crypto/openssh/ssh_api.c

   1 /* $OpenBSD: ssh_api.c,v 1.7 2016/05/04 14:22:33 markus Exp $ */
   2 /*
   3  * Copyright (c) 2012 Markus Friedl.  All rights reserved.
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 #include "includes.h"
  19
  20 #include "ssh_api.h"
  21 #include "compat.h"
  22 #include "log.h"
  23 #include "authfile.h"
  24 #include "sshkey.h"
  25 #include "misc.h"
  26 #include "ssh2.h"
  27 #include "version.h"
  28 #include "myproposal.h"
  29 #include "ssherr.h"
  30 #include "sshbuf.h"
  31
  32 #include <string.h>
  33
  34 int     _ssh_exchange_banner(struct ssh *);
  35 int     _ssh_send_banner(struct ssh *, char **);
  36 int     _ssh_read_banner(struct ssh *, char **);
  37 int     _ssh_order_hostkeyalgs(struct ssh *);
  38 int     _ssh_verify_host_key(struct sshkey *, struct ssh *);
  39 struct sshkey *_ssh_host_public_key(int, int, struct ssh *);
  40 struct sshkey *_ssh_host_private_key(int, int, struct ssh *);
  41 int     _ssh_host_key_sign(struct sshkey *, struct sshkey *,
  42     u_char **, size_t *, const u_char *, size_t, const char *, u_int);
  43
  44 /*
  45  * stubs for the server side implementation of kex.
  46  * disable privsep so our stubs will never be called.
  47  */
  48 int     use_privsep = 0;
  49 int     mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
  50     u_char *, u_int, char *, u_int);
  51 DH      *mm_choose_dh(int, int, int);
  52
  53 /* Define these two variables here so that they are part of the library */
  54 u_char *session_id2 = NULL;
  55 u_int session_id2_len = 0;
  56
  57 int
  58 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
  59     u_char *data, u_int datalen, char *alg, u_int compat)
  60 {
  61         return (-1);
  62 }
  63
  64 DH *
  65 mm_choose_dh(int min, int nbits, int max)
  66 {
  67         return (NULL);
  68 }
  69
  70 /* API */
  71
  72 int
  73 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
  74 {
  75         char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
  76         struct ssh *ssh;
  77         char **proposal;
  78         static int called;
  79         int r;
  80
  81         if (!called) {
  82 #ifdef WITH_OPENSSL
  83                 OpenSSL_add_all_algorithms();
  84 #endif /* WITH_OPENSSL */
  85                 called = 1;
  86         }
  87
  88         if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)
  89                 return SSH_ERR_ALLOC_FAIL;
  90         if (is_server)
  91                 ssh_packet_set_server(ssh);
  92
  93         /* Initialize key exchange */
  94         proposal = kex_params ? kex_params->proposal : myproposal;
  95         if ((r = kex_new(ssh, proposal, &ssh->kex)) != 0) {
  96                 ssh_free(ssh);
  97                 return r;
  98         }
  99         ssh->kex->server = is_server;
 100         if (is_server) {
 101 #ifdef WITH_OPENSSL
 102                 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
 103                 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
 104                 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server;
 105                 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server;
 106                 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_server;
 107                 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
 108                 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
 109 # ifdef OPENSSL_HAS_ECC
 110                 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server;
 111 # endif
 112 #endif /* WITH_OPENSSL */
 113                 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server;
 114                 ssh->kex->load_host_public_key=&_ssh_host_public_key;
 115                 ssh->kex->load_host_private_key=&_ssh_host_private_key;
 116                 ssh->kex->sign=&_ssh_host_key_sign;
 117         } else {
 118 #ifdef WITH_OPENSSL
 119                 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
 120                 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
 121                 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client;
 122                 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client;
 123                 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client;
 124                 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
 125                 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 126 # ifdef OPENSSL_HAS_ECC
 127                 ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
 128 # endif
 129 #endif /* WITH_OPENSSL */
 130                 ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client;
 131                 ssh->kex->verify_host_key =&_ssh_verify_host_key;
 132         }
 133         *sshp = ssh;
 134         return 0;
 135 }
 136
 137 void
 138 ssh_free(struct ssh *ssh)
 139 {
 140         struct key_entry *k;
 141
 142         ssh_packet_close(ssh);
 143         /*
 144          * we've only created the public keys variants in case we
 145          * are a acting as a server.
 146          */
 147         while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
 148                 TAILQ_REMOVE(&ssh->public_keys, k, next);
 149                 if (ssh->kex && ssh->kex->server)
 150                         sshkey_free(k->key);
 151                 free(k);
 152         }
 153         while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
 154                 TAILQ_REMOVE(&ssh->private_keys, k, next);
 155                 free(k);
 156         }
 157         if (ssh->kex)
 158                 kex_free(ssh->kex);
 159         free(ssh);
 160 }
 161
 162 void
 163 ssh_set_app_data(struct ssh *ssh, void *app_data)
 164 {
 165         ssh->app_data = app_data;
 166 }
 167
 168 void *
 169 ssh_get_app_data(struct ssh *ssh)
 170 {
 171         return ssh->app_data;
 172 }
 173
 174 /* Returns < 0 on error, 0 otherwise */
 175 int
 176 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
 177 {
 178         struct sshkey *pubkey = NULL;
 179         struct key_entry *k = NULL, *k_prv = NULL;
 180         int r;
 181
 182         if (ssh->kex->server) {
 183                 if ((r = sshkey_from_private(key, &pubkey)) != 0)
 184                         return r;
 185                 if ((k = malloc(sizeof(*k))) == NULL ||
 186                     (k_prv = malloc(sizeof(*k_prv))) == NULL) {
 187                         free(k);
 188                         sshkey_free(pubkey);
 189                         return SSH_ERR_ALLOC_FAIL;
 190                 }
 191                 k_prv->key = key;
 192                 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
 193
 194                 /* add the public key, too */
 195                 k->key = pubkey;
 196                 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
 197                 r = 0;
 198         } else {
 199                 if ((k = malloc(sizeof(*k))) == NULL)
 200                         return SSH_ERR_ALLOC_FAIL;
 201                 k->key = key;
 202                 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
 203                 r = 0;
 204         }
 205
 206         return r;
 207 }
 208
 209 int
 210 ssh_set_verify_host_key_callback(struct ssh *ssh,
 211     int (*cb)(struct sshkey *, struct ssh *))
 212 {
 213         if (cb == NULL || ssh->kex == NULL)
 214                 return SSH_ERR_INVALID_ARGUMENT;
 215
 216         ssh->kex->verify_host_key = cb;
 217
 218         return 0;
 219 }
 220
 221 int
 222 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
 223 {
 224         return sshbuf_put(ssh_packet_get_input(ssh), data, len);
 225 }
 226
 227 int
 228 ssh_packet_next(struct ssh *ssh, u_char *typep)
 229 {
 230         int r;
 231         u_int32_t seqnr;
 232         u_char type;
 233
 234         /*
 235          * Try to read a packet. Return SSH_MSG_NONE if no packet or not
 236          * enough data.
 237          */
 238         *typep = SSH_MSG_NONE;
 239         if (ssh->kex->client_version_string == NULL ||
 240             ssh->kex->server_version_string == NULL)
 241                 return _ssh_exchange_banner(ssh);
 242         /*
 243          * If we enough data and a dispatch function then
 244          * call the function and get the next packet.
 245          * Otherwise return the packet type to the caller so it
 246          * can decide how to go on.
 247          *
 248          * We will only call the dispatch function for:
 249          *     20-29    Algorithm negotiation
 250          *     30-49    Key exchange method specific (numbers can be reused for
 251          *              different authentication methods)
 252          */
 253         for (;;) {
 254                 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
 255                         return r;
 256                 if (type > 0 && type < DISPATCH_MAX &&
 257                     type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
 258                     ssh->dispatch[type] != NULL) {
 259                         if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
 260                                 return r;
 261                 } else {
 262                         *typep = type;
 263                         return 0;
 264                 }
 265         }
 266 }
 267
 268 const u_char *
 269 ssh_packet_payload(struct ssh *ssh, size_t *lenp)
 270 {
 271         return sshpkt_ptr(ssh, lenp);
 272 }
 273
 274 int
 275 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
 276 {
 277         int r;
 278
 279         if ((r = sshpkt_start(ssh, type)) != 0 ||
 280             (r = sshpkt_put(ssh, data, len)) != 0 ||
 281             (r = sshpkt_send(ssh)) != 0)
 282                 return r;
 283         return 0;
 284 }
 285
 286 const u_char *
 287 ssh_output_ptr(struct ssh *ssh, size_t *len)
 288 {
 289         struct sshbuf *output = ssh_packet_get_output(ssh);
 290
 291         *len = sshbuf_len(output);
 292         return sshbuf_ptr(output);
 293 }
 294
 295 int
 296 ssh_output_consume(struct ssh *ssh, size_t len)
 297 {
 298         return sshbuf_consume(ssh_packet_get_output(ssh), len);
 299 }
 300
 301 int
 302 ssh_output_space(struct ssh *ssh, size_t len)
 303 {
 304         return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
 305 }
 306
 307 int
 308 ssh_input_space(struct ssh *ssh, size_t len)
 309 {
 310         return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
 311 }
 312
 313 /* Read other side's version identification. */
 314 int
 315 _ssh_read_banner(struct ssh *ssh, char **bannerp)
 316 {
 317         struct sshbuf *input;
 318         const char *s;
 319         char buf[256], remote_version[256];     /* must be same size! */
 320         const char *mismatch = "Protocol mismatch.\r\n";
 321         int r, remote_major, remote_minor;
 322         size_t i, n, j, len;
 323
 324         *bannerp = NULL;
 325         input = ssh_packet_get_input(ssh);
 326         len = sshbuf_len(input);
 327         s = (const char *)sshbuf_ptr(input);
 328         for (j = n = 0;;) {
 329                 for (i = 0; i < sizeof(buf) - 1; i++) {
 330                         if (j >= len)
 331                                 return (0);
 332                         buf[i] = s[j++];
 333                         if (buf[i] == '\r') {
 334                                 buf[i] = '\n';
 335                                 buf[i + 1] = 0;
 336                                 continue;               /**XXX wait for \n */
 337                         }
 338                         if (buf[i] == '\n') {
 339                                 buf[i + 1] = 0;
 340                                 break;
 341                         }
 342                 }
 343                 buf[sizeof(buf) - 1] = 0;
 344                 if (strncmp(buf, "SSH-", 4) == 0)
 345                         break;
 346                 debug("ssh_exchange_identification: %s", buf);
 347                 if (ssh->kex->server || ++n > 65536) {
 348                         if ((r = sshbuf_put(ssh_packet_get_output(ssh),
 349                            mismatch, strlen(mismatch))) != 0)
 350                                 return r;
 351                         return SSH_ERR_NO_PROTOCOL_VERSION;
 352                 }
 353         }
 354         if ((r = sshbuf_consume(input, j)) != 0)
 355                 return r;
 356
 357         /*
 358          * Check that the versions match.  In future this might accept
 359          * several versions and set appropriate flags to handle them.
 360          */
 361         if (sscanf(buf, "SSH-%d.%d-%[^\n]\n",
 362             &remote_major, &remote_minor, remote_version) != 3)
 363                 return SSH_ERR_INVALID_FORMAT;
 364         debug("Remote protocol version %d.%d, remote software version %.100s",
 365             remote_major, remote_minor, remote_version);
 366
 367         ssh->compat = compat_datafellows(remote_version);
 368         if  (remote_major == 1 && remote_minor == 99) {
 369                 remote_major = 2;
 370                 remote_minor = 0;
 371         }
 372         if (remote_major != 2)
 373                 return SSH_ERR_PROTOCOL_MISMATCH;
 374         enable_compat20();
 375         chop(buf);
 376         debug("Remote version string %.100s", buf);
 377         if ((*bannerp = strdup(buf)) == NULL)
 378                 return SSH_ERR_ALLOC_FAIL;
 379         return 0;
 380 }
 381
 382 /* Send our own protocol version identification. */
 383 int
 384 _ssh_send_banner(struct ssh *ssh, char **bannerp)
 385 {
 386         char buf[256];
 387         int r;
 388
 389         snprintf(buf, sizeof buf, "SSH-2.0-%.100s\r\n", SSH_VERSION);
 390         if ((r = sshbuf_put(ssh_packet_get_output(ssh), buf, strlen(buf))) != 0)
 391                 return r;
 392         chop(buf);
 393         debug("Local version string %.100s", buf);
 394         if ((*bannerp = strdup(buf)) == NULL)
 395                 return SSH_ERR_ALLOC_FAIL;
 396         return 0;
 397 }
 398
 399 int
 400 _ssh_exchange_banner(struct ssh *ssh)
 401 {
 402         struct kex *kex = ssh->kex;
 403         int r;
 404
 405         /*
 406          * if _ssh_read_banner() cannot parse a full version string
 407          * it will return NULL and we end up calling it again.
 408          */
 409
 410         r = 0;
 411         if (kex->server) {
 412                 if (kex->server_version_string == NULL)
 413                         r = _ssh_send_banner(ssh, &kex->server_version_string);
 414                 if (r == 0 &&
 415                     kex->server_version_string != NULL &&
 416                     kex->client_version_string == NULL)
 417                         r = _ssh_read_banner(ssh, &kex->client_version_string);
 418         } else {
 419                 if (kex->server_version_string == NULL)
 420                         r = _ssh_read_banner(ssh, &kex->server_version_string);
 421                 if (r == 0 &&
 422                     kex->server_version_string != NULL &&
 423                     kex->client_version_string == NULL)
 424                         r = _ssh_send_banner(ssh, &kex->client_version_string);
 425         }
 426         if (r != 0)
 427                 return r;
 428         /* start initial kex as soon as we have exchanged the banners */
 429         if (kex->server_version_string != NULL &&
 430             kex->client_version_string != NULL) {
 431                 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
 432                     (r = kex_send_kexinit(ssh)) != 0)
 433                         return r;
 434         }
 435         return 0;
 436 }
 437
 438 struct sshkey *
 439 _ssh_host_public_key(int type, int nid, struct ssh *ssh)
 440 {
 441         struct key_entry *k;
 442
 443         debug3("%s: need %d", __func__, type);
 444         TAILQ_FOREACH(k, &ssh->public_keys, next) {
 445                 debug3("%s: check %s", __func__, sshkey_type(k->key));
 446                 if (k->key->type == type &&
 447                     (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
 448                         return (k->key);
 449         }
 450         return (NULL);
 451 }
 452
 453 struct sshkey *
 454 _ssh_host_private_key(int type, int nid, struct ssh *ssh)
 455 {
 456         struct key_entry *k;
 457
 458         debug3("%s: need %d", __func__, type);
 459         TAILQ_FOREACH(k, &ssh->private_keys, next) {
 460                 debug3("%s: check %s", __func__, sshkey_type(k->key));
 461                 if (k->key->type == type &&
 462                     (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
 463                         return (k->key);
 464         }
 465         return (NULL);
 466 }
 467
 468 int
 469 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
 470 {
 471         struct key_entry *k;
 472
 473         debug3("%s: need %s", __func__, sshkey_type(hostkey));
 474         TAILQ_FOREACH(k, &ssh->public_keys, next) {
 475                 debug3("%s: check %s", __func__, sshkey_type(k->key));
 476                 if (sshkey_equal_public(hostkey, k->key))
 477                         return (0);     /* ok */
 478         }
 479         return (-1);    /* failed */
 480 }
 481
 482 /* offer hostkey algorithms in kexinit depending on registered keys */
 483 int
 484 _ssh_order_hostkeyalgs(struct ssh *ssh)
 485 {
 486         struct key_entry *k;
 487         char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
 488         char **proposal;
 489         size_t maxlen;
 490         int ktype, r;
 491
 492         /* XXX we de-serialize ssh->kex->my, modify it, and change it */
 493         if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
 494                 return r;
 495         orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
 496         if ((oavail = avail = strdup(orig)) == NULL) {
 497                 r = SSH_ERR_ALLOC_FAIL;
 498                 goto out;
 499         }
 500         maxlen = strlen(avail) + 1;
 501         if ((replace = calloc(1, maxlen)) == NULL) {
 502                 r = SSH_ERR_ALLOC_FAIL;
 503                 goto out;
 504         }
 505         *replace = '\0';
 506         while ((alg = strsep(&avail, ",")) && *alg != '\0') {
 507                 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
 508                         continue;
 509                 TAILQ_FOREACH(k, &ssh->public_keys, next) {
 510                         if (k->key->type == ktype ||
 511                             (sshkey_is_cert(k->key) && k->key->type ==
 512                             sshkey_type_plain(ktype))) {
 513                                 if (*replace != '\0')
 514                                         strlcat(replace, ",", maxlen);
 515                                 strlcat(replace, alg, maxlen);
 516                                 break;
 517                         }
 518                 }
 519         }
 520         if (*replace != '\0') {
 521                 debug2("%s: orig/%d    %s", __func__, ssh->kex->server, orig);
 522                 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace);
 523                 free(orig);
 524                 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
 525                 replace = NULL; /* owned by proposal */
 526                 r = kex_prop2buf(ssh->kex->my, proposal);
 527         }
 528  out:
 529         free(oavail);
 530         free(replace);
 531         kex_prop_free(proposal);
 532         return r;
 533 }
 534
 535 int
 536 _ssh_host_key_sign(struct sshkey *privkey, struct sshkey *pubkey,
 537     u_char **signature, size_t *slen, const u_char *data, size_t dlen,
 538     const char *alg, u_int compat)
 539 {
 540         return sshkey_sign(privkey, signature, slen, data, dlen, alg, compat);
 541 }