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

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