crypto/openssh/ssh-agent.c

   1 /* $OpenBSD: ssh-agent.c,v 1.300 2023/07/19 13:56:33 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * The authentication agent program.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  15  *
  16  * Redistribution and use in source and binary forms, with or without
  17  * modification, are permitted provided that the following conditions
  18  * are met:
  19  * 1. Redistributions of source code must retain the above copyright
  20  *    notice, this list of conditions and the following disclaimer.
  21  * 2. Redistributions in binary form must reproduce the above copyright
  22  *    notice, this list of conditions and the following disclaimer in the
  23  *    documentation and/or other materials provided with the distribution.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  26  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  27  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  28  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  29  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  30  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  31  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  32  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  34  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  35  */
  36
  37 #include "includes.h"
  38
  39 #include <sys/types.h>
  40 #include <sys/resource.h>
  41 #include <sys/stat.h>
  42 #include <sys/socket.h>
  43 #include <sys/wait.h>
  44 #ifdef HAVE_SYS_TIME_H
  45 # include <sys/time.h>
  46 #endif
  47 #ifdef HAVE_SYS_UN_H
  48 # include <sys/un.h>
  49 #endif
  50 #include "openbsd-compat/sys-queue.h"
  51
  52 #ifdef WITH_OPENSSL
  53 #include <openssl/evp.h>
  54 #include "openbsd-compat/openssl-compat.h"
  55 #endif
  56
  57 #include <errno.h>
  58 #include <fcntl.h>
  59 #include <limits.h>
  60 #ifdef HAVE_PATHS_H
  61 # include <paths.h>
  62 #endif
  63 #ifdef HAVE_POLL_H
  64 # include <poll.h>
  65 #endif
  66 #include <signal.h>
  67 #include <stdarg.h>
  68 #include <stdio.h>
  69 #include <stdlib.h>
  70 #include <time.h>
  71 #include <string.h>
  72 #include <unistd.h>
  73 #ifdef HAVE_UTIL_H
  74 # include <util.h>
  75 #endif
  76
  77 #include "xmalloc.h"
  78 #include "ssh.h"
  79 #include "ssh2.h"
  80 #include "sshbuf.h"
  81 #include "sshkey.h"
  82 #include "authfd.h"
  83 #include "log.h"
  84 #include "misc.h"
  85 #include "digest.h"
  86 #include "ssherr.h"
  87 #include "match.h"
  88 #include "msg.h"
  89 #include "pathnames.h"
  90 #include "ssh-pkcs11.h"
  91 #include "sk-api.h"
  92 #include "myproposal.h"
  93
  94 #ifndef DEFAULT_ALLOWED_PROVIDERS
  95 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*"
  96 #endif
  97
  98 /* Maximum accepted message length */
  99 #define AGENT_MAX_LEN           (256*1024)
 100 /* Maximum bytes to read from client socket */
 101 #define AGENT_RBUF_LEN          (4096)
 102 /* Maximum number of recorded session IDs/hostkeys per connection */
 103 #define AGENT_MAX_SESSION_IDS           16
 104 /* Maximum size of session ID */
 105 #define AGENT_MAX_SID_LEN               128
 106 /* Maximum number of destination constraints to accept on a key */
 107 #define AGENT_MAX_DEST_CONSTRAINTS      1024
 108
 109 /* XXX store hostkey_sid in a refcounted tree */
 110
 111 typedef enum {
 112         AUTH_UNUSED = 0,
 113         AUTH_SOCKET = 1,
 114         AUTH_CONNECTION = 2,
 115 } sock_type;
 116
 117 struct hostkey_sid {
 118         struct sshkey *key;
 119         struct sshbuf *sid;
 120         int forwarded;
 121 };
 122
 123 typedef struct socket_entry {
 124         int fd;
 125         sock_type type;
 126         struct sshbuf *input;
 127         struct sshbuf *output;
 128         struct sshbuf *request;
 129         size_t nsession_ids;
 130         struct hostkey_sid *session_ids;
 131 } SocketEntry;
 132
 133 u_int sockets_alloc = 0;
 134 SocketEntry *sockets = NULL;
 135
 136 typedef struct identity {
 137         TAILQ_ENTRY(identity) next;
 138         struct sshkey *key;
 139         char *comment;
 140         char *provider;
 141         time_t death;
 142         u_int confirm;
 143         char *sk_provider;
 144         struct dest_constraint *dest_constraints;
 145         size_t ndest_constraints;
 146 } Identity;
 147
 148 struct idtable {
 149         int nentries;
 150         TAILQ_HEAD(idqueue, identity) idlist;
 151 };
 152
 153 /* private key table */
 154 struct idtable *idtab;
 155
 156 int max_fd = 0;
 157
 158 /* pid of shell == parent of agent */
 159 pid_t parent_pid = -1;
 160 time_t parent_alive_interval = 0;
 161
 162 /* pid of process for which cleanup_socket is applicable */
 163 pid_t cleanup_pid = 0;
 164
 165 /* pathname and directory for AUTH_SOCKET */
 166 char socket_name[PATH_MAX];
 167 char socket_dir[PATH_MAX];
 168
 169 /* Pattern-list of allowed PKCS#11/Security key paths */
 170 static char *allowed_providers;
 171
 172 /*
 173  * Allows PKCS11 providers or SK keys that use non-internal providers to
 174  * be added over a remote connection (identified by session-bind@openssh.com).
 175  */
 176 static int remote_add_provider;
 177
 178 /* locking */
 179 #define LOCK_SIZE       32
 180 #define LOCK_SALT_SIZE  16
 181 #define LOCK_ROUNDS     1
 182 int locked = 0;
 183 u_char lock_pwhash[LOCK_SIZE];
 184 u_char lock_salt[LOCK_SALT_SIZE];
 185
 186 extern char *__progname;
 187
 188 /* Default lifetime in seconds (0 == forever) */
 189 static int lifetime = 0;
 190
 191 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
 192
 193 /* Refuse signing of non-SSH messages for web-origin FIDO keys */
 194 static int restrict_websafe = 1;
 195
 196 /*
 197  * Client connection count; incremented in new_socket() and decremented in
 198  * close_socket().  When it reaches 0, ssh-agent will exit.  Since it is
 199  * normally initialized to 1, it will never reach 0.  However, if the -x
 200  * option is specified, it is initialized to 0 in main(); in that case,
 201  * ssh-agent will exit as soon as it has had at least one client but no
 202  * longer has any.
 203  */
 204 static int xcount = 1;
 205
 206 static void
 207 close_socket(SocketEntry *e)
 208 {
 209         size_t i;
 210         int last = 0;
 211
 212         if (e->type == AUTH_CONNECTION) {
 213                 debug("xcount %d -> %d", xcount, xcount - 1);
 214                 if (--xcount == 0)
 215                         last = 1;
 216         }
 217         close(e->fd);
 218         sshbuf_free(e->input);
 219         sshbuf_free(e->output);
 220         sshbuf_free(e->request);
 221         for (i = 0; i < e->nsession_ids; i++) {
 222                 sshkey_free(e->session_ids[i].key);
 223                 sshbuf_free(e->session_ids[i].sid);
 224         }
 225         free(e->session_ids);
 226         memset(e, '\0', sizeof(*e));
 227         e->fd = -1;
 228         e->type = AUTH_UNUSED;
 229         if (last)
 230                 cleanup_exit(0);
 231 }
 232
 233 static void
 234 idtab_init(void)
 235 {
 236         idtab = xcalloc(1, sizeof(*idtab));
 237         TAILQ_INIT(&idtab->idlist);
 238         idtab->nentries = 0;
 239 }
 240
 241 static void
 242 free_dest_constraint_hop(struct dest_constraint_hop *dch)
 243 {
 244         u_int i;
 245
 246         if (dch == NULL)
 247                 return;
 248         free(dch->user);
 249         free(dch->hostname);
 250         for (i = 0; i < dch->nkeys; i++)
 251                 sshkey_free(dch->keys[i]);
 252         free(dch->keys);
 253         free(dch->key_is_ca);
 254 }
 255
 256 static void
 257 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs)
 258 {
 259         size_t i;
 260
 261         for (i = 0; i < ndcs; i++) {
 262                 free_dest_constraint_hop(&dcs[i].from);
 263                 free_dest_constraint_hop(&dcs[i].to);
 264         }
 265         free(dcs);
 266 }
 267
 268 static void
 269 free_identity(Identity *id)
 270 {
 271         sshkey_free(id->key);
 272         free(id->provider);
 273         free(id->comment);
 274         free(id->sk_provider);
 275         free_dest_constraints(id->dest_constraints, id->ndest_constraints);
 276         free(id);
 277 }
 278
 279 /*
 280  * Match 'key' against the key/CA list in a destination constraint hop
 281  * Returns 0 on success or -1 otherwise.
 282  */
 283 static int
 284 match_key_hop(const char *tag, const struct sshkey *key,
 285     const struct dest_constraint_hop *dch)
 286 {
 287         const char *reason = NULL;
 288         const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)";
 289         u_int i;
 290         char *fp;
 291
 292         if (key == NULL)
 293                 return -1;
 294         /* XXX logspam */
 295         if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
 296             SSH_FP_DEFAULT)) == NULL)
 297                 fatal_f("fingerprint failed");
 298         debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail",
 299             tag, hostname, sshkey_type(key), fp, dch->nkeys);
 300         free(fp);
 301         for (i = 0; i < dch->nkeys; i++) {
 302                 if (dch->keys[i] == NULL)
 303                         return -1;
 304                 /* XXX logspam */
 305                 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT,
 306                     SSH_FP_DEFAULT)) == NULL)
 307                         fatal_f("fingerprint failed");
 308                 debug3_f("%s: key %u: %s%s %s", tag, i,
 309                     dch->key_is_ca[i] ? "CA " : "",
 310                     sshkey_type(dch->keys[i]), fp);
 311                 free(fp);
 312                 if (!sshkey_is_cert(key)) {
 313                         /* plain key */
 314                         if (dch->key_is_ca[i] ||
 315                             !sshkey_equal(key, dch->keys[i]))
 316                                 continue;
 317                         return 0;
 318                 }
 319                 /* certificate */
 320                 if (!dch->key_is_ca[i])
 321                         continue;
 322                 if (key->cert == NULL || key->cert->signature_key == NULL)
 323                         return -1; /* shouldn't happen */
 324                 if (!sshkey_equal(key->cert->signature_key, dch->keys[i]))
 325                         continue;
 326                 if (sshkey_cert_check_host(key, hostname, 1,
 327                     SSH_ALLOWED_CA_SIGALGS, &reason) != 0) {
 328                         debug_f("cert %s / hostname %s rejected: %s",
 329                             key->cert->key_id, hostname, reason);
 330                         continue;
 331                 }
 332                 return 0;
 333         }
 334         return -1;
 335 }
 336
 337 /* Check destination constraints on an identity against the hostkey/user */
 338 static int
 339 permitted_by_dest_constraints(const struct sshkey *fromkey,
 340     const struct sshkey *tokey, Identity *id, const char *user,
 341     const char **hostnamep)
 342 {
 343         size_t i;
 344         struct dest_constraint *d;
 345
 346         if (hostnamep != NULL)
 347                 *hostnamep = NULL;
 348         for (i = 0; i < id->ndest_constraints; i++) {
 349                 d = id->dest_constraints + i;
 350                 /* XXX remove logspam */
 351                 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)",
 352                     i, d->from.user ? d->from.user : "",
 353                     d->from.user ? "@" : "",
 354                     d->from.hostname ? d->from.hostname : "(ORIGIN)",
 355                     d->from.nkeys,
 356                     d->to.user ? d->to.user : "", d->to.user ? "@" : "",
 357                     d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys);
 358
 359                 /* Match 'from' key */
 360                 if (fromkey == NULL) {
 361                         /* We are matching the first hop */
 362                         if (d->from.hostname != NULL || d->from.nkeys != 0)
 363                                 continue;
 364                 } else if (match_key_hop("from", fromkey, &d->from) != 0)
 365                         continue;
 366
 367                 /* Match 'to' key */
 368                 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0)
 369                         continue;
 370
 371                 /* Match user if specified */
 372                 if (d->to.user != NULL && user != NULL &&
 373                     !match_pattern(user, d->to.user))
 374                         continue;
 375
 376                 /* successfully matched this constraint */
 377                 if (hostnamep != NULL)
 378                         *hostnamep = d->to.hostname;
 379                 debug2_f("allowed for hostname %s",
 380                     d->to.hostname == NULL ? "*" : d->to.hostname);
 381                 return 0;
 382         }
 383         /* no match */
 384         debug2_f("%s identity \"%s\" not permitted for this destination",
 385             sshkey_type(id->key), id->comment);
 386         return -1;
 387 }
 388
 389 /*
 390  * Check whether hostkeys on a SocketEntry and the optionally specified user
 391  * are permitted by the destination constraints on the Identity.
 392  * Returns 0 on success or -1 otherwise.
 393  */
 394 static int
 395 identity_permitted(Identity *id, SocketEntry *e, char *user,
 396     const char **forward_hostnamep, const char **last_hostnamep)
 397 {
 398         size_t i;
 399         const char **hp;
 400         struct hostkey_sid *hks;
 401         const struct sshkey *fromkey = NULL;
 402         const char *test_user;
 403         char *fp1, *fp2;
 404
 405         /* XXX remove logspam */
 406         debug3_f("entering: key %s comment \"%s\", %zu socket bindings, "
 407             "%zu constraints", sshkey_type(id->key), id->comment,
 408             e->nsession_ids, id->ndest_constraints);
 409         if (id->ndest_constraints == 0)
 410                 return 0; /* unconstrained */
 411         if (e->nsession_ids == 0)
 412                 return 0; /* local use */
 413         /*
 414          * Walk through the hops recorded by session_id and try to find a
 415          * constraint that satisfies each.
 416          */
 417         for (i = 0; i < e->nsession_ids; i++) {
 418                 hks = e->session_ids + i;
 419                 if (hks->key == NULL)
 420                         fatal_f("internal error: no bound key");
 421                 /* XXX remove logspam */
 422                 fp1 = fp2 = NULL;
 423                 if (fromkey != NULL &&
 424                     (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT,
 425                     SSH_FP_DEFAULT)) == NULL)
 426                         fatal_f("fingerprint failed");
 427                 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT,
 428                     SSH_FP_DEFAULT)) == NULL)
 429                         fatal_f("fingerprint failed");
 430                 debug3_f("socketentry fd=%d, entry %zu %s, "
 431                     "from hostkey %s %s to user %s hostkey %s %s",
 432                     e->fd, i, hks->forwarded ? "FORWARD" : "AUTH",
 433                     fromkey ? sshkey_type(fromkey) : "(ORIGIN)",
 434                     fromkey ? fp1 : "", user ? user : "(ANY)",
 435                     sshkey_type(hks->key), fp2);
 436                 free(fp1);
 437                 free(fp2);
 438                 /*
 439                  * Record the hostnames for the initial forwarding and
 440                  * the final destination.
 441                  */
 442                 hp = NULL;
 443                 if (i == e->nsession_ids - 1)
 444                         hp = last_hostnamep;
 445                 else if (i == 0)
 446                         hp = forward_hostnamep;
 447                 /* Special handling for final recorded binding */
 448                 test_user = NULL;
 449                 if (i == e->nsession_ids - 1) {
 450                         /* Can only check user at final hop */
 451                         test_user = user;
 452                         /*
 453                          * user is only presented for signature requests.
 454                          * If this is the case, make sure last binding is not
 455                          * for a forwarding.
 456                          */
 457                         if (hks->forwarded && user != NULL) {
 458                                 error_f("tried to sign on forwarding hop");
 459                                 return -1;
 460                         }
 461                 } else if (!hks->forwarded) {
 462                         error_f("tried to forward though signing bind");
 463                         return -1;
 464                 }
 465                 if (permitted_by_dest_constraints(fromkey, hks->key, id,
 466                     test_user, hp) != 0)
 467                         return -1;
 468                 fromkey = hks->key;
 469         }
 470         /*
 471          * Another special case: if the last bound session ID was for a
 472          * forwarding, and this function is not being called to check a sign
 473          * request (i.e. no 'user' supplied), then only permit the key if
 474          * there is a permission that would allow it to be used at another
 475          * destination. This hides keys that are allowed to be used to
 476          * authenticate *to* a host but not permitted for *use* beyond it.
 477          */
 478         hks = &e->session_ids[e->nsession_ids - 1];
 479         if (hks->forwarded && user == NULL &&
 480             permitted_by_dest_constraints(hks->key, NULL, id,
 481             NULL, NULL) != 0) {
 482                 debug3_f("key permitted at host but not after");
 483                 return -1;
 484         }
 485
 486         /* success */
 487         return 0;
 488 }
 489
 490 /* return matching private key for given public key */
 491 static Identity *
 492 lookup_identity(struct sshkey *key)
 493 {
 494         Identity *id;
 495
 496         TAILQ_FOREACH(id, &idtab->idlist, next) {
 497                 if (sshkey_equal(key, id->key))
 498                         return (id);
 499         }
 500         return (NULL);
 501 }
 502
 503 /* Check confirmation of keysign request */
 504 static int
 505 confirm_key(Identity *id, const char *extra)
 506 {
 507         char *p;
 508         int ret = -1;
 509
 510         p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
 511         if (p != NULL &&
 512             ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s",
 513             id->comment, p,
 514             extra == NULL ? "" : "\n", extra == NULL ? "" : extra))
 515                 ret = 0;
 516         free(p);
 517
 518         return (ret);
 519 }
 520
 521 static void
 522 send_status(SocketEntry *e, int success)
 523 {
 524         int r;
 525
 526         if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
 527             (r = sshbuf_put_u8(e->output, success ?
 528             SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
 529                 fatal_fr(r, "compose");
 530 }
 531
 532 /* send list of supported public keys to 'client' */
 533 static void
 534 process_request_identities(SocketEntry *e)
 535 {
 536         Identity *id;
 537         struct sshbuf *msg, *keys;
 538         int r;
 539         u_int nentries = 0;
 540
 541         debug2_f("entering");
 542
 543         if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL)
 544                 fatal_f("sshbuf_new failed");
 545         TAILQ_FOREACH(id, &idtab->idlist, next) {
 546                 /* identity not visible, don't include in response */
 547                 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
 548                         continue;
 549                 if ((r = sshkey_puts_opts(id->key, keys,
 550                     SSHKEY_SERIALIZE_INFO)) != 0 ||
 551                     (r = sshbuf_put_cstring(keys, id->comment)) != 0) {
 552                         error_fr(r, "compose key/comment");
 553                         continue;
 554                 }
 555                 nentries++;
 556         }
 557         debug2_f("replying with %u allowed of %u available keys",
 558             nentries, idtab->nentries);
 559         if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
 560             (r = sshbuf_put_u32(msg, nentries)) != 0 ||
 561             (r = sshbuf_putb(msg, keys)) != 0)
 562                 fatal_fr(r, "compose");
 563         if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
 564                 fatal_fr(r, "enqueue");
 565         sshbuf_free(msg);
 566         sshbuf_free(keys);
 567 }
 568
 569
 570 static char *
 571 agent_decode_alg(struct sshkey *key, u_int flags)
 572 {
 573         if (key->type == KEY_RSA) {
 574                 if (flags & SSH_AGENT_RSA_SHA2_256)
 575                         return "rsa-sha2-256";
 576                 else if (flags & SSH_AGENT_RSA_SHA2_512)
 577                         return "rsa-sha2-512";
 578         } else if (key->type == KEY_RSA_CERT) {
 579                 if (flags & SSH_AGENT_RSA_SHA2_256)
 580                         return "rsa-sha2-256-cert-v01@openssh.com";
 581                 else if (flags & SSH_AGENT_RSA_SHA2_512)
 582                         return "rsa-sha2-512-cert-v01@openssh.com";
 583         }
 584         return NULL;
 585 }
 586
 587 /*
 588  * Attempt to parse the contents of a buffer as a SSH publickey userauth
 589  * request, checking its contents for consistency and matching the embedded
 590  * key against the one that is being used for signing.
 591  * Note: does not modify msg buffer.
 592  * Optionally extract the username, session ID and/or hostkey from the request.
 593  */
 594 static int
 595 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key,
 596     char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp)
 597 {
 598         struct sshbuf *b = NULL, *sess_id = NULL;
 599         char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL;
 600         int r;
 601         u_char t, sig_follows;
 602         struct sshkey *mkey = NULL, *hostkey = NULL;
 603
 604         if (userp != NULL)
 605                 *userp = NULL;
 606         if (sess_idp != NULL)
 607                 *sess_idp = NULL;
 608         if (hostkeyp != NULL)
 609                 *hostkeyp = NULL;
 610         if ((b = sshbuf_fromb(msg)) == NULL)
 611                 fatal_f("sshbuf_fromb");
 612
 613         /* SSH userauth request */
 614         if ((r = sshbuf_froms(b, &sess_id)) != 0)
 615                 goto out;
 616         if (sshbuf_len(sess_id) == 0) {
 617                 r = SSH_ERR_INVALID_FORMAT;
 618                 goto out;
 619         }
 620         if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */
 621             (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */
 622             (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */
 623             (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */
 624             (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */
 625             (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */
 626             (r = sshkey_froms(b, &mkey)) != 0) /* key */
 627                 goto out;
 628         if (t != SSH2_MSG_USERAUTH_REQUEST ||
 629             sig_follows != 1 ||
 630             strcmp(service, "ssh-connection") != 0 ||
 631             !sshkey_equal(expected_key, mkey) ||
 632             sshkey_type_from_name(pkalg) != expected_key->type) {
 633                 r = SSH_ERR_INVALID_FORMAT;
 634                 goto out;
 635         }
 636         if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) {
 637                 if ((r = sshkey_froms(b, &hostkey)) != 0)
 638                         goto out;
 639         } else if (strcmp(method, "publickey") != 0) {
 640                 r = SSH_ERR_INVALID_FORMAT;
 641                 goto out;
 642         }
 643         if (sshbuf_len(b) != 0) {
 644                 r = SSH_ERR_INVALID_FORMAT;
 645                 goto out;
 646         }
 647         /* success */
 648         r = 0;
 649         debug3_f("well formed userauth");
 650         if (userp != NULL) {
 651                 *userp = user;
 652                 user = NULL;
 653         }
 654         if (sess_idp != NULL) {
 655                 *sess_idp = sess_id;
 656                 sess_id = NULL;
 657         }
 658         if (hostkeyp != NULL) {
 659                 *hostkeyp = hostkey;
 660                 hostkey = NULL;
 661         }
 662  out:
 663         sshbuf_free(b);
 664         sshbuf_free(sess_id);
 665         free(user);
 666         free(service);
 667         free(method);
 668         free(pkalg);
 669         sshkey_free(mkey);
 670         sshkey_free(hostkey);
 671         return r;
 672 }
 673
 674 /*
 675  * Attempt to parse the contents of a buffer as a SSHSIG signature request.
 676  * Note: does not modify buffer.
 677  */
 678 static int
 679 parse_sshsig_request(struct sshbuf *msg)
 680 {
 681         int r;
 682         struct sshbuf *b;
 683
 684         if ((b = sshbuf_fromb(msg)) == NULL)
 685                 fatal_f("sshbuf_fromb");
 686
 687         if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 ||
 688             (r = sshbuf_consume(b, 6)) != 0 ||
 689             (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */
 690             (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */
 691             (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */
 692             (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */
 693                 goto out;
 694         if (sshbuf_len(b) != 0) {
 695                 r = SSH_ERR_INVALID_FORMAT;
 696                 goto out;
 697         }
 698         /* success */
 699         r = 0;
 700  out:
 701         sshbuf_free(b);
 702         return r;
 703 }
 704
 705 /*
 706  * This function inspects a message to be signed by a FIDO key that has a
 707  * web-like application string (i.e. one that does not begin with "ssh:".
 708  * It checks that the message is one of those expected for SSH operations
 709  * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
 710  * for the web.
 711  */
 712 static int
 713 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data)
 714 {
 715         if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) {
 716                 debug_f("signed data matches public key userauth request");
 717                 return 1;
 718         }
 719         if (parse_sshsig_request(data) == 0) {
 720                 debug_f("signed data matches SSHSIG signature request");
 721                 return 1;
 722         }
 723
 724         /* XXX check CA signature operation */
 725
 726         error("web-origin key attempting to sign non-SSH message");
 727         return 0;
 728 }
 729
 730 static int
 731 buf_equal(const struct sshbuf *a, const struct sshbuf *b)
 732 {
 733         if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL)
 734                 return SSH_ERR_INVALID_ARGUMENT;
 735         if (sshbuf_len(a) != sshbuf_len(b))
 736                 return SSH_ERR_INVALID_FORMAT;
 737         if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0)
 738                 return SSH_ERR_INVALID_FORMAT;
 739         return 0;
 740 }
 741
 742 /* ssh2 only */
 743 static void
 744 process_sign_request2(SocketEntry *e)
 745 {
 746         u_char *signature = NULL;
 747         size_t slen = 0;
 748         u_int compat = 0, flags;
 749         int r, ok = -1, retried = 0;
 750         char *fp = NULL, *pin = NULL, *prompt = NULL;
 751         char *user = NULL, *sig_dest = NULL;
 752         const char *fwd_host = NULL, *dest_host = NULL;
 753         struct sshbuf *msg = NULL, *data = NULL, *sid = NULL;
 754         struct sshkey *key = NULL, *hostkey = NULL;
 755         struct identity *id;
 756         struct notifier_ctx *notifier = NULL;
 757
 758         debug_f("entering");
 759
 760         if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL)
 761                 fatal_f("sshbuf_new failed");
 762         if ((r = sshkey_froms(e->request, &key)) != 0 ||
 763             (r = sshbuf_get_stringb(e->request, data)) != 0 ||
 764             (r = sshbuf_get_u32(e->request, &flags)) != 0) {
 765                 error_fr(r, "parse");
 766                 goto send;
 767         }
 768
 769         if ((id = lookup_identity(key)) == NULL) {
 770                 verbose_f("%s key not found", sshkey_type(key));
 771                 goto send;
 772         }
 773         if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
 774             SSH_FP_DEFAULT)) == NULL)
 775                 fatal_f("fingerprint failed");
 776
 777         if (id->ndest_constraints != 0) {
 778                 if (e->nsession_ids == 0) {
 779                         logit_f("refusing use of destination-constrained key "
 780                             "to sign on unbound connection");
 781                         goto send;
 782                 }
 783                 if (parse_userauth_request(data, key, &user, &sid,
 784                     &hostkey) != 0) {
 785                         logit_f("refusing use of destination-constrained key "
 786                            "to sign an unidentified signature");
 787                         goto send;
 788                 }
 789                 /* XXX logspam */
 790                 debug_f("user=%s", user);
 791                 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0)
 792                         goto send;
 793                 /* XXX display fwd_host/dest_host in askpass UI */
 794                 /*
 795                  * Ensure that the session ID is the most recent one
 796                  * registered on the socket - it should have been bound by
 797                  * ssh immediately before userauth.
 798                  */
 799                 if (buf_equal(sid,
 800                     e->session_ids[e->nsession_ids - 1].sid) != 0) {
 801                         error_f("unexpected session ID (%zu listed) on "
 802                             "signature request for target user %s with "
 803                             "key %s %s", e->nsession_ids, user,
 804                             sshkey_type(id->key), fp);
 805                         goto send;
 806                 }
 807                 /*
 808                  * Ensure that the hostkey embedded in the signature matches
 809                  * the one most recently bound to the socket. An exception is
 810                  * made for the initial forwarding hop.
 811                  */
 812                 if (e->nsession_ids > 1 && hostkey == NULL) {
 813                         error_f("refusing use of destination-constrained key: "
 814                             "no hostkey recorded in signature for forwarded "
 815                             "connection");
 816                         goto send;
 817                 }
 818                 if (hostkey != NULL && !sshkey_equal(hostkey,
 819                     e->session_ids[e->nsession_ids - 1].key)) {
 820                         error_f("refusing use of destination-constrained key: "
 821                             "mismatch between hostkey in request and most "
 822                             "recently bound session");
 823                         goto send;
 824                 }
 825                 xasprintf(&sig_dest, "public key authentication request for "
 826                     "user \"%s\" to listed host", user);
 827         }
 828         if (id->confirm && confirm_key(id, sig_dest) != 0) {
 829                 verbose_f("user refused key");
 830                 goto send;
 831         }
 832         if (sshkey_is_sk(id->key)) {
 833                 if (restrict_websafe &&
 834                     strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
 835                     !check_websafe_message_contents(key, data)) {
 836                         /* error already logged */
 837                         goto send;
 838                 }
 839                 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
 840                         notifier = notify_start(0,
 841                             "Confirm user presence for key %s %s%s%s",
 842                             sshkey_type(id->key), fp,
 843                             sig_dest == NULL ? "" : "\n",
 844                             sig_dest == NULL ? "" : sig_dest);
 845                 }
 846         }
 847  retry_pin:
 848         if ((r = sshkey_sign(id->key, &signature, &slen,
 849             sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags),
 850             id->sk_provider, pin, compat)) != 0) {
 851                 debug_fr(r, "sshkey_sign");
 852                 if (pin == NULL && !retried && sshkey_is_sk(id->key) &&
 853                     r == SSH_ERR_KEY_WRONG_PASSPHRASE) {
 854                         notify_complete(notifier, NULL);
 855                         notifier = NULL;
 856                         /* XXX include sig_dest */
 857                         xasprintf(&prompt, "Enter PIN%sfor %s key %s: ",
 858                             (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ?
 859                             " and confirm user presence " : " ",
 860                             sshkey_type(id->key), fp);
 861                         pin = read_passphrase(prompt, RP_USE_ASKPASS);
 862                         retried = 1;
 863                         goto retry_pin;
 864                 }
 865                 error_fr(r, "sshkey_sign");
 866                 goto send;
 867         }
 868         /* Success */
 869         ok = 0;
 870         debug_f("good signature");
 871  send:
 872         notify_complete(notifier, "User presence confirmed");
 873
 874         if (ok == 0) {
 875                 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
 876                     (r = sshbuf_put_string(msg, signature, slen)) != 0)
 877                         fatal_fr(r, "compose");
 878         } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
 879                 fatal_fr(r, "compose failure");
 880
 881         if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
 882                 fatal_fr(r, "enqueue");
 883
 884         sshbuf_free(sid);
 885         sshbuf_free(data);
 886         sshbuf_free(msg);
 887         sshkey_free(key);
 888         sshkey_free(hostkey);
 889         free(fp);
 890         free(signature);
 891         free(sig_dest);
 892         free(user);
 893         free(prompt);
 894         if (pin != NULL)
 895                 freezero(pin, strlen(pin));
 896 }
 897
 898 /* shared */
 899 static void
 900 process_remove_identity(SocketEntry *e)
 901 {
 902         int r, success = 0;
 903         struct sshkey *key = NULL;
 904         Identity *id;
 905
 906         debug2_f("entering");
 907         if ((r = sshkey_froms(e->request, &key)) != 0) {
 908                 error_fr(r, "parse key");
 909                 goto done;
 910         }
 911         if ((id = lookup_identity(key)) == NULL) {
 912                 debug_f("key not found");
 913                 goto done;
 914         }
 915         /* identity not visible, cannot be removed */
 916         if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
 917                 goto done; /* error already logged */
 918         /* We have this key, free it. */
 919         if (idtab->nentries < 1)
 920                 fatal_f("internal error: nentries %d", idtab->nentries);
 921         TAILQ_REMOVE(&idtab->idlist, id, next);
 922         free_identity(id);
 923         idtab->nentries--;
 924         success = 1;
 925  done:
 926         sshkey_free(key);
 927         send_status(e, success);
 928 }
 929
 930 static void
 931 process_remove_all_identities(SocketEntry *e)
 932 {
 933         Identity *id;
 934
 935         debug2_f("entering");
 936         /* Loop over all identities and clear the keys. */
 937         for (id = TAILQ_FIRST(&idtab->idlist); id;
 938             id = TAILQ_FIRST(&idtab->idlist)) {
 939                 TAILQ_REMOVE(&idtab->idlist, id, next);
 940                 free_identity(id);
 941         }
 942
 943         /* Mark that there are no identities. */
 944         idtab->nentries = 0;
 945
 946         /* Send success. */
 947         send_status(e, 1);
 948 }
 949
 950 /* removes expired keys and returns number of seconds until the next expiry */
 951 static time_t
 952 reaper(void)
 953 {
 954         time_t deadline = 0, now = monotime();
 955         Identity *id, *nxt;
 956
 957         for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
 958                 nxt = TAILQ_NEXT(id, next);
 959                 if (id->death == 0)
 960                         continue;
 961                 if (now >= id->death) {
 962                         debug("expiring key '%s'", id->comment);
 963                         TAILQ_REMOVE(&idtab->idlist, id, next);
 964                         free_identity(id);
 965                         idtab->nentries--;
 966                 } else
 967                         deadline = (deadline == 0) ? id->death :
 968                             MINIMUM(deadline, id->death);
 969         }
 970         if (deadline == 0 || deadline <= now)
 971                 return 0;
 972         else
 973                 return (deadline - now);
 974 }
 975
 976 static int
 977 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch)
 978 {
 979         u_char key_is_ca;
 980         size_t elen = 0;
 981         int r;
 982         struct sshkey *k = NULL;
 983         char *fp;
 984
 985         memset(dch, '\0', sizeof(*dch));
 986         if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 ||
 987             (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 ||
 988             (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
 989                 error_fr(r, "parse");
 990                 goto out;
 991         }
 992         if (elen != 0) {
 993                 error_f("unsupported extensions (len %zu)", elen);
 994                 r = SSH_ERR_FEATURE_UNSUPPORTED;
 995                 goto out;
 996         }
 997         if (*dch->hostname == '\0') {
 998                 free(dch->hostname);
 999                 dch->hostname = NULL;
1000         }
1001         if (*dch->user == '\0') {
1002                 free(dch->user);
1003                 dch->user = NULL;
1004         }
1005         while (sshbuf_len(b) != 0) {
1006                 dch->keys = xrecallocarray(dch->keys, dch->nkeys,
1007                     dch->nkeys + 1, sizeof(*dch->keys));
1008                 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys,
1009                     dch->nkeys + 1, sizeof(*dch->key_is_ca));
1010                 if ((r = sshkey_froms(b, &k)) != 0 ||
1011                     (r = sshbuf_get_u8(b, &key_is_ca)) != 0)
1012                         goto out;
1013                 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1014                     SSH_FP_DEFAULT)) == NULL)
1015                         fatal_f("fingerprint failed");
1016                 debug3_f("%s%s%s: adding %skey %s %s",
1017                     dch->user == NULL ? "" : dch->user,
1018                     dch->user == NULL ? "" : "@",
1019                     dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp);
1020                 free(fp);
1021                 dch->keys[dch->nkeys] = k;
1022                 dch->key_is_ca[dch->nkeys] = key_is_ca != 0;
1023                 dch->nkeys++;
1024                 k = NULL; /* transferred */
1025         }
1026         /* success */
1027         r = 0;
1028  out:
1029         sshkey_free(k);
1030         return r;
1031 }
1032
1033 static int
1034 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc)
1035 {
1036         struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL;
1037         int r;
1038         size_t elen = 0;
1039
1040         debug3_f("entering");
1041
1042         memset(dc, '\0', sizeof(*dc));
1043         if ((r = sshbuf_froms(m, &b)) != 0 ||
1044             (r = sshbuf_froms(b, &frombuf)) != 0 ||
1045             (r = sshbuf_froms(b, &tobuf)) != 0 ||
1046             (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
1047                 error_fr(r, "parse");
1048                 goto out;
1049         }
1050         if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 ||
1051             (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0)
1052                 goto out; /* already logged */
1053         if (elen != 0) {
1054                 error_f("unsupported extensions (len %zu)", elen);
1055                 r = SSH_ERR_FEATURE_UNSUPPORTED;
1056                 goto out;
1057         }
1058         debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)",
1059             dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys,
1060             dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "",
1061             dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys);
1062         /* check consistency */
1063         if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) ||
1064             dc->from.user != NULL) {
1065                 error_f("inconsistent \"from\" specification");
1066                 r = SSH_ERR_INVALID_FORMAT;
1067                 goto out;
1068         }
1069         if (dc->to.hostname == NULL || dc->to.nkeys == 0) {
1070                 error_f("incomplete \"to\" specification");
1071                 r = SSH_ERR_INVALID_FORMAT;
1072                 goto out;
1073         }
1074         /* success */
1075         r = 0;
1076  out:
1077         sshbuf_free(b);
1078         sshbuf_free(frombuf);
1079         sshbuf_free(tobuf);
1080         return r;
1081 }
1082
1083 static int
1084 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp,
1085     struct dest_constraint **dcsp, size_t *ndcsp)
1086 {
1087         char *ext_name = NULL;
1088         int r;
1089         struct sshbuf *b = NULL;
1090
1091         if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) {
1092                 error_fr(r, "parse constraint extension");
1093                 goto out;
1094         }
1095         debug_f("constraint ext %s", ext_name);
1096         if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
1097                 if (sk_providerp == NULL) {
1098                         error_f("%s not valid here", ext_name);
1099                         r = SSH_ERR_INVALID_FORMAT;
1100                         goto out;
1101                 }
1102                 if (*sk_providerp != NULL) {
1103                         error_f("%s already set", ext_name);
1104                         r = SSH_ERR_INVALID_FORMAT;
1105                         goto out;
1106                 }
1107                 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) {
1108                         error_fr(r, "parse %s", ext_name);
1109                         goto out;
1110                 }
1111         } else if (strcmp(ext_name,
1112             "restrict-destination-v00@openssh.com") == 0) {
1113                 if (*dcsp != NULL) {
1114                         error_f("%s already set", ext_name);
1115                         goto out;
1116                 }
1117                 if ((r = sshbuf_froms(m, &b)) != 0) {
1118                         error_fr(r, "parse %s outer", ext_name);
1119                         goto out;
1120                 }
1121                 while (sshbuf_len(b) != 0) {
1122                         if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) {
1123                                 error_f("too many %s constraints", ext_name);
1124                                 goto out;
1125                         }
1126                         *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1,
1127                             sizeof(**dcsp));
1128                         if ((r = parse_dest_constraint(b,
1129                             *dcsp + (*ndcsp)++)) != 0)
1130                                 goto out; /* error already logged */
1131                 }
1132         } else {
1133                 error_f("unsupported constraint \"%s\"", ext_name);
1134                 r = SSH_ERR_FEATURE_UNSUPPORTED;
1135                 goto out;
1136         }
1137         /* success */
1138         r = 0;
1139  out:
1140         free(ext_name);
1141         sshbuf_free(b);
1142         return r;
1143 }
1144
1145 static int
1146 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp,
1147     u_int *secondsp, int *confirmp, char **sk_providerp,
1148     struct dest_constraint **dcsp, size_t *ndcsp)
1149 {
1150         u_char ctype;
1151         int r;
1152         u_int seconds, maxsign = 0;
1153
1154         while (sshbuf_len(m)) {
1155                 if ((r = sshbuf_get_u8(m, &ctype)) != 0) {
1156                         error_fr(r, "parse constraint type");
1157                         goto out;
1158                 }
1159                 switch (ctype) {
1160                 case SSH_AGENT_CONSTRAIN_LIFETIME:
1161                         if (*deathp != 0) {
1162                                 error_f("lifetime already set");
1163                                 r = SSH_ERR_INVALID_FORMAT;
1164                                 goto out;
1165                         }
1166                         if ((r = sshbuf_get_u32(m, &seconds)) != 0) {
1167                                 error_fr(r, "parse lifetime constraint");
1168                                 goto out;
1169                         }
1170                         *deathp = monotime() + seconds;
1171                         *secondsp = seconds;
1172                         break;
1173                 case SSH_AGENT_CONSTRAIN_CONFIRM:
1174                         if (*confirmp != 0) {
1175                                 error_f("confirm already set");
1176                                 r = SSH_ERR_INVALID_FORMAT;
1177                                 goto out;
1178                         }
1179                         *confirmp = 1;
1180                         break;
1181                 case SSH_AGENT_CONSTRAIN_MAXSIGN:
1182                         if (k == NULL) {
1183                                 error_f("maxsign not valid here");
1184                                 r = SSH_ERR_INVALID_FORMAT;
1185                                 goto out;
1186                         }
1187                         if (maxsign != 0) {
1188                                 error_f("maxsign already set");
1189                                 r = SSH_ERR_INVALID_FORMAT;
1190                                 goto out;
1191                         }
1192                         if ((r = sshbuf_get_u32(m, &maxsign)) != 0) {
1193                                 error_fr(r, "parse maxsign constraint");
1194                                 goto out;
1195                         }
1196                         if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
1197                                 error_fr(r, "enable maxsign");
1198                                 goto out;
1199                         }
1200                         break;
1201                 case SSH_AGENT_CONSTRAIN_EXTENSION:
1202                         if ((r = parse_key_constraint_extension(m,
1203                             sk_providerp, dcsp, ndcsp)) != 0)
1204                                 goto out; /* error already logged */
1205                         break;
1206                 default:
1207                         error_f("Unknown constraint %d", ctype);
1208                         r = SSH_ERR_FEATURE_UNSUPPORTED;
1209                         goto out;
1210                 }
1211         }
1212         /* success */
1213         r = 0;
1214  out:
1215         return r;
1216 }
1217
1218 static void
1219 process_add_identity(SocketEntry *e)
1220 {
1221         Identity *id;
1222         int success = 0, confirm = 0;
1223         char *fp, *comment = NULL, *sk_provider = NULL;
1224         char canonical_provider[PATH_MAX];
1225         time_t death = 0;
1226         u_int seconds = 0;
1227         struct dest_constraint *dest_constraints = NULL;
1228         size_t ndest_constraints = 0;
1229         struct sshkey *k = NULL;
1230         int r = SSH_ERR_INTERNAL_ERROR;
1231
1232         debug2_f("entering");
1233         if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
1234             k == NULL ||
1235             (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
1236                 error_fr(r, "parse");
1237                 goto out;
1238         }
1239         if (parse_key_constraints(e->request, k, &death, &seconds, &confirm,
1240             &sk_provider, &dest_constraints, &ndest_constraints) != 0) {
1241                 error_f("failed to parse constraints");
1242                 sshbuf_reset(e->request);
1243                 goto out;
1244         }
1245
1246         if (sk_provider != NULL) {
1247                 if (!sshkey_is_sk(k)) {
1248                         error("Cannot add provider: %s is not an "
1249                             "authenticator-hosted key", sshkey_type(k));
1250                         goto out;
1251                 }
1252                 if (strcasecmp(sk_provider, "internal") == 0) {
1253                         debug_f("internal provider");
1254                 } else {
1255                         if (e->nsession_ids != 0 && !remote_add_provider) {
1256                                 verbose("failed add of SK provider \"%.100s\": "
1257                                     "remote addition of providers is disabled",
1258                                     sk_provider);
1259                                 goto out;
1260                         }
1261                         if (realpath(sk_provider, canonical_provider) == NULL) {
1262                                 verbose("failed provider \"%.100s\": "
1263                                     "realpath: %s", sk_provider,
1264                                     strerror(errno));
1265                                 goto out;
1266                         }
1267                         free(sk_provider);
1268                         sk_provider = xstrdup(canonical_provider);
1269                         if (match_pattern_list(sk_provider,
1270                             allowed_providers, 0) != 1) {
1271                                 error("Refusing add key: "
1272                                     "provider %s not allowed", sk_provider);
1273                                 goto out;
1274                         }
1275                 }
1276         }
1277         if ((r = sshkey_shield_private(k)) != 0) {
1278                 error_fr(r, "shield private");
1279                 goto out;
1280         }
1281         if (lifetime && !death)
1282                 death = monotime() + lifetime;
1283         if ((id = lookup_identity(k)) == NULL) {
1284                 id = xcalloc(1, sizeof(Identity));
1285                 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1286                 /* Increment the number of identities. */
1287                 idtab->nentries++;
1288         } else {
1289                 /* identity not visible, do not update */
1290                 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
1291                         goto out; /* error already logged */
1292                 /* key state might have been updated */
1293                 sshkey_free(id->key);
1294                 free(id->comment);
1295                 free(id->sk_provider);
1296                 free_dest_constraints(id->dest_constraints,
1297                     id->ndest_constraints);
1298         }
1299         /* success */
1300         id->key = k;
1301         id->comment = comment;
1302         id->death = death;
1303         id->confirm = confirm;
1304         id->sk_provider = sk_provider;
1305         id->dest_constraints = dest_constraints;
1306         id->ndest_constraints = ndest_constraints;
1307
1308         if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1309             SSH_FP_DEFAULT)) == NULL)
1310                 fatal_f("sshkey_fingerprint failed");
1311         debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) "
1312             "(provider: %s) (destination constraints: %zu)",
1313             sshkey_ssh_name(k), fp, comment, seconds, confirm,
1314             sk_provider == NULL ? "none" : sk_provider, ndest_constraints);
1315         free(fp);
1316         /* transferred */
1317         k = NULL;
1318         comment = NULL;
1319         sk_provider = NULL;
1320         dest_constraints = NULL;
1321         ndest_constraints = 0;
1322         success = 1;
1323  out:
1324         free(sk_provider);
1325         free(comment);
1326         sshkey_free(k);
1327         free_dest_constraints(dest_constraints, ndest_constraints);
1328         send_status(e, success);
1329 }
1330
1331 /* XXX todo: encrypt sensitive data with passphrase */
1332 static void
1333 process_lock_agent(SocketEntry *e, int lock)
1334 {
1335         int r, success = 0, delay;
1336         char *passwd;
1337         u_char passwdhash[LOCK_SIZE];
1338         static u_int fail_count = 0;
1339         size_t pwlen;
1340
1341         debug2_f("entering");
1342         /*
1343          * This is deliberately fatal: the user has requested that we lock,
1344          * but we can't parse their request properly. The only safe thing to
1345          * do is abort.
1346          */
1347         if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
1348                 fatal_fr(r, "parse");
1349         if (pwlen == 0) {
1350                 debug("empty password not supported");
1351         } else if (locked && !lock) {
1352                 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
1353                     passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
1354                         fatal("bcrypt_pbkdf");
1355                 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
1356                         debug("agent unlocked");
1357                         locked = 0;
1358                         fail_count = 0;
1359                         explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
1360                         success = 1;
1361                 } else {
1362                         /* delay in 0.1s increments up to 10s */
1363                         if (fail_count < 100)
1364                                 fail_count++;
1365                         delay = 100000 * fail_count;
1366                         debug("unlock failed, delaying %0.1lf seconds",
1367                             (double)delay/1000000);
1368                         usleep(delay);
1369                 }
1370                 explicit_bzero(passwdhash, sizeof(passwdhash));
1371         } else if (!locked && lock) {
1372                 debug("agent locked");
1373                 locked = 1;
1374                 arc4random_buf(lock_salt, sizeof(lock_salt));
1375                 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
1376                     lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
1377                         fatal("bcrypt_pbkdf");
1378                 success = 1;
1379         }
1380         freezero(passwd, pwlen);
1381         send_status(e, success);
1382 }
1383
1384 static void
1385 no_identities(SocketEntry *e)
1386 {
1387         struct sshbuf *msg;
1388         int r;
1389
1390         if ((msg = sshbuf_new()) == NULL)
1391                 fatal_f("sshbuf_new failed");
1392         if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
1393             (r = sshbuf_put_u32(msg, 0)) != 0 ||
1394             (r = sshbuf_put_stringb(e->output, msg)) != 0)
1395                 fatal_fr(r, "compose");
1396         sshbuf_free(msg);
1397 }
1398
1399 #ifdef ENABLE_PKCS11
1400 static void
1401 process_add_smartcard_key(SocketEntry *e)
1402 {
1403         char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1404         char **comments = NULL;
1405         int r, i, count = 0, success = 0, confirm = 0;
1406         u_int seconds = 0;
1407         time_t death = 0;
1408         struct sshkey **keys = NULL, *k;
1409         Identity *id;
1410         struct dest_constraint *dest_constraints = NULL;
1411         size_t ndest_constraints = 0;
1412
1413         debug2_f("entering");
1414         if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1415             (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1416                 error_fr(r, "parse");
1417                 goto send;
1418         }
1419         if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm,
1420             NULL, &dest_constraints, &ndest_constraints) != 0) {
1421                 error_f("failed to parse constraints");
1422                 goto send;
1423         }
1424         if (e->nsession_ids != 0 && !remote_add_provider) {
1425                 verbose("failed PKCS#11 add of \"%.100s\": remote addition of "
1426                     "providers is disabled", provider);
1427                 goto send;
1428         }
1429         if (realpath(provider, canonical_provider) == NULL) {
1430                 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1431                     provider, strerror(errno));
1432                 goto send;
1433         }
1434         if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
1435                 verbose("refusing PKCS#11 add of \"%.100s\": "
1436                     "provider not allowed", canonical_provider);
1437                 goto send;
1438         }
1439         debug_f("add %.100s", canonical_provider);
1440         if (lifetime && !death)
1441                 death = monotime() + lifetime;
1442
1443         count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
1444         for (i = 0; i < count; i++) {
1445                 k = keys[i];
1446                 if (lookup_identity(k) == NULL) {
1447                         id = xcalloc(1, sizeof(Identity));
1448                         id->key = k;
1449                         keys[i] = NULL; /* transferred */
1450                         id->provider = xstrdup(canonical_provider);
1451                         if (*comments[i] != '\0') {
1452                                 id->comment = comments[i];
1453                                 comments[i] = NULL; /* transferred */
1454                         } else {
1455                                 id->comment = xstrdup(canonical_provider);
1456                         }
1457                         id->death = death;
1458                         id->confirm = confirm;
1459                         id->dest_constraints = dest_constraints;
1460                         id->ndest_constraints = ndest_constraints;
1461                         dest_constraints = NULL; /* transferred */
1462                         ndest_constraints = 0;
1463                         TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1464                         idtab->nentries++;
1465                         success = 1;
1466                 }
1467                 /* XXX update constraints for existing keys */
1468                 sshkey_free(keys[i]);
1469                 free(comments[i]);
1470         }
1471 send:
1472         free(pin);
1473         free(provider);
1474         free(keys);
1475         free(comments);
1476         free_dest_constraints(dest_constraints, ndest_constraints);
1477         send_status(e, success);
1478 }
1479
1480 static void
1481 process_remove_smartcard_key(SocketEntry *e)
1482 {
1483         char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1484         int r, success = 0;
1485         Identity *id, *nxt;
1486
1487         debug2_f("entering");
1488         if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1489             (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1490                 error_fr(r, "parse");
1491                 goto send;
1492         }
1493         free(pin);
1494
1495         if (realpath(provider, canonical_provider) == NULL) {
1496                 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1497                     provider, strerror(errno));
1498                 goto send;
1499         }
1500
1501         debug_f("remove %.100s", canonical_provider);
1502         for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
1503                 nxt = TAILQ_NEXT(id, next);
1504                 /* Skip file--based keys */
1505                 if (id->provider == NULL)
1506                         continue;
1507                 if (!strcmp(canonical_provider, id->provider)) {
1508                         TAILQ_REMOVE(&idtab->idlist, id, next);
1509                         free_identity(id);
1510                         idtab->nentries--;
1511                 }
1512         }
1513         if (pkcs11_del_provider(canonical_provider) == 0)
1514                 success = 1;
1515         else
1516                 error_f("pkcs11_del_provider failed");
1517 send:
1518         free(provider);
1519         send_status(e, success);
1520 }
1521 #endif /* ENABLE_PKCS11 */
1522
1523 static int
1524 process_ext_session_bind(SocketEntry *e)
1525 {
1526         int r, sid_match, key_match;
1527         struct sshkey *key = NULL;
1528         struct sshbuf *sid = NULL, *sig = NULL;
1529         char *fp = NULL;
1530         size_t i;
1531         u_char fwd = 0;
1532
1533         debug2_f("entering");
1534         if ((r = sshkey_froms(e->request, &key)) != 0 ||
1535             (r = sshbuf_froms(e->request, &sid)) != 0 ||
1536             (r = sshbuf_froms(e->request, &sig)) != 0 ||
1537             (r = sshbuf_get_u8(e->request, &fwd)) != 0) {
1538                 error_fr(r, "parse");
1539                 goto out;
1540         }
1541         if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
1542             SSH_FP_DEFAULT)) == NULL)
1543                 fatal_f("fingerprint failed");
1544         /* check signature with hostkey on session ID */
1545         if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig),
1546             sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) {
1547                 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp);
1548                 goto out;
1549         }
1550         /* check whether sid/key already recorded */
1551         for (i = 0; i < e->nsession_ids; i++) {
1552                 if (!e->session_ids[i].forwarded) {
1553                         error_f("attempt to bind session ID to socket "
1554                             "previously bound for authentication attempt");
1555                         r = -1;
1556                         goto out;
1557                 }
1558                 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0;
1559                 key_match = sshkey_equal(key, e->session_ids[i].key);
1560                 if (sid_match && key_match) {
1561                         debug_f("session ID already recorded for %s %s",
1562                             sshkey_type(key), fp);
1563                         r = 0;
1564                         goto out;
1565                 } else if (sid_match) {
1566                         error_f("session ID recorded against different key "
1567                             "for %s %s", sshkey_type(key), fp);
1568                         r = -1;
1569                         goto out;
1570                 }
1571                 /*
1572                  * new sid with previously-seen key can happen, e.g. multiple
1573                  * connections to the same host.
1574                  */
1575         }
1576         /* record new key/sid */
1577         if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) {
1578                 error_f("too many session IDs recorded");
1579                 goto out;
1580         }
1581         e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids,
1582             e->nsession_ids + 1, sizeof(*e->session_ids));
1583         i = e->nsession_ids++;
1584         debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i,
1585             AGENT_MAX_SESSION_IDS);
1586         e->session_ids[i].key = key;
1587         e->session_ids[i].forwarded = fwd != 0;
1588         key = NULL; /* transferred */
1589         /* can't transfer sid; it's refcounted and scoped to request's life */
1590         if ((e->session_ids[i].sid = sshbuf_new()) == NULL)
1591                 fatal_f("sshbuf_new");
1592         if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0)
1593                 fatal_fr(r, "sshbuf_putb session ID");
1594         /* success */
1595         r = 0;
1596  out:
1597         free(fp);
1598         sshkey_free(key);
1599         sshbuf_free(sid);
1600         sshbuf_free(sig);
1601         return r == 0 ? 1 : 0;
1602 }
1603
1604 static void
1605 process_extension(SocketEntry *e)
1606 {
1607         int r, success = 0;
1608         char *name;
1609
1610         debug2_f("entering");
1611         if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) {
1612                 error_fr(r, "parse");
1613                 goto send;
1614         }
1615         if (strcmp(name, "session-bind@openssh.com") == 0)
1616                 success = process_ext_session_bind(e);
1617         else
1618                 debug_f("unsupported extension \"%s\"", name);
1619         free(name);
1620 send:
1621         send_status(e, success);
1622 }
1623 /*
1624  * dispatch incoming message.
1625  * returns 1 on success, 0 for incomplete messages or -1 on error.
1626  */
1627 static int
1628 process_message(u_int socknum)
1629 {
1630         u_int msg_len;
1631         u_char type;
1632         const u_char *cp;
1633         int r;
1634         SocketEntry *e;
1635
1636         if (socknum >= sockets_alloc)
1637                 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
1638         e = &sockets[socknum];
1639
1640         if (sshbuf_len(e->input) < 5)
1641                 return 0;               /* Incomplete message header. */
1642         cp = sshbuf_ptr(e->input);
1643         msg_len = PEEK_U32(cp);
1644         if (msg_len > AGENT_MAX_LEN) {
1645                 debug_f("socket %u (fd=%d) message too long %u > %u",
1646                     socknum, e->fd, msg_len, AGENT_MAX_LEN);
1647                 return -1;
1648         }
1649         if (sshbuf_len(e->input) < msg_len + 4)
1650                 return 0;               /* Incomplete message body. */
1651
1652         /* move the current input to e->request */
1653         sshbuf_reset(e->request);
1654         if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
1655             (r = sshbuf_get_u8(e->request, &type)) != 0) {
1656                 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
1657                     r == SSH_ERR_STRING_TOO_LARGE) {
1658                         error_fr(r, "parse");
1659                         return -1;
1660                 }
1661                 fatal_fr(r, "parse");
1662         }
1663
1664         debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
1665
1666         /* check whether agent is locked */
1667         if (locked && type != SSH_AGENTC_UNLOCK) {
1668                 sshbuf_reset(e->request);
1669                 switch (type) {
1670                 case SSH2_AGENTC_REQUEST_IDENTITIES:
1671                         /* send empty lists */
1672                         no_identities(e);
1673                         break;
1674                 default:
1675                         /* send a fail message for all other request types */
1676                         send_status(e, 0);
1677                 }
1678                 return 1;
1679         }
1680
1681         switch (type) {
1682         case SSH_AGENTC_LOCK:
1683         case SSH_AGENTC_UNLOCK:
1684                 process_lock_agent(e, type == SSH_AGENTC_LOCK);
1685                 break;
1686         case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
1687                 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
1688                 break;
1689         /* ssh2 */
1690         case SSH2_AGENTC_SIGN_REQUEST:
1691                 process_sign_request2(e);
1692                 break;
1693         case SSH2_AGENTC_REQUEST_IDENTITIES:
1694                 process_request_identities(e);
1695                 break;
1696         case SSH2_AGENTC_ADD_IDENTITY:
1697         case SSH2_AGENTC_ADD_ID_CONSTRAINED:
1698                 process_add_identity(e);
1699                 break;
1700         case SSH2_AGENTC_REMOVE_IDENTITY:
1701                 process_remove_identity(e);
1702                 break;
1703         case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
1704                 process_remove_all_identities(e);
1705                 break;
1706 #ifdef ENABLE_PKCS11
1707         case SSH_AGENTC_ADD_SMARTCARD_KEY:
1708         case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
1709                 process_add_smartcard_key(e);
1710                 break;
1711         case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
1712                 process_remove_smartcard_key(e);
1713                 break;
1714 #endif /* ENABLE_PKCS11 */
1715         case SSH_AGENTC_EXTENSION:
1716                 process_extension(e);
1717                 break;
1718         default:
1719                 /* Unknown message.  Respond with failure. */
1720                 error("Unknown message %d", type);
1721                 sshbuf_reset(e->request);
1722                 send_status(e, 0);
1723                 break;
1724         }
1725         return 1;
1726 }
1727
1728 static void
1729 new_socket(sock_type type, int fd)
1730 {
1731         u_int i, old_alloc, new_alloc;
1732
1733         debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" :
1734             (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN"));
1735         if (type == AUTH_CONNECTION) {
1736                 debug("xcount %d -> %d", xcount, xcount + 1);
1737                 ++xcount;
1738         }
1739         set_nonblock(fd);
1740
1741         if (fd > max_fd)
1742                 max_fd = fd;
1743
1744         for (i = 0; i < sockets_alloc; i++)
1745                 if (sockets[i].type == AUTH_UNUSED) {
1746                         sockets[i].fd = fd;
1747                         if ((sockets[i].input = sshbuf_new()) == NULL ||
1748                             (sockets[i].output = sshbuf_new()) == NULL ||
1749                             (sockets[i].request = sshbuf_new()) == NULL)
1750                                 fatal_f("sshbuf_new failed");
1751                         sockets[i].type = type;
1752                         return;
1753                 }
1754         old_alloc = sockets_alloc;
1755         new_alloc = sockets_alloc + 10;
1756         sockets = xrecallocarray(sockets, old_alloc, new_alloc,
1757             sizeof(sockets[0]));
1758         for (i = old_alloc; i < new_alloc; i++)
1759                 sockets[i].type = AUTH_UNUSED;
1760         sockets_alloc = new_alloc;
1761         sockets[old_alloc].fd = fd;
1762         if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
1763             (sockets[old_alloc].output = sshbuf_new()) == NULL ||
1764             (sockets[old_alloc].request = sshbuf_new()) == NULL)
1765                 fatal_f("sshbuf_new failed");
1766         sockets[old_alloc].type = type;
1767 }
1768
1769 static int
1770 handle_socket_read(u_int socknum)
1771 {
1772         struct sockaddr_un sunaddr;
1773         socklen_t slen;
1774         uid_t euid;
1775         gid_t egid;
1776         int fd;
1777
1778         slen = sizeof(sunaddr);
1779         fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
1780         if (fd == -1) {
1781                 error("accept from AUTH_SOCKET: %s", strerror(errno));
1782                 return -1;
1783         }
1784         if (getpeereid(fd, &euid, &egid) == -1) {
1785                 error("getpeereid %d failed: %s", fd, strerror(errno));
1786                 close(fd);
1787                 return -1;
1788         }
1789         if ((euid != 0) && (getuid() != euid)) {
1790                 error("uid mismatch: peer euid %u != uid %u",
1791                     (u_int) euid, (u_int) getuid());
1792                 close(fd);
1793                 return -1;
1794         }
1795         new_socket(AUTH_CONNECTION, fd);
1796         return 0;
1797 }
1798
1799 static int
1800 handle_conn_read(u_int socknum)
1801 {
1802         char buf[AGENT_RBUF_LEN];
1803         ssize_t len;
1804         int r;
1805
1806         if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
1807                 if (len == -1) {
1808                         if (errno == EAGAIN || errno == EINTR)
1809                                 return 0;
1810                         error_f("read error on socket %u (fd %d): %s",
1811                             socknum, sockets[socknum].fd, strerror(errno));
1812                 }
1813                 return -1;
1814         }
1815         if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
1816                 fatal_fr(r, "compose");
1817         explicit_bzero(buf, sizeof(buf));
1818         for (;;) {
1819                 if ((r = process_message(socknum)) == -1)
1820                         return -1;
1821                 else if (r == 0)
1822                         break;
1823         }
1824         return 0;
1825 }
1826
1827 static int
1828 handle_conn_write(u_int socknum)
1829 {
1830         ssize_t len;
1831         int r;
1832
1833         if (sshbuf_len(sockets[socknum].output) == 0)
1834                 return 0; /* shouldn't happen */
1835         if ((len = write(sockets[socknum].fd,
1836             sshbuf_ptr(sockets[socknum].output),
1837             sshbuf_len(sockets[socknum].output))) <= 0) {
1838                 if (len == -1) {
1839                         if (errno == EAGAIN || errno == EINTR)
1840                                 return 0;
1841                         error_f("read error on socket %u (fd %d): %s",
1842                             socknum, sockets[socknum].fd, strerror(errno));
1843                 }
1844                 return -1;
1845         }
1846         if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
1847                 fatal_fr(r, "consume");
1848         return 0;
1849 }
1850
1851 static void
1852 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
1853 {
1854         size_t i;
1855         u_int socknum, activefds = npfd;
1856
1857         for (i = 0; i < npfd; i++) {
1858                 if (pfd[i].revents == 0)
1859                         continue;
1860                 /* Find sockets entry */
1861                 for (socknum = 0; socknum < sockets_alloc; socknum++) {
1862                         if (sockets[socknum].type != AUTH_SOCKET &&
1863                             sockets[socknum].type != AUTH_CONNECTION)
1864                                 continue;
1865                         if (pfd[i].fd == sockets[socknum].fd)
1866                                 break;
1867                 }
1868                 if (socknum >= sockets_alloc) {
1869                         error_f("no socket for fd %d", pfd[i].fd);
1870                         continue;
1871                 }
1872                 /* Process events */
1873                 switch (sockets[socknum].type) {
1874                 case AUTH_SOCKET:
1875                         if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
1876                                 break;
1877                         if (npfd > maxfds) {
1878                                 debug3("out of fds (active %u >= limit %u); "
1879                                     "skipping accept", activefds, maxfds);
1880                                 break;
1881                         }
1882                         if (handle_socket_read(socknum) == 0)
1883                                 activefds++;
1884                         break;
1885                 case AUTH_CONNECTION:
1886                         if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 &&
1887                             handle_conn_read(socknum) != 0)
1888                                 goto close_sock;
1889                         if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
1890                             handle_conn_write(socknum) != 0) {
1891  close_sock:
1892                                 if (activefds == 0)
1893                                         fatal("activefds == 0 at close_sock");
1894                                 close_socket(&sockets[socknum]);
1895                                 activefds--;
1896                                 break;
1897                         }
1898                         break;
1899                 default:
1900                         break;
1901                 }
1902         }
1903 }
1904
1905 static int
1906 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
1907 {
1908         struct pollfd *pfd = *pfdp;
1909         size_t i, j, npfd = 0;
1910         time_t deadline;
1911         int r;
1912
1913         /* Count active sockets */
1914         for (i = 0; i < sockets_alloc; i++) {
1915                 switch (sockets[i].type) {
1916                 case AUTH_SOCKET:
1917                 case AUTH_CONNECTION:
1918                         npfd++;
1919                         break;
1920                 case AUTH_UNUSED:
1921                         break;
1922                 default:
1923                         fatal("Unknown socket type %d", sockets[i].type);
1924                         break;
1925                 }
1926         }
1927         if (npfd != *npfdp &&
1928             (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
1929                 fatal_f("recallocarray failed");
1930         *pfdp = pfd;
1931         *npfdp = npfd;
1932
1933         for (i = j = 0; i < sockets_alloc; i++) {
1934                 switch (sockets[i].type) {
1935                 case AUTH_SOCKET:
1936                         if (npfd > maxfds) {
1937                                 debug3("out of fds (active %zu >= limit %u); "
1938                                     "skipping arming listener", npfd, maxfds);
1939                                 break;
1940                         }
1941                         pfd[j].fd = sockets[i].fd;
1942                         pfd[j].revents = 0;
1943                         pfd[j].events = POLLIN;
1944                         j++;
1945                         break;
1946                 case AUTH_CONNECTION:
1947                         pfd[j].fd = sockets[i].fd;
1948                         pfd[j].revents = 0;
1949                         /*
1950                          * Only prepare to read if we can handle a full-size
1951                          * input read buffer and enqueue a max size reply..
1952                          */
1953                         if ((r = sshbuf_check_reserve(sockets[i].input,
1954                             AGENT_RBUF_LEN)) == 0 &&
1955                             (r = sshbuf_check_reserve(sockets[i].output,
1956                             AGENT_MAX_LEN)) == 0)
1957                                 pfd[j].events = POLLIN;
1958                         else if (r != SSH_ERR_NO_BUFFER_SPACE)
1959                                 fatal_fr(r, "reserve");
1960                         if (sshbuf_len(sockets[i].output) > 0)
1961                                 pfd[j].events |= POLLOUT;
1962                         j++;
1963                         break;
1964                 default:
1965                         break;
1966                 }
1967         }
1968         deadline = reaper();
1969         if (parent_alive_interval != 0)
1970                 deadline = (deadline == 0) ? parent_alive_interval :
1971                     MINIMUM(deadline, parent_alive_interval);
1972         if (deadline == 0) {
1973                 *timeoutp = -1; /* INFTIM */
1974         } else {
1975                 if (deadline > INT_MAX / 1000)
1976                         *timeoutp = INT_MAX / 1000;
1977                 else
1978                         *timeoutp = deadline * 1000;
1979         }
1980         return (1);
1981 }
1982
1983 static void
1984 cleanup_socket(void)
1985 {
1986         if (cleanup_pid != 0 && getpid() != cleanup_pid)
1987                 return;
1988         debug_f("cleanup");
1989         if (socket_name[0])
1990                 unlink(socket_name);
1991         if (socket_dir[0])
1992                 rmdir(socket_dir);
1993 }
1994
1995 void
1996 cleanup_exit(int i)
1997 {
1998         cleanup_socket();
1999         _exit(i);
2000 }
2001
2002 static void
2003 cleanup_handler(int sig)
2004 {
2005         cleanup_socket();
2006 #ifdef ENABLE_PKCS11
2007         pkcs11_terminate();
2008 #endif
2009         _exit(2);
2010 }
2011
2012 static void
2013 check_parent_exists(void)
2014 {
2015         /*
2016          * If our parent has exited then getppid() will return (pid_t)1,
2017          * so testing for that should be safe.
2018          */
2019         if (parent_pid != -1 && getppid() != parent_pid) {
2020                 /* printf("Parent has died - Authentication agent exiting.\n"); */
2021                 cleanup_socket();
2022                 _exit(2);
2023         }
2024 }
2025
2026 static void
2027 usage(void)
2028 {
2029         fprintf(stderr,
2030             "usage: ssh-agent [-c | -s] [-Ddx] [-a bind_address] [-E fingerprint_hash]\n"
2031             "                 [-O option] [-P allowed_providers] [-t life]\n"
2032             "       ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n"
2033             "                 [-P allowed_providers] [-t life] command [arg ...]\n"
2034             "       ssh-agent [-c | -s] -k\n");
2035         exit(1);
2036 }
2037
2038 int
2039 main(int ac, char **av)
2040 {
2041         int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
2042         int sock, ch, result, saved_errno;
2043         char *shell, *format, *pidstr, *agentsocket = NULL;
2044 #ifdef HAVE_SETRLIMIT
2045         struct rlimit rlim;
2046 #endif
2047         extern int optind;
2048         extern char *optarg;
2049         pid_t pid;
2050         char pidstrbuf[1 + 3 * sizeof pid];
2051         size_t len;
2052         mode_t prev_mask;
2053         int timeout = -1; /* INFTIM */
2054         struct pollfd *pfd = NULL;
2055         size_t npfd = 0;
2056         u_int maxfds;
2057
2058         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
2059         sanitise_stdfd();
2060
2061         /* drop */
2062         (void)setegid(getgid());
2063         (void)setgid(getgid());
2064         setuid(geteuid());
2065
2066         platform_disable_tracing(0);    /* strict=no */
2067
2068 #ifdef RLIMIT_NOFILE
2069         if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
2070                 fatal("%s: getrlimit: %s", __progname, strerror(errno));
2071 #endif
2072
2073         __progname = ssh_get_progname(av[0]);
2074         seed_rng();
2075
2076         while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:x")) != -1) {
2077                 switch (ch) {
2078                 case 'E':
2079                         fingerprint_hash = ssh_digest_alg_by_name(optarg);
2080                         if (fingerprint_hash == -1)
2081                                 fatal("Invalid hash algorithm \"%s\"", optarg);
2082                         break;
2083                 case 'c':
2084                         if (s_flag)
2085                                 usage();
2086                         c_flag++;
2087                         break;
2088                 case 'k':
2089                         k_flag++;
2090                         break;
2091                 case 'O':
2092                         if (strcmp(optarg, "no-restrict-websafe") == 0)
2093                                 restrict_websafe = 0;
2094                         else if (strcmp(optarg, "allow-remote-pkcs11") == 0)
2095                                 remote_add_provider = 1;
2096                         else
2097                                 fatal("Unknown -O option");
2098                         break;
2099                 case 'P':
2100                         if (allowed_providers != NULL)
2101                                 fatal("-P option already specified");
2102                         allowed_providers = xstrdup(optarg);
2103                         break;
2104                 case 's':
2105                         if (c_flag)
2106                                 usage();
2107                         s_flag++;
2108                         break;
2109                 case 'd':
2110                         if (d_flag || D_flag)
2111                                 usage();
2112                         d_flag++;
2113                         break;
2114                 case 'D':
2115                         if (d_flag || D_flag)
2116                                 usage();
2117                         D_flag++;
2118                         break;
2119                 case 'a':
2120                         agentsocket = optarg;
2121                         break;
2122                 case 't':
2123                         if ((lifetime = convtime(optarg)) == -1) {
2124                                 fprintf(stderr, "Invalid lifetime\n");
2125                                 usage();
2126                         }
2127                         break;
2128                 case 'x':
2129                         xcount = 0;
2130                         break;
2131                 default:
2132                         usage();
2133                 }
2134         }
2135         ac -= optind;
2136         av += optind;
2137
2138         if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
2139                 usage();
2140
2141         if (allowed_providers == NULL)
2142                 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
2143
2144         if (ac == 0 && !c_flag && !s_flag) {
2145                 shell = getenv("SHELL");
2146                 if (shell != NULL && (len = strlen(shell)) > 2 &&
2147                     strncmp(shell + len - 3, "csh", 3) == 0)
2148                         c_flag = 1;
2149         }
2150         if (k_flag) {
2151                 const char *errstr = NULL;
2152
2153                 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
2154                 if (pidstr == NULL) {
2155                         fprintf(stderr, "%s not set, cannot kill agent\n",
2156                             SSH_AGENTPID_ENV_NAME);
2157                         exit(1);
2158                 }
2159                 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
2160                 if (errstr) {
2161                         fprintf(stderr,
2162                             "%s=\"%s\", which is not a good PID: %s\n",
2163                             SSH_AGENTPID_ENV_NAME, pidstr, errstr);
2164                         exit(1);
2165                 }
2166                 if (kill(pid, SIGTERM) == -1) {
2167                         perror("kill");
2168                         exit(1);
2169                 }
2170                 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
2171                 printf(format, SSH_AUTHSOCKET_ENV_NAME);
2172                 printf(format, SSH_AGENTPID_ENV_NAME);
2173                 printf("echo Agent pid %ld killed;\n", (long)pid);
2174                 exit(0);
2175         }
2176
2177         /*
2178          * Minimum file descriptors:
2179          * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
2180          * a few spare for libc / stack protectors / sanitisers, etc.
2181          */
2182 #define SSH_AGENT_MIN_FDS (3+1+1+1+4)
2183         if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
2184                 fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
2185                     __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
2186         maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
2187
2188         parent_pid = getpid();
2189
2190         if (agentsocket == NULL) {
2191                 /* Create private directory for agent socket */
2192                 mktemp_proto(socket_dir, sizeof(socket_dir));
2193                 if (mkdtemp(socket_dir) == NULL) {
2194                         perror("mkdtemp: private socket dir");
2195                         exit(1);
2196                 }
2197                 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
2198                     (long)parent_pid);
2199         } else {
2200                 /* Try to use specified agent socket */
2201                 socket_dir[0] = '\0';
2202                 strlcpy(socket_name, agentsocket, sizeof socket_name);
2203         }
2204
2205         /*
2206          * Create socket early so it will exist before command gets run from
2207          * the parent.
2208          */
2209         prev_mask = umask(0177);
2210         sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
2211         if (sock < 0) {
2212                 /* XXX - unix_listener() calls error() not perror() */
2213                 *socket_name = '\0'; /* Don't unlink any existing file */
2214                 cleanup_exit(1);
2215         }
2216         umask(prev_mask);
2217
2218         /*
2219          * Fork, and have the parent execute the command, if any, or present
2220          * the socket data.  The child continues as the authentication agent.
2221          */
2222         if (D_flag || d_flag) {
2223                 log_init(__progname,
2224                     d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
2225                     SYSLOG_FACILITY_AUTH, 1);
2226                 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2227                 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2228                     SSH_AUTHSOCKET_ENV_NAME);
2229                 printf("echo Agent pid %ld;\n", (long)parent_pid);
2230                 fflush(stdout);
2231                 goto skip;
2232         }
2233         pid = fork();
2234         if (pid == -1) {
2235                 perror("fork");
2236                 cleanup_exit(1);
2237         }
2238         if (pid != 0) {         /* Parent - execute the given command. */
2239                 close(sock);
2240                 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
2241                 if (ac == 0) {
2242                         format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2243                         printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2244                             SSH_AUTHSOCKET_ENV_NAME);
2245                         printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
2246                             SSH_AGENTPID_ENV_NAME);
2247                         printf("echo Agent pid %ld;\n", (long)pid);
2248                         exit(0);
2249                 }
2250                 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
2251                     setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
2252                         perror("setenv");
2253                         exit(1);
2254                 }
2255                 execvp(av[0], av);
2256                 perror(av[0]);
2257                 exit(1);
2258         }
2259         /* child */
2260         log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
2261
2262         if (setsid() == -1) {
2263                 error("setsid: %s", strerror(errno));
2264                 cleanup_exit(1);
2265         }
2266
2267         (void)chdir("/");
2268         if (stdfd_devnull(1, 1, 1) == -1)
2269                 error_f("stdfd_devnull failed");
2270
2271 #ifdef HAVE_SETRLIMIT
2272         /* deny core dumps, since memory contains unencrypted private keys */
2273         rlim.rlim_cur = rlim.rlim_max = 0;
2274         if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
2275                 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
2276                 cleanup_exit(1);
2277         }
2278 #endif
2279
2280 skip:
2281
2282         cleanup_pid = getpid();
2283
2284 #ifdef ENABLE_PKCS11
2285         pkcs11_init(0);
2286 #endif
2287         new_socket(AUTH_SOCKET, sock);
2288         if (ac > 0)
2289                 parent_alive_interval = 10;
2290         idtab_init();
2291         ssh_signal(SIGPIPE, SIG_IGN);
2292         ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
2293         ssh_signal(SIGHUP, cleanup_handler);
2294         ssh_signal(SIGTERM, cleanup_handler);
2295
2296         if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
2297                 fatal("%s: pledge: %s", __progname, strerror(errno));
2298         platform_pledge_agent();
2299
2300         while (1) {
2301                 prepare_poll(&pfd, &npfd, &timeout, maxfds);
2302                 result = poll(pfd, npfd, timeout);
2303                 saved_errno = errno;
2304                 if (parent_alive_interval != 0)
2305                         check_parent_exists();
2306                 (void) reaper();        /* remove expired keys */
2307                 if (result == -1) {
2308                         if (saved_errno == EINTR)
2309                                 continue;
2310                         fatal("poll: %s", strerror(saved_errno));
2311                 } else if (result > 0)
2312                         after_poll(pfd, npfd, maxfds);
2313         }
2314         /* NOTREACHED */
2315 }