crypto/openssh/sshconnect2.c

   1 /* $OpenBSD: sshconnect2.c,v 1.189 2012/06/22 12:30:26 dtucker Exp $ */
   2 /* $FreeBSD$ */
   3 /*
   4  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   5  * Copyright (c) 2008 Damien Miller.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #include "includes.h"
  29
  30 #include <sys/types.h>
  31 #include <sys/socket.h>
  32 #include <sys/wait.h>
  33 #include <sys/stat.h>
  34
  35 #include <errno.h>
  36 #include <fcntl.h>
  37 #include <netdb.h>
  38 #include <pwd.h>
  39 #include <signal.h>
  40 #include <stdarg.h>
  41 #include <stdio.h>
  42 #include <string.h>
  43 #include <unistd.h>
  44 #if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H)
  45 #include <vis.h>
  46 #endif
  47
  48 #include "openbsd-compat/sys-queue.h"
  49
  50 #include "xmalloc.h"
  51 #include "ssh.h"
  52 #include "ssh2.h"
  53 #include "buffer.h"
  54 #include "packet.h"
  55 #include "compat.h"
  56 #include "cipher.h"
  57 #include "key.h"
  58 #include "kex.h"
  59 #include "myproposal.h"
  60 #include "sshconnect.h"
  61 #include "authfile.h"
  62 #include "dh.h"
  63 #include "authfd.h"
  64 #include "log.h"
  65 #include "readconf.h"
  66 #include "misc.h"
  67 #include "match.h"
  68 #include "dispatch.h"
  69 #include "canohost.h"
  70 #include "msg.h"
  71 #include "pathnames.h"
  72 #include "uidswap.h"
  73 #include "hostfile.h"
  74 #include "schnorr.h"
  75 #include "jpake.h"
  76
  77 #ifdef GSSAPI
  78 #include "ssh-gss.h"
  79 #endif
  80
  81 /* import */
  82 extern char *client_version_string;
  83 extern char *server_version_string;
  84 extern Options options;
  85 #ifdef  NONE_CIPHER_ENABLED
  86 extern Kex *xxx_kex;
  87
  88 /*
  89  * tty_flag is set in ssh.c so we can use it here.  If set then prevent
  90  * the switch to the null cipher.
  91  */
  92
  93 extern int tty_flag;
  94 #endif
  95
  96 /*
  97  * SSH2 key exchange
  98  */
  99
 100 u_char *session_id2 = NULL;
 101 u_int session_id2_len = 0;
 102
 103 char *xxx_host;
 104 struct sockaddr *xxx_hostaddr;
 105
 106 Kex *xxx_kex = NULL;
 107
 108 static int
 109 verify_host_key_callback(Key *hostkey)
 110 {
 111         if (verify_host_key(xxx_host, xxx_hostaddr, hostkey) == -1)
 112                 fatal("Host key verification failed.");
 113         return 0;
 114 }
 115
 116 static char *
 117 order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
 118 {
 119         char *oavail, *avail, *first, *last, *alg, *hostname, *ret;
 120         size_t maxlen;
 121         struct hostkeys *hostkeys;
 122         int ktype;
 123         u_int i;
 124
 125         /* Find all hostkeys for this hostname */
 126         get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
 127         hostkeys = init_hostkeys();
 128         for (i = 0; i < options.num_user_hostfiles; i++)
 129                 load_hostkeys(hostkeys, hostname, options.user_hostfiles[i]);
 130         for (i = 0; i < options.num_system_hostfiles; i++)
 131                 load_hostkeys(hostkeys, hostname, options.system_hostfiles[i]);
 132
 133         oavail = avail = xstrdup(KEX_DEFAULT_PK_ALG);
 134         maxlen = strlen(avail) + 1;
 135         first = xmalloc(maxlen);
 136         last = xmalloc(maxlen);
 137         *first = *last = '\0';
 138
 139 #define ALG_APPEND(to, from) \
 140         do { \
 141                 if (*to != '\0') \
 142                         strlcat(to, ",", maxlen); \
 143                 strlcat(to, from, maxlen); \
 144         } while (0)
 145
 146         while ((alg = strsep(&avail, ",")) && *alg != '\0') {
 147                 if ((ktype = key_type_from_name(alg)) == KEY_UNSPEC)
 148                         fatal("%s: unknown alg %s", __func__, alg);
 149                 if (lookup_key_in_hostkeys_by_type(hostkeys,
 150                     key_type_plain(ktype), NULL))
 151                         ALG_APPEND(first, alg);
 152                 else
 153                         ALG_APPEND(last, alg);
 154         }
 155 #undef ALG_APPEND
 156         xasprintf(&ret, "%s%s%s", first, *first == '\0' ? "" : ",", last);
 157         if (*first != '\0')
 158                 debug3("%s: prefer hostkeyalgs: %s", __func__, first);
 159
 160         xfree(first);
 161         xfree(last);
 162         xfree(hostname);
 163         xfree(oavail);
 164         free_hostkeys(hostkeys);
 165
 166         return ret;
 167 }
 168
 169 void
 170 ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 171 {
 172         Kex *kex;
 173
 174         xxx_host = host;
 175         xxx_hostaddr = hostaddr;
 176
 177         if (options.ciphers == (char *)-1) {
 178                 logit("No valid ciphers for protocol version 2 given, using defaults.");
 179                 options.ciphers = NULL;
 180         }
 181         if (options.ciphers != NULL) {
 182                 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 183                 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
 184         }
 185         myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 186             compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
 187         myproposal[PROPOSAL_ENC_ALGS_STOC] =
 188             compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
 189         if (options.compression) {
 190                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 191                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib@openssh.com,zlib,none";
 192         } else {
 193                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 194                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com,zlib";
 195         }
 196         if (options.macs != NULL) {
 197                 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
 198                 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
 199         }
 200         if (options.hostkeyalgorithms != NULL)
 201                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 202                     options.hostkeyalgorithms;
 203         else {
 204                 /* Prefer algorithms that we already have keys for */
 205                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 206                     order_hostkeyalgs(host, hostaddr, port);
 207         }
 208         if (options.kex_algorithms != NULL)
 209                 myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms;
 210
 211         if (options.rekey_limit)
 212                 packet_set_rekey_limit((u_int32_t)options.rekey_limit);
 213
 214         /* start key exchange */
 215         kex = kex_setup(myproposal);
 216         kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 217         kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
 218         kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
 219         kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 220         kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
 221         kex->client_version_string=client_version_string;
 222         kex->server_version_string=server_version_string;
 223         kex->verify_host_key=&verify_host_key_callback;
 224
 225         xxx_kex = kex;
 226
 227         dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
 228
 229         if (options.use_roaming && !kex->roaming) {
 230                 debug("Roaming not allowed by server");
 231                 options.use_roaming = 0;
 232         }
 233
 234         session_id2 = kex->session_id;
 235         session_id2_len = kex->session_id_len;
 236
 237 #ifdef DEBUG_KEXDH
 238         /* send 1st encrypted/maced/compressed message */
 239         packet_start(SSH2_MSG_IGNORE);
 240         packet_put_cstring("markus");
 241         packet_send();
 242         packet_write_wait();
 243 #endif
 244 }
 245
 246 /*
 247  * Authenticate user
 248  */
 249
 250 typedef struct Authctxt Authctxt;
 251 typedef struct Authmethod Authmethod;
 252 typedef struct identity Identity;
 253 typedef struct idlist Idlist;
 254
 255 struct identity {
 256         TAILQ_ENTRY(identity) next;
 257         AuthenticationConnection *ac;   /* set if agent supports key */
 258         Key     *key;                   /* public/private key */
 259         char    *filename;              /* comment for agent-only keys */
 260         int     tried;
 261         int     isprivate;              /* key points to the private key */
 262 };
 263 TAILQ_HEAD(idlist, identity);
 264
 265 struct Authctxt {
 266         const char *server_user;
 267         const char *local_user;
 268         const char *host;
 269         const char *service;
 270         Authmethod *method;
 271         sig_atomic_t success;
 272         char *authlist;
 273         /* pubkey */
 274         Idlist keys;
 275         AuthenticationConnection *agent;
 276         /* hostbased */
 277         Sensitive *sensitive;
 278         /* kbd-interactive */
 279         int info_req_seen;
 280         /* generic */
 281         void *methoddata;
 282 };
 283 struct Authmethod {
 284         char    *name;          /* string to compare against server's list */
 285         int     (*userauth)(Authctxt *authctxt);
 286         void    (*cleanup)(Authctxt *authctxt);
 287         int     *enabled;       /* flag in option struct that enables method */
 288         int     *batch_flag;    /* flag in option struct that disables method */
 289 };
 290
 291 void    input_userauth_success(int, u_int32_t, void *);
 292 void    input_userauth_success_unexpected(int, u_int32_t, void *);
 293 void    input_userauth_failure(int, u_int32_t, void *);
 294 void    input_userauth_banner(int, u_int32_t, void *);
 295 void    input_userauth_error(int, u_int32_t, void *);
 296 void    input_userauth_info_req(int, u_int32_t, void *);
 297 void    input_userauth_pk_ok(int, u_int32_t, void *);
 298 void    input_userauth_passwd_changereq(int, u_int32_t, void *);
 299 void    input_userauth_jpake_server_step1(int, u_int32_t, void *);
 300 void    input_userauth_jpake_server_step2(int, u_int32_t, void *);
 301 void    input_userauth_jpake_server_confirm(int, u_int32_t, void *);
 302
 303 int     userauth_none(Authctxt *);
 304 int     userauth_pubkey(Authctxt *);
 305 int     userauth_passwd(Authctxt *);
 306 int     userauth_kbdint(Authctxt *);
 307 int     userauth_hostbased(Authctxt *);
 308 int     userauth_jpake(Authctxt *);
 309
 310 void    userauth_jpake_cleanup(Authctxt *);
 311
 312 #ifdef GSSAPI
 313 int     userauth_gssapi(Authctxt *authctxt);
 314 void    input_gssapi_response(int type, u_int32_t, void *);
 315 void    input_gssapi_token(int type, u_int32_t, void *);
 316 void    input_gssapi_hash(int type, u_int32_t, void *);
 317 void    input_gssapi_error(int, u_int32_t, void *);
 318 void    input_gssapi_errtok(int, u_int32_t, void *);
 319 #endif
 320
 321 void    userauth(Authctxt *, char *);
 322
 323 static int sign_and_send_pubkey(Authctxt *, Identity *);
 324 static void pubkey_prepare(Authctxt *);
 325 static void pubkey_cleanup(Authctxt *);
 326 static Key *load_identity_file(char *);
 327
 328 static Authmethod *authmethod_get(char *authlist);
 329 static Authmethod *authmethod_lookup(const char *name);
 330 static char *authmethods_get(void);
 331
 332 Authmethod authmethods[] = {
 333 #ifdef GSSAPI
 334         {"gssapi-with-mic",
 335                 userauth_gssapi,
 336                 NULL,
 337                 &options.gss_authentication,
 338                 NULL},
 339 #endif
 340         {"hostbased",
 341                 userauth_hostbased,
 342                 NULL,
 343                 &options.hostbased_authentication,
 344                 NULL},
 345         {"publickey",
 346                 userauth_pubkey,
 347                 NULL,
 348                 &options.pubkey_authentication,
 349                 NULL},
 350 #ifdef JPAKE
 351         {"jpake-01@openssh.com",
 352                 userauth_jpake,
 353                 userauth_jpake_cleanup,
 354                 &options.zero_knowledge_password_authentication,
 355                 &options.batch_mode},
 356 #endif
 357         {"keyboard-interactive",
 358                 userauth_kbdint,
 359                 NULL,
 360                 &options.kbd_interactive_authentication,
 361                 &options.batch_mode},
 362         {"password",
 363                 userauth_passwd,
 364                 NULL,
 365                 &options.password_authentication,
 366                 &options.batch_mode},
 367         {"none",
 368                 userauth_none,
 369                 NULL,
 370                 NULL,
 371                 NULL},
 372         {NULL, NULL, NULL, NULL, NULL}
 373 };
 374
 375 void
 376 ssh_userauth2(const char *local_user, const char *server_user, char *host,
 377     Sensitive *sensitive)
 378 {
 379         Authctxt authctxt;
 380         int type;
 381
 382         if (options.challenge_response_authentication)
 383                 options.kbd_interactive_authentication = 1;
 384
 385         packet_start(SSH2_MSG_SERVICE_REQUEST);
 386         packet_put_cstring("ssh-userauth");
 387         packet_send();
 388         debug("SSH2_MSG_SERVICE_REQUEST sent");
 389         packet_write_wait();
 390         type = packet_read();
 391         if (type != SSH2_MSG_SERVICE_ACCEPT)
 392                 fatal("Server denied authentication request: %d", type);
 393         if (packet_remaining() > 0) {
 394                 char *reply = packet_get_string(NULL);
 395                 debug2("service_accept: %s", reply);
 396                 xfree(reply);
 397         } else {
 398                 debug2("buggy server: service_accept w/o service");
 399         }
 400         packet_check_eom();
 401         debug("SSH2_MSG_SERVICE_ACCEPT received");
 402
 403         if (options.preferred_authentications == NULL)
 404                 options.preferred_authentications = authmethods_get();
 405
 406         /* setup authentication context */
 407         memset(&authctxt, 0, sizeof(authctxt));
 408         pubkey_prepare(&authctxt);
 409         authctxt.server_user = server_user;
 410         authctxt.local_user = local_user;
 411         authctxt.host = host;
 412         authctxt.service = "ssh-connection";            /* service name */
 413         authctxt.success = 0;
 414         authctxt.method = authmethod_lookup("none");
 415         authctxt.authlist = NULL;
 416         authctxt.methoddata = NULL;
 417         authctxt.sensitive = sensitive;
 418         authctxt.info_req_seen = 0;
 419         if (authctxt.method == NULL)
 420                 fatal("ssh_userauth2: internal error: cannot send userauth none request");
 421
 422         /* initial userauth request */
 423         userauth_none(&authctxt);
 424
 425         dispatch_init(&input_userauth_error);
 426         dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
 427         dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
 428         dispatch_set(SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
 429         dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt);     /* loop until success */
 430
 431         pubkey_cleanup(&authctxt);
 432         dispatch_range(SSH2_MSG_USERAUTH_MIN, SSH2_MSG_USERAUTH_MAX, NULL);
 433
 434 #ifdef  NONE_CIPHER_ENABLED
 435         /*
 436          * If the user explicitly requests to use the none cipher enable it
 437          * post authentication and only if the right conditions are met: both
 438          * of the NONE switches must be true and there must be no tty allocated.
 439          */
 440         if (options.none_switch == 1 && options.none_enabled == 1) {
 441                 if (!tty_flag) {
 442                         debug("Requesting none cipher re-keying...");
 443                         myproposal[PROPOSAL_ENC_ALGS_STOC] = "none";
 444                         myproposal[PROPOSAL_ENC_ALGS_CTOS] = "none";
 445                         kex_prop2buf(&xxx_kex->my, myproposal);
 446                         packet_request_rekeying();
 447                         fprintf(stderr, "WARNING: enabled NONE cipher\n");
 448                 } else {
 449                         /* Requested NONE cipher on an interactive session. */
 450                         debug("Cannot switch to NONE cipher with tty "
 451                             "allocated");
 452                         fprintf(stderr, "NONE cipher switch disabled given "
 453                             "a TTY is allocated\n");
 454                 }
 455         }
 456 #endif
 457         debug("Authentication succeeded (%s).", authctxt.method->name);
 458 }
 459
 460 void
 461 userauth(Authctxt *authctxt, char *authlist)
 462 {
 463         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 464                 authctxt->method->cleanup(authctxt);
 465
 466         if (authctxt->methoddata) {
 467                 xfree(authctxt->methoddata);
 468                 authctxt->methoddata = NULL;
 469         }
 470         if (authlist == NULL) {
 471                 authlist = authctxt->authlist;
 472         } else {
 473                 if (authctxt->authlist)
 474                         xfree(authctxt->authlist);
 475                 authctxt->authlist = authlist;
 476         }
 477         for (;;) {
 478                 Authmethod *method = authmethod_get(authlist);
 479                 if (method == NULL)
 480                         fatal("Permission denied (%s).", authlist);
 481                 authctxt->method = method;
 482
 483                 /* reset the per method handler */
 484                 dispatch_range(SSH2_MSG_USERAUTH_PER_METHOD_MIN,
 485                     SSH2_MSG_USERAUTH_PER_METHOD_MAX, NULL);
 486
 487                 /* and try new method */
 488                 if (method->userauth(authctxt) != 0) {
 489                         debug2("we sent a %s packet, wait for reply", method->name);
 490                         break;
 491                 } else {
 492                         debug2("we did not send a packet, disable method");
 493                         method->enabled = NULL;
 494                 }
 495         }
 496 }
 497
 498 /* ARGSUSED */
 499 void
 500 input_userauth_error(int type, u_int32_t seq, void *ctxt)
 501 {
 502         fatal("input_userauth_error: bad message during authentication: "
 503             "type %d", type);
 504 }
 505
 506 /* ARGSUSED */
 507 void
 508 input_userauth_banner(int type, u_int32_t seq, void *ctxt)
 509 {
 510         char *msg, *raw, *lang;
 511         u_int len;
 512
 513         debug3("input_userauth_banner");
 514         raw = packet_get_string(&len);
 515         lang = packet_get_string(NULL);
 516         if (len > 0 && options.log_level >= SYSLOG_LEVEL_INFO) {
 517                 if (len > 65536)
 518                         len = 65536;
 519                 msg = xmalloc(len * 4 + 1); /* max expansion from strnvis() */
 520                 strnvis(msg, raw, len * 4 + 1, VIS_SAFE|VIS_OCTAL|VIS_NOSLASH);
 521                 fprintf(stderr, "%s", msg);
 522                 xfree(msg);
 523         }
 524         xfree(raw);
 525         xfree(lang);
 526 }
 527
 528 /* ARGSUSED */
 529 void
 530 input_userauth_success(int type, u_int32_t seq, void *ctxt)
 531 {
 532         Authctxt *authctxt = ctxt;
 533
 534         if (authctxt == NULL)
 535                 fatal("input_userauth_success: no authentication context");
 536         if (authctxt->authlist) {
 537                 xfree(authctxt->authlist);
 538                 authctxt->authlist = NULL;
 539         }
 540         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 541                 authctxt->method->cleanup(authctxt);
 542         if (authctxt->methoddata) {
 543                 xfree(authctxt->methoddata);
 544                 authctxt->methoddata = NULL;
 545         }
 546         authctxt->success = 1;                  /* break out */
 547 }
 548
 549 void
 550 input_userauth_success_unexpected(int type, u_int32_t seq, void *ctxt)
 551 {
 552         Authctxt *authctxt = ctxt;
 553
 554         if (authctxt == NULL)
 555                 fatal("%s: no authentication context", __func__);
 556
 557         fatal("Unexpected authentication success during %s.",
 558             authctxt->method->name);
 559 }
 560
 561 /* ARGSUSED */
 562 void
 563 input_userauth_failure(int type, u_int32_t seq, void *ctxt)
 564 {
 565         Authctxt *authctxt = ctxt;
 566         char *authlist = NULL;
 567         int partial;
 568
 569         if (authctxt == NULL)
 570                 fatal("input_userauth_failure: no authentication context");
 571
 572         authlist = packet_get_string(NULL);
 573         partial = packet_get_char();
 574         packet_check_eom();
 575
 576         if (partial != 0)
 577                 logit("Authenticated with partial success.");
 578         debug("Authentications that can continue: %s", authlist);
 579
 580         userauth(authctxt, authlist);
 581 }
 582
 583 /* ARGSUSED */
 584 void
 585 input_userauth_pk_ok(int type, u_int32_t seq, void *ctxt)
 586 {
 587         Authctxt *authctxt = ctxt;
 588         Key *key = NULL;
 589         Identity *id = NULL;
 590         Buffer b;
 591         int pktype, sent = 0;
 592         u_int alen, blen;
 593         char *pkalg, *fp;
 594         u_char *pkblob;
 595
 596         if (authctxt == NULL)
 597                 fatal("input_userauth_pk_ok: no authentication context");
 598         if (datafellows & SSH_BUG_PKOK) {
 599                 /* this is similar to SSH_BUG_PKAUTH */
 600                 debug2("input_userauth_pk_ok: SSH_BUG_PKOK");
 601                 pkblob = packet_get_string(&blen);
 602                 buffer_init(&b);
 603                 buffer_append(&b, pkblob, blen);
 604                 pkalg = buffer_get_string(&b, &alen);
 605                 buffer_free(&b);
 606         } else {
 607                 pkalg = packet_get_string(&alen);
 608                 pkblob = packet_get_string(&blen);
 609         }
 610         packet_check_eom();
 611
 612         debug("Server accepts key: pkalg %s blen %u", pkalg, blen);
 613
 614         if ((pktype = key_type_from_name(pkalg)) == KEY_UNSPEC) {
 615                 debug("unknown pkalg %s", pkalg);
 616                 goto done;
 617         }
 618         if ((key = key_from_blob(pkblob, blen)) == NULL) {
 619                 debug("no key from blob. pkalg %s", pkalg);
 620                 goto done;
 621         }
 622         if (key->type != pktype) {
 623                 error("input_userauth_pk_ok: type mismatch "
 624                     "for decoded key (received %d, expected %d)",
 625                     key->type, pktype);
 626                 goto done;
 627         }
 628         fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
 629         debug2("input_userauth_pk_ok: fp %s", fp);
 630         xfree(fp);
 631
 632         /*
 633          * search keys in the reverse order, because last candidate has been
 634          * moved to the end of the queue.  this also avoids confusion by
 635          * duplicate keys
 636          */
 637         TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
 638                 if (key_equal(key, id->key)) {
 639                         sent = sign_and_send_pubkey(authctxt, id);
 640                         break;
 641                 }
 642         }
 643 done:
 644         if (key != NULL)
 645                 key_free(key);
 646         xfree(pkalg);
 647         xfree(pkblob);
 648
 649         /* try another method if we did not send a packet */
 650         if (sent == 0)
 651                 userauth(authctxt, NULL);
 652 }
 653
 654 #ifdef GSSAPI
 655 int
 656 userauth_gssapi(Authctxt *authctxt)
 657 {
 658         Gssctxt *gssctxt = NULL;
 659         static gss_OID_set gss_supported = NULL;
 660         static u_int mech = 0;
 661         OM_uint32 min;
 662         int ok = 0;
 663
 664         /* Try one GSSAPI method at a time, rather than sending them all at
 665          * once. */
 666
 667         if (gss_supported == NULL)
 668                 gss_indicate_mechs(&min, &gss_supported);
 669
 670         /* Check to see if the mechanism is usable before we offer it */
 671         while (mech < gss_supported->count && !ok) {
 672                 /* My DER encoding requires length<128 */
 673                 if (gss_supported->elements[mech].length < 128 &&
 674                     ssh_gssapi_check_mechanism(&gssctxt,
 675                     &gss_supported->elements[mech], authctxt->host)) {
 676                         ok = 1; /* Mechanism works */
 677                 } else {
 678                         mech++;
 679                 }
 680         }
 681
 682         if (!ok)
 683                 return 0;
 684
 685         authctxt->methoddata=(void *)gssctxt;
 686
 687         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 688         packet_put_cstring(authctxt->server_user);
 689         packet_put_cstring(authctxt->service);
 690         packet_put_cstring(authctxt->method->name);
 691
 692         packet_put_int(1);
 693
 694         packet_put_int((gss_supported->elements[mech].length) + 2);
 695         packet_put_char(SSH_GSS_OIDTYPE);
 696         packet_put_char(gss_supported->elements[mech].length);
 697         packet_put_raw(gss_supported->elements[mech].elements,
 698             gss_supported->elements[mech].length);
 699
 700         packet_send();
 701
 702         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
 703         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 704         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
 705         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 706
 707         mech++; /* Move along to next candidate */
 708
 709         return 1;
 710 }
 711
 712 static OM_uint32
 713 process_gssapi_token(void *ctxt, gss_buffer_t recv_tok)
 714 {
 715         Authctxt *authctxt = ctxt;
 716         Gssctxt *gssctxt = authctxt->methoddata;
 717         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 718         gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
 719         gss_buffer_desc gssbuf;
 720         OM_uint32 status, ms, flags;
 721         Buffer b;
 722
 723         status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 724             recv_tok, &send_tok, &flags);
 725
 726         if (send_tok.length > 0) {
 727                 if (GSS_ERROR(status))
 728                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 729                 else
 730                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 731
 732                 packet_put_string(send_tok.value, send_tok.length);
 733                 packet_send();
 734                 gss_release_buffer(&ms, &send_tok);
 735         }
 736
 737         if (status == GSS_S_COMPLETE) {
 738                 /* send either complete or MIC, depending on mechanism */
 739                 if (!(flags & GSS_C_INTEG_FLAG)) {
 740                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
 741                         packet_send();
 742                 } else {
 743                         ssh_gssapi_buildmic(&b, authctxt->server_user,
 744                             authctxt->service, "gssapi-with-mic");
 745
 746                         gssbuf.value = buffer_ptr(&b);
 747                         gssbuf.length = buffer_len(&b);
 748
 749                         status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);
 750
 751                         if (!GSS_ERROR(status)) {
 752                                 packet_start(SSH2_MSG_USERAUTH_GSSAPI_MIC);
 753                                 packet_put_string(mic.value, mic.length);
 754
 755                                 packet_send();
 756                         }
 757
 758                         buffer_free(&b);
 759                         gss_release_buffer(&ms, &mic);
 760                 }
 761         }
 762
 763         return status;
 764 }
 765
 766 /* ARGSUSED */
 767 void
 768 input_gssapi_response(int type, u_int32_t plen, void *ctxt)
 769 {
 770         Authctxt *authctxt = ctxt;
 771         Gssctxt *gssctxt;
 772         int oidlen;
 773         char *oidv;
 774
 775         if (authctxt == NULL)
 776                 fatal("input_gssapi_response: no authentication context");
 777         gssctxt = authctxt->methoddata;
 778
 779         /* Setup our OID */
 780         oidv = packet_get_string(&oidlen);
 781
 782         if (oidlen <= 2 ||
 783             oidv[0] != SSH_GSS_OIDTYPE ||
 784             oidv[1] != oidlen - 2) {
 785                 xfree(oidv);
 786                 debug("Badly encoded mechanism OID received");
 787                 userauth(authctxt, NULL);
 788                 return;
 789         }
 790
 791         if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
 792                 fatal("Server returned different OID than expected");
 793
 794         packet_check_eom();
 795
 796         xfree(oidv);
 797
 798         if (GSS_ERROR(process_gssapi_token(ctxt, GSS_C_NO_BUFFER))) {
 799                 /* Start again with next method on list */
 800                 debug("Trying to start again");
 801                 userauth(authctxt, NULL);
 802                 return;
 803         }
 804 }
 805
 806 /* ARGSUSED */
 807 void
 808 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 809 {
 810         Authctxt *authctxt = ctxt;
 811         gss_buffer_desc recv_tok;
 812         OM_uint32 status;
 813         u_int slen;
 814
 815         if (authctxt == NULL)
 816                 fatal("input_gssapi_response: no authentication context");
 817
 818         recv_tok.value = packet_get_string(&slen);
 819         recv_tok.length = slen; /* safe typecast */
 820
 821         packet_check_eom();
 822
 823         status = process_gssapi_token(ctxt, &recv_tok);
 824
 825         xfree(recv_tok.value);
 826
 827         if (GSS_ERROR(status)) {
 828                 /* Start again with the next method in the list */
 829                 userauth(authctxt, NULL);
 830                 return;
 831         }
 832 }
 833
 834 /* ARGSUSED */
 835 void
 836 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 837 {
 838         Authctxt *authctxt = ctxt;
 839         Gssctxt *gssctxt;
 840         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 841         gss_buffer_desc recv_tok;
 842         OM_uint32 status, ms;
 843         u_int len;
 844
 845         if (authctxt == NULL)
 846                 fatal("input_gssapi_response: no authentication context");
 847         gssctxt = authctxt->methoddata;
 848
 849         recv_tok.value = packet_get_string(&len);
 850         recv_tok.length = len;
 851
 852         packet_check_eom();
 853
 854         /* Stick it into GSSAPI and see what it says */
 855         status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 856             &recv_tok, &send_tok, NULL);
 857
 858         xfree(recv_tok.value);
 859         gss_release_buffer(&ms, &send_tok);
 860
 861         /* Server will be returning a failed packet after this one */
 862 }
 863
 864 /* ARGSUSED */
 865 void
 866 input_gssapi_error(int type, u_int32_t plen, void *ctxt)
 867 {
 868         OM_uint32 maj, min;
 869         char *msg;
 870         char *lang;
 871
 872         maj=packet_get_int();
 873         min=packet_get_int();
 874         msg=packet_get_string(NULL);
 875         lang=packet_get_string(NULL);
 876
 877         packet_check_eom();
 878
 879         debug("Server GSSAPI Error:\n%s", msg);
 880         xfree(msg);
 881         xfree(lang);
 882 }
 883 #endif /* GSSAPI */
 884
 885 int
 886 userauth_none(Authctxt *authctxt)
 887 {
 888         /* initial userauth request */
 889         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 890         packet_put_cstring(authctxt->server_user);
 891         packet_put_cstring(authctxt->service);
 892         packet_put_cstring(authctxt->method->name);
 893         packet_send();
 894         return 1;
 895 }
 896
 897 int
 898 userauth_passwd(Authctxt *authctxt)
 899 {
 900         static int attempt = 0;
 901         char prompt[150];
 902         char *password;
 903         const char *host = options.host_key_alias ?  options.host_key_alias :
 904             authctxt->host;
 905
 906         if (attempt++ >= options.number_of_password_prompts)
 907                 return 0;
 908
 909         if (attempt != 1)
 910                 error("Permission denied, please try again.");
 911
 912         snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
 913             authctxt->server_user, host);
 914         password = read_passphrase(prompt, 0);
 915         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 916         packet_put_cstring(authctxt->server_user);
 917         packet_put_cstring(authctxt->service);
 918         packet_put_cstring(authctxt->method->name);
 919         packet_put_char(0);
 920         packet_put_cstring(password);
 921         memset(password, 0, strlen(password));
 922         xfree(password);
 923         packet_add_padding(64);
 924         packet_send();
 925
 926         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 927             &input_userauth_passwd_changereq);
 928
 929         return 1;
 930 }
 931
 932 /*
 933  * parse PASSWD_CHANGEREQ, prompt user and send SSH2_MSG_USERAUTH_REQUEST
 934  */
 935 /* ARGSUSED */
 936 void
 937 input_userauth_passwd_changereq(int type, u_int32_t seqnr, void *ctxt)
 938 {
 939         Authctxt *authctxt = ctxt;
 940         char *info, *lang, *password = NULL, *retype = NULL;
 941         char prompt[150];
 942         const char *host = options.host_key_alias ? options.host_key_alias :
 943             authctxt->host;
 944
 945         debug2("input_userauth_passwd_changereq");
 946
 947         if (authctxt == NULL)
 948                 fatal("input_userauth_passwd_changereq: "
 949                     "no authentication context");
 950
 951         info = packet_get_string(NULL);
 952         lang = packet_get_string(NULL);
 953         if (strlen(info) > 0)
 954                 logit("%s", info);
 955         xfree(info);
 956         xfree(lang);
 957         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 958         packet_put_cstring(authctxt->server_user);
 959         packet_put_cstring(authctxt->service);
 960         packet_put_cstring(authctxt->method->name);
 961         packet_put_char(1);                     /* additional info */
 962         snprintf(prompt, sizeof(prompt),
 963             "Enter %.30s@%.128s's old password: ",
 964             authctxt->server_user, host);
 965         password = read_passphrase(prompt, 0);
 966         packet_put_cstring(password);
 967         memset(password, 0, strlen(password));
 968         xfree(password);
 969         password = NULL;
 970         while (password == NULL) {
 971                 snprintf(prompt, sizeof(prompt),
 972                     "Enter %.30s@%.128s's new password: ",
 973                     authctxt->server_user, host);
 974                 password = read_passphrase(prompt, RP_ALLOW_EOF);
 975                 if (password == NULL) {
 976                         /* bail out */
 977                         return;
 978                 }
 979                 snprintf(prompt, sizeof(prompt),
 980                     "Retype %.30s@%.128s's new password: ",
 981                     authctxt->server_user, host);
 982                 retype = read_passphrase(prompt, 0);
 983                 if (strcmp(password, retype) != 0) {
 984                         memset(password, 0, strlen(password));
 985                         xfree(password);
 986                         logit("Mismatch; try again, EOF to quit.");
 987                         password = NULL;
 988                 }
 989                 memset(retype, 0, strlen(retype));
 990                 xfree(retype);
 991         }
 992         packet_put_cstring(password);
 993         memset(password, 0, strlen(password));
 994         xfree(password);
 995         packet_add_padding(64);
 996         packet_send();
 997
 998         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 999             &input_userauth_passwd_changereq);
1000 }
1001
1002 #ifdef JPAKE
1003 static char *
1004 pw_encrypt(const char *password, const char *crypt_scheme, const char *salt)
1005 {
1006         /* OpenBSD crypt(3) handles all of these */
1007         if (strcmp(crypt_scheme, "crypt") == 0 ||
1008             strcmp(crypt_scheme, "bcrypt") == 0 ||
1009             strcmp(crypt_scheme, "md5crypt") == 0 ||
1010             strcmp(crypt_scheme, "crypt-extended") == 0)
1011                 return xstrdup(crypt(password, salt));
1012         error("%s: unsupported password encryption scheme \"%.100s\"",
1013             __func__, crypt_scheme);
1014         return NULL;
1015 }
1016
1017 static BIGNUM *
1018 jpake_password_to_secret(Authctxt *authctxt, const char *crypt_scheme,
1019     const char *salt)
1020 {
1021         char prompt[256], *password, *crypted;
1022         u_char *secret;
1023         u_int secret_len;
1024         BIGNUM *ret;
1025
1026         snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password (JPAKE): ",
1027             authctxt->server_user, authctxt->host);
1028         password = read_passphrase(prompt, 0);
1029
1030         if ((crypted = pw_encrypt(password, crypt_scheme, salt)) == NULL) {
1031                 logit("Disabling %s authentication", authctxt->method->name);
1032                 authctxt->method->enabled = NULL;
1033                 /* Continue with an empty password to fail gracefully */
1034                 crypted = xstrdup("");
1035         }
1036
1037 #ifdef JPAKE_DEBUG
1038         debug3("%s: salt = %s", __func__, salt);
1039         debug3("%s: scheme = %s", __func__, crypt_scheme);
1040         debug3("%s: crypted = %s", __func__, crypted);
1041 #endif
1042
1043         if (hash_buffer(crypted, strlen(crypted), EVP_sha256(),
1044             &secret, &secret_len) != 0)
1045                 fatal("%s: hash_buffer", __func__);
1046
1047         bzero(password, strlen(password));
1048         bzero(crypted, strlen(crypted));
1049         xfree(password);
1050         xfree(crypted);
1051
1052         if ((ret = BN_bin2bn(secret, secret_len, NULL)) == NULL)
1053                 fatal("%s: BN_bin2bn (secret)", __func__);
1054         bzero(secret, secret_len);
1055         xfree(secret);
1056
1057         return ret;
1058 }
1059
1060 /* ARGSUSED */
1061 void
1062 input_userauth_jpake_server_step1(int type, u_int32_t seq, void *ctxt)
1063 {
1064         Authctxt *authctxt = ctxt;
1065         struct jpake_ctx *pctx = authctxt->methoddata;
1066         u_char *x3_proof, *x4_proof, *x2_s_proof;
1067         u_int x3_proof_len, x4_proof_len, x2_s_proof_len;
1068         char *crypt_scheme, *salt;
1069
1070         /* Disable this message */
1071         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP1, NULL);
1072
1073         if ((pctx->g_x3 = BN_new()) == NULL ||
1074             (pctx->g_x4 = BN_new()) == NULL)
1075                 fatal("%s: BN_new", __func__);
1076
1077         /* Fetch step 1 values */
1078         crypt_scheme = packet_get_string(NULL);
1079         salt = packet_get_string(NULL);
1080         pctx->server_id = packet_get_string(&pctx->server_id_len);
1081         packet_get_bignum2(pctx->g_x3);
1082         packet_get_bignum2(pctx->g_x4);
1083         x3_proof = packet_get_string(&x3_proof_len);
1084         x4_proof = packet_get_string(&x4_proof_len);
1085         packet_check_eom();
1086
1087         JPAKE_DEBUG_CTX((pctx, "step 1 received in %s", __func__));
1088
1089         /* Obtain password and derive secret */
1090         pctx->s = jpake_password_to_secret(authctxt, crypt_scheme, salt);
1091         bzero(crypt_scheme, strlen(crypt_scheme));
1092         bzero(salt, strlen(salt));
1093         xfree(crypt_scheme);
1094         xfree(salt);
1095         JPAKE_DEBUG_BN((pctx->s, "%s: s = ", __func__));
1096
1097         /* Calculate step 2 values */
1098         jpake_step2(pctx->grp, pctx->s, pctx->g_x1,
1099             pctx->g_x3, pctx->g_x4, pctx->x2,
1100             pctx->server_id, pctx->server_id_len,
1101             pctx->client_id, pctx->client_id_len,
1102             x3_proof, x3_proof_len,
1103             x4_proof, x4_proof_len,
1104             &pctx->a,
1105             &x2_s_proof, &x2_s_proof_len);
1106
1107         bzero(x3_proof, x3_proof_len);
1108         bzero(x4_proof, x4_proof_len);
1109         xfree(x3_proof);
1110         xfree(x4_proof);
1111
1112         JPAKE_DEBUG_CTX((pctx, "step 2 sending in %s", __func__));
1113
1114         /* Send values for step 2 */
1115         packet_start(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2);
1116         packet_put_bignum2(pctx->a);
1117         packet_put_string(x2_s_proof, x2_s_proof_len);
1118         packet_send();
1119
1120         bzero(x2_s_proof, x2_s_proof_len);
1121         xfree(x2_s_proof);
1122
1123         /* Expect step 2 packet from peer */
1124         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP2,
1125             input_userauth_jpake_server_step2);
1126 }
1127
1128 /* ARGSUSED */
1129 void
1130 input_userauth_jpake_server_step2(int type, u_int32_t seq, void *ctxt)
1131 {
1132         Authctxt *authctxt = ctxt;
1133         struct jpake_ctx *pctx = authctxt->methoddata;
1134         u_char *x4_s_proof;
1135         u_int x4_s_proof_len;
1136
1137         /* Disable this message */
1138         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP2, NULL);
1139
1140         if ((pctx->b = BN_new()) == NULL)
1141                 fatal("%s: BN_new", __func__);
1142
1143         /* Fetch step 2 values */
1144         packet_get_bignum2(pctx->b);
1145         x4_s_proof = packet_get_string(&x4_s_proof_len);
1146         packet_check_eom();
1147
1148         JPAKE_DEBUG_CTX((pctx, "step 2 received in %s", __func__));
1149
1150         /* Derive shared key and calculate confirmation hash */
1151         jpake_key_confirm(pctx->grp, pctx->s, pctx->b,
1152             pctx->x2, pctx->g_x1, pctx->g_x2, pctx->g_x3, pctx->g_x4,
1153             pctx->client_id, pctx->client_id_len,
1154             pctx->server_id, pctx->server_id_len,
1155             session_id2, session_id2_len,
1156             x4_s_proof, x4_s_proof_len,
1157             &pctx->k,
1158             &pctx->h_k_cid_sessid, &pctx->h_k_cid_sessid_len);
1159
1160         bzero(x4_s_proof, x4_s_proof_len);
1161         xfree(x4_s_proof);
1162
1163         JPAKE_DEBUG_CTX((pctx, "confirm sending in %s", __func__));
1164
1165         /* Send key confirmation proof */
1166         packet_start(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM);
1167         packet_put_string(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
1168         packet_send();
1169
1170         /* Expect confirmation from peer */
1171         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_CONFIRM,
1172             input_userauth_jpake_server_confirm);
1173 }
1174
1175 /* ARGSUSED */
1176 void
1177 input_userauth_jpake_server_confirm(int type, u_int32_t seq, void *ctxt)
1178 {
1179         Authctxt *authctxt = ctxt;
1180         struct jpake_ctx *pctx = authctxt->methoddata;
1181
1182         /* Disable this message */
1183         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_CONFIRM, NULL);
1184
1185         pctx->h_k_sid_sessid = packet_get_string(&pctx->h_k_sid_sessid_len);
1186         packet_check_eom();
1187
1188         JPAKE_DEBUG_CTX((pctx, "confirm received in %s", __func__));
1189
1190         /* Verify expected confirmation hash */
1191         if (jpake_check_confirm(pctx->k,
1192             pctx->server_id, pctx->server_id_len,
1193             session_id2, session_id2_len,
1194             pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len) == 1)
1195                 debug("%s: %s success", __func__, authctxt->method->name);
1196         else {
1197                 debug("%s: confirmation mismatch", __func__);
1198                 /* XXX stash this so if auth succeeds then we can warn/kill */
1199         }
1200
1201         userauth_jpake_cleanup(authctxt);
1202 }
1203 #endif /* JPAKE */
1204
1205 static int
1206 identity_sign(Identity *id, u_char **sigp, u_int *lenp,
1207     u_char *data, u_int datalen)
1208 {
1209         Key *prv;
1210         int ret;
1211
1212         /* the agent supports this key */
1213         if (id->ac)
1214                 return (ssh_agent_sign(id->ac, id->key, sigp, lenp,
1215                     data, datalen));
1216         /*
1217          * we have already loaded the private key or
1218          * the private key is stored in external hardware
1219          */
1220         if (id->isprivate || (id->key->flags & KEY_FLAG_EXT))
1221                 return (key_sign(id->key, sigp, lenp, data, datalen));
1222         /* load the private key from the file */
1223         if ((prv = load_identity_file(id->filename)) == NULL)
1224                 return (-1);
1225         ret = key_sign(prv, sigp, lenp, data, datalen);
1226         key_free(prv);
1227         return (ret);
1228 }
1229
1230 static int
1231 sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
1232 {
1233         Buffer b;
1234         u_char *blob, *signature;
1235         u_int bloblen, slen;
1236         u_int skip = 0;
1237         int ret = -1;
1238         int have_sig = 1;
1239         char *fp;
1240
1241         fp = key_fingerprint(id->key, SSH_FP_MD5, SSH_FP_HEX);
1242         debug3("sign_and_send_pubkey: %s %s", key_type(id->key), fp);
1243         xfree(fp);
1244
1245         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1246                 /* we cannot handle this key */
1247                 debug3("sign_and_send_pubkey: cannot handle key");
1248                 return 0;
1249         }
1250         /* data to be signed */
1251         buffer_init(&b);
1252         if (datafellows & SSH_OLD_SESSIONID) {
1253                 buffer_append(&b, session_id2, session_id2_len);
1254                 skip = session_id2_len;
1255         } else {
1256                 buffer_put_string(&b, session_id2, session_id2_len);
1257                 skip = buffer_len(&b);
1258         }
1259         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1260         buffer_put_cstring(&b, authctxt->server_user);
1261         buffer_put_cstring(&b,
1262             datafellows & SSH_BUG_PKSERVICE ?
1263             "ssh-userauth" :
1264             authctxt->service);
1265         if (datafellows & SSH_BUG_PKAUTH) {
1266                 buffer_put_char(&b, have_sig);
1267         } else {
1268                 buffer_put_cstring(&b, authctxt->method->name);
1269                 buffer_put_char(&b, have_sig);
1270                 buffer_put_cstring(&b, key_ssh_name(id->key));
1271         }
1272         buffer_put_string(&b, blob, bloblen);
1273
1274         /* generate signature */
1275         ret = identity_sign(id, &signature, &slen,
1276             buffer_ptr(&b), buffer_len(&b));
1277         if (ret == -1) {
1278                 xfree(blob);
1279                 buffer_free(&b);
1280                 return 0;
1281         }
1282 #ifdef DEBUG_PK
1283         buffer_dump(&b);
1284 #endif
1285         if (datafellows & SSH_BUG_PKSERVICE) {
1286                 buffer_clear(&b);
1287                 buffer_append(&b, session_id2, session_id2_len);
1288                 skip = session_id2_len;
1289                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1290                 buffer_put_cstring(&b, authctxt->server_user);
1291                 buffer_put_cstring(&b, authctxt->service);
1292                 buffer_put_cstring(&b, authctxt->method->name);
1293                 buffer_put_char(&b, have_sig);
1294                 if (!(datafellows & SSH_BUG_PKAUTH))
1295                         buffer_put_cstring(&b, key_ssh_name(id->key));
1296                 buffer_put_string(&b, blob, bloblen);
1297         }
1298         xfree(blob);
1299
1300         /* append signature */
1301         buffer_put_string(&b, signature, slen);
1302         xfree(signature);
1303
1304         /* skip session id and packet type */
1305         if (buffer_len(&b) < skip + 1)
1306                 fatal("userauth_pubkey: internal error");
1307         buffer_consume(&b, skip + 1);
1308
1309         /* put remaining data from buffer into packet */
1310         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1311         packet_put_raw(buffer_ptr(&b), buffer_len(&b));
1312         buffer_free(&b);
1313         packet_send();
1314
1315         return 1;
1316 }
1317
1318 static int
1319 send_pubkey_test(Authctxt *authctxt, Identity *id)
1320 {
1321         u_char *blob;
1322         u_int bloblen, have_sig = 0;
1323
1324         debug3("send_pubkey_test");
1325
1326         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1327                 /* we cannot handle this key */
1328                 debug3("send_pubkey_test: cannot handle key");
1329                 return 0;
1330         }
1331         /* register callback for USERAUTH_PK_OK message */
1332         dispatch_set(SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
1333
1334         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1335         packet_put_cstring(authctxt->server_user);
1336         packet_put_cstring(authctxt->service);
1337         packet_put_cstring(authctxt->method->name);
1338         packet_put_char(have_sig);
1339         if (!(datafellows & SSH_BUG_PKAUTH))
1340                 packet_put_cstring(key_ssh_name(id->key));
1341         packet_put_string(blob, bloblen);
1342         xfree(blob);
1343         packet_send();
1344         return 1;
1345 }
1346
1347 static Key *
1348 load_identity_file(char *filename)
1349 {
1350         Key *private;
1351         char prompt[300], *passphrase;
1352         int perm_ok = 0, quit, i;
1353         struct stat st;
1354
1355         if (stat(filename, &st) < 0) {
1356                 debug3("no such identity: %s", filename);
1357                 return NULL;
1358         }
1359         private = key_load_private_type(KEY_UNSPEC, filename, "", NULL, &perm_ok);
1360         if (!perm_ok)
1361                 return NULL;
1362         if (private == NULL) {
1363                 if (options.batch_mode)
1364                         return NULL;
1365                 snprintf(prompt, sizeof prompt,
1366                     "Enter passphrase for key '%.100s': ", filename);
1367                 for (i = 0; i < options.number_of_password_prompts; i++) {
1368                         passphrase = read_passphrase(prompt, 0);
1369                         if (strcmp(passphrase, "") != 0) {
1370                                 private = key_load_private_type(KEY_UNSPEC,
1371                                     filename, passphrase, NULL, NULL);
1372                                 quit = 0;
1373                         } else {
1374                                 debug2("no passphrase given, try next key");
1375                                 quit = 1;
1376                         }
1377                         memset(passphrase, 0, strlen(passphrase));
1378                         xfree(passphrase);
1379                         if (private != NULL || quit)
1380                                 break;
1381                         debug2("bad passphrase given, try again...");
1382                 }
1383         }
1384         return private;
1385 }
1386
1387 /*
1388  * try keys in the following order:
1389  *      1. agent keys that are found in the config file
1390  *      2. other agent keys
1391  *      3. keys that are only listed in the config file
1392  */
1393 static void
1394 pubkey_prepare(Authctxt *authctxt)
1395 {
1396         Identity *id;
1397         Idlist agent, files, *preferred;
1398         Key *key;
1399         AuthenticationConnection *ac;
1400         char *comment;
1401         int i, found;
1402
1403         TAILQ_INIT(&agent);     /* keys from the agent */
1404         TAILQ_INIT(&files);     /* keys from the config file */
1405         preferred = &authctxt->keys;
1406         TAILQ_INIT(preferred);  /* preferred order of keys */
1407
1408         /* list of keys stored in the filesystem */
1409         for (i = 0; i < options.num_identity_files; i++) {
1410                 key = options.identity_keys[i];
1411                 if (key && key->type == KEY_RSA1)
1412                         continue;
1413                 if (key && key->cert && key->cert->type != SSH2_CERT_TYPE_USER)
1414                         continue;
1415                 options.identity_keys[i] = NULL;
1416                 id = xcalloc(1, sizeof(*id));
1417                 id->key = key;
1418                 id->filename = xstrdup(options.identity_files[i]);
1419                 TAILQ_INSERT_TAIL(&files, id, next);
1420         }
1421         /* list of keys supported by the agent */
1422         if ((ac = ssh_get_authentication_connection())) {
1423                 for (key = ssh_get_first_identity(ac, &comment, 2);
1424                     key != NULL;
1425                     key = ssh_get_next_identity(ac, &comment, 2)) {
1426                         found = 0;
1427                         TAILQ_FOREACH(id, &files, next) {
1428                                 /* agent keys from the config file are preferred */
1429                                 if (key_equal(key, id->key)) {
1430                                         key_free(key);
1431                                         xfree(comment);
1432                                         TAILQ_REMOVE(&files, id, next);
1433                                         TAILQ_INSERT_TAIL(preferred, id, next);
1434                                         id->ac = ac;
1435                                         found = 1;
1436                                         break;
1437                                 }
1438                         }
1439                         if (!found && !options.identities_only) {
1440                                 id = xcalloc(1, sizeof(*id));
1441                                 id->key = key;
1442                                 id->filename = comment;
1443                                 id->ac = ac;
1444                                 TAILQ_INSERT_TAIL(&agent, id, next);
1445                         }
1446                 }
1447                 /* append remaining agent keys */
1448                 for (id = TAILQ_FIRST(&agent); id; id = TAILQ_FIRST(&agent)) {
1449                         TAILQ_REMOVE(&agent, id, next);
1450                         TAILQ_INSERT_TAIL(preferred, id, next);
1451                 }
1452                 authctxt->agent = ac;
1453         }
1454         /* append remaining keys from the config file */
1455         for (id = TAILQ_FIRST(&files); id; id = TAILQ_FIRST(&files)) {
1456                 TAILQ_REMOVE(&files, id, next);
1457                 TAILQ_INSERT_TAIL(preferred, id, next);
1458         }
1459         TAILQ_FOREACH(id, preferred, next) {
1460                 debug2("key: %s (%p)", id->filename, id->key);
1461         }
1462 }
1463
1464 static void
1465 pubkey_cleanup(Authctxt *authctxt)
1466 {
1467         Identity *id;
1468
1469         if (authctxt->agent != NULL)
1470                 ssh_close_authentication_connection(authctxt->agent);
1471         for (id = TAILQ_FIRST(&authctxt->keys); id;
1472             id = TAILQ_FIRST(&authctxt->keys)) {
1473                 TAILQ_REMOVE(&authctxt->keys, id, next);
1474                 if (id->key)
1475                         key_free(id->key);
1476                 if (id->filename)
1477                         xfree(id->filename);
1478                 xfree(id);
1479         }
1480 }
1481
1482 int
1483 userauth_pubkey(Authctxt *authctxt)
1484 {
1485         Identity *id;
1486         int sent = 0;
1487
1488         while ((id = TAILQ_FIRST(&authctxt->keys))) {
1489                 if (id->tried++)
1490                         return (0);
1491                 /* move key to the end of the queue */
1492                 TAILQ_REMOVE(&authctxt->keys, id, next);
1493                 TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
1494                 /*
1495                  * send a test message if we have the public key. for
1496                  * encrypted keys we cannot do this and have to load the
1497                  * private key instead
1498                  */
1499                 if (id->key && id->key->type != KEY_RSA1) {
1500                         debug("Offering %s public key: %s", key_type(id->key),
1501                             id->filename);
1502                         sent = send_pubkey_test(authctxt, id);
1503                 } else if (id->key == NULL) {
1504                         debug("Trying private key: %s", id->filename);
1505                         id->key = load_identity_file(id->filename);
1506                         if (id->key != NULL) {
1507                                 id->isprivate = 1;
1508                                 sent = sign_and_send_pubkey(authctxt, id);
1509                                 key_free(id->key);
1510                                 id->key = NULL;
1511                         }
1512                 }
1513                 if (sent)
1514                         return (sent);
1515         }
1516         return (0);
1517 }
1518
1519 /*
1520  * Send userauth request message specifying keyboard-interactive method.
1521  */
1522 int
1523 userauth_kbdint(Authctxt *authctxt)
1524 {
1525         static int attempt = 0;
1526
1527         if (attempt++ >= options.number_of_password_prompts)
1528                 return 0;
1529         /* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
1530         if (attempt > 1 && !authctxt->info_req_seen) {
1531                 debug3("userauth_kbdint: disable: no info_req_seen");
1532                 dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
1533                 return 0;
1534         }
1535
1536         debug2("userauth_kbdint");
1537         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1538         packet_put_cstring(authctxt->server_user);
1539         packet_put_cstring(authctxt->service);
1540         packet_put_cstring(authctxt->method->name);
1541         packet_put_cstring("");                                 /* lang */
1542         packet_put_cstring(options.kbd_interactive_devices ?
1543             options.kbd_interactive_devices : "");
1544         packet_send();
1545
1546         dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
1547         return 1;
1548 }
1549
1550 /*
1551  * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
1552  */
1553 void
1554 input_userauth_info_req(int type, u_int32_t seq, void *ctxt)
1555 {
1556         Authctxt *authctxt = ctxt;
1557         char *name, *inst, *lang, *prompt, *response;
1558         u_int num_prompts, i;
1559         int echo = 0;
1560
1561         debug2("input_userauth_info_req");
1562
1563         if (authctxt == NULL)
1564                 fatal("input_userauth_info_req: no authentication context");
1565
1566         authctxt->info_req_seen = 1;
1567
1568         name = packet_get_string(NULL);
1569         inst = packet_get_string(NULL);
1570         lang = packet_get_string(NULL);
1571         if (strlen(name) > 0)
1572                 logit("%s", name);
1573         if (strlen(inst) > 0)
1574                 logit("%s", inst);
1575         xfree(name);
1576         xfree(inst);
1577         xfree(lang);
1578
1579         num_prompts = packet_get_int();
1580         /*
1581          * Begin to build info response packet based on prompts requested.
1582          * We commit to providing the correct number of responses, so if
1583          * further on we run into a problem that prevents this, we have to
1584          * be sure and clean this up and send a correct error response.
1585          */
1586         packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
1587         packet_put_int(num_prompts);
1588
1589         debug2("input_userauth_info_req: num_prompts %d", num_prompts);
1590         for (i = 0; i < num_prompts; i++) {
1591                 prompt = packet_get_string(NULL);
1592                 echo = packet_get_char();
1593
1594                 response = read_passphrase(prompt, echo ? RP_ECHO : 0);
1595
1596                 packet_put_cstring(response);
1597                 memset(response, 0, strlen(response));
1598                 xfree(response);
1599                 xfree(prompt);
1600         }
1601         packet_check_eom(); /* done with parsing incoming message. */
1602
1603         packet_add_padding(64);
1604         packet_send();
1605 }
1606
1607 static int
1608 ssh_keysign(Key *key, u_char **sigp, u_int *lenp,
1609     u_char *data, u_int datalen)
1610 {
1611         Buffer b;
1612         struct stat st;
1613         pid_t pid;
1614         int to[2], from[2], status, version = 2;
1615
1616         debug2("ssh_keysign called");
1617
1618         if (stat(_PATH_SSH_KEY_SIGN, &st) < 0) {
1619                 error("ssh_keysign: not installed: %s", strerror(errno));
1620                 return -1;
1621         }
1622         if (fflush(stdout) != 0)
1623                 error("ssh_keysign: fflush: %s", strerror(errno));
1624         if (pipe(to) < 0) {
1625                 error("ssh_keysign: pipe: %s", strerror(errno));
1626                 return -1;
1627         }
1628         if (pipe(from) < 0) {
1629                 error("ssh_keysign: pipe: %s", strerror(errno));
1630                 return -1;
1631         }
1632         if ((pid = fork()) < 0) {
1633                 error("ssh_keysign: fork: %s", strerror(errno));
1634                 return -1;
1635         }
1636         if (pid == 0) {
1637                 /* keep the socket on exec */
1638                 fcntl(packet_get_connection_in(), F_SETFD, 0);
1639                 permanently_drop_suid(getuid());
1640                 close(from[0]);
1641                 if (dup2(from[1], STDOUT_FILENO) < 0)
1642                         fatal("ssh_keysign: dup2: %s", strerror(errno));
1643                 close(to[1]);
1644                 if (dup2(to[0], STDIN_FILENO) < 0)
1645                         fatal("ssh_keysign: dup2: %s", strerror(errno));
1646                 close(from[1]);
1647                 close(to[0]);
1648                 execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *) 0);
1649                 fatal("ssh_keysign: exec(%s): %s", _PATH_SSH_KEY_SIGN,
1650                     strerror(errno));
1651         }
1652         close(from[1]);
1653         close(to[0]);
1654
1655         buffer_init(&b);
1656         buffer_put_int(&b, packet_get_connection_in()); /* send # of socket */
1657         buffer_put_string(&b, data, datalen);
1658         if (ssh_msg_send(to[1], version, &b) == -1)
1659                 fatal("ssh_keysign: couldn't send request");
1660
1661         if (ssh_msg_recv(from[0], &b) < 0) {
1662                 error("ssh_keysign: no reply");
1663                 buffer_free(&b);
1664                 return -1;
1665         }
1666         close(from[0]);
1667         close(to[1]);
1668
1669         while (waitpid(pid, &status, 0) < 0)
1670                 if (errno != EINTR)
1671                         break;
1672
1673         if (buffer_get_char(&b) != version) {
1674                 error("ssh_keysign: bad version");
1675                 buffer_free(&b);
1676                 return -1;
1677         }
1678         *sigp = buffer_get_string(&b, lenp);
1679         buffer_free(&b);
1680
1681         return 0;
1682 }
1683
1684 int
1685 userauth_hostbased(Authctxt *authctxt)
1686 {
1687         Key *private = NULL;
1688         Sensitive *sensitive = authctxt->sensitive;
1689         Buffer b;
1690         u_char *signature, *blob;
1691         char *chost, *pkalg, *p;
1692         const char *service;
1693         u_int blen, slen;
1694         int ok, i, found = 0;
1695
1696         /* check for a useful key */
1697         for (i = 0; i < sensitive->nkeys; i++) {
1698                 private = sensitive->keys[i];
1699                 if (private && private->type != KEY_RSA1) {
1700                         found = 1;
1701                         /* we take and free the key */
1702                         sensitive->keys[i] = NULL;
1703                         break;
1704                 }
1705         }
1706         if (!found) {
1707                 debug("No more client hostkeys for hostbased authentication.");
1708                 return 0;
1709         }
1710         if (key_to_blob(private, &blob, &blen) == 0) {
1711                 key_free(private);
1712                 return 0;
1713         }
1714         /* figure out a name for the client host */
1715         p = get_local_name(packet_get_connection_in());
1716         if (p == NULL) {
1717                 error("userauth_hostbased: cannot get local ipaddr/name");
1718                 key_free(private);
1719                 xfree(blob);
1720                 return 0;
1721         }
1722         xasprintf(&chost, "%s.", p);
1723         debug2("userauth_hostbased: chost %s", chost);
1724         xfree(p);
1725
1726         service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
1727             authctxt->service;
1728         pkalg = xstrdup(key_ssh_name(private));
1729         buffer_init(&b);
1730         /* construct data */
1731         buffer_put_string(&b, session_id2, session_id2_len);
1732         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1733         buffer_put_cstring(&b, authctxt->server_user);
1734         buffer_put_cstring(&b, service);
1735         buffer_put_cstring(&b, authctxt->method->name);
1736         buffer_put_cstring(&b, pkalg);
1737         buffer_put_string(&b, blob, blen);
1738         buffer_put_cstring(&b, chost);
1739         buffer_put_cstring(&b, authctxt->local_user);
1740 #ifdef DEBUG_PK
1741         buffer_dump(&b);
1742 #endif
1743         if (sensitive->external_keysign)
1744                 ok = ssh_keysign(private, &signature, &slen,
1745                     buffer_ptr(&b), buffer_len(&b));
1746         else
1747                 ok = key_sign(private, &signature, &slen,
1748                     buffer_ptr(&b), buffer_len(&b));
1749         key_free(private);
1750         buffer_free(&b);
1751         if (ok != 0) {
1752                 error("key_sign failed");
1753                 xfree(chost);
1754                 xfree(pkalg);
1755                 xfree(blob);
1756                 return 0;
1757         }
1758         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1759         packet_put_cstring(authctxt->server_user);
1760         packet_put_cstring(authctxt->service);
1761         packet_put_cstring(authctxt->method->name);
1762         packet_put_cstring(pkalg);
1763         packet_put_string(blob, blen);
1764         packet_put_cstring(chost);
1765         packet_put_cstring(authctxt->local_user);
1766         packet_put_string(signature, slen);
1767         memset(signature, 's', slen);
1768         xfree(signature);
1769         xfree(chost);
1770         xfree(pkalg);
1771         xfree(blob);
1772
1773         packet_send();
1774         return 1;
1775 }
1776
1777 #ifdef JPAKE
1778 int
1779 userauth_jpake(Authctxt *authctxt)
1780 {
1781         struct jpake_ctx *pctx;
1782         u_char *x1_proof, *x2_proof;
1783         u_int x1_proof_len, x2_proof_len;
1784         static int attempt = 0; /* XXX share with userauth_password's? */
1785
1786         if (attempt++ >= options.number_of_password_prompts)
1787                 return 0;
1788         if (attempt != 1)
1789                 error("Permission denied, please try again.");
1790
1791         if (authctxt->methoddata != NULL)
1792                 fatal("%s: authctxt->methoddata already set (%p)",
1793                     __func__, authctxt->methoddata);
1794
1795         authctxt->methoddata = pctx = jpake_new();
1796
1797         /*
1798          * Send request immediately, to get the protocol going while
1799          * we do the initial computations.
1800          */
1801         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1802         packet_put_cstring(authctxt->server_user);
1803         packet_put_cstring(authctxt->service);
1804         packet_put_cstring(authctxt->method->name);
1805         packet_send();
1806         packet_write_wait();
1807
1808         jpake_step1(pctx->grp,
1809             &pctx->client_id, &pctx->client_id_len,
1810             &pctx->x1, &pctx->x2, &pctx->g_x1, &pctx->g_x2,
1811             &x1_proof, &x1_proof_len,
1812             &x2_proof, &x2_proof_len);
1813
1814         JPAKE_DEBUG_CTX((pctx, "step 1 sending in %s", __func__));
1815
1816         packet_start(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1);
1817         packet_put_string(pctx->client_id, pctx->client_id_len);
1818         packet_put_bignum2(pctx->g_x1);
1819         packet_put_bignum2(pctx->g_x2);
1820         packet_put_string(x1_proof, x1_proof_len);
1821         packet_put_string(x2_proof, x2_proof_len);
1822         packet_send();
1823
1824         bzero(x1_proof, x1_proof_len);
1825         bzero(x2_proof, x2_proof_len);
1826         xfree(x1_proof);
1827         xfree(x2_proof);
1828
1829         /* Expect step 1 packet from peer */
1830         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP1,
1831             input_userauth_jpake_server_step1);
1832         dispatch_set(SSH2_MSG_USERAUTH_SUCCESS,
1833             &input_userauth_success_unexpected);
1834
1835         return 1;
1836 }
1837
1838 void
1839 userauth_jpake_cleanup(Authctxt *authctxt)
1840 {
1841         debug3("%s: clean up", __func__);
1842         if (authctxt->methoddata != NULL) {
1843                 jpake_free(authctxt->methoddata);
1844                 authctxt->methoddata = NULL;
1845         }
1846         dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
1847 }
1848 #endif /* JPAKE */
1849
1850 /* find auth method */
1851
1852 /*
1853  * given auth method name, if configurable options permit this method fill
1854  * in auth_ident field and return true, otherwise return false.
1855  */
1856 static int
1857 authmethod_is_enabled(Authmethod *method)
1858 {
1859         if (method == NULL)
1860                 return 0;
1861         /* return false if options indicate this method is disabled */
1862         if  (method->enabled == NULL || *method->enabled == 0)
1863                 return 0;
1864         /* return false if batch mode is enabled but method needs interactive mode */
1865         if  (method->batch_flag != NULL && *method->batch_flag != 0)
1866                 return 0;
1867         return 1;
1868 }
1869
1870 static Authmethod *
1871 authmethod_lookup(const char *name)
1872 {
1873         Authmethod *method = NULL;
1874         if (name != NULL)
1875                 for (method = authmethods; method->name != NULL; method++)
1876                         if (strcmp(name, method->name) == 0)
1877                                 return method;
1878         debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
1879         return NULL;
1880 }
1881
1882 /* XXX internal state */
1883 static Authmethod *current = NULL;
1884 static char *supported = NULL;
1885 static char *preferred = NULL;
1886
1887 /*
1888  * Given the authentication method list sent by the server, return the
1889  * next method we should try.  If the server initially sends a nil list,
1890  * use a built-in default list.
1891  */
1892 static Authmethod *
1893 authmethod_get(char *authlist)
1894 {
1895         char *name = NULL;
1896         u_int next;
1897
1898         /* Use a suitable default if we're passed a nil list.  */
1899         if (authlist == NULL || strlen(authlist) == 0)
1900                 authlist = options.preferred_authentications;
1901
1902         if (supported == NULL || strcmp(authlist, supported) != 0) {
1903                 debug3("start over, passed a different list %s", authlist);
1904                 if (supported != NULL)
1905                         xfree(supported);
1906                 supported = xstrdup(authlist);
1907                 preferred = options.preferred_authentications;
1908                 debug3("preferred %s", preferred);
1909                 current = NULL;
1910         } else if (current != NULL && authmethod_is_enabled(current))
1911                 return current;
1912
1913         for (;;) {
1914                 if ((name = match_list(preferred, supported, &next)) == NULL) {
1915                         debug("No more authentication methods to try.");
1916                         current = NULL;
1917                         return NULL;
1918                 }
1919                 preferred += next;
1920                 debug3("authmethod_lookup %s", name);
1921                 debug3("remaining preferred: %s", preferred);
1922                 if ((current = authmethod_lookup(name)) != NULL &&
1923                     authmethod_is_enabled(current)) {
1924                         debug3("authmethod_is_enabled %s", name);
1925                         debug("Next authentication method: %s", name);
1926                         xfree(name);
1927                         return current;
1928                 }
1929         }
1930 }
1931
1932 static char *
1933 authmethods_get(void)
1934 {
1935         Authmethod *method = NULL;
1936         Buffer b;
1937         char *list;
1938
1939         buffer_init(&b);
1940         for (method = authmethods; method->name != NULL; method++) {
1941                 if (authmethod_is_enabled(method)) {
1942                         if (buffer_len(&b) > 0)
1943                                 buffer_append(&b, ",", 1);
1944                         buffer_append(&b, method->name, strlen(method->name));
1945                 }
1946         }
1947         buffer_append(&b, "\0", 1);
1948         list = xstrdup(buffer_ptr(&b));
1949         buffer_free(&b);
1950         return list;
1951 }
1952