crypto/openssh/sshconnect2.c

   1 /* $OpenBSD: sshconnect2.c,v 1.239 2016/02/23 01:34:14 djm Exp $ */
   2 /*
   3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   4  * Copyright (c) 2008 Damien Miller.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28
  29 #include <sys/types.h>
  30 #include <sys/socket.h>
  31 #include <sys/wait.h>
  32 #include <sys/stat.h>
  33
  34 #include <errno.h>
  35 #include <fcntl.h>
  36 #include <netdb.h>
  37 #include <pwd.h>
  38 #include <signal.h>
  39 #include <stdarg.h>
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include <unistd.h>
  43 #if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H) && !defined(BROKEN_STRNVIS)
  44 #include <vis.h>
  45 #endif
  46
  47 #include "openbsd-compat/sys-queue.h"
  48
  49 #include "xmalloc.h"
  50 #include "ssh.h"
  51 #include "ssh2.h"
  52 #include "buffer.h"
  53 #include "packet.h"
  54 #include "compat.h"
  55 #include "cipher.h"
  56 #include "key.h"
  57 #include "kex.h"
  58 #include "myproposal.h"
  59 #include "sshconnect.h"
  60 #include "authfile.h"
  61 #include "dh.h"
  62 #include "authfd.h"
  63 #include "log.h"
  64 #include "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
  75 #ifdef GSSAPI
  76 #include "ssh-gss.h"
  77 #endif
  78
  79 /* import */
  80 extern char *client_version_string;
  81 extern char *server_version_string;
  82 extern Options options;
  83
  84 /*
  85  * SSH2 key exchange
  86  */
  87
  88 u_char *session_id2 = NULL;
  89 u_int session_id2_len = 0;
  90
  91 char *xxx_host;
  92 struct sockaddr *xxx_hostaddr;
  93
  94 static int
  95 verify_host_key_callback(Key *hostkey, struct ssh *ssh)
  96 {
  97         if (verify_host_key(xxx_host, xxx_hostaddr, hostkey) == -1)
  98                 fatal("Host key verification failed.");
  99         return 0;
 100 }
 101
 102 static char *
 103 order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
 104 {
 105         char *oavail, *avail, *first, *last, *alg, *hostname, *ret;
 106         size_t maxlen;
 107         struct hostkeys *hostkeys;
 108         int ktype;
 109         u_int i;
 110
 111         /* Find all hostkeys for this hostname */
 112         get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
 113         hostkeys = init_hostkeys();
 114         for (i = 0; i < options.num_user_hostfiles; i++)
 115                 load_hostkeys(hostkeys, hostname, options.user_hostfiles[i]);
 116         for (i = 0; i < options.num_system_hostfiles; i++)
 117                 load_hostkeys(hostkeys, hostname, options.system_hostfiles[i]);
 118
 119         oavail = avail = xstrdup(KEX_DEFAULT_PK_ALG);
 120         maxlen = strlen(avail) + 1;
 121         first = xmalloc(maxlen);
 122         last = xmalloc(maxlen);
 123         *first = *last = '\0';
 124
 125 #define ALG_APPEND(to, from) \
 126         do { \
 127                 if (*to != '\0') \
 128                         strlcat(to, ",", maxlen); \
 129                 strlcat(to, from, maxlen); \
 130         } while (0)
 131
 132         while ((alg = strsep(&avail, ",")) && *alg != '\0') {
 133                 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
 134                         fatal("%s: unknown alg %s", __func__, alg);
 135                 if (lookup_key_in_hostkeys_by_type(hostkeys,
 136                     sshkey_type_plain(ktype), NULL))
 137                         ALG_APPEND(first, alg);
 138                 else
 139                         ALG_APPEND(last, alg);
 140         }
 141 #undef ALG_APPEND
 142         xasprintf(&ret, "%s%s%s", first,
 143             (*first == '\0' || *last == '\0') ? "" : ",", last);
 144         if (*first != '\0')
 145                 debug3("%s: prefer hostkeyalgs: %s", __func__, first);
 146
 147         free(first);
 148         free(last);
 149         free(hostname);
 150         free(oavail);
 151         free_hostkeys(hostkeys);
 152
 153         return ret;
 154 }
 155
 156 void
 157 ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
 158 {
 159         char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
 160         char *s;
 161         struct kex *kex;
 162         int r;
 163
 164         xxx_host = host;
 165         xxx_hostaddr = hostaddr;
 166
 167         if ((s = kex_names_cat(options.kex_algorithms, "ext-info-c")) == NULL)
 168                 fatal("%s: kex_names_cat", __func__);
 169         myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(s);
 170         myproposal[PROPOSAL_ENC_ALGS_CTOS] =
 171             compat_cipher_proposal(options.ciphers);
 172         myproposal[PROPOSAL_ENC_ALGS_STOC] =
 173             compat_cipher_proposal(options.ciphers);
 174         if (options.compression) {
 175                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 176                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib@openssh.com,zlib,none";
 177         } else {
 178                 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
 179                 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com,zlib";
 180         }
 181         myproposal[PROPOSAL_MAC_ALGS_CTOS] =
 182             myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
 183         if (options.hostkeyalgorithms != NULL) {
 184                 if (kex_assemble_names(KEX_DEFAULT_PK_ALG,
 185                     &options.hostkeyalgorithms) != 0)
 186                         fatal("%s: kex_assemble_namelist", __func__);
 187                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 188                     compat_pkalg_proposal(options.hostkeyalgorithms);
 189         } else {
 190                 /* Enforce default */
 191                 options.hostkeyalgorithms = xstrdup(KEX_DEFAULT_PK_ALG);
 192                 /* Prefer algorithms that we already have keys for */
 193                 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] =
 194                     compat_pkalg_proposal(
 195                     order_hostkeyalgs(host, hostaddr, port));
 196         }
 197
 198         if (options.rekey_limit || options.rekey_interval)
 199                 packet_set_rekey_limits((u_int32_t)options.rekey_limit,
 200                     (time_t)options.rekey_interval);
 201
 202         /* start key exchange */
 203         if ((r = kex_setup(active_state, myproposal)) != 0)
 204                 fatal("kex_setup: %s", ssh_err(r));
 205         kex = active_state->kex;
 206 #ifdef WITH_OPENSSL
 207         kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 208         kex->kex[KEX_DH_GRP14_SHA1] = 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, *raw, *lang;
 500         u_int len;
 501
 502         debug3("input_userauth_banner");
 503         raw = packet_get_string(&len);
 504         lang = packet_get_string(NULL);
 505         if (len > 0 && options.log_level >= SYSLOG_LEVEL_INFO) {
 506                 if (len > 65536)
 507                         len = 65536;
 508                 msg = xmalloc(len * 4 + 1); /* max expansion from strnvis() */
 509                 strnvis(msg, raw, len * 4 + 1, VIS_SAFE|VIS_OCTAL|VIS_NOSLASH);
 510                 fprintf(stderr, "%s", msg);
 511                 free(msg);
 512         }
 513         free(raw);
 514         free(lang);
 515         return 0;
 516 }
 517
 518 /* ARGSUSED */
 519 int
 520 input_userauth_success(int type, u_int32_t seq, void *ctxt)
 521 {
 522         Authctxt *authctxt = ctxt;
 523
 524         if (authctxt == NULL)
 525                 fatal("input_userauth_success: no authentication context");
 526         free(authctxt->authlist);
 527         authctxt->authlist = NULL;
 528         if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
 529                 authctxt->method->cleanup(authctxt);
 530         free(authctxt->methoddata);
 531         authctxt->methoddata = NULL;
 532         authctxt->success = 1;                  /* break out */
 533         return 0;
 534 }
 535
 536 int
 537 input_userauth_success_unexpected(int type, u_int32_t seq, void *ctxt)
 538 {
 539         Authctxt *authctxt = ctxt;
 540
 541         if (authctxt == NULL)
 542                 fatal("%s: no authentication context", __func__);
 543
 544         fatal("Unexpected authentication success during %s.",
 545             authctxt->method->name);
 546         return 0;
 547 }
 548
 549 /* ARGSUSED */
 550 int
 551 input_userauth_failure(int type, u_int32_t seq, void *ctxt)
 552 {
 553         Authctxt *authctxt = ctxt;
 554         char *authlist = NULL;
 555         int partial;
 556
 557         if (authctxt == NULL)
 558                 fatal("input_userauth_failure: no authentication context");
 559
 560         authlist = packet_get_string(NULL);
 561         partial = packet_get_char();
 562         packet_check_eom();
 563
 564         if (partial != 0) {
 565                 logit("Authenticated with partial success.");
 566                 /* reset state */
 567                 pubkey_cleanup(authctxt);
 568                 pubkey_prepare(authctxt);
 569         }
 570         debug("Authentications that can continue: %s", authlist);
 571
 572         userauth(authctxt, authlist);
 573         return 0;
 574 }
 575
 576 /* ARGSUSED */
 577 int
 578 input_userauth_pk_ok(int type, u_int32_t seq, void *ctxt)
 579 {
 580         Authctxt *authctxt = ctxt;
 581         Key *key = NULL;
 582         Identity *id = NULL;
 583         Buffer b;
 584         int pktype, sent = 0;
 585         u_int alen, blen;
 586         char *pkalg, *fp;
 587         u_char *pkblob;
 588
 589         if (authctxt == NULL)
 590                 fatal("input_userauth_pk_ok: no authentication context");
 591         if (datafellows & SSH_BUG_PKOK) {
 592                 /* this is similar to SSH_BUG_PKAUTH */
 593                 debug2("input_userauth_pk_ok: SSH_BUG_PKOK");
 594                 pkblob = packet_get_string(&blen);
 595                 buffer_init(&b);
 596                 buffer_append(&b, pkblob, blen);
 597                 pkalg = buffer_get_string(&b, &alen);
 598                 buffer_free(&b);
 599         } else {
 600                 pkalg = packet_get_string(&alen);
 601                 pkblob = packet_get_string(&blen);
 602         }
 603         packet_check_eom();
 604
 605         debug("Server accepts key: pkalg %s blen %u", pkalg, blen);
 606
 607         if ((pktype = key_type_from_name(pkalg)) == KEY_UNSPEC) {
 608                 debug("unknown pkalg %s", pkalg);
 609                 goto done;
 610         }
 611         if ((key = key_from_blob(pkblob, blen)) == NULL) {
 612                 debug("no key from blob. pkalg %s", pkalg);
 613                 goto done;
 614         }
 615         if (key->type != pktype) {
 616                 error("input_userauth_pk_ok: type mismatch "
 617                     "for decoded key (received %d, expected %d)",
 618                     key->type, pktype);
 619                 goto done;
 620         }
 621         if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
 622             SSH_FP_DEFAULT)) == NULL)
 623                 goto done;
 624         debug2("input_userauth_pk_ok: fp %s", fp);
 625         free(fp);
 626
 627         /*
 628          * search keys in the reverse order, because last candidate has been
 629          * moved to the end of the queue.  this also avoids confusion by
 630          * duplicate keys
 631          */
 632         TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
 633                 if (key_equal(key, id->key)) {
 634                         sent = sign_and_send_pubkey(authctxt, id);
 635                         break;
 636                 }
 637         }
 638 done:
 639         if (key != NULL)
 640                 key_free(key);
 641         free(pkalg);
 642         free(pkblob);
 643
 644         /* try another method if we did not send a packet */
 645         if (sent == 0)
 646                 userauth(authctxt, NULL);
 647         return 0;
 648 }
 649
 650 #ifdef GSSAPI
 651 int
 652 userauth_gssapi(Authctxt *authctxt)
 653 {
 654         Gssctxt *gssctxt = NULL;
 655         static gss_OID_set gss_supported = NULL;
 656         static u_int mech = 0;
 657         OM_uint32 min;
 658         int ok = 0;
 659
 660         /* Try one GSSAPI method at a time, rather than sending them all at
 661          * once. */
 662
 663         if (gss_supported == NULL)
 664                 gss_indicate_mechs(&min, &gss_supported);
 665
 666         /* Check to see if the mechanism is usable before we offer it */
 667         while (mech < gss_supported->count && !ok) {
 668                 /* My DER encoding requires length<128 */
 669                 if (gss_supported->elements[mech].length < 128 &&
 670                     ssh_gssapi_check_mechanism(&gssctxt,
 671                     &gss_supported->elements[mech], authctxt->host)) {
 672                         ok = 1; /* Mechanism works */
 673                 } else {
 674                         mech++;
 675                 }
 676         }
 677
 678         if (!ok)
 679                 return 0;
 680
 681         authctxt->methoddata=(void *)gssctxt;
 682
 683         packet_start(SSH2_MSG_USERAUTH_REQUEST);
 684         packet_put_cstring(authctxt->server_user);
 685         packet_put_cstring(authctxt->service);
 686         packet_put_cstring(authctxt->method->name);
 687
 688         packet_put_int(1);
 689
 690         packet_put_int((gss_supported->elements[mech].length) + 2);
 691         packet_put_char(SSH_GSS_OIDTYPE);
 692         packet_put_char(gss_supported->elements[mech].length);
 693         packet_put_raw(gss_supported->elements[mech].elements,
 694             gss_supported->elements[mech].length);
 695
 696         packet_send();
 697
 698         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
 699         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 700         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
 701         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 702
 703         mech++; /* Move along to next candidate */
 704
 705         return 1;
 706 }
 707
 708 static OM_uint32
 709 process_gssapi_token(void *ctxt, gss_buffer_t recv_tok)
 710 {
 711         Authctxt *authctxt = ctxt;
 712         Gssctxt *gssctxt = authctxt->methoddata;
 713         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 714         gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
 715         gss_buffer_desc gssbuf;
 716         OM_uint32 status, ms, flags;
 717         Buffer b;
 718
 719         status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 720             recv_tok, &send_tok, &flags);
 721
 722         if (send_tok.length > 0) {
 723                 if (GSS_ERROR(status))
 724                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 725                 else
 726                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 727
 728                 packet_put_string(send_tok.value, send_tok.length);
 729                 packet_send();
 730                 gss_release_buffer(&ms, &send_tok);
 731         }
 732
 733         if (status == GSS_S_COMPLETE) {
 734                 /* send either complete or MIC, depending on mechanism */
 735                 if (!(flags & GSS_C_INTEG_FLAG)) {
 736                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
 737                         packet_send();
 738                 } else {
 739                         ssh_gssapi_buildmic(&b, authctxt->server_user,
 740                             authctxt->service, "gssapi-with-mic");
 741
 742                         gssbuf.value = buffer_ptr(&b);
 743                         gssbuf.length = buffer_len(&b);
 744
 745                         status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);
 746
 747                         if (!GSS_ERROR(status)) {
 748                                 packet_start(SSH2_MSG_USERAUTH_GSSAPI_MIC);
 749                                 packet_put_string(mic.value, mic.length);
 750
 751                                 packet_send();
 752                         }
 753
 754                         buffer_free(&b);
 755                         gss_release_buffer(&ms, &mic);
 756                 }
 757         }
 758
 759         return status;
 760 }
 761
 762 /* ARGSUSED */
 763 int
 764 input_gssapi_response(int type, u_int32_t plen, void *ctxt)
 765 {
 766         Authctxt *authctxt = ctxt;
 767         Gssctxt *gssctxt;
 768         int oidlen;
 769         char *oidv;
 770
 771         if (authctxt == NULL)
 772                 fatal("input_gssapi_response: no authentication context");
 773         gssctxt = authctxt->methoddata;
 774
 775         /* Setup our OID */
 776         oidv = packet_get_string(&oidlen);
 777
 778         if (oidlen <= 2 ||
 779             oidv[0] != SSH_GSS_OIDTYPE ||
 780             oidv[1] != oidlen - 2) {
 781                 free(oidv);
 782                 debug("Badly encoded mechanism OID received");
 783                 userauth(authctxt, NULL);
 784                 return 0;
 785         }
 786
 787         if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
 788                 fatal("Server returned different OID than expected");
 789
 790         packet_check_eom();
 791
 792         free(oidv);
 793
 794         if (GSS_ERROR(process_gssapi_token(ctxt, GSS_C_NO_BUFFER))) {
 795                 /* Start again with next method on list */
 796                 debug("Trying to start again");
 797                 userauth(authctxt, NULL);
 798                 return 0;
 799         }
 800         return 0;
 801 }
 802
 803 /* ARGSUSED */
 804 int
 805 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 806 {
 807         Authctxt *authctxt = ctxt;
 808         gss_buffer_desc recv_tok;
 809         OM_uint32 status;
 810         u_int slen;
 811
 812         if (authctxt == NULL)
 813                 fatal("input_gssapi_response: no authentication context");
 814
 815         recv_tok.value = packet_get_string(&slen);
 816         recv_tok.length = slen; /* safe typecast */
 817
 818         packet_check_eom();
 819
 820         status = process_gssapi_token(ctxt, &recv_tok);
 821
 822         free(recv_tok.value);
 823
 824         if (GSS_ERROR(status)) {
 825                 /* Start again with the next method in the list */
 826                 userauth(authctxt, NULL);
 827                 return 0;
 828         }
 829         return 0;
 830 }
 831
 832 /* ARGSUSED */
 833 int
 834 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 835 {
 836         Authctxt *authctxt = ctxt;
 837         Gssctxt *gssctxt;
 838         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 839         gss_buffer_desc recv_tok;
 840         OM_uint32 ms;
 841         u_int len;
 842
 843         if (authctxt == NULL)
 844                 fatal("input_gssapi_response: no authentication context");
 845         gssctxt = authctxt->methoddata;
 846
 847         recv_tok.value = packet_get_string(&len);
 848         recv_tok.length = len;
 849
 850         packet_check_eom();
 851
 852         /* Stick it into GSSAPI and see what it says */
 853         (void)ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
 854             &recv_tok, &send_tok, NULL);
 855
 856         free(recv_tok.value);
 857         gss_release_buffer(&ms, &send_tok);
 858
 859         /* Server will be returning a failed packet after this one */
 860         return 0;
 861 }
 862
 863 /* ARGSUSED */
 864 int
 865 input_gssapi_error(int type, u_int32_t plen, void *ctxt)
 866 {
 867         char *msg;
 868         char *lang;
 869
 870         /* maj */(void)packet_get_int();
 871         /* min */(void)packet_get_int();
 872         msg=packet_get_string(NULL);
 873         lang=packet_get_string(NULL);
 874
 875         packet_check_eom();
 876
 877         debug("Server GSSAPI Error:\n%s", msg);
 878         free(msg);
 879         free(lang);
 880         return 0;
 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         explicit_bzero(password, strlen(password));
 921         free(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 int
 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         free(info);
 955         free(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         explicit_bzero(password, strlen(password));
 967         free(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 0;
 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                         explicit_bzero(password, strlen(password));
 984                         free(password);
 985                         logit("Mismatch; try again, EOF to quit.");
 986                         password = NULL;
 987                 }
 988                 explicit_bzero(retype, strlen(retype));
 989                 free(retype);
 990         }
 991         packet_put_cstring(password);
 992         explicit_bzero(password, strlen(password));
 993         free(password);
 994         packet_add_padding(64);
 995         packet_send();
 996
 997         dispatch_set(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
 998             &input_userauth_passwd_changereq);
 999         return 0;
1000 }
1001
1002 static const char *
1003 identity_sign_encode(struct identity *id)
1004 {
1005         struct ssh *ssh = active_state;
1006
1007         if (id->key->type == KEY_RSA) {
1008                 switch (ssh->kex->rsa_sha2) {
1009                 case 256:
1010                         return "rsa-sha2-256";
1011                 case 512:
1012                         return "rsa-sha2-512";
1013                 }
1014         }
1015         return key_ssh_name(id->key);
1016 }
1017
1018 static int
1019 identity_sign(struct identity *id, u_char **sigp, size_t *lenp,
1020     const u_char *data, size_t datalen, u_int compat)
1021 {
1022         Key *prv;
1023         int ret;
1024         const char *alg;
1025
1026         alg = identity_sign_encode(id);
1027
1028         /* the agent supports this key */
1029         if (id->agent_fd != -1)
1030                 return ssh_agent_sign(id->agent_fd, id->key, sigp, lenp,
1031                     data, datalen, alg, compat);
1032
1033         /*
1034          * we have already loaded the private key or
1035          * the private key is stored in external hardware
1036          */
1037         if (id->isprivate || (id->key->flags & SSHKEY_FLAG_EXT))
1038                 return (sshkey_sign(id->key, sigp, lenp, data, datalen, alg,
1039                     compat));
1040         /* load the private key from the file */
1041         if ((prv = load_identity_file(id)) == NULL)
1042                 return SSH_ERR_KEY_NOT_FOUND;
1043         ret = sshkey_sign(prv, sigp, lenp, data, datalen, alg, compat);
1044         sshkey_free(prv);
1045         return (ret);
1046 }
1047
1048 static int
1049 sign_and_send_pubkey(Authctxt *authctxt, Identity *id)
1050 {
1051         Buffer b;
1052         Identity *private_id;
1053         u_char *blob, *signature;
1054         size_t slen;
1055         u_int bloblen, skip = 0;
1056         int matched, ret = -1, have_sig = 1;
1057         char *fp;
1058
1059         if ((fp = sshkey_fingerprint(id->key, options.fingerprint_hash,
1060             SSH_FP_DEFAULT)) == NULL)
1061                 return 0;
1062         debug3("%s: %s %s", __func__, key_type(id->key), fp);
1063         free(fp);
1064
1065         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1066                 /* we cannot handle this key */
1067                 debug3("sign_and_send_pubkey: cannot handle key");
1068                 return 0;
1069         }
1070         /* data to be signed */
1071         buffer_init(&b);
1072         if (datafellows & SSH_OLD_SESSIONID) {
1073                 buffer_append(&b, session_id2, session_id2_len);
1074                 skip = session_id2_len;
1075         } else {
1076                 buffer_put_string(&b, session_id2, session_id2_len);
1077                 skip = buffer_len(&b);
1078         }
1079         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1080         buffer_put_cstring(&b, authctxt->server_user);
1081         buffer_put_cstring(&b,
1082             datafellows & SSH_BUG_PKSERVICE ?
1083             "ssh-userauth" :
1084             authctxt->service);
1085         if (datafellows & SSH_BUG_PKAUTH) {
1086                 buffer_put_char(&b, have_sig);
1087         } else {
1088                 buffer_put_cstring(&b, authctxt->method->name);
1089                 buffer_put_char(&b, have_sig);
1090                 buffer_put_cstring(&b, identity_sign_encode(id));
1091         }
1092         buffer_put_string(&b, blob, bloblen);
1093
1094         /*
1095          * If the key is an certificate, try to find a matching private key
1096          * and use it to complete the signature.
1097          * If no such private key exists, return failure and continue with
1098          * other methods of authentication.
1099          */
1100         if (key_is_cert(id->key)) {
1101                 matched = 0;
1102                 TAILQ_FOREACH(private_id, &authctxt->keys, next) {
1103                         if (sshkey_equal_public(id->key, private_id->key) &&
1104                             id->key->type != private_id->key->type) {
1105                                 id = private_id;
1106                                 matched = 1;
1107                                 break;
1108                         }
1109                 }
1110                 if (matched) {
1111                         debug2("%s: using private key \"%s\"%s for "
1112                             "certificate", __func__, id->filename,
1113                             id->agent_fd != -1 ? " from agent" : "");
1114                 } else {
1115                         /* XXX maybe verbose/error? */
1116                         debug("%s: no private key for certificate "
1117                             "\"%s\"", __func__, id->filename);
1118                         free(blob);
1119                         buffer_free(&b);
1120                         return 0;
1121                 }
1122         }
1123
1124         /* generate signature */
1125         ret = identity_sign(id, &signature, &slen,
1126             buffer_ptr(&b), buffer_len(&b), datafellows);
1127         if (ret != 0) {
1128                 if (ret != SSH_ERR_KEY_NOT_FOUND)
1129                         error("%s: signing failed: %s", __func__, ssh_err(ret));
1130                 free(blob);
1131                 buffer_free(&b);
1132                 return 0;
1133         }
1134 #ifdef DEBUG_PK
1135         buffer_dump(&b);
1136 #endif
1137         if (datafellows & SSH_BUG_PKSERVICE) {
1138                 buffer_clear(&b);
1139                 buffer_append(&b, session_id2, session_id2_len);
1140                 skip = session_id2_len;
1141                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
1142                 buffer_put_cstring(&b, authctxt->server_user);
1143                 buffer_put_cstring(&b, authctxt->service);
1144                 buffer_put_cstring(&b, authctxt->method->name);
1145                 buffer_put_char(&b, have_sig);
1146                 if (!(datafellows & SSH_BUG_PKAUTH))
1147                         buffer_put_cstring(&b, key_ssh_name(id->key));
1148                 buffer_put_string(&b, blob, bloblen);
1149         }
1150         free(blob);
1151
1152         /* append signature */
1153         buffer_put_string(&b, signature, slen);
1154         free(signature);
1155
1156         /* skip session id and packet type */
1157         if (buffer_len(&b) < skip + 1)
1158                 fatal("userauth_pubkey: internal error");
1159         buffer_consume(&b, skip + 1);
1160
1161         /* put remaining data from buffer into packet */
1162         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1163         packet_put_raw(buffer_ptr(&b), buffer_len(&b));
1164         buffer_free(&b);
1165         packet_send();
1166
1167         return 1;
1168 }
1169
1170 static int
1171 send_pubkey_test(Authctxt *authctxt, Identity *id)
1172 {
1173         u_char *blob;
1174         u_int bloblen, have_sig = 0;
1175
1176         debug3("send_pubkey_test");
1177
1178         if (key_to_blob(id->key, &blob, &bloblen) == 0) {
1179                 /* we cannot handle this key */
1180                 debug3("send_pubkey_test: cannot handle key");
1181                 return 0;
1182         }
1183         /* register callback for USERAUTH_PK_OK message */
1184         dispatch_set(SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
1185
1186         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1187         packet_put_cstring(authctxt->server_user);
1188         packet_put_cstring(authctxt->service);
1189         packet_put_cstring(authctxt->method->name);
1190         packet_put_char(have_sig);
1191         if (!(datafellows & SSH_BUG_PKAUTH))
1192                 packet_put_cstring(identity_sign_encode(id));
1193         packet_put_string(blob, bloblen);
1194         free(blob);
1195         packet_send();
1196         return 1;
1197 }
1198
1199 static Key *
1200 load_identity_file(Identity *id)
1201 {
1202         Key *private = NULL;
1203         char prompt[300], *passphrase, *comment;
1204         int r, perm_ok = 0, quit = 0, i;
1205         struct stat st;
1206
1207         if (stat(id->filename, &st) < 0) {
1208                 (id->userprovided ? logit : debug3)("no such identity: %s: %s",
1209                     id->filename, strerror(errno));
1210                 return NULL;
1211         }
1212         snprintf(prompt, sizeof prompt,
1213             "Enter passphrase for key '%.100s': ", id->filename);
1214         for (i = 0; i <= options.number_of_password_prompts; i++) {
1215                 if (i == 0)
1216                         passphrase = "";
1217                 else {
1218                         passphrase = read_passphrase(prompt, 0);
1219                         if (*passphrase == '\0') {
1220                                 debug2("no passphrase given, try next key");
1221                                 free(passphrase);
1222                                 break;
1223                         }
1224                 }
1225                 switch ((r = sshkey_load_private_type(KEY_UNSPEC, id->filename,
1226                     passphrase, &private, &comment, &perm_ok))) {
1227                 case 0:
1228                         break;
1229                 case SSH_ERR_KEY_WRONG_PASSPHRASE:
1230                         if (options.batch_mode) {
1231                                 quit = 1;
1232                                 break;
1233                         }
1234                         if (i != 0)
1235                                 debug2("bad passphrase given, try again...");
1236                         break;
1237                 case SSH_ERR_SYSTEM_ERROR:
1238                         if (errno == ENOENT) {
1239                                 debug2("Load key \"%s\": %s",
1240                                     id->filename, ssh_err(r));
1241                                 quit = 1;
1242                                 break;
1243                         }
1244                         /* FALLTHROUGH */
1245                 default:
1246                         error("Load key \"%s\": %s", id->filename, ssh_err(r));
1247                         quit = 1;
1248                         break;
1249                 }
1250                 if (!quit && private != NULL && id->agent_fd == -1 &&
1251                     !(id->key && id->isprivate))
1252                         maybe_add_key_to_agent(id->filename, private, comment,
1253                             passphrase);
1254                 if (i > 0) {
1255                         explicit_bzero(passphrase, strlen(passphrase));
1256                         free(passphrase);
1257                 }
1258                 free(comment);
1259                 if (private != NULL || quit)
1260                         break;
1261         }
1262         return private;
1263 }
1264
1265 /*
1266  * try keys in the following order:
1267  *      1. certificates listed in the config file
1268  *      2. other input certificates
1269  *      3. agent keys that are found in the config file
1270  *      4. other agent keys
1271  *      5. keys that are only listed in the config file
1272  */
1273 static void
1274 pubkey_prepare(Authctxt *authctxt)
1275 {
1276         struct identity *id, *id2, *tmp;
1277         struct idlist agent, files, *preferred;
1278         struct sshkey *key;
1279         int agent_fd = -1, i, r, found;
1280         size_t j;
1281         struct ssh_identitylist *idlist;
1282
1283         TAILQ_INIT(&agent);     /* keys from the agent */
1284         TAILQ_INIT(&files);     /* keys from the config file */
1285         preferred = &authctxt->keys;
1286         TAILQ_INIT(preferred);  /* preferred order of keys */
1287
1288         /* list of keys stored in the filesystem and PKCS#11 */
1289         for (i = 0; i < options.num_identity_files; i++) {
1290                 key = options.identity_keys[i];
1291                 if (key && key->type == KEY_RSA1)
1292                         continue;
1293                 if (key && key->cert && key->cert->type != SSH2_CERT_TYPE_USER)
1294                         continue;
1295                 options.identity_keys[i] = NULL;
1296                 id = xcalloc(1, sizeof(*id));
1297                 id->agent_fd = -1;
1298                 id->key = key;
1299                 id->filename = xstrdup(options.identity_files[i]);
1300                 id->userprovided = options.identity_file_userprovided[i];
1301                 TAILQ_INSERT_TAIL(&files, id, next);
1302         }
1303         /* Prefer PKCS11 keys that are explicitly listed */
1304         TAILQ_FOREACH_SAFE(id, &files, next, tmp) {
1305                 if (id->key == NULL || (id->key->flags & SSHKEY_FLAG_EXT) == 0)
1306                         continue;
1307                 found = 0;
1308                 TAILQ_FOREACH(id2, &files, next) {
1309                         if (id2->key == NULL ||
1310                             (id2->key->flags & SSHKEY_FLAG_EXT) == 0)
1311                                 continue;
1312                         if (sshkey_equal(id->key, id2->key)) {
1313                                 TAILQ_REMOVE(&files, id, next);
1314                                 TAILQ_INSERT_TAIL(preferred, id, next);
1315                                 found = 1;
1316                                 break;
1317                         }
1318                 }
1319                 /* If IdentitiesOnly set and key not found then don't use it */
1320                 if (!found && options.identities_only) {
1321                         TAILQ_REMOVE(&files, id, next);
1322                         explicit_bzero(id, sizeof(*id));
1323                         free(id);
1324                 }
1325         }
1326         /* list of certificates specified by user */
1327         for (i = 0; i < options.num_certificate_files; i++) {
1328                 key = options.certificates[i];
1329                 if (!key_is_cert(key) || key->cert == NULL ||
1330                     key->cert->type != SSH2_CERT_TYPE_USER)
1331                         continue;
1332                 id = xcalloc(1, sizeof(*id));
1333                 id->agent_fd = -1;
1334                 id->key = key;
1335                 id->filename = xstrdup(options.certificate_files[i]);
1336                 id->userprovided = options.certificate_file_userprovided[i];
1337                 TAILQ_INSERT_TAIL(preferred, id, next);
1338         }
1339         /* list of keys supported by the agent */
1340         if ((r = ssh_get_authentication_socket(&agent_fd)) != 0) {
1341                 if (r != SSH_ERR_AGENT_NOT_PRESENT)
1342                         debug("%s: ssh_get_authentication_socket: %s",
1343                             __func__, ssh_err(r));
1344         } else if ((r = ssh_fetch_identitylist(agent_fd, 2, &idlist)) != 0) {
1345                 if (r != SSH_ERR_AGENT_NO_IDENTITIES)
1346                         debug("%s: ssh_fetch_identitylist: %s",
1347                             __func__, ssh_err(r));
1348                 close(agent_fd);
1349         } else {
1350                 for (j = 0; j < idlist->nkeys; j++) {
1351                         found = 0;
1352                         TAILQ_FOREACH(id, &files, next) {
1353                                 /*
1354                                  * agent keys from the config file are
1355                                  * preferred
1356                                  */
1357                                 if (sshkey_equal(idlist->keys[j], id->key)) {
1358                                         TAILQ_REMOVE(&files, id, next);
1359                                         TAILQ_INSERT_TAIL(preferred, id, next);
1360                                         id->agent_fd = agent_fd;
1361                                         found = 1;
1362                                         break;
1363                                 }
1364                         }
1365                         if (!found && !options.identities_only) {
1366                                 id = xcalloc(1, sizeof(*id));
1367                                 /* XXX "steals" key/comment from idlist */
1368                                 id->key = idlist->keys[j];
1369                                 id->filename = idlist->comments[j];
1370                                 idlist->keys[j] = NULL;
1371                                 idlist->comments[j] = NULL;
1372                                 id->agent_fd = agent_fd;
1373                                 TAILQ_INSERT_TAIL(&agent, id, next);
1374                         }
1375                 }
1376                 ssh_free_identitylist(idlist);
1377                 /* append remaining agent keys */
1378                 for (id = TAILQ_FIRST(&agent); id; id = TAILQ_FIRST(&agent)) {
1379                         TAILQ_REMOVE(&agent, id, next);
1380                         TAILQ_INSERT_TAIL(preferred, id, next);
1381                 }
1382                 authctxt->agent_fd = agent_fd;
1383         }
1384         /* append remaining keys from the config file */
1385         for (id = TAILQ_FIRST(&files); id; id = TAILQ_FIRST(&files)) {
1386                 TAILQ_REMOVE(&files, id, next);
1387                 TAILQ_INSERT_TAIL(preferred, id, next);
1388         }
1389         /* finally, filter by PubkeyAcceptedKeyTypes */
1390         TAILQ_FOREACH_SAFE(id, preferred, next, id2) {
1391                 if (id->key != NULL &&
1392                     match_pattern_list(sshkey_ssh_name(id->key),
1393                     options.pubkey_key_types, 0) != 1) {
1394                         debug("Skipping %s key %s - "
1395                             "not in PubkeyAcceptedKeyTypes",
1396                             sshkey_ssh_name(id->key), id->filename);
1397                         TAILQ_REMOVE(preferred, id, next);
1398                         sshkey_free(id->key);
1399                         free(id->filename);
1400                         memset(id, 0, sizeof(*id));
1401                         continue;
1402                 }
1403                 debug2("key: %s (%p)%s%s", id->filename, id->key,
1404                     id->userprovided ? ", explicit" : "",
1405                     id->agent_fd != -1 ? ", agent" : "");
1406         }
1407 }
1408
1409 static void
1410 pubkey_cleanup(Authctxt *authctxt)
1411 {
1412         Identity *id;
1413
1414         if (authctxt->agent_fd != -1)
1415                 ssh_close_authentication_socket(authctxt->agent_fd);
1416         for (id = TAILQ_FIRST(&authctxt->keys); id;
1417             id = TAILQ_FIRST(&authctxt->keys)) {
1418                 TAILQ_REMOVE(&authctxt->keys, id, next);
1419                 sshkey_free(id->key);
1420                 free(id->filename);
1421                 free(id);
1422         }
1423 }
1424
1425 static int
1426 try_identity(Identity *id)
1427 {
1428         if (!id->key)
1429                 return (0);
1430         if (key_type_plain(id->key->type) == KEY_RSA &&
1431             (datafellows & SSH_BUG_RSASIGMD5) != 0) {
1432                 debug("Skipped %s key %s for RSA/MD5 server",
1433                     key_type(id->key), id->filename);
1434                 return (0);
1435         }
1436         return (id->key->type != KEY_RSA1);
1437 }
1438
1439 int
1440 userauth_pubkey(Authctxt *authctxt)
1441 {
1442         Identity *id;
1443         int sent = 0;
1444
1445         while ((id = TAILQ_FIRST(&authctxt->keys))) {
1446                 if (id->tried++)
1447                         return (0);
1448                 /* move key to the end of the queue */
1449                 TAILQ_REMOVE(&authctxt->keys, id, next);
1450                 TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
1451                 /*
1452                  * send a test message if we have the public key. for
1453                  * encrypted keys we cannot do this and have to load the
1454                  * private key instead
1455                  */
1456                 if (id->key != NULL) {
1457                         if (try_identity(id)) {
1458                                 debug("Offering %s public key: %s",
1459                                     key_type(id->key), id->filename);
1460                                 sent = send_pubkey_test(authctxt, id);
1461                         }
1462                 } else {
1463                         debug("Trying private key: %s", id->filename);
1464                         id->key = load_identity_file(id);
1465                         if (id->key != NULL) {
1466                                 if (try_identity(id)) {
1467                                         id->isprivate = 1;
1468                                         sent = sign_and_send_pubkey(
1469                                             authctxt, id);
1470                                 }
1471                                 key_free(id->key);
1472                                 id->key = NULL;
1473                         }
1474                 }
1475                 if (sent)
1476                         return (sent);
1477         }
1478         return (0);
1479 }
1480
1481 /*
1482  * Send userauth request message specifying keyboard-interactive method.
1483  */
1484 int
1485 userauth_kbdint(Authctxt *authctxt)
1486 {
1487         static int attempt = 0;
1488
1489         if (attempt++ >= options.number_of_password_prompts)
1490                 return 0;
1491         /* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
1492         if (attempt > 1 && !authctxt->info_req_seen) {
1493                 debug3("userauth_kbdint: disable: no info_req_seen");
1494                 dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
1495                 return 0;
1496         }
1497
1498         debug2("userauth_kbdint");
1499         packet_start(SSH2_MSG_USERAUTH_REQUEST);
1500         packet_put_cstring(authctxt->server_user);
1501         packet_put_cstring(authctxt->service);
1502         packet_put_cstring(authctxt->method->name);
1503         packet_put_cstring("");                                 /* lang */
1504         packet_put_cstring(options.kbd_interactive_devices ?
1505             options.kbd_interactive_devices : "");
1506         packet_send();
1507
1508         dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
1509         return 1;
1510 }
1511
1512 /*
1513  * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
1514  */
1515 int
1516 input_userauth_info_req(int type, u_int32_t seq, void *ctxt)
1517 {
1518         Authctxt *authctxt = ctxt;
1519         char *name, *inst, *lang, *prompt, *response;
1520         u_int num_prompts, i;
1521         int echo = 0;
1522
1523         debug2("input_userauth_info_req");
1524
1525         if (authctxt == NULL)
1526                 fatal("input_userauth_info_req: no authentication context");
1527
1528         authctxt->info_req_seen = 1;
1529
1530         name = packet_get_string(NULL);
1531         inst = packet_get_string(NULL);
1532         lang = packet_get_string(NULL);
1533         if (strlen(name) > 0)
1534                 logit("%s", name);
1535         if (strlen(inst) > 0)
1536                 logit("%s", inst);
1537         free(name);
1538         free(inst);
1539         free(lang);
1540
1541         num_prompts = packet_get_int();
1542         /*
1543          * Begin to build info response packet based on prompts requested.
1544          * We commit to providing the correct number of responses, so if
1545          * further on we run into a problem that prevents this, we have to
1546          * be sure and clean this up and send a correct error response.
1547          */
1548         packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
1549         packet_put_int(num_prompts);
1550
1551         debug2("input_userauth_info_req: num_prompts %d", num_prompts);
1552         for (i = 0; i < num_prompts; i++) {
1553                 prompt = packet_get_string(NULL);
1554                 echo = packet_get_char();
1555
1556                 response = read_passphrase(prompt, echo ? RP_ECHO : 0);
1557
1558                 packet_put_cstring(response);
1559                 explicit_bzero(response, strlen(response));
1560                 free(response);
1561                 free(prompt);
1562         }
1563         packet_check_eom(); /* done with parsing incoming message. */
1564
1565         packet_add_padding(64);
1566         packet_send();
1567         return 0;
1568 }
1569
1570 static int
1571 ssh_keysign(struct sshkey *key, u_char **sigp, size_t *lenp,
1572     const u_char *data, size_t datalen)
1573 {
1574         struct sshbuf *b;
1575         struct stat st;
1576         pid_t pid;
1577         int i, r, to[2], from[2], status, sock = packet_get_connection_in();
1578         u_char rversion = 0, version = 2;
1579         void (*osigchld)(int);
1580
1581         *sigp = NULL;
1582         *lenp = 0;
1583
1584         if (stat(_PATH_SSH_KEY_SIGN, &st) < 0) {
1585                 error("%s: not installed: %s", __func__, strerror(errno));
1586                 return -1;
1587         }
1588         if (fflush(stdout) != 0) {
1589                 error("%s: fflush: %s", __func__, strerror(errno));
1590                 return -1;
1591         }
1592         if (pipe(to) < 0) {
1593                 error("%s: pipe: %s", __func__, strerror(errno));
1594                 return -1;
1595         }
1596         if (pipe(from) < 0) {
1597                 error("%s: pipe: %s", __func__, strerror(errno));
1598                 return -1;
1599         }
1600         if ((pid = fork()) < 0) {
1601                 error("%s: fork: %s", __func__, strerror(errno));
1602                 return -1;
1603         }
1604         osigchld = signal(SIGCHLD, SIG_DFL);
1605         if (pid == 0) {
1606                 /* keep the socket on exec */
1607                 fcntl(sock, F_SETFD, 0);
1608                 permanently_drop_suid(getuid());
1609                 close(from[0]);
1610                 if (dup2(from[1], STDOUT_FILENO) < 0)
1611                         fatal("%s: dup2: %s", __func__, strerror(errno));
1612                 close(to[1]);
1613                 if (dup2(to[0], STDIN_FILENO) < 0)
1614                         fatal("%s: dup2: %s", __func__, strerror(errno));
1615                 close(from[1]);
1616                 close(to[0]);
1617                 /* Close everything but stdio and the socket */
1618                 for (i = STDERR_FILENO + 1; i < sock; i++)
1619                         close(i);
1620                 closefrom(sock + 1);
1621                 debug3("%s: [child] pid=%ld, exec %s",
1622                     __func__, (long)getpid(), _PATH_SSH_KEY_SIGN);
1623                 execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *)NULL);
1624                 fatal("%s: exec(%s): %s", __func__, _PATH_SSH_KEY_SIGN,
1625                     strerror(errno));
1626         }
1627         close(from[1]);
1628         close(to[0]);
1629
1630         if ((b = sshbuf_new()) == NULL)
1631                 fatal("%s: sshbuf_new failed", __func__);
1632         /* send # of sock, data to be signed */
1633         if ((r = sshbuf_put_u32(b, sock) != 0) ||
1634             (r = sshbuf_put_string(b, data, datalen)) != 0)
1635                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
1636         if (ssh_msg_send(to[1], version, b) == -1)
1637                 fatal("%s: couldn't send request", __func__);
1638         sshbuf_reset(b);
1639         r = ssh_msg_recv(from[0], b);
1640         close(from[0]);
1641         close(to[1]);
1642         if (r < 0) {
1643                 error("%s: no reply", __func__);
1644                 goto fail;
1645         }
1646
1647         errno = 0;
1648         while (waitpid(pid, &status, 0) < 0) {
1649                 if (errno != EINTR) {
1650                         error("%s: waitpid %ld: %s",
1651                             __func__, (long)pid, strerror(errno));
1652                         goto fail;
1653                 }
1654         }
1655         if (!WIFEXITED(status)) {
1656                 error("%s: exited abnormally", __func__);
1657                 goto fail;
1658         }
1659         if (WEXITSTATUS(status) != 0) {
1660                 error("%s: exited with status %d",
1661                     __func__, WEXITSTATUS(status));
1662                 goto fail;
1663         }
1664         if ((r = sshbuf_get_u8(b, &rversion)) != 0) {
1665                 error("%s: buffer error: %s", __func__, ssh_err(r));
1666                 goto fail;
1667         }
1668         if (rversion != version) {
1669                 error("%s: bad version", __func__);
1670                 goto fail;
1671         }
1672         if ((r = sshbuf_get_string(b, sigp, lenp)) != 0) {
1673                 error("%s: buffer error: %s", __func__, ssh_err(r));
1674  fail:
1675                 signal(SIGCHLD, osigchld);
1676                 sshbuf_free(b);
1677                 return -1;
1678         }
1679         signal(SIGCHLD, osigchld);
1680         sshbuf_free(b);
1681
1682         return 0;
1683 }
1684
1685 int
1686 userauth_hostbased(Authctxt *authctxt)
1687 {
1688         struct ssh *ssh = active_state;
1689         struct sshkey *private = NULL;
1690         struct sshbuf *b = NULL;
1691         const char *service;
1692         u_char *sig = NULL, *keyblob = NULL;
1693         char *fp = NULL, *chost = NULL, *lname = NULL;
1694         size_t siglen = 0, keylen = 0;
1695         int i, r, success = 0;
1696
1697         if (authctxt->ktypes == NULL) {
1698                 authctxt->oktypes = xstrdup(options.hostbased_key_types);
1699                 authctxt->ktypes = authctxt->oktypes;
1700         }
1701
1702         /*
1703          * Work through each listed type pattern in HostbasedKeyTypes,
1704          * trying each hostkey that matches the type in turn.
1705          */
1706         for (;;) {
1707                 if (authctxt->active_ktype == NULL)
1708                         authctxt->active_ktype = strsep(&authctxt->ktypes, ",");
1709                 if (authctxt->active_ktype == NULL ||
1710                     *authctxt->active_ktype == '\0')
1711                         break;
1712                 debug3("%s: trying key type %s", __func__,
1713                     authctxt->active_ktype);
1714
1715                 /* check for a useful key */
1716                 private = NULL;
1717                 for (i = 0; i < authctxt->sensitive->nkeys; i++) {
1718                         if (authctxt->sensitive->keys[i] == NULL ||
1719                             authctxt->sensitive->keys[i]->type == KEY_RSA1 ||
1720                             authctxt->sensitive->keys[i]->type == KEY_UNSPEC)
1721                                 continue;
1722                         if (match_pattern_list(
1723                             sshkey_ssh_name(authctxt->sensitive->keys[i]),
1724                             authctxt->active_ktype, 0) != 1)
1725                                 continue;
1726                         /* we take and free the key */
1727                         private = authctxt->sensitive->keys[i];
1728                         authctxt->sensitive->keys[i] = NULL;
1729                         break;
1730                 }
1731                 /* Found one */
1732                 if (private != NULL)
1733                         break;
1734                 /* No more keys of this type; advance */
1735                 authctxt->active_ktype = NULL;
1736         }
1737         if (private == NULL) {
1738                 free(authctxt->oktypes);
1739                 authctxt->oktypes = authctxt->ktypes = NULL;
1740                 authctxt->active_ktype = NULL;
1741                 debug("No more client hostkeys for hostbased authentication.");
1742                 goto out;
1743         }
1744
1745         if ((fp = sshkey_fingerprint(private, options.fingerprint_hash,
1746             SSH_FP_DEFAULT)) == NULL) {
1747                 error("%s: sshkey_fingerprint failed", __func__);
1748                 goto out;
1749         }
1750         debug("%s: trying hostkey %s %s",
1751             __func__, sshkey_ssh_name(private), fp);
1752
1753         /* figure out a name for the client host */
1754         if ((lname = get_local_name(packet_get_connection_in())) == NULL) {
1755                 error("%s: cannot get local ipaddr/name", __func__);
1756                 goto out;
1757         }
1758
1759         /* XXX sshbuf_put_stringf? */
1760         xasprintf(&chost, "%s.", lname);
1761         debug2("%s: chost %s", __func__, chost);
1762
1763         service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
1764             authctxt->service;
1765
1766         /* construct data */
1767         if ((b = sshbuf_new()) == NULL) {
1768                 error("%s: sshbuf_new failed", __func__);
1769                 goto out;
1770         }
1771         if ((r = sshkey_to_blob(private, &keyblob, &keylen)) != 0) {
1772                 error("%s: sshkey_to_blob: %s", __func__, ssh_err(r));
1773                 goto out;
1774         }
1775         if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 ||
1776             (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1777             (r = sshbuf_put_cstring(b, authctxt->server_user)) != 0 ||
1778             (r = sshbuf_put_cstring(b, service)) != 0 ||
1779             (r = sshbuf_put_cstring(b, authctxt->method->name)) != 0 ||
1780             (r = sshbuf_put_cstring(b, key_ssh_name(private))) != 0 ||
1781             (r = sshbuf_put_string(b, keyblob, keylen)) != 0 ||
1782             (r = sshbuf_put_cstring(b, chost)) != 0 ||
1783             (r = sshbuf_put_cstring(b, authctxt->local_user)) != 0) {
1784                 error("%s: buffer error: %s", __func__, ssh_err(r));
1785                 goto out;
1786         }
1787
1788 #ifdef DEBUG_PK
1789         sshbuf_dump(b, stderr);
1790 #endif
1791         if (authctxt->sensitive->external_keysign)
1792                 r = ssh_keysign(private, &sig, &siglen,
1793                     sshbuf_ptr(b), sshbuf_len(b));
1794         else if ((r = sshkey_sign(private, &sig, &siglen,
1795             sshbuf_ptr(b), sshbuf_len(b), NULL, datafellows)) != 0)
1796                 debug("%s: sshkey_sign: %s", __func__, ssh_err(r));
1797         if (r != 0) {
1798                 error("sign using hostkey %s %s failed",
1799                     sshkey_ssh_name(private), fp);
1800                 goto out;
1801         }
1802         if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1803             (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
1804             (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
1805             (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
1806             (r = sshpkt_put_cstring(ssh, key_ssh_name(private))) != 0 ||
1807             (r = sshpkt_put_string(ssh, keyblob, keylen)) != 0 ||
1808             (r = sshpkt_put_cstring(ssh, chost)) != 0 ||
1809             (r = sshpkt_put_cstring(ssh, authctxt->local_user)) != 0 ||
1810             (r = sshpkt_put_string(ssh, sig, siglen)) != 0 ||
1811             (r = sshpkt_send(ssh)) != 0) {
1812                 error("%s: packet error: %s", __func__, ssh_err(r));
1813                 goto out;
1814         }
1815         success = 1;
1816
1817  out:
1818         if (sig != NULL) {
1819                 explicit_bzero(sig, siglen);
1820                 free(sig);
1821         }
1822         free(keyblob);
1823         free(lname);
1824         free(fp);
1825         free(chost);
1826         sshkey_free(private);
1827         sshbuf_free(b);
1828
1829         return success;
1830 }
1831
1832 /* find auth method */
1833
1834 /*
1835  * given auth method name, if configurable options permit this method fill
1836  * in auth_ident field and return true, otherwise return false.
1837  */
1838 static int
1839 authmethod_is_enabled(Authmethod *method)
1840 {
1841         if (method == NULL)
1842                 return 0;
1843         /* return false if options indicate this method is disabled */
1844         if  (method->enabled == NULL || *method->enabled == 0)
1845                 return 0;
1846         /* return false if batch mode is enabled but method needs interactive mode */
1847         if  (method->batch_flag != NULL && *method->batch_flag != 0)
1848                 return 0;
1849         return 1;
1850 }
1851
1852 static Authmethod *
1853 authmethod_lookup(const char *name)
1854 {
1855         Authmethod *method = NULL;
1856         if (name != NULL)
1857                 for (method = authmethods; method->name != NULL; method++)
1858                         if (strcmp(name, method->name) == 0)
1859                                 return method;
1860         debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
1861         return NULL;
1862 }
1863
1864 /* XXX internal state */
1865 static Authmethod *current = NULL;
1866 static char *supported = NULL;
1867 static char *preferred = NULL;
1868
1869 /*
1870  * Given the authentication method list sent by the server, return the
1871  * next method we should try.  If the server initially sends a nil list,
1872  * use a built-in default list.
1873  */
1874 static Authmethod *
1875 authmethod_get(char *authlist)
1876 {
1877         char *name = NULL;
1878         u_int next;
1879
1880         /* Use a suitable default if we're passed a nil list.  */
1881         if (authlist == NULL || strlen(authlist) == 0)
1882                 authlist = options.preferred_authentications;
1883
1884         if (supported == NULL || strcmp(authlist, supported) != 0) {
1885                 debug3("start over, passed a different list %s", authlist);
1886                 free(supported);
1887                 supported = xstrdup(authlist);
1888                 preferred = options.preferred_authentications;
1889                 debug3("preferred %s", preferred);
1890                 current = NULL;
1891         } else if (current != NULL && authmethod_is_enabled(current))
1892                 return current;
1893
1894         for (;;) {
1895                 if ((name = match_list(preferred, supported, &next)) == NULL) {
1896                         debug("No more authentication methods to try.");
1897                         current = NULL;
1898                         return NULL;
1899                 }
1900                 preferred += next;
1901                 debug3("authmethod_lookup %s", name);
1902                 debug3("remaining preferred: %s", preferred);
1903                 if ((current = authmethod_lookup(name)) != NULL &&
1904                     authmethod_is_enabled(current)) {
1905                         debug3("authmethod_is_enabled %s", name);
1906                         debug("Next authentication method: %s", name);
1907                         free(name);
1908                         return current;
1909                 }
1910                 free(name);
1911         }
1912 }
1913
1914 static char *
1915 authmethods_get(void)
1916 {
1917         Authmethod *method = NULL;
1918         Buffer b;
1919         char *list;
1920
1921         buffer_init(&b);
1922         for (method = authmethods; method->name != NULL; method++) {
1923                 if (authmethod_is_enabled(method)) {
1924                         if (buffer_len(&b) > 0)
1925                                 buffer_append(&b, ",", 1);
1926                         buffer_append(&b, method->name, strlen(method->name));
1927                 }
1928         }
1929         buffer_append(&b, "\0", 1);
1930         list = xstrdup(buffer_ptr(&b));
1931         buffer_free(&b);
1932         return list;
1933 }
1934