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. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  *
  18  * 3. The name(s) of the authors of this software must not be used to
  19  *    endorse or promote products derived from this software without
  20  *    prior written permission.
  21  *
  22  * 4. Redistributions of any form whatsoever must retain the following
  23  *    acknowledgment:
  24  *    "This product includes software developed by Paul Mackerras
  25  *     <paulus@samba.org>".
  26  *
  27  * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
  28  * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  29  * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  30  * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  31  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  32  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  33  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  34  */
  35
  36 #define RCSID   "$Id: chap-new.c,v 1.5 2004/10/31 22:23:18 paulus Exp $"
  37
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include "pppd.h"
  41 #include "chap-new.h"
  42 #include "chap-md5.h"
  43
  44 #ifdef CHAPMS
  45 #include "chap_ms.h"
  46 #define MDTYPE_ALL (MDTYPE_MICROSOFT_V2 | MDTYPE_MICROSOFT | MDTYPE_MD5)
  47 #else
  48 #define MDTYPE_ALL (MDTYPE_MD5)
  49 #endif
  50
  51 int chap_mdtype_all = MDTYPE_ALL;
  52
  53 /* Hook for a plugin to validate CHAP challenge */
  54 int (*chap_verify_hook)(char *name, char *ourname, int id,
  55                         struct chap_digest_type *digest,
  56                         unsigned char *challenge, unsigned char *response,
  57                         char *message, int message_space) = NULL;
  58
  59 /*
  60  * Option variables.
  61  */
  62 int chap_timeout_time = 3;
  63 int chap_max_transmits = 10;
  64 int chap_rechallenge_time = 0;
  65
  66 /*
  67  * Command-line options.
  68  */
  69 static option_t chap_option_list[] = {
  70         { "chap-restart", o_int, &chap_timeout_time,
  71           "Set timeout for CHAP", OPT_PRIO },
  72         { "chap-max-challenge", o_int, &chap_max_transmits,
  73           "Set max #xmits for challenge", OPT_PRIO },
  74         { "chap-interval", o_int, &chap_rechallenge_time,
  75           "Set interval for rechallenge", OPT_PRIO },
  76         { NULL }
  77 };
  78
  79 /*
  80  * Internal state.
  81  */
  82 static struct chap_client_state {
  83         int flags;
  84         char *name;
  85         struct chap_digest_type *digest;
  86         unsigned char priv[64];         /* private area for digest's use */
  87 } client;
  88
  89 /*
  90  * These limits apply to challenge and response packets we send.
  91  * The +4 is the +1 that we actually need rounded up.
  92  */
  93 #define CHAL_MAX_PKTLEN (PPP_HDRLEN + CHAP_HDRLEN + 4 + MAX_CHALLENGE_LEN + MAXNAMELEN)
  94 #define RESP_MAX_PKTLEN (PPP_HDRLEN + CHAP_HDRLEN + 4 + MAX_RESPONSE_LEN + MAXNAMELEN)
  95
  96 static struct chap_server_state {
  97         int flags;
  98         int id;
  99         char *name;
 100         struct chap_digest_type *digest;
 101         int challenge_xmits;
 102         int challenge_pktlen;
 103         unsigned char challenge[CHAL_MAX_PKTLEN];
 104 } server;
 105
 106 /* Values for flags in chap_client_state and chap_server_state */
 107 #define LOWERUP                 1
 108 #define AUTH_STARTED            2
 109 #define AUTH_DONE               4
 110 #define AUTH_FAILED             8
 111 #define TIMEOUT_PENDING         0x10
 112 #define CHALLENGE_VALID         0x20
 113
 114 /*
 115  * Prototypes.
 116  */
 117 static void chap_init(int unit);
 118 static void chap_lowerup(int unit);
 119 static void chap_lowerdown(int unit);
 120 static void chap_timeout(void *arg);
 121 static void chap_generate_challenge(struct chap_server_state *ss);
 122 static void chap_handle_response(struct chap_server_state *ss, int code,
 123                 unsigned char *pkt, int len);
 124 static int chap_verify_response(char *name, char *ourname, int id,
 125                 struct chap_digest_type *digest,
 126                 unsigned char *challenge, unsigned char *response,
 127                 char *message, int message_space);
 128 static void chap_respond(struct chap_client_state *cs, int id,
 129                 unsigned char *pkt, int len);
 130 static void chap_handle_status(struct chap_client_state *cs, int code, int id,
 131                 unsigned char *pkt, int len);
 132 static void chap_protrej(int unit);
 133 static void chap_input(int unit, unsigned char *pkt, int pktlen);
 134 static int chap_print_pkt(unsigned char *p, int plen,
 135                 void (*printer) __P((void *, char *, ...)), void *arg);
 136
 137 /* List of digest types that we know about */
 138 static struct chap_digest_type *chap_digests;
 139
 140 /*
 141  * chap_init - reset to initial state.
 142  */
 143 static void
 144 chap_init(int unit)
 145 {
 146         memset(&client, 0, sizeof(client));
 147         memset(&server, 0, sizeof(server));
 148
 149         chap_md5_init();
 150 #ifdef CHAPMS
 151         chapms_init();
 152 #endif
 153 }
 154
 155 /*
 156  * Add a new digest type to the list.
 157  */
 158 void
 159 chap_register_digest(struct chap_digest_type *dp)
 160 {
 161         dp->next = chap_digests;
 162         chap_digests = dp;
 163 }
 164
 165 /*
 166  * chap_lowerup - we can start doing stuff now.
 167  */
 168 static void
 169 chap_lowerup(int unit)
 170 {
 171         struct chap_client_state *cs = &client;
 172         struct chap_server_state *ss = &server;
 173
 174         cs->flags |= LOWERUP;
 175         ss->flags |= LOWERUP;
 176         if (ss->flags & AUTH_STARTED)
 177                 chap_timeout(ss);
 178 }
 179
 180 static void
 181 chap_lowerdown(int unit)
 182 {
 183         struct chap_client_state *cs = &client;
 184         struct chap_server_state *ss = &server;
 185
 186         cs->flags = 0;
 187         if (ss->flags & TIMEOUT_PENDING)
 188                 UNTIMEOUT(chap_timeout, ss);
 189         ss->flags = 0;
 190 }
 191
 192 /*
 193  * chap_auth_peer - Start authenticating the peer.
 194  * If the lower layer is already up, we start sending challenges,
 195  * otherwise we wait for the lower layer to come up.
 196  */
 197 void
 198 chap_auth_peer(int unit, char *our_name, int digest_code)
 199 {
 200         struct chap_server_state *ss = &server;
 201         struct chap_digest_type *dp;
 202
 203         if (ss->flags & AUTH_STARTED) {
 204                 error("CHAP: peer authentication already started!");
 205                 return;
 206         }
 207         for (dp = chap_digests; dp != NULL; dp = dp->next)
 208                 if (dp->code == digest_code)
 209                         break;
 210         if (dp == NULL)
 211                 fatal("CHAP digest 0x%x requested but not available",
 212                       digest_code);
 213
 214         ss->digest = dp;
 215         ss->name = our_name;
 216         /* Start with a random ID value */
 217         ss->id = (unsigned char)(drand48() * 256);
 218         ss->flags |= AUTH_STARTED;
 219         if (ss->flags & LOWERUP)
 220                 chap_timeout(ss);
 221 }
 222
 223 /*
 224  * chap_auth_with_peer - Prepare to authenticate ourselves to the peer.
 225  * There isn't much to do until we receive a challenge.
 226  */
 227 void
 228 chap_auth_with_peer(int unit, char *our_name, int digest_code)
 229 {
 230         struct chap_client_state *cs = &client;
 231         struct chap_digest_type *dp;
 232
 233         if (cs->flags & AUTH_STARTED) {
 234                 error("CHAP: authentication with peer already started!");
 235                 return;
 236         }
 237         for (dp = chap_digests; dp != NULL; dp = dp->next)
 238                 if (dp->code == digest_code)
 239                         break;
 240         if (dp == NULL)
 241                 fatal("CHAP digest 0x%x requested but not available",
 242                       digest_code);
 243
 244         cs->digest = dp;
 245         cs->name = our_name;
 246         cs->flags |= AUTH_STARTED;
 247 }
 248
 249 /*
 250  * chap_timeout - It's time to send another challenge to the peer.
 251  * This could be either a retransmission of a previous challenge,
 252  * or a new challenge to start re-authentication.
 253  */
 254 static void
 255 chap_timeout(void *arg)
 256 {
 257         struct chap_server_state *ss = arg;
 258
 259         ss->flags &= ~TIMEOUT_PENDING;
 260         if ((ss->flags & CHALLENGE_VALID) == 0) {
 261                 ss->challenge_xmits = 0;
 262                 chap_generate_challenge(ss);
 263                 ss->flags |= CHALLENGE_VALID;
 264         } else if (ss->challenge_xmits >= chap_max_transmits) {
 265                 ss->flags &= ~CHALLENGE_VALID;
 266                 ss->flags |= AUTH_DONE | AUTH_FAILED;
 267                 auth_peer_fail(0, PPP_CHAP);
 268                 return;
 269         }
 270
 271         output(0, ss->challenge, ss->challenge_pktlen);
 272         ++ss->challenge_xmits;
 273         ss->flags |= TIMEOUT_PENDING;
 274         TIMEOUT(chap_timeout, arg, chap_timeout_time);
 275 }
 276
 277 /*
 278  * chap_generate_challenge - generate a challenge string and format
 279  * the challenge packet in ss->challenge_pkt.
 280  */
 281 static void
 282 chap_generate_challenge(struct chap_server_state *ss)
 283 {
 284         int clen = 1, nlen, len;
 285         unsigned char *p;
 286
 287         p = ss->challenge;
 288         MAKEHEADER(p, PPP_CHAP);
 289         p += CHAP_HDRLEN;
 290         ss->digest->generate_challenge(p);
 291         clen = *p;
 292         nlen = strlen(ss->name);
 293         memcpy(p + 1 + clen, ss->name, nlen);
 294
 295         len = CHAP_HDRLEN + 1 + clen + nlen;
 296         ss->challenge_pktlen = PPP_HDRLEN + len;
 297
 298         p = ss->challenge + PPP_HDRLEN;
 299         p[0] = CHAP_CHALLENGE;
 300         p[1] = ++ss->id;
 301         p[2] = len >> 8;
 302         p[3] = len;
 303 }
 304
 305 /*
 306  * chap_handle_response - check the response to our challenge.
 307  */
 308 static void
 309 chap_handle_response(struct chap_server_state *ss, int id,
 310                      unsigned char *pkt, int len)
 311 {
 312         int response_len, ok, mlen;
 313         unsigned char *response, *p;
 314         char *name = NULL;      /* initialized to shut gcc up */
 315         int (*verifier)(char *, char *, int, struct chap_digest_type *,
 316                 unsigned char *, unsigned char *, char *, int);
 317         char rname[MAXNAMELEN+1];
 318         char message[256];
 319
 320         if ((ss->flags & LOWERUP) == 0)
 321                 return;
 322         if (id != ss->challenge[PPP_HDRLEN+1] || len < 2)
 323                 return;
 324         if ((ss->flags & AUTH_DONE) == 0) {
 325                 if ((ss->flags & CHALLENGE_VALID) == 0)
 326                         return;
 327                 response = pkt;
 328                 GETCHAR(response_len, pkt);
 329                 len -= response_len + 1;        /* length of name */
 330                 name = (char *)pkt + response_len;
 331                 if (len < 0)
 332                         return;
 333
 334                 ss->flags &= ~CHALLENGE_VALID;
 335                 if (ss->flags & TIMEOUT_PENDING) {
 336                         ss->flags &= ~TIMEOUT_PENDING;
 337                         UNTIMEOUT(chap_timeout, ss);
 338                 }
 339
 340                 if (explicit_remote) {
 341                         name = remote_name;
 342                 } else {
 343                         /* Null terminate and clean remote name. */
 344                         slprintf(rname, sizeof(rname), "%.*v", len, name);
 345                         name = rname;
 346                 }
 347
 348                 if (chap_verify_hook)
 349                         verifier = chap_verify_hook;
 350                 else
 351                         verifier = chap_verify_response;
 352                 ok = (*verifier)(name, ss->name, id, ss->digest,
 353                                  ss->challenge + PPP_HDRLEN + CHAP_HDRLEN,
 354                                  response, message, sizeof(message));
 355                 if (!ok || !auth_number()) {
 356                         ss->flags |= AUTH_FAILED;
 357                         warn("Peer %q failed CHAP authentication", name);
 358                 }
 359         }
 360
 361         /* send the response */
 362         p = outpacket_buf;
 363         MAKEHEADER(p, PPP_CHAP);
 364         mlen = strlen(message);
 365         len = CHAP_HDRLEN + mlen;
 366         p[0] = (ss->flags & AUTH_FAILED)? CHAP_FAILURE: CHAP_SUCCESS;
 367         p[1] = id;
 368         p[2] = len >> 8;
 369         p[3] = len;
 370         if (mlen > 0)
 371                 memcpy(p + CHAP_HDRLEN, message, mlen);
 372         output(0, outpacket_buf, PPP_HDRLEN + len);
 373
 374         if ((ss->flags & AUTH_DONE) == 0) {
 375                 ss->flags |= AUTH_DONE;
 376                 if (ss->flags & AUTH_FAILED) {
 377                         auth_peer_fail(0, PPP_CHAP);
 378                 } else {
 379                         auth_peer_success(0, PPP_CHAP, ss->digest->code,
 380                                           name, strlen(name));
 381                         if (chap_rechallenge_time) {
 382                                 ss->flags |= TIMEOUT_PENDING;
 383                                 TIMEOUT(chap_timeout, ss,
 384                                         chap_rechallenge_time);
 385                         }
 386                 }
 387         }
 388 }
 389
 390 /*
 391  * chap_verify_response - check whether the peer's response matches
 392  * what we think it should be.  Returns 1 if it does (authentication
 393  * succeeded), or 0 if it doesn't.
 394  */
 395 static int
 396 chap_verify_response(char *name, char *ourname, int id,
 397                      struct chap_digest_type *digest,
 398                      unsigned char *challenge, unsigned char *response,
 399                      char *message, int message_space)
 400 {
 401         int ok;
 402         unsigned char secret[MAXSECRETLEN];
 403         int secret_len;
 404
 405         /* Get the secret that the peer is supposed to know */
 406         if (!get_secret(0, name, ourname, (char *)secret, &secret_len, 1)) {
 407                 error("No CHAP secret found for authenticating %q", name);
 408                 return 0;
 409         }
 410
 411         ok = digest->verify_response(id, name, secret, secret_len, challenge,
 412                                      response, message, message_space);
 413         memset(secret, 0, sizeof(secret));
 414
 415         return ok;
 416 }
 417
 418 /*
 419  * chap_respond - Generate and send a response to a challenge.
 420  */
 421 static void
 422 chap_respond(struct chap_client_state *cs, int id,
 423              unsigned char *pkt, int len)
 424 {
 425         int clen, nlen;
 426         int secret_len;
 427         unsigned char *p;
 428         unsigned char response[RESP_MAX_PKTLEN];
 429         char rname[MAXNAMELEN+1];
 430         char secret[MAXSECRETLEN+1];
 431
 432         if ((cs->flags & (LOWERUP | AUTH_STARTED)) != (LOWERUP | AUTH_STARTED))
 433                 return;         /* not ready */
 434         if (len < 2 || len < pkt[0] + 1)
 435                 return;         /* too short */
 436         clen = pkt[0];
 437         nlen = len - (clen + 1);
 438
 439         /* Null terminate and clean remote name. */
 440         slprintf(rname, sizeof(rname), "%.*v", nlen, pkt + clen + 1);
 441
 442         /* Microsoft doesn't send their name back in the PPP packet */
 443         if (explicit_remote || (remote_name[0] != 0 && rname[0] == 0))
 444                 strlcpy(rname, remote_name, sizeof(rname));
 445
 446         /* get secret for authenticating ourselves with the specified host */
 447         if (!get_secret(0, cs->name, rname, secret, &secret_len, 0)) {
 448                 secret_len = 0; /* assume null secret if can't find one */
 449                 warn("No CHAP secret found for authenticating us to %q", rname);
 450         }
 451
 452         p = response;
 453         MAKEHEADER(p, PPP_CHAP);
 454         p += CHAP_HDRLEN;
 455
 456         cs->digest->make_response(p, id, cs->name, pkt,
 457                                   secret, secret_len, cs->priv);
 458         memset(secret, 0, secret_len);
 459
 460         clen = *p;
 461         nlen = strlen(cs->name);
 462         memcpy(p + clen + 1, cs->name, nlen);
 463
 464         p = response + PPP_HDRLEN;
 465         len = CHAP_HDRLEN + clen + 1 + nlen;
 466         p[0] = CHAP_RESPONSE;
 467         p[1] = id;
 468         p[2] = len >> 8;
 469         p[3] = len;
 470
 471         output(0, response, PPP_HDRLEN + len);
 472 }
 473
 474 static void
 475 chap_handle_status(struct chap_client_state *cs, int code, int id,
 476                    unsigned char *pkt, int len)
 477 {
 478         const char *msg = NULL;
 479
 480         if ((cs->flags & (AUTH_DONE|AUTH_STARTED|LOWERUP))
 481             != (AUTH_STARTED|LOWERUP))
 482                 return;
 483         cs->flags |= AUTH_DONE;
 484
 485         if (code == CHAP_SUCCESS) {
 486                 /* used for MS-CHAP v2 mutual auth, yuck */
 487                 if (cs->digest->check_success != NULL) {
 488                         if (!(*cs->digest->check_success)(pkt, len, cs->priv))
 489                                 code = CHAP_FAILURE;
 490                 } else
 491                         msg = "CHAP authentication succeeded";
 492         } else {
 493                 if (cs->digest->handle_failure != NULL)
 494                         (*cs->digest->handle_failure)(pkt, len);
 495                 else
 496                         msg = "CHAP authentication failed";
 497         }
 498         if (msg) {
 499                 if (len > 0)
 500                         info("%s: %.*v", msg, len, pkt);
 501                 else
 502                         info("%s", msg);
 503         }
 504         if (code == CHAP_SUCCESS)
 505                 auth_withpeer_success(0, PPP_CHAP, cs->digest->code);
 506         else {
 507                 cs->flags |= AUTH_FAILED;
 508                 auth_withpeer_fail(0, PPP_CHAP);
 509         }
 510 }
 511
 512 static void
 513 chap_input(int unit, unsigned char *pkt, int pktlen)
 514 {
 515         struct chap_client_state *cs = &client;
 516         struct chap_server_state *ss = &server;
 517         unsigned char code, id;
 518         int len;
 519
 520         if (pktlen < CHAP_HDRLEN)
 521                 return;
 522         GETCHAR(code, pkt);
 523         GETCHAR(id, pkt);
 524         GETSHORT(len, pkt);
 525         if (len < CHAP_HDRLEN || len > pktlen)
 526                 return;
 527         len -= CHAP_HDRLEN;
 528
 529         switch (code) {
 530         case CHAP_CHALLENGE:
 531                 chap_respond(cs, id, pkt, len);
 532                 break;
 533         case CHAP_RESPONSE:
 534                 chap_handle_response(ss, id, pkt, len);
 535                 break;
 536         case CHAP_FAILURE:
 537         case CHAP_SUCCESS:
 538                 chap_handle_status(cs, code, id, pkt, len);
 539                 break;
 540         }
 541 }
 542
 543 static void
 544 chap_protrej(int unit)
 545 {
 546         struct chap_client_state *cs = &client;
 547         struct chap_server_state *ss = &server;
 548
 549         if (ss->flags & TIMEOUT_PENDING) {
 550                 ss->flags &= ~TIMEOUT_PENDING;
 551                 UNTIMEOUT(chap_timeout, ss);
 552         }
 553         if (ss->flags & AUTH_STARTED) {
 554                 ss->flags = 0;
 555                 auth_peer_fail(0, PPP_CHAP);
 556         }
 557         if ((cs->flags & (AUTH_STARTED|AUTH_DONE)) == AUTH_STARTED) {
 558                 cs->flags &= ~AUTH_STARTED;
 559                 auth_withpeer_fail(0, PPP_CHAP);
 560         }
 561 }
 562
 563 /*
 564  * chap_print_pkt - print the contents of a CHAP packet.
 565  */
 566 static char *chap_code_names[] = {
 567         "Challenge", "Response", "Success", "Failure"
 568 };
 569
 570 static int
 571 chap_print_pkt(unsigned char *p, int plen,
 572                void (*printer) __P((void *, char *, ...)), void *arg)
 573 {
 574         int code, id, len;
 575         int clen, nlen;
 576         unsigned char x;
 577
 578         if (plen < CHAP_HDRLEN)
 579                 return 0;
 580         GETCHAR(code, p);
 581         GETCHAR(id, p);
 582         GETSHORT(len, p);
 583         if (len < CHAP_HDRLEN || len > plen)
 584                 return 0;
 585
 586         if (code >= 1 && code <= sizeof(chap_code_names) / sizeof(char *))
 587                 printer(arg, " %s", chap_code_names[code-1]);
 588         else
 589                 printer(arg, " code=0x%x", code);
 590         printer(arg, " id=0x%x", id);
 591         len -= CHAP_HDRLEN;
 592         switch (code) {
 593         case CHAP_CHALLENGE:
 594         case CHAP_RESPONSE:
 595                 if (len < 1)
 596                         break;
 597                 clen = p[0];
 598                 if (len < clen + 1)
 599                         break;
 600                 ++p;
 601                 nlen = len - clen - 1;
 602                 printer(arg, " <");
 603                 for (; clen > 0; --clen) {
 604                         GETCHAR(x, p);
 605                         printer(arg, "%.2x", x);
 606                 }
 607                 printer(arg, ">, name = ");
 608                 print_string((char *)p, nlen, printer, arg);
 609                 break;
 610         case CHAP_FAILURE:
 611         case CHAP_SUCCESS:
 612                 printer(arg, " ");
 613                 print_string((char *)p, len, printer, arg);
 614                 break;
 615         default:
 616                 for (clen = len; clen > 0; --clen) {
 617                         GETCHAR(x, p);
 618                         printer(arg, " %.2x", x);
 619                 }
 620         }
 621
 622         return len + CHAP_HDRLEN;
 623 }
 624
 625 struct protent chap_protent = {
 626         PPP_CHAP,
 627         chap_init,
 628         chap_input,
 629         chap_protrej,
 630         chap_lowerup,
 631         chap_lowerdown,
 632         NULL,           /* open */
 633         NULL,           /* close */
 634         chap_print_pkt,
 635         NULL,           /* datainput */
 636         1,              /* enabled_flag */
 637         "CHAP",         /* name */
 638         NULL,           /* data_name */
 639         chap_option_list,
 640         NULL,           /* check_options */
 641 };