ssh-pkcs11-client.c revision 1.17 
1/*	$NetBSD: ssh-pkcs11-client.c,v 1.17 2021/03/05 17:47:16 christos Exp $	*/
2/* $OpenBSD: ssh-pkcs11-client.c,v 1.17 2020/10/18 11:32:02 djm Exp $ */
3
4/*
5 * Copyright (c) 2010 Markus Friedl.  All rights reserved.
6 * Copyright (c) 2014 Pedro Martelletto. All rights reserved.
7 *
8 * Permission to use, copy, modify, and distribute this software for any
9 * purpose with or without fee is hereby granted, provided that the above
10 * copyright notice and this permission notice appear in all copies.
11 *
12 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
13 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
14 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
15 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
16 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
17 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
18 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
19 */
20#include "includes.h"
21__RCSID("$NetBSD: ssh-pkcs11-client.c,v 1.17 2021/03/05 17:47:16 christos Exp $");
22
23#include <sys/types.h>
24#include <sys/time.h>
25#include <sys/socket.h>
26
27#include <stdarg.h>
28#include <string.h>
29#include <unistd.h>
30#include <errno.h>
31
32#include <openssl/ecdsa.h>
33#include <openssl/rsa.h>
34
35#include "pathnames.h"
36#include "xmalloc.h"
37#include "sshbuf.h"
38#include "log.h"
39#include "misc.h"
40#include "sshkey.h"
41#include "authfd.h"
42#include "atomicio.h"
43#include "ssh-pkcs11.h"
44#include "ssherr.h"
45
46/* borrows code from sftp-server and ssh-agent */
47
48static int fd = -1;
49static pid_t pid = -1;
50
51static void
52send_msg(struct sshbuf *m)
53{
54	u_char buf[4];
55	size_t mlen = sshbuf_len(m);
56	int r;
57
58	POKE_U32(buf, mlen);
59	if (atomicio(vwrite, fd, buf, 4) != 4 ||
60	    atomicio(vwrite, fd, sshbuf_mutable_ptr(m),
61	    sshbuf_len(m)) != sshbuf_len(m))
62		error("write to helper failed");
63	if ((r = sshbuf_consume(m, mlen)) != 0)
64		fatal_fr(r, "consume");
65}
66
67static int
68recv_msg(struct sshbuf *m)
69{
70	u_int l, len;
71	u_char c, buf[1024];
72	int r;
73
74	if ((len = atomicio(read, fd, buf, 4)) != 4) {
75		error("read from helper failed: %u", len);
76		return (0); /* XXX */
77	}
78	len = PEEK_U32(buf);
79	if (len > 256 * 1024)
80		fatal("response too long: %u", len);
81	/* read len bytes into m */
82	sshbuf_reset(m);
83	while (len > 0) {
84		l = len;
85		if (l > sizeof(buf))
86			l = sizeof(buf);
87		if (atomicio(read, fd, buf, l) != l) {
88			error("response from helper failed.");
89			return (0); /* XXX */
90		}
91		if ((r = sshbuf_put(m, buf, l)) != 0)
92			fatal_fr(r, "sshbuf_put");
93		len -= l;
94	}
95	if ((r = sshbuf_get_u8(m, &c)) != 0)
96		fatal_fr(r, "parse type");
97	return c;
98}
99
100int
101pkcs11_init(int interactive)
102{
103	return (0);
104}
105
106void
107pkcs11_terminate(void)
108{
109	if (fd >= 0)
110		close(fd);
111}
112
113static int
114rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding)
115{
116	struct sshkey *key = NULL;
117	struct sshbuf *msg = NULL;
118	u_char *blob = NULL, *signature = NULL;
119	size_t blen, slen = 0;
120	int r, ret = -1;
121
122	if (padding != RSA_PKCS1_PADDING)
123		goto fail;
124	key = sshkey_new(KEY_UNSPEC);
125	if (key == NULL) {
126		error_f("sshkey_new failed");
127		goto fail;
128	}
129	key->type = KEY_RSA;
130	RSA_up_ref(rsa);
131	key->rsa = rsa;
132	if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
133		error_fr(r, "encode key");
134		goto fail;
135	}
136	if ((msg = sshbuf_new()) == NULL)
137		fatal_f("sshbuf_new failed");
138	if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
139	    (r = sshbuf_put_string(msg, blob, blen)) != 0 ||
140	    (r = sshbuf_put_string(msg, from, flen)) != 0 ||
141	    (r = sshbuf_put_u32(msg, 0)) != 0)
142		fatal_fr(r, "compose");
143	send_msg(msg);
144	sshbuf_reset(msg);
145
146	if (recv_msg(msg) == SSH2_AGENT_SIGN_RESPONSE) {
147		if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
148			fatal_fr(r, "parse");
149		if (slen <= (size_t)RSA_size(rsa)) {
150			memcpy(to, signature, slen);
151			ret = slen;
152		}
153		free(signature);
154	}
155 fail:
156	free(blob);
157	sshkey_free(key);
158	sshbuf_free(msg);
159	return (ret);
160}
161
162static ECDSA_SIG *
163ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv,
164    const BIGNUM *rp, EC_KEY *ec)
165{
166	struct sshkey *key = NULL;
167	struct sshbuf *msg = NULL;
168	ECDSA_SIG *ret = NULL;
169	const u_char *cp;
170	u_char *blob = NULL, *signature = NULL;
171	size_t blen, slen = 0;
172	int r, nid;
173
174	nid = sshkey_ecdsa_key_to_nid(ec);
175	if (nid < 0) {
176		error_f("couldn't get curve nid");
177		goto fail;
178	}
179
180	key = sshkey_new(KEY_UNSPEC);
181	if (key == NULL) {
182		error_f("sshkey_new failed");
183		goto fail;
184	}
185	key->ecdsa = ec;
186	key->ecdsa_nid = nid;
187	key->type = KEY_ECDSA;
188	EC_KEY_up_ref(ec);
189
190	if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) {
191		error_fr(r, "encode key");
192		goto fail;
193	}
194	if ((msg = sshbuf_new()) == NULL)
195		fatal_f("sshbuf_new failed");
196	if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
197	    (r = sshbuf_put_string(msg, blob, blen)) != 0 ||
198	    (r = sshbuf_put_string(msg, dgst, dgst_len)) != 0 ||
199	    (r = sshbuf_put_u32(msg, 0)) != 0)
200		fatal_fr(r, "compose");
201	send_msg(msg);
202	sshbuf_reset(msg);
203
204	if (recv_msg(msg) == SSH2_AGENT_SIGN_RESPONSE) {
205		if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0)
206			fatal_fr(r, "parse");
207		cp = signature;
208		ret = d2i_ECDSA_SIG(NULL, &cp, slen);
209		free(signature);
210	}
211
212 fail:
213	free(blob);
214	sshkey_free(key);
215	sshbuf_free(msg);
216	return (ret);
217}
218
219static RSA_METHOD	*helper_rsa;
220static EC_KEY_METHOD	*helper_ecdsa;
221
222/* redirect private key crypto operations to the ssh-pkcs11-helper */
223static void
224wrap_key(struct sshkey *k)
225{
226	if (k->type == KEY_RSA)
227		RSA_set_method(k->rsa, helper_rsa);
228	else if (k->type == KEY_ECDSA)
229		EC_KEY_set_method(k->ecdsa, helper_ecdsa);
230	else
231		fatal_f("unknown key type");
232}
233
234static int
235pkcs11_start_helper_methods(void)
236{
237	if (helper_ecdsa != NULL)
238		return (0);
239
240	int (*orig_sign)(int, const unsigned char *, int, unsigned char *,
241	    unsigned int *, const BIGNUM *, const BIGNUM *, EC_KEY *) = NULL;
242	if (helper_ecdsa != NULL)
243		return (0);
244	helper_ecdsa = EC_KEY_METHOD_new(EC_KEY_OpenSSL());
245	if (helper_ecdsa == NULL)
246		return (-1);
247	EC_KEY_METHOD_get_sign(helper_ecdsa, &orig_sign, NULL, NULL);
248	EC_KEY_METHOD_set_sign(helper_ecdsa, orig_sign, NULL, ecdsa_do_sign);
249
250	if ((helper_rsa = RSA_meth_dup(RSA_get_default_method())) == NULL)
251		fatal_f("RSA_meth_dup failed");
252	if (!RSA_meth_set1_name(helper_rsa, "ssh-pkcs11-helper") ||
253	    !RSA_meth_set_priv_enc(helper_rsa, rsa_encrypt))
254		fatal_f("failed to prepare method");
255
256	return (0);
257}
258
259static int
260pkcs11_start_helper(void)
261{
262	int pair[2];
263	const char *helper, *verbosity = NULL;
264
265	if (log_level_get() >= SYSLOG_LEVEL_DEBUG1)
266		verbosity = "-vvv";
267
268	if (pkcs11_start_helper_methods() == -1) {
269		error("pkcs11_start_helper_methods failed");
270		return (-1);
271	}
272
273	if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) {
274		error("socketpair: %s", strerror(errno));
275		return (-1);
276	}
277	if ((pid = fork()) == -1) {
278		error("fork: %s", strerror(errno));
279		return (-1);
280	} else if (pid == 0) {
281		if ((dup2(pair[1], STDIN_FILENO) == -1) ||
282		    (dup2(pair[1], STDOUT_FILENO) == -1)) {
283			fprintf(stderr, "dup2: %s\n", strerror(errno));
284			_exit(1);
285		}
286		close(pair[0]);
287		close(pair[1]);
288		helper = getenv("SSH_PKCS11_HELPER");
289		if (helper == NULL || strlen(helper) == 0)
290			helper = _PATH_SSH_PKCS11_HELPER;
291		debug_f("starting %s %s", helper,
292		    verbosity == NULL ? "" : verbosity);
293		execlp(helper, helper, verbosity, (char *)NULL);
294		fprintf(stderr, "exec: %s: %s\n", helper, strerror(errno));
295		_exit(1);
296	}
297	close(pair[1]);
298	fd = pair[0];
299	return (0);
300}
301
302int
303pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp,
304    char ***labelsp)
305{
306	struct sshkey *k;
307	int r, type;
308	u_char *blob;
309	char *label;
310	size_t blen;
311	u_int nkeys, i;
312	struct sshbuf *msg;
313
314	if (fd < 0 && pkcs11_start_helper() < 0)
315		return (-1);
316
317	if ((msg = sshbuf_new()) == NULL)
318		fatal_f("sshbuf_new failed");
319	if ((r = sshbuf_put_u8(msg, SSH_AGENTC_ADD_SMARTCARD_KEY)) != 0 ||
320	    (r = sshbuf_put_cstring(msg, name)) != 0 ||
321	    (r = sshbuf_put_cstring(msg, pin)) != 0)
322		fatal_fr(r, "compose");
323	send_msg(msg);
324	sshbuf_reset(msg);
325
326	type = recv_msg(msg);
327	if (type == SSH2_AGENT_IDENTITIES_ANSWER) {
328		if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
329			fatal_fr(r, "parse nkeys");
330		*keysp = xcalloc(nkeys, sizeof(struct sshkey *));
331		if (labelsp)
332			*labelsp = xcalloc(nkeys, sizeof(char *));
333		for (i = 0; i < nkeys; i++) {
334			/* XXX clean up properly instead of fatal() */
335			if ((r = sshbuf_get_string(msg, &blob, &blen)) != 0 ||
336			    (r = sshbuf_get_cstring(msg, &label, NULL)) != 0)
337				fatal_fr(r, "parse key");
338			if ((r = sshkey_from_blob(blob, blen, &k)) != 0)
339				fatal_fr(r, "decode key");
340			wrap_key(k);
341			(*keysp)[i] = k;
342			if (labelsp)
343				(*labelsp)[i] = label;
344			else
345				free(label);
346			free(blob);
347		}
348	} else if (type == SSH2_AGENT_FAILURE) {
349		if ((r = sshbuf_get_u32(msg, &nkeys)) != 0)
350			nkeys = -1;
351	} else {
352		nkeys = -1;
353	}
354	sshbuf_free(msg);
355	return (nkeys);
356}
357
358int
359pkcs11_del_provider(char *name)
360{
361	int r, ret = -1;
362	struct sshbuf *msg;
363
364	if ((msg = sshbuf_new()) == NULL)
365		fatal_f("sshbuf_new failed");
366	if ((r = sshbuf_put_u8(msg, SSH_AGENTC_REMOVE_SMARTCARD_KEY)) != 0 ||
367	    (r = sshbuf_put_cstring(msg, name)) != 0 ||
368	    (r = sshbuf_put_cstring(msg, "")) != 0)
369		fatal_fr(r, "compose");
370	send_msg(msg);
371	sshbuf_reset(msg);
372
373	if (recv_msg(msg) == SSH_AGENT_SUCCESS)
374		ret = 0;
375	sshbuf_free(msg);
376	return (ret);
377}
378