ssh-pkcs11-client.c

   1 /* $OpenBSD: ssh-pkcs11-client.c,v 1.20 2024/08/15 00:51:51 djm Exp $ */
   2 /*
   3  * Copyright (c) 2010 Markus Friedl.  All rights reserved.
   4  * Copyright (c) 2014 Pedro Martelletto. All rights reserved.
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include "includes.h"
  20
  21 #ifdef ENABLE_PKCS11
  22
  23 #include <sys/types.h>
  24 #ifdef HAVE_SYS_TIME_H
  25 # include <sys/time.h>
  26 #endif
  27 #include <sys/socket.h>
  28
  29 #include <stdarg.h>
  30 #include <string.h>
  31 #include <unistd.h>
  32 #include <errno.h>
  33 #include <limits.h>
  34
  35 #include <openssl/ecdsa.h>
  36 #include <openssl/rsa.h>
  37
  38 #include "pathnames.h"
  39 #include "xmalloc.h"
  40 #include "sshbuf.h"
  41 #include "log.h"
  42 #include "misc.h"
  43 #include "sshkey.h"
  44 #include "authfd.h"
  45 #include "atomicio.h"
  46 #include "ssh-pkcs11.h"
  47 #include "ssherr.h"
  48
  49 #include "openbsd-compat/openssl-compat.h"
  50
  51 #if !defined(OPENSSL_HAS_ECC) || !defined(HAVE_EC_KEY_METHOD_NEW)
  52 #define EC_KEY_METHOD void
  53 #define EC_KEY void
  54 #endif
  55
  56 /* borrows code from sftp-server and ssh-agent */
  57
  58 /*
  59  * Maintain a list of ssh-pkcs11-helper subprocesses. These may be looked up
  60  * by provider path or their unique EC/RSA METHOD pointers.
  61  */
  62 struct helper {
  63         char *path;
  64         pid_t pid;
  65         int fd;
  66         RSA_METHOD *rsa_meth;
  67         EC_KEY_METHOD *ec_meth;
  68         int (*rsa_finish)(RSA *rsa);
  69         void (*ec_finish)(EC_KEY *key);
  70         size_t nrsa, nec; /* number of active keys of each type */
  71 };
  72 static struct helper **helpers;
  73 static size_t nhelpers;
  74
  75 static struct helper *
  76 helper_by_provider(const char *path)
  77 {
  78         size_t i;
  79
  80         for (i = 0; i < nhelpers; i++) {
  81                 if (helpers[i] == NULL || helpers[i]->path == NULL ||
  82                     helpers[i]->fd == -1)
  83                         continue;
  84                 if (strcmp(helpers[i]->path, path) == 0)
  85                         return helpers[i];
  86         }
  87         return NULL;
  88 }
  89
  90 static struct helper *
  91 helper_by_rsa(const RSA *rsa)
  92 {
  93         size_t i;
  94         const RSA_METHOD *meth;
  95
  96         if ((meth = RSA_get_method(rsa)) == NULL)
  97                 return NULL;
  98         for (i = 0; i < nhelpers; i++) {
  99                 if (helpers[i] != NULL && helpers[i]->rsa_meth == meth)
 100                         return helpers[i];
 101         }
 102         return NULL;
 103
 104 }
 105
 106 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 107 static struct helper *
 108 helper_by_ec(const EC_KEY *ec)
 109 {
 110         size_t i;
 111         const EC_KEY_METHOD *meth;
 112
 113         if ((meth = EC_KEY_get_method(ec)) == NULL)
 114                 return NULL;
 115         for (i = 0; i < nhelpers; i++) {
 116                 if (helpers[i] != NULL && helpers[i]->ec_meth == meth)
 117                         return helpers[i];
 118         }
 119         return NULL;
 120
 121 }
 122 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
 123
 124 static void
 125 helper_free(struct helper *helper)
 126 {
 127         size_t i;
 128         int found = 0;
 129
 130         if (helper == NULL)
 131                 return;
 132         if (helper->path == NULL || helper->ec_meth == NULL ||
 133             helper->rsa_meth == NULL)
 134                 fatal_f("inconsistent helper");
 135         debug3_f("free helper for provider %s", helper->path);
 136         for (i = 0; i < nhelpers; i++) {
 137                 if (helpers[i] == helper) {
 138                         if (found)
 139                                 fatal_f("helper recorded more than once");
 140                         found = 1;
 141                 }
 142                 else if (found)
 143                         helpers[i - 1] = helpers[i];
 144         }
 145         if (found) {
 146                 helpers = xrecallocarray(helpers, nhelpers,
 147                     nhelpers - 1, sizeof(*helpers));
 148                 nhelpers--;
 149         }
 150         free(helper->path);
 151 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 152         EC_KEY_METHOD_free(helper->ec_meth);
 153 #endif
 154         RSA_meth_free(helper->rsa_meth);
 155         free(helper);
 156 }
 157
 158 static void
 159 helper_terminate(struct helper *helper)
 160 {
 161         if (helper == NULL) {
 162                 return;
 163         } else if (helper->fd == -1) {
 164                 debug3_f("already terminated");
 165         } else {
 166                 debug3_f("terminating helper for %s; "
 167                     "remaining %zu RSA %zu ECDSA",
 168                     helper->path, helper->nrsa, helper->nec);
 169                 close(helper->fd);
 170                 /* XXX waitpid() */
 171                 helper->fd = -1;
 172                 helper->pid = -1;
 173         }
 174         /*
 175          * Don't delete the helper entry until there are no remaining keys
 176          * that reference it. Otherwise, any signing operation would call
 177          * a free'd METHOD pointer and that would be bad.
 178          */
 179         if (helper->nrsa == 0 && helper->nec == 0)
 180                 helper_free(helper);
 181 }
 182
 183 static void
 184 send_msg(int fd, struct sshbuf *m)
 185 {
 186         u_char buf[4];
 187         size_t mlen = sshbuf_len(m);
 188         int r;
 189
 190         if (fd == -1)
 191                 return;
 192         POKE_U32(buf, mlen);
 193         if (atomicio(vwrite, fd, buf, 4) != 4 ||
 194             atomicio(vwrite, fd, sshbuf_mutable_ptr(m),
 195             sshbuf_len(m)) != sshbuf_len(m))
 196                 error("write to helper failed");
 197         if ((r = sshbuf_consume(m, mlen)) != 0)
 198                 fatal_fr(r, "consume");
 199 }
 200
 201 static int
 202 recv_msg(int fd, struct sshbuf *m)
 203 {
 204         u_int l, len;
 205         u_char c, buf[1024];
 206         int r;
 207
 208         sshbuf_reset(m);
 209         if (fd == -1)
 210                 return 0; /* XXX */
 211         if ((len = atomicio(read, fd, buf, 4)) != 4) {
 212                 error("read from helper failed: %u", len);
 213                 return (0); /* XXX */
 214         }
 215         len = PEEK_U32(buf);
 216         if (len > 256 * 1024)
 217                 fatal("response too long: %u", len);
 218         /* read len bytes into m */
 219         while (len > 0) {
 220                 l = len;
 221                 if (l > sizeof(buf))
 222                         l = sizeof(buf);
 223                 if (atomicio(read, fd, buf, l) != l) {
 224                         error("response from helper failed.");
 225                         return (0); /* XXX */
 226                 }
 227                 if ((r = sshbuf_put(m, buf, l)) != 0)
 228                         fatal_fr(r, "sshbuf_put");
 229                 len -= l;
 230         }
 231         if ((r = sshbuf_get_u8(m, &c)) != 0)
 232                 fatal_fr(r, "parse type");
 233         return c;
 234 }
 235
 236 int
 237 pkcs11_init(int interactive)
 238 {
 239         return 0;
 240 }
 241
 242 void
 243 pkcs11_terminate(void)
 244 {
 245         size_t i;
 246
 247         debug3_f("terminating %zu helpers", nhelpers);
 248         for (i = 0; i < nhelpers; i++)
 249                 helper_terminate(helpers[i]);
 250 }
 251
 252 static int
 253 rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
 254 {
 255         struct sshkey *key = NULL;
 256         struct sshbuf *msg = NULL;
 257         u_char *blob = NULL, *signature = NULL;
 258         size_t blen, slen = 0;
 259         int r, ret = -1;
 260         struct helper *helper;
 261
 262         if ((helper = helper_by_rsa(rsa)) == NULL || helper->fd == -1)
 263                 fatal_f("no helper for PKCS11 key");
 264         debug3_f("signing with PKCS11 provider %s", helper->path);
 265         if (padding != RSA_PKCS1_PADDING)
 266                 goto fail;
 267         if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
 268                 error_f("sshkey_new failed");
 269                 goto fail;
 270         }
 271         if ((key->pkey = EVP_PKEY_new()) == NULL ||
 272            EVP_PKEY_set1_RSA(key->pkey, rsa) != 1) {
 273                 error_f("pkey setup failed");
 274                 goto fail;
 275         }
 276
 277         key->type = KEY_RSA;
 278         if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
 279                 error_fr(r, "encode key");
 280                 goto fail;
 281         }
 282         if ((msg = sshbuf_new()) == NULL)
 283                 fatal_f("sshbuf_new failed");
 284         if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
 285             (r = sshbuf_put_string(msg, blob, blen)) != 0 ||
 286             (r = sshbuf_put_string(msg, from, flen)) != 0 ||
 287             (r = sshbuf_put_u32(msg, 0)) != 0)
 288                 fatal_fr(r, "compose");
 289         send_msg(helper->fd, msg);
 290         sshbuf_reset(msg);
 291
 292         if (recv_msg(helper->fd, msg) == SSH2_AGENT_SIGN_RESPONSE) {
 293                 if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
 294                         fatal_fr(r, "parse");
 295                 if (slen <= (size_t)RSA_size(rsa)) {
 296                         memcpy(to, signature, slen);
 297                         ret = slen;
 298                 }
 299                 free(signature);
 300         }
 301  fail:
 302         free(blob);
 303         sshkey_free(key);
 304         sshbuf_free(msg);
 305         return (ret);
 306 }
 307
 308 static int
 309 rsa_finish(RSA *rsa)
 310 {
 311         struct helper *helper;
 312
 313         if ((helper = helper_by_rsa(rsa)) == NULL)
 314                 fatal_f("no helper for PKCS11 key");
 315         debug3_f("free PKCS11 RSA key for provider %s", helper->path);
 316         if (helper->rsa_finish != NULL)
 317                 helper->rsa_finish(rsa);
 318         if (helper->nrsa == 0)
 319                 fatal_f("RSA refcount error");
 320         helper->nrsa--;
 321         debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
 322             helper->path, helper->nrsa, helper->nec);
 323         if (helper->nrsa == 0 && helper->nec == 0)
 324                 helper_terminate(helper);
 325         return 1;
 326 }
 327
 328 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 329 static ECDSA_SIG *
 330 ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
 331     const BIGNUM *rp, EC_KEY *ec)
 332 {
 333         struct sshkey *key = NULL;
 334         struct sshbuf *msg = NULL;
 335         ECDSA_SIG *ret = NULL;
 336         const u_char *cp;
 337         u_char *blob = NULL, *signature = NULL;
 338         size_t blen, slen = 0;
 339         int r, nid;
 340         struct helper *helper;
 341
 342         if ((helper = helper_by_ec(ec)) == NULL || helper->fd == -1)
 343                 fatal_f("no helper for PKCS11 key");
 344         debug3_f("signing with PKCS11 provider %s", helper->path);
 345
 346         if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
 347                 error_f("sshkey_new failed");
 348                 goto fail;
 349         }
 350         if ((key->pkey = EVP_PKEY_new()) == NULL ||
 351             EVP_PKEY_set1_EC_KEY(key->pkey, ec) != 1) {
 352                 error("pkey setup failed");
 353                 goto fail;
 354         }
 355         if ((nid = sshkey_ecdsa_pkey_to_nid(key->pkey)) < 0) {
 356                 error("couldn't get curve nid");
 357                 goto fail;
 358         }
 359         key->ecdsa_nid = nid;
 360         key->type = KEY_ECDSA;
 361
 362         if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
 363                 error_fr(r, "encode key");
 364                 goto fail;
 365         }
 366         if ((msg = sshbuf_new()) == NULL)
 367                 fatal_f("sshbuf_new failed");
 368         if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
 369             (r = sshbuf_put_string(msg, blob, blen)) != 0 ||
 370             (r = sshbuf_put_string(msg, dgst, dgst_len)) != 0 ||
 371             (r = sshbuf_put_u32(msg, 0)) != 0)
 372                 fatal_fr(r, "compose");
 373         send_msg(helper->fd, msg);
 374         sshbuf_reset(msg);
 375
 376         if (recv_msg(helper->fd, msg) == SSH2_AGENT_SIGN_RESPONSE) {
 377                 if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
 378                         fatal_fr(r, "parse");
 379                 cp = signature;
 380                 ret = d2i_ECDSA_SIG(NULL, &cp, slen);
 381                 free(signature);
 382         }
 383
 384  fail:
 385         free(blob);
 386         sshkey_free(key);
 387         sshbuf_free(msg);
 388         return (ret);
 389 }
 390
 391 static void
 392 ecdsa_do_finish(EC_KEY *ec)
 393 {
 394         struct helper *helper;
 395
 396         if ((helper = helper_by_ec(ec)) == NULL)
 397                 fatal_f("no helper for PKCS11 key");
 398         debug3_f("free PKCS11 ECDSA key for provider %s", helper->path);
 399         if (helper->ec_finish != NULL)
 400                 helper->ec_finish(ec);
 401         if (helper->nec == 0)
 402                 fatal_f("ECDSA refcount error");
 403         helper->nec--;
 404         debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
 405             helper->path, helper->nrsa, helper->nec);
 406         if (helper->nrsa == 0 && helper->nec == 0)
 407                 helper_terminate(helper);
 408 }
 409 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
 410
 411 /* redirect private key crypto operations to the ssh-pkcs11-helper */
 412 static void
 413 wrap_key(struct helper *helper, struct sshkey *k)
 414 {
 415         RSA *rsa = NULL;
 416         EC_KEY *ecdsa = NULL;
 417
 418         debug3_f("wrap %s for provider %s", sshkey_type(k), helper->path);
 419         if (k->type == KEY_RSA) {
 420                 if ((rsa = EVP_PKEY_get1_RSA(k->pkey)) == NULL)
 421                         fatal_f("no RSA key");
 422                 if (RSA_set_method(rsa, helper->rsa_meth) != 1)
 423                         fatal_f("RSA_set_method failed");
 424                 if (helper->nrsa++ >= INT_MAX)
 425                         fatal_f("RSA refcount error");
 426                 if (EVP_PKEY_set1_RSA(k->pkey, rsa) != 1)
 427                         fatal_f("EVP_PKEY_set1_RSA failed");
 428                 RSA_free(rsa);
 429 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 430         } else if (k->type == KEY_ECDSA) {
 431                 if ((ecdsa = EVP_PKEY_get1_EC_KEY(k->pkey)) == NULL)
 432                         fatal_f("no ECDSA key");
 433                 if (EC_KEY_set_method(ecdsa, helper->ec_meth) != 1)
 434                         fatal_f("EC_KEY_set_method failed");
 435                 if (helper->nec++ >= INT_MAX)
 436                         fatal_f("EC refcount error");
 437                 if (EVP_PKEY_set1_EC_KEY(k->pkey, ecdsa) != 1)
 438                         fatal_f("EVP_PKEY_set1_EC_KEY failed");
 439                 EC_KEY_free(ecdsa);
 440 #endif
 441         } else
 442                 fatal_f("unknown key type");
 443         k->flags |= SSHKEY_FLAG_EXT;
 444         debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
 445             helper->path, helper->nrsa, helper->nec);
 446 }
 447
 448 /*
 449  * Make a private PKCS#11-backed certificate by grafting a previously-loaded
 450  * PKCS#11 private key and a public certificate key.
 451  */
 452 int
 453 pkcs11_make_cert(const struct sshkey *priv,
 454     const struct sshkey *certpub, struct sshkey **certprivp)
 455 {
 456         struct helper *helper = NULL;
 457         struct sshkey *ret;
 458         int r;
 459         RSA *rsa_priv = NULL, *rsa_cert = NULL;
 460 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 461         EC_KEY *ec_priv = NULL, *ec_cert = NULL;
 462 #endif
 463
 464         debug3_f("private key type %s cert type %s", sshkey_type(priv),
 465             sshkey_type(certpub));
 466         *certprivp = NULL;
 467         if (!sshkey_is_cert(certpub) || sshkey_is_cert(priv) ||
 468             !sshkey_equal_public(priv, certpub)) {
 469                 error_f("private key %s doesn't match cert %s",
 470                     sshkey_type(priv), sshkey_type(certpub));
 471                 return SSH_ERR_INVALID_ARGUMENT;
 472         }
 473         *certprivp = NULL;
 474         if (priv->type == KEY_RSA) {
 475                 if ((rsa_priv = EVP_PKEY_get1_RSA(priv->pkey)) == NULL)
 476                         fatal_f("no RSA pkey");
 477                 if ((helper = helper_by_rsa(rsa_priv)) == NULL ||
 478                     helper->fd == -1)
 479                         fatal_f("no helper for PKCS11 RSA key");
 480                 if ((r = sshkey_from_private(priv, &ret)) != 0)
 481                         fatal_fr(r, "copy key");
 482                 if ((rsa_cert = EVP_PKEY_get1_RSA(ret->pkey)) == NULL)
 483                         fatal_f("no RSA cert pkey");
 484                 if (RSA_set_method(rsa_cert, helper->rsa_meth) != 1)
 485                         fatal_f("RSA_set_method failed");
 486                 if (helper->nrsa++ >= INT_MAX)
 487                         fatal_f("RSA refcount error");
 488                 if (EVP_PKEY_set1_RSA(ret->pkey, rsa_cert) != 1)
 489                         fatal_f("EVP_PKEY_set1_RSA failed");
 490                 RSA_free(rsa_priv);
 491                 RSA_free(rsa_cert);
 492 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 493         } else if (priv->type == KEY_ECDSA) {
 494                 if ((ec_priv = EVP_PKEY_get1_EC_KEY(priv->pkey)) == NULL)
 495                         fatal_f("no EC pkey");
 496                 if ((helper = helper_by_ec(ec_priv)) == NULL ||
 497                     helper->fd == -1)
 498                         fatal_f("no helper for PKCS11 EC key");
 499                 if ((r = sshkey_from_private(priv, &ret)) != 0)
 500                         fatal_fr(r, "copy key");
 501                 if ((ec_cert = EVP_PKEY_get1_EC_KEY(ret->pkey)) == NULL)
 502                         fatal_f("no EC cert pkey");
 503                 if (EC_KEY_set_method(ec_cert, helper->ec_meth) != 1)
 504                         fatal_f("EC_KEY_set_method failed");
 505                 if (helper->nec++ >= INT_MAX)
 506                         fatal_f("EC refcount error");
 507                 if (EVP_PKEY_set1_EC_KEY(ret->pkey, ec_cert) != 1)
 508                         fatal_f("EVP_PKEY_set1_EC_KEY failed");
 509                 EC_KEY_free(ec_priv);
 510                 EC_KEY_free(ec_cert);
 511 #endif
 512         } else
 513                 fatal_f("unknown key type %s", sshkey_type(priv));
 514
 515         ret->flags |= SSHKEY_FLAG_EXT;
 516         if ((r = sshkey_to_certified(ret)) != 0 ||
 517             (r = sshkey_cert_copy(certpub, ret)) != 0)
 518                 fatal_fr(r, "graft certificate");
 519         debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
 520             helper->path, helper->nrsa, helper->nec);
 521         /* success */
 522         *certprivp = ret;
 523         return 0;
 524 }
 525
 526 static int
 527 pkcs11_start_helper_methods(struct helper *helper)
 528 {
 529         RSA_METHOD *rsa_meth = NULL;
 530         EC_KEY_METHOD *ec_meth = NULL;
 531 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 532         int (*ec_init)(EC_KEY *key);
 533         int (*ec_copy)(EC_KEY *dest, const EC_KEY *src);
 534         int (*ec_set_group)(EC_KEY *key, const EC_GROUP *grp);
 535         int (*ec_set_private)(EC_KEY *key, const BIGNUM *priv_key);
 536         int (*ec_set_public)(EC_KEY *key, const EC_POINT *pub_key);
 537         int (*ec_sign)(int, const unsigned char *, int, unsigned char *,
 538             unsigned int *, const BIGNUM *, const BIGNUM *, EC_KEY *) = NULL;
 539
 540         if ((ec_meth = EC_KEY_METHOD_new(EC_KEY_OpenSSL())) == NULL)
 541                 return -1;
 542         EC_KEY_METHOD_get_sign(ec_meth, &ec_sign, NULL, NULL);
 543         EC_KEY_METHOD_set_sign(ec_meth, ec_sign, NULL, ecdsa_do_sign);
 544         EC_KEY_METHOD_get_init(ec_meth, &ec_init, &helper->ec_finish,
 545             &ec_copy, &ec_set_group, &ec_set_private, &ec_set_public);
 546         EC_KEY_METHOD_set_init(ec_meth, ec_init, ecdsa_do_finish,
 547             ec_copy, ec_set_group, ec_set_private, ec_set_public);
 548 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
 549
 550         if ((rsa_meth = RSA_meth_dup(RSA_get_default_method())) == NULL)
 551                 fatal_f("RSA_meth_dup failed");
 552         helper->rsa_finish = RSA_meth_get_finish(rsa_meth);
 553         if (!RSA_meth_set1_name(rsa_meth, "ssh-pkcs11-helper") ||
 554             !RSA_meth_set_priv_enc(rsa_meth, rsa_encrypt) ||
 555             !RSA_meth_set_finish(rsa_meth, rsa_finish))
 556                 fatal_f("failed to prepare method");
 557
 558         helper->ec_meth = ec_meth;
 559         helper->rsa_meth = rsa_meth;
 560         return 0;
 561 }
 562
 563 static struct helper *
 564 pkcs11_start_helper(const char *path)
 565 {
 566         int pair[2];
 567         char *prog, *verbosity = NULL;
 568         struct helper *helper;
 569         pid_t pid;
 570
 571         if (nhelpers >= INT_MAX)
 572                 fatal_f("too many helpers");
 573         debug3_f("start helper for %s", path);
 574         if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
 575                 error_f("socketpair: %s", strerror(errno));
 576                 return NULL;
 577         }
 578         helper = xcalloc(1, sizeof(*helper));
 579         if (pkcs11_start_helper_methods(helper) == -1) {
 580                 error_f("pkcs11_start_helper_methods failed");
 581                 goto fail;
 582         }
 583         if ((pid = fork()) == -1) {
 584                 error_f("fork: %s", strerror(errno));
 585  fail:
 586                 close(pair[0]);
 587                 close(pair[1]);
 588                 RSA_meth_free(helper->rsa_meth);
 589 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
 590                 EC_KEY_METHOD_free(helper->ec_meth);
 591 #endif
 592                 free(helper);
 593                 return NULL;
 594         } else if (pid == 0) {
 595                 if ((dup2(pair[1], STDIN_FILENO) == -1) ||
 596                     (dup2(pair[1], STDOUT_FILENO) == -1)) {
 597                         fprintf(stderr, "dup2: %s\n", strerror(errno));
 598                         _exit(1);
 599                 }
 600                 close(pair[0]);
 601                 close(pair[1]);
 602                 prog = getenv("SSH_PKCS11_HELPER");
 603                 if (prog == NULL || strlen(prog) == 0)
 604                         prog = _PATH_SSH_PKCS11_HELPER;
 605                 if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)
 606                         verbosity = "-vvv";
 607                 debug_f("starting %s %s", prog,
 608                     verbosity == NULL ? "" : verbosity);
 609                 execlp(prog, prog, verbosity, (char *)NULL);
 610                 fprintf(stderr, "exec: %s: %s\n", prog, strerror(errno));
 611                 _exit(1);
 612         }
 613         close(pair[1]);
 614         helper->fd = pair[0];
 615         helper->path = xstrdup(path);
 616         helper->pid = pid;
 617         debug3_f("helper %zu for \"%s\" on fd %d pid %ld", nhelpers,
 618             helper->path, helper->fd, (long)helper->pid);
 619         helpers = xrecallocarray(helpers, nhelpers,
 620             nhelpers + 1, sizeof(*helpers));
 621         helpers[nhelpers++] = helper;
 622         return helper;
 623 }
 624
 625 int
 626 pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
 627     char ***labelsp)
 628 {
 629         struct sshkey *k;
 630         int r, type;
 631         u_char *blob;
 632         char *label;
 633         size_t blen;
 634         u_int nkeys, i;
 635         struct sshbuf *msg;
 636         struct helper *helper;
 637
 638         if ((helper = helper_by_provider(name)) == NULL &&
 639             (helper = pkcs11_start_helper(name)) == NULL)
 640                 return -1;
 641
 642         if ((msg = sshbuf_new()) == NULL)
 643                 fatal_f("sshbuf_new failed");
 644         if ((r = sshbuf_put_u8(msg, SSH_AGENTC_ADD_SMARTCARD_KEY)) != 0 ||
 645             (r = sshbuf_put_cstring(msg, name)) != 0 ||
 646             (r = sshbuf_put_cstring(msg, pin)) != 0)
 647                 fatal_fr(r, "compose");
 648         send_msg(helper->fd, msg);
 649         sshbuf_reset(msg);
 650
 651         type = recv_msg(helper->fd, msg);
 652         if (type == SSH2_AGENT_IDENTITIES_ANSWER) {
 653                 if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
 654                         fatal_fr(r, "parse nkeys");
 655                 *keysp = xcalloc(nkeys, sizeof(struct sshkey *));
 656                 if (labelsp)
 657                         *labelsp = xcalloc(nkeys, sizeof(char *));
 658                 for (i = 0; i < nkeys; i++) {
 659                         /* XXX clean up properly instead of fatal() */
 660                         if ((r = sshbuf_get_string(msg, &blob, &blen)) != 0 ||
 661                             (r = sshbuf_get_cstring(msg, &label, NULL)) != 0)
 662                                 fatal_fr(r, "parse key");
 663                         if ((r = sshkey_from_blob(blob, blen, &k)) != 0)
 664                                 fatal_fr(r, "decode key");
 665                         wrap_key(helper, k);
 666                         (*keysp)[i] = k;
 667                         if (labelsp)
 668                                 (*labelsp)[i] = label;
 669                         else
 670                                 free(label);
 671                         free(blob);
 672                 }
 673         } else if (type == SSH2_AGENT_FAILURE) {
 674                 if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
 675                         nkeys = -1;
 676         } else {
 677                 nkeys = -1;
 678         }
 679         sshbuf_free(msg);
 680         return (nkeys);
 681 }
 682
 683 int
 684 pkcs11_del_provider(char *name)
 685 {
 686         struct helper *helper;
 687
 688         /*
 689          * ssh-agent deletes keys before calling this, so the helper entry
 690          * should be gone before we get here.
 691          */
 692         debug3_f("delete %s", name);
 693         if ((helper = helper_by_provider(name)) != NULL)
 694                 helper_terminate(helper);
 695         return 0;
 696 }
 697 #endif /* ENABLE_PKCS11 */