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

   1 /* -*-c-*-
   2  *
   3  * $Id: daemon.c,v 1.1 1997/07/21 13:47:50 mdw Exp $
   4  *
   5  * Running a `become' daemon
   6  *
   7  * (c) 1997 EBI
   8  */
   9
  10 /*----- Licencing 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
  26  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  27  */
  28
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: daemon.c,v $
  32  * Revision 1.1  1997/07/21 13:47:50  mdw
  33  * Initial revision
  34  *
  35  */
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 /* --- ANSI headers --- */
  40
  41 #include <errno.h>
  42 #include <signal.h>
  43 #include <setjmp.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47
  48 /* --- Unix headers --- */
  49
  50 #include <sys/types.h>
  51 #include <sys/time.h>
  52 #include <sys/socket.h>
  53
  54 #include <netinet/in.h>
  55
  56 #include <arpa/inet.h>
  57
  58 #include <netdb.h>
  59 #include <syslog.h>
  60 #include <unistd.h>
  61
  62 /* --- Local headers --- */
  63
  64 #include "become.h"
  65 #include "config.h"
  66 #include "crypt.h"
  67 #include "daemon.h"
  68 #include "idea.h"
  69 #include "lexer.h"
  70 #include "name.h"
  71 #include "parser.h"
  72 #include "rule.h"
  73 #include "tx.h"
  74 #include "userdb.h"
  75 #include "utils.h"
  76
  77 /*----- Arbitrary constants -----------------------------------------------*/
  78
  79 #define daemon__awakeEvery (5 * 60)     /* Awaken this often to rescan */
  80
  81 /*----- Static variables --------------------------------------------------*/
  82
  83 static int daemon__running = 0;         /* Am I running as a daemon? */
  84 static int daemon__port = -1;           /* No particular port yet */
  85 static volatile sig_atomic_t daemon__rescan = 0; /* Rescan as soon as poss */
  86 #define daemon__signum daemon__rescan   /* Alias for readbility */
  87 static int daemon__readKey = 0;         /* Have I read a key? */
  88 static unsigned char daemon__key[IDEA_KEYSIZE]; /* encryption key */
  89 static jmp_buf daemon__dieBuf;          /* Jump here to kill the daemon */
  90
  91 /*----- Main code ---------------------------------------------------------*/
  92
  93 /* --- @daemon_usePort@ --- *
  94  *
  95  * Arguments:   @int port@ = port to use, please
  96  *
  97  * Returns:     ---
  98  *
  99  * Use:         Instructs the daemon to listen to the given port.
 100  */
 101
 102 void daemon_usePort(int port)
 103 {
 104   daemon__port = port;
 105 }
 106
 107 /* --- @daemon_readKey@ --- *
 108  *
 109  * Arguments:   @const char *kf@ = name of file containing key
 110  *
 111  * Returns:     ---
 112  *
 113  * Use:         Instructs the daemon to read the named key file.
 114  */
 115
 116 void daemon_readKey(const char *kf)
 117 {
 118   FILE *fp;
 119
 120   if (!daemon__running)
 121     return;
 122
 123   if ((fp = fopen(kf, "r")) == 0) {
 124     syslog(LOG_WARNING, "couldn't read key file: %e");
 125     return;
 126   }
 127   tx_getBits(daemon__key, 128, fp);
 128   fclose(fp);
 129   daemon__readKey = 1;
 130   return;
 131 }
 132
 133 /* --- @daemon__readConfig@ --- *
 134  *
 135  * Arguments:   @const char *cf@ = pointer to configuration file to use
 136  *
 137  * Returns:     Zero if it worked, nonzero if it hurt...
 138  *
 139  * Use:         Reads the configuration file, and other things.
 140  */
 141
 142 static int daemon__readConfig(const char *cf)
 143 {
 144   FILE *fp;
 145
 146   daemon__readKey = 0;
 147   if ((fp = fopen(cf, "r")) == 0)
 148     return (-1);
 149   lexer_scan(fp);
 150   yyparse();
 151   fclose(fp);
 152   if (!daemon__readKey)
 153     daemon_readKey(file_KEY);
 154   daemon__rescan = 0;
 155   return (0);
 156 }
 157
 158 /* --- @daemon__restart@ --- *
 159  *
 160  * Arguments:   @int sig@ = the signal number
 161  *
 162  * Returns:     ---
 163  *
 164  * Use:         Handles signals.  Causes the configuration file to be reread.
 165  */
 166
 167 static void daemon__restart(int sig)
 168 {
 169   daemon__rescan = 1;
 170   signal(sig, daemon__restart);
 171 }
 172
 173 /* --- @daemon__die@ --- *
 174  *
 175  * Arguments:   @int sig@ = the signal number
 176  *
 177  * Returns:     via @longjmp@
 178  *
 179  * Use:         Handles other signals.  Causes the daemon to die.
 180  */
 181
 182 static void daemon__die(int sig)
 183 {
 184   daemon__signum = sig;
 185   longjmp(daemon__dieBuf, 1);
 186 }
 187
 188 /* --- @daemon__read@ --- *
 189  *
 190  * Arguments:   @int fd@ = socket handle
 191  *
 192  * Returns:     ---
 193  *
 194  * Use:         Examines a buffer, and returns a response.
 195  */
 196
 197 void daemon__read(int fd)
 198 {
 199   unsigned char buff[65536];            /* Buffer for incoming packets */
 200   unsigned char rpl[crp_size];          /* Buffer for outgoing replies */
 201   struct sockaddr_in sin;               /* Address of packet sender */
 202   char sender[64];                      /* Sender's hostname (resolved) */
 203   unsigned char sk[IDEA_KEYSIZE];       /* Session key for reply */
 204   request rq;                           /* Request buffer for verification */
 205
 206   /* --- Read the message --- */
 207
 208   {
 209     int slen = sizeof(sin);
 210
 211     if (recvfrom(fd, (char *)buff, sizeof(buff), 0,
 212                  (struct sockaddr *)&sin, &slen) < 0) {
 213       syslog(LOG_INFO, "duff packet received: %e");
 214       return;
 215     }
 216   }
 217
 218   /* --- Resolve the host name --- */
 219
 220   {
 221     struct hostent *he = gethostbyaddr((char *)&sin.sin_addr,
 222                                        sizeof(sin.sin_addr),
 223                                        AF_INET);
 224     sender[0] = 0;
 225     strncat(sender,
 226             he ? he->h_name : inet_ntoa(sin.sin_addr),
 227             sizeof(sender));
 228     syslog(LOG_DEBUG, "packet received from %s", sender);
 229   }
 230
 231   /* --- Unpack the block --- */
 232
 233   if (crypt_unpackRequest(&rq, buff, daemon__key, sk, rpl) == 0) {
 234     burn(buff);
 235     syslog(LOG_INFO, "packet from %s rejected", sender);
 236     return;
 237   }
 238   burn(buff);
 239
 240   /* --- Fill in the sender's address in the request block --- */
 241
 242   rq.host = sin.sin_addr;
 243
 244   /* --- Build a reply block --- */
 245
 246   {
 247     int answer = rule_check(&rq);
 248     syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s",
 249            sender, rq.from, rq.to, rq.cmd, answer ? "granted" : "denied");
 250     crypt_packReply(rpl, sk, answer);
 251     burn(sk);
 252   }
 253
 254   /* --- Send the reply off --- */
 255
 256   sendto(fd, (char *)rpl, crp_size, 0, (struct sockaddr *)&sin, sizeof(sin));
 257   burn(rpl);
 258 }
 259
 260 /* --- @daemon_init@ --- *
 261  *
 262  * Arguments:   @const char *cf@ = pointer to name of configuration file
 263  *              @int port@ = port to listen to, or %$-1$% for default
 264  *
 265  * Returns:     Never.
 266  *
 267  * Use:         Starts `become' up in daemon mode.
 268  */
 269
 270 void daemon_init(const char *cf, int port)
 271 {
 272   int s;
 273
 274   /* --- Remove my root privileges --- *
 275    *
 276    * Just in case there's anything dodgy in my configuration file, or the
 277    * user wants me to start on a funny port.
 278    */
 279
 280   seteuid(getuid());
 281
 282   /* --- Initialise bits of the program --- */
 283
 284   daemon__running = 1;
 285   daemon__port = port;
 286   userdb_init();
 287   userdb_local();
 288   userdb_yp();
 289   name_init();
 290   rule_init();
 291   openlog(quis(), 0, LOG_DAEMON);
 292   syslog(LOG_NOTICE, "starting up");
 293
 294   if (daemon__readConfig(cf))
 295     die("couldn't read configuration file");
 296
 297   /* --- Decide on a port to use --- *
 298    *
 299    * If I don't have a port yet (e.g., from the configuration file) then
 300    * look it up in /etc/services under whatever name I was started as.
 301    */
 302
 303   if (daemon__port <= 0) {
 304     struct servent *se = getservbyname(quis(), "udp");
 305     if (!se)
 306       die("no idea which port to use");
 307     daemon__port = ntohs(se->s_port);
 308   }
 309
 310   /* --- Now set up a socket --- */
 311
 312   {
 313     struct sockaddr_in sin;
 314
 315     if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
 316       die("couldn't create socket: %s", strerror(errno));
 317     sin.sin_family = AF_INET;
 318     sin.sin_port = htons(daemon__port);
 319     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 320     if (bind(s, (struct sockaddr *)&sin, sizeof(sin)))
 321       die("couldn't bind socket to port: %s", strerror(errno));
 322   }
 323
 324   /* --- Fork off into the sunset --- */
 325
 326 #ifdef NDEBUG
 327   {
 328     int pid = fork();
 329     FILE *fp;
 330
 331     /* --- Make a background process --- */
 332
 333     if (pid == -1)
 334       die("couldn't fork daemon: %s", strerror(errno));
 335     else if (pid != 0)
 336       return;
 337
 338     /* --- Disconnect from the terminal --- */
 339
 340     setsid();
 341
 342     /* --- Write my process id to a file --- */
 343
 344     if ((fp = fopen(file_PID, "w")) != 0) {
 345       fprintf(fp, "%lu\n", (unsigned long)getpid());
 346       fclose(fp);
 347     }
 348   }
 349 #endif
 350
 351   /* --- Program in daemon death mode --- */
 352
 353   if (setjmp(daemon__dieBuf)) {
 354     syslog(LOG_NOTICE, "killed by signal type %i", daemon__signum);
 355     remove(file_PID);
 356     exit(0);
 357   }
 358
 359   /* --- Set signal handlers --- */
 360
 361   signal(SIGHUP, daemon__restart);
 362   signal(SIGQUIT, daemon__restart);
 363   signal(SIGINT, daemon__die);
 364   signal(SIGTERM, daemon__die);
 365   signal(SIGSEGV, daemon__die);
 366   signal(SIGFPE, daemon__die);
 367   signal(SIGBUS, daemon__die);
 368
 369   /* --- Now wait for something exciting to happen --- *
 370    *
 371    * Actually, every so often (5 minutes, perhaps) I need to wake up and
 372    * rescan the users to see whether they've changed.  Time to play with
 373    * @select@.
 374    */
 375
 376   {
 377     time_t when;
 378
 379     /* --- Find when I am, and thus when I need to be awoken again --- */
 380
 381     when = time(0) + daemon__awakeEvery;
 382
 383     for (;;) {
 384       fd_set fds;
 385       int i;
 386
 387       /* --- Set up the file descriptor tables --- */
 388
 389       FD_ZERO(&fds);
 390       FD_SET(s, &fds);
 391
 392       /* --- Now wait for something interesting --- */
 393
 394       i = select(FD_SETSIZE, &fds, 0, 0, 0);
 395
 396       /* --- Now, see if I need to rescan the config --- */
 397
 398       if (daemon__rescan || time(0) - when > 0) {
 399         daemon__rescan = 0;
 400         syslog(LOG_INFO, "rescanning configuration file");
 401         userdb_reinit();
 402         userdb_local();
 403         userdb_yp();
 404         rule_reinit();
 405         name_reinit();
 406         if (daemon__readConfig(cf))
 407           syslog(LOG_ERR, "error reading configuration file");
 408         when = time(0) + daemon__awakeEvery;
 409       }
 410
 411       /* --- Read the data from the request --- */
 412
 413       if (i > 0)
 414         daemon__read(s);
 415     }
 416   }
 417 }
 418
 419 /*----- That's all, folks -------------------------------------------------*/