crypto/openssh/sshconnect2.c

   1 /* $OpenBSD: sshconnect2.c,v 1.247 2016/07/22 05:46:11 dtucker Exp $ */
   2 /*
   3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   4  * Copyright (c) 2008 Damien Miller.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28
  29 #include <sys/types.h>
  30 #include <sys/socket.h>
  31 #include <sys/wait.h>
  32 #include <sys/stat.h>
  33
  34 #include <errno.h>
  35 #include <fcntl.h>
  36 #include <netdb.h>
  37 #include <pwd.h>
  38 #include <signal.h>
  39 #include <stdarg.h>
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43 #if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H) && !defined(BROKEN_STRNVIS)
  44 #include <vis.h>
  45 #endif
  46
  47 #include "openbsd-compat/sys-queue.h"
  48
  49 #include "xmalloc.h"
  50 #include "ssh.h"
  51 #include "ssh2.h"
  52 #include "buffer.h"
  53 #include "packet.h"
  54 #include "compat.h"
  55 #include "cipher.h"
  56 #include "key.h"
  57 #include "kex.h"
  58 #include "myproposal.h"
  59 #include "sshconnect.h"
  60 #include "authfile.h"
  61 #include "dh.h"
  62 #include "authfd.h"
  63 #include "log.h"
  64 #include "misc.h"
  65 #include "readconf.h"
  66 #include "match.h"
  67 #include "dispatch.h"
  68 #include "canohost.h"
  69 #include "msg.h"
  70 #include "pathnames.h"
  71 #include "uidswap.h"
  72 #include "hostfile.h"
  73 #include "ssherr.h"
  74 #include "utf8.h"
  75
  76 #ifdef GSSAPI
  77 #include "ssh-gss.h"
  78 #endif
  79
  80 /* import */
  81 extern char *client_version_string;
  82 extern char *server_version_string;
  83 extern Options options;
  84
  85 /*
  86  * SSH2 key exchange
  87  */
  88
  89 u_char *session_id2 = NULL;
  90 u_int session_id2_len = 0;
  91
  92 char *xxx_host;
  93 struct sockaddr *xxx_hostaddr;
  94
  95 static int
  96 verify_host_key_callback(Key *hostkey, struct ssh *ssh)
  97 {
  98         if (verify_host_key(xxx_host, xxx_hostaddr, hostkey) == -1)
  99                 fatal("Host key verification failed.");
 100         return 0;
 101 }
 102
 103 static char *
 104 order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
 105 {
 106         char *oavail, *avail, *first, *last, *alg, *hostname, *ret;
 107         size_t maxlen;
 108         struct hostkeys *hostkeys;
 109         int ktype;
 110         u_int i;
 111
 112         /* Find all hostkeys for this hostname */
 113         get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
 114         hostkeys = init_hostkeys();
 115         for (i = 0; i < options.num_user_hostfiles; i++)
 116                 load_hostkeys(hostkeys, hostname, options.user_hostfiles[i]);
 117         for (i = 0; i < options.num_system_hostfiles; i++)
 118                 load_hostkeys(hostkeys, hostname, options.system_hostfiles[i]);
 119
 120         oavail = avail = xstrdup(KEX_DEFAULT_PK_ALG);
 121         maxlen = strlen(avail) + 1;
 122         first = xmalloc(maxlen);
 123         last = xmalloc(maxlen);
 124         *first = *last = '\0';
 125
 126 #define ALG_APPEND(to, from) \
 127         do { \
 128                 if (*to != '\0') \
 129                         strlcat(to, ",", maxlen); \
 130                 strlcat(to, from, maxlen); \
 131         } while (0)
 132
 133         while ((alg = strsep(&avail, ",")) && *alg != '\0') {
 134                 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
 135                         fatal("%s: unknown alg %s", __func__, alg);
 136                 if (lookup_key_in_hostkeys_by_type(hostkeys,
 137                     sshkey_type_plain(ktype), NULL))
 138                         ALG_APPEND(first, alg);
 139                 else
 140                         ALG_APPEND(last, alg);
 141         }
 142 #undef ALG_APPEND
 143         xasprintf(&ret, "%s%s%s", first,
 144             (*first == '\0' || *last == '\0') ? "" : ",", last);
 145         if (*first != '\0')
 146                 debug3("%s: prefer hostkeyalgs: %s", __func__, first);
 147
 148         free(first);
 149         free(last);
 150         free(hostname);
 151         free(oavail);
 152         free_hostkeys(hostkeys);
 153
 154         return ret;
 155 }
 156
 157 void
 158 ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 159 {
 160         char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
 161         char *s;
 162         struct kex *kex;
 163         int r;
 164
 165         xxx_host = host;
 166         xxx_hostaddr = hostaddr;
 167
 168         if ((s = kex_names_cat(options.kex_algorithms, "ext-info-c")) == NULL)
 169                 fatal("%s: kex_names_cat", __func__);
 170         myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(s);
 171         myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 172             compat_cipher_proposal(options.ciphers);
 173         myproposal[PROPOSAL_ENC_ALGS_STOC] =
 174             compat_cipher_proposal(options.ciphers);
 175         myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 176             myproposal[PROPOSAL_COMP_ALGS_STOC] = options.compression ?
 177             "zlib@openssh.com,zlib,none" : "none,zlib@openssh.com,zlib";
 178         myproposal[PROPOSAL_MAC_ALGS_CTOS] =
 179             myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
 180         if (options.hostkeyalgorithms != NULL) {
 181                 if (kex_assemble_names(KEX_DEFAULT_PK_ALG,
 182                     &options.hostkeyalgorithms) != 0)
 183                         fatal("%s: kex_assemble_namelist", __func__);
 184                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 185                     compat_pkalg_proposal(options.hostkeyalgorithms);
 186         } else {
 187                 /* Enforce default */
 188                 options.hostkeyalgorithms = xstrdup(KEX_DEFAULT_PK_ALG);
 189                 /* Prefer algorithms that we already have keys for */
 190                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 191                     compat_pkalg_proposal(
 192                     order_hostkeyalgs(host, hostaddr, port));
 193         }
 194
 195         if (options.rekey_limit || options.rekey_interval)
 196                 packet_set_rekey_limits((u_int32_t)options.rekey_limit,
 197                     (time_t)options.rekey_interval);
 198
 199         /* start key exchange */
 200         if ((r = kex_setup(active_state, myproposal)) != 0)
 201                 fatal("kex_setup: %s", ssh_err(r));
 202         kex = active_state->kex;
 203 #ifdef WITH_OPENSSL
 204         kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 205         kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
 206         kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client;
 207         kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client;
 208         kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client;
 209         kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
 210         kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 211 # ifdef OPENSSL_HAS_ECC
 212         kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
 213 # endif
 214 #endif
 215         kex->kex[KEX_C25519_SHA256] = kexc25519_client;
 216         kex->client_version_string=client_version_string;
 217         kex->server_version_string=server_version_string;
 218         kex->verify_host_key=&verify_host_key_callback;
 219
 220         dispatch_run(DISPATCH_BLOCK, &kex->done, active_state);
 221
 222         /* remove ext-info from the KEX proposals for rekeying */
 223         myproposal[PROPOSAL_KEX_ALGS] =
 224             compat_kex_proposal(options.kex_algorithms);
 225         if ((r = kex_prop2buf(kex->my, myproposal)) != 0)
 226                 fatal("kex_prop2buf: %s", ssh_err(r));
 227
 228         session_id2 = kex->session_id;
 229         session_id2_len = kex->session_id_len;
 230
 231 #ifdef DEBUG_KEXDH
 232         /* send 1st encrypted/maced/compressed message */
 233         packet_start(SSH2_MSG_IGNORE);
 234         packet_put_cstring("markus");
 235         packet_send();
 236         packet_write_wait();
 237 #endif
 238 }
 239
 240 /*
 241  * Authenticate user
 242  */
 243
 244 typedef struct cauthctxt Authctxt;
 245 typedef struct cauthmethod Authmethod;
 246 typedef struct identity Identity;
 247 typedef struct idlist Idlist;
 248
 249 struct identity {
 250         TAILQ_ENTRY(identity) next;
 251         int     agent_fd;               /* >=0 if agent supports key */
 252         struct sshkey   *key;           /* public/private key */
 253         char    *filename;              /* comment for agent-only keys */
 254         int     tried;
 255         int     isprivate;              /* key points to the private key */
 256         int     userprovided;
 257 };
 258 TAILQ_HEAD(idlist, identity);
 259
 260 struct cauthctxt {
 261         const char *server_user;
 262         const char *local_user;
 263         const char *host;
 264         const char *service;
 265         struct cauthmethod *method;
 266         sig_atomic_t success;
 267         char *authlist;
 268         int attempt;
 269         /* pubkey */
 270         struct idlist keys;
 271         int agent_fd;
 272         /* hostbased */
 273         Sensitive *sensitive;
 274         char *oktypes, *ktypes;
 275         const char *active_ktype;
 276         /* kbd-interactive */
 277         int info_req_seen;
 278         /* generic */
 279         void *methoddata;
 280 };
 281
 282 struct cauthmethod {
 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 int     input_userauth_service_accept(int, u_int32_t, void *);
 291 int     input_userauth_ext_info(int, u_int32_t, void *);
 292 int     input_userauth_success(int, u_int32_t, void *);
 293 int     input_userauth_success_unexpected(int, u_int32_t, void *);
 294 int     input_userauth_failure(int, u_int32_t, void *);
 295 int     input_userauth_banner(int, u_int32_t, void *);
 296 int     input_userauth_error(int, u_int32_t, void *);
 297 int     input_userauth_info_req(int, u_int32_t, void *);
 298 int     input_userauth_pk_ok(int, u_int32_t, void *);
 299 int     input_userauth_passwd_changereq(int, u_int32_t, void *);
 300
 301 int     userauth_none(Authctxt *);
 302 int     userauth_pubkey(Authctxt *);
 303 int     userauth_passwd(Authctxt *);
 304 int     userauth_kbdint(Authctxt *);
 305 int     userauth_hostbased(Authctxt *);
 306
 307 #ifdef GSSAPI
 308 int     userauth_gssapi(Authctxt *authctxt);
 309 int     input_gssapi_response(int type, u_int32_t, void *);
 310 int     input_gssapi_token(int type, u_int32_t, void *);
 311 int     input_gssapi_hash(int type, u_int32_t, void *);
 312 int     input_gssapi_error(int, u_int32_t, void *);
 313 int     input_gssapi_errtok(int, u_int32_t, void *);
 314 #endif
 315
 316 void    userauth(Authctxt *, char *);
 317
 318 static int sign_and_send_pubkey(Authctxt *, Identity *);
 319 static void pubkey_prepare(Authctxt *);
 320 static void pubkey_cleanup(Authctxt *);
 321 static Key *load_identity_file(Identity *);
 322
 323 static Authmethod *authmethod_get(char *authlist);
 324 static Authmethod *authmethod_lookup(const char *name);
 325 static char *authmethods_get(void);
 326
 327 Authmethod authmethods[] = {
 328 #ifdef GSSAPI
 329         {"gssapi-with-mic",
 330                 userauth_gssapi,
 331                 NULL,
 332                 &options.gss_authentication,
 333                 NULL},
 334 #endif
 335         {"hostbased",
 336                 userauth_hostbased,
 337                 NULL,
 338                 &options.hostbased_authentication,
 339                 NULL},
 340         {"publickey",
 341                 userauth_pubkey,
 342                 NULL,
 343                 &options.pubkey_authentication,
 344                 NULL},
 345         {"keyboard-interactive",
 346                 userauth_kbdint,
 347                 NULL,
 348                 &options.kbd_interactive_authentication,
 349                 &options.batch_mode},
 350         {"password",
 351                 userauth_passwd,
 352                 NULL,
 353                 &options.password_authentication,
 354                 &options.batch_mode},
 355         {"none",
 356                 userauth_none,
 357                 NULL,
 358                 NULL,
 359                 NULL},
 360         {NULL, NULL, NULL, NULL, NULL}
 361 };
 362
 363 void
 364 ssh_userauth2(const char *local_user, const char *server_user, char *host,
 365     Sensitive *sensitive)
 366 {
 367         struct ssh *ssh = active_state;
 368         Authctxt authctxt;
 369         int r;
 370
 371         if (options.challenge_response_authentication)
 372                 options.kbd_interactive_authentication = 1;
 373         if (options.preferred_authentications == NULL)
 374                 options.preferred_authentications = authmethods_get();
 375
 376         /* setup authentication context */
 377         memset(&authctxt, 0, sizeof(authctxt));
 378         pubkey_prepare(&authctxt);
 379         authctxt.server_user = server_user;
 380         authctxt.local_user = local_user;
 381         authctxt.host = host;
 382         authctxt.service = "ssh-connection";            /* service name */
 383         authctxt.success = 0;
 384         authctxt.method = authmethod_lookup("none");
 385         authctxt.authlist = NULL;
 386         authctxt.methoddata = NULL;
 387         authctxt.sensitive = sensitive;
 388         authctxt.active_ktype = authctxt.oktypes = authctxt.ktypes = NULL;
 389         authctxt.info_req_seen = 0;
 390         authctxt.agent_fd = -1;
 391         if (authctxt.method == NULL)
 392                 fatal("ssh_userauth2: internal error: cannot send userauth none request");
 393
 394         if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_REQUEST)) != 0 ||
 395             (r = sshpkt_put_cstring(ssh, "ssh-userauth")) != 0 ||
 396             (r = sshpkt_send(ssh)) != 0)
 397                 fatal("%s: %s", __func__, ssh_err(r));
 398
 399         ssh_dispatch_init(ssh, &input_userauth_error);
 400         ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &input_userauth_ext_info);
 401         ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_ACCEPT, &input_userauth_service_accept);
 402         ssh_dispatch_run(ssh, DISPATCH_BLOCK, &authctxt.success, &authctxt);    /* loop until success */
 403
 404         pubkey_cleanup(&authctxt);
 405         ssh_dispatch_range(ssh, SSH2_MSG_USERAUTH_MIN, SSH2_MSG_USERAUTH_MAX, NULL);
 406
 407         debug("Authentication succeeded (%s).", authctxt.method->name);
 408 }
 409
 410 /* ARGSUSED */
 411 int
 412 input_userauth_service_accept(int type, u_int32_t seqnr, void *ctxt)
 413 {
 414         Authctxt *authctxt = ctxt;
 415         struct ssh *ssh = active_state;
 416         int r;
 417
 418         if (ssh_packet_remaining(ssh) > 0) {
 419                 char *reply;
 420
 421                 if ((r = sshpkt_get_cstring(ssh, &reply, NULL)) != 0)
 422                         goto out;
 423                 debug2("service_accept: %s", reply);
 424                 free(reply);
 425         } else {
 426                 debug2("buggy server: service_accept w/o service");
 427         }
 428         if ((r = sshpkt_get_end(ssh)) != 0)
 429                 goto out;
 430         debug("SSH2_MSG_SERVICE_ACCEPT received");
 431
 432         /* initial userauth request */
 433         userauth_none(authctxt);
 434
 435         ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &input_userauth_error);
 436         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
 437         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
 438         ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
 439         r = 0;
 440  out:
 441         return r;
 442 }
 443
 444 /* ARGSUSED */
 445 int
 446 input_userauth_ext_info(int type, u_int32_t seqnr, void *ctxt)
 447 {
 448         return kex_input_ext_info(type, seqnr, active_state);
 449 }
 450
 451 void
 452 userauth(Authctxt *authctxt, char *authlist)
 453 {
 454         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 455                 authctxt->method->cleanup(authctxt);
 456
 457         free(authctxt->methoddata);
 458         authctxt->methoddata = NULL;
 459         if (authlist == NULL) {
 460                 authlist = authctxt->authlist;
 461         } else {
 462                 free(authctxt->authlist);
 463                 authctxt->authlist = authlist;
 464         }
 465         for (;;) {
 466                 Authmethod *method = authmethod_get(authlist);
 467                 if (method == NULL)
 468                         fatal("Permission denied (%s).", authlist);
 469                 authctxt->method = method;
 470
 471                 /* reset the per method handler */
 472                 dispatch_range(SSH2_MSG_USERAUTH_PER_METHOD_MIN,
 473                     SSH2_MSG_USERAUTH_PER_METHOD_MAX, NULL);
 474
 475                 /* and try new method */
 476                 if (method->userauth(authctxt) != 0) {
 477                         debug2("we sent a %s packet, wait for reply", method->name);
 478                         break;
 479                 } else {
 480                         debug2("we did not send a packet, disable method");
 481                         method->enabled = NULL;
 482                 }
 483         }
 484 }
 485
 486 /* ARGSUSED */
 487 int
 488 input_userauth_error(int type, u_int32_t seq, void *ctxt)
 489 {
 490         fatal("input_userauth_error: bad message during authentication: "
 491             "type %d", type);
 492         return 0;
 493 }
 494
 495 /* ARGSUSED */
 496 int
 497 input_userauth_banner(int type, u_int32_t seq, void *ctxt)
 498 {
 499         char *msg, *lang;
 500         u_int len;
 501
 502         debug3("%s", __func__);
 503         msg = packet_get_string(&len);
 504         lang = packet_get_string(NULL);
 505         if (len > 0 && options.log_level >= SYSLOG_LEVEL_INFO)
 506                 fmprintf(stderr, "%s", msg);
 507         free(msg);
 508         free(lang);
 509         return 0;
 510 }
 511
 512 /* ARGSUSED */
 513 int
 514 input_userauth_success(int type, u_int32_t seq, void *ctxt)
 515 {
 516         Authctxt *authctxt = ctxt;
 517
 518         if (authctxt == NULL)
 519                 fatal("input_userauth_success: no authentication context");
 520         free(authctxt->authlist);
 521         authctxt->authlist = NULL;
 522         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 523                 authctxt->method->cleanup(authctxt);
 524         free(authctxt->methoddata);
 525         authctxt->methoddata = NULL;
 526         authctxt->success = 1;                  /* break out */
 527         return 0;
 528 }
 529
 530 int
 531 input_userauth_success_unexpected(int type, u_int32_t seq, void *ctxt)
 532 {
 533         Authctxt *authctxt = ctxt;
 534
 535         if (authctxt == NULL)
 536                 fatal("%s: no authentication context", __func__);
 537
 538         fatal("Unexpected authentication success during %s.",
 539             authctxt->method->name);
 540         return 0;
 541 }
 542
 543 /* ARGSUSED */
 544 int
 545 input_userauth_failure(int type, u_int32_t seq, void *ctxt)
 546 {
 547         Authctxt *authctxt = ctxt;
 548         char *authlist = NULL;
 549         int partial;
 550
 551         if (authctxt == NULL)
 552                 fatal("input_userauth_failure: no authentication context");
 553
 554         authlist = packet_get_string(NULL);
 555         partial = packet_get_char();
 556         packet_check_eom();
 557
 558         if (partial != 0) {
 559                 verbose("Authenticated with partial success.");
 560                 /* reset state */
 561                 pubkey_cleanup(authctxt);
 562                 pubkey_prepare(authctxt);
 563         }
 564         debug("Authentications that can continue: %s", authlist);
 565
 566         userauth(authctxt, authlist);
 567         return 0;
 568 }
 569
 570 /* ARGSUSED */
 571 int
 572 input_userauth_pk_ok(int type, u_int32_t seq, void *ctxt)
 573 {
 574         Authctxt *authctxt = ctxt;
 575         Key *key = NULL;
 576         Identity *id = NULL;
 577         Buffer b;
 578         int pktype, sent = 0;
 579         u_int alen, blen;
 580         char *pkalg, *fp;
 581         u_char *pkblob;
 582
 583         if (authctxt == NULL)
 584                 fatal("input_userauth_pk_ok: no authentication context");
 585         if (datafellows & SSH_BUG_PKOK) {
 586                 /* this is similar to SSH_BUG_PKAUTH */
 587                 debug2("input_userauth_pk_ok: SSH_BUG_PKOK");
 588                 pkblob = packet_get_string(&blen);
 589                 buffer_init(&b);
 590                 buffer_append(&b, pkblob, blen);
 591                 pkalg = buffer_get_string(&b, &alen);
 592                 buffer_free(&b);
 593         } else {
 594                 pkalg = packet_get_string(&alen);
 595                 pkblob = packet_get_string(&blen);
 596         }
 597         packet_check_eom();
 598
 599         debug("Server accepts key: pkalg %s blen %u", pkalg, blen);
 600
 601         if ((pktype = key_type_from_name(pkalg)) == KEY_UNSPEC) {
 602                 debug("unknown pkalg %s", pkalg);
 603                 goto done;
 604         }
 605         if ((key = key_from_blob(pkblob, blen)) == NULL) {
 606                 debug("no key from blob. pkalg %s", pkalg);
 607                 goto done;
 608         }
 609         if (key->type != pktype) {
 610                 error("input_userauth_pk_ok: type mismatch "
 611                     "for decoded key (received %d, expected %d)",
 612                     key->type, pktype);
 613                 goto done;
 614         }
 615         if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
 616             SSH_FP_DEFAULT)) == NULL)
 617                 goto done;
 618         debug2("input_userauth_pk_ok: fp %s", fp);
 619         free(fp);
 620
 621         /*
 622          * search keys in the reverse order, because last candidate has been
 623          * moved to the end of the queue.  this also avoids confusion by
 624          * duplicate keys
 625          */
 626         TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
 627                 if (key_equal(key, id->key)) {
 628                         sent = sign_and_send_pubkey(authctxt, id);
 629                         break;
 630                 }
 631         }
 632 done:
 633         if (key != NULL)
 634                 key_free(key);
 635         free(pkalg);
 636         free(pkblob);
 637
 638         /* try another method if we did not send a packet */
 639         if (sent == 0)
 640                 userauth(authctxt, NULL);
 641         return 0;
 642 }
 643
 644 #ifdef GSSAPI
 645 int
 646 userauth_gssapi(Authctxt *authctxt)
 647 {
 648         Gssctxt *gssctxt = NULL;
 649         static gss_OID_set gss_supported = NULL;
 650         static u_int mech = 0;
 651         OM_uint32 min;
 652         int ok = 0;
 653
 654         /* Try one GSSAPI method at a time, rather than sending them all at
 655          * once. */
 656
 657         if (gss_supported == NULL)
 658                 gss_indicate_mechs(&min, &gss_supported);
 659
 660         /* Check to see if the mechanism is usable before we offer it */
 661         while (mech < gss_supported->count && !ok) {
 662                 /* My DER encoding requires length<128 */
 663                 if (gss_supported->elements[mech].length < 128 &&
 664                     ssh_gssapi_check_mechanism(&gssctxt,
 665                     &gss_supported->elements[mech], authctxt->host)) {
 666                         ok = 1; /* Mechanism works */
 667                 } else {
 668                         mech++;
 669                 }
 670         }
 671
 672         if (!ok)
 673                 return 0;
 674
 675         authctxt->methoddata=(void *)gssctxt;
 676
 677         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 678         packet_put_cstring(authctxt->server_user);
 679         packet_put_cstring(authctxt->service);
 680         packet_put_cstring(authctxt->method->name);
 681
 682         packet_put_int(1);
 683
 684         packet_put_int((gss_supported->elements[mech].length) + 2);
 685         packet_put_char(SSH_GSS_OIDTYPE);
 686         packet_put_char(gss_supported->elements[mech].length);
 687         packet_put_raw(gss_supported->elements[mech].elements,
 688             gss_supported->elements[mech].length);
 689
 690         packet_send();
 691
 692         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
 693         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 694         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
 695         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 696
 697         mech++; /* Move along to next candidate */
 698
 699         return 1;
 700 }
 701
 702 static OM_uint32
 703 process_gssapi_token(void *ctxt, gss_buffer_t recv_tok)
 704 {
 705         Authctxt *authctxt = ctxt;
 706         Gssctxt *gssctxt = authctxt->methoddata;
 707         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 708         gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
 709         gss_buffer_desc gssbuf;
 710         OM_uint32 status, ms, flags;
 711         Buffer b;
 712
 713         status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 714             recv_tok, &send_tok, &flags);
 715
 716         if (send_tok.length > 0) {
 717                 if (GSS_ERROR(status))
 718                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 719                 else
 720                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 721
 722                 packet_put_string(send_tok.value, send_tok.length);
 723                 packet_send();
 724                 gss_release_buffer(&ms, &send_tok);
 725         }
 726
 727         if (status == GSS_S_COMPLETE) {
 728                 /* send either complete or MIC, depending on mechanism */
 729                 if (!(flags & GSS_C_INTEG_FLAG)) {
 730                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
 731                         packet_send();
 732                 } else {
 733                         ssh_gssapi_buildmic(&b, authctxt->server_user,
 734                             authctxt->service, "gssapi-with-mic");
 735
 736                         gssbuf.value = buffer_ptr(&b);
 737                         gssbuf.length = buffer_len(&b);
 738
 739                         status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);
 740
 741                         if (!GSS_ERROR(status)) {
 742                                 packet_start(SSH2_MSG_USERAUTH_GSSAPI_MIC);
 743                                 packet_put_string(mic.value, mic.length);
 744
 745                                 packet_send();
 746                         }
 747
 748                         buffer_free(&b);
 749                         gss_release_buffer(&ms, &mic);
 750                 }
 751         }
 752
 753         return status;
 754 }
 755
 756 /* ARGSUSED */
 757 int
 758 input_gssapi_response(int type, u_int32_t plen, void *ctxt)
 759 {
 760         Authctxt *authctxt = ctxt;
 761         Gssctxt *gssctxt;
 762         int oidlen;
 763         char *oidv;
 764
 765         if (authctxt == NULL)
 766                 fatal("input_gssapi_response: no authentication context");
 767         gssctxt = authctxt->methoddata;
 768
 769         /* Setup our OID */
 770         oidv = packet_get_string(&oidlen);
 771
 772         if (oidlen <= 2 ||
 773             oidv[0] != SSH_GSS_OIDTYPE ||
 774             oidv[1] != oidlen - 2) {
 775                 free(oidv);
 776                 debug("Badly encoded mechanism OID received");
 777                 userauth(authctxt, NULL);
 778                 return 0;
 779         }
 780
 781         if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
 782                 fatal("Server returned different OID than expected");
 783
 784         packet_check_eom();
 785
 786         free(oidv);
 787
 788         if (GSS_ERROR(process_gssapi_token(ctxt, GSS_C_NO_BUFFER))) {
 789                 /* Start again with next method on list */
 790                 debug("Trying to start again");
 791                 userauth(authctxt, NULL);
 792                 return 0;
 793         }
 794         return 0;
 795 }
 796
 797 /* ARGSUSED */
 798 int
 799 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 800 {
 801         Authctxt *authctxt = ctxt;
 802         gss_buffer_desc recv_tok;
 803         OM_uint32 status;
 804         u_int slen;
 805
 806         if (authctxt == NULL)
 807                 fatal("input_gssapi_response: no authentication context");
 808
 809         recv_tok.value = packet_get_string(&slen);
 810         recv_tok.length = slen; /* safe typecast */
 811
 812         packet_check_eom();
 813
 814         status = process_gssapi_token(ctxt, &recv_tok);
 815
 816         free(recv_tok.value);
 817
 818         if (GSS_ERROR(status)) {
 819                 /* Start again with the next method in the list */
 820                 userauth(authctxt, NULL);
 821                 return 0;
 822         }
 823         return 0;
 824 }
 825
 826 /* ARGSUSED */
 827 int
 828 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 829 {
 830         Authctxt *authctxt = ctxt;
 831         Gssctxt *gssctxt;
 832         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 833         gss_buffer_desc recv_tok;
 834         OM_uint32 ms;
 835         u_int len;
 836
 837         if (authctxt == NULL)
 838                 fatal("input_gssapi_response: no authentication context");
 839         gssctxt = authctxt->methoddata;
 840
 841         recv_tok.value = packet_get_string(&len);
 842         recv_tok.length = len;
 843
 844         packet_check_eom();
 845
 846         /* Stick it into GSSAPI and see what it says */
 847         (void)ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 848             &recv_tok, &send_tok, NULL);
 849
 850         free(recv_tok.value);
 851         gss_release_buffer(&ms, &send_tok);
 852
 853         /* Server will be returning a failed packet after this one */
 854         return 0;
 855 }
 856
 857 /* ARGSUSED */
 858 int
 859 input_gssapi_error(int type, u_int32_t plen, void *ctxt)
 860 {
 861         char *msg;
 862         char *lang;
 863
 864         /* maj */(void)packet_get_int();
 865         /* min */(void)packet_get_int();
 866         msg=packet_get_string(NULL);
 867         lang=packet_get_string(NULL);
 868
 869         packet_check_eom();
 870
 871         debug("Server GSSAPI Error:\n%s", msg);
 872         free(msg);
 873         free(lang);
 874         return 0;
 875 }
 876 #endif /* GSSAPI */
 877
 878 int
 879 userauth_none(Authctxt *authctxt)
 880 {
 881         /* initial userauth request */
 882         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 883         packet_put_cstring(authctxt->server_user);
 884         packet_put_cstring(authctxt->service);
 885         packet_put_cstring(authctxt->method->name);
 886         packet_send();
 887         return 1;
 888 }
 889
 890 int
 891 userauth_passwd(Authctxt *authctxt)
 892 {
 893         static int attempt = 0;
 894         char prompt[150];
 895         char *password;
 896         const char *host = options.host_key_alias ?  options.host_key_alias :
 897             authctxt->host;
 898
 899         if (attempt++ >= options.number_of_password_prompts)
 900                 return 0;
 901
 902         if (attempt != 1)
 903                 error("Permission denied, please try again.");
 904
 905         snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
 906             authctxt->server_user, host);
 907         password = read_passphrase(prompt, 0);
 908         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 909         packet_put_cstring(authctxt->server_user);
 910         packet_put_cstring(authctxt->service);
 911         packet_put_cstring(authctxt->method->name);
 912         packet_put_char(0);
 913         packet_put_cstring(password);
 914         explicit_bzero(password, strlen(password));
 915         free(password);
 916         packet_add_padding(64);
 917         packet_send();
 918
 919         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 920             &input_userauth_passwd_changereq);
 921
 922         return 1;
 923 }
 924
 925 /*
 926  * parse PASSWD_CHANGEREQ, prompt user and send SSH2_MSG_USERAUTH_REQUEST
 927  */
 928 /* ARGSUSED */
 929 int
 930 input_userauth_passwd_changereq(int type, u_int32_t seqnr, void *ctxt)
 931 {
 932         Authctxt *authctxt = ctxt;
 933         char *info, *lang, *password = NULL, *retype = NULL;
 934         char prompt[150];
 935         const char *host = options.host_key_alias ? options.host_key_alias :
 936             authctxt->host;
 937
 938         debug2("input_userauth_passwd_changereq");
 939
 940         if (authctxt == NULL)
 941                 fatal("input_userauth_passwd_changereq: "
 942                     "no authentication context");
 943
 944         info = packet_get_string(NULL);
 945         lang = packet_get_string(NULL);
 946         if (strlen(info) > 0)
 947                 logit("%s", info);
 948         free(info);
 949         free(lang);
 950         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 951         packet_put_cstring(authctxt->server_user);
 952         packet_put_cstring(authctxt->service);
 953         packet_put_cstring(authctxt->method->name);
 954         packet_put_char(1);                     /* additional info */
 955         snprintf(prompt, sizeof(prompt),
 956             "Enter %.30s@%.128s's old password: ",
 957             authctxt->server_user, host);
 958         password = read_passphrase(prompt, 0);
 959         packet_put_cstring(password);
 960         explicit_bzero(password, strlen(password));
 961         free(password);
 962         password = NULL;
 963         while (password == NULL) {
 964                 snprintf(prompt, sizeof(prompt),
 965                     "Enter %.30s@%.128s's new password: ",
 966                     authctxt->server_user, host);
 967                 password = read_passphrase(prompt, RP_ALLOW_EOF);
 968                 if (password == NULL) {
 969                         /* bail out */
 970                         return 0;
 971                 }
 972                 snprintf(prompt, sizeof(prompt),
 973                     "Retype %.30s@%.128s's new password: ",
 974                     authctxt->server_user, host);
 975                 retype = read_passphrase(prompt, 0);
 976                 if (strcmp(password, retype) != 0) {
 977                         explicit_bzero(password, strlen(password));
 978                         free(password);
 979                         logit("Mismatch; try again, EOF to quit.");
 980                         password = NULL;
 981                 }
 982                 explicit_bzero(retype, strlen(retype));
 983                 free(retype);
 984         }
 985         packet_put_cstring(password);
 986         explicit_bzero(password, strlen(password));
 987         free(password);
 988         packet_add_padding(64);
 989         packet_send();
 990
 991         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 992             &input_userauth_passwd_changereq);
 993         return 0;
 994 }
 995
 996 static const char *
 997 identity_sign_encode(struct identity *id)
 998 {
 999         struct ssh *ssh = active_state;
1000
1001         if (id->key->type == KEY_RSA) {
1002                 switch (ssh->kex->rsa_sha2) {
1003                 case 256:
1004                         return "rsa-sha2-256";
1005                 case 512:
1006                         return "rsa-sha2-512";
1007                 }
1008         }
1009         return key_ssh_name(id->key);
1010 }
1011
1012 static int
1013 identity_sign(struct identity *id, u_char **sigp, size_t *lenp,
1014     const u_char *data, size_t datalen, u_int compat)
1015 {
1016         Key *prv;
1017         int ret;
1018         const char *alg;
1019
1020         alg = identity_sign_encode(id);
1021
1022         /* the agent supports this key */
1023         if (id->agent_fd != -1)
1024                 return ssh_agent_sign(id->agent_fd, id->key, sigp, lenp,
1025                     data, datalen, alg, compat);
1026
1027         /*
1028          * we have already loaded the private key or
1029          * the private key is stored in external hardware
1030          */
1031         if (id->isprivate || (id->key->flags & SSHKEY_FLAG_EXT))
1032                 return (sshkey_sign(id->key, sigp, lenp, data, datalen, alg,
1033                     compat));
1034         /* load the private key from the file */
1035         if ((prv = load_identity_file(id)) == NULL)
1036                 return SSH_ERR_KEY_NOT_FOUND;
1037         ret = sshkey_sign(prv, sigp, lenp, data, datalen, alg, compat);
1038         sshkey_free(prv);
1039         return (ret);
1040 }
1041
1042 static int
1043 sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
1044 {
1045         Buffer b;
1046         Identity *private_id;
1047         u_char *blob, *signature;
1048         size_t slen;
1049         u_int bloblen, skip = 0;
1050         int matched, ret = -1, have_sig = 1;
1051         char *fp;
1052
1053         if ((fp = sshkey_fingerprint(id->key, options.fingerprint_hash,
1054             SSH_FP_DEFAULT)) == NULL)
1055                 return 0;
1056         debug3("%s: %s %s", __func__, key_type(id->key), fp);
1057         free(fp);
1058
1059         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1060                 /* we cannot handle this key */
1061                 debug3("sign_and_send_pubkey: cannot handle key");
1062                 return 0;
1063         }
1064         /* data to be signed */
1065         buffer_init(&b);
1066         if (datafellows & SSH_OLD_SESSIONID) {
1067                 buffer_append(&b, session_id2, session_id2_len);
1068                 skip = session_id2_len;
1069         } else {
1070                 buffer_put_string(&b, session_id2, session_id2_len);
1071                 skip = buffer_len(&b);
1072         }
1073         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1074         buffer_put_cstring(&b, authctxt->server_user);
1075         buffer_put_cstring(&b,
1076             datafellows & SSH_BUG_PKSERVICE ?
1077             "ssh-userauth" :
1078             authctxt->service);
1079         if (datafellows & SSH_BUG_PKAUTH) {
1080                 buffer_put_char(&b, have_sig);
1081         } else {
1082                 buffer_put_cstring(&b, authctxt->method->name);
1083                 buffer_put_char(&b, have_sig);
1084                 buffer_put_cstring(&b, identity_sign_encode(id));
1085         }
1086         buffer_put_string(&b, blob, bloblen);
1087
1088         /*
1089          * If the key is an certificate, try to find a matching private key
1090          * and use it to complete the signature.
1091          * If no such private key exists, fall back to trying the certificate
1092          * key itself in case it has a private half already loaded.
1093          */
1094         if (key_is_cert(id->key)) {
1095                 matched = 0;
1096                 TAILQ_FOREACH(private_id, &authctxt->keys, next) {
1097                         if (sshkey_equal_public(id->key, private_id->key) &&
1098                             id->key->type != private_id->key->type) {
1099                                 id = private_id;
1100                                 matched = 1;
1101                                 break;
1102                         }
1103                 }
1104                 if (matched) {
1105                         debug2("%s: using private key \"%s\"%s for "
1106                             "certificate", __func__, id->filename,
1107                             id->agent_fd != -1 ? " from agent" : "");
1108                 } else {
1109                         debug("%s: no separate private key for certificate "
1110                             "\"%s\"", __func__, id->filename);
1111                 }
1112         }
1113
1114         /* generate signature */
1115         ret = identity_sign(id, &signature, &slen,
1116             buffer_ptr(&b), buffer_len(&b), datafellows);
1117         if (ret != 0) {
1118                 if (ret != SSH_ERR_KEY_NOT_FOUND)
1119                         error("%s: signing failed: %s", __func__, ssh_err(ret));
1120                 free(blob);
1121                 buffer_free(&b);
1122                 return 0;
1123         }
1124 #ifdef DEBUG_PK
1125         buffer_dump(&b);
1126 #endif
1127         if (datafellows & SSH_BUG_PKSERVICE) {
1128                 buffer_clear(&b);
1129                 buffer_append(&b, session_id2, session_id2_len);
1130                 skip = session_id2_len;
1131                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1132                 buffer_put_cstring(&b, authctxt->server_user);
1133                 buffer_put_cstring(&b, authctxt->service);
1134                 buffer_put_cstring(&b, authctxt->method->name);
1135                 buffer_put_char(&b, have_sig);
1136                 if (!(datafellows & SSH_BUG_PKAUTH))
1137                         buffer_put_cstring(&b, key_ssh_name(id->key));
1138                 buffer_put_string(&b, blob, bloblen);
1139         }
1140         free(blob);
1141
1142         /* append signature */
1143         buffer_put_string(&b, signature, slen);
1144         free(signature);
1145
1146         /* skip session id and packet type */
1147         if (buffer_len(&b) < skip + 1)
1148                 fatal("userauth_pubkey: internal error");
1149         buffer_consume(&b, skip + 1);
1150
1151         /* put remaining data from buffer into packet */
1152         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1153         packet_put_raw(buffer_ptr(&b), buffer_len(&b));
1154         buffer_free(&b);
1155         packet_send();
1156
1157         return 1;
1158 }
1159
1160 static int
1161 send_pubkey_test(Authctxt *authctxt, Identity *id)
1162 {
1163         u_char *blob;
1164         u_int bloblen, have_sig = 0;
1165
1166         debug3("send_pubkey_test");
1167
1168         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1169                 /* we cannot handle this key */
1170                 debug3("send_pubkey_test: cannot handle key");
1171                 return 0;
1172         }
1173         /* register callback for USERAUTH_PK_OK message */
1174         dispatch_set(SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
1175
1176         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1177         packet_put_cstring(authctxt->server_user);
1178         packet_put_cstring(authctxt->service);
1179         packet_put_cstring(authctxt->method->name);
1180         packet_put_char(have_sig);
1181         if (!(datafellows & SSH_BUG_PKAUTH))
1182                 packet_put_cstring(identity_sign_encode(id));
1183         packet_put_string(blob, bloblen);
1184         free(blob);
1185         packet_send();
1186         return 1;
1187 }
1188
1189 static Key *
1190 load_identity_file(Identity *id)
1191 {
1192         Key *private = NULL;
1193         char prompt[300], *passphrase, *comment;
1194         int r, perm_ok = 0, quit = 0, i;
1195         struct stat st;
1196
1197         if (stat(id->filename, &st) < 0) {
1198                 (id->userprovided ? logit : debug3)("no such identity: %s: %s",
1199                     id->filename, strerror(errno));
1200                 return NULL;
1201         }
1202         snprintf(prompt, sizeof prompt,
1203             "Enter passphrase for key '%.100s': ", id->filename);
1204         for (i = 0; i <= options.number_of_password_prompts; i++) {
1205                 if (i == 0)
1206                         passphrase = "";
1207                 else {
1208                         passphrase = read_passphrase(prompt, 0);
1209                         if (*passphrase == '\0') {
1210                                 debug2("no passphrase given, try next key");
1211                                 free(passphrase);
1212                                 break;
1213                         }
1214                 }
1215                 switch ((r = sshkey_load_private_type(KEY_UNSPEC, id->filename,
1216                     passphrase, &private, &comment, &perm_ok))) {
1217                 case 0:
1218                         break;
1219                 case SSH_ERR_KEY_WRONG_PASSPHRASE:
1220                         if (options.batch_mode) {
1221                                 quit = 1;
1222                                 break;
1223                         }
1224                         if (i != 0)
1225                                 debug2("bad passphrase given, try again...");
1226                         break;
1227                 case SSH_ERR_SYSTEM_ERROR:
1228                         if (errno == ENOENT) {
1229                                 debug2("Load key \"%s\": %s",
1230                                     id->filename, ssh_err(r));
1231                                 quit = 1;
1232                                 break;
1233                         }
1234                         /* FALLTHROUGH */
1235                 default:
1236                         error("Load key \"%s\": %s", id->filename, ssh_err(r));
1237                         quit = 1;
1238                         break;
1239                 }
1240                 if (!quit && private != NULL && id->agent_fd == -1 &&
1241                     !(id->key && id->isprivate))
1242                         maybe_add_key_to_agent(id->filename, private, comment,
1243                             passphrase);
1244                 if (i > 0) {
1245                         explicit_bzero(passphrase, strlen(passphrase));
1246                         free(passphrase);
1247                 }
1248                 free(comment);
1249                 if (private != NULL || quit)
1250                         break;
1251         }
1252         return private;
1253 }
1254
1255 /*
1256  * try keys in the following order:
1257  *      1. certificates listed in the config file
1258  *      2. other input certificates
1259  *      3. agent keys that are found in the config file
1260  *      4. other agent keys
1261  *      5. keys that are only listed in the config file
1262  */
1263 static void
1264 pubkey_prepare(Authctxt *authctxt)
1265 {
1266         struct identity *id, *id2, *tmp;
1267         struct idlist agent, files, *preferred;
1268         struct sshkey *key;
1269         int agent_fd = -1, i, r, found;
1270         size_t j;
1271         struct ssh_identitylist *idlist;
1272
1273         TAILQ_INIT(&agent);     /* keys from the agent */
1274         TAILQ_INIT(&files);     /* keys from the config file */
1275         preferred = &authctxt->keys;
1276         TAILQ_INIT(preferred);  /* preferred order of keys */
1277
1278         /* list of keys stored in the filesystem and PKCS#11 */
1279         for (i = 0; i < options.num_identity_files; i++) {
1280                 key = options.identity_keys[i];
1281                 if (key && key->type == KEY_RSA1)
1282                         continue;
1283                 if (key && key->cert && key->cert->type != SSH2_CERT_TYPE_USER)
1284                         continue;
1285                 options.identity_keys[i] = NULL;
1286                 id = xcalloc(1, sizeof(*id));
1287                 id->agent_fd = -1;
1288                 id->key = key;
1289                 id->filename = xstrdup(options.identity_files[i]);
1290                 id->userprovided = options.identity_file_userprovided[i];
1291                 TAILQ_INSERT_TAIL(&files, id, next);
1292         }
1293         /* list of certificates specified by user */
1294         for (i = 0; i < options.num_certificate_files; i++) {
1295                 key = options.certificates[i];
1296                 if (!key_is_cert(key) || key->cert == NULL ||
1297                     key->cert->type != SSH2_CERT_TYPE_USER)
1298                         continue;
1299                 id = xcalloc(1, sizeof(*id));
1300                 id->agent_fd = -1;
1301                 id->key = key;
1302                 id->filename = xstrdup(options.certificate_files[i]);
1303                 id->userprovided = options.certificate_file_userprovided[i];
1304                 TAILQ_INSERT_TAIL(preferred, id, next);
1305         }
1306         /* list of keys supported by the agent */
1307         if ((r = ssh_get_authentication_socket(&agent_fd)) != 0) {
1308                 if (r != SSH_ERR_AGENT_NOT_PRESENT)
1309                         debug("%s: ssh_get_authentication_socket: %s",
1310                             __func__, ssh_err(r));
1311         } else if ((r = ssh_fetch_identitylist(agent_fd, 2, &idlist)) != 0) {
1312                 if (r != SSH_ERR_AGENT_NO_IDENTITIES)
1313                         debug("%s: ssh_fetch_identitylist: %s",
1314                             __func__, ssh_err(r));
1315                 close(agent_fd);
1316         } else {
1317                 for (j = 0; j < idlist->nkeys; j++) {
1318                         found = 0;
1319                         TAILQ_FOREACH(id, &files, next) {
1320                                 /*
1321                                  * agent keys from the config file are
1322                                  * preferred
1323                                  */
1324                                 if (sshkey_equal(idlist->keys[j], id->key)) {
1325                                         TAILQ_REMOVE(&files, id, next);
1326                                         TAILQ_INSERT_TAIL(preferred, id, next);
1327                                         id->agent_fd = agent_fd;
1328                                         found = 1;
1329                                         break;
1330                                 }
1331                         }
1332                         if (!found && !options.identities_only) {
1333                                 id = xcalloc(1, sizeof(*id));
1334                                 /* XXX "steals" key/comment from idlist */
1335                                 id->key = idlist->keys[j];
1336                                 id->filename = idlist->comments[j];
1337                                 idlist->keys[j] = NULL;
1338                                 idlist->comments[j] = NULL;
1339                                 id->agent_fd = agent_fd;
1340                                 TAILQ_INSERT_TAIL(&agent, id, next);
1341                         }
1342                 }
1343                 ssh_free_identitylist(idlist);
1344                 /* append remaining agent keys */
1345                 for (id = TAILQ_FIRST(&agent); id; id = TAILQ_FIRST(&agent)) {
1346                         TAILQ_REMOVE(&agent, id, next);
1347                         TAILQ_INSERT_TAIL(preferred, id, next);
1348                 }
1349                 authctxt->agent_fd = agent_fd;
1350         }
1351         /* Prefer PKCS11 keys that are explicitly listed */
1352         TAILQ_FOREACH_SAFE(id, &files, next, tmp) {
1353                 if (id->key == NULL || (id->key->flags & SSHKEY_FLAG_EXT) == 0)
1354                         continue;
1355                 found = 0;
1356                 TAILQ_FOREACH(id2, &files, next) {
1357                         if (id2->key == NULL ||
1358                             (id2->key->flags & SSHKEY_FLAG_EXT) == 0)
1359                                 continue;
1360                         if (sshkey_equal(id->key, id2->key)) {
1361                                 TAILQ_REMOVE(&files, id, next);
1362                                 TAILQ_INSERT_TAIL(preferred, id, next);
1363                                 found = 1;
1364                                 break;
1365                         }
1366                 }
1367                 /* If IdentitiesOnly set and key not found then don't use it */
1368                 if (!found && options.identities_only) {
1369                         TAILQ_REMOVE(&files, id, next);
1370                         explicit_bzero(id, sizeof(*id));
1371                         free(id);
1372                 }
1373         }
1374         /* append remaining keys from the config file */
1375         for (id = TAILQ_FIRST(&files); id; id = TAILQ_FIRST(&files)) {
1376                 TAILQ_REMOVE(&files, id, next);
1377                 TAILQ_INSERT_TAIL(preferred, id, next);
1378         }
1379         /* finally, filter by PubkeyAcceptedKeyTypes */
1380         TAILQ_FOREACH_SAFE(id, preferred, next, id2) {
1381                 if (id->key != NULL &&
1382                     match_pattern_list(sshkey_ssh_name(id->key),
1383                     options.pubkey_key_types, 0) != 1) {
1384                         debug("Skipping %s key %s - "
1385                             "not in PubkeyAcceptedKeyTypes",
1386                             sshkey_ssh_name(id->key), id->filename);
1387                         TAILQ_REMOVE(preferred, id, next);
1388                         sshkey_free(id->key);
1389                         free(id->filename);
1390                         memset(id, 0, sizeof(*id));
1391                         continue;
1392                 }
1393                 debug2("key: %s (%p)%s%s", id->filename, id->key,
1394                     id->userprovided ? ", explicit" : "",
1395                     id->agent_fd != -1 ? ", agent" : "");
1396         }
1397 }
1398
1399 static void
1400 pubkey_cleanup(Authctxt *authctxt)
1401 {
1402         Identity *id;
1403
1404         if (authctxt->agent_fd != -1)
1405                 ssh_close_authentication_socket(authctxt->agent_fd);
1406         for (id = TAILQ_FIRST(&authctxt->keys); id;
1407             id = TAILQ_FIRST(&authctxt->keys)) {
1408                 TAILQ_REMOVE(&authctxt->keys, id, next);
1409                 sshkey_free(id->key);
1410                 free(id->filename);
1411                 free(id);
1412         }
1413 }
1414
1415 static int
1416 try_identity(Identity *id)
1417 {
1418         if (!id->key)
1419                 return (0);
1420         if (key_type_plain(id->key->type) == KEY_RSA &&
1421             (datafellows & SSH_BUG_RSASIGMD5) != 0) {
1422                 debug("Skipped %s key %s for RSA/MD5 server",
1423                     key_type(id->key), id->filename);
1424                 return (0);
1425         }
1426         return (id->key->type != KEY_RSA1);
1427 }
1428
1429 int
1430 userauth_pubkey(Authctxt *authctxt)
1431 {
1432         Identity *id;
1433         int sent = 0;
1434
1435         while ((id = TAILQ_FIRST(&authctxt->keys))) {
1436                 if (id->tried++)
1437                         return (0);
1438                 /* move key to the end of the queue */
1439                 TAILQ_REMOVE(&authctxt->keys, id, next);
1440                 TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
1441                 /*
1442                  * send a test message if we have the public key. for
1443                  * encrypted keys we cannot do this and have to load the
1444                  * private key instead
1445                  */
1446                 if (id->key != NULL) {
1447                         if (try_identity(id)) {
1448                                 debug("Offering %s public key: %s",
1449                                     key_type(id->key), id->filename);
1450                                 sent = send_pubkey_test(authctxt, id);
1451                         }
1452                 } else {
1453                         debug("Trying private key: %s", id->filename);
1454                         id->key = load_identity_file(id);
1455                         if (id->key != NULL) {
1456                                 if (try_identity(id)) {
1457                                         id->isprivate = 1;
1458                                         sent = sign_and_send_pubkey(
1459                                             authctxt, id);
1460                                 }
1461                                 key_free(id->key);
1462                                 id->key = NULL;
1463                         }
1464                 }
1465                 if (sent)
1466                         return (sent);
1467         }
1468         return (0);
1469 }
1470
1471 /*
1472  * Send userauth request message specifying keyboard-interactive method.
1473  */
1474 int
1475 userauth_kbdint(Authctxt *authctxt)
1476 {
1477         static int attempt = 0;
1478
1479         if (attempt++ >= options.number_of_password_prompts)
1480                 return 0;
1481         /* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
1482         if (attempt > 1 && !authctxt->info_req_seen) {
1483                 debug3("userauth_kbdint: disable: no info_req_seen");
1484                 dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
1485                 return 0;
1486         }
1487
1488         debug2("userauth_kbdint");
1489         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1490         packet_put_cstring(authctxt->server_user);
1491         packet_put_cstring(authctxt->service);
1492         packet_put_cstring(authctxt->method->name);
1493         packet_put_cstring("");                                 /* lang */
1494         packet_put_cstring(options.kbd_interactive_devices ?
1495             options.kbd_interactive_devices : "");
1496         packet_send();
1497
1498         dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
1499         return 1;
1500 }
1501
1502 /*
1503  * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
1504  */
1505 int
1506 input_userauth_info_req(int type, u_int32_t seq, void *ctxt)
1507 {
1508         Authctxt *authctxt = ctxt;
1509         char *name, *inst, *lang, *prompt, *response;
1510         u_int num_prompts, i;
1511         int echo = 0;
1512
1513         debug2("input_userauth_info_req");
1514
1515         if (authctxt == NULL)
1516                 fatal("input_userauth_info_req: no authentication context");
1517
1518         authctxt->info_req_seen = 1;
1519
1520         name = packet_get_string(NULL);
1521         inst = packet_get_string(NULL);
1522         lang = packet_get_string(NULL);
1523         if (strlen(name) > 0)
1524                 logit("%s", name);
1525         if (strlen(inst) > 0)
1526                 logit("%s", inst);
1527         free(name);
1528         free(inst);
1529         free(lang);
1530
1531         num_prompts = packet_get_int();
1532         /*
1533          * Begin to build info response packet based on prompts requested.
1534          * We commit to providing the correct number of responses, so if
1535          * further on we run into a problem that prevents this, we have to
1536          * be sure and clean this up and send a correct error response.
1537          */
1538         packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
1539         packet_put_int(num_prompts);
1540
1541         debug2("input_userauth_info_req: num_prompts %d", num_prompts);
1542         for (i = 0; i < num_prompts; i++) {
1543                 prompt = packet_get_string(NULL);
1544                 echo = packet_get_char();
1545
1546                 response = read_passphrase(prompt, echo ? RP_ECHO : 0);
1547
1548                 packet_put_cstring(response);
1549                 explicit_bzero(response, strlen(response));
1550                 free(response);
1551                 free(prompt);
1552         }
1553         packet_check_eom(); /* done with parsing incoming message. */
1554
1555         packet_add_padding(64);
1556         packet_send();
1557         return 0;
1558 }
1559
1560 static int
1561 ssh_keysign(struct sshkey *key, u_char **sigp, size_t *lenp,
1562     const u_char *data, size_t datalen)
1563 {
1564         struct sshbuf *b;
1565         struct stat st;
1566         pid_t pid;
1567         int i, r, to[2], from[2], status, sock = packet_get_connection_in();
1568         u_char rversion = 0, version = 2;
1569         void (*osigchld)(int);
1570
1571         *sigp = NULL;
1572         *lenp = 0;
1573
1574         if (stat(_PATH_SSH_KEY_SIGN, &st) < 0) {
1575                 error("%s: not installed: %s", __func__, strerror(errno));
1576                 return -1;
1577         }
1578         if (fflush(stdout) != 0) {
1579                 error("%s: fflush: %s", __func__, strerror(errno));
1580                 return -1;
1581         }
1582         if (pipe(to) < 0) {
1583                 error("%s: pipe: %s", __func__, strerror(errno));
1584                 return -1;
1585         }
1586         if (pipe(from) < 0) {
1587                 error("%s: pipe: %s", __func__, strerror(errno));
1588                 return -1;
1589         }
1590         if ((pid = fork()) < 0) {
1591                 error("%s: fork: %s", __func__, strerror(errno));
1592                 return -1;
1593         }
1594         osigchld = signal(SIGCHLD, SIG_DFL);
1595         if (pid == 0) {
1596                 /* keep the socket on exec */
1597                 fcntl(sock, F_SETFD, 0);
1598                 permanently_drop_suid(getuid());
1599                 close(from[0]);
1600                 if (dup2(from[1], STDOUT_FILENO) < 0)
1601                         fatal("%s: dup2: %s", __func__, strerror(errno));
1602                 close(to[1]);
1603                 if (dup2(to[0], STDIN_FILENO) < 0)
1604                         fatal("%s: dup2: %s", __func__, strerror(errno));
1605                 close(from[1]);
1606                 close(to[0]);
1607                 /* Close everything but stdio and the socket */
1608                 for (i = STDERR_FILENO + 1; i < sock; i++)
1609                         close(i);
1610                 closefrom(sock + 1);
1611                 debug3("%s: [child] pid=%ld, exec %s",
1612                     __func__, (long)getpid(), _PATH_SSH_KEY_SIGN);
1613                 execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *)NULL);
1614                 fatal("%s: exec(%s): %s", __func__, _PATH_SSH_KEY_SIGN,
1615                     strerror(errno));
1616         }
1617         close(from[1]);
1618         close(to[0]);
1619
1620         if ((b = sshbuf_new()) == NULL)
1621                 fatal("%s: sshbuf_new failed", __func__);
1622         /* send # of sock, data to be signed */
1623         if ((r = sshbuf_put_u32(b, sock) != 0) ||
1624             (r = sshbuf_put_string(b, data, datalen)) != 0)
1625                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
1626         if (ssh_msg_send(to[1], version, b) == -1)
1627                 fatal("%s: couldn't send request", __func__);
1628         sshbuf_reset(b);
1629         r = ssh_msg_recv(from[0], b);
1630         close(from[0]);
1631         close(to[1]);
1632         if (r < 0) {
1633                 error("%s: no reply", __func__);
1634                 goto fail;
1635         }
1636
1637         errno = 0;
1638         while (waitpid(pid, &status, 0) < 0) {
1639                 if (errno != EINTR) {
1640                         error("%s: waitpid %ld: %s",
1641                             __func__, (long)pid, strerror(errno));
1642                         goto fail;
1643                 }
1644         }
1645         if (!WIFEXITED(status)) {
1646                 error("%s: exited abnormally", __func__);
1647                 goto fail;
1648         }
1649         if (WEXITSTATUS(status) != 0) {
1650                 error("%s: exited with status %d",
1651                     __func__, WEXITSTATUS(status));
1652                 goto fail;
1653         }
1654         if ((r = sshbuf_get_u8(b, &rversion)) != 0) {
1655                 error("%s: buffer error: %s", __func__, ssh_err(r));
1656                 goto fail;
1657         }
1658         if (rversion != version) {
1659                 error("%s: bad version", __func__);
1660                 goto fail;
1661         }
1662         if ((r = sshbuf_get_string(b, sigp, lenp)) != 0) {
1663                 error("%s: buffer error: %s", __func__, ssh_err(r));
1664  fail:
1665                 signal(SIGCHLD, osigchld);
1666                 sshbuf_free(b);
1667                 return -1;
1668         }
1669         signal(SIGCHLD, osigchld);
1670         sshbuf_free(b);
1671
1672         return 0;
1673 }
1674
1675 int
1676 userauth_hostbased(Authctxt *authctxt)
1677 {
1678         struct ssh *ssh = active_state;
1679         struct sshkey *private = NULL;
1680         struct sshbuf *b = NULL;
1681         const char *service;
1682         u_char *sig = NULL, *keyblob = NULL;
1683         char *fp = NULL, *chost = NULL, *lname = NULL;
1684         size_t siglen = 0, keylen = 0;
1685         int i, r, success = 0;
1686
1687         if (authctxt->ktypes == NULL) {
1688                 authctxt->oktypes = xstrdup(options.hostbased_key_types);
1689                 authctxt->ktypes = authctxt->oktypes;
1690         }
1691
1692         /*
1693          * Work through each listed type pattern in HostbasedKeyTypes,
1694          * trying each hostkey that matches the type in turn.
1695          */
1696         for (;;) {
1697                 if (authctxt->active_ktype == NULL)
1698                         authctxt->active_ktype = strsep(&authctxt->ktypes, ",");
1699                 if (authctxt->active_ktype == NULL ||
1700                     *authctxt->active_ktype == '\0')
1701                         break;
1702                 debug3("%s: trying key type %s", __func__,
1703                     authctxt->active_ktype);
1704
1705                 /* check for a useful key */
1706                 private = NULL;
1707                 for (i = 0; i < authctxt->sensitive->nkeys; i++) {
1708                         if (authctxt->sensitive->keys[i] == NULL ||
1709                             authctxt->sensitive->keys[i]->type == KEY_RSA1 ||
1710                             authctxt->sensitive->keys[i]->type == KEY_UNSPEC)
1711                                 continue;
1712                         if (match_pattern_list(
1713                             sshkey_ssh_name(authctxt->sensitive->keys[i]),
1714                             authctxt->active_ktype, 0) != 1)
1715                                 continue;
1716                         /* we take and free the key */
1717                         private = authctxt->sensitive->keys[i];
1718                         authctxt->sensitive->keys[i] = NULL;
1719                         break;
1720                 }
1721                 /* Found one */
1722                 if (private != NULL)
1723                         break;
1724                 /* No more keys of this type; advance */
1725                 authctxt->active_ktype = NULL;
1726         }
1727         if (private == NULL) {
1728                 free(authctxt->oktypes);
1729                 authctxt->oktypes = authctxt->ktypes = NULL;
1730                 authctxt->active_ktype = NULL;
1731                 debug("No more client hostkeys for hostbased authentication.");
1732                 goto out;
1733         }
1734
1735         if ((fp = sshkey_fingerprint(private, options.fingerprint_hash,
1736             SSH_FP_DEFAULT)) == NULL) {
1737                 error("%s: sshkey_fingerprint failed", __func__);
1738                 goto out;
1739         }
1740         debug("%s: trying hostkey %s %s",
1741             __func__, sshkey_ssh_name(private), fp);
1742
1743         /* figure out a name for the client host */
1744         if ((lname = get_local_name(packet_get_connection_in())) == NULL) {
1745                 error("%s: cannot get local ipaddr/name", __func__);
1746                 goto out;
1747         }
1748
1749         /* XXX sshbuf_put_stringf? */
1750         xasprintf(&chost, "%s.", lname);
1751         debug2("%s: chost %s", __func__, chost);
1752
1753         service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
1754             authctxt->service;
1755
1756         /* construct data */
1757         if ((b = sshbuf_new()) == NULL) {
1758                 error("%s: sshbuf_new failed", __func__);
1759                 goto out;
1760         }
1761         if ((r = sshkey_to_blob(private, &keyblob, &keylen)) != 0) {
1762                 error("%s: sshkey_to_blob: %s", __func__, ssh_err(r));
1763                 goto out;
1764         }
1765         if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
1766             (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1767             (r = sshbuf_put_cstring(b, authctxt->server_user)) != 0 ||
1768             (r = sshbuf_put_cstring(b, service)) != 0 ||
1769             (r = sshbuf_put_cstring(b, authctxt->method->name)) != 0 ||
1770             (r = sshbuf_put_cstring(b, key_ssh_name(private))) != 0 ||
1771             (r = sshbuf_put_string(b, keyblob, keylen)) != 0 ||
1772             (r = sshbuf_put_cstring(b, chost)) != 0 ||
1773             (r = sshbuf_put_cstring(b, authctxt->local_user)) != 0) {
1774                 error("%s: buffer error: %s", __func__, ssh_err(r));
1775                 goto out;
1776         }
1777
1778 #ifdef DEBUG_PK
1779         sshbuf_dump(b, stderr);
1780 #endif
1781         if (authctxt->sensitive->external_keysign)
1782                 r = ssh_keysign(private, &sig, &siglen,
1783                     sshbuf_ptr(b), sshbuf_len(b));
1784         else if ((r = sshkey_sign(private, &sig, &siglen,
1785             sshbuf_ptr(b), sshbuf_len(b), NULL, datafellows)) != 0)
1786                 debug("%s: sshkey_sign: %s", __func__, ssh_err(r));
1787         if (r != 0) {
1788                 error("sign using hostkey %s %s failed",
1789                     sshkey_ssh_name(private), fp);
1790                 goto out;
1791         }
1792         if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1793             (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
1794             (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
1795             (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
1796             (r = sshpkt_put_cstring(ssh, key_ssh_name(private))) != 0 ||
1797             (r = sshpkt_put_string(ssh, keyblob, keylen)) != 0 ||
1798             (r = sshpkt_put_cstring(ssh, chost)) != 0 ||
1799             (r = sshpkt_put_cstring(ssh, authctxt->local_user)) != 0 ||
1800             (r = sshpkt_put_string(ssh, sig, siglen)) != 0 ||
1801             (r = sshpkt_send(ssh)) != 0) {
1802                 error("%s: packet error: %s", __func__, ssh_err(r));
1803                 goto out;
1804         }
1805         success = 1;
1806
1807  out:
1808         if (sig != NULL) {
1809                 explicit_bzero(sig, siglen);
1810                 free(sig);
1811         }
1812         free(keyblob);
1813         free(lname);
1814         free(fp);
1815         free(chost);
1816         sshkey_free(private);
1817         sshbuf_free(b);
1818
1819         return success;
1820 }
1821
1822 /* find auth method */
1823
1824 /*
1825  * given auth method name, if configurable options permit this method fill
1826  * in auth_ident field and return true, otherwise return false.
1827  */
1828 static int
1829 authmethod_is_enabled(Authmethod *method)
1830 {
1831         if (method == NULL)
1832                 return 0;
1833         /* return false if options indicate this method is disabled */
1834         if  (method->enabled == NULL || *method->enabled == 0)
1835                 return 0;
1836         /* return false if batch mode is enabled but method needs interactive mode */
1837         if  (method->batch_flag != NULL && *method->batch_flag != 0)
1838                 return 0;
1839         return 1;
1840 }
1841
1842 static Authmethod *
1843 authmethod_lookup(const char *name)
1844 {
1845         Authmethod *method = NULL;
1846         if (name != NULL)
1847                 for (method = authmethods; method->name != NULL; method++)
1848                         if (strcmp(name, method->name) == 0)
1849                                 return method;
1850         debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
1851         return NULL;
1852 }
1853
1854 /* XXX internal state */
1855 static Authmethod *current = NULL;
1856 static char *supported = NULL;
1857 static char *preferred = NULL;
1858
1859 /*
1860  * Given the authentication method list sent by the server, return the
1861  * next method we should try.  If the server initially sends a nil list,
1862  * use a built-in default list.
1863  */
1864 static Authmethod *
1865 authmethod_get(char *authlist)
1866 {
1867         char *name = NULL;
1868         u_int next;
1869
1870         /* Use a suitable default if we're passed a nil list.  */
1871         if (authlist == NULL || strlen(authlist) == 0)
1872                 authlist = options.preferred_authentications;
1873
1874         if (supported == NULL || strcmp(authlist, supported) != 0) {
1875                 debug3("start over, passed a different list %s", authlist);
1876                 free(supported);
1877                 supported = xstrdup(authlist);
1878                 preferred = options.preferred_authentications;
1879                 debug3("preferred %s", preferred);
1880                 current = NULL;
1881         } else if (current != NULL && authmethod_is_enabled(current))
1882                 return current;
1883
1884         for (;;) {
1885                 if ((name = match_list(preferred, supported, &next)) == NULL) {
1886                         debug("No more authentication methods to try.");
1887                         current = NULL;
1888                         return NULL;
1889                 }
1890                 preferred += next;
1891                 debug3("authmethod_lookup %s", name);
1892                 debug3("remaining preferred: %s", preferred);
1893                 if ((current = authmethod_lookup(name)) != NULL &&
1894                     authmethod_is_enabled(current)) {
1895                         debug3("authmethod_is_enabled %s", name);
1896                         debug("Next authentication method: %s", name);
1897                         free(name);
1898                         return current;
1899                 }
1900                 free(name);
1901         }
1902 }
1903
1904 static char *
1905 authmethods_get(void)
1906 {
1907         Authmethod *method = NULL;
1908         Buffer b;
1909         char *list;
1910
1911         buffer_init(&b);
1912         for (method = authmethods; method->name != NULL; method++) {
1913                 if (authmethod_is_enabled(method)) {
1914                         if (buffer_len(&b) > 0)
1915                                 buffer_append(&b, ",", 1);
1916                         buffer_append(&b, method->name, strlen(method->name));
1917                 }
1918         }
1919         if ((list = sshbuf_dup_string(&b)) == NULL)
1920                 fatal("%s: sshbuf_dup_string failed", __func__);
1921         buffer_free(&b);
1922         return list;
1923 }
1924