1 /* $OpenBSD: ssh-pkcs11-client.c,v 1.19 2023/12/18 14:46:56 djm Exp $ */
3 * Copyright (c) 2010 Markus Friedl. All rights reserved.
4 * Copyright (c) 2014 Pedro Martelletto. All rights reserved.
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.
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.
23 #include <sys/types.h>
24 #ifdef HAVE_SYS_TIME_H
25 # include <sys/time.h>
27 #include <sys/socket.h>
35 #include <openssl/ecdsa.h>
36 #include <openssl/rsa.h>
38 #include "pathnames.h"
46 #include "ssh-pkcs11.h"
49 #include "openbsd-compat/openssl-compat.h"
51 #if !defined(OPENSSL_HAS_ECC) || !defined(HAVE_EC_KEY_METHOD_NEW)
52 #define EC_KEY_METHOD void
56 /* borrows code from sftp-server and ssh-agent */
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.
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 */
72 static struct helper **helpers;
73 static size_t nhelpers;
75 static struct helper *
76 helper_by_provider(const char *path)
80 for (i = 0; i < nhelpers; i++) {
81 if (helpers[i] == NULL || helpers[i]->path == NULL ||
84 if (strcmp(helpers[i]->path, path) == 0)
90 static struct helper *
91 helper_by_rsa(const RSA *rsa)
94 const RSA_METHOD *meth;
96 if ((meth = RSA_get_method(rsa)) == NULL)
98 for (i = 0; i < nhelpers; i++) {
99 if (helpers[i] != NULL && helpers[i]->rsa_meth == meth)
106 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
107 static struct helper *
108 helper_by_ec(const EC_KEY *ec)
111 const EC_KEY_METHOD *meth;
113 if ((meth = EC_KEY_get_method(ec)) == NULL)
115 for (i = 0; i < nhelpers; i++) {
116 if (helpers[i] != NULL && helpers[i]->ec_meth == meth)
122 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
125 helper_free(struct helper *helper)
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) {
139 fatal_f("helper recorded more than once");
143 helpers[i - 1] = helpers[i];
146 helpers = xrecallocarray(helpers, nhelpers,
147 nhelpers - 1, sizeof(*helpers));
151 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
152 EC_KEY_METHOD_free(helper->ec_meth);
154 RSA_meth_free(helper->rsa_meth);
159 helper_terminate(struct helper *helper)
161 if (helper == NULL) {
163 } else if (helper->fd == -1) {
164 debug3_f("already terminated");
166 debug3_f("terminating helper for %s; "
167 "remaining %zu RSA %zu ECDSA",
168 helper->path, helper->nrsa, helper->nec);
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.
179 if (helper->nrsa == 0 && helper->nec == 0)
184 send_msg(int fd, struct sshbuf *m)
187 size_t mlen = sshbuf_len(m);
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");
202 recv_msg(int fd, struct sshbuf *m)
211 if ((len = atomicio(read, fd, buf, 4)) != 4) {
212 error("read from helper failed: %u", len);
213 return (0); /* XXX */
216 if (len > 256 * 1024)
217 fatal("response too long: %u", len);
218 /* read len bytes into m */
223 if (atomicio(read, fd, buf, l) != l) {
224 error("response from helper failed.");
225 return (0); /* XXX */
227 if ((r = sshbuf_put(m, buf, l)) != 0)
228 fatal_fr(r, "sshbuf_put");
231 if ((r = sshbuf_get_u8(m, &c)) != 0)
232 fatal_fr(r, "parse type");
237 pkcs11_init(int interactive)
243 pkcs11_terminate(void)
247 debug3_f("terminating %zu helpers", nhelpers);
248 for (i = 0; i < nhelpers; i++)
249 helper_terminate(helpers[i]);
253 rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
255 struct sshkey *key = NULL;
256 struct sshbuf *msg = NULL;
257 u_char *blob = NULL, *signature = NULL;
258 size_t blen, slen = 0;
260 struct helper *helper;
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)
267 key = sshkey_new(KEY_UNSPEC);
269 error_f("sshkey_new failed");
275 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
276 error_fr(r, "encode key");
279 if ((msg = sshbuf_new()) == NULL)
280 fatal_f("sshbuf_new failed");
281 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
282 (r = sshbuf_put_string(msg, blob, blen)) != 0 ||
283 (r = sshbuf_put_string(msg, from, flen)) != 0 ||
284 (r = sshbuf_put_u32(msg, 0)) != 0)
285 fatal_fr(r, "compose");
286 send_msg(helper->fd, msg);
289 if (recv_msg(helper->fd, msg) == SSH2_AGENT_SIGN_RESPONSE) {
290 if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
291 fatal_fr(r, "parse");
292 if (slen <= (size_t)RSA_size(rsa)) {
293 memcpy(to, signature, slen);
308 struct helper *helper;
310 if ((helper = helper_by_rsa(rsa)) == NULL)
311 fatal_f("no helper for PKCS11 key");
312 debug3_f("free PKCS11 RSA key for provider %s", helper->path);
313 if (helper->rsa_finish != NULL)
314 helper->rsa_finish(rsa);
315 if (helper->nrsa == 0)
316 fatal_f("RSA refcount error");
318 debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
319 helper->path, helper->nrsa, helper->nec);
320 if (helper->nrsa == 0 && helper->nec == 0)
321 helper_terminate(helper);
325 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
327 ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
328 const BIGNUM *rp, EC_KEY *ec)
330 struct sshkey *key = NULL;
331 struct sshbuf *msg = NULL;
332 ECDSA_SIG *ret = NULL;
334 u_char *blob = NULL, *signature = NULL;
335 size_t blen, slen = 0;
337 struct helper *helper;
339 if ((helper = helper_by_ec(ec)) == NULL || helper->fd == -1)
340 fatal_f("no helper for PKCS11 key");
341 debug3_f("signing with PKCS11 provider %s", helper->path);
342 nid = sshkey_ecdsa_key_to_nid(ec);
344 error_f("couldn't get curve nid");
348 key = sshkey_new(KEY_UNSPEC);
350 error_f("sshkey_new failed");
354 key->ecdsa_nid = nid;
355 key->type = KEY_ECDSA;
358 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
359 error_fr(r, "encode key");
362 if ((msg = sshbuf_new()) == NULL)
363 fatal_f("sshbuf_new failed");
364 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
365 (r = sshbuf_put_string(msg, blob, blen)) != 0 ||
366 (r = sshbuf_put_string(msg, dgst, dgst_len)) != 0 ||
367 (r = sshbuf_put_u32(msg, 0)) != 0)
368 fatal_fr(r, "compose");
369 send_msg(helper->fd, msg);
372 if (recv_msg(helper->fd, msg) == SSH2_AGENT_SIGN_RESPONSE) {
373 if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
374 fatal_fr(r, "parse");
376 ret = d2i_ECDSA_SIG(NULL, &cp, slen);
388 ecdsa_do_finish(EC_KEY *ec)
390 struct helper *helper;
392 if ((helper = helper_by_ec(ec)) == NULL)
393 fatal_f("no helper for PKCS11 key");
394 debug3_f("free PKCS11 ECDSA key for provider %s", helper->path);
395 if (helper->ec_finish != NULL)
396 helper->ec_finish(ec);
397 if (helper->nec == 0)
398 fatal_f("ECDSA refcount error");
400 debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
401 helper->path, helper->nrsa, helper->nec);
402 if (helper->nrsa == 0 && helper->nec == 0)
403 helper_terminate(helper);
405 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
407 /* redirect private key crypto operations to the ssh-pkcs11-helper */
409 wrap_key(struct helper *helper, struct sshkey *k)
411 debug3_f("wrap %s for provider %s", sshkey_type(k), helper->path);
412 if (k->type == KEY_RSA) {
413 RSA_set_method(k->rsa, helper->rsa_meth);
414 if (helper->nrsa++ >= INT_MAX)
415 fatal_f("RSA refcount error");
416 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
417 } else if (k->type == KEY_ECDSA) {
418 EC_KEY_set_method(k->ecdsa, helper->ec_meth);
419 if (helper->nec++ >= INT_MAX)
420 fatal_f("EC refcount error");
423 fatal_f("unknown key type");
424 k->flags |= SSHKEY_FLAG_EXT;
425 debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
426 helper->path, helper->nrsa, helper->nec);
430 * Make a private PKCS#11-backed certificate by grafting a previously-loaded
431 * PKCS#11 private key and a public certificate key.
434 pkcs11_make_cert(const struct sshkey *priv,
435 const struct sshkey *certpub, struct sshkey **certprivp)
437 struct helper *helper = NULL;
441 debug3_f("private key type %s cert type %s", sshkey_type(priv),
442 sshkey_type(certpub));
444 if (!sshkey_is_cert(certpub) || sshkey_is_cert(priv) ||
445 !sshkey_equal_public(priv, certpub)) {
446 error_f("private key %s doesn't match cert %s",
447 sshkey_type(priv), sshkey_type(certpub));
448 return SSH_ERR_INVALID_ARGUMENT;
451 if (priv->type == KEY_RSA) {
452 if ((helper = helper_by_rsa(priv->rsa)) == NULL ||
454 fatal_f("no helper for PKCS11 RSA key");
455 if ((r = sshkey_from_private(priv, &ret)) != 0)
456 fatal_fr(r, "copy key");
457 RSA_set_method(ret->rsa, helper->rsa_meth);
458 if (helper->nrsa++ >= INT_MAX)
459 fatal_f("RSA refcount error");
460 } else if (priv->type == KEY_ECDSA) {
461 if ((helper = helper_by_ec(priv->ecdsa)) == NULL ||
463 fatal_f("no helper for PKCS11 EC key");
464 if ((r = sshkey_from_private(priv, &ret)) != 0)
465 fatal_fr(r, "copy key");
466 EC_KEY_set_method(ret->ecdsa, helper->ec_meth);
467 if (helper->nec++ >= INT_MAX)
468 fatal_f("EC refcount error");
470 fatal_f("unknown key type %s", sshkey_type(priv));
472 ret->flags |= SSHKEY_FLAG_EXT;
473 if ((r = sshkey_to_certified(ret)) != 0 ||
474 (r = sshkey_cert_copy(certpub, ret)) != 0)
475 fatal_fr(r, "graft certificate");
476 debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA",
477 helper->path, helper->nrsa, helper->nec);
484 pkcs11_start_helper_methods(struct helper *helper)
486 RSA_METHOD *rsa_meth;
487 EC_KEY_METHOD *ec_meth = NULL;
488 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
489 int (*ec_init)(EC_KEY *key);
490 int (*ec_copy)(EC_KEY *dest, const EC_KEY *src);
491 int (*ec_set_group)(EC_KEY *key, const EC_GROUP *grp);
492 int (*ec_set_private)(EC_KEY *key, const BIGNUM *priv_key);
493 int (*ec_set_public)(EC_KEY *key, const EC_POINT *pub_key);
494 int (*ec_sign)(int, const unsigned char *, int, unsigned char *,
495 unsigned int *, const BIGNUM *, const BIGNUM *, EC_KEY *) = NULL;
497 if ((ec_meth = EC_KEY_METHOD_new(EC_KEY_OpenSSL())) == NULL)
499 EC_KEY_METHOD_get_sign(ec_meth, &ec_sign, NULL, NULL);
500 EC_KEY_METHOD_set_sign(ec_meth, ec_sign, NULL, ecdsa_do_sign);
501 EC_KEY_METHOD_get_init(ec_meth, &ec_init, &helper->ec_finish,
502 &ec_copy, &ec_set_group, &ec_set_private, &ec_set_public);
503 EC_KEY_METHOD_set_init(ec_meth, ec_init, ecdsa_do_finish,
504 ec_copy, ec_set_group, ec_set_private, ec_set_public);
505 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */
507 if ((rsa_meth = RSA_meth_dup(RSA_get_default_method())) == NULL)
508 fatal_f("RSA_meth_dup failed");
509 helper->rsa_finish = RSA_meth_get_finish(rsa_meth);
510 if (!RSA_meth_set1_name(rsa_meth, "ssh-pkcs11-helper") ||
511 !RSA_meth_set_priv_enc(rsa_meth, rsa_encrypt) ||
512 !RSA_meth_set_finish(rsa_meth, rsa_finish))
513 fatal_f("failed to prepare method");
515 helper->ec_meth = ec_meth;
516 helper->rsa_meth = rsa_meth;
520 static struct helper *
521 pkcs11_start_helper(const char *path)
524 char *prog, *verbosity = NULL;
525 struct helper *helper;
528 if (nhelpers >= INT_MAX)
529 fatal_f("too many helpers");
530 debug3_f("start helper for %s", path);
531 if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
532 error_f("socketpair: %s", strerror(errno));
535 helper = xcalloc(1, sizeof(*helper));
536 if (pkcs11_start_helper_methods(helper) == -1) {
537 error_f("pkcs11_start_helper_methods failed");
540 if ((pid = fork()) == -1) {
541 error_f("fork: %s", strerror(errno));
545 RSA_meth_free(helper->rsa_meth);
546 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW)
547 EC_KEY_METHOD_free(helper->ec_meth);
551 } else if (pid == 0) {
552 if ((dup2(pair[1], STDIN_FILENO) == -1) ||
553 (dup2(pair[1], STDOUT_FILENO) == -1)) {
554 fprintf(stderr, "dup2: %s\n", strerror(errno));
559 prog = getenv("SSH_PKCS11_HELPER");
560 if (prog == NULL || strlen(prog) == 0)
561 prog = _PATH_SSH_PKCS11_HELPER;
562 if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)
564 debug_f("starting %s %s", prog,
565 verbosity == NULL ? "" : verbosity);
566 execlp(prog, prog, verbosity, (char *)NULL);
567 fprintf(stderr, "exec: %s: %s\n", prog, strerror(errno));
571 helper->fd = pair[0];
572 helper->path = xstrdup(path);
574 debug3_f("helper %zu for \"%s\" on fd %d pid %ld", nhelpers,
575 helper->path, helper->fd, (long)helper->pid);
576 helpers = xrecallocarray(helpers, nhelpers,
577 nhelpers + 1, sizeof(*helpers));
578 helpers[nhelpers++] = helper;
583 pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
593 struct helper *helper;
595 if ((helper = helper_by_provider(name)) == NULL &&
596 (helper = pkcs11_start_helper(name)) == NULL)
599 if ((msg = sshbuf_new()) == NULL)
600 fatal_f("sshbuf_new failed");
601 if ((r = sshbuf_put_u8(msg, SSH_AGENTC_ADD_SMARTCARD_KEY)) != 0 ||
602 (r = sshbuf_put_cstring(msg, name)) != 0 ||
603 (r = sshbuf_put_cstring(msg, pin)) != 0)
604 fatal_fr(r, "compose");
605 send_msg(helper->fd, msg);
608 type = recv_msg(helper->fd, msg);
609 if (type == SSH2_AGENT_IDENTITIES_ANSWER) {
610 if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
611 fatal_fr(r, "parse nkeys");
612 *keysp = xcalloc(nkeys, sizeof(struct sshkey *));
614 *labelsp = xcalloc(nkeys, sizeof(char *));
615 for (i = 0; i < nkeys; i++) {
616 /* XXX clean up properly instead of fatal() */
617 if ((r = sshbuf_get_string(msg, &blob, &blen)) != 0 ||
618 (r = sshbuf_get_cstring(msg, &label, NULL)) != 0)
619 fatal_fr(r, "parse key");
620 if ((r = sshkey_from_blob(blob, blen, &k)) != 0)
621 fatal_fr(r, "decode key");
625 (*labelsp)[i] = label;
630 } else if (type == SSH2_AGENT_FAILURE) {
631 if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
641 pkcs11_del_provider(char *name)
643 struct helper *helper;
646 * ssh-agent deletes keys before calling this, so the helper entry
647 * should be gone before we get here.
649 debug3_f("delete %s", name);
650 if ((helper = helper_by_provider(name)) != NULL)
651 helper_terminate(helper);
654 #endif /* ENABLE_PKCS11 */