crypto/openssh/sshconnect2.c

   1 /* $OpenBSD: sshconnect2.c,v 1.186 2010/11/29 23:45:51 djm 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
 124         /* Find all hostkeys for this hostname */
 125         get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
 126         hostkeys = init_hostkeys();
 127         load_hostkeys(hostkeys, hostname, options.user_hostfile2);
 128         load_hostkeys(hostkeys, hostname, options.system_hostfile2);
 129         load_hostkeys(hostkeys, hostname, options.user_hostfile);
 130         load_hostkeys(hostkeys, hostname, options.system_hostfile);
 131
 132         oavail = avail = xstrdup(KEX_DEFAULT_PK_ALG);
 133         maxlen = strlen(avail) + 1;
 134         first = xmalloc(maxlen);
 135         last = xmalloc(maxlen);
 136         *first = *last = '\0';
 137
 138 #define ALG_APPEND(to, from) \
 139         do { \
 140                 if (*to != '\0') \
 141                         strlcat(to, ",", maxlen); \
 142                 strlcat(to, from, maxlen); \
 143         } while (0)
 144
 145         while ((alg = strsep(&avail, ",")) && *alg != '\0') {
 146                 if ((ktype = key_type_from_name(alg)) == KEY_UNSPEC)
 147                         fatal("%s: unknown alg %s", __func__, alg);
 148                 if (lookup_key_in_hostkeys_by_type(hostkeys,
 149                     key_type_plain(ktype), NULL))
 150                         ALG_APPEND(first, alg);
 151                 else
 152                         ALG_APPEND(last, alg);
 153         }
 154 #undef ALG_APPEND
 155         xasprintf(&ret, "%s%s%s", first, *first == '\0' ? "" : ",", last);
 156         if (*first != '\0')
 157                 debug3("%s: prefer hostkeyalgs: %s", __func__, first);
 158
 159         xfree(first);
 160         xfree(last);
 161         xfree(hostname);
 162         xfree(oavail);
 163         free_hostkeys(hostkeys);
 164
 165         return ret;
 166 }
 167
 168 void
 169 ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 170 {
 171         Kex *kex;
 172
 173         xxx_host = host;
 174         xxx_hostaddr = hostaddr;
 175
 176         if (options.ciphers == (char *)-1) {
 177                 logit("No valid ciphers for protocol version 2 given, using defaults.");
 178                 options.ciphers = NULL;
 179         }
 180         if (options.ciphers != NULL) {
 181                 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 182                 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
 183         }
 184         myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 185             compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
 186         myproposal[PROPOSAL_ENC_ALGS_STOC] =
 187             compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
 188         if (options.compression) {
 189                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 190                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib@openssh.com,zlib,none";
 191         } else {
 192                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 193                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com,zlib";
 194         }
 195         if (options.macs != NULL) {
 196                 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
 197                 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
 198         }
 199         if (options.hostkeyalgorithms != NULL)
 200                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 201                     options.hostkeyalgorithms;
 202         else {
 203                 /* Prefer algorithms that we already have keys for */
 204                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 205                     order_hostkeyalgs(host, hostaddr, port);
 206         }
 207         if (options.kex_algorithms != NULL)
 208                 myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms;
 209
 210         if (options.rekey_limit)
 211                 packet_set_rekey_limit((u_int32_t)options.rekey_limit);
 212
 213         /* start key exchange */
 214         kex = kex_setup(myproposal);
 215         kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 216         kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
 217         kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
 218         kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 219         kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
 220         kex->client_version_string=client_version_string;
 221         kex->server_version_string=server_version_string;
 222         kex->verify_host_key=&verify_host_key_callback;
 223
 224         xxx_kex = kex;
 225
 226         dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
 227
 228         if (options.use_roaming && !kex->roaming) {
 229                 debug("Roaming not allowed by server");
 230                 options.use_roaming = 0;
 231         }
 232
 233         session_id2 = kex->session_id;
 234         session_id2_len = kex->session_id_len;
 235
 236 #ifdef DEBUG_KEXDH
 237         /* send 1st encrypted/maced/compressed message */
 238         packet_start(SSH2_MSG_IGNORE);
 239         packet_put_cstring("markus");
 240         packet_send();
 241         packet_write_wait();
 242 #endif
 243 }
 244
 245 /*
 246  * Authenticate user
 247  */
 248
 249 typedef struct Authctxt Authctxt;
 250 typedef struct Authmethod Authmethod;
 251 typedef struct identity Identity;
 252 typedef struct idlist Idlist;
 253
 254 struct identity {
 255         TAILQ_ENTRY(identity) next;
 256         AuthenticationConnection *ac;   /* set if agent supports key */
 257         Key     *key;                   /* public/private key */
 258         char    *filename;              /* comment for agent-only keys */
 259         int     tried;
 260         int     isprivate;              /* key points to the private key */
 261 };
 262 TAILQ_HEAD(idlist, identity);
 263
 264 struct Authctxt {
 265         const char *server_user;
 266         const char *local_user;
 267         const char *host;
 268         const char *service;
 269         Authmethod *method;
 270         sig_atomic_t success;
 271         char *authlist;
 272         /* pubkey */
 273         Idlist keys;
 274         AuthenticationConnection *agent;
 275         /* hostbased */
 276         Sensitive *sensitive;
 277         /* kbd-interactive */
 278         int info_req_seen;
 279         /* generic */
 280         void *methoddata;
 281 };
 282 struct Authmethod {
 283         char    *name;          /* string to compare against server's list */
 284         int     (*userauth)(Authctxt *authctxt);
 285         void    (*cleanup)(Authctxt *authctxt);
 286         int     *enabled;       /* flag in option struct that enables method */
 287         int     *batch_flag;    /* flag in option struct that disables method */
 288 };
 289
 290 void    input_userauth_success(int, u_int32_t, void *);
 291 void    input_userauth_success_unexpected(int, u_int32_t, void *);
 292 void    input_userauth_failure(int, u_int32_t, void *);
 293 void    input_userauth_banner(int, u_int32_t, void *);
 294 void    input_userauth_error(int, u_int32_t, void *);
 295 void    input_userauth_info_req(int, u_int32_t, void *);
 296 void    input_userauth_pk_ok(int, u_int32_t, void *);
 297 void    input_userauth_passwd_changereq(int, u_int32_t, void *);
 298 void    input_userauth_jpake_server_step1(int, u_int32_t, void *);
 299 void    input_userauth_jpake_server_step2(int, u_int32_t, void *);
 300 void    input_userauth_jpake_server_confirm(int, u_int32_t, void *);
 301
 302 int     userauth_none(Authctxt *);
 303 int     userauth_pubkey(Authctxt *);
 304 int     userauth_passwd(Authctxt *);
 305 int     userauth_kbdint(Authctxt *);
 306 int     userauth_hostbased(Authctxt *);
 307 int     userauth_jpake(Authctxt *);
 308
 309 void    userauth_jpake_cleanup(Authctxt *);
 310
 311 #ifdef GSSAPI
 312 int     userauth_gssapi(Authctxt *authctxt);
 313 void    input_gssapi_response(int type, u_int32_t, void *);
 314 void    input_gssapi_token(int type, u_int32_t, void *);
 315 void    input_gssapi_hash(int type, u_int32_t, void *);
 316 void    input_gssapi_error(int, u_int32_t, void *);
 317 void    input_gssapi_errtok(int, u_int32_t, void *);
 318 #endif
 319
 320 void    userauth(Authctxt *, char *);
 321
 322 static int sign_and_send_pubkey(Authctxt *, Identity *);
 323 static void pubkey_prepare(Authctxt *);
 324 static void pubkey_cleanup(Authctxt *);
 325 static Key *load_identity_file(char *);
 326
 327 static Authmethod *authmethod_get(char *authlist);
 328 static Authmethod *authmethod_lookup(const char *name);
 329 static char *authmethods_get(void);
 330
 331 Authmethod authmethods[] = {
 332 #ifdef GSSAPI
 333         {"gssapi-with-mic",
 334                 userauth_gssapi,
 335                 NULL,
 336                 &options.gss_authentication,
 337                 NULL},
 338 #endif
 339         {"hostbased",
 340                 userauth_hostbased,
 341                 NULL,
 342                 &options.hostbased_authentication,
 343                 NULL},
 344         {"publickey",
 345                 userauth_pubkey,
 346                 NULL,
 347                 &options.pubkey_authentication,
 348                 NULL},
 349 #ifdef JPAKE
 350         {"jpake-01@openssh.com",
 351                 userauth_jpake,
 352                 userauth_jpake_cleanup,
 353                 &options.zero_knowledge_password_authentication,
 354                 &options.batch_mode},
 355 #endif
 356         {"keyboard-interactive",
 357                 userauth_kbdint,
 358                 NULL,
 359                 &options.kbd_interactive_authentication,
 360                 &options.batch_mode},
 361         {"password",
 362                 userauth_passwd,
 363                 NULL,
 364                 &options.password_authentication,
 365                 &options.batch_mode},
 366         {"none",
 367                 userauth_none,
 368                 NULL,
 369                 NULL,
 370                 NULL},
 371         {NULL, NULL, NULL, NULL, NULL}
 372 };
 373
 374 void
 375 ssh_userauth2(const char *local_user, const char *server_user, char *host,
 376     Sensitive *sensitive)
 377 {
 378         Authctxt authctxt;
 379         int type;
 380
 381         if (options.challenge_response_authentication)
 382                 options.kbd_interactive_authentication = 1;
 383
 384         packet_start(SSH2_MSG_SERVICE_REQUEST);
 385         packet_put_cstring("ssh-userauth");
 386         packet_send();
 387         debug("SSH2_MSG_SERVICE_REQUEST sent");
 388         packet_write_wait();
 389         type = packet_read();
 390         if (type != SSH2_MSG_SERVICE_ACCEPT)
 391                 fatal("Server denied authentication request: %d", type);
 392         if (packet_remaining() > 0) {
 393                 char *reply = packet_get_string(NULL);
 394                 debug2("service_accept: %s", reply);
 395                 xfree(reply);
 396         } else {
 397                 debug2("buggy server: service_accept w/o service");
 398         }
 399         packet_check_eom();
 400         debug("SSH2_MSG_SERVICE_ACCEPT received");
 401
 402         if (options.preferred_authentications == NULL)
 403                 options.preferred_authentications = authmethods_get();
 404
 405         /* setup authentication context */
 406         memset(&authctxt, 0, sizeof(authctxt));
 407         pubkey_prepare(&authctxt);
 408         authctxt.server_user = server_user;
 409         authctxt.local_user = local_user;
 410         authctxt.host = host;
 411         authctxt.service = "ssh-connection";            /* service name */
 412         authctxt.success = 0;
 413         authctxt.method = authmethod_lookup("none");
 414         authctxt.authlist = NULL;
 415         authctxt.methoddata = NULL;
 416         authctxt.sensitive = sensitive;
 417         authctxt.info_req_seen = 0;
 418         if (authctxt.method == NULL)
 419                 fatal("ssh_userauth2: internal error: cannot send userauth none request");
 420
 421         /* initial userauth request */
 422         userauth_none(&authctxt);
 423
 424         dispatch_init(&input_userauth_error);
 425         dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
 426         dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
 427         dispatch_set(SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
 428         dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt);     /* loop until success */
 429
 430         pubkey_cleanup(&authctxt);
 431         dispatch_range(SSH2_MSG_USERAUTH_MIN, SSH2_MSG_USERAUTH_MAX, NULL);
 432
 433 #ifdef  NONE_CIPHER_ENABLED
 434         /*
 435          * If the user explicitly requests to use the none cipher enable it
 436          * post authentication and only if the right conditions are met: both
 437          * of the NONE switches must be true and there must be no tty allocated.
 438          */
 439         if (options.none_switch == 1 && options.none_enabled == 1) {
 440                 if (!tty_flag) {
 441                         debug("Requesting none cipher re-keying...");
 442                         myproposal[PROPOSAL_ENC_ALGS_STOC] = "none";
 443                         myproposal[PROPOSAL_ENC_ALGS_CTOS] = "none";
 444                         kex_prop2buf(&xxx_kex->my, myproposal);
 445                         packet_request_rekeying();
 446                         fprintf(stderr, "WARNING: enabled NONE cipher\n");
 447                 } else {
 448                         /* Requested NONE cipher on an interactive session. */
 449                         debug("Cannot switch to NONE cipher with tty "
 450                             "allocated");
 451                         fprintf(stderr, "NONE cipher switch disabled given "
 452                             "a TTY is allocated\n");
 453                 }
 454         }
 455 #endif
 456         debug("Authentication succeeded (%s).", authctxt.method->name);
 457 }
 458
 459 void
 460 userauth(Authctxt *authctxt, char *authlist)
 461 {
 462         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 463                 authctxt->method->cleanup(authctxt);
 464
 465         if (authctxt->methoddata) {
 466                 xfree(authctxt->methoddata);
 467                 authctxt->methoddata = NULL;
 468         }
 469         if (authlist == NULL) {
 470                 authlist = authctxt->authlist;
 471         } else {
 472                 if (authctxt->authlist)
 473                         xfree(authctxt->authlist);
 474                 authctxt->authlist = authlist;
 475         }
 476         for (;;) {
 477                 Authmethod *method = authmethod_get(authlist);
 478                 if (method == NULL)
 479                         fatal("Permission denied (%s).", authlist);
 480                 authctxt->method = method;
 481
 482                 /* reset the per method handler */
 483                 dispatch_range(SSH2_MSG_USERAUTH_PER_METHOD_MIN,
 484                     SSH2_MSG_USERAUTH_PER_METHOD_MAX, NULL);
 485
 486                 /* and try new method */
 487                 if (method->userauth(authctxt) != 0) {
 488                         debug2("we sent a %s packet, wait for reply", method->name);
 489                         break;
 490                 } else {
 491                         debug2("we did not send a packet, disable method");
 492                         method->enabled = NULL;
 493                 }
 494         }
 495 }
 496
 497 /* ARGSUSED */
 498 void
 499 input_userauth_error(int type, u_int32_t seq, void *ctxt)
 500 {
 501         fatal("input_userauth_error: bad message during authentication: "
 502             "type %d", type);
 503 }
 504
 505 /* ARGSUSED */
 506 void
 507 input_userauth_banner(int type, u_int32_t seq, void *ctxt)
 508 {
 509         char *msg, *raw, *lang;
 510         u_int len;
 511
 512         debug3("input_userauth_banner");
 513         raw = packet_get_string(&len);
 514         lang = packet_get_string(NULL);
 515         if (len > 0 && options.log_level >= SYSLOG_LEVEL_INFO) {
 516                 if (len > 65536)
 517                         len = 65536;
 518                 msg = xmalloc(len * 4 + 1); /* max expansion from strnvis() */
 519                 strnvis(msg, raw, len * 4 + 1, VIS_SAFE|VIS_OCTAL|VIS_NOSLASH);
 520                 fprintf(stderr, "%s", msg);
 521                 xfree(msg);
 522         }
 523         xfree(raw);
 524         xfree(lang);
 525 }
 526
 527 /* ARGSUSED */
 528 void
 529 input_userauth_success(int type, u_int32_t seq, void *ctxt)
 530 {
 531         Authctxt *authctxt = ctxt;
 532
 533         if (authctxt == NULL)
 534                 fatal("input_userauth_success: no authentication context");
 535         if (authctxt->authlist) {
 536                 xfree(authctxt->authlist);
 537                 authctxt->authlist = NULL;
 538         }
 539         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 540                 authctxt->method->cleanup(authctxt);
 541         if (authctxt->methoddata) {
 542                 xfree(authctxt->methoddata);
 543                 authctxt->methoddata = NULL;
 544         }
 545         authctxt->success = 1;                  /* break out */
 546 }
 547
 548 void
 549 input_userauth_success_unexpected(int type, u_int32_t seq, void *ctxt)
 550 {
 551         Authctxt *authctxt = ctxt;
 552
 553         if (authctxt == NULL)
 554                 fatal("%s: no authentication context", __func__);
 555
 556         fatal("Unexpected authentication success during %s.",
 557             authctxt->method->name);
 558 }
 559
 560 /* ARGSUSED */
 561 void
 562 input_userauth_failure(int type, u_int32_t seq, void *ctxt)
 563 {
 564         Authctxt *authctxt = ctxt;
 565         char *authlist = NULL;
 566         int partial;
 567
 568         if (authctxt == NULL)
 569                 fatal("input_userauth_failure: no authentication context");
 570
 571         authlist = packet_get_string(NULL);
 572         partial = packet_get_char();
 573         packet_check_eom();
 574
 575         if (partial != 0)
 576                 logit("Authenticated with partial success.");
 577         debug("Authentications that can continue: %s", authlist);
 578
 579         userauth(authctxt, authlist);
 580 }
 581
 582 /* ARGSUSED */
 583 void
 584 input_userauth_pk_ok(int type, u_int32_t seq, void *ctxt)
 585 {
 586         Authctxt *authctxt = ctxt;
 587         Key *key = NULL;
 588         Identity *id = NULL;
 589         Buffer b;
 590         int pktype, sent = 0;
 591         u_int alen, blen;
 592         char *pkalg, *fp;
 593         u_char *pkblob;
 594
 595         if (authctxt == NULL)
 596                 fatal("input_userauth_pk_ok: no authentication context");
 597         if (datafellows & SSH_BUG_PKOK) {
 598                 /* this is similar to SSH_BUG_PKAUTH */
 599                 debug2("input_userauth_pk_ok: SSH_BUG_PKOK");
 600                 pkblob = packet_get_string(&blen);
 601                 buffer_init(&b);
 602                 buffer_append(&b, pkblob, blen);
 603                 pkalg = buffer_get_string(&b, &alen);
 604                 buffer_free(&b);
 605         } else {
 606                 pkalg = packet_get_string(&alen);
 607                 pkblob = packet_get_string(&blen);
 608         }
 609         packet_check_eom();
 610
 611         debug("Server accepts key: pkalg %s blen %u", pkalg, blen);
 612
 613         if ((pktype = key_type_from_name(pkalg)) == KEY_UNSPEC) {
 614                 debug("unknown pkalg %s", pkalg);
 615                 goto done;
 616         }
 617         if ((key = key_from_blob(pkblob, blen)) == NULL) {
 618                 debug("no key from blob. pkalg %s", pkalg);
 619                 goto done;
 620         }
 621         if (key->type != pktype) {
 622                 error("input_userauth_pk_ok: type mismatch "
 623                     "for decoded key (received %d, expected %d)",
 624                     key->type, pktype);
 625                 goto done;
 626         }
 627         fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
 628         debug2("input_userauth_pk_ok: fp %s", fp);
 629         xfree(fp);
 630
 631         /*
 632          * search keys in the reverse order, because last candidate has been
 633          * moved to the end of the queue.  this also avoids confusion by
 634          * duplicate keys
 635          */
 636         TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
 637                 if (key_equal(key, id->key)) {
 638                         sent = sign_and_send_pubkey(authctxt, id);
 639                         break;
 640                 }
 641         }
 642 done:
 643         if (key != NULL)
 644                 key_free(key);
 645         xfree(pkalg);
 646         xfree(pkblob);
 647
 648         /* try another method if we did not send a packet */
 649         if (sent == 0)
 650                 userauth(authctxt, NULL);
 651 }
 652
 653 #ifdef GSSAPI
 654 int
 655 userauth_gssapi(Authctxt *authctxt)
 656 {
 657         Gssctxt *gssctxt = NULL;
 658         static gss_OID_set gss_supported = NULL;
 659         static u_int mech = 0;
 660         OM_uint32 min;
 661         int ok = 0;
 662
 663         /* Try one GSSAPI method at a time, rather than sending them all at
 664          * once. */
 665
 666         if (gss_supported == NULL)
 667                 gss_indicate_mechs(&min, &gss_supported);
 668
 669         /* Check to see if the mechanism is usable before we offer it */
 670         while (mech < gss_supported->count && !ok) {
 671                 /* My DER encoding requires length<128 */
 672                 if (gss_supported->elements[mech].length < 128 &&
 673                     ssh_gssapi_check_mechanism(&gssctxt,
 674                     &gss_supported->elements[mech], authctxt->host)) {
 675                         ok = 1; /* Mechanism works */
 676                 } else {
 677                         mech++;
 678                 }
 679         }
 680
 681         if (!ok)
 682                 return 0;
 683
 684         authctxt->methoddata=(void *)gssctxt;
 685
 686         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 687         packet_put_cstring(authctxt->server_user);
 688         packet_put_cstring(authctxt->service);
 689         packet_put_cstring(authctxt->method->name);
 690
 691         packet_put_int(1);
 692
 693         packet_put_int((gss_supported->elements[mech].length) + 2);
 694         packet_put_char(SSH_GSS_OIDTYPE);
 695         packet_put_char(gss_supported->elements[mech].length);
 696         packet_put_raw(gss_supported->elements[mech].elements,
 697             gss_supported->elements[mech].length);
 698
 699         packet_send();
 700
 701         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
 702         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 703         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
 704         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 705
 706         mech++; /* Move along to next candidate */
 707
 708         return 1;
 709 }
 710
 711 static OM_uint32
 712 process_gssapi_token(void *ctxt, gss_buffer_t recv_tok)
 713 {
 714         Authctxt *authctxt = ctxt;
 715         Gssctxt *gssctxt = authctxt->methoddata;
 716         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 717         gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
 718         gss_buffer_desc gssbuf;
 719         OM_uint32 status, ms, flags;
 720         Buffer b;
 721
 722         status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 723             recv_tok, &send_tok, &flags);
 724
 725         if (send_tok.length > 0) {
 726                 if (GSS_ERROR(status))
 727                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 728                 else
 729                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 730
 731                 packet_put_string(send_tok.value, send_tok.length);
 732                 packet_send();
 733                 gss_release_buffer(&ms, &send_tok);
 734         }
 735
 736         if (status == GSS_S_COMPLETE) {
 737                 /* send either complete or MIC, depending on mechanism */
 738                 if (!(flags & GSS_C_INTEG_FLAG)) {
 739                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
 740                         packet_send();
 741                 } else {
 742                         ssh_gssapi_buildmic(&b, authctxt->server_user,
 743                             authctxt->service, "gssapi-with-mic");
 744
 745                         gssbuf.value = buffer_ptr(&b);
 746                         gssbuf.length = buffer_len(&b);
 747
 748                         status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);
 749
 750                         if (!GSS_ERROR(status)) {
 751                                 packet_start(SSH2_MSG_USERAUTH_GSSAPI_MIC);
 752                                 packet_put_string(mic.value, mic.length);
 753
 754                                 packet_send();
 755                         }
 756
 757                         buffer_free(&b);
 758                         gss_release_buffer(&ms, &mic);
 759                 }
 760         }
 761
 762         return status;
 763 }
 764
 765 /* ARGSUSED */
 766 void
 767 input_gssapi_response(int type, u_int32_t plen, void *ctxt)
 768 {
 769         Authctxt *authctxt = ctxt;
 770         Gssctxt *gssctxt;
 771         int oidlen;
 772         char *oidv;
 773
 774         if (authctxt == NULL)
 775                 fatal("input_gssapi_response: no authentication context");
 776         gssctxt = authctxt->methoddata;
 777
 778         /* Setup our OID */
 779         oidv = packet_get_string(&oidlen);
 780
 781         if (oidlen <= 2 ||
 782             oidv[0] != SSH_GSS_OIDTYPE ||
 783             oidv[1] != oidlen - 2) {
 784                 xfree(oidv);
 785                 debug("Badly encoded mechanism OID received");
 786                 userauth(authctxt, NULL);
 787                 return;
 788         }
 789
 790         if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
 791                 fatal("Server returned different OID than expected");
 792
 793         packet_check_eom();
 794
 795         xfree(oidv);
 796
 797         if (GSS_ERROR(process_gssapi_token(ctxt, GSS_C_NO_BUFFER))) {
 798                 /* Start again with next method on list */
 799                 debug("Trying to start again");
 800                 userauth(authctxt, NULL);
 801                 return;
 802         }
 803 }
 804
 805 /* ARGSUSED */
 806 void
 807 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 808 {
 809         Authctxt *authctxt = ctxt;
 810         gss_buffer_desc recv_tok;
 811         OM_uint32 status;
 812         u_int slen;
 813
 814         if (authctxt == NULL)
 815                 fatal("input_gssapi_response: no authentication context");
 816
 817         recv_tok.value = packet_get_string(&slen);
 818         recv_tok.length = slen; /* safe typecast */
 819
 820         packet_check_eom();
 821
 822         status = process_gssapi_token(ctxt, &recv_tok);
 823
 824         xfree(recv_tok.value);
 825
 826         if (GSS_ERROR(status)) {
 827                 /* Start again with the next method in the list */
 828                 userauth(authctxt, NULL);
 829                 return;
 830         }
 831 }
 832
 833 /* ARGSUSED */
 834 void
 835 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 836 {
 837         Authctxt *authctxt = ctxt;
 838         Gssctxt *gssctxt;
 839         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 840         gss_buffer_desc recv_tok;
 841         OM_uint32 status, ms;
 842         u_int len;
 843
 844         if (authctxt == NULL)
 845                 fatal("input_gssapi_response: no authentication context");
 846         gssctxt = authctxt->methoddata;
 847
 848         recv_tok.value = packet_get_string(&len);
 849         recv_tok.length = len;
 850
 851         packet_check_eom();
 852
 853         /* Stick it into GSSAPI and see what it says */
 854         status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 855             &recv_tok, &send_tok, NULL);
 856
 857         xfree(recv_tok.value);
 858         gss_release_buffer(&ms, &send_tok);
 859
 860         /* Server will be returning a failed packet after this one */
 861 }
 862
 863 /* ARGSUSED */
 864 void
 865 input_gssapi_error(int type, u_int32_t plen, void *ctxt)
 866 {
 867         OM_uint32 maj, min;
 868         char *msg;
 869         char *lang;
 870
 871         maj=packet_get_int();
 872         min=packet_get_int();
 873         msg=packet_get_string(NULL);
 874         lang=packet_get_string(NULL);
 875
 876         packet_check_eom();
 877
 878         debug("Server GSSAPI Error:\n%s", msg);
 879         xfree(msg);
 880         xfree(lang);
 881 }
 882 #endif /* GSSAPI */
 883
 884 int
 885 userauth_none(Authctxt *authctxt)
 886 {
 887         /* initial userauth request */
 888         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 889         packet_put_cstring(authctxt->server_user);
 890         packet_put_cstring(authctxt->service);
 891         packet_put_cstring(authctxt->method->name);
 892         packet_send();
 893         return 1;
 894 }
 895
 896 int
 897 userauth_passwd(Authctxt *authctxt)
 898 {
 899         static int attempt = 0;
 900         char prompt[150];
 901         char *password;
 902         const char *host = options.host_key_alias ?  options.host_key_alias :
 903             authctxt->host;
 904
 905         if (attempt++ >= options.number_of_password_prompts)
 906                 return 0;
 907
 908         if (attempt != 1)
 909                 error("Permission denied, please try again.");
 910
 911         snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
 912             authctxt->server_user, host);
 913         password = read_passphrase(prompt, 0);
 914         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 915         packet_put_cstring(authctxt->server_user);
 916         packet_put_cstring(authctxt->service);
 917         packet_put_cstring(authctxt->method->name);
 918         packet_put_char(0);
 919         packet_put_cstring(password);
 920         memset(password, 0, strlen(password));
 921         xfree(password);
 922         packet_add_padding(64);
 923         packet_send();
 924
 925         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 926             &input_userauth_passwd_changereq);
 927
 928         return 1;
 929 }
 930
 931 /*
 932  * parse PASSWD_CHANGEREQ, prompt user and send SSH2_MSG_USERAUTH_REQUEST
 933  */
 934 /* ARGSUSED */
 935 void
 936 input_userauth_passwd_changereq(int type, u_int32_t seqnr, void *ctxt)
 937 {
 938         Authctxt *authctxt = ctxt;
 939         char *info, *lang, *password = NULL, *retype = NULL;
 940         char prompt[150];
 941         const char *host = options.host_key_alias ? options.host_key_alias :
 942             authctxt->host;
 943
 944         debug2("input_userauth_passwd_changereq");
 945
 946         if (authctxt == NULL)
 947                 fatal("input_userauth_passwd_changereq: "
 948                     "no authentication context");
 949
 950         info = packet_get_string(NULL);
 951         lang = packet_get_string(NULL);
 952         if (strlen(info) > 0)
 953                 logit("%s", info);
 954         xfree(info);
 955         xfree(lang);
 956         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 957         packet_put_cstring(authctxt->server_user);
 958         packet_put_cstring(authctxt->service);
 959         packet_put_cstring(authctxt->method->name);
 960         packet_put_char(1);                     /* additional info */
 961         snprintf(prompt, sizeof(prompt),
 962             "Enter %.30s@%.128s's old password: ",
 963             authctxt->server_user, host);
 964         password = read_passphrase(prompt, 0);
 965         packet_put_cstring(password);
 966         memset(password, 0, strlen(password));
 967         xfree(password);
 968         password = NULL;
 969         while (password == NULL) {
 970                 snprintf(prompt, sizeof(prompt),
 971                     "Enter %.30s@%.128s's new password: ",
 972                     authctxt->server_user, host);
 973                 password = read_passphrase(prompt, RP_ALLOW_EOF);
 974                 if (password == NULL) {
 975                         /* bail out */
 976                         return;
 977                 }
 978                 snprintf(prompt, sizeof(prompt),
 979                     "Retype %.30s@%.128s's new password: ",
 980                     authctxt->server_user, host);
 981                 retype = read_passphrase(prompt, 0);
 982                 if (strcmp(password, retype) != 0) {
 983                         memset(password, 0, strlen(password));
 984                         xfree(password);
 985                         logit("Mismatch; try again, EOF to quit.");
 986                         password = NULL;
 987                 }
 988                 memset(retype, 0, strlen(retype));
 989                 xfree(retype);
 990         }
 991         packet_put_cstring(password);
 992         memset(password, 0, strlen(password));
 993         xfree(password);
 994         packet_add_padding(64);
 995         packet_send();
 996
 997         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 998             &input_userauth_passwd_changereq);
 999 }
1000
1001 #ifdef JPAKE
1002 static char *
1003 pw_encrypt(const char *password, const char *crypt_scheme, const char *salt)
1004 {
1005         /* OpenBSD crypt(3) handles all of these */
1006         if (strcmp(crypt_scheme, "crypt") == 0 ||
1007             strcmp(crypt_scheme, "bcrypt") == 0 ||
1008             strcmp(crypt_scheme, "md5crypt") == 0 ||
1009             strcmp(crypt_scheme, "crypt-extended") == 0)
1010                 return xstrdup(crypt(password, salt));
1011         error("%s: unsupported password encryption scheme \"%.100s\"",
1012             __func__, crypt_scheme);
1013         return NULL;
1014 }
1015
1016 static BIGNUM *
1017 jpake_password_to_secret(Authctxt *authctxt, const char *crypt_scheme,
1018     const char *salt)
1019 {
1020         char prompt[256], *password, *crypted;
1021         u_char *secret;
1022         u_int secret_len;
1023         BIGNUM *ret;
1024
1025         snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password (JPAKE): ",
1026             authctxt->server_user, authctxt->host);
1027         password = read_passphrase(prompt, 0);
1028
1029         if ((crypted = pw_encrypt(password, crypt_scheme, salt)) == NULL) {
1030                 logit("Disabling %s authentication", authctxt->method->name);
1031                 authctxt->method->enabled = NULL;
1032                 /* Continue with an empty password to fail gracefully */
1033                 crypted = xstrdup("");
1034         }
1035
1036 #ifdef JPAKE_DEBUG
1037         debug3("%s: salt = %s", __func__, salt);
1038         debug3("%s: scheme = %s", __func__, crypt_scheme);
1039         debug3("%s: crypted = %s", __func__, crypted);
1040 #endif
1041
1042         if (hash_buffer(crypted, strlen(crypted), EVP_sha256(),
1043             &secret, &secret_len) != 0)
1044                 fatal("%s: hash_buffer", __func__);
1045
1046         bzero(password, strlen(password));
1047         bzero(crypted, strlen(crypted));
1048         xfree(password);
1049         xfree(crypted);
1050
1051         if ((ret = BN_bin2bn(secret, secret_len, NULL)) == NULL)
1052                 fatal("%s: BN_bin2bn (secret)", __func__);
1053         bzero(secret, secret_len);
1054         xfree(secret);
1055
1056         return ret;
1057 }
1058
1059 /* ARGSUSED */
1060 void
1061 input_userauth_jpake_server_step1(int type, u_int32_t seq, void *ctxt)
1062 {
1063         Authctxt *authctxt = ctxt;
1064         struct jpake_ctx *pctx = authctxt->methoddata;
1065         u_char *x3_proof, *x4_proof, *x2_s_proof;
1066         u_int x3_proof_len, x4_proof_len, x2_s_proof_len;
1067         char *crypt_scheme, *salt;
1068
1069         /* Disable this message */
1070         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP1, NULL);
1071
1072         if ((pctx->g_x3 = BN_new()) == NULL ||
1073             (pctx->g_x4 = BN_new()) == NULL)
1074                 fatal("%s: BN_new", __func__);
1075
1076         /* Fetch step 1 values */
1077         crypt_scheme = packet_get_string(NULL);
1078         salt = packet_get_string(NULL);
1079         pctx->server_id = packet_get_string(&pctx->server_id_len);
1080         packet_get_bignum2(pctx->g_x3);
1081         packet_get_bignum2(pctx->g_x4);
1082         x3_proof = packet_get_string(&x3_proof_len);
1083         x4_proof = packet_get_string(&x4_proof_len);
1084         packet_check_eom();
1085
1086         JPAKE_DEBUG_CTX((pctx, "step 1 received in %s", __func__));
1087
1088         /* Obtain password and derive secret */
1089         pctx->s = jpake_password_to_secret(authctxt, crypt_scheme, salt);
1090         bzero(crypt_scheme, strlen(crypt_scheme));
1091         bzero(salt, strlen(salt));
1092         xfree(crypt_scheme);
1093         xfree(salt);
1094         JPAKE_DEBUG_BN((pctx->s, "%s: s = ", __func__));
1095
1096         /* Calculate step 2 values */
1097         jpake_step2(pctx->grp, pctx->s, pctx->g_x1,
1098             pctx->g_x3, pctx->g_x4, pctx->x2,
1099             pctx->server_id, pctx->server_id_len,
1100             pctx->client_id, pctx->client_id_len,
1101             x3_proof, x3_proof_len,
1102             x4_proof, x4_proof_len,
1103             &pctx->a,
1104             &x2_s_proof, &x2_s_proof_len);
1105
1106         bzero(x3_proof, x3_proof_len);
1107         bzero(x4_proof, x4_proof_len);
1108         xfree(x3_proof);
1109         xfree(x4_proof);
1110
1111         JPAKE_DEBUG_CTX((pctx, "step 2 sending in %s", __func__));
1112
1113         /* Send values for step 2 */
1114         packet_start(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2);
1115         packet_put_bignum2(pctx->a);
1116         packet_put_string(x2_s_proof, x2_s_proof_len);
1117         packet_send();
1118
1119         bzero(x2_s_proof, x2_s_proof_len);
1120         xfree(x2_s_proof);
1121
1122         /* Expect step 2 packet from peer */
1123         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP2,
1124             input_userauth_jpake_server_step2);
1125 }
1126
1127 /* ARGSUSED */
1128 void
1129 input_userauth_jpake_server_step2(int type, u_int32_t seq, void *ctxt)
1130 {
1131         Authctxt *authctxt = ctxt;
1132         struct jpake_ctx *pctx = authctxt->methoddata;
1133         u_char *x4_s_proof;
1134         u_int x4_s_proof_len;
1135
1136         /* Disable this message */
1137         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP2, NULL);
1138
1139         if ((pctx->b = BN_new()) == NULL)
1140                 fatal("%s: BN_new", __func__);
1141
1142         /* Fetch step 2 values */
1143         packet_get_bignum2(pctx->b);
1144         x4_s_proof = packet_get_string(&x4_s_proof_len);
1145         packet_check_eom();
1146
1147         JPAKE_DEBUG_CTX((pctx, "step 2 received in %s", __func__));
1148
1149         /* Derive shared key and calculate confirmation hash */
1150         jpake_key_confirm(pctx->grp, pctx->s, pctx->b,
1151             pctx->x2, pctx->g_x1, pctx->g_x2, pctx->g_x3, pctx->g_x4,
1152             pctx->client_id, pctx->client_id_len,
1153             pctx->server_id, pctx->server_id_len,
1154             session_id2, session_id2_len,
1155             x4_s_proof, x4_s_proof_len,
1156             &pctx->k,
1157             &pctx->h_k_cid_sessid, &pctx->h_k_cid_sessid_len);
1158
1159         bzero(x4_s_proof, x4_s_proof_len);
1160         xfree(x4_s_proof);
1161
1162         JPAKE_DEBUG_CTX((pctx, "confirm sending in %s", __func__));
1163
1164         /* Send key confirmation proof */
1165         packet_start(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM);
1166         packet_put_string(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
1167         packet_send();
1168
1169         /* Expect confirmation from peer */
1170         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_CONFIRM,
1171             input_userauth_jpake_server_confirm);
1172 }
1173
1174 /* ARGSUSED */
1175 void
1176 input_userauth_jpake_server_confirm(int type, u_int32_t seq, void *ctxt)
1177 {
1178         Authctxt *authctxt = ctxt;
1179         struct jpake_ctx *pctx = authctxt->methoddata;
1180
1181         /* Disable this message */
1182         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_CONFIRM, NULL);
1183
1184         pctx->h_k_sid_sessid = packet_get_string(&pctx->h_k_sid_sessid_len);
1185         packet_check_eom();
1186
1187         JPAKE_DEBUG_CTX((pctx, "confirm received in %s", __func__));
1188
1189         /* Verify expected confirmation hash */
1190         if (jpake_check_confirm(pctx->k,
1191             pctx->server_id, pctx->server_id_len,
1192             session_id2, session_id2_len,
1193             pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len) == 1)
1194                 debug("%s: %s success", __func__, authctxt->method->name);
1195         else {
1196                 debug("%s: confirmation mismatch", __func__);
1197                 /* XXX stash this so if auth succeeds then we can warn/kill */
1198         }
1199
1200         userauth_jpake_cleanup(authctxt);
1201 }
1202 #endif /* JPAKE */
1203
1204 static int
1205 identity_sign(Identity *id, u_char **sigp, u_int *lenp,
1206     u_char *data, u_int datalen)
1207 {
1208         Key *prv;
1209         int ret;
1210
1211         /* the agent supports this key */
1212         if (id->ac)
1213                 return (ssh_agent_sign(id->ac, id->key, sigp, lenp,
1214                     data, datalen));
1215         /*
1216          * we have already loaded the private key or
1217          * the private key is stored in external hardware
1218          */
1219         if (id->isprivate || (id->key->flags & KEY_FLAG_EXT))
1220                 return (key_sign(id->key, sigp, lenp, data, datalen));
1221         /* load the private key from the file */
1222         if ((prv = load_identity_file(id->filename)) == NULL)
1223                 return (-1);
1224         ret = key_sign(prv, sigp, lenp, data, datalen);
1225         key_free(prv);
1226         return (ret);
1227 }
1228
1229 static int
1230 sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
1231 {
1232         Buffer b;
1233         u_char *blob, *signature;
1234         u_int bloblen, slen;
1235         u_int skip = 0;
1236         int ret = -1;
1237         int have_sig = 1;
1238         char *fp;
1239
1240         fp = key_fingerprint(id->key, SSH_FP_MD5, SSH_FP_HEX);
1241         debug3("sign_and_send_pubkey: %s %s", key_type(id->key), fp);
1242         xfree(fp);
1243
1244         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1245                 /* we cannot handle this key */
1246                 debug3("sign_and_send_pubkey: cannot handle key");
1247                 return 0;
1248         }
1249         /* data to be signed */
1250         buffer_init(&b);
1251         if (datafellows & SSH_OLD_SESSIONID) {
1252                 buffer_append(&b, session_id2, session_id2_len);
1253                 skip = session_id2_len;
1254         } else {
1255                 buffer_put_string(&b, session_id2, session_id2_len);
1256                 skip = buffer_len(&b);
1257         }
1258         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1259         buffer_put_cstring(&b, authctxt->server_user);
1260         buffer_put_cstring(&b,
1261             datafellows & SSH_BUG_PKSERVICE ?
1262             "ssh-userauth" :
1263             authctxt->service);
1264         if (datafellows & SSH_BUG_PKAUTH) {
1265                 buffer_put_char(&b, have_sig);
1266         } else {
1267                 buffer_put_cstring(&b, authctxt->method->name);
1268                 buffer_put_char(&b, have_sig);
1269                 buffer_put_cstring(&b, key_ssh_name(id->key));
1270         }
1271         buffer_put_string(&b, blob, bloblen);
1272
1273         /* generate signature */
1274         ret = identity_sign(id, &signature, &slen,
1275             buffer_ptr(&b), buffer_len(&b));
1276         if (ret == -1) {
1277                 xfree(blob);
1278                 buffer_free(&b);
1279                 return 0;
1280         }
1281 #ifdef DEBUG_PK
1282         buffer_dump(&b);
1283 #endif
1284         if (datafellows & SSH_BUG_PKSERVICE) {
1285                 buffer_clear(&b);
1286                 buffer_append(&b, session_id2, session_id2_len);
1287                 skip = session_id2_len;
1288                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1289                 buffer_put_cstring(&b, authctxt->server_user);
1290                 buffer_put_cstring(&b, authctxt->service);
1291                 buffer_put_cstring(&b, authctxt->method->name);
1292                 buffer_put_char(&b, have_sig);
1293                 if (!(datafellows & SSH_BUG_PKAUTH))
1294                         buffer_put_cstring(&b, key_ssh_name(id->key));
1295                 buffer_put_string(&b, blob, bloblen);
1296         }
1297         xfree(blob);
1298
1299         /* append signature */
1300         buffer_put_string(&b, signature, slen);
1301         xfree(signature);
1302
1303         /* skip session id and packet type */
1304         if (buffer_len(&b) < skip + 1)
1305                 fatal("userauth_pubkey: internal error");
1306         buffer_consume(&b, skip + 1);
1307
1308         /* put remaining data from buffer into packet */
1309         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1310         packet_put_raw(buffer_ptr(&b), buffer_len(&b));
1311         buffer_free(&b);
1312         packet_send();
1313
1314         return 1;
1315 }
1316
1317 static int
1318 send_pubkey_test(Authctxt *authctxt, Identity *id)
1319 {
1320         u_char *blob;
1321         u_int bloblen, have_sig = 0;
1322
1323         debug3("send_pubkey_test");
1324
1325         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1326                 /* we cannot handle this key */
1327                 debug3("send_pubkey_test: cannot handle key");
1328                 return 0;
1329         }
1330         /* register callback for USERAUTH_PK_OK message */
1331         dispatch_set(SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
1332
1333         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1334         packet_put_cstring(authctxt->server_user);
1335         packet_put_cstring(authctxt->service);
1336         packet_put_cstring(authctxt->method->name);
1337         packet_put_char(have_sig);
1338         if (!(datafellows & SSH_BUG_PKAUTH))
1339                 packet_put_cstring(key_ssh_name(id->key));
1340         packet_put_string(blob, bloblen);
1341         xfree(blob);
1342         packet_send();
1343         return 1;
1344 }
1345
1346 static Key *
1347 load_identity_file(char *filename)
1348 {
1349         Key *private;
1350         char prompt[300], *passphrase;
1351         int perm_ok = 0, quit, i;
1352         struct stat st;
1353
1354         if (stat(filename, &st) < 0) {
1355                 debug3("no such identity: %s", filename);
1356                 return NULL;
1357         }
1358         private = key_load_private_type(KEY_UNSPEC, filename, "", NULL, &perm_ok);
1359         if (!perm_ok)
1360                 return NULL;
1361         if (private == NULL) {
1362                 if (options.batch_mode)
1363                         return NULL;
1364                 snprintf(prompt, sizeof prompt,
1365                     "Enter passphrase for key '%.100s': ", filename);
1366                 for (i = 0; i < options.number_of_password_prompts; i++) {
1367                         passphrase = read_passphrase(prompt, 0);
1368                         if (strcmp(passphrase, "") != 0) {
1369                                 private = key_load_private_type(KEY_UNSPEC,
1370                                     filename, passphrase, NULL, NULL);
1371                                 quit = 0;
1372                         } else {
1373                                 debug2("no passphrase given, try next key");
1374                                 quit = 1;
1375                         }
1376                         memset(passphrase, 0, strlen(passphrase));
1377                         xfree(passphrase);
1378                         if (private != NULL || quit)
1379                                 break;
1380                         debug2("bad passphrase given, try again...");
1381                 }
1382         }
1383         return private;
1384 }
1385
1386 /*
1387  * try keys in the following order:
1388  *      1. agent keys that are found in the config file
1389  *      2. other agent keys
1390  *      3. keys that are only listed in the config file
1391  */
1392 static void
1393 pubkey_prepare(Authctxt *authctxt)
1394 {
1395         Identity *id;
1396         Idlist agent, files, *preferred;
1397         Key *key;
1398         AuthenticationConnection *ac;
1399         char *comment;
1400         int i, found;
1401
1402         TAILQ_INIT(&agent);     /* keys from the agent */
1403         TAILQ_INIT(&files);     /* keys from the config file */
1404         preferred = &authctxt->keys;
1405         TAILQ_INIT(preferred);  /* preferred order of keys */
1406
1407         /* list of keys stored in the filesystem */
1408         for (i = 0; i < options.num_identity_files; i++) {
1409                 key = options.identity_keys[i];
1410                 if (key && key->type == KEY_RSA1)
1411                         continue;
1412                 if (key && key->cert && key->cert->type != SSH2_CERT_TYPE_USER)
1413                         continue;
1414                 options.identity_keys[i] = NULL;
1415                 id = xcalloc(1, sizeof(*id));
1416                 id->key = key;
1417                 id->filename = xstrdup(options.identity_files[i]);
1418                 TAILQ_INSERT_TAIL(&files, id, next);
1419         }
1420         /* list of keys supported by the agent */
1421         if ((ac = ssh_get_authentication_connection())) {
1422                 for (key = ssh_get_first_identity(ac, &comment, 2);
1423                     key != NULL;
1424                     key = ssh_get_next_identity(ac, &comment, 2)) {
1425                         found = 0;
1426                         TAILQ_FOREACH(id, &files, next) {
1427                                 /* agent keys from the config file are preferred */
1428                                 if (key_equal(key, id->key)) {
1429                                         key_free(key);
1430                                         xfree(comment);
1431                                         TAILQ_REMOVE(&files, id, next);
1432                                         TAILQ_INSERT_TAIL(preferred, id, next);
1433                                         id->ac = ac;
1434                                         found = 1;
1435                                         break;
1436                                 }
1437                         }
1438                         if (!found && !options.identities_only) {
1439                                 id = xcalloc(1, sizeof(*id));
1440                                 id->key = key;
1441                                 id->filename = comment;
1442                                 id->ac = ac;
1443                                 TAILQ_INSERT_TAIL(&agent, id, next);
1444                         }
1445                 }
1446                 /* append remaining agent keys */
1447                 for (id = TAILQ_FIRST(&agent); id; id = TAILQ_FIRST(&agent)) {
1448                         TAILQ_REMOVE(&agent, id, next);
1449                         TAILQ_INSERT_TAIL(preferred, id, next);
1450                 }
1451                 authctxt->agent = ac;
1452         }
1453         /* append remaining keys from the config file */
1454         for (id = TAILQ_FIRST(&files); id; id = TAILQ_FIRST(&files)) {
1455                 TAILQ_REMOVE(&files, id, next);
1456                 TAILQ_INSERT_TAIL(preferred, id, next);
1457         }
1458         TAILQ_FOREACH(id, preferred, next) {
1459                 debug2("key: %s (%p)", id->filename, id->key);
1460         }
1461 }
1462
1463 static void
1464 pubkey_cleanup(Authctxt *authctxt)
1465 {
1466         Identity *id;
1467
1468         if (authctxt->agent != NULL)
1469                 ssh_close_authentication_connection(authctxt->agent);
1470         for (id = TAILQ_FIRST(&authctxt->keys); id;
1471             id = TAILQ_FIRST(&authctxt->keys)) {
1472                 TAILQ_REMOVE(&authctxt->keys, id, next);
1473                 if (id->key)
1474                         key_free(id->key);
1475                 if (id->filename)
1476                         xfree(id->filename);
1477                 xfree(id);
1478         }
1479 }
1480
1481 int
1482 userauth_pubkey(Authctxt *authctxt)
1483 {
1484         Identity *id;
1485         int sent = 0;
1486
1487         while ((id = TAILQ_FIRST(&authctxt->keys))) {
1488                 if (id->tried++)
1489                         return (0);
1490                 /* move key to the end of the queue */
1491                 TAILQ_REMOVE(&authctxt->keys, id, next);
1492                 TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
1493                 /*
1494                  * send a test message if we have the public key. for
1495                  * encrypted keys we cannot do this and have to load the
1496                  * private key instead
1497                  */
1498                 if (id->key && id->key->type != KEY_RSA1) {
1499                         debug("Offering %s public key: %s", key_type(id->key),
1500                             id->filename);
1501                         sent = send_pubkey_test(authctxt, id);
1502                 } else if (id->key == NULL) {
1503                         debug("Trying private key: %s", id->filename);
1504                         id->key = load_identity_file(id->filename);
1505                         if (id->key != NULL) {
1506                                 id->isprivate = 1;
1507                                 sent = sign_and_send_pubkey(authctxt, id);
1508                                 key_free(id->key);
1509                                 id->key = NULL;
1510                         }
1511                 }
1512                 if (sent)
1513                         return (sent);
1514         }
1515         return (0);
1516 }
1517
1518 /*
1519  * Send userauth request message specifying keyboard-interactive method.
1520  */
1521 int
1522 userauth_kbdint(Authctxt *authctxt)
1523 {
1524         static int attempt = 0;
1525
1526         if (attempt++ >= options.number_of_password_prompts)
1527                 return 0;
1528         /* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
1529         if (attempt > 1 && !authctxt->info_req_seen) {
1530                 debug3("userauth_kbdint: disable: no info_req_seen");
1531                 dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
1532                 return 0;
1533         }
1534
1535         debug2("userauth_kbdint");
1536         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1537         packet_put_cstring(authctxt->server_user);
1538         packet_put_cstring(authctxt->service);
1539         packet_put_cstring(authctxt->method->name);
1540         packet_put_cstring("");                                 /* lang */
1541         packet_put_cstring(options.kbd_interactive_devices ?
1542             options.kbd_interactive_devices : "");
1543         packet_send();
1544
1545         dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
1546         return 1;
1547 }
1548
1549 /*
1550  * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
1551  */
1552 void
1553 input_userauth_info_req(int type, u_int32_t seq, void *ctxt)
1554 {
1555         Authctxt *authctxt = ctxt;
1556         char *name, *inst, *lang, *prompt, *response;
1557         u_int num_prompts, i;
1558         int echo = 0;
1559
1560         debug2("input_userauth_info_req");
1561
1562         if (authctxt == NULL)
1563                 fatal("input_userauth_info_req: no authentication context");
1564
1565         authctxt->info_req_seen = 1;
1566
1567         name = packet_get_string(NULL);
1568         inst = packet_get_string(NULL);
1569         lang = packet_get_string(NULL);
1570         if (strlen(name) > 0)
1571                 logit("%s", name);
1572         if (strlen(inst) > 0)
1573                 logit("%s", inst);
1574         xfree(name);
1575         xfree(inst);
1576         xfree(lang);
1577
1578         num_prompts = packet_get_int();
1579         /*
1580          * Begin to build info response packet based on prompts requested.
1581          * We commit to providing the correct number of responses, so if
1582          * further on we run into a problem that prevents this, we have to
1583          * be sure and clean this up and send a correct error response.
1584          */
1585         packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
1586         packet_put_int(num_prompts);
1587
1588         debug2("input_userauth_info_req: num_prompts %d", num_prompts);
1589         for (i = 0; i < num_prompts; i++) {
1590                 prompt = packet_get_string(NULL);
1591                 echo = packet_get_char();
1592
1593                 response = read_passphrase(prompt, echo ? RP_ECHO : 0);
1594
1595                 packet_put_cstring(response);
1596                 memset(response, 0, strlen(response));
1597                 xfree(response);
1598                 xfree(prompt);
1599         }
1600         packet_check_eom(); /* done with parsing incoming message. */
1601
1602         packet_add_padding(64);
1603         packet_send();
1604 }
1605
1606 static int
1607 ssh_keysign(Key *key, u_char **sigp, u_int *lenp,
1608     u_char *data, u_int datalen)
1609 {
1610         Buffer b;
1611         struct stat st;
1612         pid_t pid;
1613         int to[2], from[2], status, version = 2;
1614
1615         debug2("ssh_keysign called");
1616
1617         if (stat(_PATH_SSH_KEY_SIGN, &st) < 0) {
1618                 error("ssh_keysign: not installed: %s", strerror(errno));
1619                 return -1;
1620         }
1621         if (fflush(stdout) != 0)
1622                 error("ssh_keysign: fflush: %s", strerror(errno));
1623         if (pipe(to) < 0) {
1624                 error("ssh_keysign: pipe: %s", strerror(errno));
1625                 return -1;
1626         }
1627         if (pipe(from) < 0) {
1628                 error("ssh_keysign: pipe: %s", strerror(errno));
1629                 return -1;
1630         }
1631         if ((pid = fork()) < 0) {
1632                 error("ssh_keysign: fork: %s", strerror(errno));
1633                 return -1;
1634         }
1635         if (pid == 0) {
1636                 /* keep the socket on exec */
1637                 fcntl(packet_get_connection_in(), F_SETFD, 0);
1638                 permanently_drop_suid(getuid());
1639                 close(from[0]);
1640                 if (dup2(from[1], STDOUT_FILENO) < 0)
1641                         fatal("ssh_keysign: dup2: %s", strerror(errno));
1642                 close(to[1]);
1643                 if (dup2(to[0], STDIN_FILENO) < 0)
1644                         fatal("ssh_keysign: dup2: %s", strerror(errno));
1645                 close(from[1]);
1646                 close(to[0]);
1647                 execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *) 0);
1648                 fatal("ssh_keysign: exec(%s): %s", _PATH_SSH_KEY_SIGN,
1649                     strerror(errno));
1650         }
1651         close(from[1]);
1652         close(to[0]);
1653
1654         buffer_init(&b);
1655         buffer_put_int(&b, packet_get_connection_in()); /* send # of socket */
1656         buffer_put_string(&b, data, datalen);
1657         if (ssh_msg_send(to[1], version, &b) == -1)
1658                 fatal("ssh_keysign: couldn't send request");
1659
1660         if (ssh_msg_recv(from[0], &b) < 0) {
1661                 error("ssh_keysign: no reply");
1662                 buffer_free(&b);
1663                 return -1;
1664         }
1665         close(from[0]);
1666         close(to[1]);
1667
1668         while (waitpid(pid, &status, 0) < 0)
1669                 if (errno != EINTR)
1670                         break;
1671
1672         if (buffer_get_char(&b) != version) {
1673                 error("ssh_keysign: bad version");
1674                 buffer_free(&b);
1675                 return -1;
1676         }
1677         *sigp = buffer_get_string(&b, lenp);
1678         buffer_free(&b);
1679
1680         return 0;
1681 }
1682
1683 int
1684 userauth_hostbased(Authctxt *authctxt)
1685 {
1686         Key *private = NULL;
1687         Sensitive *sensitive = authctxt->sensitive;
1688         Buffer b;
1689         u_char *signature, *blob;
1690         char *chost, *pkalg, *p;
1691         const char *service;
1692         u_int blen, slen;
1693         int ok, i, found = 0;
1694
1695         /* check for a useful key */
1696         for (i = 0; i < sensitive->nkeys; i++) {
1697                 private = sensitive->keys[i];
1698                 if (private && private->type != KEY_RSA1) {
1699                         found = 1;
1700                         /* we take and free the key */
1701                         sensitive->keys[i] = NULL;
1702                         break;
1703                 }
1704         }
1705         if (!found) {
1706                 debug("No more client hostkeys for hostbased authentication.");
1707                 return 0;
1708         }
1709         if (key_to_blob(private, &blob, &blen) == 0) {
1710                 key_free(private);
1711                 return 0;
1712         }
1713         /* figure out a name for the client host */
1714         p = get_local_name(packet_get_connection_in());
1715         if (p == NULL) {
1716                 error("userauth_hostbased: cannot get local ipaddr/name");
1717                 key_free(private);
1718                 xfree(blob);
1719                 return 0;
1720         }
1721         xasprintf(&chost, "%s.", p);
1722         debug2("userauth_hostbased: chost %s", chost);
1723         xfree(p);
1724
1725         service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
1726             authctxt->service;
1727         pkalg = xstrdup(key_ssh_name(private));
1728         buffer_init(&b);
1729         /* construct data */
1730         buffer_put_string(&b, session_id2, session_id2_len);
1731         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1732         buffer_put_cstring(&b, authctxt->server_user);
1733         buffer_put_cstring(&b, service);
1734         buffer_put_cstring(&b, authctxt->method->name);
1735         buffer_put_cstring(&b, pkalg);
1736         buffer_put_string(&b, blob, blen);
1737         buffer_put_cstring(&b, chost);
1738         buffer_put_cstring(&b, authctxt->local_user);
1739 #ifdef DEBUG_PK
1740         buffer_dump(&b);
1741 #endif
1742         if (sensitive->external_keysign)
1743                 ok = ssh_keysign(private, &signature, &slen,
1744                     buffer_ptr(&b), buffer_len(&b));
1745         else
1746                 ok = key_sign(private, &signature, &slen,
1747                     buffer_ptr(&b), buffer_len(&b));
1748         key_free(private);
1749         buffer_free(&b);
1750         if (ok != 0) {
1751                 error("key_sign failed");
1752                 xfree(chost);
1753                 xfree(pkalg);
1754                 xfree(blob);
1755                 return 0;
1756         }
1757         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1758         packet_put_cstring(authctxt->server_user);
1759         packet_put_cstring(authctxt->service);
1760         packet_put_cstring(authctxt->method->name);
1761         packet_put_cstring(pkalg);
1762         packet_put_string(blob, blen);
1763         packet_put_cstring(chost);
1764         packet_put_cstring(authctxt->local_user);
1765         packet_put_string(signature, slen);
1766         memset(signature, 's', slen);
1767         xfree(signature);
1768         xfree(chost);
1769         xfree(pkalg);
1770         xfree(blob);
1771
1772         packet_send();
1773         return 1;
1774 }
1775
1776 #ifdef JPAKE
1777 int
1778 userauth_jpake(Authctxt *authctxt)
1779 {
1780         struct jpake_ctx *pctx;
1781         u_char *x1_proof, *x2_proof;
1782         u_int x1_proof_len, x2_proof_len;
1783         static int attempt = 0; /* XXX share with userauth_password's? */
1784
1785         if (attempt++ >= options.number_of_password_prompts)
1786                 return 0;
1787         if (attempt != 1)
1788                 error("Permission denied, please try again.");
1789
1790         if (authctxt->methoddata != NULL)
1791                 fatal("%s: authctxt->methoddata already set (%p)",
1792                     __func__, authctxt->methoddata);
1793
1794         authctxt->methoddata = pctx = jpake_new();
1795
1796         /*
1797          * Send request immediately, to get the protocol going while
1798          * we do the initial computations.
1799          */
1800         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1801         packet_put_cstring(authctxt->server_user);
1802         packet_put_cstring(authctxt->service);
1803         packet_put_cstring(authctxt->method->name);
1804         packet_send();
1805         packet_write_wait();
1806
1807         jpake_step1(pctx->grp,
1808             &pctx->client_id, &pctx->client_id_len,
1809             &pctx->x1, &pctx->x2, &pctx->g_x1, &pctx->g_x2,
1810             &x1_proof, &x1_proof_len,
1811             &x2_proof, &x2_proof_len);
1812
1813         JPAKE_DEBUG_CTX((pctx, "step 1 sending in %s", __func__));
1814
1815         packet_start(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1);
1816         packet_put_string(pctx->client_id, pctx->client_id_len);
1817         packet_put_bignum2(pctx->g_x1);
1818         packet_put_bignum2(pctx->g_x2);
1819         packet_put_string(x1_proof, x1_proof_len);
1820         packet_put_string(x2_proof, x2_proof_len);
1821         packet_send();
1822
1823         bzero(x1_proof, x1_proof_len);
1824         bzero(x2_proof, x2_proof_len);
1825         xfree(x1_proof);
1826         xfree(x2_proof);
1827
1828         /* Expect step 1 packet from peer */
1829         dispatch_set(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP1,
1830             input_userauth_jpake_server_step1);
1831         dispatch_set(SSH2_MSG_USERAUTH_SUCCESS,
1832             &input_userauth_success_unexpected);
1833
1834         return 1;
1835 }
1836
1837 void
1838 userauth_jpake_cleanup(Authctxt *authctxt)
1839 {
1840         debug3("%s: clean up", __func__);
1841         if (authctxt->methoddata != NULL) {
1842                 jpake_free(authctxt->methoddata);
1843                 authctxt->methoddata = NULL;
1844         }
1845         dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
1846 }
1847 #endif /* JPAKE */
1848
1849 /* find auth method */
1850
1851 /*
1852  * given auth method name, if configurable options permit this method fill
1853  * in auth_ident field and return true, otherwise return false.
1854  */
1855 static int
1856 authmethod_is_enabled(Authmethod *method)
1857 {
1858         if (method == NULL)
1859                 return 0;
1860         /* return false if options indicate this method is disabled */
1861         if  (method->enabled == NULL || *method->enabled == 0)
1862                 return 0;
1863         /* return false if batch mode is enabled but method needs interactive mode */
1864         if  (method->batch_flag != NULL && *method->batch_flag != 0)
1865                 return 0;
1866         return 1;
1867 }
1868
1869 static Authmethod *
1870 authmethod_lookup(const char *name)
1871 {
1872         Authmethod *method = NULL;
1873         if (name != NULL)
1874                 for (method = authmethods; method->name != NULL; method++)
1875                         if (strcmp(name, method->name) == 0)
1876                                 return method;
1877         debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
1878         return NULL;
1879 }
1880
1881 /* XXX internal state */
1882 static Authmethod *current = NULL;
1883 static char *supported = NULL;
1884 static char *preferred = NULL;
1885
1886 /*
1887  * Given the authentication method list sent by the server, return the
1888  * next method we should try.  If the server initially sends a nil list,
1889  * use a built-in default list.
1890  */
1891 static Authmethod *
1892 authmethod_get(char *authlist)
1893 {
1894         char *name = NULL;
1895         u_int next;
1896
1897         /* Use a suitable default if we're passed a nil list.  */
1898         if (authlist == NULL || strlen(authlist) == 0)
1899                 authlist = options.preferred_authentications;
1900
1901         if (supported == NULL || strcmp(authlist, supported) != 0) {
1902                 debug3("start over, passed a different list %s", authlist);
1903                 if (supported != NULL)
1904                         xfree(supported);
1905                 supported = xstrdup(authlist);
1906                 preferred = options.preferred_authentications;
1907                 debug3("preferred %s", preferred);
1908                 current = NULL;
1909         } else if (current != NULL && authmethod_is_enabled(current))
1910                 return current;
1911
1912         for (;;) {
1913                 if ((name = match_list(preferred, supported, &next)) == NULL) {
1914                         debug("No more authentication methods to try.");
1915                         current = NULL;
1916                         return NULL;
1917                 }
1918                 preferred += next;
1919                 debug3("authmethod_lookup %s", name);
1920                 debug3("remaining preferred: %s", preferred);
1921                 if ((current = authmethod_lookup(name)) != NULL &&
1922                     authmethod_is_enabled(current)) {
1923                         debug3("authmethod_is_enabled %s", name);
1924                         debug("Next authentication method: %s", name);
1925                         return current;
1926                 }
1927         }
1928 }
1929
1930 static char *
1931 authmethods_get(void)
1932 {
1933         Authmethod *method = NULL;
1934         Buffer b;
1935         char *list;
1936
1937         buffer_init(&b);
1938         for (method = authmethods; method->name != NULL; method++) {
1939                 if (authmethod_is_enabled(method)) {
1940                         if (buffer_len(&b) > 0)
1941                                 buffer_append(&b, ",", 1);
1942                         buffer_append(&b, method->name, strlen(method->name));
1943                 }
1944         }
1945         buffer_append(&b, "\0", 1);
1946         list = xstrdup(buffer_ptr(&b));
1947         buffer_free(&b);
1948         return list;
1949 }
1950