1 /* $OpenBSD: ssh-pkcs11-helper.c,v 1.13 2017/05/30 08:52:19 markus Exp $ */
2 /*
3  * Copyright (c) 2010 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 <sys/types.h>
21 #ifdef HAVE_SYS_TIME_H
22 # include <sys/time.h>
23 #endif
24 
25 #include "openbsd-compat/sys-queue.h"
26 
27 #include <stdarg.h>
28 #include <string.h>
29 #include <unistd.h>
30 #include <errno.h>
31 
32 #include "xmalloc.h"
33 #include "buffer.h"
34 #include "log.h"
35 #include "misc.h"
36 #include "key.h"
37 #include "authfd.h"
38 #include "ssh-pkcs11.h"
39 
40 #ifdef ENABLE_PKCS11
41 
42 /* borrows code from sftp-server and ssh-agent */
43 
44 struct pkcs11_keyinfo {
45 	struct sshkey	*key;
46 	char		*providername;
47 	TAILQ_ENTRY(pkcs11_keyinfo) next;
48 };
49 
50 TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
51 
52 #define MAX_MSG_LENGTH		10240 /*XXX*/
53 
54 /* helper */
55 #define get_int()			buffer_get_int(&iqueue);
56 #define get_string(lenp)		buffer_get_string(&iqueue, lenp);
57 
58 /* input and output queue */
59 Buffer iqueue;
60 Buffer oqueue;
61 
62 static void
63 add_key(struct sshkey *k, char *name)
64 {
65 	struct pkcs11_keyinfo *ki;
66 
67 	ki = xcalloc(1, sizeof(*ki));
68 	ki->providername = xstrdup(name);
69 	ki->key = k;
70 	TAILQ_INSERT_TAIL(&pkcs11_keylist, ki, next);
71 }
72 
73 static void
74 del_keys_by_name(char *name)
75 {
76 	struct pkcs11_keyinfo *ki, *nxt;
77 
78 	for (ki = TAILQ_FIRST(&pkcs11_keylist); ki; ki = nxt) {
79 		nxt = TAILQ_NEXT(ki, next);
80 		if (!strcmp(ki->providername, name)) {
81 			TAILQ_REMOVE(&pkcs11_keylist, ki, next);
82 			free(ki->providername);
83 			key_free(ki->key);
84 			free(ki);
85 		}
86 	}
87 }
88 
89 /* lookup matching 'private' key */
90 static struct sshkey *
91 lookup_key(struct sshkey *k)
92 {
93 	struct pkcs11_keyinfo *ki;
94 
95 	TAILQ_FOREACH(ki, &pkcs11_keylist, next) {
96 		debug("check %p %s", ki, ki->providername);
97 		if (key_equal(k, ki->key))
98 			return (ki->key);
99 	}
100 	return (NULL);
101 }
102 
103 static void
104 send_msg(Buffer *m)
105 {
106 	int mlen = buffer_len(m);
107 
108 	buffer_put_int(&oqueue, mlen);
109 	buffer_append(&oqueue, buffer_ptr(m), mlen);
110 	buffer_consume(m, mlen);
111 }
112 
113 static void
114 process_add(void)
115 {
116 	char *name, *pin;
117 	struct sshkey **keys;
118 	int i, nkeys;
119 	u_char *blob;
120 	u_int blen;
121 	Buffer msg;
122 
123 	buffer_init(&msg);
124 	name = get_string(NULL);
125 	pin = get_string(NULL);
126 	if ((nkeys = pkcs11_add_provider(name, pin, &keys)) > 0) {
127 		buffer_put_char(&msg, SSH2_AGENT_IDENTITIES_ANSWER);
128 		buffer_put_int(&msg, nkeys);
129 		for (i = 0; i < nkeys; i++) {
130 			if (key_to_blob(keys[i], &blob, &blen) == 0)
131 				continue;
132 			buffer_put_string(&msg, blob, blen);
133 			buffer_put_cstring(&msg, name);
134 			free(blob);
135 			add_key(keys[i], name);
136 		}
137 		free(keys);
138 	} else {
139 		buffer_put_char(&msg, SSH_AGENT_FAILURE);
140 	}
141 	free(pin);
142 	free(name);
143 	send_msg(&msg);
144 	buffer_free(&msg);
145 }
146 
147 static void
148 process_del(void)
149 {
150 	char *name, *pin;
151 	Buffer msg;
152 
153 	buffer_init(&msg);
154 	name = get_string(NULL);
155 	pin = get_string(NULL);
156 	del_keys_by_name(name);
157 	if (pkcs11_del_provider(name) == 0)
158 		 buffer_put_char(&msg, SSH_AGENT_SUCCESS);
159 	else
160 		 buffer_put_char(&msg, SSH_AGENT_FAILURE);
161 	free(pin);
162 	free(name);
163 	send_msg(&msg);
164 	buffer_free(&msg);
165 }
166 
167 static void
168 process_sign(void)
169 {
170 	u_char *blob, *data, *signature = NULL;
171 	u_int blen, dlen, slen = 0;
172 	int ok = -1;
173 	struct sshkey *key, *found;
174 	Buffer msg;
175 
176 	blob = get_string(&blen);
177 	data = get_string(&dlen);
178 	(void)get_int(); /* XXX ignore flags */
179 
180 	if ((key = key_from_blob(blob, blen)) != NULL) {
181 		if ((found = lookup_key(key)) != NULL) {
182 #ifdef WITH_OPENSSL
183 			int ret;
184 
185 			slen = RSA_size(key->rsa);
186 			signature = xmalloc(slen);
187 			if ((ret = RSA_private_encrypt(dlen, data, signature,
188 			    found->rsa, RSA_PKCS1_PADDING)) != -1) {
189 				slen = ret;
190 				ok = 0;
191 			}
192 #endif /* WITH_OPENSSL */
193 		}
194 		key_free(key);
195 	}
196 	buffer_init(&msg);
197 	if (ok == 0) {
198 		buffer_put_char(&msg, SSH2_AGENT_SIGN_RESPONSE);
199 		buffer_put_string(&msg, signature, slen);
200 	} else {
201 		buffer_put_char(&msg, SSH_AGENT_FAILURE);
202 	}
203 	free(data);
204 	free(blob);
205 	free(signature);
206 	send_msg(&msg);
207 	buffer_free(&msg);
208 }
209 
210 static void
211 process(void)
212 {
213 	u_int msg_len;
214 	u_int buf_len;
215 	u_int consumed;
216 	u_int type;
217 	u_char *cp;
218 
219 	buf_len = buffer_len(&iqueue);
220 	if (buf_len < 5)
221 		return;		/* Incomplete message. */
222 	cp = buffer_ptr(&iqueue);
223 	msg_len = get_u32(cp);
224 	if (msg_len > MAX_MSG_LENGTH) {
225 		error("bad message len %d", msg_len);
226 		cleanup_exit(11);
227 	}
228 	if (buf_len < msg_len + 4)
229 		return;
230 	buffer_consume(&iqueue, 4);
231 	buf_len -= 4;
232 	type = buffer_get_char(&iqueue);
233 	switch (type) {
234 	case SSH_AGENTC_ADD_SMARTCARD_KEY:
235 		debug("process_add");
236 		process_add();
237 		break;
238 	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
239 		debug("process_del");
240 		process_del();
241 		break;
242 	case SSH2_AGENTC_SIGN_REQUEST:
243 		debug("process_sign");
244 		process_sign();
245 		break;
246 	default:
247 		error("Unknown message %d", type);
248 		break;
249 	}
250 	/* discard the remaining bytes from the current packet */
251 	if (buf_len < buffer_len(&iqueue)) {
252 		error("iqueue grew unexpectedly");
253 		cleanup_exit(255);
254 	}
255 	consumed = buf_len - buffer_len(&iqueue);
256 	if (msg_len < consumed) {
257 		error("msg_len %d < consumed %d", msg_len, consumed);
258 		cleanup_exit(255);
259 	}
260 	if (msg_len > consumed)
261 		buffer_consume(&iqueue, msg_len - consumed);
262 }
263 
264 void
265 cleanup_exit(int i)
266 {
267 	/* XXX */
268 	_exit(i);
269 }
270 
271 int
272 main(int argc, char **argv)
273 {
274 	fd_set *rset, *wset;
275 	int in, out, max, log_stderr = 0;
276 	ssize_t len, olen, set_size;
277 	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
278 	LogLevel log_level = SYSLOG_LEVEL_ERROR;
279 	char buf[4*4096];
280 
281 	extern char *__progname;
282 
283 	ssh_malloc_init();	/* must be called before any mallocs */
284 	TAILQ_INIT(&pkcs11_keylist);
285 	pkcs11_init(0);
286 
287 	seed_rng();
288 	__progname = ssh_get_progname(argv[0]);
289 
290 	log_init(__progname, log_level, log_facility, log_stderr);
291 
292 	in = STDIN_FILENO;
293 	out = STDOUT_FILENO;
294 
295 	max = 0;
296 	if (in > max)
297 		max = in;
298 	if (out > max)
299 		max = out;
300 
301 	buffer_init(&iqueue);
302 	buffer_init(&oqueue);
303 
304 	set_size = howmany(max + 1, NFDBITS) * sizeof(fd_mask);
305 	rset = xmalloc(set_size);
306 	wset = xmalloc(set_size);
307 
308 	for (;;) {
309 		memset(rset, 0, set_size);
310 		memset(wset, 0, set_size);
311 
312 		/*
313 		 * Ensure that we can read a full buffer and handle
314 		 * the worst-case length packet it can generate,
315 		 * otherwise apply backpressure by stopping reads.
316 		 */
317 		if (buffer_check_alloc(&iqueue, sizeof(buf)) &&
318 		    buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
319 			FD_SET(in, rset);
320 
321 		olen = buffer_len(&oqueue);
322 		if (olen > 0)
323 			FD_SET(out, wset);
324 
325 		if (select(max+1, rset, wset, NULL, NULL) < 0) {
326 			if (errno == EINTR)
327 				continue;
328 			error("select: %s", strerror(errno));
329 			cleanup_exit(2);
330 		}
331 
332 		/* copy stdin to iqueue */
333 		if (FD_ISSET(in, rset)) {
334 			len = read(in, buf, sizeof buf);
335 			if (len == 0) {
336 				debug("read eof");
337 				cleanup_exit(0);
338 			} else if (len < 0) {
339 				error("read: %s", strerror(errno));
340 				cleanup_exit(1);
341 			} else {
342 				buffer_append(&iqueue, buf, len);
343 			}
344 		}
345 		/* send oqueue to stdout */
346 		if (FD_ISSET(out, wset)) {
347 			len = write(out, buffer_ptr(&oqueue), olen);
348 			if (len < 0) {
349 				error("write: %s", strerror(errno));
350 				cleanup_exit(1);
351 			} else {
352 				buffer_consume(&oqueue, len);
353 			}
354 		}
355 
356 		/*
357 		 * Process requests from client if we can fit the results
358 		 * into the output buffer, otherwise stop processing input
359 		 * and let the output queue drain.
360 		 */
361 		if (buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
362 			process();
363 	}
364 }
365 #else /* ENABLE_PKCS11 */
366 int
367 main(int argc, char **argv)
368 {
369 	extern char *__progname;
370 
371 	__progname = ssh_get_progname(argv[0]);
372 	log_init(__progname, SYSLOG_LEVEL_ERROR, SYSLOG_FACILITY_AUTH, 0);
373 	fatal("PKCS#11 support disabled at compile time");
374 }
375 #endif /* ENABLE_PKCS11 */
376