1 /* $NetBSD: ssh-pkcs11-helper.c,v 1.21 2021/09/02 11:26:18 christos Exp $ */ 2 /* $OpenBSD: ssh-pkcs11-helper.c,v 1.25 2021/08/11 05:20:17 djm Exp $ */ 3 4 /* 5 * Copyright (c) 2010 Markus Friedl. All rights reserved. 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 #include "includes.h" 20 __RCSID("$NetBSD: ssh-pkcs11-helper.c,v 1.21 2021/09/02 11:26:18 christos Exp $"); 21 22 #include <sys/types.h> 23 #include <sys/queue.h> 24 #include <sys/time.h> 25 #include <sys/param.h> 26 27 #include <stdlib.h> 28 #include <errno.h> 29 #include <poll.h> 30 #include <stdarg.h> 31 #include <string.h> 32 #include <unistd.h> 33 34 #include "xmalloc.h" 35 #include "sshbuf.h" 36 #include "log.h" 37 #include "misc.h" 38 #include "sshkey.h" 39 #include "authfd.h" 40 #include "ssh-pkcs11.h" 41 #include "ssherr.h" 42 43 #ifdef WITH_OPENSSL 44 45 /* borrows code from sftp-server and ssh-agent */ 46 47 struct pkcs11_keyinfo { 48 struct sshkey *key; 49 char *providername, *label; 50 TAILQ_ENTRY(pkcs11_keyinfo) next; 51 }; 52 53 TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist; 54 55 #define MAX_MSG_LENGTH 10240 /*XXX*/ 56 57 /* input and output queue */ 58 struct sshbuf *iqueue; 59 struct sshbuf *oqueue; 60 61 static void 62 add_key(struct sshkey *k, char *name, char *label) 63 { 64 struct pkcs11_keyinfo *ki; 65 66 ki = xcalloc(1, sizeof(*ki)); 67 ki->providername = xstrdup(name); 68 ki->key = k; 69 ki->label = xstrdup(label); 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 free(ki->label); 84 sshkey_free(ki->key); 85 free(ki); 86 } 87 } 88 } 89 90 /* lookup matching 'private' key */ 91 static struct sshkey * 92 lookup_key(struct sshkey *k) 93 { 94 struct pkcs11_keyinfo *ki; 95 96 TAILQ_FOREACH(ki, &pkcs11_keylist, next) { 97 debug("check %s %s %s", sshkey_type(ki->key), 98 ki->providername, ki->label); 99 if (sshkey_equal(k, ki->key)) 100 return (ki->key); 101 } 102 return (NULL); 103 } 104 105 static void 106 send_msg(struct sshbuf *m) 107 { 108 int r; 109 110 if ((r = sshbuf_put_stringb(oqueue, m)) != 0) 111 fatal_fr(r, "enqueue"); 112 } 113 114 static void 115 process_add(void) 116 { 117 char *name, *pin; 118 struct sshkey **keys = NULL; 119 int r, i, nkeys; 120 u_char *blob; 121 size_t blen; 122 struct sshbuf *msg; 123 char **labels = NULL; 124 125 if ((msg = sshbuf_new()) == NULL) 126 fatal_f("sshbuf_new failed"); 127 if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 || 128 (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0) 129 fatal_fr(r, "parse"); 130 if ((nkeys = pkcs11_add_provider(name, pin, &keys, &labels)) > 0) { 131 if ((r = sshbuf_put_u8(msg, 132 SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 133 (r = sshbuf_put_u32(msg, nkeys)) != 0) 134 fatal_fr(r, "compose"); 135 for (i = 0; i < nkeys; i++) { 136 if ((r = sshkey_to_blob(keys[i], &blob, &blen)) != 0) { 137 debug_fr(r, "encode key"); 138 continue; 139 } 140 if ((r = sshbuf_put_string(msg, blob, blen)) != 0 || 141 (r = sshbuf_put_cstring(msg, labels[i])) != 0) 142 fatal_fr(r, "compose key"); 143 free(blob); 144 add_key(keys[i], name, labels[i]); 145 free(labels[i]); 146 } 147 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0 || 148 (r = sshbuf_put_u32(msg, -nkeys)) != 0) 149 fatal_fr(r, "compose"); 150 free(labels); 151 free(keys); /* keys themselves are transferred to pkcs11_keylist */ 152 free(pin); 153 free(name); 154 send_msg(msg); 155 sshbuf_free(msg); 156 } 157 158 static void 159 process_del(void) 160 { 161 char *name, *pin; 162 struct sshbuf *msg; 163 int r; 164 165 if ((msg = sshbuf_new()) == NULL) 166 fatal_f("sshbuf_new failed"); 167 if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 || 168 (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0) 169 fatal_fr(r, "parse"); 170 del_keys_by_name(name); 171 if ((r = sshbuf_put_u8(msg, pkcs11_del_provider(name) == 0 ? 172 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0) 173 fatal_fr(r, "compose"); 174 free(pin); 175 free(name); 176 send_msg(msg); 177 sshbuf_free(msg); 178 } 179 180 static void 181 process_sign(void) 182 { 183 u_char *blob, *data, *signature = NULL; 184 size_t blen, dlen, slen = 0; 185 int r, ok = -1; 186 struct sshkey *key, *found; 187 struct sshbuf *msg; 188 189 /* XXX support SHA2 signature flags */ 190 if ((r = sshbuf_get_string(iqueue, &blob, &blen)) != 0 || 191 (r = sshbuf_get_string(iqueue, &data, &dlen)) != 0 || 192 (r = sshbuf_get_u32(iqueue, NULL)) != 0) 193 fatal_fr(r, "parse"); 194 195 if ((r = sshkey_from_blob(blob, blen, &key)) != 0) 196 fatal_fr(r, "decode key"); 197 else { 198 if ((found = lookup_key(key)) != NULL) { 199 #ifdef WITH_OPENSSL 200 int ret; 201 202 if (key->type == KEY_RSA) { 203 slen = RSA_size(key->rsa); 204 signature = xmalloc(slen); 205 ret = RSA_private_encrypt(dlen, data, signature, 206 found->rsa, RSA_PKCS1_PADDING); 207 if (ret != -1) { 208 slen = ret; 209 ok = 0; 210 } 211 } else if (key->type == KEY_ECDSA) { 212 u_int xslen = ECDSA_size(key->ecdsa); 213 214 signature = xmalloc(xslen); 215 /* "The parameter type is ignored." */ 216 ret = ECDSA_sign(-1, data, dlen, signature, 217 &xslen, found->ecdsa); 218 if (ret != 0) 219 ok = 0; 220 else 221 error_f("ECDSA_sign returned %d", ret); 222 slen = xslen; 223 } else 224 error_f("don't know how to sign with key " 225 "type %d", (int)key->type); 226 #endif /* WITH_OPENSSL */ 227 } 228 sshkey_free(key); 229 } 230 if ((msg = sshbuf_new()) == NULL) 231 fatal_f("sshbuf_new failed"); 232 if (ok == 0) { 233 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 234 (r = sshbuf_put_string(msg, signature, slen)) != 0) 235 fatal_fr(r, "compose response"); 236 } else { 237 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_FAILURE)) != 0) 238 fatal_fr(r, "compose failure response"); 239 } 240 free(data); 241 free(blob); 242 free(signature); 243 send_msg(msg); 244 sshbuf_free(msg); 245 } 246 247 static void 248 process(void) 249 { 250 u_int msg_len; 251 u_int buf_len; 252 u_int consumed; 253 u_char type; 254 const u_char *cp; 255 int r; 256 257 buf_len = sshbuf_len(iqueue); 258 if (buf_len < 5) 259 return; /* Incomplete message. */ 260 cp = sshbuf_ptr(iqueue); 261 msg_len = get_u32(cp); 262 if (msg_len > MAX_MSG_LENGTH) { 263 error("bad message len %d", msg_len); 264 cleanup_exit(11); 265 } 266 if (buf_len < msg_len + 4) 267 return; 268 if ((r = sshbuf_consume(iqueue, 4)) != 0 || 269 (r = sshbuf_get_u8(iqueue, &type)) != 0) 270 fatal_fr(r, "parse type/len"); 271 buf_len -= 4; 272 switch (type) { 273 case SSH_AGENTC_ADD_SMARTCARD_KEY: 274 debug("process_add"); 275 process_add(); 276 break; 277 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 278 debug("process_del"); 279 process_del(); 280 break; 281 case SSH2_AGENTC_SIGN_REQUEST: 282 debug("process_sign"); 283 process_sign(); 284 break; 285 default: 286 error("Unknown message %d", type); 287 break; 288 } 289 /* discard the remaining bytes from the current packet */ 290 if (buf_len < sshbuf_len(iqueue)) { 291 error("iqueue grew unexpectedly"); 292 cleanup_exit(255); 293 } 294 consumed = buf_len - sshbuf_len(iqueue); 295 if (msg_len < consumed) { 296 error("msg_len %d < consumed %d", msg_len, consumed); 297 cleanup_exit(255); 298 } 299 if (msg_len > consumed) { 300 if ((r = sshbuf_consume(iqueue, msg_len - consumed)) != 0) 301 fatal_fr(r, "consume"); 302 } 303 } 304 305 void 306 cleanup_exit(int i) 307 { 308 /* XXX */ 309 _exit(i); 310 } 311 312 313 int 314 main(int argc, char **argv) 315 { 316 int r, ch, in, out, log_stderr = 0; 317 ssize_t len; 318 SyslogFacility log_facility = SYSLOG_FACILITY_AUTH; 319 LogLevel log_level = SYSLOG_LEVEL_ERROR; 320 char buf[4*4096]; 321 extern char *__progname; 322 struct pollfd pfd[2]; 323 324 TAILQ_INIT(&pkcs11_keylist); 325 326 log_init(__progname, log_level, log_facility, log_stderr); 327 328 while ((ch = getopt(argc, argv, "v")) != -1) { 329 switch (ch) { 330 case 'v': 331 log_stderr = 1; 332 if (log_level == SYSLOG_LEVEL_ERROR) 333 log_level = SYSLOG_LEVEL_DEBUG1; 334 else if (log_level < SYSLOG_LEVEL_DEBUG3) 335 log_level++; 336 break; 337 default: 338 fprintf(stderr, "usage: %s [-v]\n", __progname); 339 exit(1); 340 } 341 } 342 343 log_init(__progname, log_level, log_facility, log_stderr); 344 345 pkcs11_init(0); 346 in = STDIN_FILENO; 347 out = STDOUT_FILENO; 348 349 if ((iqueue = sshbuf_new()) == NULL) 350 fatal_f("sshbuf_new failed"); 351 if ((oqueue = sshbuf_new()) == NULL) 352 fatal_f("sshbuf_new failed"); 353 354 while (1) { 355 memset(pfd, 0, sizeof(pfd)); 356 pfd[0].fd = in; 357 pfd[1].fd = out; 358 359 /* 360 * Ensure that we can read a full buffer and handle 361 * the worst-case length packet it can generate, 362 * otherwise apply backpressure by stopping reads. 363 */ 364 if ((r = sshbuf_check_reserve(iqueue, sizeof(buf))) == 0 && 365 (r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0) 366 pfd[0].events = POLLIN; 367 else if (r != SSH_ERR_NO_BUFFER_SPACE) 368 fatal_fr(r, "reserve"); 369 370 if (sshbuf_len(oqueue) > 0) 371 pfd[1].events = POLLOUT; 372 373 if ((r = poll(pfd, 2, -1 /* INFTIM */)) <= 0) { 374 if (r == 0 || errno == EINTR) 375 continue; 376 fatal("poll: %s", strerror(errno)); 377 } 378 379 /* copy stdin to iqueue */ 380 if ((pfd[0].revents & (POLLIN|POLLERR)) != 0) { 381 len = read(in, buf, sizeof buf); 382 if (len == 0) { 383 debug("read eof"); 384 cleanup_exit(0); 385 } else if (len < 0) { 386 error("read: %s", strerror(errno)); 387 cleanup_exit(1); 388 } else if ((r = sshbuf_put(iqueue, buf, len)) != 0) 389 fatal_fr(r, "sshbuf_put"); 390 } 391 /* send oqueue to stdout */ 392 if ((pfd[1].revents & (POLLOUT|POLLHUP)) != 0) { 393 len = write(out, sshbuf_ptr(oqueue), 394 sshbuf_len(oqueue)); 395 if (len < 0) { 396 error("write: %s", strerror(errno)); 397 cleanup_exit(1); 398 } else if ((r = sshbuf_consume(oqueue, len)) != 0) 399 fatal_fr(r, "consume"); 400 } 401 402 /* 403 * Process requests from client if we can fit the results 404 * into the output buffer, otherwise stop processing input 405 * and let the output queue drain. 406 */ 407 if ((r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0) 408 process(); 409 else if (r != SSH_ERR_NO_BUFFER_SPACE) 410 fatal_fr(r, "reserve"); 411 } 412 } 413 414 #else /* WITH_OPENSSL */ 415 void 416 cleanup_exit(int i) 417 { 418 _exit(i); 419 } 420 421 int 422 main(int argc, char **argv) 423 { 424 fprintf(stderr, "PKCS#11 code is not enabled\n"); 425 return 1; 426 } 427 #endif /* WITH_OPENSSL */ 428