crypto/openssh/ssh-agent.c

   1 /* $OpenBSD: ssh-agent.c,v 1.287 2022/01/14 03:43:48 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 __RCSID("$FreeBSD$");
  39
  40 #include <sys/types.h>
  41 #include <sys/resource.h>
  42 #include <sys/stat.h>
  43 #include <sys/socket.h>
  44 #include <sys/wait.h>
  45 #ifdef HAVE_SYS_TIME_H
  46 # include <sys/time.h>
  47 #endif
  48 #ifdef HAVE_SYS_UN_H
  49 # include <sys/un.h>
  50 #endif
  51 #include "openbsd-compat/sys-queue.h"
  52
  53 #ifdef WITH_OPENSSL
  54 #include <openssl/evp.h>
  55 #include "openbsd-compat/openssl-compat.h"
  56 #endif
  57
  58 #include <errno.h>
  59 #include <fcntl.h>
  60 #include <limits.h>
  61 #ifdef HAVE_PATHS_H
  62 # include <paths.h>
  63 #endif
  64 #ifdef HAVE_POLL_H
  65 # include <poll.h>
  66 #endif
  67 #include <signal.h>
  68 #include <stdarg.h>
  69 #include <stdio.h>
  70 #include <stdlib.h>
  71 #include <time.h>
  72 #include <string.h>
  73 #include <unistd.h>
  74 #ifdef HAVE_UTIL_H
  75 # include <util.h>
  76 #endif
  77
  78 #include "xmalloc.h"
  79 #include "ssh.h"
  80 #include "ssh2.h"
  81 #include "sshbuf.h"
  82 #include "sshkey.h"
  83 #include "authfd.h"
  84 #include "compat.h"
  85 #include "log.h"
  86 #include "misc.h"
  87 #include "digest.h"
  88 #include "ssherr.h"
  89 #include "match.h"
  90 #include "msg.h"
  91 #include "ssherr.h"
  92 #include "pathnames.h"
  93 #include "ssh-pkcs11.h"
  94 #include "sk-api.h"
  95 #include "myproposal.h"
  96
  97 #ifndef DEFAULT_ALLOWED_PROVIDERS
  98 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*"
  99 #endif
 100
 101 /* Maximum accepted message length */
 102 #define AGENT_MAX_LEN           (256*1024)
 103 /* Maximum bytes to read from client socket */
 104 #define AGENT_RBUF_LEN          (4096)
 105 /* Maximum number of recorded session IDs/hostkeys per connection */
 106 #define AGENT_MAX_SESSION_IDS           16
 107 /* Maximum size of session ID */
 108 #define AGENT_MAX_SID_LEN               128
 109 /* Maximum number of destination constraints to accept on a key */
 110 #define AGENT_MAX_DEST_CONSTRAINTS      1024
 111
 112 /* XXX store hostkey_sid in a refcounted tree */
 113
 114 typedef enum {
 115         AUTH_UNUSED = 0,
 116         AUTH_SOCKET = 1,
 117         AUTH_CONNECTION = 2,
 118 } sock_type;
 119
 120 struct hostkey_sid {
 121         struct sshkey *key;
 122         struct sshbuf *sid;
 123         int forwarded;
 124 };
 125
 126 typedef struct socket_entry {
 127         int fd;
 128         sock_type type;
 129         struct sshbuf *input;
 130         struct sshbuf *output;
 131         struct sshbuf *request;
 132         size_t nsession_ids;
 133         struct hostkey_sid *session_ids;
 134 } SocketEntry;
 135
 136 u_int sockets_alloc = 0;
 137 SocketEntry *sockets = NULL;
 138
 139 typedef struct identity {
 140         TAILQ_ENTRY(identity) next;
 141         struct sshkey *key;
 142         char *comment;
 143         char *provider;
 144         time_t death;
 145         u_int confirm;
 146         char *sk_provider;
 147         struct dest_constraint *dest_constraints;
 148         size_t ndest_constraints;
 149 } Identity;
 150
 151 struct idtable {
 152         int nentries;
 153         TAILQ_HEAD(idqueue, identity) idlist;
 154 };
 155
 156 /* private key table */
 157 struct idtable *idtab;
 158
 159 int max_fd = 0;
 160
 161 /* pid of shell == parent of agent */
 162 pid_t parent_pid = -1;
 163 time_t parent_alive_interval = 0;
 164
 165 /* pid of process for which cleanup_socket is applicable */
 166 pid_t cleanup_pid = 0;
 167
 168 /* pathname and directory for AUTH_SOCKET */
 169 char socket_name[PATH_MAX];
 170 char socket_dir[PATH_MAX];
 171
 172 /* Pattern-list of allowed PKCS#11/Security key paths */
 173 static char *allowed_providers;
 174
 175 /* locking */
 176 #define LOCK_SIZE       32
 177 #define LOCK_SALT_SIZE  16
 178 #define LOCK_ROUNDS     1
 179 int locked = 0;
 180 u_char lock_pwhash[LOCK_SIZE];
 181 u_char lock_salt[LOCK_SALT_SIZE];
 182
 183 extern char *__progname;
 184
 185 /* Default lifetime in seconds (0 == forever) */
 186 static int lifetime = 0;
 187
 188 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
 189
 190 /* Refuse signing of non-SSH messages for web-origin FIDO keys */
 191 static int restrict_websafe = 1;
 192
 193 /*
 194  * Client connection count; incremented in new_socket() and decremented in
 195  * close_socket().  When it reaches 0, ssh-agent will exit.  Since it is
 196  * normally initialized to 1, it will never reach 0.  However, if the -x
 197  * option is specified, it is initialized to 0 in main(); in that case,
 198  * ssh-agent will exit as soon as it has had at least one client but no
 199  * longer has any.
 200  */
 201 static int xcount = 1;
 202
 203 static void
 204 close_socket(SocketEntry *e)
 205 {
 206         size_t i;
 207         int last = 0;
 208
 209         if (e->type == AUTH_CONNECTION) {
 210                 debug("xcount %d -> %d", xcount, xcount - 1);
 211                 if (--xcount == 0)
 212                         last = 1;
 213         }
 214         close(e->fd);
 215         sshbuf_free(e->input);
 216         sshbuf_free(e->output);
 217         sshbuf_free(e->request);
 218         for (i = 0; i < e->nsession_ids; i++) {
 219                 sshkey_free(e->session_ids[i].key);
 220                 sshbuf_free(e->session_ids[i].sid);
 221         }
 222         free(e->session_ids);
 223         memset(e, '\0', sizeof(*e));
 224         e->fd = -1;
 225         e->type = AUTH_UNUSED;
 226         if (last)
 227                 cleanup_exit(0);
 228 }
 229
 230 static void
 231 idtab_init(void)
 232 {
 233         idtab = xcalloc(1, sizeof(*idtab));
 234         TAILQ_INIT(&idtab->idlist);
 235         idtab->nentries = 0;
 236 }
 237
 238 static void
 239 free_dest_constraint_hop(struct dest_constraint_hop *dch)
 240 {
 241         u_int i;
 242
 243         if (dch == NULL)
 244                 return;
 245         free(dch->user);
 246         free(dch->hostname);
 247         for (i = 0; i < dch->nkeys; i++)
 248                 sshkey_free(dch->keys[i]);
 249         free(dch->keys);
 250         free(dch->key_is_ca);
 251 }
 252
 253 static void
 254 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs)
 255 {
 256         size_t i;
 257
 258         for (i = 0; i < ndcs; i++) {
 259                 free_dest_constraint_hop(&dcs[i].from);
 260                 free_dest_constraint_hop(&dcs[i].to);
 261         }
 262         free(dcs);
 263 }
 264
 265 static void
 266 free_identity(Identity *id)
 267 {
 268         sshkey_free(id->key);
 269         free(id->provider);
 270         free(id->comment);
 271         free(id->sk_provider);
 272         free_dest_constraints(id->dest_constraints, id->ndest_constraints);
 273         free(id);
 274 }
 275
 276 /*
 277  * Match 'key' against the key/CA list in a destination constraint hop
 278  * Returns 0 on success or -1 otherwise.
 279  */
 280 static int
 281 match_key_hop(const char *tag, const struct sshkey *key,
 282     const struct dest_constraint_hop *dch)
 283 {
 284         const char *reason = NULL;
 285         const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)";
 286         u_int i;
 287         char *fp;
 288
 289         if (key == NULL)
 290                 return -1;
 291         /* XXX logspam */
 292         if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
 293             SSH_FP_DEFAULT)) == NULL)
 294                 fatal_f("fingerprint failed");
 295         debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail",
 296             tag, hostname, sshkey_type(key), fp, dch->nkeys);
 297         free(fp);
 298         for (i = 0; i < dch->nkeys; i++) {
 299                 if (dch->keys[i] == NULL)
 300                         return -1;
 301                 /* XXX logspam */
 302                 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT,
 303                     SSH_FP_DEFAULT)) == NULL)
 304                         fatal_f("fingerprint failed");
 305                 debug3_f("%s: key %u: %s%s %s", tag, i,
 306                     dch->key_is_ca[i] ? "CA " : "",
 307                     sshkey_type(dch->keys[i]), fp);
 308                 free(fp);
 309                 if (!sshkey_is_cert(key)) {
 310                         /* plain key */
 311                         if (dch->key_is_ca[i] ||
 312                             !sshkey_equal(key, dch->keys[i]))
 313                                 continue;
 314                         return 0;
 315                 }
 316                 /* certificate */
 317                 if (!dch->key_is_ca[i])
 318                         continue;
 319                 if (key->cert == NULL || key->cert->signature_key == NULL)
 320                         return -1; /* shouldn't happen */
 321                 if (!sshkey_equal(key->cert->signature_key, dch->keys[i]))
 322                         continue;
 323                 if (sshkey_cert_check_host(key, hostname, 1,
 324                     SSH_ALLOWED_CA_SIGALGS, &reason) != 0) {
 325                         debug_f("cert %s / hostname %s rejected: %s",
 326                             key->cert->key_id, hostname, reason);
 327                         continue;
 328                 }
 329                 return 0;
 330         }
 331         return -1;
 332 }
 333
 334 /* Check destination constraints on an identity against the hostkey/user */
 335 static int
 336 permitted_by_dest_constraints(const struct sshkey *fromkey,
 337     const struct sshkey *tokey, Identity *id, const char *user,
 338     const char **hostnamep)
 339 {
 340         size_t i;
 341         struct dest_constraint *d;
 342
 343         if (hostnamep != NULL)
 344                 *hostnamep = NULL;
 345         for (i = 0; i < id->ndest_constraints; i++) {
 346                 d = id->dest_constraints + i;
 347                 /* XXX remove logspam */
 348                 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)",
 349                     i, d->from.user ? d->from.user : "",
 350                     d->from.user ? "@" : "",
 351                     d->from.hostname ? d->from.hostname : "(ORIGIN)",
 352                     d->from.nkeys,
 353                     d->to.user ? d->to.user : "", d->to.user ? "@" : "",
 354                     d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys);
 355
 356                 /* Match 'from' key */
 357                 if (fromkey == NULL) {
 358                         /* We are matching the first hop */
 359                         if (d->from.hostname != NULL || d->from.nkeys != 0)
 360                                 continue;
 361                 } else if (match_key_hop("from", fromkey, &d->from) != 0)
 362                         continue;
 363
 364                 /* Match 'to' key */
 365                 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0)
 366                         continue;
 367
 368                 /* Match user if specified */
 369                 if (d->to.user != NULL && user != NULL &&
 370                     !match_pattern(user, d->to.user))
 371                         continue;
 372
 373                 /* successfully matched this constraint */
 374                 if (hostnamep != NULL)
 375                         *hostnamep = d->to.hostname;
 376                 debug2_f("allowed for hostname %s",
 377                     d->to.hostname == NULL ? "*" : d->to.hostname);
 378                 return 0;
 379         }
 380         /* no match */
 381         debug2_f("%s identity \"%s\" not permitted for this destination",
 382             sshkey_type(id->key), id->comment);
 383         return -1;
 384 }
 385
 386 /*
 387  * Check whether hostkeys on a SocketEntry and the optionally specified user
 388  * are permitted by the destination constraints on the Identity.
 389  * Returns 0 on success or -1 otherwise.
 390  */
 391 static int
 392 identity_permitted(Identity *id, SocketEntry *e, char *user,
 393     const char **forward_hostnamep, const char **last_hostnamep)
 394 {
 395         size_t i;
 396         const char **hp;
 397         struct hostkey_sid *hks;
 398         const struct sshkey *fromkey = NULL;
 399         const char *test_user;
 400         char *fp1, *fp2;
 401
 402         /* XXX remove logspam */
 403         debug3_f("entering: key %s comment \"%s\", %zu socket bindings, "
 404             "%zu constraints", sshkey_type(id->key), id->comment,
 405             e->nsession_ids, id->ndest_constraints);
 406         if (id->ndest_constraints == 0)
 407                 return 0; /* unconstrained */
 408         if (e->nsession_ids == 0)
 409                 return 0; /* local use */
 410         /*
 411          * Walk through the hops recorded by session_id and try to find a
 412          * constraint that satisfies each.
 413          */
 414         for (i = 0; i < e->nsession_ids; i++) {
 415                 hks = e->session_ids + i;
 416                 if (hks->key == NULL)
 417                         fatal_f("internal error: no bound key");
 418                 /* XXX remove logspam */
 419                 fp1 = fp2 = NULL;
 420                 if (fromkey != NULL &&
 421                     (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT,
 422                     SSH_FP_DEFAULT)) == NULL)
 423                         fatal_f("fingerprint failed");
 424                 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT,
 425                     SSH_FP_DEFAULT)) == NULL)
 426                         fatal_f("fingerprint failed");
 427                 debug3_f("socketentry fd=%d, entry %zu %s, "
 428                     "from hostkey %s %s to user %s hostkey %s %s",
 429                     e->fd, i, hks->forwarded ? "FORWARD" : "AUTH",
 430                     fromkey ? sshkey_type(fromkey) : "(ORIGIN)",
 431                     fromkey ? fp1 : "", user ? user : "(ANY)",
 432                     sshkey_type(hks->key), fp2);
 433                 free(fp1);
 434                 free(fp2);
 435                 /*
 436                  * Record the hostnames for the initial forwarding and
 437                  * the final destination.
 438                  */
 439                 hp = NULL;
 440                 if (i == e->nsession_ids - 1)
 441                         hp = last_hostnamep;
 442                 else if (i == 0)
 443                         hp = forward_hostnamep;
 444                 /* Special handling for final recorded binding */
 445                 test_user = NULL;
 446                 if (i == e->nsession_ids - 1) {
 447                         /* Can only check user at final hop */
 448                         test_user = user;
 449                         /*
 450                          * user is only presented for signature requests.
 451                          * If this is the case, make sure last binding is not
 452                          * for a forwarding.
 453                          */
 454                         if (hks->forwarded && user != NULL) {
 455                                 error_f("tried to sign on forwarding hop");
 456                                 return -1;
 457                         }
 458                 } else if (!hks->forwarded) {
 459                         error_f("tried to forward though signing bind");
 460                         return -1;
 461                 }
 462                 if (permitted_by_dest_constraints(fromkey, hks->key, id,
 463                     test_user, hp) != 0)
 464                         return -1;
 465                 fromkey = hks->key;
 466         }
 467         /*
 468          * Another special case: if the last bound session ID was for a
 469          * forwarding, and this function is not being called to check a sign
 470          * request (i.e. no 'user' supplied), then only permit the key if
 471          * there is a permission that would allow it to be used at another
 472          * destination. This hides keys that are allowed to be used to
 473          * authenticate *to* a host but not permitted for *use* beyond it.
 474          */
 475         hks = &e->session_ids[e->nsession_ids - 1];
 476         if (hks->forwarded && user == NULL &&
 477             permitted_by_dest_constraints(hks->key, NULL, id,
 478             NULL, NULL) != 0) {
 479                 debug3_f("key permitted at host but not after");
 480                 return -1;
 481         }
 482
 483         /* success */
 484         return 0;
 485 }
 486
 487 /* return matching private key for given public key */
 488 static Identity *
 489 lookup_identity(struct sshkey *key)
 490 {
 491         Identity *id;
 492
 493         TAILQ_FOREACH(id, &idtab->idlist, next) {
 494                 if (sshkey_equal(key, id->key))
 495                         return (id);
 496         }
 497         return (NULL);
 498 }
 499
 500 /* Check confirmation of keysign request */
 501 static int
 502 confirm_key(Identity *id, const char *extra)
 503 {
 504         char *p;
 505         int ret = -1;
 506
 507         p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
 508         if (p != NULL &&
 509             ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s",
 510             id->comment, p,
 511             extra == NULL ? "" : "\n", extra == NULL ? "" : extra))
 512                 ret = 0;
 513         free(p);
 514
 515         return (ret);
 516 }
 517
 518 static void
 519 send_status(SocketEntry *e, int success)
 520 {
 521         int r;
 522
 523         if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
 524             (r = sshbuf_put_u8(e->output, success ?
 525             SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
 526                 fatal_fr(r, "compose");
 527 }
 528
 529 /* send list of supported public keys to 'client' */
 530 static void
 531 process_request_identities(SocketEntry *e)
 532 {
 533         Identity *id;
 534         struct sshbuf *msg, *keys;
 535         int r;
 536         u_int nentries = 0;
 537
 538         debug2_f("entering");
 539
 540         if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL)
 541                 fatal_f("sshbuf_new failed");
 542         TAILQ_FOREACH(id, &idtab->idlist, next) {
 543                 /* identity not visible, don't include in response */
 544                 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
 545                         continue;
 546                 if ((r = sshkey_puts_opts(id->key, keys,
 547                     SSHKEY_SERIALIZE_INFO)) != 0 ||
 548                     (r = sshbuf_put_cstring(keys, id->comment)) != 0) {
 549                         error_fr(r, "compose key/comment");
 550                         continue;
 551                 }
 552                 nentries++;
 553         }
 554         debug2_f("replying with %u allowed of %u available keys",
 555             nentries, idtab->nentries);
 556         if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
 557             (r = sshbuf_put_u32(msg, nentries)) != 0 ||
 558             (r = sshbuf_putb(msg, keys)) != 0)
 559                 fatal_fr(r, "compose");
 560         if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
 561                 fatal_fr(r, "enqueue");
 562         sshbuf_free(msg);
 563         sshbuf_free(keys);
 564 }
 565
 566
 567 static char *
 568 agent_decode_alg(struct sshkey *key, u_int flags)
 569 {
 570         if (key->type == KEY_RSA) {
 571                 if (flags & SSH_AGENT_RSA_SHA2_256)
 572                         return "rsa-sha2-256";
 573                 else if (flags & SSH_AGENT_RSA_SHA2_512)
 574                         return "rsa-sha2-512";
 575         } else if (key->type == KEY_RSA_CERT) {
 576                 if (flags & SSH_AGENT_RSA_SHA2_256)
 577                         return "rsa-sha2-256-cert-v01@openssh.com";
 578                 else if (flags & SSH_AGENT_RSA_SHA2_512)
 579                         return "rsa-sha2-512-cert-v01@openssh.com";
 580         }
 581         return NULL;
 582 }
 583
 584 /*
 585  * Attempt to parse the contents of a buffer as a SSH publickey userauth
 586  * request, checking its contents for consistency and matching the embedded
 587  * key against the one that is being used for signing.
 588  * Note: does not modify msg buffer.
 589  * Optionally extract the username, session ID and/or hostkey from the request.
 590  */
 591 static int
 592 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key,
 593     char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp)
 594 {
 595         struct sshbuf *b = NULL, *sess_id = NULL;
 596         char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL;
 597         int r;
 598         u_char t, sig_follows;
 599         struct sshkey *mkey = NULL, *hostkey = NULL;
 600
 601         if (userp != NULL)
 602                 *userp = NULL;
 603         if (sess_idp != NULL)
 604                 *sess_idp = NULL;
 605         if (hostkeyp != NULL)
 606                 *hostkeyp = NULL;
 607         if ((b = sshbuf_fromb(msg)) == NULL)
 608                 fatal_f("sshbuf_fromb");
 609
 610         /* SSH userauth request */
 611         if ((r = sshbuf_froms(b, &sess_id)) != 0)
 612                 goto out;
 613         if (sshbuf_len(sess_id) == 0) {
 614                 r = SSH_ERR_INVALID_FORMAT;
 615                 goto out;
 616         }
 617         if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */
 618             (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */
 619             (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */
 620             (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */
 621             (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */
 622             (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */
 623             (r = sshkey_froms(b, &mkey)) != 0) /* key */
 624                 goto out;
 625         if (t != SSH2_MSG_USERAUTH_REQUEST ||
 626             sig_follows != 1 ||
 627             strcmp(service, "ssh-connection") != 0 ||
 628             !sshkey_equal(expected_key, mkey) ||
 629             sshkey_type_from_name(pkalg) != expected_key->type) {
 630                 r = SSH_ERR_INVALID_FORMAT;
 631                 goto out;
 632         }
 633         if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) {
 634                 if ((r = sshkey_froms(b, &hostkey)) != 0)
 635                         goto out;
 636         } else if (strcmp(method, "publickey") != 0) {
 637                 r = SSH_ERR_INVALID_FORMAT;
 638                 goto out;
 639         }
 640         if (sshbuf_len(b) != 0) {
 641                 r = SSH_ERR_INVALID_FORMAT;
 642                 goto out;
 643         }
 644         /* success */
 645         r = 0;
 646         debug3_f("well formed userauth");
 647         if (userp != NULL) {
 648                 *userp = user;
 649                 user = NULL;
 650         }
 651         if (sess_idp != NULL) {
 652                 *sess_idp = sess_id;
 653                 sess_id = NULL;
 654         }
 655         if (hostkeyp != NULL) {
 656                 *hostkeyp = hostkey;
 657                 hostkey = NULL;
 658         }
 659  out:
 660         sshbuf_free(b);
 661         sshbuf_free(sess_id);
 662         free(user);
 663         free(service);
 664         free(method);
 665         free(pkalg);
 666         sshkey_free(mkey);
 667         sshkey_free(hostkey);
 668         return r;
 669 }
 670
 671 /*
 672  * Attempt to parse the contents of a buffer as a SSHSIG signature request.
 673  * Note: does not modify buffer.
 674  */
 675 static int
 676 parse_sshsig_request(struct sshbuf *msg)
 677 {
 678         int r;
 679         struct sshbuf *b;
 680
 681         if ((b = sshbuf_fromb(msg)) == NULL)
 682                 fatal_f("sshbuf_fromb");
 683
 684         if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 ||
 685             (r = sshbuf_consume(b, 6)) != 0 ||
 686             (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */
 687             (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */
 688             (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */
 689             (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */
 690                 goto out;
 691         if (sshbuf_len(b) != 0) {
 692                 r = SSH_ERR_INVALID_FORMAT;
 693                 goto out;
 694         }
 695         /* success */
 696         r = 0;
 697  out:
 698         sshbuf_free(b);
 699         return r;
 700 }
 701
 702 /*
 703  * This function inspects a message to be signed by a FIDO key that has a
 704  * web-like application string (i.e. one that does not begin with "ssh:".
 705  * It checks that the message is one of those expected for SSH operations
 706  * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
 707  * for the web.
 708  */
 709 static int
 710 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data)
 711 {
 712         if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) {
 713                 debug_f("signed data matches public key userauth request");
 714                 return 1;
 715         }
 716         if (parse_sshsig_request(data) == 0) {
 717                 debug_f("signed data matches SSHSIG signature request");
 718                 return 1;
 719         }
 720
 721         /* XXX check CA signature operation */
 722
 723         error("web-origin key attempting to sign non-SSH message");
 724         return 0;
 725 }
 726
 727 static int
 728 buf_equal(const struct sshbuf *a, const struct sshbuf *b)
 729 {
 730         if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL)
 731                 return SSH_ERR_INVALID_ARGUMENT;
 732         if (sshbuf_len(a) != sshbuf_len(b))
 733                 return SSH_ERR_INVALID_FORMAT;
 734         if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0)
 735                 return SSH_ERR_INVALID_FORMAT;
 736         return 0;
 737 }
 738
 739 /* ssh2 only */
 740 static void
 741 process_sign_request2(SocketEntry *e)
 742 {
 743         u_char *signature = NULL;
 744         size_t slen = 0;
 745         u_int compat = 0, flags;
 746         int r, ok = -1, retried = 0;
 747         char *fp = NULL, *pin = NULL, *prompt = NULL;
 748         char *user = NULL, *sig_dest = NULL;
 749         const char *fwd_host = NULL, *dest_host = NULL;
 750         struct sshbuf *msg = NULL, *data = NULL, *sid = NULL;
 751         struct sshkey *key = NULL, *hostkey = NULL;
 752         struct identity *id;
 753         struct notifier_ctx *notifier = NULL;
 754
 755         debug_f("entering");
 756
 757         if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL)
 758                 fatal_f("sshbuf_new failed");
 759         if ((r = sshkey_froms(e->request, &key)) != 0 ||
 760             (r = sshbuf_get_stringb(e->request, data)) != 0 ||
 761             (r = sshbuf_get_u32(e->request, &flags)) != 0) {
 762                 error_fr(r, "parse");
 763                 goto send;
 764         }
 765
 766         if ((id = lookup_identity(key)) == NULL) {
 767                 verbose_f("%s key not found", sshkey_type(key));
 768                 goto send;
 769         }
 770         if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
 771             SSH_FP_DEFAULT)) == NULL)
 772                 fatal_f("fingerprint failed");
 773
 774         if (id->ndest_constraints != 0) {
 775                 if (e->nsession_ids == 0) {
 776                         logit_f("refusing use of destination-constrained key "
 777                             "to sign on unbound connection");
 778                         goto send;
 779                 }
 780                 if (parse_userauth_request(data, key, &user, &sid,
 781                     &hostkey) != 0) {
 782                         logit_f("refusing use of destination-constrained key "
 783                            "to sign an unidentified signature");
 784                         goto send;
 785                 }
 786                 /* XXX logspam */
 787                 debug_f("user=%s", user);
 788                 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0)
 789                         goto send;
 790                 /* XXX display fwd_host/dest_host in askpass UI */
 791                 /*
 792                  * Ensure that the session ID is the most recent one
 793                  * registered on the socket - it should have been bound by
 794                  * ssh immediately before userauth.
 795                  */
 796                 if (buf_equal(sid,
 797                     e->session_ids[e->nsession_ids - 1].sid) != 0) {
 798                         error_f("unexpected session ID (%zu listed) on "
 799                             "signature request for target user %s with "
 800                             "key %s %s", e->nsession_ids, user,
 801                             sshkey_type(id->key), fp);
 802                         goto send;
 803                 }
 804                 /*
 805                  * Ensure that the hostkey embedded in the signature matches
 806                  * the one most recently bound to the socket. An exception is
 807                  * made for the initial forwarding hop.
 808                  */
 809                 if (e->nsession_ids > 1 && hostkey == NULL) {
 810                         error_f("refusing use of destination-constrained key: "
 811                             "no hostkey recorded in signature for forwarded "
 812                             "connection");
 813                         goto send;
 814                 }
 815                 if (hostkey != NULL && !sshkey_equal(hostkey,
 816                     e->session_ids[e->nsession_ids - 1].key)) {
 817                         error_f("refusing use of destination-constrained key: "
 818                             "mismatch between hostkey in request and most "
 819                             "recently bound session");
 820                         goto send;
 821                 }
 822                 xasprintf(&sig_dest, "public key authentication request for "
 823                     "user \"%s\" to listed host", user);
 824         }
 825         if (id->confirm && confirm_key(id, sig_dest) != 0) {
 826                 verbose_f("user refused key");
 827                 goto send;
 828         }
 829         if (sshkey_is_sk(id->key)) {
 830                 if (strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
 831                     !check_websafe_message_contents(key, data)) {
 832                         /* error already logged */
 833                         goto send;
 834                 }
 835                 if ((id->key->sk_flags & SSH_SK_USER_VERIFICATION_REQD)) {
 836                         /* XXX include sig_dest */
 837                         xasprintf(&prompt, "Enter PIN%sfor %s key %s: ",
 838                             (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ?
 839                             " and confirm user presence " : " ",
 840                             sshkey_type(id->key), fp);
 841                         pin = read_passphrase(prompt, RP_USE_ASKPASS);
 842                         free(prompt);
 843                         prompt = NULL;
 844                 } else if ((id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) {
 845                         notifier = notify_start(0,
 846                             "Confirm user presence for key %s %s%s%s",
 847                             sshkey_type(id->key), fp,
 848                             sig_dest == NULL ? "" : "\n",
 849                             sig_dest == NULL ? "" : sig_dest);
 850                 }
 851         }
 852  retry_pin:
 853         if ((r = sshkey_sign(id->key, &signature, &slen,
 854             sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags),
 855             id->sk_provider, pin, compat)) != 0) {
 856                 debug_fr(r, "sshkey_sign");
 857                 if (pin == NULL && !retried && sshkey_is_sk(id->key) &&
 858                     r == SSH_ERR_KEY_WRONG_PASSPHRASE) {
 859                         if (notifier) {
 860                                 notify_complete(notifier, NULL);
 861                                 notifier = NULL;
 862                         }
 863                         /* XXX include sig_dest */
 864                         xasprintf(&prompt, "Enter PIN%sfor %s key %s: ",
 865                             (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ?
 866                             " and confirm user presence " : " ",
 867                             sshkey_type(id->key), fp);
 868                         pin = read_passphrase(prompt, RP_USE_ASKPASS);
 869                         retried = 1;
 870                         goto retry_pin;
 871                 }
 872                 error_fr(r, "sshkey_sign");
 873                 goto send;
 874         }
 875         /* Success */
 876         ok = 0;
 877  send:
 878         notify_complete(notifier, "User presence confirmed");
 879
 880         if (ok == 0) {
 881                 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
 882                     (r = sshbuf_put_string(msg, signature, slen)) != 0)
 883                         fatal_fr(r, "compose");
 884         } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
 885                 fatal_fr(r, "compose failure");
 886
 887         if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
 888                 fatal_fr(r, "enqueue");
 889
 890         sshbuf_free(sid);
 891         sshbuf_free(data);
 892         sshbuf_free(msg);
 893         sshkey_free(key);
 894         sshkey_free(hostkey);
 895         free(fp);
 896         free(signature);
 897         free(sig_dest);
 898         free(user);
 899         free(prompt);
 900         if (pin != NULL)
 901                 freezero(pin, strlen(pin));
 902 }
 903
 904 /* shared */
 905 static void
 906 process_remove_identity(SocketEntry *e)
 907 {
 908         int r, success = 0;
 909         struct sshkey *key = NULL;
 910         Identity *id;
 911
 912         debug2_f("entering");
 913         if ((r = sshkey_froms(e->request, &key)) != 0) {
 914                 error_fr(r, "parse key");
 915                 goto done;
 916         }
 917         if ((id = lookup_identity(key)) == NULL) {
 918                 debug_f("key not found");
 919                 goto done;
 920         }
 921         /* identity not visible, cannot be removed */
 922         if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
 923                 goto done; /* error already logged */
 924         /* We have this key, free it. */
 925         if (idtab->nentries < 1)
 926                 fatal_f("internal error: nentries %d", idtab->nentries);
 927         TAILQ_REMOVE(&idtab->idlist, id, next);
 928         free_identity(id);
 929         idtab->nentries--;
 930         success = 1;
 931  done:
 932         sshkey_free(key);
 933         send_status(e, success);
 934 }
 935
 936 static void
 937 process_remove_all_identities(SocketEntry *e)
 938 {
 939         Identity *id;
 940
 941         debug2_f("entering");
 942         /* Loop over all identities and clear the keys. */
 943         for (id = TAILQ_FIRST(&idtab->idlist); id;
 944             id = TAILQ_FIRST(&idtab->idlist)) {
 945                 TAILQ_REMOVE(&idtab->idlist, id, next);
 946                 free_identity(id);
 947         }
 948
 949         /* Mark that there are no identities. */
 950         idtab->nentries = 0;
 951
 952         /* Send success. */
 953         send_status(e, 1);
 954 }
 955
 956 /* removes expired keys and returns number of seconds until the next expiry */
 957 static time_t
 958 reaper(void)
 959 {
 960         time_t deadline = 0, now = monotime();
 961         Identity *id, *nxt;
 962
 963         for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
 964                 nxt = TAILQ_NEXT(id, next);
 965                 if (id->death == 0)
 966                         continue;
 967                 if (now >= id->death) {
 968                         debug("expiring key '%s'", id->comment);
 969                         TAILQ_REMOVE(&idtab->idlist, id, next);
 970                         free_identity(id);
 971                         idtab->nentries--;
 972                 } else
 973                         deadline = (deadline == 0) ? id->death :
 974                             MINIMUM(deadline, id->death);
 975         }
 976         if (deadline == 0 || deadline <= now)
 977                 return 0;
 978         else
 979                 return (deadline - now);
 980 }
 981
 982 static int
 983 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch)
 984 {
 985         u_char key_is_ca;
 986         size_t elen = 0;
 987         int r;
 988         struct sshkey *k = NULL;
 989         char *fp;
 990
 991         memset(dch, '\0', sizeof(*dch));
 992         if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 ||
 993             (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 ||
 994             (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
 995                 error_fr(r, "parse");
 996                 goto out;
 997         }
 998         if (elen != 0) {
 999                 error_f("unsupported extensions (len %zu)", elen);
1000                 r = SSH_ERR_FEATURE_UNSUPPORTED;
1001                 goto out;
1002         }
1003         if (*dch->hostname == '\0') {
1004                 free(dch->hostname);
1005                 dch->hostname = NULL;
1006         }
1007         if (*dch->user == '\0') {
1008                 free(dch->user);
1009                 dch->user = NULL;
1010         }
1011         while (sshbuf_len(b) != 0) {
1012                 dch->keys = xrecallocarray(dch->keys, dch->nkeys,
1013                     dch->nkeys + 1, sizeof(*dch->keys));
1014                 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys,
1015                     dch->nkeys + 1, sizeof(*dch->key_is_ca));
1016                 if ((r = sshkey_froms(b, &k)) != 0 ||
1017                     (r = sshbuf_get_u8(b, &key_is_ca)) != 0)
1018                         goto out;
1019                 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1020                     SSH_FP_DEFAULT)) == NULL)
1021                         fatal_f("fingerprint failed");
1022                 debug3_f("%s%s%s: adding %skey %s %s",
1023                     dch->user == NULL ? "" : dch->user,
1024                     dch->user == NULL ? "" : "@",
1025                     dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp);
1026                 free(fp);
1027                 dch->keys[dch->nkeys] = k;
1028                 dch->key_is_ca[dch->nkeys] = key_is_ca != 0;
1029                 dch->nkeys++;
1030                 k = NULL; /* transferred */
1031         }
1032         /* success */
1033         r = 0;
1034  out:
1035         sshkey_free(k);
1036         return r;
1037 }
1038
1039 static int
1040 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc)
1041 {
1042         struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL;
1043         int r;
1044         size_t elen = 0;
1045
1046         debug3_f("entering");
1047
1048         memset(dc, '\0', sizeof(*dc));
1049         if ((r = sshbuf_froms(m, &b)) != 0 ||
1050             (r = sshbuf_froms(b, &frombuf)) != 0 ||
1051             (r = sshbuf_froms(b, &tobuf)) != 0 ||
1052             (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
1053                 error_fr(r, "parse");
1054                 goto out;
1055         }
1056         if ((r = parse_dest_constraint_hop(frombuf, &dc->from) != 0) ||
1057             (r = parse_dest_constraint_hop(tobuf, &dc->to) != 0))
1058                 goto out; /* already logged */
1059         if (elen != 0) {
1060                 error_f("unsupported extensions (len %zu)", elen);
1061                 r = SSH_ERR_FEATURE_UNSUPPORTED;
1062                 goto out;
1063         }
1064         debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)",
1065             dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys,
1066             dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "",
1067             dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys);
1068         /* check consistency */
1069         if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) ||
1070             dc->from.user != NULL) {
1071                 error_f("inconsistent \"from\" specification");
1072                 r = SSH_ERR_INVALID_FORMAT;
1073                 goto out;
1074         }
1075         if (dc->to.hostname == NULL || dc->to.nkeys == 0) {
1076                 error_f("incomplete \"to\" specification");
1077                 r = SSH_ERR_INVALID_FORMAT;
1078                 goto out;
1079         }
1080         /* success */
1081         r = 0;
1082  out:
1083         sshbuf_free(b);
1084         sshbuf_free(frombuf);
1085         sshbuf_free(tobuf);
1086         return r;
1087 }
1088
1089 static int
1090 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp,
1091     struct dest_constraint **dcsp, size_t *ndcsp)
1092 {
1093         char *ext_name = NULL;
1094         int r;
1095         struct sshbuf *b = NULL;
1096
1097         if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) {
1098                 error_fr(r, "parse constraint extension");
1099                 goto out;
1100         }
1101         debug_f("constraint ext %s", ext_name);
1102         if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
1103                 if (sk_providerp == NULL) {
1104                         error_f("%s not valid here", ext_name);
1105                         r = SSH_ERR_INVALID_FORMAT;
1106                         goto out;
1107                 }
1108                 if (*sk_providerp != NULL) {
1109                         error_f("%s already set", ext_name);
1110                         r = SSH_ERR_INVALID_FORMAT;
1111                         goto out;
1112                 }
1113                 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) {
1114                         error_fr(r, "parse %s", ext_name);
1115                         goto out;
1116                 }
1117         } else if (strcmp(ext_name,
1118             "restrict-destination-v00@openssh.com") == 0) {
1119                 if (*dcsp != NULL) {
1120                         error_f("%s already set", ext_name);
1121                         goto out;
1122                 }
1123                 if ((r = sshbuf_froms(m, &b)) != 0) {
1124                         error_fr(r, "parse %s outer", ext_name);
1125                         goto out;
1126                 }
1127                 while (sshbuf_len(b) != 0) {
1128                         if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) {
1129                                 error_f("too many %s constraints", ext_name);
1130                                 goto out;
1131                         }
1132                         *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1,
1133                             sizeof(**dcsp));
1134                         if ((r = parse_dest_constraint(b,
1135                             *dcsp + (*ndcsp)++)) != 0)
1136                                 goto out; /* error already logged */
1137                 }
1138         } else {
1139                 error_f("unsupported constraint \"%s\"", ext_name);
1140                 r = SSH_ERR_FEATURE_UNSUPPORTED;
1141                 goto out;
1142         }
1143         /* success */
1144         r = 0;
1145  out:
1146         free(ext_name);
1147         sshbuf_free(b);
1148         return r;
1149 }
1150
1151 static int
1152 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp,
1153     u_int *secondsp, int *confirmp, char **sk_providerp,
1154     struct dest_constraint **dcsp, size_t *ndcsp)
1155 {
1156         u_char ctype;
1157         int r;
1158         u_int seconds, maxsign = 0;
1159
1160         while (sshbuf_len(m)) {
1161                 if ((r = sshbuf_get_u8(m, &ctype)) != 0) {
1162                         error_fr(r, "parse constraint type");
1163                         goto out;
1164                 }
1165                 switch (ctype) {
1166                 case SSH_AGENT_CONSTRAIN_LIFETIME:
1167                         if (*deathp != 0) {
1168                                 error_f("lifetime already set");
1169                                 r = SSH_ERR_INVALID_FORMAT;
1170                                 goto out;
1171                         }
1172                         if ((r = sshbuf_get_u32(m, &seconds)) != 0) {
1173                                 error_fr(r, "parse lifetime constraint");
1174                                 goto out;
1175                         }
1176                         *deathp = monotime() + seconds;
1177                         *secondsp = seconds;
1178                         break;
1179                 case SSH_AGENT_CONSTRAIN_CONFIRM:
1180                         if (*confirmp != 0) {
1181                                 error_f("confirm already set");
1182                                 r = SSH_ERR_INVALID_FORMAT;
1183                                 goto out;
1184                         }
1185                         *confirmp = 1;
1186                         break;
1187                 case SSH_AGENT_CONSTRAIN_MAXSIGN:
1188                         if (k == NULL) {
1189                                 error_f("maxsign not valid here");
1190                                 r = SSH_ERR_INVALID_FORMAT;
1191                                 goto out;
1192                         }
1193                         if (maxsign != 0) {
1194                                 error_f("maxsign already set");
1195                                 r = SSH_ERR_INVALID_FORMAT;
1196                                 goto out;
1197                         }
1198                         if ((r = sshbuf_get_u32(m, &maxsign)) != 0) {
1199                                 error_fr(r, "parse maxsign constraint");
1200                                 goto out;
1201                         }
1202                         if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
1203                                 error_fr(r, "enable maxsign");
1204                                 goto out;
1205                         }
1206                         break;
1207                 case SSH_AGENT_CONSTRAIN_EXTENSION:
1208                         if ((r = parse_key_constraint_extension(m,
1209                             sk_providerp, dcsp, ndcsp)) != 0)
1210                                 goto out; /* error already logged */
1211                         break;
1212                 default:
1213                         error_f("Unknown constraint %d", ctype);
1214                         r = SSH_ERR_FEATURE_UNSUPPORTED;
1215                         goto out;
1216                 }
1217         }
1218         /* success */
1219         r = 0;
1220  out:
1221         return r;
1222 }
1223
1224 static void
1225 process_add_identity(SocketEntry *e)
1226 {
1227         Identity *id;
1228         int success = 0, confirm = 0;
1229         char *fp, *comment = NULL, *sk_provider = NULL;
1230         char canonical_provider[PATH_MAX];
1231         time_t death = 0;
1232         u_int seconds = 0;
1233         struct dest_constraint *dest_constraints = NULL;
1234         size_t ndest_constraints = 0;
1235         struct sshkey *k = NULL;
1236         int r = SSH_ERR_INTERNAL_ERROR;
1237
1238         debug2_f("entering");
1239         if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
1240             k == NULL ||
1241             (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
1242                 error_fr(r, "parse");
1243                 goto out;
1244         }
1245         if (parse_key_constraints(e->request, k, &death, &seconds, &confirm,
1246             &sk_provider, &dest_constraints, &ndest_constraints) != 0) {
1247                 error_f("failed to parse constraints");
1248                 sshbuf_reset(e->request);
1249                 goto out;
1250         }
1251
1252         if (sk_provider != NULL) {
1253                 if (!sshkey_is_sk(k)) {
1254                         error("Cannot add provider: %s is not an "
1255                             "authenticator-hosted key", sshkey_type(k));
1256                         goto out;
1257                 }
1258                 if (strcasecmp(sk_provider, "internal") == 0) {
1259                         debug_f("internal provider");
1260                 } else {
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 (realpath(provider, canonical_provider) == NULL) {
1425                 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1426                     provider, strerror(errno));
1427                 goto send;
1428         }
1429         if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
1430                 verbose("refusing PKCS#11 add of \"%.100s\": "
1431                     "provider not allowed", canonical_provider);
1432                 goto send;
1433         }
1434         debug_f("add %.100s", canonical_provider);
1435         if (lifetime && !death)
1436                 death = monotime() + lifetime;
1437
1438         count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
1439         for (i = 0; i < count; i++) {
1440                 k = keys[i];
1441                 if (lookup_identity(k) == NULL) {
1442                         id = xcalloc(1, sizeof(Identity));
1443                         id->key = k;
1444                         keys[i] = NULL; /* transferred */
1445                         id->provider = xstrdup(canonical_provider);
1446                         if (*comments[i] != '\0') {
1447                                 id->comment = comments[i];
1448                                 comments[i] = NULL; /* transferred */
1449                         } else {
1450                                 id->comment = xstrdup(canonical_provider);
1451                         }
1452                         id->death = death;
1453                         id->confirm = confirm;
1454                         id->dest_constraints = dest_constraints;
1455                         id->ndest_constraints = ndest_constraints;
1456                         dest_constraints = NULL; /* transferred */
1457                         ndest_constraints = 0;
1458                         TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1459                         idtab->nentries++;
1460                         success = 1;
1461                 }
1462                 /* XXX update constraints for existing keys */
1463                 sshkey_free(keys[i]);
1464                 free(comments[i]);
1465         }
1466 send:
1467         free(pin);
1468         free(provider);
1469         free(keys);
1470         free(comments);
1471         free_dest_constraints(dest_constraints, ndest_constraints);
1472         send_status(e, success);
1473 }
1474
1475 static void
1476 process_remove_smartcard_key(SocketEntry *e)
1477 {
1478         char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1479         int r, success = 0;
1480         Identity *id, *nxt;
1481
1482         debug2_f("entering");
1483         if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1484             (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1485                 error_fr(r, "parse");
1486                 goto send;
1487         }
1488         free(pin);
1489
1490         if (realpath(provider, canonical_provider) == NULL) {
1491                 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1492                     provider, strerror(errno));
1493                 goto send;
1494         }
1495
1496         debug_f("remove %.100s", canonical_provider);
1497         for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
1498                 nxt = TAILQ_NEXT(id, next);
1499                 /* Skip file--based keys */
1500                 if (id->provider == NULL)
1501                         continue;
1502                 if (!strcmp(canonical_provider, id->provider)) {
1503                         TAILQ_REMOVE(&idtab->idlist, id, next);
1504                         free_identity(id);
1505                         idtab->nentries--;
1506                 }
1507         }
1508         if (pkcs11_del_provider(canonical_provider) == 0)
1509                 success = 1;
1510         else
1511                 error_f("pkcs11_del_provider failed");
1512 send:
1513         free(provider);
1514         send_status(e, success);
1515 }
1516 #endif /* ENABLE_PKCS11 */
1517
1518 static int
1519 process_ext_session_bind(SocketEntry *e)
1520 {
1521         int r, sid_match, key_match;
1522         struct sshkey *key = NULL;
1523         struct sshbuf *sid = NULL, *sig = NULL;
1524         char *fp = NULL;
1525         size_t i;
1526         u_char fwd = 0;
1527
1528         debug2_f("entering");
1529         if ((r = sshkey_froms(e->request, &key)) != 0 ||
1530             (r = sshbuf_froms(e->request, &sid)) != 0 ||
1531             (r = sshbuf_froms(e->request, &sig)) != 0 ||
1532             (r = sshbuf_get_u8(e->request, &fwd)) != 0) {
1533                 error_fr(r, "parse");
1534                 goto out;
1535         }
1536         if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
1537             SSH_FP_DEFAULT)) == NULL)
1538                 fatal_f("fingerprint failed");
1539         /* check signature with hostkey on session ID */
1540         if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig),
1541             sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) {
1542                 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp);
1543                 goto out;
1544         }
1545         /* check whether sid/key already recorded */
1546         for (i = 0; i < e->nsession_ids; i++) {
1547                 if (!e->session_ids[i].forwarded) {
1548                         error_f("attempt to bind session ID to socket "
1549                             "previously bound for authentication attempt");
1550                         r = -1;
1551                         goto out;
1552                 }
1553                 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0;
1554                 key_match = sshkey_equal(key, e->session_ids[i].key);
1555                 if (sid_match && key_match) {
1556                         debug_f("session ID already recorded for %s %s",
1557                             sshkey_type(key), fp);
1558                         r = 0;
1559                         goto out;
1560                 } else if (sid_match) {
1561                         error_f("session ID recorded against different key "
1562                             "for %s %s", sshkey_type(key), fp);
1563                         r = -1;
1564                         goto out;
1565                 }
1566                 /*
1567                  * new sid with previously-seen key can happen, e.g. multiple
1568                  * connections to the same host.
1569                  */
1570         }
1571         /* record new key/sid */
1572         if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) {
1573                 error_f("too many session IDs recorded");
1574                 goto out;
1575         }
1576         e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids,
1577             e->nsession_ids + 1, sizeof(*e->session_ids));
1578         i = e->nsession_ids++;
1579         debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i,
1580             AGENT_MAX_SESSION_IDS);
1581         e->session_ids[i].key = key;
1582         e->session_ids[i].forwarded = fwd != 0;
1583         key = NULL; /* transferred */
1584         /* can't transfer sid; it's refcounted and scoped to request's life */
1585         if ((e->session_ids[i].sid = sshbuf_new()) == NULL)
1586                 fatal_f("sshbuf_new");
1587         if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0)
1588                 fatal_fr(r, "sshbuf_putb session ID");
1589         /* success */
1590         r = 0;
1591  out:
1592         sshkey_free(key);
1593         sshbuf_free(sid);
1594         sshbuf_free(sig);
1595         return r == 0 ? 1 : 0;
1596 }
1597
1598 static void
1599 process_extension(SocketEntry *e)
1600 {
1601         int r, success = 0;
1602         char *name;
1603
1604         debug2_f("entering");
1605         if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) {
1606                 error_fr(r, "parse");
1607                 goto send;
1608         }
1609         if (strcmp(name, "session-bind@openssh.com") == 0)
1610                 success = process_ext_session_bind(e);
1611         else
1612                 debug_f("unsupported extension \"%s\"", name);
1613         free(name);
1614 send:
1615         send_status(e, success);
1616 }
1617 /*
1618  * dispatch incoming message.
1619  * returns 1 on success, 0 for incomplete messages or -1 on error.
1620  */
1621 static int
1622 process_message(u_int socknum)
1623 {
1624         u_int msg_len;
1625         u_char type;
1626         const u_char *cp;
1627         int r;
1628         SocketEntry *e;
1629
1630         if (socknum >= sockets_alloc)
1631                 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
1632         e = &sockets[socknum];
1633
1634         if (sshbuf_len(e->input) < 5)
1635                 return 0;               /* Incomplete message header. */
1636         cp = sshbuf_ptr(e->input);
1637         msg_len = PEEK_U32(cp);
1638         if (msg_len > AGENT_MAX_LEN) {
1639                 debug_f("socket %u (fd=%d) message too long %u > %u",
1640                     socknum, e->fd, msg_len, AGENT_MAX_LEN);
1641                 return -1;
1642         }
1643         if (sshbuf_len(e->input) < msg_len + 4)
1644                 return 0;               /* Incomplete message body. */
1645
1646         /* move the current input to e->request */
1647         sshbuf_reset(e->request);
1648         if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
1649             (r = sshbuf_get_u8(e->request, &type)) != 0) {
1650                 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
1651                     r == SSH_ERR_STRING_TOO_LARGE) {
1652                         error_fr(r, "parse");
1653                         return -1;
1654                 }
1655                 fatal_fr(r, "parse");
1656         }
1657
1658         debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
1659
1660         /* check whether agent is locked */
1661         if (locked && type != SSH_AGENTC_UNLOCK) {
1662                 sshbuf_reset(e->request);
1663                 switch (type) {
1664                 case SSH2_AGENTC_REQUEST_IDENTITIES:
1665                         /* send empty lists */
1666                         no_identities(e);
1667                         break;
1668                 default:
1669                         /* send a fail message for all other request types */
1670                         send_status(e, 0);
1671                 }
1672                 return 1;
1673         }
1674
1675         switch (type) {
1676         case SSH_AGENTC_LOCK:
1677         case SSH_AGENTC_UNLOCK:
1678                 process_lock_agent(e, type == SSH_AGENTC_LOCK);
1679                 break;
1680         case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
1681                 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
1682                 break;
1683         /* ssh2 */
1684         case SSH2_AGENTC_SIGN_REQUEST:
1685                 process_sign_request2(e);
1686                 break;
1687         case SSH2_AGENTC_REQUEST_IDENTITIES:
1688                 process_request_identities(e);
1689                 break;
1690         case SSH2_AGENTC_ADD_IDENTITY:
1691         case SSH2_AGENTC_ADD_ID_CONSTRAINED:
1692                 process_add_identity(e);
1693                 break;
1694         case SSH2_AGENTC_REMOVE_IDENTITY:
1695                 process_remove_identity(e);
1696                 break;
1697         case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
1698                 process_remove_all_identities(e);
1699                 break;
1700 #ifdef ENABLE_PKCS11
1701         case SSH_AGENTC_ADD_SMARTCARD_KEY:
1702         case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
1703                 process_add_smartcard_key(e);
1704                 break;
1705         case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
1706                 process_remove_smartcard_key(e);
1707                 break;
1708 #endif /* ENABLE_PKCS11 */
1709         case SSH_AGENTC_EXTENSION:
1710                 process_extension(e);
1711                 break;
1712         default:
1713                 /* Unknown message.  Respond with failure. */
1714                 error("Unknown message %d", type);
1715                 sshbuf_reset(e->request);
1716                 send_status(e, 0);
1717                 break;
1718         }
1719         return 1;
1720 }
1721
1722 static void
1723 new_socket(sock_type type, int fd)
1724 {
1725         u_int i, old_alloc, new_alloc;
1726
1727         debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" :
1728             (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN"));
1729         if (type == AUTH_CONNECTION) {
1730                 debug("xcount %d -> %d", xcount, xcount + 1);
1731                 ++xcount;
1732         }
1733         set_nonblock(fd);
1734
1735         if (fd > max_fd)
1736                 max_fd = fd;
1737
1738         for (i = 0; i < sockets_alloc; i++)
1739                 if (sockets[i].type == AUTH_UNUSED) {
1740                         sockets[i].fd = fd;
1741                         if ((sockets[i].input = sshbuf_new()) == NULL ||
1742                             (sockets[i].output = sshbuf_new()) == NULL ||
1743                             (sockets[i].request = sshbuf_new()) == NULL)
1744                                 fatal_f("sshbuf_new failed");
1745                         sockets[i].type = type;
1746                         return;
1747                 }
1748         old_alloc = sockets_alloc;
1749         new_alloc = sockets_alloc + 10;
1750         sockets = xrecallocarray(sockets, old_alloc, new_alloc,
1751             sizeof(sockets[0]));
1752         for (i = old_alloc; i < new_alloc; i++)
1753                 sockets[i].type = AUTH_UNUSED;
1754         sockets_alloc = new_alloc;
1755         sockets[old_alloc].fd = fd;
1756         if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
1757             (sockets[old_alloc].output = sshbuf_new()) == NULL ||
1758             (sockets[old_alloc].request = sshbuf_new()) == NULL)
1759                 fatal_f("sshbuf_new failed");
1760         sockets[old_alloc].type = type;
1761 }
1762
1763 static int
1764 handle_socket_read(u_int socknum)
1765 {
1766         struct sockaddr_un sunaddr;
1767         socklen_t slen;
1768         uid_t euid;
1769         gid_t egid;
1770         int fd;
1771
1772         slen = sizeof(sunaddr);
1773         fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
1774         if (fd == -1) {
1775                 error("accept from AUTH_SOCKET: %s", strerror(errno));
1776                 return -1;
1777         }
1778         if (getpeereid(fd, &euid, &egid) == -1) {
1779                 error("getpeereid %d failed: %s", fd, strerror(errno));
1780                 close(fd);
1781                 return -1;
1782         }
1783         if ((euid != 0) && (getuid() != euid)) {
1784                 error("uid mismatch: peer euid %u != uid %u",
1785                     (u_int) euid, (u_int) getuid());
1786                 close(fd);
1787                 return -1;
1788         }
1789         new_socket(AUTH_CONNECTION, fd);
1790         return 0;
1791 }
1792
1793 static int
1794 handle_conn_read(u_int socknum)
1795 {
1796         char buf[AGENT_RBUF_LEN];
1797         ssize_t len;
1798         int r;
1799
1800         if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
1801                 if (len == -1) {
1802                         if (errno == EAGAIN || errno == EINTR)
1803                                 return 0;
1804                         error_f("read error on socket %u (fd %d): %s",
1805                             socknum, sockets[socknum].fd, strerror(errno));
1806                 }
1807                 return -1;
1808         }
1809         if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
1810                 fatal_fr(r, "compose");
1811         explicit_bzero(buf, sizeof(buf));
1812         for (;;) {
1813                 if ((r = process_message(socknum)) == -1)
1814                         return -1;
1815                 else if (r == 0)
1816                         break;
1817         }
1818         return 0;
1819 }
1820
1821 static int
1822 handle_conn_write(u_int socknum)
1823 {
1824         ssize_t len;
1825         int r;
1826
1827         if (sshbuf_len(sockets[socknum].output) == 0)
1828                 return 0; /* shouldn't happen */
1829         if ((len = write(sockets[socknum].fd,
1830             sshbuf_ptr(sockets[socknum].output),
1831             sshbuf_len(sockets[socknum].output))) <= 0) {
1832                 if (len == -1) {
1833                         if (errno == EAGAIN || errno == EINTR)
1834                                 return 0;
1835                         error_f("read error on socket %u (fd %d): %s",
1836                             socknum, sockets[socknum].fd, strerror(errno));
1837                 }
1838                 return -1;
1839         }
1840         if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
1841                 fatal_fr(r, "consume");
1842         return 0;
1843 }
1844
1845 static void
1846 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
1847 {
1848         size_t i;
1849         u_int socknum, activefds = npfd;
1850
1851         for (i = 0; i < npfd; i++) {
1852                 if (pfd[i].revents == 0)
1853                         continue;
1854                 /* Find sockets entry */
1855                 for (socknum = 0; socknum < sockets_alloc; socknum++) {
1856                         if (sockets[socknum].type != AUTH_SOCKET &&
1857                             sockets[socknum].type != AUTH_CONNECTION)
1858                                 continue;
1859                         if (pfd[i].fd == sockets[socknum].fd)
1860                                 break;
1861                 }
1862                 if (socknum >= sockets_alloc) {
1863                         error_f("no socket for fd %d", pfd[i].fd);
1864                         continue;
1865                 }
1866                 /* Process events */
1867                 switch (sockets[socknum].type) {
1868                 case AUTH_SOCKET:
1869                         if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
1870                                 break;
1871                         if (npfd > maxfds) {
1872                                 debug3("out of fds (active %u >= limit %u); "
1873                                     "skipping accept", activefds, maxfds);
1874                                 break;
1875                         }
1876                         if (handle_socket_read(socknum) == 0)
1877                                 activefds++;
1878                         break;
1879                 case AUTH_CONNECTION:
1880                         if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 &&
1881                             handle_conn_read(socknum) != 0)
1882                                 goto close_sock;
1883                         if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
1884                             handle_conn_write(socknum) != 0) {
1885  close_sock:
1886                                 if (activefds == 0)
1887                                         fatal("activefds == 0 at close_sock");
1888                                 close_socket(&sockets[socknum]);
1889                                 activefds--;
1890                                 break;
1891                         }
1892                         break;
1893                 default:
1894                         break;
1895                 }
1896         }
1897 }
1898
1899 static int
1900 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
1901 {
1902         struct pollfd *pfd = *pfdp;
1903         size_t i, j, npfd = 0;
1904         time_t deadline;
1905         int r;
1906
1907         /* Count active sockets */
1908         for (i = 0; i < sockets_alloc; i++) {
1909                 switch (sockets[i].type) {
1910                 case AUTH_SOCKET:
1911                 case AUTH_CONNECTION:
1912                         npfd++;
1913                         break;
1914                 case AUTH_UNUSED:
1915                         break;
1916                 default:
1917                         fatal("Unknown socket type %d", sockets[i].type);
1918                         break;
1919                 }
1920         }
1921         if (npfd != *npfdp &&
1922             (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
1923                 fatal_f("recallocarray failed");
1924         *pfdp = pfd;
1925         *npfdp = npfd;
1926
1927         for (i = j = 0; i < sockets_alloc; i++) {
1928                 switch (sockets[i].type) {
1929                 case AUTH_SOCKET:
1930                         if (npfd > maxfds) {
1931                                 debug3("out of fds (active %zu >= limit %u); "
1932                                     "skipping arming listener", npfd, maxfds);
1933                                 break;
1934                         }
1935                         pfd[j].fd = sockets[i].fd;
1936                         pfd[j].revents = 0;
1937                         pfd[j].events = POLLIN;
1938                         j++;
1939                         break;
1940                 case AUTH_CONNECTION:
1941                         pfd[j].fd = sockets[i].fd;
1942                         pfd[j].revents = 0;
1943                         /*
1944                          * Only prepare to read if we can handle a full-size
1945                          * input read buffer and enqueue a max size reply..
1946                          */
1947                         if ((r = sshbuf_check_reserve(sockets[i].input,
1948                             AGENT_RBUF_LEN)) == 0 &&
1949                             (r = sshbuf_check_reserve(sockets[i].output,
1950                             AGENT_MAX_LEN)) == 0)
1951                                 pfd[j].events = POLLIN;
1952                         else if (r != SSH_ERR_NO_BUFFER_SPACE)
1953                                 fatal_fr(r, "reserve");
1954                         if (sshbuf_len(sockets[i].output) > 0)
1955                                 pfd[j].events |= POLLOUT;
1956                         j++;
1957                         break;
1958                 default:
1959                         break;
1960                 }
1961         }
1962         deadline = reaper();
1963         if (parent_alive_interval != 0)
1964                 deadline = (deadline == 0) ? parent_alive_interval :
1965                     MINIMUM(deadline, parent_alive_interval);
1966         if (deadline == 0) {
1967                 *timeoutp = -1; /* INFTIM */
1968         } else {
1969                 if (deadline > INT_MAX / 1000)
1970                         *timeoutp = INT_MAX / 1000;
1971                 else
1972                         *timeoutp = deadline * 1000;
1973         }
1974         return (1);
1975 }
1976
1977 static void
1978 cleanup_socket(void)
1979 {
1980         if (cleanup_pid != 0 && getpid() != cleanup_pid)
1981                 return;
1982         debug_f("cleanup");
1983         if (socket_name[0])
1984                 unlink(socket_name);
1985         if (socket_dir[0])
1986                 rmdir(socket_dir);
1987 }
1988
1989 void
1990 cleanup_exit(int i)
1991 {
1992         cleanup_socket();
1993         _exit(i);
1994 }
1995
1996 /*ARGSUSED*/
1997 static void
1998 cleanup_handler(int sig)
1999 {
2000         cleanup_socket();
2001 #ifdef ENABLE_PKCS11
2002         pkcs11_terminate();
2003 #endif
2004         _exit(2);
2005 }
2006
2007 static void
2008 check_parent_exists(void)
2009 {
2010         /*
2011          * If our parent has exited then getppid() will return (pid_t)1,
2012          * so testing for that should be safe.
2013          */
2014         if (parent_pid != -1 && getppid() != parent_pid) {
2015                 /* printf("Parent has died - Authentication agent exiting.\n"); */
2016                 cleanup_socket();
2017                 _exit(2);
2018         }
2019 }
2020
2021 static void
2022 usage(void)
2023 {
2024         fprintf(stderr,
2025             "usage: ssh-agent [-c | -s] [-Ddx] [-a bind_address] [-E fingerprint_hash]\n"
2026             "                 [-P allowed_providers] [-t life]\n"
2027             "       ssh-agent [-a bind_address] [-E fingerprint_hash] [-P allowed_providers]\n"
2028             "                 [-t life] command [arg ...]\n"
2029             "       ssh-agent [-c | -s] -k\n");
2030         exit(1);
2031 }
2032
2033 int
2034 main(int ac, char **av)
2035 {
2036         int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
2037         int sock, ch, result, saved_errno;
2038         char *shell, *format, *pidstr, *agentsocket = NULL;
2039 #ifdef HAVE_SETRLIMIT
2040         struct rlimit rlim;
2041 #endif
2042         extern int optind;
2043         extern char *optarg;
2044         pid_t pid;
2045         char pidstrbuf[1 + 3 * sizeof pid];
2046         size_t len;
2047         mode_t prev_mask;
2048         int timeout = -1; /* INFTIM */
2049         struct pollfd *pfd = NULL;
2050         size_t npfd = 0;
2051         u_int maxfds;
2052
2053         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
2054         sanitise_stdfd();
2055
2056         /* drop */
2057         setegid(getgid());
2058         setgid(getgid());
2059         setuid(geteuid());
2060
2061         platform_disable_tracing(0);    /* strict=no */
2062
2063 #ifdef RLIMIT_NOFILE
2064         if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
2065                 fatal("%s: getrlimit: %s", __progname, strerror(errno));
2066 #endif
2067
2068         __progname = ssh_get_progname(av[0]);
2069         seed_rng();
2070
2071         while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:x")) != -1) {
2072                 switch (ch) {
2073                 case 'E':
2074                         fingerprint_hash = ssh_digest_alg_by_name(optarg);
2075                         if (fingerprint_hash == -1)
2076                                 fatal("Invalid hash algorithm \"%s\"", optarg);
2077                         break;
2078                 case 'c':
2079                         if (s_flag)
2080                                 usage();
2081                         c_flag++;
2082                         break;
2083                 case 'k':
2084                         k_flag++;
2085                         break;
2086                 case 'O':
2087                         if (strcmp(optarg, "no-restrict-websafe") == 0)
2088                                 restrict_websafe  = 0;
2089                         else
2090                                 fatal("Unknown -O option");
2091                         break;
2092                 case 'P':
2093                         if (allowed_providers != NULL)
2094                                 fatal("-P option already specified");
2095                         allowed_providers = xstrdup(optarg);
2096                         break;
2097                 case 's':
2098                         if (c_flag)
2099                                 usage();
2100                         s_flag++;
2101                         break;
2102                 case 'd':
2103                         if (d_flag || D_flag)
2104                                 usage();
2105                         d_flag++;
2106                         break;
2107                 case 'D':
2108                         if (d_flag || D_flag)
2109                                 usage();
2110                         D_flag++;
2111                         break;
2112                 case 'a':
2113                         agentsocket = optarg;
2114                         break;
2115                 case 't':
2116                         if ((lifetime = convtime(optarg)) == -1) {
2117                                 fprintf(stderr, "Invalid lifetime\n");
2118                                 usage();
2119                         }
2120                         break;
2121                 case 'x':
2122                         xcount = 0;
2123                         break;
2124                 default:
2125                         usage();
2126                 }
2127         }
2128         ac -= optind;
2129         av += optind;
2130
2131         if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
2132                 usage();
2133
2134         if (allowed_providers == NULL)
2135                 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
2136
2137         if (ac == 0 && !c_flag && !s_flag) {
2138                 shell = getenv("SHELL");
2139                 if (shell != NULL && (len = strlen(shell)) > 2 &&
2140                     strncmp(shell + len - 3, "csh", 3) == 0)
2141                         c_flag = 1;
2142         }
2143         if (k_flag) {
2144                 const char *errstr = NULL;
2145
2146                 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
2147                 if (pidstr == NULL) {
2148                         fprintf(stderr, "%s not set, cannot kill agent\n",
2149                             SSH_AGENTPID_ENV_NAME);
2150                         exit(1);
2151                 }
2152                 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
2153                 if (errstr) {
2154                         fprintf(stderr,
2155                             "%s=\"%s\", which is not a good PID: %s\n",
2156                             SSH_AGENTPID_ENV_NAME, pidstr, errstr);
2157                         exit(1);
2158                 }
2159                 if (kill(pid, SIGTERM) == -1) {
2160                         perror("kill");
2161                         exit(1);
2162                 }
2163                 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
2164                 printf(format, SSH_AUTHSOCKET_ENV_NAME);
2165                 printf(format, SSH_AGENTPID_ENV_NAME);
2166                 printf("echo Agent pid %ld killed;\n", (long)pid);
2167                 exit(0);
2168         }
2169
2170         /*
2171          * Minimum file descriptors:
2172          * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
2173          * a few spare for libc / stack protectors / sanitisers, etc.
2174          */
2175 #define SSH_AGENT_MIN_FDS (3+1+1+1+4)
2176         if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
2177                 fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
2178                     __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
2179         maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
2180
2181         parent_pid = getpid();
2182
2183         if (agentsocket == NULL) {
2184                 /* Create private directory for agent socket */
2185                 mktemp_proto(socket_dir, sizeof(socket_dir));
2186                 if (mkdtemp(socket_dir) == NULL) {
2187                         perror("mkdtemp: private socket dir");
2188                         exit(1);
2189                 }
2190                 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
2191                     (long)parent_pid);
2192         } else {
2193                 /* Try to use specified agent socket */
2194                 socket_dir[0] = '\0';
2195                 strlcpy(socket_name, agentsocket, sizeof socket_name);
2196         }
2197
2198         /*
2199          * Create socket early so it will exist before command gets run from
2200          * the parent.
2201          */
2202         prev_mask = umask(0177);
2203         sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
2204         if (sock < 0) {
2205                 /* XXX - unix_listener() calls error() not perror() */
2206                 *socket_name = '\0'; /* Don't unlink any existing file */
2207                 cleanup_exit(1);
2208         }
2209         umask(prev_mask);
2210
2211         /*
2212          * Fork, and have the parent execute the command, if any, or present
2213          * the socket data.  The child continues as the authentication agent.
2214          */
2215         if (D_flag || d_flag) {
2216                 log_init(__progname,
2217                     d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
2218                     SYSLOG_FACILITY_AUTH, 1);
2219                 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2220                 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2221                     SSH_AUTHSOCKET_ENV_NAME);
2222                 printf("echo Agent pid %ld;\n", (long)parent_pid);
2223                 fflush(stdout);
2224                 goto skip;
2225         }
2226         pid = fork();
2227         if (pid == -1) {
2228                 perror("fork");
2229                 cleanup_exit(1);
2230         }
2231         if (pid != 0) {         /* Parent - execute the given command. */
2232                 close(sock);
2233                 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
2234                 if (ac == 0) {
2235                         format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2236                         printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2237                             SSH_AUTHSOCKET_ENV_NAME);
2238                         printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
2239                             SSH_AGENTPID_ENV_NAME);
2240                         printf("echo Agent pid %ld;\n", (long)pid);
2241                         exit(0);
2242                 }
2243                 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
2244                     setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
2245                         perror("setenv");
2246                         exit(1);
2247                 }
2248                 execvp(av[0], av);
2249                 perror(av[0]);
2250                 exit(1);
2251         }
2252         /* child */
2253         log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
2254
2255         if (setsid() == -1) {
2256                 error("setsid: %s", strerror(errno));
2257                 cleanup_exit(1);
2258         }
2259
2260         (void)chdir("/");
2261         if (stdfd_devnull(1, 1, 1) == -1)
2262                 error_f("stdfd_devnull failed");
2263
2264 #ifdef HAVE_SETRLIMIT
2265         /* deny core dumps, since memory contains unencrypted private keys */
2266         rlim.rlim_cur = rlim.rlim_max = 0;
2267         if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
2268                 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
2269                 cleanup_exit(1);
2270         }
2271 #endif
2272
2273 skip:
2274
2275         cleanup_pid = getpid();
2276
2277 #ifdef ENABLE_PKCS11
2278         pkcs11_init(0);
2279 #endif
2280         new_socket(AUTH_SOCKET, sock);
2281         if (ac > 0)
2282                 parent_alive_interval = 10;
2283         idtab_init();
2284         ssh_signal(SIGPIPE, SIG_IGN);
2285         ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
2286         ssh_signal(SIGHUP, cleanup_handler);
2287         ssh_signal(SIGTERM, cleanup_handler);
2288
2289         if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
2290                 fatal("%s: pledge: %s", __progname, strerror(errno));
2291         platform_pledge_agent();
2292
2293         while (1) {
2294                 prepare_poll(&pfd, &npfd, &timeout, maxfds);
2295                 result = poll(pfd, npfd, timeout);
2296                 saved_errno = errno;
2297                 if (parent_alive_interval != 0)
2298                         check_parent_exists();
2299                 (void) reaper();        /* remove expired keys */
2300                 if (result == -1) {
2301                         if (saved_errno == EINTR)
2302                                 continue;
2303                         fatal("poll: %s", strerror(saved_errno));
2304                 } else if (result > 0)
2305                         after_poll(pfd, npfd, maxfds);
2306         }
2307         /* NOTREACHED */
2308 }