pppd/chap.c

   1 /*
   2  * chap.c - Crytographic Handshake Authentication Protocol.
   3  *
   4  * Copyright (c) 1991 Gregory M. Christy.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms are permitted
   8  * provided that the above copyright notice and this paragraph are
   9  * duplicated in all such forms and that any documentation,
  10  * advertising materials, and other materials related to such
  11  * distribution and use acknowledge that the software was developed
  12  * by Gregory M. Christy.  The name of the author may not be used to
  13  * endorse or promote products derived from this software without
  14  * specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  18  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  19  */
  20
  21 #ifndef lint
  22 static char rcsid[] = "$Id: chap.c,v 1.3 1994/04/18 04:01:07 paulus Exp $";
  23 #endif
  24
  25 /*
  26  * TODO:
  27  */
  28
  29 #include <stdio.h>
  30 #include <sys/types.h>
  31 #include <sys/time.h>
  32 #include <syslog.h>
  33
  34 #include "ppp.h"
  35 #include "pppd.h"
  36 #include "chap.h"
  37 #include "md5.h"
  38
  39 chap_state chap[NPPP];          /* CHAP state; one for each unit */
  40
  41 static void ChapChallengeTimeout __ARGS((caddr_t));
  42 static void ChapResponseTimeout __ARGS((caddr_t));
  43 static void ChapReceiveChallenge __ARGS((chap_state *, u_char *, int, int));
  44 static void ChapReceiveResponse __ARGS((chap_state *, u_char *, int, int));
  45 static void ChapReceiveSuccess __ARGS((chap_state *, u_char *, int, int));
  46 static void ChapReceiveFailure __ARGS((chap_state *, u_char *, int, int));
  47 static void ChapSendStatus __ARGS((chap_state *, int));
  48 static void ChapSendChallenge __ARGS((chap_state *));
  49 static void ChapSendResponse __ARGS((chap_state *));
  50 static void ChapGenChallenge __ARGS((chap_state *));
  51
  52 extern double drand48 __ARGS((void));
  53 extern void srand48 __ARGS((long));
  54
  55 /*
  56  * ChapInit - Initialize a CHAP unit.
  57  */
  58 void
  59 ChapInit(unit)
  60     int unit;
  61 {
  62     chap_state *cstate = &chap[unit];
  63
  64     BZERO(cstate, sizeof(*cstate));
  65     cstate->unit = unit;
  66     cstate->clientstate = CHAPCS_INITIAL;
  67     cstate->serverstate = CHAPSS_INITIAL;
  68     cstate->timeouttime = CHAP_DEFTIMEOUT;
  69     cstate->max_transmits = CHAP_DEFTRANSMITS;
  70     srand48((long) time(NULL)); /* joggle random number generator */
  71 }
  72
  73
  74 /*
  75  * ChapAuthWithPeer - Authenticate us with our peer (start client).
  76  *
  77  */
  78 void
  79 ChapAuthWithPeer(unit, our_name, digest)
  80     int unit;
  81     char *our_name;
  82     int digest;
  83 {
  84     chap_state *cstate = &chap[unit];
  85
  86     cstate->resp_name = our_name;
  87     cstate->resp_type = digest;
  88
  89     if (cstate->clientstate == CHAPCS_INITIAL ||
  90         cstate->clientstate == CHAPCS_PENDING) {
  91         /* lower layer isn't up - wait until later */
  92         cstate->clientstate = CHAPCS_PENDING;
  93         return;
  94     }
  95
  96     /*
  97      * We get here as a result of LCP coming up.
  98      * So even if CHAP was open before, we will
  99      * have to re-authenticate ourselves.
 100      */
 101     cstate->clientstate = CHAPCS_LISTEN;
 102 }
 103
 104
 105 /*
 106  * ChapAuthPeer - Authenticate our peer (start server).
 107  */
 108 void
 109 ChapAuthPeer(unit, our_name, digest)
 110     int unit;
 111     char *our_name;
 112     int digest;
 113 {
 114     chap_state *cstate = &chap[unit];
 115
 116     cstate->chal_name = our_name;
 117     cstate->chal_type = digest;
 118
 119     if (cstate->serverstate == CHAPSS_INITIAL ||
 120         cstate->serverstate == CHAPSS_PENDING) {
 121         /* lower layer isn't up - wait until later */
 122         cstate->serverstate = CHAPSS_PENDING;
 123         return;
 124     }
 125
 126     ChapGenChallenge(cstate);
 127     ChapSendChallenge(cstate);          /* crank it up dude! */
 128     cstate->serverstate = CHAPSS_INITIAL_CHAL;
 129 }
 130
 131
 132 /*
 133  * ChapChallengeTimeout - Timeout expired on sending challenge.
 134  */
 135 static void
 136 ChapChallengeTimeout(arg)
 137     caddr_t arg;
 138 {
 139     chap_state *cstate = (chap_state *) arg;
 140
 141     /* if we aren't sending challenges, don't worry.  then again we */
 142     /* probably shouldn't be here either */
 143     if (cstate->serverstate != CHAPSS_INITIAL_CHAL &&
 144         cstate->serverstate != CHAPSS_RECHALLENGE)
 145         return;
 146
 147     if (cstate->chal_transmits >= cstate->max_transmits) {
 148         /* give up on peer */
 149         syslog(LOG_ERR, "Peer failed to respond to CHAP challenge");
 150         cstate->serverstate = CHAPSS_BADAUTH;
 151         auth_peer_fail(cstate->unit, CHAP);
 152         return;
 153     }
 154
 155     ChapSendChallenge(cstate);          /* Re-send challenge */
 156 }
 157
 158
 159 /*
 160  * ChapResponseTimeout - Timeout expired on sending response.
 161  */
 162 static void
 163 ChapResponseTimeout(arg)
 164     caddr_t arg;
 165 {
 166     chap_state *cstate = (chap_state *) arg;
 167
 168     /* if we aren't sending a response, don't worry. */
 169     if (cstate->clientstate != CHAPCS_RESPONSE)
 170         return;
 171
 172     ChapSendResponse(cstate);           /* re-send response */
 173 }
 174
 175
 176 /*
 177  * ChapRechallenge - Time to challenge the peer again.
 178  */
 179 static void
 180 ChapRechallenge(arg)
 181     caddr_t arg;
 182 {
 183     chap_state *cstate = (chap_state *) arg;
 184
 185     /* if we aren't sending a response, don't worry. */
 186     if (cstate->serverstate != CHAPSS_OPEN)
 187         return;
 188
 189     ChapGenChallenge(cstate);
 190     ChapSendChallenge(cstate);
 191     cstate->serverstate = CHAPSS_RECHALLENGE;
 192
 193     if (cstate->chal_interval != 0)
 194         TIMEOUT(ChapRechallenge, (caddr_t) cstate, cstate->chal_interval);
 195 }
 196
 197
 198 /*
 199  * ChapLowerUp - The lower layer is up.
 200  *
 201  * Start up if we have pending requests.
 202  */
 203 void
 204 ChapLowerUp(unit)
 205     int unit;
 206 {
 207     chap_state *cstate = &chap[unit];
 208
 209     if (cstate->clientstate == CHAPCS_INITIAL)
 210         cstate->clientstate = CHAPCS_CLOSED;
 211     else if (cstate->clientstate == CHAPCS_PENDING)
 212         cstate->clientstate = CHAPCS_LISTEN;
 213
 214     if (cstate->serverstate == CHAPSS_INITIAL)
 215         cstate->serverstate = CHAPSS_CLOSED;
 216     else if (cstate->serverstate == CHAPSS_PENDING) {
 217         ChapGenChallenge(cstate);
 218         ChapSendChallenge(cstate);
 219         cstate->serverstate = CHAPSS_INITIAL_CHAL;
 220     }
 221 }
 222
 223
 224 /*
 225  * ChapLowerDown - The lower layer is down.
 226  *
 227  * Cancel all timeouts.
 228  */
 229 void
 230 ChapLowerDown(unit)
 231     int unit;
 232 {
 233     chap_state *cstate = &chap[unit];
 234
 235     /* Timeout(s) pending?  Cancel if so. */
 236     if (cstate->serverstate == CHAPSS_INITIAL_CHAL ||
 237         cstate->serverstate == CHAPSS_RECHALLENGE)
 238         UNTIMEOUT(ChapChallengeTimeout, (caddr_t) cstate);
 239     else if (cstate->serverstate == CHAPSS_OPEN
 240              && cstate->chal_interval != 0)
 241         UNTIMEOUT(ChapRechallenge, (caddr_t) cstate);
 242     if (cstate->clientstate == CHAPCS_RESPONSE)
 243         UNTIMEOUT(ChapResponseTimeout, (caddr_t) cstate);
 244
 245     cstate->clientstate = CHAPCS_INITIAL;
 246     cstate->serverstate = CHAPSS_INITIAL;
 247 }
 248
 249
 250 /*
 251  * ChapProtocolReject - Peer doesn't grok CHAP.
 252  */
 253 void
 254 ChapProtocolReject(unit)
 255     int unit;
 256 {
 257     chap_state *cstate = &chap[unit];
 258
 259     if (cstate->serverstate != CHAPSS_INITIAL &&
 260         cstate->serverstate != CHAPSS_CLOSED)
 261         auth_peer_fail(unit, CHAP);
 262     if (cstate->clientstate != CHAPCS_INITIAL &&
 263         cstate->clientstate != CHAPCS_CLOSED)
 264         auth_withpeer_fail(unit, CHAP);
 265     ChapLowerDown(unit);                /* shutdown chap */
 266 }
 267
 268
 269 /*
 270  * ChapInput - Input CHAP packet.
 271  */
 272 void
 273 ChapInput(unit, inpacket, packet_len)
 274     int unit;
 275     u_char *inpacket;
 276     int packet_len;
 277 {
 278     chap_state *cstate = &chap[unit];
 279     u_char *inp;
 280     u_char code, id;
 281     int len;
 282
 283     /*
 284      * Parse header (code, id and length).
 285      * If packet too short, drop it.
 286      */
 287     inp = inpacket;
 288     if (packet_len < CHAP_HEADERLEN) {
 289         CHAPDEBUG((LOG_INFO, "ChapInput: rcvd short header."));
 290         return;
 291     }
 292     GETCHAR(code, inp);
 293     GETCHAR(id, inp);
 294     GETSHORT(len, inp);
 295     if (len < CHAP_HEADERLEN) {
 296         CHAPDEBUG((LOG_INFO, "ChapInput: rcvd illegal length."));
 297         return;
 298     }
 299     if (len > packet_len) {
 300         CHAPDEBUG((LOG_INFO, "ChapInput: rcvd short packet."));
 301         return;
 302     }
 303     len -= CHAP_HEADERLEN;
 304
 305     /*
 306      * Action depends on code (as in fact it usually does :-).
 307      */
 308     switch (code) {
 309     case CHAP_CHALLENGE:
 310         ChapReceiveChallenge(cstate, inp, id, len);
 311         break;
 312
 313     case CHAP_RESPONSE:
 314         ChapReceiveResponse(cstate, inp, id, len);
 315         break;
 316
 317     case CHAP_FAILURE:
 318         ChapReceiveFailure(cstate, inp, id, len);
 319         break;
 320
 321     case CHAP_SUCCESS:
 322         ChapReceiveSuccess(cstate, inp, id, len);
 323         break;
 324
 325     default:                            /* Need code reject? */
 326         syslog(LOG_WARNING, "Unknown CHAP code (%d) received.", code);
 327         break;
 328     }
 329 }
 330
 331
 332 /*
 333  * ChapReceiveChallenge - Receive Challenge and send Response.
 334  */
 335 static void
 336 ChapReceiveChallenge(cstate, inp, id, len)
 337     chap_state *cstate;
 338     u_char *inp;
 339     int id;
 340     int len;
 341 {
 342     int rchallenge_len;
 343     u_char *rchallenge;
 344     int secret_len;
 345     char secret[MAXSECRETLEN];
 346     char rhostname[256];
 347     MD5_CTX mdContext;
 348
 349     CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: Rcvd id %d.", id));
 350     if (cstate->clientstate == CHAPCS_CLOSED ||
 351         cstate->clientstate == CHAPCS_PENDING) {
 352         CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: in state %d",
 353                    cstate->clientstate));
 354         return;
 355     }
 356
 357     if (len < 2) {
 358         CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: rcvd short packet."));
 359         return;
 360     }
 361
 362     GETCHAR(rchallenge_len, inp);
 363     len -= sizeof (u_char) + rchallenge_len;    /* now name field length */
 364     if (len < 0) {
 365         CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: rcvd short packet."));
 366         return;
 367     }
 368     rchallenge = inp;
 369     INCPTR(rchallenge_len, inp);
 370
 371     if (len >= sizeof(rhostname))
 372         len = sizeof(rhostname) - 1;
 373     BCOPY(inp, rhostname, len);
 374     rhostname[len] = '\000';
 375
 376     CHAPDEBUG((LOG_INFO, "ChapReceiveChallenge: received name field: %s",
 377                rhostname));
 378
 379     /* get secret for authenticating ourselves with the specified host */
 380     if (!get_secret(cstate->unit, cstate->resp_name, rhostname,
 381                     secret, &secret_len, 0)) {
 382         secret_len = 0;         /* assume null secret if can't find one */
 383         syslog(LOG_WARNING, "No CHAP secret found for authenticating us to %s",
 384                rhostname);
 385     }
 386
 387     /* cancel response send timeout if necessary */
 388     if (cstate->clientstate == CHAPCS_RESPONSE)
 389         UNTIMEOUT(ChapResponseTimeout, (caddr_t) cstate);
 390
 391     cstate->resp_id = id;
 392     cstate->resp_transmits = 0;
 393
 394     /*  generate MD based on negotiated type */
 395     switch (cstate->resp_type) {
 396
 397     case CHAP_DIGEST_MD5:               /* only MD5 is defined for now */
 398         MD5Init(&mdContext);
 399         MD5Update(&mdContext, &cstate->resp_id, 1);
 400         MD5Update(&mdContext, secret, secret_len);
 401         MD5Update(&mdContext, rchallenge, rchallenge_len);
 402         MD5Final(&mdContext);
 403         BCOPY(mdContext.digest, cstate->response, MD5_SIGNATURE_SIZE);
 404         cstate->resp_length = MD5_SIGNATURE_SIZE;
 405         break;
 406
 407     default:
 408         CHAPDEBUG((LOG_INFO, "unknown digest type %d", cstate->resp_type));
 409         return;
 410     }
 411
 412     ChapSendResponse(cstate);
 413 }
 414
 415
 416 /*
 417  * ChapReceiveResponse - Receive and process response.
 418  */
 419 static void
 420 ChapReceiveResponse(cstate, inp, id, len)
 421     chap_state *cstate;
 422     u_char *inp;
 423     int id;
 424     int len;
 425 {
 426     u_char *remmd, remmd_len;
 427     int secret_len, old_state;
 428     int code;
 429     char rhostname[256];
 430     u_char buf[256];
 431     MD5_CTX mdContext;
 432     u_char msg[256];
 433     char secret[MAXSECRETLEN];
 434
 435     CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: Rcvd id %d.", id));
 436
 437     if (cstate->serverstate == CHAPSS_CLOSED ||
 438         cstate->serverstate == CHAPSS_PENDING) {
 439         CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: in state %d",
 440                    cstate->serverstate));
 441         return;
 442     }
 443
 444     if (id != cstate->chal_id)
 445         return;                 /* doesn't match ID of last challenge */
 446
 447     /*
 448      * If we have received a duplicate or bogus Response,
 449      * we have to send the same answer (Success/Failure)
 450      * as we did for the first Response we saw.
 451      */
 452     if (cstate->serverstate == CHAPSS_OPEN) {
 453         ChapSendStatus(cstate, CHAP_SUCCESS);
 454         return;
 455     }
 456     if (cstate->serverstate == CHAPSS_BADAUTH) {
 457         ChapSendStatus(cstate, CHAP_FAILURE);
 458         return;
 459     }
 460
 461     if (len < 2) {
 462         CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: rcvd short packet."));
 463         return;
 464     }
 465     GETCHAR(remmd_len, inp);            /* get length of MD */
 466     remmd = inp;                        /* get pointer to MD */
 467     INCPTR(remmd_len, inp);
 468
 469     len -= sizeof (u_char) + remmd_len;
 470     if (len < 0) {
 471         CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: rcvd short packet."));
 472         return;
 473     }
 474
 475     UNTIMEOUT(ChapChallengeTimeout, (caddr_t) cstate);
 476
 477     if (len >= sizeof(rhostname))
 478         len = sizeof(rhostname) - 1;
 479     BCOPY(inp, rhostname, len);
 480     rhostname[len] = '\000';
 481
 482     CHAPDEBUG((LOG_INFO, "ChapReceiveResponse: received name field: %s",
 483                rhostname));
 484
 485     /*
 486      * Get secret for authenticating them with us,
 487      * do the hash ourselves, and compare the result.
 488      */
 489     code = CHAP_FAILURE;
 490     if (!get_secret(cstate->unit, rhostname, cstate->chal_name,
 491                    secret, &secret_len, 1)) {
 492         syslog(LOG_WARNING, "No CHAP secret found for authenticating %s",
 493                rhostname);
 494     } else {
 495
 496         /*  generate MD based on negotiated type */
 497         switch (cstate->chal_type) {
 498
 499         case CHAP_DIGEST_MD5:           /* only MD5 is defined for now */
 500             if (remmd_len != MD5_SIGNATURE_SIZE)
 501                 break;                  /* it's not even the right length */
 502             MD5Init(&mdContext);
 503             MD5Update(&mdContext, &cstate->chal_id, 1);
 504             MD5Update(&mdContext, secret, secret_len);
 505             MD5Update(&mdContext, cstate->challenge, cstate->chal_len);
 506             MD5Final(&mdContext);
 507
 508             /* compare local and remote MDs and send the appropriate status */
 509             if (bcmp (mdContext.digest, remmd, MD5_SIGNATURE_SIZE) == 0)
 510                 code = CHAP_SUCCESS;    /* they are the same! */
 511             break;
 512
 513         default:
 514             CHAPDEBUG((LOG_INFO, "unknown digest type %d", cstate->chal_type));
 515         }
 516     }
 517
 518     ChapSendStatus(cstate, code);
 519
 520     if (code == CHAP_SUCCESS) {
 521         old_state = cstate->serverstate;
 522         cstate->serverstate = CHAPSS_OPEN;
 523         if (old_state == CHAPSS_INITIAL_CHAL) {
 524             auth_peer_success(cstate->unit, CHAP);
 525         }
 526         if (cstate->chal_interval != 0)
 527             TIMEOUT(ChapRechallenge, (caddr_t) cstate, cstate->chal_interval);
 528
 529     } else {
 530         syslog(LOG_ERR, "CHAP peer authentication failed");
 531         cstate->serverstate = CHAPSS_BADAUTH;
 532         auth_peer_fail(cstate->unit, CHAP);
 533     }
 534 }
 535
 536 /*
 537  * ChapReceiveSuccess - Receive Success
 538  */
 539 static void
 540 ChapReceiveSuccess(cstate, inp, id, len)
 541     chap_state *cstate;
 542     u_char *inp;
 543     u_char id;
 544     int len;
 545 {
 546
 547     CHAPDEBUG((LOG_INFO, "ChapReceiveSuccess: Rcvd id %d.", id));
 548
 549     if (cstate->clientstate == CHAPCS_OPEN)
 550         /* presumably an answer to a duplicate response */
 551         return;
 552
 553     if (cstate->clientstate != CHAPCS_RESPONSE) {
 554         /* don't know what this is */
 555         CHAPDEBUG((LOG_INFO, "ChapReceiveSuccess: in state %d\n",
 556                    cstate->clientstate));
 557         return;
 558     }
 559
 560     UNTIMEOUT(ChapResponseTimeout, (caddr_t) cstate);
 561
 562     /*
 563      * Print message.
 564      */
 565     if (len > 0)
 566         PRINTMSG(inp, len);
 567
 568     cstate->clientstate = CHAPCS_OPEN;
 569
 570     auth_withpeer_success(cstate->unit, CHAP);
 571 }
 572
 573
 574 /*
 575  * ChapReceiveFailure - Receive failure.
 576  */
 577 static void
 578 ChapReceiveFailure(cstate, inp, id, len)
 579     chap_state *cstate;
 580     u_char *inp;
 581     u_char id;
 582     int len;
 583 {
 584     u_char msglen;
 585     u_char *msg;
 586
 587     CHAPDEBUG((LOG_INFO, "ChapReceiveFailure: Rcvd id %d.", id));
 588
 589     if (cstate->clientstate != CHAPCS_RESPONSE) {
 590         /* don't know what this is */
 591         CHAPDEBUG((LOG_INFO, "ChapReceiveFailure: in state %d\n",
 592                    cstate->clientstate));
 593         return;
 594     }
 595
 596     UNTIMEOUT(ChapResponseTimeout, (caddr_t) cstate);
 597
 598     /*
 599      * Print message.
 600      */
 601     if (len > 0)
 602         PRINTMSG(inp, len);
 603
 604     syslog(LOG_ERR, "CHAP authentication failed");
 605     auth_withpeer_fail(cstate->unit, CHAP);
 606 }
 607
 608
 609 /*
 610  * ChapSendChallenge - Send an Authenticate challenge.
 611  */
 612 static void
 613 ChapSendChallenge(cstate)
 614     chap_state *cstate;
 615 {
 616     u_char *outp;
 617     int chal_len, name_len;
 618     int outlen;
 619
 620     chal_len = cstate->chal_len;
 621     name_len = strlen(cstate->chal_name);
 622     outlen = CHAP_HEADERLEN + sizeof (u_char) + chal_len + name_len;
 623     outp = outpacket_buf;
 624
 625     MAKEHEADER(outp, CHAP);             /* paste in a CHAP header */
 626
 627     PUTCHAR(CHAP_CHALLENGE, outp);
 628     PUTCHAR(cstate->chal_id, outp);
 629     PUTSHORT(outlen, outp);
 630
 631     PUTCHAR(chal_len, outp);            /* put length of challenge */
 632     BCOPY(cstate->challenge, outp, chal_len);
 633     INCPTR(chal_len, outp);
 634
 635     BCOPY(cstate->chal_name, outp, name_len);   /* append hostname */
 636
 637     output(cstate->unit, outpacket_buf, outlen + DLLHEADERLEN);
 638
 639     CHAPDEBUG((LOG_INFO, "ChapSendChallenge: Sent id %d.", cstate->chal_id));
 640
 641     TIMEOUT(ChapChallengeTimeout, (caddr_t) cstate, cstate->timeouttime);
 642     ++cstate->chal_transmits;
 643 }
 644
 645
 646 /*
 647  * ChapSendStatus - Send a status response (ack or nak).
 648  */
 649 static void
 650 ChapSendStatus(cstate, code)
 651     chap_state *cstate;
 652     int code;
 653 {
 654     u_char *outp;
 655     int outlen, msglen;
 656     char msg[256];
 657
 658     if (code == CHAP_SUCCESS)
 659         sprintf(msg, "Welcome to %s.", hostname);
 660     else
 661         sprintf(msg, "I don't like you.  Go 'way.");
 662     msglen = strlen(msg);
 663
 664     outlen = CHAP_HEADERLEN + msglen;
 665     outp = outpacket_buf;
 666
 667     MAKEHEADER(outp, CHAP);     /* paste in a header */
 668
 669     PUTCHAR(code, outp);
 670     PUTCHAR(cstate->chal_id, outp);
 671     PUTSHORT(outlen, outp);
 672     BCOPY(msg, outp, msglen);
 673     output(cstate->unit, outpacket_buf, outlen + DLLHEADERLEN);
 674
 675     CHAPDEBUG((LOG_INFO, "ChapSendStatus: Sent code %d, id %d.", code,
 676                cstate->chal_id));
 677 }
 678
 679 /*
 680  * ChapGenChallenge is used to generate a pseudo-random challenge string of
 681  * a pseudo-random length between min_len and max_len.  The challenge
 682  * string and its length are stored in *cstate, and various other fields of
 683  * *cstate are initialized.
 684  */
 685
 686 static void
 687 ChapGenChallenge(cstate)
 688     chap_state *cstate;
 689 {
 690     int chal_len;
 691     u_char *ptr = cstate->challenge;
 692     unsigned int i;
 693
 694     /* pick a random challenge length between MIN_CHALLENGE_LENGTH and
 695        MAX_CHALLENGE_LENGTH */
 696     chal_len =  (unsigned) ((drand48() *
 697                              (MAX_CHALLENGE_LENGTH - MIN_CHALLENGE_LENGTH)) +
 698                             MIN_CHALLENGE_LENGTH);
 699     cstate->chal_len = chal_len;
 700     cstate->chal_id = ++cstate->id;
 701     cstate->chal_transmits = 0;
 702
 703     /* generate a random string */
 704     for (i = 0; i < chal_len; i++ )
 705         *ptr++ = (char) (drand48() * 0xff);
 706 }
 707
 708 /*
 709  * ChapSendResponse - send a response packet with values as specified
 710  * in *cstate.
 711  */
 712 /* ARGSUSED */
 713 static void
 714 ChapSendResponse(cstate)
 715     chap_state *cstate;
 716 {
 717     u_char *outp;
 718     int outlen, md_len, name_len;
 719
 720     md_len = cstate->resp_length;
 721     name_len = strlen(cstate->resp_name);
 722     outlen = CHAP_HEADERLEN + sizeof (u_char) + md_len + name_len;
 723     outp = outpacket_buf;
 724
 725     MAKEHEADER(outp, CHAP);
 726
 727     PUTCHAR(CHAP_RESPONSE, outp);       /* we are a response */
 728     PUTCHAR(cstate->resp_id, outp);     /* copy id from challenge packet */
 729     PUTSHORT(outlen, outp);             /* packet length */
 730
 731     PUTCHAR(md_len, outp);              /* length of MD */
 732     BCOPY(cstate->response, outp, md_len);      /* copy MD to buffer */
 733     INCPTR(md_len, outp);
 734
 735     BCOPY(cstate->resp_name, outp, name_len); /* append our name */
 736
 737     /* send the packet */
 738     output(cstate->unit, outpacket_buf, outlen + DLLHEADERLEN);
 739
 740     cstate->clientstate = CHAPCS_RESPONSE;
 741     TIMEOUT(ChapResponseTimeout, (caddr_t) cstate, cstate->timeouttime);
 742     ++cstate->resp_transmits;
 743 }
 744
 745 /*
 746  * ChapPrintPkt - print the contents of a CHAP packet.
 747  */
 748 char *ChapCodenames[] = {
 749     "Challenge", "Response", "Success", "Failure"
 750 };
 751
 752 int
 753 ChapPrintPkt(p, plen, printer, arg)
 754     u_char *p;
 755     int plen;
 756     void (*printer) __ARGS((void *, char *, ...));
 757     void *arg;
 758 {
 759     int code, id, len;
 760     int clen, nlen;
 761     u_char x;
 762
 763     if (plen < CHAP_HEADERLEN)
 764         return 0;
 765     GETCHAR(code, p);
 766     GETCHAR(id, p);
 767     GETSHORT(len, p);
 768     if (len < CHAP_HEADERLEN || len > plen)
 769         return 0;
 770
 771     if (code >= 1 && code <= sizeof(ChapCodenames) / sizeof(char *))
 772         printer(arg, " %s", ChapCodenames[code-1]);
 773     else
 774         printer(arg, " code=0x%x", code);
 775     printer(arg, " id=0x%x", id);
 776     len -= CHAP_HEADERLEN;
 777     switch (code) {
 778     case CHAP_CHALLENGE:
 779     case CHAP_RESPONSE:
 780         if (len < 1)
 781             break;
 782         clen = p[0];
 783         if (len < clen + 1)
 784             break;
 785         ++p;
 786         nlen = len - clen - 1;
 787         printer(arg, " <");
 788         for (; clen > 0; --clen) {
 789             GETCHAR(x, p);
 790             printer(arg, "%.2x", x);
 791         }
 792         printer(arg, ">, name = ");
 793         print_string((char *)p, nlen, printer, arg);
 794         break;
 795     case CHAP_FAILURE:
 796     case CHAP_SUCCESS:
 797         printer(arg, " ");
 798         print_string((char *)p, len, printer, arg);
 799         break;
 800     default:
 801         for (clen = len; clen > 0; --clen) {
 802             GETCHAR(x, p);
 803             printer(arg, " %.2x", x);
 804         }
 805     }
 806
 807     return len + CHAP_HEADERLEN;
 808 }
 809
 810 #ifdef NO_DRAND48
 811
 812 double drand48()
 813 {
 814   return (double)random() / (double)0x7fffffffL; /* 2**31-1 */
 815 }
 816
 817 void srand48(seedval)
 818 long seedval;
 819 {
 820   srand((int)seedval);
 821 }
 822
 823 #endif