crypto/openssh/ssh-pkcs11-helper.c

   1 /* $OpenBSD: ssh-pkcs11-helper.c,v 1.26 2021/11/18 03:31:44 djm 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 <stdlib.h>
  28 #include <errno.h>
  29 #ifdef HAVE_POLL_H
  30 #include <poll.h>
  31 #endif
  32 #include <stdarg.h>
  33 #include <string.h>
  34 #include <unistd.h>
  35
  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 "ssh-pkcs11.h"
  43 #include "ssherr.h"
  44
  45 #ifdef ENABLE_PKCS11
  46
  47 #ifdef WITH_OPENSSL
  48
  49 /* borrows code from sftp-server and ssh-agent */
  50
  51 struct pkcs11_keyinfo {
  52         struct sshkey   *key;
  53         char            *providername, *label;
  54         TAILQ_ENTRY(pkcs11_keyinfo) next;
  55 };
  56
  57 TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
  58
  59 #define MAX_MSG_LENGTH          10240 /*XXX*/
  60
  61 /* input and output queue */
  62 struct sshbuf *iqueue;
  63 struct sshbuf *oqueue;
  64
  65 static void
  66 add_key(struct sshkey *k, char *name, char *label)
  67 {
  68         struct pkcs11_keyinfo *ki;
  69
  70         ki = xcalloc(1, sizeof(*ki));
  71         ki->providername = xstrdup(name);
  72         ki->key = k;
  73         ki->label = xstrdup(label);
  74         TAILQ_INSERT_TAIL(&pkcs11_keylist, ki, next);
  75 }
  76
  77 static void
  78 del_keys_by_name(char *name)
  79 {
  80         struct pkcs11_keyinfo *ki, *nxt;
  81
  82         for (ki = TAILQ_FIRST(&pkcs11_keylist); ki; ki = nxt) {
  83                 nxt = TAILQ_NEXT(ki, next);
  84                 if (!strcmp(ki->providername, name)) {
  85                         TAILQ_REMOVE(&pkcs11_keylist, ki, next);
  86                         free(ki->providername);
  87                         free(ki->label);
  88                         sshkey_free(ki->key);
  89                         free(ki);
  90                 }
  91         }
  92 }
  93
  94 /* lookup matching 'private' key */
  95 static struct sshkey *
  96 lookup_key(struct sshkey *k)
  97 {
  98         struct pkcs11_keyinfo *ki;
  99
 100         TAILQ_FOREACH(ki, &pkcs11_keylist, next) {
 101                 debug("check %s %s %s", sshkey_type(ki->key),
 102                     ki->providername, ki->label);
 103                 if (sshkey_equal(k, ki->key))
 104                         return (ki->key);
 105         }
 106         return (NULL);
 107 }
 108
 109 static void
 110 send_msg(struct sshbuf *m)
 111 {
 112         int r;
 113
 114         if ((r = sshbuf_put_stringb(oqueue, m)) != 0)
 115                 fatal_fr(r, "enqueue");
 116 }
 117
 118 static void
 119 process_add(void)
 120 {
 121         char *name, *pin;
 122         struct sshkey **keys = NULL;
 123         int r, i, nkeys;
 124         u_char *blob;
 125         size_t blen;
 126         struct sshbuf *msg;
 127         char **labels = NULL;
 128
 129         if ((msg = sshbuf_new()) == NULL)
 130                 fatal_f("sshbuf_new failed");
 131         if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
 132             (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0)
 133                 fatal_fr(r, "parse");
 134         if ((nkeys = pkcs11_add_provider(name, pin, &keys, &labels)) > 0) {
 135                 if ((r = sshbuf_put_u8(msg,
 136                     SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
 137                     (r = sshbuf_put_u32(msg, nkeys)) != 0)
 138                         fatal_fr(r, "compose");
 139                 for (i = 0; i < nkeys; i++) {
 140                         if ((r = sshkey_to_blob(keys[i], &blob, &blen)) != 0) {
 141                                 debug_fr(r, "encode key");
 142                                 continue;
 143                         }
 144                         if ((r = sshbuf_put_string(msg, blob, blen)) != 0 ||
 145                             (r = sshbuf_put_cstring(msg, labels[i])) != 0)
 146                                 fatal_fr(r, "compose key");
 147                         free(blob);
 148                         add_key(keys[i], name, labels[i]);
 149                         free(labels[i]);
 150                 }
 151         } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0 ||
 152             (r = sshbuf_put_u32(msg, -nkeys)) != 0)
 153                 fatal_fr(r, "compose");
 154         free(labels);
 155         free(keys); /* keys themselves are transferred to pkcs11_keylist */
 156         free(pin);
 157         free(name);
 158         send_msg(msg);
 159         sshbuf_free(msg);
 160 }
 161
 162 static void
 163 process_del(void)
 164 {
 165         char *name, *pin;
 166         struct sshbuf *msg;
 167         int r;
 168
 169         if ((msg = sshbuf_new()) == NULL)
 170                 fatal_f("sshbuf_new failed");
 171         if ((r = sshbuf_get_cstring(iqueue, &name, NULL)) != 0 ||
 172             (r = sshbuf_get_cstring(iqueue, &pin, NULL)) != 0)
 173                 fatal_fr(r, "parse");
 174         del_keys_by_name(name);
 175         if ((r = sshbuf_put_u8(msg, pkcs11_del_provider(name) == 0 ?
 176             SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
 177                 fatal_fr(r, "compose");
 178         free(pin);
 179         free(name);
 180         send_msg(msg);
 181         sshbuf_free(msg);
 182 }
 183
 184 static void
 185 process_sign(void)
 186 {
 187         u_char *blob, *data, *signature = NULL;
 188         size_t blen, dlen, slen = 0;
 189         int r, ok = -1;
 190         struct sshkey *key, *found;
 191         struct sshbuf *msg;
 192
 193         /* XXX support SHA2 signature flags */
 194         if ((r = sshbuf_get_string(iqueue, &blob, &blen)) != 0 ||
 195             (r = sshbuf_get_string(iqueue, &data, &dlen)) != 0 ||
 196             (r = sshbuf_get_u32(iqueue, NULL)) != 0)
 197                 fatal_fr(r, "parse");
 198
 199         if ((r = sshkey_from_blob(blob, blen, &key)) != 0)
 200                 fatal_fr(r, "decode key");
 201         else {
 202                 if ((found = lookup_key(key)) != NULL) {
 203 #ifdef WITH_OPENSSL
 204                         int ret;
 205
 206                         if (key->type == KEY_RSA) {
 207                                 slen = RSA_size(key->rsa);
 208                                 signature = xmalloc(slen);
 209                                 ret = RSA_private_encrypt(dlen, data, signature,
 210                                     found->rsa, RSA_PKCS1_PADDING);
 211                                 if (ret != -1) {
 212                                         slen = ret;
 213                                         ok = 0;
 214                                 }
 215 #ifdef OPENSSL_HAS_ECC
 216                         } else if (key->type == KEY_ECDSA) {
 217                                 u_int xslen = ECDSA_size(key->ecdsa);
 218
 219                                 signature = xmalloc(xslen);
 220                                 /* "The parameter type is ignored." */
 221                                 ret = ECDSA_sign(-1, data, dlen, signature,
 222                                     &xslen, found->ecdsa);
 223                                 if (ret != 0)
 224                                         ok = 0;
 225                                 else
 226                                         error_f("ECDSA_sign returned %d", ret);
 227                                 slen = xslen;
 228 #endif /* OPENSSL_HAS_ECC */
 229                         } else
 230                                 error_f("don't know how to sign with key "
 231                                     "type %d", (int)key->type);
 232 #endif /* WITH_OPENSSL */
 233                 }
 234                 sshkey_free(key);
 235         }
 236         if ((msg = sshbuf_new()) == NULL)
 237                 fatal_f("sshbuf_new failed");
 238         if (ok == 0) {
 239                 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
 240                     (r = sshbuf_put_string(msg, signature, slen)) != 0)
 241                         fatal_fr(r, "compose response");
 242         } else {
 243                 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_FAILURE)) != 0)
 244                         fatal_fr(r, "compose failure response");
 245         }
 246         free(data);
 247         free(blob);
 248         free(signature);
 249         send_msg(msg);
 250         sshbuf_free(msg);
 251 }
 252
 253 static void
 254 process(void)
 255 {
 256         u_int msg_len;
 257         u_int buf_len;
 258         u_int consumed;
 259         u_char type;
 260         const u_char *cp;
 261         int r;
 262
 263         buf_len = sshbuf_len(iqueue);
 264         if (buf_len < 5)
 265                 return;         /* Incomplete message. */
 266         cp = sshbuf_ptr(iqueue);
 267         msg_len = get_u32(cp);
 268         if (msg_len > MAX_MSG_LENGTH) {
 269                 error("bad message len %d", msg_len);
 270                 cleanup_exit(11);
 271         }
 272         if (buf_len < msg_len + 4)
 273                 return;
 274         if ((r = sshbuf_consume(iqueue, 4)) != 0 ||
 275             (r = sshbuf_get_u8(iqueue, &type)) != 0)
 276                 fatal_fr(r, "parse type/len");
 277         buf_len -= 4;
 278         switch (type) {
 279         case SSH_AGENTC_ADD_SMARTCARD_KEY:
 280                 debug("process_add");
 281                 process_add();
 282                 break;
 283         case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
 284                 debug("process_del");
 285                 process_del();
 286                 break;
 287         case SSH2_AGENTC_SIGN_REQUEST:
 288                 debug("process_sign");
 289                 process_sign();
 290                 break;
 291         default:
 292                 error("Unknown message %d", type);
 293                 break;
 294         }
 295         /* discard the remaining bytes from the current packet */
 296         if (buf_len < sshbuf_len(iqueue)) {
 297                 error("iqueue grew unexpectedly");
 298                 cleanup_exit(255);
 299         }
 300         consumed = buf_len - sshbuf_len(iqueue);
 301         if (msg_len < consumed) {
 302                 error("msg_len %d < consumed %d", msg_len, consumed);
 303                 cleanup_exit(255);
 304         }
 305         if (msg_len > consumed) {
 306                 if ((r = sshbuf_consume(iqueue, msg_len - consumed)) != 0)
 307                         fatal_fr(r, "consume");
 308         }
 309 }
 310
 311 void
 312 cleanup_exit(int i)
 313 {
 314         /* XXX */
 315         _exit(i);
 316 }
 317
 318
 319 int
 320 main(int argc, char **argv)
 321 {
 322         int r, ch, in, out, log_stderr = 0;
 323         ssize_t len;
 324         SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
 325         LogLevel log_level = SYSLOG_LEVEL_ERROR;
 326         char buf[4*4096];
 327         extern char *__progname;
 328         struct pollfd pfd[2];
 329
 330         __progname = ssh_get_progname(argv[0]);
 331         seed_rng();
 332         TAILQ_INIT(&pkcs11_keylist);
 333
 334         log_init(__progname, log_level, log_facility, log_stderr);
 335
 336         while ((ch = getopt(argc, argv, "v")) != -1) {
 337                 switch (ch) {
 338                 case 'v':
 339                         log_stderr = 1;
 340                         if (log_level == SYSLOG_LEVEL_ERROR)
 341                                 log_level = SYSLOG_LEVEL_DEBUG1;
 342                         else if (log_level < SYSLOG_LEVEL_DEBUG3)
 343                                 log_level++;
 344                         break;
 345                 default:
 346                         fprintf(stderr, "usage: %s [-v]\n", __progname);
 347                         exit(1);
 348                 }
 349         }
 350
 351         log_init(__progname, log_level, log_facility, log_stderr);
 352
 353         pkcs11_init(0);
 354         in = STDIN_FILENO;
 355         out = STDOUT_FILENO;
 356
 357         if ((iqueue = sshbuf_new()) == NULL)
 358                 fatal_f("sshbuf_new failed");
 359         if ((oqueue = sshbuf_new()) == NULL)
 360                 fatal_f("sshbuf_new failed");
 361
 362         while (1) {
 363                 memset(pfd, 0, sizeof(pfd));
 364                 pfd[0].fd = in;
 365                 pfd[1].fd = out;
 366
 367                 /*
 368                  * Ensure that we can read a full buffer and handle
 369                  * the worst-case length packet it can generate,
 370                  * otherwise apply backpressure by stopping reads.
 371                  */
 372                 if ((r = sshbuf_check_reserve(iqueue, sizeof(buf))) == 0 &&
 373                     (r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0)
 374                         pfd[0].events = POLLIN;
 375                 else if (r != SSH_ERR_NO_BUFFER_SPACE)
 376                         fatal_fr(r, "reserve");
 377
 378                 if (sshbuf_len(oqueue) > 0)
 379                         pfd[1].events = POLLOUT;
 380
 381                 if ((r = poll(pfd, 2, -1 /* INFTIM */)) <= 0) {
 382                         if (r == 0 || errno == EINTR)
 383                                 continue;
 384                         fatal("poll: %s", strerror(errno));
 385                 }
 386
 387                 /* copy stdin to iqueue */
 388                 if ((pfd[0].revents & (POLLIN|POLLHUP|POLLERR)) != 0) {
 389                         len = read(in, buf, sizeof buf);
 390                         if (len == 0) {
 391                                 debug("read eof");
 392                                 cleanup_exit(0);
 393                         } else if (len < 0) {
 394                                 error("read: %s", strerror(errno));
 395                                 cleanup_exit(1);
 396                         } else if ((r = sshbuf_put(iqueue, buf, len)) != 0)
 397                                 fatal_fr(r, "sshbuf_put");
 398                 }
 399                 /* send oqueue to stdout */
 400                 if ((pfd[1].revents & (POLLOUT|POLLHUP)) != 0) {
 401                         len = write(out, sshbuf_ptr(oqueue),
 402                             sshbuf_len(oqueue));
 403                         if (len < 0) {
 404                                 error("write: %s", strerror(errno));
 405                                 cleanup_exit(1);
 406                         } else if ((r = sshbuf_consume(oqueue, len)) != 0)
 407                                 fatal_fr(r, "consume");
 408                 }
 409
 410                 /*
 411                  * Process requests from client if we can fit the results
 412                  * into the output buffer, otherwise stop processing input
 413                  * and let the output queue drain.
 414                  */
 415                 if ((r = sshbuf_check_reserve(oqueue, MAX_MSG_LENGTH)) == 0)
 416                         process();
 417                 else if (r != SSH_ERR_NO_BUFFER_SPACE)
 418                         fatal_fr(r, "reserve");
 419         }
 420 }
 421
 422 #else /* WITH_OPENSSL */
 423 void
 424 cleanup_exit(int i)
 425 {
 426         _exit(i);
 427 }
 428
 429 int
 430 main(int argc, char **argv)
 431 {
 432         fprintf(stderr, "PKCS#11 code is not enabled\n");
 433         return 1;
 434 }
 435 #endif /* WITH_OPENSSL */
 436 #else /* ENABLE_PKCS11 */
 437 int
 438 main(int argc, char **argv)
 439 {
 440         extern char *__progname;
 441
 442         __progname = ssh_get_progname(argv[0]);
 443         log_init(__progname, SYSLOG_LEVEL_ERROR, SYSLOG_FACILITY_AUTH, 0);
 444         fatal("PKCS#11 support disabled at compile time");
 445 }
 446 #endif /* ENABLE_PKCS11 */