authfd.c

   1 /* $OpenBSD: authfd.c,v 1.81 2009/08/27 17:44:52 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Functions for connecting the local authentication agent.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 implementation,
  15  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/un.h>
  42 #include <sys/socket.h>
  43
  44 #include <openssl/evp.h>
  45
  46 #include <openssl/crypto.h>
  47 #include <fcntl.h>
  48 #include <stdlib.h>
  49 #include <signal.h>
  50 #include <stdarg.h>
  51 #include <string.h>
  52 #include <unistd.h>
  53
  54 #include "xmalloc.h"
  55 #include "ssh.h"
  56 #include "rsa.h"
  57 #include "buffer.h"
  58 #include "key.h"
  59 #include "authfd.h"
  60 #include "cipher.h"
  61 #include "kex.h"
  62 #include "compat.h"
  63 #include "log.h"
  64 #include "atomicio.h"
  65 #include "misc.h"
  66
  67 static int agent_present = 0;
  68
  69 /* helper */
  70 int     decode_reply(int type);
  71
  72 /* macro to check for "agent failure" message */
  73 #define agent_failed(x) \
  74     ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \
  75     (x == SSH2_AGENT_FAILURE))
  76
  77 int
  78 ssh_agent_present(void)
  79 {
  80         int authfd;
  81
  82         if (agent_present)
  83                 return 1;
  84         if ((authfd = ssh_get_authentication_socket()) == -1)
  85                 return 0;
  86         else {
  87                 ssh_close_authentication_socket(authfd);
  88                 return 1;
  89         }
  90 }
  91
  92 /* Returns the number of the authentication fd, or -1 if there is none. */
  93
  94 int
  95 ssh_get_authentication_socket(void)
  96 {
  97         const char *authsocket;
  98         int sock;
  99         struct sockaddr_un sunaddr;
 100
 101         authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
 102         if (!authsocket)
 103                 return -1;
 104
 105         sunaddr.sun_family = AF_UNIX;
 106         strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
 107
 108         sock = socket(AF_UNIX, SOCK_STREAM, 0);
 109         if (sock < 0)
 110                 return -1;
 111
 112         /* close on exec */
 113         if (fcntl(sock, F_SETFD, 1) == -1) {
 114                 close(sock);
 115                 return -1;
 116         }
 117         if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) {
 118                 close(sock);
 119                 return -1;
 120         }
 121         agent_present = 1;
 122         return sock;
 123 }
 124
 125 static int
 126 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply)
 127 {
 128         u_int l, len;
 129         char buf[1024];
 130
 131         /* Get the length of the message, and format it in the buffer. */
 132         len = buffer_len(request);
 133         put_u32(buf, len);
 134
 135         /* Send the length and then the packet to the agent. */
 136         if (atomicio(vwrite, auth->fd, buf, 4) != 4 ||
 137             atomicio(vwrite, auth->fd, buffer_ptr(request),
 138             buffer_len(request)) != buffer_len(request)) {
 139                 error("Error writing to authentication socket.");
 140                 return 0;
 141         }
 142         /*
 143          * Wait for response from the agent.  First read the length of the
 144          * response packet.
 145          */
 146         if (atomicio(read, auth->fd, buf, 4) != 4) {
 147             error("Error reading response length from authentication socket.");
 148             return 0;
 149         }
 150
 151         /* Extract the length, and check it for sanity. */
 152         len = get_u32(buf);
 153         if (len > 256 * 1024)
 154                 fatal("Authentication response too long: %u", len);
 155
 156         /* Read the rest of the response in to the buffer. */
 157         buffer_clear(reply);
 158         while (len > 0) {
 159                 l = len;
 160                 if (l > sizeof(buf))
 161                         l = sizeof(buf);
 162                 if (atomicio(read, auth->fd, buf, l) != l) {
 163                         error("Error reading response from authentication socket.");
 164                         return 0;
 165                 }
 166                 buffer_append(reply, buf, l);
 167                 len -= l;
 168         }
 169         return 1;
 170 }
 171
 172 /*
 173  * Closes the agent socket if it should be closed (depends on how it was
 174  * obtained).  The argument must have been returned by
 175  * ssh_get_authentication_socket().
 176  */
 177
 178 void
 179 ssh_close_authentication_socket(int sock)
 180 {
 181         if (getenv(SSH_AUTHSOCKET_ENV_NAME))
 182                 close(sock);
 183 }
 184
 185 /*
 186  * Opens and connects a private socket for communication with the
 187  * authentication agent.  Returns the file descriptor (which must be
 188  * shut down and closed by the caller when no longer needed).
 189  * Returns NULL if an error occurred and the connection could not be
 190  * opened.
 191  */
 192
 193 AuthenticationConnection *
 194 ssh_get_authentication_connection(void)
 195 {
 196         AuthenticationConnection *auth;
 197         int sock;
 198
 199         sock = ssh_get_authentication_socket();
 200
 201         /*
 202          * Fail if we couldn't obtain a connection.  This happens if we
 203          * exited due to a timeout.
 204          */
 205         if (sock < 0)
 206                 return NULL;
 207
 208         auth = xmalloc(sizeof(*auth));
 209         auth->fd = sock;
 210         buffer_init(&auth->identities);
 211         auth->howmany = 0;
 212
 213         return auth;
 214 }
 215
 216 /*
 217  * Closes the connection to the authentication agent and frees any associated
 218  * memory.
 219  */
 220
 221 void
 222 ssh_close_authentication_connection(AuthenticationConnection *auth)
 223 {
 224         buffer_free(&auth->identities);
 225         close(auth->fd);
 226         xfree(auth);
 227 }
 228
 229 /* Lock/unlock agent */
 230 int
 231 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password)
 232 {
 233         int type;
 234         Buffer msg;
 235
 236         buffer_init(&msg);
 237         buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK);
 238         buffer_put_cstring(&msg, password);
 239
 240         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 241                 buffer_free(&msg);
 242                 return 0;
 243         }
 244         type = buffer_get_char(&msg);
 245         buffer_free(&msg);
 246         return decode_reply(type);
 247 }
 248
 249 /*
 250  * Returns the first authentication identity held by the agent.
 251  */
 252
 253 int
 254 ssh_get_num_identities(AuthenticationConnection *auth, int version)
 255 {
 256         int type, code1 = 0, code2 = 0;
 257         Buffer request;
 258
 259         switch (version) {
 260         case 1:
 261                 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
 262                 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER;
 263                 break;
 264         case 2:
 265                 code1 = SSH2_AGENTC_REQUEST_IDENTITIES;
 266                 code2 = SSH2_AGENT_IDENTITIES_ANSWER;
 267                 break;
 268         default:
 269                 return 0;
 270         }
 271
 272         /*
 273          * Send a message to the agent requesting for a list of the
 274          * identities it can represent.
 275          */
 276         buffer_init(&request);
 277         buffer_put_char(&request, code1);
 278
 279         buffer_clear(&auth->identities);
 280         if (ssh_request_reply(auth, &request, &auth->identities) == 0) {
 281                 buffer_free(&request);
 282                 return 0;
 283         }
 284         buffer_free(&request);
 285
 286         /* Get message type, and verify that we got a proper answer. */
 287         type = buffer_get_char(&auth->identities);
 288         if (agent_failed(type)) {
 289                 return 0;
 290         } else if (type != code2) {
 291                 fatal("Bad authentication reply message type: %d", type);
 292         }
 293
 294         /* Get the number of entries in the response and check it for sanity. */
 295         auth->howmany = buffer_get_int(&auth->identities);
 296         if ((u_int)auth->howmany > 1024)
 297                 fatal("Too many identities in authentication reply: %d",
 298                     auth->howmany);
 299
 300         return auth->howmany;
 301 }
 302
 303 Key *
 304 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version)
 305 {
 306         /* get number of identities and return the first entry (if any). */
 307         if (ssh_get_num_identities(auth, version) > 0)
 308                 return ssh_get_next_identity(auth, comment, version);
 309         return NULL;
 310 }
 311
 312 Key *
 313 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version)
 314 {
 315         int keybits;
 316         u_int bits;
 317         u_char *blob;
 318         u_int blen;
 319         Key *key = NULL;
 320
 321         /* Return failure if no more entries. */
 322         if (auth->howmany <= 0)
 323                 return NULL;
 324
 325         /*
 326          * Get the next entry from the packet.  These will abort with a fatal
 327          * error if the packet is too short or contains corrupt data.
 328          */
 329         switch (version) {
 330         case 1:
 331                 key = key_new(KEY_RSA1);
 332                 bits = buffer_get_int(&auth->identities);
 333                 buffer_get_bignum(&auth->identities, key->rsa->e);
 334                 buffer_get_bignum(&auth->identities, key->rsa->n);
 335                 *comment = buffer_get_string(&auth->identities, NULL);
 336                 keybits = BN_num_bits(key->rsa->n);
 337                 if (keybits < 0 || bits != (u_int)keybits)
 338                         logit("Warning: identity keysize mismatch: actual %d, announced %u",
 339                             BN_num_bits(key->rsa->n), bits);
 340                 break;
 341         case 2:
 342                 blob = buffer_get_string(&auth->identities, &blen);
 343                 *comment = buffer_get_string(&auth->identities, NULL);
 344                 key = key_from_blob(blob, blen);
 345                 xfree(blob);
 346                 break;
 347         default:
 348                 return NULL;
 349         }
 350         /* Decrement the number of remaining entries. */
 351         auth->howmany--;
 352         return key;
 353 }
 354
 355 /*
 356  * Generates a random challenge, sends it to the agent, and waits for
 357  * response from the agent.  Returns true (non-zero) if the agent gave the
 358  * correct answer, zero otherwise.  Response type selects the style of
 359  * response desired, with 0 corresponding to protocol version 1.0 (no longer
 360  * supported) and 1 corresponding to protocol version 1.1.
 361  */
 362
 363 int
 364 ssh_decrypt_challenge(AuthenticationConnection *auth,
 365     Key* key, BIGNUM *challenge,
 366     u_char session_id[16],
 367     u_int response_type,
 368     u_char response[16])
 369 {
 370         Buffer buffer;
 371         int success = 0;
 372         int i;
 373         int type;
 374
 375         if (key->type != KEY_RSA1)
 376                 return 0;
 377         if (response_type == 0) {
 378                 logit("Compatibility with ssh protocol version 1.0 no longer supported.");
 379                 return 0;
 380         }
 381         buffer_init(&buffer);
 382         buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
 383         buffer_put_int(&buffer, BN_num_bits(key->rsa->n));
 384         buffer_put_bignum(&buffer, key->rsa->e);
 385         buffer_put_bignum(&buffer, key->rsa->n);
 386         buffer_put_bignum(&buffer, challenge);
 387         buffer_append(&buffer, session_id, 16);
 388         buffer_put_int(&buffer, response_type);
 389
 390         if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
 391                 buffer_free(&buffer);
 392                 return 0;
 393         }
 394         type = buffer_get_char(&buffer);
 395
 396         if (agent_failed(type)) {
 397                 logit("Agent admitted failure to authenticate using the key.");
 398         } else if (type != SSH_AGENT_RSA_RESPONSE) {
 399                 fatal("Bad authentication response: %d", type);
 400         } else {
 401                 success = 1;
 402                 /*
 403                  * Get the response from the packet.  This will abort with a
 404                  * fatal error if the packet is corrupt.
 405                  */
 406                 for (i = 0; i < 16; i++)
 407                         response[i] = (u_char)buffer_get_char(&buffer);
 408         }
 409         buffer_free(&buffer);
 410         return success;
 411 }
 412
 413 /* ask agent to sign data, returns -1 on error, 0 on success */
 414 int
 415 ssh_agent_sign(AuthenticationConnection *auth,
 416     Key *key,
 417     u_char **sigp, u_int *lenp,
 418     u_char *data, u_int datalen)
 419 {
 420         extern int datafellows;
 421         Buffer msg;
 422         u_char *blob;
 423         u_int blen;
 424         int type, flags = 0;
 425         int ret = -1;
 426
 427         if (key_to_blob(key, &blob, &blen) == 0)
 428                 return -1;
 429
 430         if (datafellows & SSH_BUG_SIGBLOB)
 431                 flags = SSH_AGENT_OLD_SIGNATURE;
 432
 433         buffer_init(&msg);
 434         buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
 435         buffer_put_string(&msg, blob, blen);
 436         buffer_put_string(&msg, data, datalen);
 437         buffer_put_int(&msg, flags);
 438         xfree(blob);
 439
 440         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 441                 buffer_free(&msg);
 442                 return -1;
 443         }
 444         type = buffer_get_char(&msg);
 445         if (agent_failed(type)) {
 446                 logit("Agent admitted failure to sign using the key.");
 447         } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
 448                 fatal("Bad authentication response: %d", type);
 449         } else {
 450                 ret = 0;
 451                 *sigp = buffer_get_string(&msg, lenp);
 452         }
 453         buffer_free(&msg);
 454         return ret;
 455 }
 456
 457 /* Encode key for a message to the agent. */
 458
 459 static void
 460 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment)
 461 {
 462         buffer_put_int(b, BN_num_bits(key->n));
 463         buffer_put_bignum(b, key->n);
 464         buffer_put_bignum(b, key->e);
 465         buffer_put_bignum(b, key->d);
 466         /* To keep within the protocol: p < q for ssh. in SSL p > q */
 467         buffer_put_bignum(b, key->iqmp);        /* ssh key->u */
 468         buffer_put_bignum(b, key->q);   /* ssh key->p, SSL key->q */
 469         buffer_put_bignum(b, key->p);   /* ssh key->q, SSL key->p */
 470         buffer_put_cstring(b, comment);
 471 }
 472
 473 static void
 474 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment)
 475 {
 476         buffer_put_cstring(b, key_ssh_name(key));
 477         switch (key->type) {
 478         case KEY_RSA:
 479                 buffer_put_bignum2(b, key->rsa->n);
 480                 buffer_put_bignum2(b, key->rsa->e);
 481                 buffer_put_bignum2(b, key->rsa->d);
 482                 buffer_put_bignum2(b, key->rsa->iqmp);
 483                 buffer_put_bignum2(b, key->rsa->p);
 484                 buffer_put_bignum2(b, key->rsa->q);
 485                 break;
 486         case KEY_DSA:
 487                 buffer_put_bignum2(b, key->dsa->p);
 488                 buffer_put_bignum2(b, key->dsa->q);
 489                 buffer_put_bignum2(b, key->dsa->g);
 490                 buffer_put_bignum2(b, key->dsa->pub_key);
 491                 buffer_put_bignum2(b, key->dsa->priv_key);
 492                 break;
 493         }
 494         buffer_put_cstring(b, comment);
 495 }
 496
 497 /*
 498  * Adds an identity to the authentication server.  This call is not meant to
 499  * be used by normal applications.
 500  */
 501
 502 int
 503 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key,
 504     const char *comment, u_int life, u_int confirm)
 505 {
 506         Buffer msg;
 507         int type, constrained = (life || confirm);
 508
 509         buffer_init(&msg);
 510
 511         switch (key->type) {
 512         case KEY_RSA1:
 513                 type = constrained ?
 514                     SSH_AGENTC_ADD_RSA_ID_CONSTRAINED :
 515                     SSH_AGENTC_ADD_RSA_IDENTITY;
 516                 buffer_put_char(&msg, type);
 517                 ssh_encode_identity_rsa1(&msg, key->rsa, comment);
 518                 break;
 519         case KEY_RSA:
 520         case KEY_DSA:
 521                 type = constrained ?
 522                     SSH2_AGENTC_ADD_ID_CONSTRAINED :
 523                     SSH2_AGENTC_ADD_IDENTITY;
 524                 buffer_put_char(&msg, type);
 525                 ssh_encode_identity_ssh2(&msg, key, comment);
 526                 break;
 527         default:
 528                 buffer_free(&msg);
 529                 return 0;
 530         }
 531         if (constrained) {
 532                 if (life != 0) {
 533                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
 534                         buffer_put_int(&msg, life);
 535                 }
 536                 if (confirm != 0)
 537                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
 538         }
 539         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 540                 buffer_free(&msg);
 541                 return 0;
 542         }
 543         type = buffer_get_char(&msg);
 544         buffer_free(&msg);
 545         return decode_reply(type);
 546 }
 547
 548 /*
 549  * Removes an identity from the authentication server.  This call is not
 550  * meant to be used by normal applications.
 551  */
 552
 553 int
 554 ssh_remove_identity(AuthenticationConnection *auth, Key *key)
 555 {
 556         Buffer msg;
 557         int type;
 558         u_char *blob;
 559         u_int blen;
 560
 561         buffer_init(&msg);
 562
 563         if (key->type == KEY_RSA1) {
 564                 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY);
 565                 buffer_put_int(&msg, BN_num_bits(key->rsa->n));
 566                 buffer_put_bignum(&msg, key->rsa->e);
 567                 buffer_put_bignum(&msg, key->rsa->n);
 568         } else if (key->type == KEY_DSA || key->type == KEY_RSA) {
 569                 key_to_blob(key, &blob, &blen);
 570                 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY);
 571                 buffer_put_string(&msg, blob, blen);
 572                 xfree(blob);
 573         } else {
 574                 buffer_free(&msg);
 575                 return 0;
 576         }
 577         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 578                 buffer_free(&msg);
 579                 return 0;
 580         }
 581         type = buffer_get_char(&msg);
 582         buffer_free(&msg);
 583         return decode_reply(type);
 584 }
 585
 586 int
 587 ssh_update_card(AuthenticationConnection *auth, int add,
 588     const char *reader_id, const char *pin, u_int life, u_int confirm)
 589 {
 590         Buffer msg;
 591         int type, constrained = (life || confirm);
 592
 593         if (add) {
 594                 type = constrained ?
 595                     SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
 596                     SSH_AGENTC_ADD_SMARTCARD_KEY;
 597         } else
 598                 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;
 599
 600         buffer_init(&msg);
 601         buffer_put_char(&msg, type);
 602         buffer_put_cstring(&msg, reader_id);
 603         buffer_put_cstring(&msg, pin);
 604
 605         if (constrained) {
 606                 if (life != 0) {
 607                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
 608                         buffer_put_int(&msg, life);
 609                 }
 610                 if (confirm != 0)
 611                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
 612         }
 613
 614         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 615                 buffer_free(&msg);
 616                 return 0;
 617         }
 618         type = buffer_get_char(&msg);
 619         buffer_free(&msg);
 620         return decode_reply(type);
 621 }
 622
 623 /*
 624  * Removes all identities from the agent.  This call is not meant to be used
 625  * by normal applications.
 626  */
 627
 628 int
 629 ssh_remove_all_identities(AuthenticationConnection *auth, int version)
 630 {
 631         Buffer msg;
 632         int type;
 633         int code = (version==1) ?
 634                 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
 635                 SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
 636
 637         buffer_init(&msg);
 638         buffer_put_char(&msg, code);
 639
 640         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 641                 buffer_free(&msg);
 642                 return 0;
 643         }
 644         type = buffer_get_char(&msg);
 645         buffer_free(&msg);
 646         return decode_reply(type);
 647 }
 648
 649 int
 650 decode_reply(int type)
 651 {
 652         switch (type) {
 653         case SSH_AGENT_FAILURE:
 654         case SSH_COM_AGENT2_FAILURE:
 655         case SSH2_AGENT_FAILURE:
 656                 logit("SSH_AGENT_FAILURE");
 657                 return 0;
 658         case SSH_AGENT_SUCCESS:
 659                 return 1;
 660         default:
 661                 fatal("Bad response from authentication agent: %d", type);
 662         }
 663         /* NOTREACHED */
 664         return 0;
 665 }