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

   1 /* -*-c-*-
   2  *
   3  * $Id: check.c,v 1.4.2.1 1997/09/26 09:08:01 mdw Exp $
   4  *
   5  * Check validity of requests
   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: check.c,v $
  32  * Revision 1.4.2.1  1997/09/26 09:08:01  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 1.4  1997/08/07 09:52:05  mdw
  38  * (Log entry for previous version is bogus.)  Added support for multiple
  39  * servers.
  40  *
  41  * Revision 1.2  1997/08/04 10:24:20  mdw
  42  * Sources placed under CVS control.
  43  *
  44  * Revision 1.1  1997/07/21  13:47:53  mdw
  45  * Initial revision
  46  *
  47  */
  48
  49 /*----- Header files ------------------------------------------------------*/
  50
  51 /* --- ANSI headers --- */
  52
  53 #include <ctype.h>
  54 #include <errno.h>
  55 #include <stdio.h>
  56 #include <stdlib.h>
  57 #include <string.h>
  58 #include <time.h>
  59
  60 /* --- Unix headers --- */
  61
  62 #include <sys/time.h>
  63 #include <sys/types.h>
  64 #include <sys/socket.h>
  65
  66 #include <netinet/in.h>
  67
  68 #include <arpa/inet.h>
  69
  70 #include <netdb.h>
  71 #include <unistd.h>
  72
  73 /* --- Local headers --- */
  74
  75 #include "become.h"
  76 #include "blowfish.h"
  77 #include "config.h"
  78 #include "crypt.h"
  79 #include "lexer.h"
  80 #include "name.h"
  81 #include "netg.h"
  82 #include "rule.h"
  83 #include "parser.h"
  84 #include "tx.h"
  85 #include "userdb.h"
  86 #include "utils.h"
  87
  88 /*----- Main code ---------------------------------------------------------*/
  89
  90 /* --- @check__send@ --- *
  91  *
  92  * Arguments:   @unsigned char *crq@ = pointer to encrypted request
  93  *              @int fd@ = socket to send from
  94  *              @struct sockaddr_in *serv@ = pointer to table of servers
  95  *              @size_t n_serv@ = number of servers
  96  *
  97  * Returns:     ---
  98  *
  99  * Use:         Sends the request packet to the list of servers.  If the
 100  *              message couldn't be sent to any of them, an error is
 101  *              reported.
 102  */
 103
 104 static void check__send(unsigned char *crq, int fd,
 105                         struct sockaddr_in *serv, size_t n_serv)
 106 {
 107   size_t i;
 108   int ok = 0;
 109   int err = 0;
 110
 111   for (i = 0; i < n_serv; i++) {
 112     if (sendto(fd, (char *)crq, crq_size, 0,
 113                (struct sockaddr *)(serv + i), sizeof(serv[i])) < 0) {
 114       T( trace(TRACE_CLIENT, "client: send to %s failed: %s",
 115                inet_ntoa(serv[i].sin_addr), strerror(errno)); )
 116       err = errno;
 117     } else
 118       ok = 1;
 119   }
 120
 121   if (!ok)
 122     die("couldn't send request to server: %s", strerror(err));
 123 }
 124
 125 /* --- @check__ask@ --- *
 126  *
 127  * Arguments:   @request *rq@ = pointer to request buffer
 128  *              @struct sockaddr_in *serv@ = pointer to table of servers
 129  *              @size_t n_serv@ = number of servers
 130  *
 131  * Returns:     Nonzero if OK, zero if forbidden
 132  *
 133  * Use:         Contacts a number of servers to decide whether the request
 134  *              is OK.
 135  */
 136
 137 static int check__ask(request *rq, struct sockaddr_in *serv, size_t n_serv)
 138 {
 139   int fd;
 140   unsigned char crq[crq_size];
 141   unsigned char sk[BLOWFISH_KEYSIZE];
 142   time_t t;
 143   pid_t pid;
 144
 145   /* --- First, build the encrypted request packet --- */
 146
 147   {
 148     unsigned char k[BLOWFISH_KEYSIZE];
 149     FILE *fp;
 150
 151     /* --- Read in the encryption key --- */
 152
 153     if ((fp = fopen(file_KEY, "r")) == 0) {
 154       die("couldn't open key file `%s': %s", file_KEY,
 155           strerror(errno));
 156     }
 157     tx_getBits(k, 128, fp);
 158
 159     /* --- Now build a request packet --- */
 160
 161     t = time(0);
 162     pid = getpid();
 163     crypt_packRequest(rq, crq, t, pid, k, sk);
 164     burn(k);
 165     T( trace(TRACE_CLIENT, "client: encrypted request packet"); )
 166   }
 167
 168   /* --- Create my socket --- */
 169
 170   {
 171     struct sockaddr_in sin;
 172
 173     if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
 174       die("couldn't create socket: %s", strerror(errno));
 175
 176     /* --- Bind myself to some address --- */
 177
 178     sin.sin_family = AF_INET;
 179     sin.sin_port = 0;
 180     sin.sin_addr.s_addr = htonl(INADDR_ANY);
 181
 182     if (bind(fd, (struct sockaddr *)&sin, sizeof(sin)) < 0)
 183       die("couldn't bind socket to address: %s", strerror(errno));
 184   }
 185
 186   /* --- Now wait for a reply --- */
 187
 188   {
 189     fd_set fds;
 190     struct timeval start, now, tv;
 191     int ind;
 192     size_t i;
 193
 194     /* --- State table for waiting for replies --- *
 195      *
 196      * For each number, send off the request to our servers, and wait for
 197      * that many seconds to have elapsed since we started.  If the number is
 198      * %$-1$% then it's time to give up.
 199      */
 200
 201     static int tbl[] = { 0, 5, 10, 20, -1 };
 202
 203     /* --- Find out when we are --- */
 204
 205     gettimeofday(&start, 0);
 206     ind = 0;
 207
 208     /* --- Now loop until everything's done --- */
 209
 210     for (;;) {
 211       gettimeofday(&now, 0);
 212
 213       /* --- If the current timer has expired, find one that hasn't --- *
 214        *
 215        * Also resend the request after I've found a timer which is still
 216        * extant.  If there aren't any, report an error.
 217        */
 218
 219       if (now.tv_sec >= start.tv_sec + tbl[ind] &&
 220           now.tv_usec >= start.tv_usec) {
 221         do {
 222           ind++;
 223           if (tbl[ind] < 0)
 224             die("no reply from servers");
 225         } while (now.tv_sec >= start.tv_sec + tbl[ind] &&
 226                  now.tv_usec >= start.tv_usec);
 227         check__send(crq, fd, serv, n_serv);
 228         T( trace(TRACE_CLIENT, "client: send request to servers"); )
 229       }
 230
 231       /* --- Now wait for a packet to arrive --- */
 232
 233       if (now.tv_usec > start.tv_usec) {
 234         now.tv_usec -= 1000000;
 235         now.tv_sec += 1;
 236       }
 237       tv.tv_sec = start.tv_sec + tbl[ind] - now.tv_sec;
 238       tv.tv_usec = start.tv_usec - now.tv_usec;
 239
 240       /* --- Sort out file descriptors to watch --- */
 241
 242       FD_ZERO(&fds);
 243       FD_SET(fd, &fds);
 244
 245       /* --- Wait for them --- */
 246
 247       i = select(FD_SETSIZE, &fds, 0, 0, &tv);
 248       if (i == 0 || (i < 0 && errno == EINTR))
 249         continue;
 250       if (i < 0)
 251         die("error waiting for reply: %s", strerror(errno));
 252
 253       /* --- A reply should be waiting now --- */
 254
 255       {
 256         struct sockaddr_in sin;
 257         int slen = sizeof(sin);
 258         unsigned char buff[256];
 259         int answer;
 260
 261         /* --- Read the reply data --- */
 262
 263         if (recvfrom(fd, (char *)buff, sizeof(buff), 0,
 264                      (struct sockaddr *)&sin, &slen) < 0)
 265           die("error reading server's reply: %s", strerror(errno));
 266
 267         IF_TRACING(TRACE_CLIENT, {
 268           struct hostent *h = gethostbyaddr((char *)&sin.sin_addr,
 269                                             sizeof(sin.sin_addr), AF_INET);
 270           trace(TRACE_CLIENT, "client: reply received from %s port %i",
 271                 h ? h->h_name : inet_ntoa(sin.sin_addr),
 272                 ntohs(sin.sin_port));
 273         })
 274
 275         /* --- Verify the sender --- *
 276          *
 277          * This is more to avoid confusion than for security: an active
 278          * attacker is quite capable of forging the source address.  We rely
 279          * on the checksum in the reply packet for authentication.
 280          */
 281
 282         for (i = 0; i < n_serv; i++) {
 283           if (sin.sin_addr.s_addr == serv[i].sin_addr.s_addr &&
 284               sin.sin_port == serv[i].sin_port)
 285             break;
 286         }
 287         if (i >= n_serv) {
 288           T( trace(TRACE_CLIENT, "client: reply from unknown host"); )
 289           continue;
 290         }
 291
 292         /* --- Unpack and verify the response --- */
 293
 294         answer = crypt_unpackReply(buff, sk, t, pid);
 295         if (answer < 0) {
 296           T( trace(TRACE_CLIENT,
 297                    "client: invalid or corrupt reply packet"); )
 298           continue;
 299         }
 300         return (answer);
 301       }
 302     }
 303   }
 304
 305   die("internal error: can't get here in check__ask");
 306   return (0);
 307 }
 308
 309 /* --- @check__client@ --- *
 310  *
 311  * Arguments:   @request *rq@ = pointer to a request block
 312  *              @FILE *fp@ = file containing server configuration
 313  *
 314  * Returns:     Nonzero if OK, zero if forbidden
 315  *
 316  * Use:         Asks one or several servers whether a request is acceptable.
 317  */
 318
 319 int check__client(request *rq, FILE *fp)
 320 {
 321   /* --- Format of the file --- *
 322    *
 323    * The `servers' file contains entries of the form
 324    *
 325    *    %%\syntax{<host> [`:' <port>]}%%
 326    *
 327    * separates by whitespace.  I build them all into an array of socket
 328    * addresses and pass the whole lot to another function.
 329    */
 330
 331   struct sockaddr_in *serv;             /* Array of servers */
 332   size_t n_serv, max_serv;              /* Number and maximum number */
 333
 334   /* --- Initialise the server array --- */
 335
 336   T( trace(TRACE_CLIENT, "client: reading server definitions"); )
 337   n_serv = 0; max_serv = 4;             /* Four seems reasonable */
 338   serv = xmalloc(sizeof(*serv) * max_serv);
 339
 340   /* --- Start reading the file --- */
 341
 342   {
 343     char buff[256], *p, *l;             /* A buffer and pointers for it */
 344     int port;                           /* Default port for servers */
 345     int state;                          /* Current parser state */
 346     struct in_addr t_host;              /* Temp place for an address*/
 347     int t_port;                         /* Temp place for a port */
 348     int ch;                             /* The current character */
 349
 350     /* --- Parser states --- */
 351
 352     enum {
 353       st_start,                         /* Waiting to begin */
 354       st_host,                          /* Reading a new hostname */
 355       st_colon,                         /* Expecting a colon, maybe */
 356       st_preport,                       /* Waiting before reading port */
 357       st_port,                          /* Reading a port number */
 358       st_commit,                        /* Commit a newly read server */
 359       st_done                           /* Finished reading the file */
 360     };
 361
 362     /* --- Find a default port --- */
 363
 364     {
 365       struct servent *s = getservbyname(quis(), "udp");
 366       port = (s ? s->s_port : -1);
 367     }
 368
 369     /* --- Initialise for scanning the file --- */
 370
 371     state = st_host;
 372     p = buff;
 373     l = buff + sizeof(buff);
 374     t_port = port;
 375     ch = getc(fp);
 376
 377     /* --- Go for it --- */
 378
 379     while (state != st_done) {
 380       switch (state) {
 381
 382         /* --- Initial whitespace before hostname --- */
 383
 384         case st_start:
 385           if (ch == EOF)
 386             state = st_done;
 387           else if (isspace((unsigned char)ch))
 388             ch = getc(fp);
 389           else
 390             state = st_host;
 391           break;
 392
 393         /* --- Read a host name --- */
 394
 395         case st_host:
 396           if (p == l)
 397             die("string too long in `" file_SERVER "'");
 398           if (ch != EOF && !isspace((unsigned char)ch) && ch != ':') {
 399             *p++ = ch;
 400             ch = getc(fp);
 401           } else {
 402             struct hostent *h;
 403
 404             *p++ = 0;
 405             if ((h = gethostbyname(buff)) == 0)
 406               die("unknown host `%s' in `" file_SERVER "'", buff);
 407             memcpy(&t_host, h->h_addr, sizeof(t_host));
 408             state = st_colon;
 409           }
 410           break;
 411
 412         /* --- Waiting for a colon coming up --- */
 413
 414         case st_colon:
 415           if (ch == EOF)
 416             state = st_commit;
 417           else if (isspace((unsigned char)ch))
 418             ch = getc(fp);
 419           else if (ch == ':') {
 420             state = st_preport;
 421             ch = getc(fp);
 422           }
 423           else
 424             state = st_commit;
 425           break;
 426
 427         /* --- Clearing whitespace before a port number --- */
 428
 429         case st_preport:
 430           if (ch == EOF)
 431             state = st_commit;
 432           else if (isspace((unsigned char)ch))
 433             ch = getc(fp);
 434           else {
 435             state = st_port;
 436             p = buff;
 437           }
 438           break;
 439
 440         /* --- Read a port number --- */
 441
 442         case st_port:
 443           if (p == l)
 444             die("string too long in `" file_SERVER "'");
 445           if (ch != EOF && !isspace((unsigned char)ch) && ch != ':') {
 446             *p++ = ch;
 447             ch = getc(fp);
 448           } else {
 449             struct servent *s;
 450
 451             *p++ = 0;
 452             s = getservbyname(buff, "udp");
 453             if (!s && isdigit((unsigned char)buff[0]))
 454               t_port = htons(atoi(buff));
 455             else if (!s)
 456               die("unknown service `%s' in `" file_SERVER "'", buff);
 457             else
 458               t_port = s->s_port;
 459             state = st_commit;
 460           }
 461           break;
 462
 463         /* --- A server has been read successfully --- */
 464
 465         case st_commit:
 466           if (n_serv == max_serv) {
 467             max_serv *= 2;
 468             serv = xrealloc(serv, max_serv * sizeof(*serv));
 469           }
 470           serv[n_serv].sin_family = AF_INET;
 471           serv[n_serv].sin_addr = t_host;
 472           serv[n_serv].sin_port = t_port;
 473           n_serv++;
 474           state = st_start;
 475           p = buff;
 476           t_port = port;
 477           break;
 478
 479         /* --- A safety net for a broken parser --- */
 480
 481         default:
 482           die("internal error: can't get here in check__client");
 483           break;
 484       }
 485     }
 486   }
 487
 488   fclose(fp);
 489
 490   /* --- Now start sending requests --- */
 491
 492   if (!n_serv)
 493     die("no servers specified in `" file_SERVER "'");
 494
 495   IF_TRACING(TRACE_CLIENT, {
 496     size_t i;
 497
 498     for (i = 0; i < n_serv; i++) {
 499       trace(TRACE_CLIENT, "client: server %s port %i",
 500             inet_ntoa(serv[i].sin_addr), ntohs(serv[i].sin_port));
 501     }
 502   })
 503   return (check__ask(rq, serv, n_serv));
 504 }
 505
 506 /* --- @check@ --- *
 507  *
 508  * Arguments:   @request *rq@ = pointer to request buffer
 509  *
 510  * Returns:     Nonzero if OK, zero if forbidden
 511  *
 512  * Use:         Checks to see if the request is acceptable.
 513  */
 514
 515 int check(request *rq)
 516 {
 517   FILE *fp;
 518
 519   /* --- Check if we need to talk to a server --- */
 520
 521   if ((fp = fopen(file_SERVER, "r")) != 0)
 522     return (check__client(rq, fp));
 523
 524   /* --- Otherwise do this all the old-fashioned way --- */
 525
 526   if ((fp = fopen(file_RULES, "r")) == 0) {
 527     die("couldn't read configuration file `%s': %s",
 528         file_RULES, strerror(errno));
 529   }
 530
 531   userdb_init();
 532   userdb_local();
 533   userdb_yp();
 534   netg_init();
 535   name_init();
 536   rule_init();
 537   lexer_scan(fp);
 538   yyparse();
 539
 540   return (rule_check(rq));
 541 }
 542
 543 /*----- That's all, folks -------------------------------------------------*/