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

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