq);
 276     syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s",
 277            sender, rq.from, rq.to, rq.cmd, answer ? "granted" : "denied");
 278     crypt_packReply(rpl, sk, answer);
 279     burn(sk);
 280   }
 281
 282   /* --- Send the reply off --- */
 283
 284   sendto(fd, (char *)rpl, crp_size, 0, (struct sockaddr *)&sin, sizeof(sin));
 285   T( trace(TRACE_DAEMON, "daemon: reply sent"); )
 286   burn(rpl);
 287 }
 288
 289 /* --- @daemon_init@ --- *
 290  *
 291  * Arguments:   @const char *cf@ = pointer to name of configuration file
 292  *              @int port@ = port to listen to, or %$-1$% for default
 293  *
 294  * Returns:     Never.
 295  *
 296  * Use:         Starts `become' up in daemon mode.
 297  */
 298
 299 void daemon_init(const char *cf, int port)
 300 {
 301   int s;
 302
 303   /* --- Remove my root privileges --- *
 304    *
 305    * Just in case there's anything dodgy in my configuration file, or the
 306    * user wants me to start on a funny port.
 307    */
 308
 309   setuid(getuid());
 310
 311   /* --- Initialise bits of the program --- */
 312
 313   daemon__running = 1;
 314   daemon__port = port;
 315   userdb_init();
 316   userdb_local();
 317   userdb_yp();
 318   netg_init();
 319   name_init();
 320   rule_init();
 321   openlog(quis(), 0, LOG_DAEMON);
 322   syslog(LOG_NOTICE, "starting up");
 323
 324   if (daemon__readConfig(cf))
 325     die("couldn't read configuration file");
 326
 327   /* --- Decide on a port to use --- *
 328    *
 329    * If I don't have a port yet (e.g., from the configuration file) then
 330    * look it up in /etc/services under whatever name I was started as.
 331    */
 332
 333   if (daemon__port == 0) {
 334     struct servent *se = getservbyname(quis(), "udp");
 335     if (!se)
 336       die("no idea which port to listen to");
 337     daemon__port = se->s_port;
 338   }
 339
 340   /* --- Now set up a socket --- */
 341
 342   {
 343     struct sockaddr_in sin;
 344
 345     if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
 346       die("couldn't create socket: %s", strerror(errno));
 347     sin.sin_family = AF_INET;
 348     sin.sin_port = daemon__port;
 349     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 350     if (bind(s, (struct sockaddr *)&sin, sizeof(sin))) {
 351       die("couldn't bind socket to port %i: %s",
 352           ntohs(daemon__port), strerror(errno));
 353     }
 354   }
 355
 356   /* --- Fork off into the sunset --- */
 357
 358 #ifdef NDEBUG
 359   {
 360     int pid = fork();
 361     FILE *fp;
 362
 363     /* --- Make a background process --- */
 364
 365     if (pid == -1)
 366       die("couldn't fork daemon: %s", strerror(errno));
 367     else if (pid != 0)
 368       return;
 369
 370     /* --- Disconnect from the terminal --- */
 371
 372     setsid();
 373
 374     /* --- Write my process id to a file --- */
 375
 376     if ((fp = fopen(file_PID, "w")) != 0) {
 377       fprintf(fp, "%lu\n", (unsigned long)getpid());
 378       fclose(fp);
 379     }
 380     T( trace(TRACE_DAEMON, "daemon: forked to pid %li", (long)getpid()); )
 381   }
 382 #endif
 383
 384   /* --- Program in daemon death mode --- */
 385
 386   if (setjmp(daemon__dieBuf)) {
 387 #ifdef TRACING
 388     if (daemon__signum == SIGQUIT && tracing() & TRACE_RULE) {
 389       T( rule_dump(); )
 390       signal(SIGQUIT, daemon__die);
 391     } else
 392 #endif
 393     {
 394       T( trace(TRACE_DAEMON, "daemon: killed by signal %i",
 395                daemon__signum); )
 396       syslog(LOG_NOTICE, "killed by signal type %i", daemon__signum);
 397       remove(file_PID);
 398       exit(0);
 399     }
 400   } else {
 401
 402     /* --- Set signal handlers --- */
 403
 404     signal(SIGHUP, daemon__restart);
 405     signal(SIGQUIT, daemon__die);
 406     signal(SIGINT, daemon__die);
 407     signal(SIGTERM, daemon__die);
 408     signal(SIGSEGV, daemon__die);
 409     signal(SIGFPE, daemon__die);
 410     signal(SIGBUS, daemon__die);
 411   }
 412
 413   /* --- Now wait for something exciting to happen --- *
 414    *
 415    * Actually, every so often (5 minutes, perhaps) I need to wake up and
 416    * rescan the users to see whether they've changed.  Time to play with
 417    * @select@.
 418    */
 419
 420   {
 421     time_t when;
 422
 423     /* --- Find when I am, and thus when I need to be awoken again --- */
 424
 425     when = time(0) + daemon__awakeEvery;
 426
 427     for (;;) {
 428       fd_set fds;
 429       int i;
 430
 431       /* --- Set up the file descriptor tables --- */
 432
 433       FD_ZERO(&fds);
 434       FD_SET(s, &fds);
 435
 436       /* --- Now wait for something interesting --- */
 437
 438       T( trace(TRACE_DAEMON, "daemon: waiting for requests"); )
 439       i = select(FD_SETSIZE, &fds, 0, 0, 0);
 440
 441       /* --- Now, see if I need to rescan the config --- */
 442
 443       if (daemon__rescan || time(0) - when > 0) {
 444         daemon__rescan = 0;
 445         syslog(LOG_INFO, "rescanning configuration file");
 446         name_end();
 447         rule_end();
 448         netg_end();
 449         userdb_end();
 450         userdb_init();
 451         userdb_local();
 452         userdb_yp();
 453         netg_init();
 454         rule_init();
 455         name_init();
 456         if (daemon__readConfig(cf))
 457           syslog(LOG_ERR, "error reading configuration file");
 458         when = time(0) + daemon__awakeEvery;
 459       }
 460
 461       /* --- Read the data from the request --- */
 462
 463       if (i > 0)
 464         daemon__read(s);
 465     }
 466   }
 467 }
 468
 469 /*----- That's all, folks -------------------------------------------------*/