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

   1 /* -*-c-*-
   2  *
   3  * $Id: daemon.c,v 1.17 2004/04/08 01:36:20 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 /*----- Header files ------------------------------------------------------*/
  30
  31 /* --- ANSI headers --- */
  32
  33 #include <errno.h>
  34 #include <signal.h>
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38
  39 /* --- Unix headers --- */
  40
  41 #include <sys/types.h>
  42 #include <sys/time.h>
  43 #include <sys/socket.h>
  44
  45 #include <netinet/in.h>
  46
  47 #include <arpa/inet.h>
  48
  49 #include <netdb.h>
  50 #include <syslog.h>
  51 #include <unistd.h>
  52
  53 /* --- mLib headers --- */
  54
  55 #include <mLib/fwatch.h>
  56 #include <mLib/quis.h>
  57 #include <mLib/report.h>
  58 #include <mLib/sel.h>
  59 #include <mLib/sig.h>
  60 #include <mLib/sym.h>
  61 #include <mLib/trace.h>
  62
  63 /* --- Catacomb headers --- */
  64
  65 #include <catacomb/buf.h>
  66 #include <catacomb/dsa.h>
  67 #include <catacomb/key.h>
  68 #include <catacomb/mp.h>
  69 #include <catacomb/noise.h>
  70 #include <catacomb/paranoia.h>
  71 #include <catacomb/rand.h>
  72 #include <catacomb/sha.h>
  73
  74 /* --- Local headers --- */
  75
  76 #include "become.h"
  77 #include "config.h"
  78 #include "daemon.h"
  79 #include "lexer.h"
  80 #include "name.h"
  81 #include "netg.h"
  82 #include "parse.h"
  83 #include "rule.h"
  84 #include "userdb.h"
  85
  86 /*----- Arbitrary constants -----------------------------------------------*/
  87
  88 #define daemon__awakeEvery (10)         /* Awaken this often to rescan */
  89
  90 /*----- Static variables --------------------------------------------------*/
  91
  92 static int daemon__port = -1;           /* No particular port yet */
  93 static fwatch daemon__cwatch, daemon__kwatch; /* Watching key/config files */
  94 static sel_timer daemon__timer;         /* Timer for reading */
  95 static sel_state daemon__sel;           /* Select context */
  96 static sel_file daemon__listen;         /* Listening socket selector */
  97 static const char *daemon__config;      /* Configuration file for daemon */
  98 static const char *daemon__keyfile;     /* Keyring file for daemon */
  99 static dsa_priv daemon__key;            /* The key data */
 100
 101 /*----- Main code ---------------------------------------------------------*/
 102
 103 /* --- @daemon_usePort@ --- *
 104  *
 105  * Arguments:   @int port@ = port to use, please
 106  *
 107  * Returns:     ---
 108  *
 109  * Use:         Instructs the daemon to listen to the given port.
 110  */
 111
 112 void daemon_usePort(int port)
 113 {
 114   daemon__port = port;
 115 }
 116
 117 /* --- @daemon__moan@ --- *
 118  *
 119  * Arguments:   @const char *f@ = offending file name
 120  *              @int line@ = offending line of the file
 121  *              @const char *msg@ = message
 122  *              @void *p@ = ignored
 123  *
 124  * Returns:     ---
 125  *
 126  * Use:         Reports an error message about a key file.
 127  */
 128
 129 static void daemon__moan(const char *f, int line, const char *msg, void *p)
 130 {
 131   syslog(LOG_ERR, "key file error: %s: %d: %s", f, line, msg);
 132   T( trace(TRACE_DAEMON, "daemon: key file error: %s: %d: %s",
 133            f, line, msg); )
 134 }
 135
 136 /* --- @daemon_readKey@ --- *
 137  *
 138  * Arguments:   @const char *kf@ = pointer to key file name to use
 139  *
 140  * Returns:     ---
 141  *
 142  * Use:         Loads the private key from the key file.
 143  */
 144
 145 void daemon_readKey(const char *kf)
 146 {
 147   key_packstruct kps[DSA_PRIVFETCHSZ];
 148   key_packdef *kp;
 149   key_file f;
 150   key *k;
 151   int err;
 152
 153   if (daemon__keyfile)
 154     return;
 155   T( trace(TRACE_DAEMON, "daemon: reading key from `%s'", kf); )
 156   if (key_open(&f, kf, KOPEN_READ, daemon__moan, 0))
 157     return;
 158   kp = key_fetchinit(dsa_privfetch, kps, &daemon__key);
 159   if ((k = key_bytype(&f, "become-dsa")) == 0)
 160     err = KERR_NOTFOUND;
 161   else
 162     err = key_fetch(kp, k);
 163   if (err)
 164     syslog(LOG_ERR, "couldn't load key: %s", key_strerror(err));
 165   else {
 166     mp_copy(daemon__key.dp.p);
 167     mp_copy(daemon__key.dp.q);
 168     mp_copy(daemon__key.dp.g);
 169     mp_copy(daemon__key.x);
 170     mp_copy(daemon__key.y);
 171     daemon__keyfile = kf;
 172   }
 173   key_fetchdone(kp);
 174   key_close(&f);
 175 }
 176
 177 /* --- @daemon__readConfig@ --- *
 178  *
 179  * Arguments:   @const char *cf@ = pointer to configuration file to use
 180  *
 181  * Returns:     Zero if it worked, nonzero if it hurt...
 182  *
 183  * Use:         Reads the configuration file, and other things.
 184  */
 185
 186 static int daemon__readConfig(const char *cf)
 187 {
 188   FILE *fp;
 189
 190   daemon__keyfile = 0;
 191   if ((fp = fopen(cf, "r")) == 0)
 192     return (-1);
 193   lexer_scan(fp);
 194   parse();
 195   fclose(fp);
 196   if (!daemon__keyfile)
 197     daemon_readKey(file_KEY);
 198   T( trace(TRACE_DAEMON, "daemon: read config file"); )
 199   return (0);
 200 }
 201
 202 /* --- @daemon__read@ --- *
 203  *
 204  * Arguments:   @int fd@ = socket handle
 205  *              @unsigned mode@ = ignored
 206  *              @void *p@ = ignored
 207  *
 208  * Returns:     ---
 209  *
 210  * Use:         Examines a buffer, and returns a response.
 211  */
 212
 213 void daemon__read(int fd, unsigned mode, void *p)
 214 {
 215   unsigned char buff[65536];            /* Buffer for incoming packets */
 216   struct sockaddr_in sin;               /* Address of packet sender */
 217   char sender[64];                      /* Sender's hostname (resolved) */
 218   octet h[SHA_HASHSZ];                  /* Hash of the transmission buffer */
 219   sha_ctx hc;                           /* Hashing context */
 220   request rq;                           /* Request buffer for verification */
 221   ssize_t sz;                           /* Length of incoming message */
 222   socklen_t slen;                       /* Length of incoming address */
 223   uint32 u;                             /* Scratch integer */
 224   uint16 ul;                            /* And another */
 225   struct hostent *he;                   /* Resolve structure */
 226   mp *m, *k, *r, *s;                    /* Integers for signing */
 227   int ans;                              /* Answer from the check */
 228   buf b;                                /* Buffer for parsing request */
 229
 230   /* --- Kick some randomness in the pot --- */
 231
 232   noise_timer(RAND_GLOBAL);
 233
 234   /* --- Read the message --- */
 235
 236   slen = sizeof(sin);
 237   if ((sz = recvfrom(fd, (char *)buff, sizeof(buff), 0,
 238                      (struct sockaddr *)&sin, &slen)) < 0) {
 239     T( trace(TRACE_DAEMON, "daemon: error reading packet: %s",
 240              strerror(errno)); )
 241     syslog(LOG_INFO, "duff packet received: %e");
 242     return;
 243   }
 244
 245   /* --- Resolve the host name --- */
 246
 247   he = gethostbyaddr((char *)&sin.sin_addr, sizeof(sin.sin_addr), AF_INET);
 248   sender[0] = 0;
 249   strncat(sender, he ? he->h_name : inet_ntoa(sin.sin_addr),
 250           sizeof(sender) - 1);
 251   syslog(LOG_DEBUG, "packet received from %s", sender);
 252   T( trace(TRACE_DAEMON, "daemon: received request from %s", sender); )
 253
 254   /* --- Sanity check --- */
 255
 256   if (!daemon__keyfile) {
 257     syslog(LOG_NOTICE, "no key file: ignoring request");
 258     T( trace(TRACE_DAEMON, "daemon: no key file: ignoring request"); )
 259     return;
 260   }
 261
 262   /* --- Unpack the block --- */
 263
 264   rq.host = sin.sin_addr;
 265   buf_init(&b, buff, sz);
 266   if (buf_ensure(&b, SHA_HASHSZ)) goto fail;  BSTEP(&b, SHA_HASHSZ);
 267   if (buf_getu32(&b, &u)) goto fail;  rq.from = u;
 268   if (buf_getu32(&b, &u)) goto fail;  rq.to = u;
 269   if (buf_getu16(&b, &ul) || buf_ensure(&b, ul) || ul >= sizeof(rq.cmd))
 270     goto fail;
 271   memcpy(rq.cmd, BCUR(&b), ul);
 272   rq.cmd[ul] = 0;
 273   BSTEP(&b, ul);
 274   if (BLEFT(&b)) goto fail;
 275
 276   /* --- Hash the request block --- */
 277
 278   sha_init(&hc);
 279   sha_hash(&hc, buff, sz);
 280   sha_done(&hc, h);
 281
 282   /* --- Build a reply block --- */
 283
 284   ans = rule_check(&rq);
 285   syslog(LOG_INFO, "request from %s for %i to become %i to run %s %s",
 286          sender, rq.from, rq.to, rq.cmd, ans ? "granted" : "denied");
 287   buf_init(&b, buff, sizeof(buff));
 288   if (buf_put(&b, h, sizeof(h)) || buf_putbyte(&b, ans))
 289     goto fail;
 290
 291   /* --- Sign the reply block --- */
 292
 293   sha_init(&hc);
 294   sha_hash(&hc, BBASE(&b), BLEN(&b));
 295   sha_done(&hc, h);
 296   m = mp_loadb(MP_NEW, h, sizeof(h));
 297   rand_get(RAND_GLOBAL, h, sizeof(h));
 298   k = mp_loadb(MP_NEWSEC, h, sizeof(h));
 299   r = s = MP_NEW;
 300   dsa_mksig(&daemon__key.dp, daemon__key.x, m, k, &r, &s);
 301   buf_putmp(&b, r);
 302   buf_putmp(&b, s);
 303   mp_drop(m);
 304   mp_drop(k);
 305   mp_drop(r);
 306   mp_drop(s);
 307   if (BBAD(&b))
 308     goto fail;
 309
 310   /* --- Send the reply off --- */
 311
 312   sendto(fd, BBASE(&b), BLEN(&b), 0, (struct sockaddr *)&sin, sizeof(sin));
 313   T( trace(TRACE_DAEMON, "daemon: reply sent"); )
 314   return;
 315
 316 fail:
 317   syslog(LOG_ERR, "couldn't respond to query");
 318   T( trace(TRACE_DAEMON, "daemon: failed to answer query"); )
 319 }
 320
 321 /* --- @daemon__die@ --- *
 322  *
 323  * Arguments:   @int n@ = signal number
 324  *              @void *p@ = ignored
 325  *
 326  * Returns:     Doesn't.
 327  *
 328  * Use:         Exits the daemon.
 329  */
 330
 331 static void daemon__die(int n, void *p)
 332 {
 333   T( trace(TRACE_DAEMON, "daemon: killed by signal %i", n); )
 334   syslog(LOG_NOTICE, "killed by signal type %i", n);
 335   remove(file_PID);
 336   exit(0);
 337 }
 338
 339 /* --- @daemon__setTimer@ --- *
 340  *
 341  * Arguments:   ---
 342  *
 343  * Returns:     ---
 344  *
 345  * Use:         Sets the interval timer up.
 346  */
 347
 348 static void daemon__wakeUp(struct timeval *tv, void *p);
 349
 350 static void daemon__setTimer(void)
 351 {
 352   struct timeval tv;
 353
 354   gettimeofday(&tv, 0);
 355   tv.tv_sec += daemon__awakeEvery;
 356   sel_addtimer(&daemon__sel, &daemon__timer, &tv, daemon__wakeUp, 0);
 357 }
 358
 359 /* --- @daemon__rescan@ --- *
 360  *
 361  * Arguments:   @int n@ = signal number
 362  *              @void *p@ = ignored
 363  *
 364  * Returns:     ---
 365  *
 366  * Use:         Forces a rescan of the daemon's configuration.
 367  */
 368
 369 static void daemon__rescan(int n, void *p)
 370 {
 371   syslog(LOG_INFO, "rescanning configuration file");
 372   name_end();
 373   rule_end();
 374   netg_end();
 375   userdb_end();
 376   dsa_privfree(&daemon__key);
 377   userdb_init();
 378   userdb_local();
 379   userdb_yp();
 380   netg_init();
 381   rule_init();
 382   name_init();
 383   if (daemon__readConfig(daemon__config))
 384     syslog(LOG_ERR, "error reading configuration file");
 385   sel_rmtimer(&daemon__timer);
 386   daemon__setTimer();
 387   fwatch_update(&daemon__cwatch, daemon__config);
 388   fwatch_update(&daemon__kwatch, daemon__keyfile);
 389 }
 390
 391 /* --- @daemon__wakeUp@ --- *
 392  *
 393  * Arguments:   @struct timeval *tv@ = ignored
 394  *              @void *p@ = ignored
 395  *
 396  * Returns:     ---
 397  *
 398  * Use:         Wakes up periodically to check the configuration file.
 399  */
 400
 401 static void daemon__wakeUp(struct timeval *tv, void *p)
 402 {
 403   T( trace(TRACE_DAEMON, "daemon: interval timer"); )
 404   rand_seed(RAND_GLOBAL, 160);
 405   daemon__setTimer();
 406   if (fwatch_update(&daemon__cwatch, daemon__config))
 407     daemon__rescan(0, 0);
 408   else if (fwatch_update(&daemon__kwatch, daemon__keyfile)) {
 409     const char *kf = daemon__keyfile;
 410     daemon__keyfile = 0;
 411     daemon_readKey(kf);
 412   }
 413 }
 414
 415 /* --- @daemon_init@ --- *
 416  *
 417  * Arguments:   @const char *cf@ = pointer to name of configuration file
 418  *              @int port@ = port to listen to, or %$-1$% for default
 419  *              @unsigned f@ = various flags
 420  *
 421  * Returns:     Never.
 422  *
 423  * Use:         Starts `become' up in daemon mode.
 424  */
 425
 426 void daemon_init(const char *cf, int port, unsigned f)
 427 {
 428   int s;
 429   int i;
 430
 431   static struct sigvec {
 432     int sig;
 433     void (*proc)(int n, void *p);
 434     sig s;
 435   } sigs[] = {
 436     { SIGHUP, daemon__rescan },
 437     { SIGINT, daemon__die },
 438     { SIGTERM, daemon__die },
 439     { SIGQUIT, daemon__die },
 440     { 0, 0 }
 441   };
 442
 443   /* --- Remove my root privileges --- *
 444    *
 445    * Just in case there's anything dodgy in my configuration file, or the
 446    * user wants me to start on a funny port.
 447    */
 448
 449   setuid(getuid());
 450
 451   /* --- Initialize the random number generator --- */
 452
 453   rand_noisesrc(RAND_GLOBAL, &noise_source);
 454   rand_seed(RAND_GLOBAL, 160);
 455
 456   /* --- Initialise bits of the program --- */
 457
 458   daemon__config = cf;
 459   daemon__port = port;
 460   sel_init(&daemon__sel);
 461   sig_init(&daemon__sel);
 462   userdb_init();
 463   userdb_local();
 464   userdb_yp();
 465   netg_init();
 466   name_init();
 467   rule_init();
 468   openlog(quis(), 0, LOG_DAEMON);
 469   syslog(LOG_NOTICE, "starting up");
 470
 471   if (daemon__readConfig(daemon__config))
 472     die(1, "couldn't read configuration file");
 473   fwatch_init(&daemon__cwatch, daemon__config);
 474   fwatch_init(&daemon__kwatch, daemon__keyfile);
 475
 476   /* --- Decide on a port to use --- *
 477    *
 478    * If I don't have a port yet (e.g., from the configuration file) then
 479    * look it up in /etc/services under whatever name I was started as.
 480    */
 481
 482   if (daemon__port == 0) {
 483     struct servent *se = getservbyname(quis(), "udp");
 484     if (se)
 485       daemon__port = se->s_port;
 486     else
 487       daemon__port = htons(SERVER_PORT);
 488   }
 489
 490   /* --- Now set up a socket --- */
 491
 492   {
 493     struct sockaddr_in sin;
 494
 495     if ((s = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
 496       die(1, "couldn't create socket: %s", strerror(errno));
 497     sin.sin_family = AF_INET;
 498     sin.sin_port = daemon__port;
 499     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 500     if (bind(s, (struct sockaddr *)&sin, sizeof(sin))) {
 501       die(1, "couldn't bind socket to port %i: %s",
 502           ntohs(daemon__port), strerror(errno));
 503     }
 504   }
 505
 506   /* --- Fork off into the sunset --- */
 507
 508   if (!(f & df_nofork)) {
 509     int pid = fork();
 510     FILE *fp;
 511
 512     /* --- Make a background process --- */
 513
 514     if (pid == -1)
 515       die(1, "couldn't fork daemon: %s", strerror(errno));
 516     else if (pid != 0)
 517       return;
 518
 519     /* --- Disconnect from the terminal --- */
 520
 521     setsid();
 522
 523     /* --- Write my process id to a file --- */
 524
 525     if ((fp = fopen(file_PID, "w")) != 0) {
 526       fprintf(fp, "%lu\n", (unsigned long)getpid());
 527       fclose(fp);
 528     }
 529     T( trace(TRACE_DAEMON, "daemon: forked to pid %li", (long)getpid()); )
 530   }
 531
 532   /* --- Set signal handlers --- */
 533
 534   for (i = 0; sigs[i].proc; i++)
 535     sig_add(&sigs[i].s, sigs[i].sig, sigs[i].proc, 0);
 536
 537   /* --- Set the timer for rescanning the file --- */
 538
 539   daemon__setTimer();
 540
 541   /* --- Watch for input --- */
 542
 543   sel_initfile(&daemon__sel, &daemon__listen, s, SEL_READ,
 544                daemon__read, 0);
 545   sel_addfile(&daemon__listen);
 546
 547   /* --- Now wait for something exciting to happen --- */
 548
 549   for (;;) {
 550     if (sel_select(&daemon__sel)) {
 551       if (errno == EINTR || errno == EAGAIN)
 552         continue;
 553       syslog(LOG_ERR, "error from select: %s", strerror(errno));
 554       exit(1);
 555     }
 556   }
 557 }
 558
 559 /*----- That's all, folks -------------------------------------------------*/