sshconnect2.c

   1 /* $OpenBSD: sshconnect2.c,v 1.204 2014/02/02 03:44:32 djm Exp $ */
   2 /*
   3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   4  * Copyright (c) 2008 Damien Miller.  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  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28
  29 #include <sys/types.h>
  30 #include <sys/socket.h>
  31 #include <sys/wait.h>
  32 #include <sys/stat.h>
  33
  34 #include <errno.h>
  35 #include <fcntl.h>
  36 #include <netdb.h>
  37 #include <pwd.h>
  38 #include <signal.h>
  39 #include <stdarg.h>
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43 #if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H) && !defined(BROKEN_STRNVIS)
  44 #include <vis.h>
  45 #endif
  46
  47 #include "openbsd-compat/sys-queue.h"
  48
  49 #include "xmalloc.h"
  50 #include "ssh.h"
  51 #include "ssh2.h"
  52 #include "buffer.h"
  53 #include "packet.h"
  54 #include "compat.h"
  55 #include "cipher.h"
  56 #include "key.h"
  57 #include "kex.h"
  58 #include "myproposal.h"
  59 #include "sshconnect.h"
  60 #include "authfile.h"
  61 #include "dh.h"
  62 #include "authfd.h"
  63 #include "log.h"
  64 #include "readconf.h"
  65 #include "misc.h"
  66 #include "match.h"
  67 #include "dispatch.h"
  68 #include "canohost.h"
  69 #include "msg.h"
  70 #include "pathnames.h"
  71 #include "uidswap.h"
  72 #include "hostfile.h"
  73
  74 #ifdef GSSAPI
  75 #include "ssh-gss.h"
  76 #endif
  77
  78 /* import */
  79 extern char *client_version_string;
  80 extern char *server_version_string;
  81 extern Options options;
  82
  83 /*
  84  * SSH2 key exchange
  85  */
  86
  87 u_char *session_id2 = NULL;
  88 u_int session_id2_len = 0;
  89
  90 char *xxx_host;
  91 struct sockaddr *xxx_hostaddr;
  92
  93 Kex *xxx_kex = NULL;
  94
  95 static int
  96 verify_host_key_callback(Key *hostkey)
  97 {
  98         if (verify_host_key(xxx_host, xxx_hostaddr, hostkey) == -1)
  99                 fatal("Host key verification failed.");
 100         return 0;
 101 }
 102
 103 static char *
 104 order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
 105 {
 106         char *oavail, *avail, *first, *last, *alg, *hostname, *ret;
 107         size_t maxlen;
 108         struct hostkeys *hostkeys;
 109         int ktype;
 110         u_int i;
 111
 112         /* Find all hostkeys for this hostname */
 113         get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
 114         hostkeys = init_hostkeys();
 115         for (i = 0; i < options.num_user_hostfiles; i++)
 116                 load_hostkeys(hostkeys, hostname, options.user_hostfiles[i]);
 117         for (i = 0; i < options.num_system_hostfiles; i++)
 118                 load_hostkeys(hostkeys, hostname, options.system_hostfiles[i]);
 119
 120         oavail = avail = xstrdup(KEX_DEFAULT_PK_ALG);
 121         maxlen = strlen(avail) + 1;
 122         first = xmalloc(maxlen);
 123         last = xmalloc(maxlen);
 124         *first = *last = '\0';
 125
 126 #define ALG_APPEND(to, from) \
 127         do { \
 128                 if (*to != '\0') \
 129                         strlcat(to, ",", maxlen); \
 130                 strlcat(to, from, maxlen); \
 131         } while (0)
 132
 133         while ((alg = strsep(&avail, ",")) && *alg != '\0') {
 134                 if ((ktype = key_type_from_name(alg)) == KEY_UNSPEC)
 135                         fatal("%s: unknown alg %s", __func__, alg);
 136                 if (lookup_key_in_hostkeys_by_type(hostkeys,
 137                     key_type_plain(ktype), NULL))
 138                         ALG_APPEND(first, alg);
 139                 else
 140                         ALG_APPEND(last, alg);
 141         }
 142 #undef ALG_APPEND
 143         xasprintf(&ret, "%s%s%s", first, *first == '\0' ? "" : ",", last);
 144         if (*first != '\0')
 145                 debug3("%s: prefer hostkeyalgs: %s", __func__, first);
 146
 147         free(first);
 148         free(last);
 149         free(hostname);
 150         free(oavail);
 151         free_hostkeys(hostkeys);
 152
 153         return ret;
 154 }
 155
 156 void
 157 ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 158 {
 159         Kex *kex;
 160
 161         xxx_host = host;
 162         xxx_hostaddr = hostaddr;
 163
 164         if (options.ciphers == (char *)-1) {
 165                 logit("No valid ciphers for protocol version 2 given, using defaults.");
 166                 options.ciphers = NULL;
 167         }
 168         if (options.ciphers != NULL) {
 169                 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 170                 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
 171         }
 172         myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 173             compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
 174         myproposal[PROPOSAL_ENC_ALGS_STOC] =
 175             compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
 176         if (options.compression) {
 177                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 178                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib@openssh.com,zlib,none";
 179         } else {
 180                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 181                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com,zlib";
 182         }
 183         if (options.macs != NULL) {
 184                 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
 185                 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
 186         }
 187         if (options.hostkeyalgorithms != NULL)
 188                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 189                     compat_pkalg_proposal(options.hostkeyalgorithms);
 190         else {
 191                 /* Prefer algorithms that we already have keys for */
 192                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 193                     compat_pkalg_proposal(
 194                     order_hostkeyalgs(host, hostaddr, port));
 195         }
 196         if (options.kex_algorithms != NULL)
 197                 myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms;
 198
 199         if (options.rekey_limit || options.rekey_interval)
 200                 packet_set_rekey_limits((u_int32_t)options.rekey_limit,
 201                     (time_t)options.rekey_interval);
 202
 203         /* start key exchange */
 204         kex = kex_setup(myproposal);
 205         kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 206         kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
 207         kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
 208         kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 209         kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
 210         kex->kex[KEX_C25519_SHA256] = kexc25519_client;
 211         kex->client_version_string=client_version_string;
 212         kex->server_version_string=server_version_string;
 213         kex->verify_host_key=&verify_host_key_callback;
 214
 215         xxx_kex = kex;
 216
 217         dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
 218
 219         if (options.use_roaming && !kex->roaming) {
 220                 debug("Roaming not allowed by server");
 221                 options.use_roaming = 0;
 222         }
 223
 224         session_id2 = kex->session_id;
 225         session_id2_len = kex->session_id_len;
 226
 227 #ifdef DEBUG_KEXDH
 228         /* send 1st encrypted/maced/compressed message */
 229         packet_start(SSH2_MSG_IGNORE);
 230         packet_put_cstring("markus");
 231         packet_send();
 232         packet_write_wait();
 233 #endif
 234 }
 235
 236 /*
 237  * Authenticate user
 238  */
 239
 240 typedef struct Authctxt Authctxt;
 241 typedef struct Authmethod Authmethod;
 242 typedef struct identity Identity;
 243 typedef struct idlist Idlist;
 244
 245 struct identity {
 246         TAILQ_ENTRY(identity) next;
 247         AuthenticationConnection *ac;   /* set if agent supports key */
 248         Key     *key;                   /* public/private key */
 249         char    *filename;              /* comment for agent-only keys */
 250         int     tried;
 251         int     isprivate;              /* key points to the private key */
 252         int     userprovided;
 253 };
 254 TAILQ_HEAD(idlist, identity);
 255
 256 struct Authctxt {
 257         const char *server_user;
 258         const char *local_user;
 259         const char *host;
 260         const char *service;
 261         Authmethod *method;
 262         sig_atomic_t success;
 263         char *authlist;
 264         /* pubkey */
 265         Idlist keys;
 266         AuthenticationConnection *agent;
 267         /* hostbased */
 268         Sensitive *sensitive;
 269         /* kbd-interactive */
 270         int info_req_seen;
 271         /* generic */
 272         void *methoddata;
 273 };
 274 struct Authmethod {
 275         char    *name;          /* string to compare against server's list */
 276         int     (*userauth)(Authctxt *authctxt);
 277         void    (*cleanup)(Authctxt *authctxt);
 278         int     *enabled;       /* flag in option struct that enables method */
 279         int     *batch_flag;    /* flag in option struct that disables method */
 280 };
 281
 282 void    input_userauth_success(int, u_int32_t, void *);
 283 void    input_userauth_success_unexpected(int, u_int32_t, void *);
 284 void    input_userauth_failure(int, u_int32_t, void *);
 285 void    input_userauth_banner(int, u_int32_t, void *);
 286 void    input_userauth_error(int, u_int32_t, void *);
 287 void    input_userauth_info_req(int, u_int32_t, void *);
 288 void    input_userauth_pk_ok(int, u_int32_t, void *);
 289 void    input_userauth_passwd_changereq(int, u_int32_t, void *);
 290
 291 int     userauth_none(Authctxt *);
 292 int     userauth_pubkey(Authctxt *);
 293 int     userauth_passwd(Authctxt *);
 294 int     userauth_kbdint(Authctxt *);
 295 int     userauth_hostbased(Authctxt *);
 296
 297 #ifdef GSSAPI
 298 int     userauth_gssapi(Authctxt *authctxt);
 299 void    input_gssapi_response(int type, u_int32_t, void *);
 300 void    input_gssapi_token(int type, u_int32_t, void *);
 301 void    input_gssapi_hash(int type, u_int32_t, void *);
 302 void    input_gssapi_error(int, u_int32_t, void *);
 303 void    input_gssapi_errtok(int, u_int32_t, void *);
 304 #endif
 305
 306 void    userauth(Authctxt *, char *);
 307
 308 static int sign_and_send_pubkey(Authctxt *, Identity *);
 309 static void pubkey_prepare(Authctxt *);
 310 static void pubkey_cleanup(Authctxt *);
 311 static Key *load_identity_file(char *, int);
 312
 313 static Authmethod *authmethod_get(char *authlist);
 314 static Authmethod *authmethod_lookup(const char *name);
 315 static char *authmethods_get(void);
 316
 317 Authmethod authmethods[] = {
 318 #ifdef GSSAPI
 319         {"gssapi-with-mic",
 320                 userauth_gssapi,
 321                 NULL,
 322                 &options.gss_authentication,
 323                 NULL},
 324 #endif
 325         {"hostbased",
 326                 userauth_hostbased,
 327                 NULL,
 328                 &options.hostbased_authentication,
 329                 NULL},
 330         {"publickey",
 331                 userauth_pubkey,
 332                 NULL,
 333                 &options.pubkey_authentication,
 334                 NULL},
 335         {"keyboard-interactive",
 336                 userauth_kbdint,
 337                 NULL,
 338                 &options.kbd_interactive_authentication,
 339                 &options.batch_mode},
 340         {"password",
 341                 userauth_passwd,
 342                 NULL,
 343                 &options.password_authentication,
 344                 &options.batch_mode},
 345         {"none",
 346                 userauth_none,
 347                 NULL,
 348                 NULL,
 349                 NULL},
 350         {NULL, NULL, NULL, NULL, NULL}
 351 };
 352
 353 void
 354 ssh_userauth2(const char *local_user, const char *server_user, char *host,
 355     Sensitive *sensitive)
 356 {
 357         Authctxt authctxt;
 358         int type;
 359
 360         if (options.challenge_response_authentication)
 361                 options.kbd_interactive_authentication = 1;
 362
 363         packet_start(SSH2_MSG_SERVICE_REQUEST);
 364         packet_put_cstring("ssh-userauth");
 365         packet_send();
 366         debug("SSH2_MSG_SERVICE_REQUEST sent");
 367         packet_write_wait();
 368         type = packet_read();
 369         if (type != SSH2_MSG_SERVICE_ACCEPT)
 370                 fatal("Server denied authentication request: %d", type);
 371         if (packet_remaining() > 0) {
 372                 char *reply = packet_get_string(NULL);
 373                 debug2("service_accept: %s", reply);
 374                 free(reply);
 375         } else {
 376                 debug2("buggy server: service_accept w/o service");
 377         }
 378         packet_check_eom();
 379         debug("SSH2_MSG_SERVICE_ACCEPT received");
 380
 381         if (options.preferred_authentications == NULL)
 382                 options.preferred_authentications = authmethods_get();
 383
 384         /* setup authentication context */
 385         memset(&authctxt, 0, sizeof(authctxt));
 386         pubkey_prepare(&authctxt);
 387         authctxt.server_user = server_user;
 388         authctxt.local_user = local_user;
 389         authctxt.host = host;
 390         authctxt.service = "ssh-connection";            /* service name */
 391         authctxt.success = 0;
 392         authctxt.method = authmethod_lookup("none");
 393         authctxt.authlist = NULL;
 394         authctxt.methoddata = NULL;
 395         authctxt.sensitive = sensitive;
 396         authctxt.info_req_seen = 0;
 397         if (authctxt.method == NULL)
 398                 fatal("ssh_userauth2: internal error: cannot send userauth none request");
 399
 400         /* initial userauth request */
 401         userauth_none(&authctxt);
 402
 403         dispatch_init(&input_userauth_error);
 404         dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
 405         dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
 406         dispatch_set(SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
 407         dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt);     /* loop until success */
 408
 409         pubkey_cleanup(&authctxt);
 410         dispatch_range(SSH2_MSG_USERAUTH_MIN, SSH2_MSG_USERAUTH_MAX, NULL);
 411
 412         debug("Authentication succeeded (%s).", authctxt.method->name);
 413 }
 414
 415 void
 416 userauth(Authctxt *authctxt, char *authlist)
 417 {
 418         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 419                 authctxt->method->cleanup(authctxt);
 420
 421         free(authctxt->methoddata);
 422         authctxt->methoddata = NULL;
 423         if (authlist == NULL) {
 424                 authlist = authctxt->authlist;
 425         } else {
 426                 free(authctxt->authlist);
 427                 authctxt->authlist = authlist;
 428         }
 429         for (;;) {
 430                 Authmethod *method = authmethod_get(authlist);
 431                 if (method == NULL)
 432                         fatal("Permission denied (%s).", authlist);
 433                 authctxt->method = method;
 434
 435                 /* reset the per method handler */
 436                 dispatch_range(SSH2_MSG_USERAUTH_PER_METHOD_MIN,
 437                     SSH2_MSG_USERAUTH_PER_METHOD_MAX, NULL);
 438
 439                 /* and try new method */
 440                 if (method->userauth(authctxt) != 0) {
 441                         debug2("we sent a %s packet, wait for reply", method->name);
 442                         break;
 443                 } else {
 444                         debug2("we did not send a packet, disable method");
 445                         method->enabled = NULL;
 446                 }
 447         }
 448 }
 449
 450 /* ARGSUSED */
 451 void
 452 input_userauth_error(int type, u_int32_t seq, void *ctxt)
 453 {
 454         fatal("input_userauth_error: bad message during authentication: "
 455             "type %d", type);
 456 }
 457
 458 /* ARGSUSED */
 459 void
 460 input_userauth_banner(int type, u_int32_t seq, void *ctxt)
 461 {
 462         char *msg, *raw, *lang;
 463         u_int len;
 464
 465         debug3("input_userauth_banner");
 466         raw = packet_get_string(&len);
 467         lang = packet_get_string(NULL);
 468         if (len > 0 && options.log_level >= SYSLOG_LEVEL_INFO) {
 469                 if (len > 65536)
 470                         len = 65536;
 471                 msg = xmalloc(len * 4 + 1); /* max expansion from strnvis() */
 472                 strnvis(msg, raw, len * 4 + 1, VIS_SAFE|VIS_OCTAL|VIS_NOSLASH);
 473                 fprintf(stderr, "%s", msg);
 474                 free(msg);
 475         }
 476         free(raw);
 477         free(lang);
 478 }
 479
 480 /* ARGSUSED */
 481 void
 482 input_userauth_success(int type, u_int32_t seq, void *ctxt)
 483 {
 484         Authctxt *authctxt = ctxt;
 485
 486         if (authctxt == NULL)
 487                 fatal("input_userauth_success: no authentication context");
 488         free(authctxt->authlist);
 489         authctxt->authlist = NULL;
 490         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 491                 authctxt->method->cleanup(authctxt);
 492         free(authctxt->methoddata);
 493         authctxt->methoddata = NULL;
 494         authctxt->success = 1;                  /* break out */
 495 }
 496
 497 void
 498 input_userauth_success_unexpected(int type, u_int32_t seq, void *ctxt)
 499 {
 500         Authctxt *authctxt = ctxt;
 501
 502         if (authctxt == NULL)
 503                 fatal("%s: no authentication context", __func__);
 504
 505         fatal("Unexpected authentication success during %s.",
 506             authctxt->method->name);
 507 }
 508
 509 /* ARGSUSED */
 510 void
 511 input_userauth_failure(int type, u_int32_t seq, void *ctxt)
 512 {
 513         Authctxt *authctxt = ctxt;
 514         char *authlist = NULL;
 515         int partial;
 516
 517         if (authctxt == NULL)
 518                 fatal("input_userauth_failure: no authentication context");
 519
 520         authlist = packet_get_string(NULL);
 521         partial = packet_get_char();
 522         packet_check_eom();
 523
 524         if (partial != 0) {
 525                 logit("Authenticated with partial success.");
 526                 /* reset state */
 527                 pubkey_cleanup(authctxt);
 528                 pubkey_prepare(authctxt);
 529         }
 530         debug("Authentications that can continue: %s", authlist);
 531
 532         userauth(authctxt, authlist);
 533 }
 534
 535 /* ARGSUSED */
 536 void
 537 input_userauth_pk_ok(int type, u_int32_t seq, void *ctxt)
 538 {
 539         Authctxt *authctxt = ctxt;
 540         Key *key = NULL;
 541         Identity *id = NULL;
 542         Buffer b;
 543         int pktype, sent = 0;
 544         u_int alen, blen;
 545         char *pkalg, *fp;
 546         u_char *pkblob;
 547
 548         if (authctxt == NULL)
 549                 fatal("input_userauth_pk_ok: no authentication context");
 550         if (datafellows & SSH_BUG_PKOK) {
 551                 /* this is similar to SSH_BUG_PKAUTH */
 552                 debug2("input_userauth_pk_ok: SSH_BUG_PKOK");
 553                 pkblob = packet_get_string(&blen);
 554                 buffer_init(&b);
 555                 buffer_append(&b, pkblob, blen);
 556                 pkalg = buffer_get_string(&b, &alen);
 557                 buffer_free(&b);
 558         } else {
 559                 pkalg = packet_get_string(&alen);
 560                 pkblob = packet_get_string(&blen);
 561         }
 562         packet_check_eom();
 563
 564         debug("Server accepts key: pkalg %s blen %u", pkalg, blen);
 565
 566         if ((pktype = key_type_from_name(pkalg)) == KEY_UNSPEC) {
 567                 debug("unknown pkalg %s", pkalg);
 568                 goto done;
 569         }
 570         if ((key = key_from_blob(pkblob, blen)) == NULL) {
 571                 debug("no key from blob. pkalg %s", pkalg);
 572                 goto done;
 573         }
 574         if (key->type != pktype) {
 575                 error("input_userauth_pk_ok: type mismatch "
 576                     "for decoded key (received %d, expected %d)",
 577                     key->type, pktype);
 578                 goto done;
 579         }
 580         fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
 581         debug2("input_userauth_pk_ok: fp %s", fp);
 582         free(fp);
 583
 584         /*
 585          * search keys in the reverse order, because last candidate has been
 586          * moved to the end of the queue.  this also avoids confusion by
 587          * duplicate keys
 588          */
 589         TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
 590                 if (key_equal(key, id->key)) {
 591                         sent = sign_and_send_pubkey(authctxt, id);
 592                         break;
 593                 }
 594         }
 595 done:
 596         if (key != NULL)
 597                 key_free(key);
 598         free(pkalg);
 599         free(pkblob);
 600
 601         /* try another method if we did not send a packet */
 602         if (sent == 0)
 603                 userauth(authctxt, NULL);
 604 }
 605
 606 #ifdef GSSAPI
 607 int
 608 userauth_gssapi(Authctxt *authctxt)
 609 {
 610         Gssctxt *gssctxt = NULL;
 611         static gss_OID_set gss_supported = NULL;
 612         static u_int mech = 0;
 613         OM_uint32 min;
 614         int ok = 0;
 615
 616         /* Try one GSSAPI method at a time, rather than sending them all at
 617          * once. */
 618
 619         if (gss_supported == NULL)
 620                 gss_indicate_mechs(&min, &gss_supported);
 621
 622         /* Check to see if the mechanism is usable before we offer it */
 623         while (mech < gss_supported->count && !ok) {
 624                 /* My DER encoding requires length<128 */
 625                 if (gss_supported->elements[mech].length < 128 &&
 626                     ssh_gssapi_check_mechanism(&gssctxt,
 627                     &gss_supported->elements[mech], authctxt->host)) {
 628                         ok = 1; /* Mechanism works */
 629                 } else {
 630                         mech++;
 631                 }
 632         }
 633
 634         if (!ok)
 635                 return 0;
 636
 637         authctxt->methoddata=(void *)gssctxt;
 638
 639         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 640         packet_put_cstring(authctxt->server_user);
 641         packet_put_cstring(authctxt->service);
 642         packet_put_cstring(authctxt->method->name);
 643
 644         packet_put_int(1);
 645
 646         packet_put_int((gss_supported->elements[mech].length) + 2);
 647         packet_put_char(SSH_GSS_OIDTYPE);
 648         packet_put_char(gss_supported->elements[mech].length);
 649         packet_put_raw(gss_supported->elements[mech].elements,
 650             gss_supported->elements[mech].length);
 651
 652         packet_send();
 653
 654         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
 655         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 656         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
 657         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 658
 659         mech++; /* Move along to next candidate */
 660
 661         return 1;
 662 }
 663
 664 static OM_uint32
 665 process_gssapi_token(void *ctxt, gss_buffer_t recv_tok)
 666 {
 667         Authctxt *authctxt = ctxt;
 668         Gssctxt *gssctxt = authctxt->methoddata;
 669         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 670         gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
 671         gss_buffer_desc gssbuf;
 672         OM_uint32 status, ms, flags;
 673         Buffer b;
 674
 675         status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 676             recv_tok, &send_tok, &flags);
 677
 678         if (send_tok.length > 0) {
 679                 if (GSS_ERROR(status))
 680                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 681                 else
 682                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 683
 684                 packet_put_string(send_tok.value, send_tok.length);
 685                 packet_send();
 686                 gss_release_buffer(&ms, &send_tok);
 687         }
 688
 689         if (status == GSS_S_COMPLETE) {
 690                 /* send either complete or MIC, depending on mechanism */
 691                 if (!(flags & GSS_C_INTEG_FLAG)) {
 692                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
 693                         packet_send();
 694                 } else {
 695                         ssh_gssapi_buildmic(&b, authctxt->server_user,
 696                             authctxt->service, "gssapi-with-mic");
 697
 698                         gssbuf.value = buffer_ptr(&b);
 699                         gssbuf.length = buffer_len(&b);
 700
 701                         status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);
 702
 703                         if (!GSS_ERROR(status)) {
 704                                 packet_start(SSH2_MSG_USERAUTH_GSSAPI_MIC);
 705                                 packet_put_string(mic.value, mic.length);
 706
 707                                 packet_send();
 708                         }
 709
 710                         buffer_free(&b);
 711                         gss_release_buffer(&ms, &mic);
 712                 }
 713         }
 714
 715         return status;
 716 }
 717
 718 /* ARGSUSED */
 719 void
 720 input_gssapi_response(int type, u_int32_t plen, void *ctxt)
 721 {
 722         Authctxt *authctxt = ctxt;
 723         Gssctxt *gssctxt;
 724         int oidlen;
 725         char *oidv;
 726
 727         if (authctxt == NULL)
 728                 fatal("input_gssapi_response: no authentication context");
 729         gssctxt = authctxt->methoddata;
 730
 731         /* Setup our OID */
 732         oidv = packet_get_string(&oidlen);
 733
 734         if (oidlen <= 2 ||
 735             oidv[0] != SSH_GSS_OIDTYPE ||
 736             oidv[1] != oidlen - 2) {
 737                 free(oidv);
 738                 debug("Badly encoded mechanism OID received");
 739                 userauth(authctxt, NULL);
 740                 return;
 741         }
 742
 743         if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
 744                 fatal("Server returned different OID than expected");
 745
 746         packet_check_eom();
 747
 748         free(oidv);
 749
 750         if (GSS_ERROR(process_gssapi_token(ctxt, GSS_C_NO_BUFFER))) {
 751                 /* Start again with next method on list */
 752                 debug("Trying to start again");
 753                 userauth(authctxt, NULL);
 754                 return;
 755         }
 756 }
 757
 758 /* ARGSUSED */
 759 void
 760 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 761 {
 762         Authctxt *authctxt = ctxt;
 763         gss_buffer_desc recv_tok;
 764         OM_uint32 status;
 765         u_int slen;
 766
 767         if (authctxt == NULL)
 768                 fatal("input_gssapi_response: no authentication context");
 769
 770         recv_tok.value = packet_get_string(&slen);
 771         recv_tok.length = slen; /* safe typecast */
 772
 773         packet_check_eom();
 774
 775         status = process_gssapi_token(ctxt, &recv_tok);
 776
 777         free(recv_tok.value);
 778
 779         if (GSS_ERROR(status)) {
 780                 /* Start again with the next method in the list */
 781                 userauth(authctxt, NULL);
 782                 return;
 783         }
 784 }
 785
 786 /* ARGSUSED */
 787 void
 788 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 789 {
 790         Authctxt *authctxt = ctxt;
 791         Gssctxt *gssctxt;
 792         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 793         gss_buffer_desc recv_tok;
 794         OM_uint32 ms;
 795         u_int len;
 796
 797         if (authctxt == NULL)
 798                 fatal("input_gssapi_response: no authentication context");
 799         gssctxt = authctxt->methoddata;
 800
 801         recv_tok.value = packet_get_string(&len);
 802         recv_tok.length = len;
 803
 804         packet_check_eom();
 805
 806         /* Stick it into GSSAPI and see what it says */
 807         (void)ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 808             &recv_tok, &send_tok, NULL);
 809
 810         free(recv_tok.value);
 811         gss_release_buffer(&ms, &send_tok);
 812
 813         /* Server will be returning a failed packet after this one */
 814 }
 815
 816 /* ARGSUSED */
 817 void
 818 input_gssapi_error(int type, u_int32_t plen, void *ctxt)
 819 {
 820         char *msg;
 821         char *lang;
 822
 823         /* maj */(void)packet_get_int();
 824         /* min */(void)packet_get_int();
 825         msg=packet_get_string(NULL);
 826         lang=packet_get_string(NULL);
 827
 828         packet_check_eom();
 829
 830         debug("Server GSSAPI Error:\n%s", msg);
 831         free(msg);
 832         free(lang);
 833 }
 834 #endif /* GSSAPI */
 835
 836 int
 837 userauth_none(Authctxt *authctxt)
 838 {
 839         /* initial userauth request */
 840         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 841         packet_put_cstring(authctxt->server_user);
 842         packet_put_cstring(authctxt->service);
 843         packet_put_cstring(authctxt->method->name);
 844         packet_send();
 845         return 1;
 846 }
 847
 848 int
 849 userauth_passwd(Authctxt *authctxt)
 850 {
 851         static int attempt = 0;
 852         char prompt[150];
 853         char *password;
 854         const char *host = options.host_key_alias ?  options.host_key_alias :
 855             authctxt->host;
 856
 857         if (attempt++ >= options.number_of_password_prompts)
 858                 return 0;
 859
 860         if (attempt != 1)
 861                 error("Permission denied, please try again.");
 862
 863         snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
 864             authctxt->server_user, host);
 865         password = read_passphrase(prompt, 0);
 866         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 867         packet_put_cstring(authctxt->server_user);
 868         packet_put_cstring(authctxt->service);
 869         packet_put_cstring(authctxt->method->name);
 870         packet_put_char(0);
 871         packet_put_cstring(password);
 872         explicit_bzero(password, strlen(password));
 873         free(password);
 874         packet_add_padding(64);
 875         packet_send();
 876
 877         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 878             &input_userauth_passwd_changereq);
 879
 880         return 1;
 881 }
 882
 883 /*
 884  * parse PASSWD_CHANGEREQ, prompt user and send SSH2_MSG_USERAUTH_REQUEST
 885  */
 886 /* ARGSUSED */
 887 void
 888 input_userauth_passwd_changereq(int type, u_int32_t seqnr, void *ctxt)
 889 {
 890         Authctxt *authctxt = ctxt;
 891         char *info, *lang, *password = NULL, *retype = NULL;
 892         char prompt[150];
 893         const char *host = options.host_key_alias ? options.host_key_alias :
 894             authctxt->host;
 895
 896         debug2("input_userauth_passwd_changereq");
 897
 898         if (authctxt == NULL)
 899                 fatal("input_userauth_passwd_changereq: "
 900                     "no authentication context");
 901
 902         info = packet_get_string(NULL);
 903         lang = packet_get_string(NULL);
 904         if (strlen(info) > 0)
 905                 logit("%s", info);
 906         free(info);
 907         free(lang);
 908         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 909         packet_put_cstring(authctxt->server_user);
 910         packet_put_cstring(authctxt->service);
 911         packet_put_cstring(authctxt->method->name);
 912         packet_put_char(1);                     /* additional info */
 913         snprintf(prompt, sizeof(prompt),
 914             "Enter %.30s@%.128s's old password: ",
 915             authctxt->server_user, host);
 916         password = read_passphrase(prompt, 0);
 917         packet_put_cstring(password);
 918         explicit_bzero(password, strlen(password));
 919         free(password);
 920         password = NULL;
 921         while (password == NULL) {
 922                 snprintf(prompt, sizeof(prompt),
 923                     "Enter %.30s@%.128s's new password: ",
 924                     authctxt->server_user, host);
 925                 password = read_passphrase(prompt, RP_ALLOW_EOF);
 926                 if (password == NULL) {
 927                         /* bail out */
 928                         return;
 929                 }
 930                 snprintf(prompt, sizeof(prompt),
 931                     "Retype %.30s@%.128s's new password: ",
 932                     authctxt->server_user, host);
 933                 retype = read_passphrase(prompt, 0);
 934                 if (strcmp(password, retype) != 0) {
 935                         explicit_bzero(password, strlen(password));
 936                         free(password);
 937                         logit("Mismatch; try again, EOF to quit.");
 938                         password = NULL;
 939                 }
 940                 explicit_bzero(retype, strlen(retype));
 941                 free(retype);
 942         }
 943         packet_put_cstring(password);
 944         explicit_bzero(password, strlen(password));
 945         free(password);
 946         packet_add_padding(64);
 947         packet_send();
 948
 949         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 950             &input_userauth_passwd_changereq);
 951 }
 952
 953 static int
 954 identity_sign(Identity *id, u_char **sigp, u_int *lenp,
 955     u_char *data, u_int datalen)
 956 {
 957         Key *prv;
 958         int ret;
 959
 960         /* the agent supports this key */
 961         if (id->ac)
 962                 return (ssh_agent_sign(id->ac, id->key, sigp, lenp,
 963                     data, datalen));
 964         /*
 965          * we have already loaded the private key or
 966          * the private key is stored in external hardware
 967          */
 968         if (id->isprivate || (id->key->flags & KEY_FLAG_EXT))
 969                 return (key_sign(id->key, sigp, lenp, data, datalen));
 970         /* load the private key from the file */
 971         if ((prv = load_identity_file(id->filename, id->userprovided)) == NULL)
 972                 return (-1);
 973         ret = key_sign(prv, sigp, lenp, data, datalen);
 974         key_free(prv);
 975         return (ret);
 976 }
 977
 978 static int
 979 sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
 980 {
 981         Buffer b;
 982         u_char *blob, *signature;
 983         u_int bloblen, slen;
 984         u_int skip = 0;
 985         int ret = -1;
 986         int have_sig = 1;
 987         char *fp;
 988
 989         fp = key_fingerprint(id->key, SSH_FP_MD5, SSH_FP_HEX);
 990         debug3("sign_and_send_pubkey: %s %s", key_type(id->key), fp);
 991         free(fp);
 992
 993         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
 994                 /* we cannot handle this key */
 995                 debug3("sign_and_send_pubkey: cannot handle key");
 996                 return 0;
 997         }
 998         /* data to be signed */
 999         buffer_init(&b);
1000         if (datafellows & SSH_OLD_SESSIONID) {
1001                 buffer_append(&b, session_id2, session_id2_len);
1002                 skip = session_id2_len;
1003         } else {
1004                 buffer_put_string(&b, session_id2, session_id2_len);
1005                 skip = buffer_len(&b);
1006         }
1007         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1008         buffer_put_cstring(&b, authctxt->server_user);
1009         buffer_put_cstring(&b,
1010             datafellows & SSH_BUG_PKSERVICE ?
1011             "ssh-userauth" :
1012             authctxt->service);
1013         if (datafellows & SSH_BUG_PKAUTH) {
1014                 buffer_put_char(&b, have_sig);
1015         } else {
1016                 buffer_put_cstring(&b, authctxt->method->name);
1017                 buffer_put_char(&b, have_sig);
1018                 buffer_put_cstring(&b, key_ssh_name(id->key));
1019         }
1020         buffer_put_string(&b, blob, bloblen);
1021
1022         /* generate signature */
1023         ret = identity_sign(id, &signature, &slen,
1024             buffer_ptr(&b), buffer_len(&b));
1025         if (ret == -1) {
1026                 free(blob);
1027                 buffer_free(&b);
1028                 return 0;
1029         }
1030 #ifdef DEBUG_PK
1031         buffer_dump(&b);
1032 #endif
1033         if (datafellows & SSH_BUG_PKSERVICE) {
1034                 buffer_clear(&b);
1035                 buffer_append(&b, session_id2, session_id2_len);
1036                 skip = session_id2_len;
1037                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1038                 buffer_put_cstring(&b, authctxt->server_user);
1039                 buffer_put_cstring(&b, authctxt->service);
1040                 buffer_put_cstring(&b, authctxt->method->name);
1041                 buffer_put_char(&b, have_sig);
1042                 if (!(datafellows & SSH_BUG_PKAUTH))
1043                         buffer_put_cstring(&b, key_ssh_name(id->key));
1044                 buffer_put_string(&b, blob, bloblen);
1045         }
1046         free(blob);
1047
1048         /* append signature */
1049         buffer_put_string(&b, signature, slen);
1050         free(signature);
1051
1052         /* skip session id and packet type */
1053         if (buffer_len(&b) < skip + 1)
1054                 fatal("userauth_pubkey: internal error");
1055         buffer_consume(&b, skip + 1);
1056
1057         /* put remaining data from buffer into packet */
1058         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1059         packet_put_raw(buffer_ptr(&b), buffer_len(&b));
1060         buffer_free(&b);
1061         packet_send();
1062
1063         return 1;
1064 }
1065
1066 static int
1067 send_pubkey_test(Authctxt *authctxt, Identity *id)
1068 {
1069         u_char *blob;
1070         u_int bloblen, have_sig = 0;
1071
1072         debug3("send_pubkey_test");
1073
1074         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1075                 /* we cannot handle this key */
1076                 debug3("send_pubkey_test: cannot handle key");
1077                 return 0;
1078         }
1079         /* register callback for USERAUTH_PK_OK message */
1080         dispatch_set(SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
1081
1082         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1083         packet_put_cstring(authctxt->server_user);
1084         packet_put_cstring(authctxt->service);
1085         packet_put_cstring(authctxt->method->name);
1086         packet_put_char(have_sig);
1087         if (!(datafellows & SSH_BUG_PKAUTH))
1088                 packet_put_cstring(key_ssh_name(id->key));
1089         packet_put_string(blob, bloblen);
1090         free(blob);
1091         packet_send();
1092         return 1;
1093 }
1094
1095 static Key *
1096 load_identity_file(char *filename, int userprovided)
1097 {
1098         Key *private;
1099         char prompt[300], *passphrase;
1100         int perm_ok = 0, quit, i;
1101         struct stat st;
1102
1103         if (stat(filename, &st) < 0) {
1104                 (userprovided ? logit : debug3)("no such identity: %s: %s",
1105                     filename, strerror(errno));
1106                 return NULL;
1107         }
1108         private = key_load_private_type(KEY_UNSPEC, filename, "", NULL, &perm_ok);
1109         if (!perm_ok) {
1110                 if (private != NULL)
1111                         key_free(private);
1112                 return NULL;
1113         }
1114         if (private == NULL) {
1115                 if (options.batch_mode)
1116                         return NULL;
1117                 snprintf(prompt, sizeof prompt,
1118                     "Enter passphrase for key '%.100s': ", filename);
1119                 for (i = 0; i < options.number_of_password_prompts; i++) {
1120                         passphrase = read_passphrase(prompt, 0);
1121                         if (strcmp(passphrase, "") != 0) {
1122                                 private = key_load_private_type(KEY_UNSPEC,
1123                                     filename, passphrase, NULL, NULL);
1124                                 quit = 0;
1125                         } else {
1126                                 debug2("no passphrase given, try next key");
1127                                 quit = 1;
1128                         }
1129                         explicit_bzero(passphrase, strlen(passphrase));
1130                         free(passphrase);
1131                         if (private != NULL || quit)
1132                                 break;
1133                         debug2("bad passphrase given, try again...");
1134                 }
1135         }
1136         return private;
1137 }
1138
1139 /*
1140  * try keys in the following order:
1141  *      1. agent keys that are found in the config file
1142  *      2. other agent keys
1143  *      3. keys that are only listed in the config file
1144  */
1145 static void
1146 pubkey_prepare(Authctxt *authctxt)
1147 {
1148         Identity *id, *id2, *tmp;
1149         Idlist agent, files, *preferred;
1150         Key *key;
1151         AuthenticationConnection *ac;
1152         char *comment;
1153         int i, found;
1154
1155         TAILQ_INIT(&agent);     /* keys from the agent */
1156         TAILQ_INIT(&files);     /* keys from the config file */
1157         preferred = &authctxt->keys;
1158         TAILQ_INIT(preferred);  /* preferred order of keys */
1159
1160         /* list of keys stored in the filesystem and PKCS#11 */
1161         for (i = 0; i < options.num_identity_files; i++) {
1162                 key = options.identity_keys[i];
1163                 if (key && key->type == KEY_RSA1)
1164                         continue;
1165                 if (key && key->cert && key->cert->type != SSH2_CERT_TYPE_USER)
1166                         continue;
1167                 options.identity_keys[i] = NULL;
1168                 id = xcalloc(1, sizeof(*id));
1169                 id->key = key;
1170                 id->filename = xstrdup(options.identity_files[i]);
1171                 id->userprovided = options.identity_file_userprovided[i];
1172                 TAILQ_INSERT_TAIL(&files, id, next);
1173         }
1174         /* Prefer PKCS11 keys that are explicitly listed */
1175         TAILQ_FOREACH_SAFE(id, &files, next, tmp) {
1176                 if (id->key == NULL || (id->key->flags & KEY_FLAG_EXT) == 0)
1177                         continue;
1178                 found = 0;
1179                 TAILQ_FOREACH(id2, &files, next) {
1180                         if (id2->key == NULL ||
1181                             (id2->key->flags & KEY_FLAG_EXT) != 0)
1182                                 continue;
1183                         if (key_equal(id->key, id2->key)) {
1184                                 TAILQ_REMOVE(&files, id, next);
1185                                 TAILQ_INSERT_TAIL(preferred, id, next);
1186                                 found = 1;
1187                                 break;
1188                         }
1189                 }
1190                 /* If IdentitiesOnly set and key not found then don't use it */
1191                 if (!found && options.identities_only) {
1192                         TAILQ_REMOVE(&files, id, next);
1193                         explicit_bzero(id, sizeof(*id));
1194                         free(id);
1195                 }
1196         }
1197         /* list of keys supported by the agent */
1198         if ((ac = ssh_get_authentication_connection())) {
1199                 for (key = ssh_get_first_identity(ac, &comment, 2);
1200                     key != NULL;
1201                     key = ssh_get_next_identity(ac, &comment, 2)) {
1202                         found = 0;
1203                         TAILQ_FOREACH(id, &files, next) {
1204                                 /* agent keys from the config file are preferred */
1205                                 if (key_equal(key, id->key)) {
1206                                         key_free(key);
1207                                         free(comment);
1208                                         TAILQ_REMOVE(&files, id, next);
1209                                         TAILQ_INSERT_TAIL(preferred, id, next);
1210                                         id->ac = ac;
1211                                         found = 1;
1212                                         break;
1213                                 }
1214                         }
1215                         if (!found && !options.identities_only) {
1216                                 id = xcalloc(1, sizeof(*id));
1217                                 id->key = key;
1218                                 id->filename = comment;
1219                                 id->ac = ac;
1220                                 TAILQ_INSERT_TAIL(&agent, id, next);
1221                         }
1222                 }
1223                 /* append remaining agent keys */
1224                 for (id = TAILQ_FIRST(&agent); id; id = TAILQ_FIRST(&agent)) {
1225                         TAILQ_REMOVE(&agent, id, next);
1226                         TAILQ_INSERT_TAIL(preferred, id, next);
1227                 }
1228                 authctxt->agent = ac;
1229         }
1230         /* append remaining keys from the config file */
1231         for (id = TAILQ_FIRST(&files); id; id = TAILQ_FIRST(&files)) {
1232                 TAILQ_REMOVE(&files, id, next);
1233                 TAILQ_INSERT_TAIL(preferred, id, next);
1234         }
1235         TAILQ_FOREACH(id, preferred, next) {
1236                 debug2("key: %s (%p),%s", id->filename, id->key,
1237                     id->userprovided ? " explicit" : "");
1238         }
1239 }
1240
1241 static void
1242 pubkey_cleanup(Authctxt *authctxt)
1243 {
1244         Identity *id;
1245
1246         if (authctxt->agent != NULL)
1247                 ssh_close_authentication_connection(authctxt->agent);
1248         for (id = TAILQ_FIRST(&authctxt->keys); id;
1249             id = TAILQ_FIRST(&authctxt->keys)) {
1250                 TAILQ_REMOVE(&authctxt->keys, id, next);
1251                 if (id->key)
1252                         key_free(id->key);
1253                 free(id->filename);
1254                 free(id);
1255         }
1256 }
1257
1258 int
1259 userauth_pubkey(Authctxt *authctxt)
1260 {
1261         Identity *id;
1262         int sent = 0;
1263
1264         while ((id = TAILQ_FIRST(&authctxt->keys))) {
1265                 if (id->tried++)
1266                         return (0);
1267                 /* move key to the end of the queue */
1268                 TAILQ_REMOVE(&authctxt->keys, id, next);
1269                 TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
1270                 /*
1271                  * send a test message if we have the public key. for
1272                  * encrypted keys we cannot do this and have to load the
1273                  * private key instead
1274                  */
1275                 if (id->key != NULL) {
1276                         if (key_type_plain(id->key->type) == KEY_RSA &&
1277                             (datafellows & SSH_BUG_RSASIGMD5) != 0) {
1278                                 debug("Skipped %s key %s for RSA/MD5 server",
1279                                     key_type(id->key), id->filename);
1280                         } else if (id->key->type != KEY_RSA1) {
1281                                 debug("Offering %s public key: %s",
1282                                     key_type(id->key), id->filename);
1283                                 sent = send_pubkey_test(authctxt, id);
1284                         }
1285                 } else {
1286                         debug("Trying private key: %s", id->filename);
1287                         id->key = load_identity_file(id->filename,
1288                             id->userprovided);
1289                         if (id->key != NULL) {
1290                                 id->isprivate = 1;
1291                                 if (key_type_plain(id->key->type) == KEY_RSA &&
1292                                     (datafellows & SSH_BUG_RSASIGMD5) != 0) {
1293                                         debug("Skipped %s key %s for RSA/MD5 "
1294                                             "server", key_type(id->key),
1295                                             id->filename);
1296                                 } else {
1297                                         sent = sign_and_send_pubkey(
1298                                             authctxt, id);
1299                                 }
1300                                 key_free(id->key);
1301                                 id->key = NULL;
1302                         }
1303                 }
1304                 if (sent)
1305                         return (sent);
1306         }
1307         return (0);
1308 }
1309
1310 /*
1311  * Send userauth request message specifying keyboard-interactive method.
1312  */
1313 int
1314 userauth_kbdint(Authctxt *authctxt)
1315 {
1316         static int attempt = 0;
1317
1318         if (attempt++ >= options.number_of_password_prompts)
1319                 return 0;
1320         /* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
1321         if (attempt > 1 && !authctxt->info_req_seen) {
1322                 debug3("userauth_kbdint: disable: no info_req_seen");
1323                 dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
1324                 return 0;
1325         }
1326
1327         debug2("userauth_kbdint");
1328         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1329         packet_put_cstring(authctxt->server_user);
1330         packet_put_cstring(authctxt->service);
1331         packet_put_cstring(authctxt->method->name);
1332         packet_put_cstring("");                                 /* lang */
1333         packet_put_cstring(options.kbd_interactive_devices ?
1334             options.kbd_interactive_devices : "");
1335         packet_send();
1336
1337         dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
1338         return 1;
1339 }
1340
1341 /*
1342  * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
1343  */
1344 void
1345 input_userauth_info_req(int type, u_int32_t seq, void *ctxt)
1346 {
1347         Authctxt *authctxt = ctxt;
1348         char *name, *inst, *lang, *prompt, *response;
1349         u_int num_prompts, i;
1350         int echo = 0;
1351
1352         debug2("input_userauth_info_req");
1353
1354         if (authctxt == NULL)
1355                 fatal("input_userauth_info_req: no authentication context");
1356
1357         authctxt->info_req_seen = 1;
1358
1359         name = packet_get_string(NULL);
1360         inst = packet_get_string(NULL);
1361         lang = packet_get_string(NULL);
1362         if (strlen(name) > 0)
1363                 logit("%s", name);
1364         if (strlen(inst) > 0)
1365                 logit("%s", inst);
1366         free(name);
1367         free(inst);
1368         free(lang);
1369
1370         num_prompts = packet_get_int();
1371         /*
1372          * Begin to build info response packet based on prompts requested.
1373          * We commit to providing the correct number of responses, so if
1374          * further on we run into a problem that prevents this, we have to
1375          * be sure and clean this up and send a correct error response.
1376          */
1377         packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
1378         packet_put_int(num_prompts);
1379
1380         debug2("input_userauth_info_req: num_prompts %d", num_prompts);
1381         for (i = 0; i < num_prompts; i++) {
1382                 prompt = packet_get_string(NULL);
1383                 echo = packet_get_char();
1384
1385                 response = read_passphrase(prompt, echo ? RP_ECHO : 0);
1386
1387                 packet_put_cstring(response);
1388                 explicit_bzero(response, strlen(response));
1389                 free(response);
1390                 free(prompt);
1391         }
1392         packet_check_eom(); /* done with parsing incoming message. */
1393
1394         packet_add_padding(64);
1395         packet_send();
1396 }
1397
1398 static int
1399 ssh_keysign(Key *key, u_char **sigp, u_int *lenp,
1400     u_char *data, u_int datalen)
1401 {
1402         Buffer b;
1403         struct stat st;
1404         pid_t pid;
1405         int to[2], from[2], status, version = 2;
1406
1407         debug2("ssh_keysign called");
1408
1409         if (stat(_PATH_SSH_KEY_SIGN, &st) < 0) {
1410                 error("ssh_keysign: not installed: %s", strerror(errno));
1411                 return -1;
1412         }
1413         if (fflush(stdout) != 0)
1414                 error("ssh_keysign: fflush: %s", strerror(errno));
1415         if (pipe(to) < 0) {
1416                 error("ssh_keysign: pipe: %s", strerror(errno));
1417                 return -1;
1418         }
1419         if (pipe(from) < 0) {
1420                 error("ssh_keysign: pipe: %s", strerror(errno));
1421                 return -1;
1422         }
1423         if ((pid = fork()) < 0) {
1424                 error("ssh_keysign: fork: %s", strerror(errno));
1425                 return -1;
1426         }
1427         if (pid == 0) {
1428                 /* keep the socket on exec */
1429                 fcntl(packet_get_connection_in(), F_SETFD, 0);
1430                 permanently_drop_suid(getuid());
1431                 close(from[0]);
1432                 if (dup2(from[1], STDOUT_FILENO) < 0)
1433                         fatal("ssh_keysign: dup2: %s", strerror(errno));
1434                 close(to[1]);
1435                 if (dup2(to[0], STDIN_FILENO) < 0)
1436                         fatal("ssh_keysign: dup2: %s", strerror(errno));
1437                 close(from[1]);
1438                 close(to[0]);
1439                 execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *) 0);
1440                 fatal("ssh_keysign: exec(%s): %s", _PATH_SSH_KEY_SIGN,
1441                     strerror(errno));
1442         }
1443         close(from[1]);
1444         close(to[0]);
1445
1446         buffer_init(&b);
1447         buffer_put_int(&b, packet_get_connection_in()); /* send # of socket */
1448         buffer_put_string(&b, data, datalen);
1449         if (ssh_msg_send(to[1], version, &b) == -1)
1450                 fatal("ssh_keysign: couldn't send request");
1451
1452         if (ssh_msg_recv(from[0], &b) < 0) {
1453                 error("ssh_keysign: no reply");
1454                 buffer_free(&b);
1455                 return -1;
1456         }
1457         close(from[0]);
1458         close(to[1]);
1459
1460         while (waitpid(pid, &status, 0) < 0)
1461                 if (errno != EINTR)
1462                         break;
1463
1464         if (buffer_get_char(&b) != version) {
1465                 error("ssh_keysign: bad version");
1466                 buffer_free(&b);
1467                 return -1;
1468         }
1469         *sigp = buffer_get_string(&b, lenp);
1470         buffer_free(&b);
1471
1472         return 0;
1473 }
1474
1475 int
1476 userauth_hostbased(Authctxt *authctxt)
1477 {
1478         Key *private = NULL;
1479         Sensitive *sensitive = authctxt->sensitive;
1480         Buffer b;
1481         u_char *signature, *blob;
1482         char *chost, *pkalg, *p;
1483         const char *service;
1484         u_int blen, slen;
1485         int ok, i, found = 0;
1486
1487         /* check for a useful key */
1488         for (i = 0; i < sensitive->nkeys; i++) {
1489                 private = sensitive->keys[i];
1490                 if (private && private->type != KEY_RSA1) {
1491                         found = 1;
1492                         /* we take and free the key */
1493                         sensitive->keys[i] = NULL;
1494                         break;
1495                 }
1496         }
1497         if (!found) {
1498                 debug("No more client hostkeys for hostbased authentication.");
1499                 return 0;
1500         }
1501         if (key_to_blob(private, &blob, &blen) == 0) {
1502                 key_free(private);
1503                 return 0;
1504         }
1505         /* figure out a name for the client host */
1506         p = get_local_name(packet_get_connection_in());
1507         if (p == NULL) {
1508                 error("userauth_hostbased: cannot get local ipaddr/name");
1509                 key_free(private);
1510                 free(blob);
1511                 return 0;
1512         }
1513         xasprintf(&chost, "%s.", p);
1514         debug2("userauth_hostbased: chost %s", chost);
1515         free(p);
1516
1517         service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
1518             authctxt->service;
1519         pkalg = xstrdup(key_ssh_name(private));
1520         buffer_init(&b);
1521         /* construct data */
1522         buffer_put_string(&b, session_id2, session_id2_len);
1523         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1524         buffer_put_cstring(&b, authctxt->server_user);
1525         buffer_put_cstring(&b, service);
1526         buffer_put_cstring(&b, authctxt->method->name);
1527         buffer_put_cstring(&b, pkalg);
1528         buffer_put_string(&b, blob, blen);
1529         buffer_put_cstring(&b, chost);
1530         buffer_put_cstring(&b, authctxt->local_user);
1531 #ifdef DEBUG_PK
1532         buffer_dump(&b);
1533 #endif
1534         if (sensitive->external_keysign)
1535                 ok = ssh_keysign(private, &signature, &slen,
1536                     buffer_ptr(&b), buffer_len(&b));
1537         else
1538                 ok = key_sign(private, &signature, &slen,
1539                     buffer_ptr(&b), buffer_len(&b));
1540         key_free(private);
1541         buffer_free(&b);
1542         if (ok != 0) {
1543                 error("key_sign failed");
1544                 free(chost);
1545                 free(pkalg);
1546                 free(blob);
1547                 return 0;
1548         }
1549         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1550         packet_put_cstring(authctxt->server_user);
1551         packet_put_cstring(authctxt->service);
1552         packet_put_cstring(authctxt->method->name);
1553         packet_put_cstring(pkalg);
1554         packet_put_string(blob, blen);
1555         packet_put_cstring(chost);
1556         packet_put_cstring(authctxt->local_user);
1557         packet_put_string(signature, slen);
1558         explicit_bzero(signature, slen);
1559         free(signature);
1560         free(chost);
1561         free(pkalg);
1562         free(blob);
1563
1564         packet_send();
1565         return 1;
1566 }
1567
1568 /* find auth method */
1569
1570 /*
1571  * given auth method name, if configurable options permit this method fill
1572  * in auth_ident field and return true, otherwise return false.
1573  */
1574 static int
1575 authmethod_is_enabled(Authmethod *method)
1576 {
1577         if (method == NULL)
1578                 return 0;
1579         /* return false if options indicate this method is disabled */
1580         if  (method->enabled == NULL || *method->enabled == 0)
1581                 return 0;
1582         /* return false if batch mode is enabled but method needs interactive mode */
1583         if  (method->batch_flag != NULL && *method->batch_flag != 0)
1584                 return 0;
1585         return 1;
1586 }
1587
1588 static Authmethod *
1589 authmethod_lookup(const char *name)
1590 {
1591         Authmethod *method = NULL;
1592         if (name != NULL)
1593                 for (method = authmethods; method->name != NULL; method++)
1594                         if (strcmp(name, method->name) == 0)
1595                                 return method;
1596         debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
1597         return NULL;
1598 }
1599
1600 /* XXX internal state */
1601 static Authmethod *current = NULL;
1602 static char *supported = NULL;
1603 static char *preferred = NULL;
1604
1605 /*
1606  * Given the authentication method list sent by the server, return the
1607  * next method we should try.  If the server initially sends a nil list,
1608  * use a built-in default list.
1609  */
1610 static Authmethod *
1611 authmethod_get(char *authlist)
1612 {
1613         char *name = NULL;
1614         u_int next;
1615
1616         /* Use a suitable default if we're passed a nil list.  */
1617         if (authlist == NULL || strlen(authlist) == 0)
1618                 authlist = options.preferred_authentications;
1619
1620         if (supported == NULL || strcmp(authlist, supported) != 0) {
1621                 debug3("start over, passed a different list %s", authlist);
1622                 free(supported);
1623                 supported = xstrdup(authlist);
1624                 preferred = options.preferred_authentications;
1625                 debug3("preferred %s", preferred);
1626                 current = NULL;
1627         } else if (current != NULL && authmethod_is_enabled(current))
1628                 return current;
1629
1630         for (;;) {
1631                 if ((name = match_list(preferred, supported, &next)) == NULL) {
1632                         debug("No more authentication methods to try.");
1633                         current = NULL;
1634                         return NULL;
1635                 }
1636                 preferred += next;
1637                 debug3("authmethod_lookup %s", name);
1638                 debug3("remaining preferred: %s", preferred);
1639                 if ((current = authmethod_lookup(name)) != NULL &&
1640                     authmethod_is_enabled(current)) {
1641                         debug3("authmethod_is_enabled %s", name);
1642                         debug("Next authentication method: %s", name);
1643                         free(name);
1644                         return current;
1645                 }
1646                 free(name);
1647         }
1648 }
1649
1650 static char *
1651 authmethods_get(void)
1652 {
1653         Authmethod *method = NULL;
1654         Buffer b;
1655         char *list;
1656
1657         buffer_init(&b);
1658         for (method = authmethods; method->name != NULL; method++) {
1659                 if (authmethod_is_enabled(method)) {
1660                         if (buffer_len(&b) > 0)
1661                                 buffer_append(&b, ",", 1);
1662                         buffer_append(&b, method->name, strlen(method->name));
1663                 }
1664         }
1665         buffer_append(&b, "\0", 1);
1666         list = xstrdup(buffer_ptr(&b));
1667         buffer_free(&b);
1668         return list;
1669 }
1670