pppd/chap-new.c

   1 /*
   2  * chap-new.c - New CHAP implementation.
   3  *
   4  * Copyright (c) 2003 Paul Mackerras. All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. The name(s) of the authors of this software must not be used to
  14  *    endorse or promote products derived from this software without
  15  *    prior written permission.
  16  *
  17  * 3. Redistributions of any form whatsoever must retain the following
  18  *    acknowledgment:
  19  *    "This product includes software developed by Paul Mackerras
  20  *     <paulus@samba.org>".
  21  *
  22  * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
  23  * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  24  * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  25  * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  26  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  27  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  28  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  29  */
  30
  31 #define RCSID   "$Id: chap-new.c,v 1.8 2005/07/13 10:41:58 paulus Exp $"
  32
  33 #include <stdlib.h>
  34 #include <string.h>
  35 #include "pppd.h"
  36 #include "chap-new.h"
  37 #include "chap-md5.h"
  38
  39 #ifdef CHAPMS
  40 #include "chap_ms.h"
  41 #define MDTYPE_ALL (MDTYPE_MICROSOFT_V2 | MDTYPE_MICROSOFT | MDTYPE_MD5)
  42 #else
  43 #define MDTYPE_ALL (MDTYPE_MD5)
  44 #endif
  45
  46 int chap_mdtype_all = MDTYPE_ALL;
  47
  48 /* Hook for a plugin to validate CHAP challenge */
  49 int (*chap_verify_hook)(char *name, char *ourname, int id,
  50                         struct chap_digest_type *digest,
  51                         unsigned char *challenge, unsigned char *response,
  52                         char *message, int message_space) = NULL;
  53
  54 /*
  55  * Option variables.
  56  */
  57 int chap_timeout_time = 3;
  58 int chap_max_transmits = 10;
  59 int chap_rechallenge_time = 0;
  60
  61 /*
  62  * Command-line options.
  63  */
  64 static option_t chap_option_list[] = {
  65         { "chap-restart", o_int, &chap_timeout_time,
  66           "Set timeout for CHAP", OPT_PRIO },
  67         { "chap-max-challenge", o_int, &chap_max_transmits,
  68           "Set max #xmits for challenge", OPT_PRIO },
  69         { "chap-interval", o_int, &chap_rechallenge_time,
  70           "Set interval for rechallenge", OPT_PRIO },
  71         { NULL }
  72 };
  73
  74 /*
  75  * Internal state.
  76  */
  77 static struct chap_client_state {
  78         int flags;
  79         char *name;
  80         struct chap_digest_type *digest;
  81         unsigned char priv[64];         /* private area for digest's use */
  82 } client;
  83
  84 /*
  85  * These limits apply to challenge and response packets we send.
  86  * The +4 is the +1 that we actually need rounded up.
  87  */
  88 #define CHAL_MAX_PKTLEN (PPP_HDRLEN + CHAP_HDRLEN + 4 + MAX_CHALLENGE_LEN + MAXNAMELEN)
  89 #define RESP_MAX_PKTLEN (PPP_HDRLEN + CHAP_HDRLEN + 4 + MAX_RESPONSE_LEN + MAXNAMELEN)
  90
  91 static struct chap_server_state {
  92         int flags;
  93         int id;
  94         char *name;
  95         struct chap_digest_type *digest;
  96         int challenge_xmits;
  97         int challenge_pktlen;
  98         unsigned char challenge[CHAL_MAX_PKTLEN];
  99         char message[256];
 100 } server;
 101
 102 /* Values for flags in chap_client_state and chap_server_state */
 103 #define LOWERUP                 1
 104 #define AUTH_STARTED            2
 105 #define AUTH_DONE               4
 106 #define AUTH_FAILED             8
 107 #define TIMEOUT_PENDING         0x10
 108 #define CHALLENGE_VALID         0x20
 109
 110 /*
 111  * Prototypes.
 112  */
 113 static void chap_init(int unit);
 114 static void chap_lowerup(int unit);
 115 static void chap_lowerdown(int unit);
 116 static void chap_timeout(void *arg);
 117 static void chap_generate_challenge(struct chap_server_state *ss);
 118 static void chap_handle_response(struct chap_server_state *ss, int code,
 119                 unsigned char *pkt, int len);
 120 static int chap_verify_response(char *name, char *ourname, int id,
 121                 struct chap_digest_type *digest,
 122                 unsigned char *challenge, unsigned char *response,
 123                 char *message, int message_space);
 124 static void chap_respond(struct chap_client_state *cs, int id,
 125                 unsigned char *pkt, int len);
 126 static void chap_handle_status(struct chap_client_state *cs, int code, int id,
 127                 unsigned char *pkt, int len);
 128 static void chap_protrej(int unit);
 129 static void chap_input(int unit, unsigned char *pkt, int pktlen);
 130 static int chap_print_pkt(unsigned char *p, int plen,
 131                 void (*printer) __P((void *, char *, ...)), void *arg);
 132
 133 /* List of digest types that we know about */
 134 static struct chap_digest_type *chap_digests;
 135
 136 /*
 137  * chap_init - reset to initial state.
 138  */
 139 static void
 140 chap_init(int unit)
 141 {
 142         memset(&client, 0, sizeof(client));
 143         memset(&server, 0, sizeof(server));
 144
 145         chap_md5_init();
 146 #ifdef CHAPMS
 147         chapms_init();
 148 #endif
 149 }
 150
 151 /*
 152  * Add a new digest type to the list.
 153  */
 154 void
 155 chap_register_digest(struct chap_digest_type *dp)
 156 {
 157         dp->next = chap_digests;
 158         chap_digests = dp;
 159 }
 160
 161 /*
 162  * chap_lowerup - we can start doing stuff now.
 163  */
 164 static void
 165 chap_lowerup(int unit)
 166 {
 167         struct chap_client_state *cs = &client;
 168         struct chap_server_state *ss = &server;
 169
 170         cs->flags |= LOWERUP;
 171         ss->flags |= LOWERUP;
 172         if (ss->flags & AUTH_STARTED)
 173                 chap_timeout(ss);
 174 }
 175
 176 static void
 177 chap_lowerdown(int unit)
 178 {
 179         struct chap_client_state *cs = &client;
 180         struct chap_server_state *ss = &server;
 181
 182         cs->flags = 0;
 183         if (ss->flags & TIMEOUT_PENDING)
 184                 UNTIMEOUT(chap_timeout, ss);
 185         ss->flags = 0;
 186 }
 187
 188 /*
 189  * chap_auth_peer - Start authenticating the peer.
 190  * If the lower layer is already up, we start sending challenges,
 191  * otherwise we wait for the lower layer to come up.
 192  */
 193 void
 194 chap_auth_peer(int unit, char *our_name, int digest_code)
 195 {
 196         struct chap_server_state *ss = &server;
 197         struct chap_digest_type *dp;
 198
 199         if (ss->flags & AUTH_STARTED) {
 200                 error("CHAP: peer authentication already started!");
 201                 return;
 202         }
 203         for (dp = chap_digests; dp != NULL; dp = dp->next)
 204                 if (dp->code == digest_code)
 205                         break;
 206         if (dp == NULL)
 207                 fatal("CHAP digest 0x%x requested but not available",
 208                       digest_code);
 209
 210         ss->digest = dp;
 211         ss->name = our_name;
 212         /* Start with a random ID value */
 213         ss->id = (unsigned char)(drand48() * 256);
 214         ss->flags |= AUTH_STARTED;
 215         if (ss->flags & LOWERUP)
 216                 chap_timeout(ss);
 217 }
 218
 219 /*
 220  * chap_auth_with_peer - Prepare to authenticate ourselves to the peer.
 221  * There isn't much to do until we receive a challenge.
 222  */
 223 void
 224 chap_auth_with_peer(int unit, char *our_name, int digest_code)
 225 {
 226         struct chap_client_state *cs = &client;
 227         struct chap_digest_type *dp;
 228
 229         if (cs->flags & AUTH_STARTED) {
 230                 error("CHAP: authentication with peer already started!");
 231                 return;
 232         }
 233         for (dp = chap_digests; dp != NULL; dp = dp->next)
 234                 if (dp->code == digest_code)
 235                         break;
 236         if (dp == NULL)
 237                 fatal("CHAP digest 0x%x requested but not available",
 238                       digest_code);
 239
 240         cs->digest = dp;
 241         cs->name = our_name;
 242         cs->flags |= AUTH_STARTED;
 243 }
 244
 245 /*
 246  * chap_timeout - It's time to send another challenge to the peer.
 247  * This could be either a retransmission of a previous challenge,
 248  * or a new challenge to start re-authentication.
 249  */
 250 static void
 251 chap_timeout(void *arg)
 252 {
 253         struct chap_server_state *ss = arg;
 254
 255         ss->flags &= ~TIMEOUT_PENDING;
 256         if ((ss->flags & CHALLENGE_VALID) == 0) {
 257                 ss->challenge_xmits = 0;
 258                 chap_generate_challenge(ss);
 259                 ss->flags |= CHALLENGE_VALID;
 260         } else if (ss->challenge_xmits >= chap_max_transmits) {
 261                 ss->flags &= ~CHALLENGE_VALID;
 262                 ss->flags |= AUTH_DONE | AUTH_FAILED;
 263                 auth_peer_fail(0, PPP_CHAP);
 264                 return;
 265         }
 266
 267         output(0, ss->challenge, ss->challenge_pktlen);
 268         ++ss->challenge_xmits;
 269         ss->flags |= TIMEOUT_PENDING;
 270         TIMEOUT(chap_timeout, arg, chap_timeout_time);
 271 }
 272
 273 /*
 274  * chap_generate_challenge - generate a challenge string and format
 275  * the challenge packet in ss->challenge_pkt.
 276  */
 277 static void
 278 chap_generate_challenge(struct chap_server_state *ss)
 279 {
 280         int clen = 1, nlen, len;
 281         unsigned char *p;
 282
 283         p = ss->challenge;
 284         MAKEHEADER(p, PPP_CHAP);
 285         p += CHAP_HDRLEN;
 286         ss->digest->generate_challenge(p);
 287         clen = *p;
 288         nlen = strlen(ss->name);
 289         memcpy(p + 1 + clen, ss->name, nlen);
 290
 291         len = CHAP_HDRLEN + 1 + clen + nlen;
 292         ss->challenge_pktlen = PPP_HDRLEN + len;
 293
 294         p = ss->challenge + PPP_HDRLEN;
 295         p[0] = CHAP_CHALLENGE;
 296         p[1] = ++ss->id;
 297         p[2] = len >> 8;
 298         p[3] = len;
 299 }
 300
 301 /*
 302  * chap_handle_response - check the response to our challenge.
 303  */
 304 static void
 305 chap_handle_response(struct chap_server_state *ss, int id,
 306                      unsigned char *pkt, int len)
 307 {
 308         int response_len, ok, mlen;
 309         unsigned char *response, *p;
 310         char *name = NULL;      /* initialized to shut gcc up */
 311         int (*verifier)(char *, char *, int, struct chap_digest_type *,
 312                 unsigned char *, unsigned char *, char *, int);
 313         char rname[MAXNAMELEN+1];
 314
 315         if ((ss->flags & LOWERUP) == 0)
 316                 return;
 317         if (id != ss->challenge[PPP_HDRLEN+1] || len < 2)
 318                 return;
 319         if (ss->flags & CHALLENGE_VALID) {
 320                 response = pkt;
 321                 GETCHAR(response_len, pkt);
 322                 len -= response_len + 1;        /* length of name */
 323                 name = (char *)pkt + response_len;
 324                 if (len < 0)
 325                         return;
 326
 327                 if (ss->flags & TIMEOUT_PENDING) {
 328                         ss->flags &= ~TIMEOUT_PENDING;
 329                         UNTIMEOUT(chap_timeout, ss);
 330                 }
 331
 332                 if (explicit_remote) {
 333                         name = remote_name;
 334                 } else {
 335                         /* Null terminate and clean remote name. */
 336                         slprintf(rname, sizeof(rname), "%.*v", len, name);
 337                         name = rname;
 338                 }
 339
 340                 if (chap_verify_hook)
 341                         verifier = chap_verify_hook;
 342                 else
 343                         verifier = chap_verify_response;
 344                 ok = (*verifier)(name, ss->name, id, ss->digest,
 345                                  ss->challenge + PPP_HDRLEN + CHAP_HDRLEN,
 346                                  response, ss->message, sizeof(ss->message));
 347                 if (!ok || !auth_number()) {
 348                         ss->flags |= AUTH_FAILED;
 349                         warn("Peer %q failed CHAP authentication", name);
 350                 }
 351         } else if ((ss->flags & AUTH_DONE) == 0)
 352                 return;
 353
 354         /* send the response */
 355         p = outpacket_buf;
 356         MAKEHEADER(p, PPP_CHAP);
 357         mlen = strlen(ss->message);
 358         len = CHAP_HDRLEN + mlen;
 359         p[0] = (ss->flags & AUTH_FAILED)? CHAP_FAILURE: CHAP_SUCCESS;
 360         p[1] = id;
 361         p[2] = len >> 8;
 362         p[3] = len;
 363         if (mlen > 0)
 364                 memcpy(p + CHAP_HDRLEN, ss->message, mlen);
 365         output(0, outpacket_buf, PPP_HDRLEN + len);
 366
 367         if (ss->flags & CHALLENGE_VALID) {
 368                 ss->flags &= ~CHALLENGE_VALID;
 369                 if (ss->flags & AUTH_FAILED) {
 370                         auth_peer_fail(0, PPP_CHAP);
 371                 } else {
 372                         if ((ss->flags & AUTH_DONE) == 0)
 373                                 auth_peer_success(0, PPP_CHAP,
 374                                                   ss->digest->code,
 375                                                   name, strlen(name));
 376                         if (chap_rechallenge_time) {
 377                                 ss->flags |= TIMEOUT_PENDING;
 378                                 TIMEOUT(chap_timeout, ss,
 379                                         chap_rechallenge_time);
 380                         }
 381                 }
 382                 ss->flags |= AUTH_DONE;
 383         }
 384 }
 385
 386 /*
 387  * chap_verify_response - check whether the peer's response matches
 388  * what we think it should be.  Returns 1 if it does (authentication
 389  * succeeded), or 0 if it doesn't.
 390  */
 391 static int
 392 chap_verify_response(char *name, char *ourname, int id,
 393                      struct chap_digest_type *digest,
 394                      unsigned char *challenge, unsigned char *response,
 395                      char *message, int message_space)
 396 {
 397         int ok;
 398         unsigned char secret[MAXSECRETLEN];
 399         int secret_len;
 400
 401         /* Get the secret that the peer is supposed to know */
 402         if (!get_secret(0, name, ourname, (char *)secret, &secret_len, 1)) {
 403                 error("No CHAP secret found for authenticating %q", name);
 404                 return 0;
 405         }
 406
 407         ok = digest->verify_response(id, name, secret, secret_len, challenge,
 408                                      response, message, message_space);
 409         memset(secret, 0, sizeof(secret));
 410
 411         return ok;
 412 }
 413
 414 /*
 415  * chap_respond - Generate and send a response to a challenge.
 416  */
 417 static void
 418 chap_respond(struct chap_client_state *cs, int id,
 419              unsigned char *pkt, int len)
 420 {
 421         int clen, nlen;
 422         int secret_len;
 423         unsigned char *p;
 424         unsigned char response[RESP_MAX_PKTLEN];
 425         char rname[MAXNAMELEN+1];
 426         char secret[MAXSECRETLEN+1];
 427
 428         if ((cs->flags & (LOWERUP | AUTH_STARTED)) != (LOWERUP | AUTH_STARTED))
 429                 return;         /* not ready */
 430         if (len < 2 || len < pkt[0] + 1)
 431                 return;         /* too short */
 432         clen = pkt[0];
 433         nlen = len - (clen + 1);
 434
 435         /* Null terminate and clean remote name. */
 436         slprintf(rname, sizeof(rname), "%.*v", nlen, pkt + clen + 1);
 437
 438         /* Microsoft doesn't send their name back in the PPP packet */
 439         if (explicit_remote || (remote_name[0] != 0 && rname[0] == 0))
 440                 strlcpy(rname, remote_name, sizeof(rname));
 441
 442         /* get secret for authenticating ourselves with the specified host */
 443         if (!get_secret(0, cs->name, rname, secret, &secret_len, 0)) {
 444                 secret_len = 0; /* assume null secret if can't find one */
 445                 warn("No CHAP secret found for authenticating us to %q", rname);
 446         }
 447
 448         p = response;
 449         MAKEHEADER(p, PPP_CHAP);
 450         p += CHAP_HDRLEN;
 451
 452         cs->digest->make_response(p, id, cs->name, pkt,
 453                                   secret, secret_len, cs->priv);
 454         memset(secret, 0, secret_len);
 455
 456         clen = *p;
 457         nlen = strlen(cs->name);
 458         memcpy(p + clen + 1, cs->name, nlen);
 459
 460         p = response + PPP_HDRLEN;
 461         len = CHAP_HDRLEN + clen + 1 + nlen;
 462         p[0] = CHAP_RESPONSE;
 463         p[1] = id;
 464         p[2] = len >> 8;
 465         p[3] = len;
 466
 467         output(0, response, PPP_HDRLEN + len);
 468 }
 469
 470 static void
 471 chap_handle_status(struct chap_client_state *cs, int code, int id,
 472                    unsigned char *pkt, int len)
 473 {
 474         const char *msg = NULL;
 475
 476         if ((cs->flags & (AUTH_DONE|AUTH_STARTED|LOWERUP))
 477             != (AUTH_STARTED|LOWERUP))
 478                 return;
 479         cs->flags |= AUTH_DONE;
 480
 481         if (code == CHAP_SUCCESS) {
 482                 /* used for MS-CHAP v2 mutual auth, yuck */
 483                 if (cs->digest->check_success != NULL) {
 484                         if (!(*cs->digest->check_success)(pkt, len, cs->priv))
 485                                 code = CHAP_FAILURE;
 486                 } else
 487                         msg = "CHAP authentication succeeded";
 488         } else {
 489                 if (cs->digest->handle_failure != NULL)
 490                         (*cs->digest->handle_failure)(pkt, len);
 491                 else
 492                         msg = "CHAP authentication failed";
 493         }
 494         if (msg) {
 495                 if (len > 0)
 496                         info("%s: %.*v", msg, len, pkt);
 497                 else
 498                         info("%s", msg);
 499         }
 500         if (code == CHAP_SUCCESS)
 501                 auth_withpeer_success(0, PPP_CHAP, cs->digest->code);
 502         else {
 503                 cs->flags |= AUTH_FAILED;
 504                 error("CHAP authentication failed");
 505                 auth_withpeer_fail(0, PPP_CHAP);
 506         }
 507 }
 508
 509 static void
 510 chap_input(int unit, unsigned char *pkt, int pktlen)
 511 {
 512         struct chap_client_state *cs = &client;
 513         struct chap_server_state *ss = &server;
 514         unsigned char code, id;
 515         int len;
 516
 517         if (pktlen < CHAP_HDRLEN)
 518                 return;
 519         GETCHAR(code, pkt);
 520         GETCHAR(id, pkt);
 521         GETSHORT(len, pkt);
 522         if (len < CHAP_HDRLEN || len > pktlen)
 523                 return;
 524         len -= CHAP_HDRLEN;
 525
 526         switch (code) {
 527         case CHAP_CHALLENGE:
 528                 chap_respond(cs, id, pkt, len);
 529                 break;
 530         case CHAP_RESPONSE:
 531                 chap_handle_response(ss, id, pkt, len);
 532                 break;
 533         case CHAP_FAILURE:
 534         case CHAP_SUCCESS:
 535                 chap_handle_status(cs, code, id, pkt, len);
 536                 break;
 537         }
 538 }
 539
 540 static void
 541 chap_protrej(int unit)
 542 {
 543         struct chap_client_state *cs = &client;
 544         struct chap_server_state *ss = &server;
 545
 546         if (ss->flags & TIMEOUT_PENDING) {
 547                 ss->flags &= ~TIMEOUT_PENDING;
 548                 UNTIMEOUT(chap_timeout, ss);
 549         }
 550         if (ss->flags & AUTH_STARTED) {
 551                 ss->flags = 0;
 552                 auth_peer_fail(0, PPP_CHAP);
 553         }
 554         if ((cs->flags & (AUTH_STARTED|AUTH_DONE)) == AUTH_STARTED) {
 555                 cs->flags &= ~AUTH_STARTED;
 556                 error("CHAP authentication failed due to protocol-reject");
 557                 auth_withpeer_fail(0, PPP_CHAP);
 558         }
 559 }
 560
 561 /*
 562  * chap_print_pkt - print the contents of a CHAP packet.
 563  */
 564 static char *chap_code_names[] = {
 565         "Challenge", "Response", "Success", "Failure"
 566 };
 567
 568 static int
 569 chap_print_pkt(unsigned char *p, int plen,
 570                void (*printer) __P((void *, char *, ...)), void *arg)
 571 {
 572         int code, id, len;
 573         int clen, nlen;
 574         unsigned char x;
 575
 576         if (plen < CHAP_HDRLEN)
 577                 return 0;
 578         GETCHAR(code, p);
 579         GETCHAR(id, p);
 580         GETSHORT(len, p);
 581         if (len < CHAP_HDRLEN || len > plen)
 582                 return 0;
 583
 584         if (code >= 1 && code <= sizeof(chap_code_names) / sizeof(char *))
 585                 printer(arg, " %s", chap_code_names[code-1]);
 586         else
 587                 printer(arg, " code=0x%x", code);
 588         printer(arg, " id=0x%x", id);
 589         len -= CHAP_HDRLEN;
 590         switch (code) {
 591         case CHAP_CHALLENGE:
 592         case CHAP_RESPONSE:
 593                 if (len < 1)
 594                         break;
 595                 clen = p[0];
 596                 if (len < clen + 1)
 597                         break;
 598                 ++p;
 599                 nlen = len - clen - 1;
 600                 printer(arg, " <");
 601                 for (; clen > 0; --clen) {
 602                         GETCHAR(x, p);
 603                         printer(arg, "%.2x", x);
 604                 }
 605                 printer(arg, ">, name = ");
 606                 print_string((char *)p, nlen, printer, arg);
 607                 break;
 608         case CHAP_FAILURE:
 609         case CHAP_SUCCESS:
 610                 printer(arg, " ");
 611                 print_string((char *)p, len, printer, arg);
 612                 break;
 613         default:
 614                 for (clen = len; clen > 0; --clen) {
 615                         GETCHAR(x, p);
 616                         printer(arg, " %.2x", x);
 617                 }
 618         }
 619
 620         return len + CHAP_HDRLEN;
 621 }
 622
 623 struct protent chap_protent = {
 624         PPP_CHAP,
 625         chap_init,
 626         chap_input,
 627         chap_protrej,
 628         chap_lowerup,
 629         chap_lowerdown,
 630         NULL,           /* open */
 631         NULL,           /* close */
 632         chap_print_pkt,
 633         NULL,           /* datainput */
 634         1,              /* enabled_flag */
 635         "CHAP",         /* name */
 636         NULL,           /* data_name */
 637         chap_option_list,
 638         NULL,           /* check_options */
 639 };