crypto/openssh/authfd.c

   1 /* $OpenBSD: authfd.c,v 1.93 2014/04/29 18:01:49 markus 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 <fcntl.h>
  45 #include <stdlib.h>
  46 #include <signal.h>
  47 #include <stdarg.h>
  48 #include <string.h>
  49 #include <unistd.h>
  50
  51 #include "xmalloc.h"
  52 #include "ssh.h"
  53 #include "rsa.h"
  54 #include "buffer.h"
  55 #include "key.h"
  56 #include "authfd.h"
  57 #include "cipher.h"
  58 #include "kex.h"
  59 #include "compat.h"
  60 #include "log.h"
  61 #include "atomicio.h"
  62 #include "misc.h"
  63
  64 static int agent_present = 0;
  65
  66 /* helper */
  67 int     decode_reply(int type);
  68
  69 /* macro to check for "agent failure" message */
  70 #define agent_failed(x) \
  71     ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \
  72     (x == SSH2_AGENT_FAILURE))
  73
  74 int
  75 ssh_agent_present(void)
  76 {
  77         int authfd;
  78
  79         if (agent_present)
  80                 return 1;
  81         if ((authfd = ssh_get_authentication_socket()) == -1)
  82                 return 0;
  83         else {
  84                 ssh_close_authentication_socket(authfd);
  85                 return 1;
  86         }
  87 }
  88
  89 /* Returns the number of the authentication fd, or -1 if there is none. */
  90
  91 int
  92 ssh_get_authentication_socket(void)
  93 {
  94         const char *authsocket;
  95         int sock;
  96         struct sockaddr_un sunaddr;
  97
  98         authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
  99         if (!authsocket)
 100                 return -1;
 101
 102         memset(&sunaddr, 0, sizeof(sunaddr));
 103         sunaddr.sun_family = AF_UNIX;
 104         strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
 105
 106         sock = socket(AF_UNIX, SOCK_STREAM, 0);
 107         if (sock < 0)
 108                 return -1;
 109
 110         /* close on exec */
 111         if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1) {
 112                 close(sock);
 113                 return -1;
 114         }
 115         if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) {
 116                 close(sock);
 117                 return -1;
 118         }
 119         agent_present = 1;
 120         return sock;
 121 }
 122
 123 static int
 124 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply)
 125 {
 126         u_int l, len;
 127         char buf[1024];
 128
 129         /* Get the length of the message, and format it in the buffer. */
 130         len = buffer_len(request);
 131         put_u32(buf, len);
 132
 133         /* Send the length and then the packet to the agent. */
 134         if (atomicio(vwrite, auth->fd, buf, 4) != 4 ||
 135             atomicio(vwrite, auth->fd, buffer_ptr(request),
 136             buffer_len(request)) != buffer_len(request)) {
 137                 error("Error writing to authentication socket.");
 138                 return 0;
 139         }
 140         /*
 141          * Wait for response from the agent.  First read the length of the
 142          * response packet.
 143          */
 144         if (atomicio(read, auth->fd, buf, 4) != 4) {
 145             error("Error reading response length from authentication socket.");
 146             return 0;
 147         }
 148
 149         /* Extract the length, and check it for sanity. */
 150         len = get_u32(buf);
 151         if (len > 256 * 1024)
 152                 fatal("Authentication response too long: %u", len);
 153
 154         /* Read the rest of the response in to the buffer. */
 155         buffer_clear(reply);
 156         while (len > 0) {
 157                 l = len;
 158                 if (l > sizeof(buf))
 159                         l = sizeof(buf);
 160                 if (atomicio(read, auth->fd, buf, l) != l) {
 161                         error("Error reading response from authentication socket.");
 162                         return 0;
 163                 }
 164                 buffer_append(reply, buf, l);
 165                 len -= l;
 166         }
 167         return 1;
 168 }
 169
 170 /*
 171  * Closes the agent socket if it should be closed (depends on how it was
 172  * obtained).  The argument must have been returned by
 173  * ssh_get_authentication_socket().
 174  */
 175
 176 void
 177 ssh_close_authentication_socket(int sock)
 178 {
 179         if (getenv(SSH_AUTHSOCKET_ENV_NAME))
 180                 close(sock);
 181 }
 182
 183 /*
 184  * Opens and connects a private socket for communication with the
 185  * authentication agent.  Returns the file descriptor (which must be
 186  * shut down and closed by the caller when no longer needed).
 187  * Returns NULL if an error occurred and the connection could not be
 188  * opened.
 189  */
 190
 191 AuthenticationConnection *
 192 ssh_get_authentication_connection(void)
 193 {
 194         AuthenticationConnection *auth;
 195         int sock;
 196
 197         sock = ssh_get_authentication_socket();
 198
 199         /*
 200          * Fail if we couldn't obtain a connection.  This happens if we
 201          * exited due to a timeout.
 202          */
 203         if (sock < 0)
 204                 return NULL;
 205
 206         auth = xcalloc(1, sizeof(*auth));
 207         auth->fd = sock;
 208         buffer_init(&auth->identities);
 209         auth->howmany = 0;
 210
 211         return auth;
 212 }
 213
 214 /*
 215  * Closes the connection to the authentication agent and frees any associated
 216  * memory.
 217  */
 218
 219 void
 220 ssh_close_authentication_connection(AuthenticationConnection *auth)
 221 {
 222         buffer_free(&auth->identities);
 223         close(auth->fd);
 224         free(auth);
 225 }
 226
 227 /* Lock/unlock agent */
 228 int
 229 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password)
 230 {
 231         int type;
 232         Buffer msg;
 233
 234         buffer_init(&msg);
 235         buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK);
 236         buffer_put_cstring(&msg, password);
 237
 238         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 239                 buffer_free(&msg);
 240                 return 0;
 241         }
 242         type = buffer_get_char(&msg);
 243         buffer_free(&msg);
 244         return decode_reply(type);
 245 }
 246
 247 /*
 248  * Returns the first authentication identity held by the agent.
 249  */
 250
 251 int
 252 ssh_get_num_identities(AuthenticationConnection *auth, int version)
 253 {
 254         int type, code1 = 0, code2 = 0;
 255         Buffer request;
 256
 257         switch (version) {
 258         case 1:
 259                 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
 260                 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER;
 261                 break;
 262         case 2:
 263                 code1 = SSH2_AGENTC_REQUEST_IDENTITIES;
 264                 code2 = SSH2_AGENT_IDENTITIES_ANSWER;
 265                 break;
 266         default:
 267                 return 0;
 268         }
 269
 270         /*
 271          * Send a message to the agent requesting for a list of the
 272          * identities it can represent.
 273          */
 274         buffer_init(&request);
 275         buffer_put_char(&request, code1);
 276
 277         buffer_clear(&auth->identities);
 278         if (ssh_request_reply(auth, &request, &auth->identities) == 0) {
 279                 buffer_free(&request);
 280                 return 0;
 281         }
 282         buffer_free(&request);
 283
 284         /* Get message type, and verify that we got a proper answer. */
 285         type = buffer_get_char(&auth->identities);
 286         if (agent_failed(type)) {
 287                 return 0;
 288         } else if (type != code2) {
 289                 fatal("Bad authentication reply message type: %d", type);
 290         }
 291
 292         /* Get the number of entries in the response and check it for sanity. */
 293         auth->howmany = buffer_get_int(&auth->identities);
 294         if ((u_int)auth->howmany > 1024)
 295                 fatal("Too many identities in authentication reply: %d",
 296                     auth->howmany);
 297
 298         return auth->howmany;
 299 }
 300
 301 Key *
 302 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version)
 303 {
 304         /* get number of identities and return the first entry (if any). */
 305         if (ssh_get_num_identities(auth, version) > 0)
 306                 return ssh_get_next_identity(auth, comment, version);
 307         return NULL;
 308 }
 309
 310 Key *
 311 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version)
 312 {
 313 #ifdef WITH_SSH1
 314         int keybits;
 315         u_int bits;
 316 #endif
 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 #ifdef WITH_SSH1
 331         case 1:
 332                 key = key_new(KEY_RSA1);
 333                 bits = buffer_get_int(&auth->identities);
 334                 buffer_get_bignum(&auth->identities, key->rsa->e);
 335                 buffer_get_bignum(&auth->identities, key->rsa->n);
 336                 *comment = buffer_get_string(&auth->identities, NULL);
 337                 keybits = BN_num_bits(key->rsa->n);
 338                 if (keybits < 0 || bits != (u_int)keybits)
 339                         logit("Warning: identity keysize mismatch: actual %d, announced %u",
 340                             BN_num_bits(key->rsa->n), bits);
 341                 break;
 342 #endif
 343         case 2:
 344                 blob = buffer_get_string(&auth->identities, &blen);
 345                 *comment = buffer_get_string(&auth->identities, NULL);
 346                 key = key_from_blob(blob, blen);
 347                 free(blob);
 348                 break;
 349         default:
 350                 return NULL;
 351         }
 352         /* Decrement the number of remaining entries. */
 353         auth->howmany--;
 354         return key;
 355 }
 356
 357 /*
 358  * Generates a random challenge, sends it to the agent, and waits for
 359  * response from the agent.  Returns true (non-zero) if the agent gave the
 360  * correct answer, zero otherwise.  Response type selects the style of
 361  * response desired, with 0 corresponding to protocol version 1.0 (no longer
 362  * supported) and 1 corresponding to protocol version 1.1.
 363  */
 364
 365 #ifdef WITH_SSH1
 366 int
 367 ssh_decrypt_challenge(AuthenticationConnection *auth,
 368     Key* key, BIGNUM *challenge,
 369     u_char session_id[16],
 370     u_int response_type,
 371     u_char response[16])
 372 {
 373         Buffer buffer;
 374         int success = 0;
 375         int i;
 376         int type;
 377
 378         if (key->type != KEY_RSA1)
 379                 return 0;
 380         if (response_type == 0) {
 381                 logit("Compatibility with ssh protocol version 1.0 no longer supported.");
 382                 return 0;
 383         }
 384         buffer_init(&buffer);
 385         buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
 386         buffer_put_int(&buffer, BN_num_bits(key->rsa->n));
 387         buffer_put_bignum(&buffer, key->rsa->e);
 388         buffer_put_bignum(&buffer, key->rsa->n);
 389         buffer_put_bignum(&buffer, challenge);
 390         buffer_append(&buffer, session_id, 16);
 391         buffer_put_int(&buffer, response_type);
 392
 393         if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
 394                 buffer_free(&buffer);
 395                 return 0;
 396         }
 397         type = buffer_get_char(&buffer);
 398
 399         if (agent_failed(type)) {
 400                 logit("Agent admitted failure to authenticate using the key.");
 401         } else if (type != SSH_AGENT_RSA_RESPONSE) {
 402                 fatal("Bad authentication response: %d", type);
 403         } else {
 404                 success = 1;
 405                 /*
 406                  * Get the response from the packet.  This will abort with a
 407                  * fatal error if the packet is corrupt.
 408                  */
 409                 for (i = 0; i < 16; i++)
 410                         response[i] = (u_char)buffer_get_char(&buffer);
 411         }
 412         buffer_free(&buffer);
 413         return success;
 414 }
 415 #endif
 416
 417 /* ask agent to sign data, returns -1 on error, 0 on success */
 418 int
 419 ssh_agent_sign(AuthenticationConnection *auth,
 420     Key *key,
 421     u_char **sigp, u_int *lenp,
 422     u_char *data, u_int datalen)
 423 {
 424         extern int datafellows;
 425         Buffer msg;
 426         u_char *blob;
 427         u_int blen;
 428         int type, flags = 0;
 429         int ret = -1;
 430
 431         if (key_to_blob(key, &blob, &blen) == 0)
 432                 return -1;
 433
 434         if (datafellows & SSH_BUG_SIGBLOB)
 435                 flags = SSH_AGENT_OLD_SIGNATURE;
 436
 437         buffer_init(&msg);
 438         buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
 439         buffer_put_string(&msg, blob, blen);
 440         buffer_put_string(&msg, data, datalen);
 441         buffer_put_int(&msg, flags);
 442         free(blob);
 443
 444         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 445                 buffer_free(&msg);
 446                 return -1;
 447         }
 448         type = buffer_get_char(&msg);
 449         if (agent_failed(type)) {
 450                 logit("Agent admitted failure to sign using the key.");
 451         } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
 452                 fatal("Bad authentication response: %d", type);
 453         } else {
 454                 ret = 0;
 455                 *sigp = buffer_get_string(&msg, lenp);
 456         }
 457         buffer_free(&msg);
 458         return ret;
 459 }
 460
 461 /* Encode key for a message to the agent. */
 462
 463 #ifdef WITH_SSH1
 464 static void
 465 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment)
 466 {
 467         buffer_put_int(b, BN_num_bits(key->n));
 468         buffer_put_bignum(b, key->n);
 469         buffer_put_bignum(b, key->e);
 470         buffer_put_bignum(b, key->d);
 471         /* To keep within the protocol: p < q for ssh. in SSL p > q */
 472         buffer_put_bignum(b, key->iqmp);        /* ssh key->u */
 473         buffer_put_bignum(b, key->q);   /* ssh key->p, SSL key->q */
 474         buffer_put_bignum(b, key->p);   /* ssh key->q, SSL key->p */
 475         buffer_put_cstring(b, comment);
 476 }
 477 #endif
 478
 479 static void
 480 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment)
 481 {
 482         key_private_serialize(key, b);
 483         buffer_put_cstring(b, comment);
 484 }
 485
 486 /*
 487  * Adds an identity to the authentication server.  This call is not meant to
 488  * be used by normal applications.
 489  */
 490
 491 int
 492 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key,
 493     const char *comment, u_int life, u_int confirm)
 494 {
 495         Buffer msg;
 496         int type, constrained = (life || confirm);
 497
 498         buffer_init(&msg);
 499
 500         switch (key->type) {
 501 #ifdef WITH_SSH1
 502         case KEY_RSA1:
 503                 type = constrained ?
 504                     SSH_AGENTC_ADD_RSA_ID_CONSTRAINED :
 505                     SSH_AGENTC_ADD_RSA_IDENTITY;
 506                 buffer_put_char(&msg, type);
 507                 ssh_encode_identity_rsa1(&msg, key->rsa, comment);
 508                 break;
 509 #endif
 510 #ifdef WITH_OPENSSL
 511         case KEY_RSA:
 512         case KEY_RSA_CERT:
 513         case KEY_RSA_CERT_V00:
 514         case KEY_DSA:
 515         case KEY_DSA_CERT:
 516         case KEY_DSA_CERT_V00:
 517         case KEY_ECDSA:
 518         case KEY_ECDSA_CERT:
 519 #endif
 520         case KEY_ED25519:
 521         case KEY_ED25519_CERT:
 522                 type = constrained ?
 523                     SSH2_AGENTC_ADD_ID_CONSTRAINED :
 524                     SSH2_AGENTC_ADD_IDENTITY;
 525                 buffer_put_char(&msg, type);
 526                 ssh_encode_identity_ssh2(&msg, key, comment);
 527                 break;
 528         default:
 529                 buffer_free(&msg);
 530                 return 0;
 531         }
 532         if (constrained) {
 533                 if (life != 0) {
 534                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
 535                         buffer_put_int(&msg, life);
 536                 }
 537                 if (confirm != 0)
 538                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
 539         }
 540         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 541                 buffer_free(&msg);
 542                 return 0;
 543         }
 544         type = buffer_get_char(&msg);
 545         buffer_free(&msg);
 546         return decode_reply(type);
 547 }
 548
 549 /*
 550  * Removes an identity from the authentication server.  This call is not
 551  * meant to be used by normal applications.
 552  */
 553
 554 int
 555 ssh_remove_identity(AuthenticationConnection *auth, Key *key)
 556 {
 557         Buffer msg;
 558         int type;
 559         u_char *blob;
 560         u_int blen;
 561
 562         buffer_init(&msg);
 563
 564 #ifdef WITH_SSH1
 565         if (key->type == KEY_RSA1) {
 566                 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY);
 567                 buffer_put_int(&msg, BN_num_bits(key->rsa->n));
 568                 buffer_put_bignum(&msg, key->rsa->e);
 569                 buffer_put_bignum(&msg, key->rsa->n);
 570         } else
 571 #endif
 572         if (key->type != KEY_UNSPEC) {
 573                 key_to_blob(key, &blob, &blen);
 574                 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY);
 575                 buffer_put_string(&msg, blob, blen);
 576                 free(blob);
 577         } else {
 578                 buffer_free(&msg);
 579                 return 0;
 580         }
 581         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 582                 buffer_free(&msg);
 583                 return 0;
 584         }
 585         type = buffer_get_char(&msg);
 586         buffer_free(&msg);
 587         return decode_reply(type);
 588 }
 589
 590 int
 591 ssh_update_card(AuthenticationConnection *auth, int add,
 592     const char *reader_id, const char *pin, u_int life, u_int confirm)
 593 {
 594         Buffer msg;
 595         int type, constrained = (life || confirm);
 596
 597         if (add) {
 598                 type = constrained ?
 599                     SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
 600                     SSH_AGENTC_ADD_SMARTCARD_KEY;
 601         } else
 602                 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;
 603
 604         buffer_init(&msg);
 605         buffer_put_char(&msg, type);
 606         buffer_put_cstring(&msg, reader_id);
 607         buffer_put_cstring(&msg, pin);
 608
 609         if (constrained) {
 610                 if (life != 0) {
 611                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
 612                         buffer_put_int(&msg, life);
 613                 }
 614                 if (confirm != 0)
 615                         buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
 616         }
 617
 618         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 619                 buffer_free(&msg);
 620                 return 0;
 621         }
 622         type = buffer_get_char(&msg);
 623         buffer_free(&msg);
 624         return decode_reply(type);
 625 }
 626
 627 /*
 628  * Removes all identities from the agent.  This call is not meant to be used
 629  * by normal applications.
 630  */
 631
 632 int
 633 ssh_remove_all_identities(AuthenticationConnection *auth, int version)
 634 {
 635         Buffer msg;
 636         int type;
 637         int code = (version==1) ?
 638                 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
 639                 SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
 640
 641         buffer_init(&msg);
 642         buffer_put_char(&msg, code);
 643
 644         if (ssh_request_reply(auth, &msg, &msg) == 0) {
 645                 buffer_free(&msg);
 646                 return 0;
 647         }
 648         type = buffer_get_char(&msg);
 649         buffer_free(&msg);
 650         return decode_reply(type);
 651 }
 652
 653 int
 654 decode_reply(int type)
 655 {
 656         switch (type) {
 657         case SSH_AGENT_FAILURE:
 658         case SSH_COM_AGENT2_FAILURE:
 659         case SSH2_AGENT_FAILURE:
 660                 logit("SSH_AGENT_FAILURE");
 661                 return 0;
 662         case SSH_AGENT_SUCCESS:
 663                 return 1;
 664         default:
 665                 fatal("Bad response from authentication agent: %d", type);
 666         }
 667         /* NOTREACHED */
 668         return 0;
 669 }