Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.24
1.1 deraadt 1: /*
2:
3: sshconnect.c
4:
5: Author: Tatu Ylonen <ylo@cs.hut.fi>
6:
7: Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8: All rights reserved
9:
10: Created: Sat Mar 18 22:15:47 1995 ylo
11:
12: Code to connect to a remote host, and to perform the client side of the
13: login (authentication) dialog.
14:
15: */
16:
17: #include "includes.h"
1.24 ! deraadt 18: RCSID("$Id: sshconnect.c,v 1.23 1999/10/25 20:34:30 markus Exp $");
1.1 deraadt 19:
1.3 provos 20: #include <ssl/bn.h>
1.1 deraadt 21: #include "xmalloc.h"
22: #include "rsa.h"
23: #include "ssh.h"
24: #include "packet.h"
25: #include "authfd.h"
26: #include "cipher.h"
27: #include "mpaux.h"
28: #include "uidswap.h"
1.21 markus 29: #include "compat.h"
1.1 deraadt 30:
1.24 ! deraadt 31: #include <ssl/md5.h>
1.10 deraadt 32:
1.1 deraadt 33: /* Session id for the current session. */
34: unsigned char session_id[16];
35:
36: /* Connect to the given ssh server using a proxy command. */
37:
1.3 provos 38: int
39: ssh_proxy_connect(const char *host, int port, uid_t original_real_uid,
40: const char *proxy_command)
1.1 deraadt 41: {
42: Buffer command;
43: const char *cp;
44: char *command_string;
45: int pin[2], pout[2];
46: int pid;
47: char portstring[100];
48:
49: /* Convert the port number into a string. */
1.6 deraadt 50: snprintf(portstring, sizeof portstring, "%d", port);
1.1 deraadt 51:
52: /* Build the final command string in the buffer by making the appropriate
53: substitutions to the given proxy command. */
54: buffer_init(&command);
55: for (cp = proxy_command; *cp; cp++)
56: {
57: if (cp[0] == '%' && cp[1] == '%')
58: {
59: buffer_append(&command, "%", 1);
60: cp++;
61: continue;
62: }
63: if (cp[0] == '%' && cp[1] == 'h')
64: {
65: buffer_append(&command, host, strlen(host));
66: cp++;
67: continue;
68: }
69: if (cp[0] == '%' && cp[1] == 'p')
70: {
71: buffer_append(&command, portstring, strlen(portstring));
72: cp++;
73: continue;
74: }
75: buffer_append(&command, cp, 1);
76: }
77: buffer_append(&command, "\0", 1);
78:
79: /* Get the final command string. */
80: command_string = buffer_ptr(&command);
81:
82: /* Create pipes for communicating with the proxy. */
83: if (pipe(pin) < 0 || pipe(pout) < 0)
84: fatal("Could not create pipes to communicate with the proxy: %.100s",
85: strerror(errno));
86:
87: debug("Executing proxy command: %.500s", command_string);
88:
89: /* Fork and execute the proxy command. */
90: if ((pid = fork()) == 0)
91: {
92: char *argv[10];
93:
94: /* Child. Permanently give up superuser privileges. */
95: permanently_set_uid(original_real_uid);
96:
97: /* Redirect stdin and stdout. */
98: close(pin[1]);
99: if (pin[0] != 0)
100: {
101: if (dup2(pin[0], 0) < 0)
102: perror("dup2 stdin");
103: close(pin[0]);
104: }
105: close(pout[0]);
106: if (dup2(pout[1], 1) < 0)
107: perror("dup2 stdout");
108: close(pout[1]); /* Cannot be 1 because pin allocated two descriptors. */
109:
110: /* Stderr is left as it is so that error messages get printed on
111: the user's terminal. */
112: argv[0] = "/bin/sh";
113: argv[1] = "-c";
114: argv[2] = command_string;
115: argv[3] = NULL;
116:
117: /* Execute the proxy command. Note that we gave up any extra
118: privileges above. */
119: execv("/bin/sh", argv);
120: perror("/bin/sh");
121: exit(1);
122: }
123: /* Parent. */
124: if (pid < 0)
125: fatal("fork failed: %.100s", strerror(errno));
126:
127: /* Close child side of the descriptors. */
128: close(pin[0]);
129: close(pout[1]);
130:
131: /* Free the command name. */
132: buffer_free(&command);
133:
134: /* Set the connection file descriptors. */
1.3 provos 135: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 136:
137: return 1;
138: }
139:
140: /* Creates a (possibly privileged) socket for use as the ssh connection. */
141:
142: int ssh_create_socket(uid_t original_real_uid, int privileged)
143: {
144: int sock;
145:
146: /* If we are running as root and want to connect to a privileged port,
147: bind our own socket to a privileged port. */
148: if (privileged)
149: {
1.2 deraadt 150: int p = IPPORT_RESERVED - 1;
151:
152: sock = rresvport(&p);
153: if (sock < 0)
154: fatal("rresvport: %.100s", strerror(errno));
1.1 deraadt 155: debug("Allocated local port %d.", p);
156: }
157: else
158: {
159: /* Just create an ordinary socket on arbitrary port. We use the
160: user's uid to create the socket. */
161: temporarily_use_uid(original_real_uid);
162: sock = socket(AF_INET, SOCK_STREAM, 0);
163: if (sock < 0)
164: fatal("socket: %.100s", strerror(errno));
165: restore_uid();
166: }
167: return sock;
168: }
169:
170: /* Opens a TCP/IP connection to the remote server on the given host. If
171: port is 0, the default port will be used. If anonymous is zero,
172: a privileged port will be allocated to make the connection.
173: This requires super-user privileges if anonymous is false.
174: Connection_attempts specifies the maximum number of tries (one per
175: second). If proxy_command is non-NULL, it specifies the command (with %h
176: and %p substituted for host and port, respectively) to use to contact
177: the daemon. */
178:
1.12 provos 179: int ssh_connect(const char *host, struct sockaddr_in *hostaddr,
180: int port, int connection_attempts,
1.1 deraadt 181: int anonymous, uid_t original_real_uid,
1.3 provos 182: const char *proxy_command)
1.1 deraadt 183: {
184: int sock = -1, attempt, i;
185: int on = 1;
186: struct servent *sp;
187: struct hostent *hp;
188: struct linger linger;
189:
190: debug("ssh_connect: getuid %d geteuid %d anon %d",
191: (int)getuid(), (int)geteuid(), anonymous);
192:
193: /* Get default port if port has not been set. */
194: if (port == 0)
195: {
196: sp = getservbyname(SSH_SERVICE_NAME, "tcp");
197: if (sp)
198: port = ntohs(sp->s_port);
199: else
200: port = SSH_DEFAULT_PORT;
201: }
202:
203: /* If a proxy command is given, connect using it. */
204: if (proxy_command != NULL)
1.3 provos 205: return ssh_proxy_connect(host, port, original_real_uid, proxy_command);
1.1 deraadt 206:
207: /* No proxy command. */
208:
209: /* No host lookup made yet. */
210: hp = NULL;
211:
212: /* Try to connect several times. On some machines, the first time will
213: sometimes fail. In general socket code appears to behave quite
214: magically on many machines. */
215: for (attempt = 0; attempt < connection_attempts; attempt++)
216: {
217: if (attempt > 0)
218: debug("Trying again...");
219:
220: /* Try to parse the host name as a numeric inet address. */
1.12 provos 221: memset(hostaddr, 0, sizeof(hostaddr));
222: hostaddr->sin_family = AF_INET;
223: hostaddr->sin_port = htons(port);
224: hostaddr->sin_addr.s_addr = inet_addr(host);
225: if ((hostaddr->sin_addr.s_addr & 0xffffffff) != 0xffffffff)
1.1 deraadt 226: {
227: /* Valid numeric IP address */
228: debug("Connecting to %.100s port %d.",
1.12 provos 229: inet_ntoa(hostaddr->sin_addr), port);
1.1 deraadt 230:
231: /* Create a socket. */
232: sock = ssh_create_socket(original_real_uid,
233: !anonymous && geteuid() == 0 &&
1.9 deraadt 234: port < IPPORT_RESERVED);
1.1 deraadt 235:
236: /* Connect to the host. We use the user's uid in the hope that
237: it will help with the problems of tcp_wrappers showing the
238: remote uid as root. */
239: temporarily_use_uid(original_real_uid);
1.12 provos 240: if (connect(sock, (struct sockaddr *)hostaddr, sizeof(*hostaddr))
1.1 deraadt 241: >= 0)
242: {
243: /* Successful connect. */
244: restore_uid();
245: break;
246: }
247: debug("connect: %.100s", strerror(errno));
248: restore_uid();
249:
250: /* Destroy the failed socket. */
1.11 deraadt 251: shutdown(sock, SHUT_RDWR);
1.1 deraadt 252: close(sock);
253: }
254: else
255: {
256: /* Not a valid numeric inet address. */
257: /* Map host name to an address. */
258: if (!hp)
259: hp = gethostbyname(host);
260: if (!hp)
261: fatal("Bad host name: %.100s", host);
262: if (!hp->h_addr_list[0])
263: fatal("Host does not have an IP address: %.100s", host);
264:
265: /* Loop through addresses for this host, and try each one in
266: sequence until the connection succeeds. */
267: for (i = 0; hp->h_addr_list[i]; i++)
268: {
269: /* Set the address to connect to. */
1.12 provos 270: hostaddr->sin_family = hp->h_addrtype;
271: memcpy(&hostaddr->sin_addr, hp->h_addr_list[i],
272: sizeof(hostaddr->sin_addr));
1.1 deraadt 273:
274: debug("Connecting to %.200s [%.100s] port %d.",
1.12 provos 275: host, inet_ntoa(hostaddr->sin_addr), port);
1.1 deraadt 276:
277: /* Create a socket for connecting. */
278: sock = ssh_create_socket(original_real_uid,
279: !anonymous && geteuid() == 0 &&
1.9 deraadt 280: port < IPPORT_RESERVED);
1.1 deraadt 281:
282: /* Connect to the host. We use the user's uid in the hope that
283: it will help with tcp_wrappers showing the remote uid as
284: root. */
285: temporarily_use_uid(original_real_uid);
1.12 provos 286: if (connect(sock, (struct sockaddr *)hostaddr,
287: sizeof(*hostaddr)) >= 0)
1.1 deraadt 288: {
289: /* Successful connection. */
290: restore_uid();
291: break;
292: }
293: debug("connect: %.100s", strerror(errno));
294: restore_uid();
295:
296: /* Close the failed socket; there appear to be some problems
297: when reusing a socket for which connect() has already
298: returned an error. */
1.11 deraadt 299: shutdown(sock, SHUT_RDWR);
1.1 deraadt 300: close(sock);
301: }
302: if (hp->h_addr_list[i])
303: break; /* Successful connection. */
304: }
305:
306: /* Sleep a moment before retrying. */
307: sleep(1);
308: }
309: /* Return failure if we didn't get a successful connection. */
310: if (attempt >= connection_attempts)
311: return 0;
312:
313: debug("Connection established.");
314:
315: /* Set socket options. We would like the socket to disappear as soon as
316: it has been closed for whatever reason. */
317: /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
318: setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (void *)&on, sizeof(on));
319: linger.l_onoff = 1;
320: linger.l_linger = 5;
321: setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger));
322:
323: /* Set the connection. */
1.3 provos 324: packet_set_connection(sock, sock);
1.1 deraadt 325:
326: return 1;
327: }
328:
329: /* Checks if the user has an authentication agent, and if so, tries to
330: authenticate using the agent. */
331:
1.3 provos 332: int
333: try_agent_authentication()
1.1 deraadt 334: {
335: int status, type, bits;
336: char *comment;
337: AuthenticationConnection *auth;
338: unsigned char response[16];
339: unsigned int i;
1.3 provos 340: BIGNUM *e, *n, *challenge;
1.1 deraadt 341:
342: /* Get connection to the agent. */
343: auth = ssh_get_authentication_connection();
344: if (!auth)
345: return 0;
346:
1.3 provos 347: e = BN_new();
348: n = BN_new();
349: challenge = BN_new();
1.1 deraadt 350:
351: /* Loop through identities served by the agent. */
1.3 provos 352: for (status = ssh_get_first_identity(auth, &bits, e, n, &comment);
1.1 deraadt 353: status;
1.3 provos 354: status = ssh_get_next_identity(auth, &bits, e, n, &comment))
1.1 deraadt 355: {
356: int plen, clen;
357:
358: /* Try this identity. */
359: debug("Trying RSA authentication via agent with '%.100s'", comment);
360: xfree(comment);
361:
362: /* Tell the server that we are willing to authenticate using this key. */
363: packet_start(SSH_CMSG_AUTH_RSA);
1.3 provos 364: packet_put_bignum(n);
1.1 deraadt 365: packet_send();
366: packet_write_wait();
367:
368: /* Wait for server's response. */
369: type = packet_read(&plen);
370:
371: /* The server sends failure if it doesn\'t like our key or does not
372: support RSA authentication. */
373: if (type == SSH_SMSG_FAILURE)
374: {
375: debug("Server refused our key.");
376: continue;
377: }
378:
379: /* Otherwise it should have sent a challenge. */
380: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
381: packet_disconnect("Protocol error during RSA authentication: %d",
382: type);
383:
1.3 provos 384: packet_get_bignum(challenge, &clen);
1.1 deraadt 385:
386: packet_integrity_check(plen, clen, type);
387:
388: debug("Received RSA challenge from server.");
389:
390: /* Ask the agent to decrypt the challenge. */
1.3 provos 391: if (!ssh_decrypt_challenge(auth, bits, e, n, challenge,
1.1 deraadt 392: session_id, 1, response))
393: {
394: /* The agent failed to authenticate this identifier although it
395: advertised it supports this. Just return a wrong value. */
396: log("Authentication agent failed to decrypt challenge.");
397: memset(response, 0, sizeof(response));
398: }
399:
400: debug("Sending response to RSA challenge.");
401:
402: /* Send the decrypted challenge back to the server. */
403: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
404: for (i = 0; i < 16; i++)
405: packet_put_char(response[i]);
406: packet_send();
407: packet_write_wait();
408:
409: /* Wait for response from the server. */
410: type = packet_read(&plen);
411:
412: /* The server returns success if it accepted the authentication. */
413: if (type == SSH_SMSG_SUCCESS)
414: {
415: debug("RSA authentication accepted by server.");
1.3 provos 416: BN_clear_free(e);
417: BN_clear_free(n);
418: BN_clear_free(challenge);
1.1 deraadt 419: return 1;
420: }
421:
422: /* Otherwise it should return failure. */
423: if (type != SSH_SMSG_FAILURE)
424: packet_disconnect("Protocol error waiting RSA auth response: %d",
425: type);
426: }
427:
1.3 provos 428: BN_clear_free(e);
429: BN_clear_free(n);
430: BN_clear_free(challenge);
1.1 deraadt 431:
432: debug("RSA authentication using agent refused.");
433: return 0;
434: }
435:
436: /* Computes the proper response to a RSA challenge, and sends the response to
437: the server. */
438:
1.3 provos 439: void
440: respond_to_rsa_challenge(BIGNUM *challenge, RSA *prv)
1.1 deraadt 441: {
442: unsigned char buf[32], response[16];
1.10 deraadt 443: MD5_CTX md;
1.3 provos 444: int i, len;
1.1 deraadt 445:
446: /* Decrypt the challenge using the private key. */
447: rsa_private_decrypt(challenge, challenge, prv);
448:
449: /* Compute the response. */
450: /* The response is MD5 of decrypted challenge plus session id. */
1.3 provos 451: len = BN_num_bytes(challenge);
452: assert(len <= sizeof(buf) && len);
453: memset(buf, 0, sizeof(buf));
454: BN_bn2bin(challenge, buf + sizeof(buf) - len);
1.24 ! deraadt 455: MD5_Init(&md);
! 456: MD5_Update(&md, buf, 32);
! 457: MD5_Update(&md, session_id, 16);
! 458: MD5_Final(response, &md);
1.1 deraadt 459:
460: debug("Sending response to host key RSA challenge.");
461:
462: /* Send the response back to the server. */
463: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
464: for (i = 0; i < 16; i++)
465: packet_put_char(response[i]);
466: packet_send();
467: packet_write_wait();
468:
469: memset(buf, 0, sizeof(buf));
470: memset(response, 0, sizeof(response));
471: memset(&md, 0, sizeof(md));
472: }
473:
474: /* Checks if the user has authentication file, and if so, tries to authenticate
475: the user using it. */
476:
1.3 provos 477: int
478: try_rsa_authentication(struct passwd *pw, const char *authfile,
479: int may_ask_passphrase)
1.1 deraadt 480: {
1.3 provos 481: BIGNUM *challenge;
482: RSA *private_key;
483: RSA *public_key;
1.1 deraadt 484: char *passphrase, *comment;
485: int type, i;
486: int plen, clen;
487:
488: /* Try to load identification for the authentication key. */
1.3 provos 489: public_key = RSA_new();
490: if (!load_public_key(authfile, public_key, &comment)) {
491: RSA_free(public_key);
1.1 deraadt 492: return 0; /* Could not load it. Fail. */
1.3 provos 493: }
1.1 deraadt 494:
495: debug("Trying RSA authentication with key '%.100s'", comment);
496:
497: /* Tell the server that we are willing to authenticate using this key. */
498: packet_start(SSH_CMSG_AUTH_RSA);
1.3 provos 499: packet_put_bignum(public_key->n);
1.1 deraadt 500: packet_send();
501: packet_write_wait();
502:
503: /* We no longer need the public key. */
1.3 provos 504: RSA_free(public_key);
1.1 deraadt 505:
506: /* Wait for server's response. */
507: type = packet_read(&plen);
508:
509: /* The server responds with failure if it doesn\'t like our key or doesn\'t
510: support RSA authentication. */
511: if (type == SSH_SMSG_FAILURE)
512: {
513: debug("Server refused our key.");
514: xfree(comment);
515: return 0; /* Server refuses to authenticate with this key. */
516: }
517:
518: /* Otherwise, the server should respond with a challenge. */
519: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
520: packet_disconnect("Protocol error during RSA authentication: %d", type);
521:
522: /* Get the challenge from the packet. */
1.3 provos 523: challenge = BN_new();
524: packet_get_bignum(challenge, &clen);
1.1 deraadt 525:
526: packet_integrity_check(plen, clen, type);
527:
528: debug("Received RSA challenge from server.");
529:
1.3 provos 530: private_key = RSA_new();
1.1 deraadt 531: /* Load the private key. Try first with empty passphrase; if it fails,
532: ask for a passphrase. */
1.3 provos 533: if (!load_private_key(authfile, "", private_key, NULL))
1.1 deraadt 534: {
535: char buf[300];
536: /* Request passphrase from the user. We read from /dev/tty to make
537: this work even if stdin has been redirected. If running in
538: batch mode, we just use the empty passphrase, which will fail and
539: return. */
1.6 deraadt 540: snprintf(buf, sizeof buf,
541: "Enter passphrase for RSA key '%.100s': ", comment);
1.1 deraadt 542: if (may_ask_passphrase)
543: passphrase = read_passphrase(buf, 0);
544: else
545: {
546: debug("Will not query passphrase for %.100s in batch mode.",
547: comment);
548: passphrase = xstrdup("");
549: }
550:
551: /* Load the authentication file using the pasphrase. */
1.3 provos 552: if (!load_private_key(authfile, passphrase, private_key, NULL))
1.1 deraadt 553: {
554: memset(passphrase, 0, strlen(passphrase));
555: xfree(passphrase);
556: error("Bad passphrase.");
557:
558: /* Send a dummy response packet to avoid protocol error. */
559: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
560: for (i = 0; i < 16; i++)
561: packet_put_char(0);
562: packet_send();
563: packet_write_wait();
564:
565: /* Expect the server to reject it... */
566: packet_read_expect(&plen, SSH_SMSG_FAILURE);
567: xfree(comment);
568: return 0;
569: }
570:
571: /* Destroy the passphrase. */
572: memset(passphrase, 0, strlen(passphrase));
573: xfree(passphrase);
574: }
575:
576: /* We no longer need the comment. */
577: xfree(comment);
578:
579: /* Compute and send a response to the challenge. */
1.3 provos 580: respond_to_rsa_challenge(challenge, private_key);
1.1 deraadt 581:
582: /* Destroy the private key. */
1.3 provos 583: RSA_free(private_key);
1.1 deraadt 584:
585: /* We no longer need the challenge. */
1.3 provos 586: BN_clear_free(challenge);
1.1 deraadt 587:
588: /* Wait for response from the server. */
589: type = packet_read(&plen);
590: if (type == SSH_SMSG_SUCCESS)
591: {
592: debug("RSA authentication accepted by server.");
593: return 1;
594: }
595: if (type != SSH_SMSG_FAILURE)
596: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
597: debug("RSA authentication refused.");
598: return 0;
599: }
600:
601: /* Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
602: authentication and RSA host authentication. */
603:
1.3 provos 604: int
605: try_rhosts_rsa_authentication(const char *local_user, RSA *host_key)
1.1 deraadt 606: {
607: int type;
1.3 provos 608: BIGNUM *challenge;
1.1 deraadt 609: int plen, clen;
610:
611: debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
612:
613: /* Tell the server that we are willing to authenticate using this key. */
614: packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
615: packet_put_string(local_user, strlen(local_user));
1.3 provos 616: packet_put_int(BN_num_bits(host_key->n));
617: packet_put_bignum(host_key->e);
618: packet_put_bignum(host_key->n);
1.1 deraadt 619: packet_send();
620: packet_write_wait();
621:
622: /* Wait for server's response. */
623: type = packet_read(&plen);
624:
625: /* The server responds with failure if it doesn't admit our .rhosts
626: authentication or doesn't know our host key. */
627: if (type == SSH_SMSG_FAILURE)
628: {
629: debug("Server refused our rhosts authentication or host key.");
630: return 0; /* Server refuses to authenticate us with this method. */
631: }
632:
633: /* Otherwise, the server should respond with a challenge. */
634: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
635: packet_disconnect("Protocol error during RSA authentication: %d", type);
636:
637: /* Get the challenge from the packet. */
1.3 provos 638: challenge = BN_new();
639: packet_get_bignum(challenge, &clen);
1.1 deraadt 640:
641: packet_integrity_check(plen, clen, type);
642:
643: debug("Received RSA challenge for host key from server.");
644:
645: /* Compute a response to the challenge. */
1.3 provos 646: respond_to_rsa_challenge(challenge, host_key);
1.1 deraadt 647:
648: /* We no longer need the challenge. */
1.3 provos 649: BN_clear_free(challenge);
1.1 deraadt 650:
651: /* Wait for response from the server. */
652: type = packet_read(&plen);
653: if (type == SSH_SMSG_SUCCESS)
654: {
655: debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
656: return 1;
657: }
658: if (type != SSH_SMSG_FAILURE)
659: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
660: debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
661: return 0;
662: }
663:
664: #ifdef KRB4
665: int try_kerberos_authentication()
666: {
667: KTEXT_ST auth; /* Kerberos data */
668: char *reply;
669: char inst[INST_SZ];
670: char *realm;
671: CREDENTIALS cred;
1.5 dugsong 672: int r, type, plen;
1.1 deraadt 673: Key_schedule schedule;
674: u_long checksum, cksum;
675: MSG_DAT msg_data;
676: struct sockaddr_in local, foreign;
677: struct stat st;
678:
679: /* Don't do anything if we don't have any tickets. */
680: if (stat(tkt_string(), &st) < 0) return 0;
681:
682: strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ);
683:
684: realm = (char *)krb_realmofhost(get_canonical_hostname());
685: if (!realm) {
1.5 dugsong 686: debug("Kerberos V4: no realm for %s", get_canonical_hostname());
1.1 deraadt 687: return 0;
688: }
689: /* This can really be anything. */
690: checksum = (u_long) getpid();
691:
692: r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
693: if (r != KSUCCESS) {
1.5 dugsong 694: debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
1.1 deraadt 695: return 0;
696: }
697: /* Get session key to decrypt the server's reply with. */
698: r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
699: if (r != KSUCCESS) {
1.5 dugsong 700: debug("get_cred failed: %s", krb_err_txt[r]);
1.1 deraadt 701: return 0;
702: }
703: des_key_sched((des_cblock *)cred.session, schedule);
704:
705: /* Send authentication info to server. */
706: packet_start(SSH_CMSG_AUTH_KERBEROS);
707: packet_put_string((char *)auth.dat, auth.length);
708: packet_send();
709: packet_write_wait();
710:
1.5 dugsong 711: /* Zero the buffer. */
1.1 deraadt 712: (void) memset(auth.dat, 0, MAX_KTXT_LEN);
713:
714: r = sizeof(local);
715: memset(&local, 0, sizeof(local));
716: if (getsockname(packet_get_connection_in(),
717: (struct sockaddr *) &local, &r) < 0)
1.5 dugsong 718: debug("getsockname failed: %s", strerror(errno));
1.1 deraadt 719:
720: r = sizeof(foreign);
721: memset(&foreign, 0, sizeof(foreign));
722: if (getpeername(packet_get_connection_in(),
723: (struct sockaddr *)&foreign, &r) < 0)
1.5 dugsong 724: debug("getpeername failed: %s", strerror(errno));
1.1 deraadt 725:
726: /* Get server reply. */
727: type = packet_read(&plen);
728: switch(type) {
729:
730: case SSH_SMSG_FAILURE: /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
731: debug("Kerberos V4 authentication failed.");
732: return 0;
733: break;
734:
735: case SSH_SMSG_AUTH_KERBEROS_RESPONSE: /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
736: debug("Kerberos V4 authentication accepted.");
737:
738: /* Get server's response. */
739: reply = packet_get_string((unsigned int *)&auth.length);
740: memcpy(auth.dat, reply, auth.length);
741: xfree(reply);
742:
743: packet_integrity_check(plen, 4 + auth.length, type);
744:
745: /* If his response isn't properly encrypted with the session key,
746: and the decrypted checksum fails to match, he's bogus. Bail out. */
747: r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
748: &foreign, &local, &msg_data);
749: if (r != KSUCCESS) {
1.5 dugsong 750: debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
1.1 deraadt 751: packet_disconnect("Kerberos V4 challenge failed!");
752: }
1.5 dugsong 753: /* Fetch the (incremented) checksum that we supplied in the request. */
1.1 deraadt 754: (void)memcpy((char *)&cksum, (char *)msg_data.app_data, sizeof(cksum));
755: cksum = ntohl(cksum);
756:
757: /* If it matches, we're golden. */
758: if (cksum == checksum + 1) {
759: debug("Kerberos V4 challenge successful.");
760: return 1;
761: }
762: else
763: packet_disconnect("Kerberos V4 challenge failed!");
764: break;
765:
766: default:
767: packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
768: }
769: return 0;
770: }
771: #endif /* KRB4 */
772:
773: #ifdef AFS
774: int send_kerberos_tgt()
775: {
776: CREDENTIALS *creds;
777: char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
1.5 dugsong 778: int r, type, plen;
1.1 deraadt 779: unsigned char buffer[8192];
780: struct stat st;
781:
782: /* Don't do anything if we don't have any tickets. */
783: if (stat(tkt_string(), &st) < 0) return 0;
784:
1.5 dugsong 785: creds = xmalloc(sizeof(*creds));
1.1 deraadt 786:
1.5 dugsong 787: if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
788: debug("Kerberos V4 tf_fullname failed: %s",krb_err_txt[r]);
1.1 deraadt 789: return 0;
1.5 dugsong 790: }
791: if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
792: debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
1.1 deraadt 793: return 0;
794: }
795: if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
1.5 dugsong 796: debug("Kerberos V4 ticket expired: %s", TKT_FILE);
1.1 deraadt 797: return 0;
798: }
799:
800: creds_to_radix(creds, buffer);
801: xfree(creds);
802:
803: packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
804: packet_put_string((char *)buffer, strlen(buffer));
805: packet_send();
806: packet_write_wait();
807:
808: type = packet_read(&plen);
1.5 dugsong 809:
1.1 deraadt 810: if (type == SSH_SMSG_FAILURE)
1.5 dugsong 811: debug("Kerberos TGT for realm %s rejected.", prealm);
1.1 deraadt 812: else if (type != SSH_SMSG_SUCCESS)
813: packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
814:
815: return 1;
816: }
817:
818: void send_afs_tokens(void)
819: {
820: CREDENTIALS creds;
821: struct ViceIoctl parms;
822: struct ClearToken ct;
1.5 dugsong 823: int i, type, len, plen;
1.1 deraadt 824: char buf[2048], *p, *server_cell;
825: unsigned char buffer[8192];
826:
827: /* Move over ktc_GetToken, here's something leaner. */
828: for (i = 0; i < 100; i++) { /* just in case */
829: parms.in = (char *)&i;
830: parms.in_size = sizeof(i);
831: parms.out = buf;
832: parms.out_size = sizeof(buf);
833: if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) break;
834: p = buf;
835:
836: /* Get secret token. */
837: memcpy(&creds.ticket_st.length, p, sizeof(unsigned int));
838: if (creds.ticket_st.length > MAX_KTXT_LEN) break;
839: p += sizeof(unsigned int);
840: memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
841: p += creds.ticket_st.length;
842:
843: /* Get clear token. */
844: memcpy(&len, p, sizeof(len));
845: if (len != sizeof(struct ClearToken)) break;
846: p += sizeof(len);
847: memcpy(&ct, p, len);
848: p += len;
849: p += sizeof(len); /* primary flag */
850: server_cell = p;
851:
852: /* Flesh out our credentials. */
1.6 deraadt 853: strlcpy(creds.service, "afs", sizeof creds.service);
1.1 deraadt 854: creds.instance[0] = '\0';
1.6 deraadt 855: strlcpy(creds.realm, server_cell, REALM_SZ);
1.1 deraadt 856: memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
857: creds.issue_date = ct.BeginTimestamp;
858: creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
859: creds.kvno = ct.AuthHandle;
1.5 dugsong 860: snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
1.1 deraadt 861: creds.pinst[0] = '\0';
862:
863: /* Encode token, ship it off. */
864: if (!creds_to_radix(&creds, buffer)) break;
865: packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
866: packet_put_string((char *)buffer, strlen(buffer));
867: packet_send();
868: packet_write_wait();
869:
870: /* Roger, Roger. Clearance, Clarence. What's your vector, Victor? */
871: type = packet_read(&plen);
872:
873: if (type == SSH_SMSG_FAILURE)
1.5 dugsong 874: debug("AFS token for cell %s rejected.", server_cell);
1.1 deraadt 875: else if (type != SSH_SMSG_SUCCESS)
876: packet_disconnect("Protocol error on AFS token response: %d", type);
877: }
878: }
879: #endif /* AFS */
880:
881: /* Waits for the server identification string, and sends our own identification
882: string. */
883:
884: void ssh_exchange_identification()
885: {
886: char buf[256], remote_version[256]; /* must be same size! */
887: int remote_major, remote_minor, i;
888: int connection_in = packet_get_connection_in();
889: int connection_out = packet_get_connection_out();
1.17 markus 890: extern Options options;
1.1 deraadt 891:
892: /* Read other side\'s version identification. */
893: for (i = 0; i < sizeof(buf) - 1; i++)
894: {
895: if (read(connection_in, &buf[i], 1) != 1)
896: fatal("read: %.100s", strerror(errno));
897: if (buf[i] == '\r')
898: {
899: buf[i] = '\n';
900: buf[i + 1] = 0;
901: break;
902: }
903: if (buf[i] == '\n')
904: {
905: buf[i + 1] = 0;
906: break;
907: }
908: }
909: buf[sizeof(buf) - 1] = 0;
910:
911: /* Check that the versions match. In future this might accept several
912: versions and set appropriate flags to handle them. */
913: if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor,
914: remote_version) != 3)
915: fatal("Bad remote protocol version identification: '%.100s'", buf);
916: debug("Remote protocol version %d.%d, remote software version %.100s",
917: remote_major, remote_minor, remote_version);
1.17 markus 918:
1.22 markus 919: /* Check if the remote protocol version is too old. */
920: if (remote_major == 1 && remote_minor < 3)
921: fatal("Remote machine has too old SSH software version.");
1.21 markus 922:
1.22 markus 923: /* We speak 1.3, too. */
1.21 markus 924: if (remote_major == 1 && remote_minor == 3) {
925: enable_compat13();
926: if (options.forward_agent && strcmp(remote_version, SSH_VERSION) != 0) {
927: log("Agent forwarding disabled, remote version '%s' is not compatible.",
1.23 markus 928: remote_version);
1.17 markus 929: options.forward_agent = 0;
930: }
1.21 markus 931: }
1.1 deraadt 932: #if 0
933: /* Removed for now, to permit compatibility with latter versions. The server
934: will reject our version and disconnect if it doesn't support it. */
935: if (remote_major != PROTOCOL_MAJOR)
936: fatal("Protocol major versions differ: %d vs. %d",
937: PROTOCOL_MAJOR, remote_major);
938: #endif
939:
940: /* Send our own protocol version identification. */
1.6 deraadt 941: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.1 deraadt 942: PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
943: if (write(connection_out, buf, strlen(buf)) != strlen(buf))
944: fatal("write: %.100s", strerror(errno));
945: }
946:
947: int ssh_cipher_default = SSH_CIPHER_3DES;
948:
949: int read_yes_or_no(const char *prompt, int defval)
950: {
951: char buf[1024];
952: FILE *f;
953: int retval = -1;
954:
955: if (isatty(0))
956: f = stdin;
957: else
958: f = fopen("/dev/tty", "rw");
959:
960: if (f == NULL)
961: return 0;
962:
963: fflush(stdout);
964:
965: while (1)
966: {
967: fprintf(stderr, "%s", prompt);
968: if (fgets(buf, sizeof(buf), f) == NULL)
969: {
970: /* Print a newline (the prompt probably didn\'t have one). */
971: fprintf(stderr, "\n");
1.6 deraadt 972: strlcpy(buf, "no", sizeof buf);
1.1 deraadt 973: }
974: /* Remove newline from response. */
975: if (strchr(buf, '\n'))
976: *strchr(buf, '\n') = 0;
977:
978: if (buf[0] == 0)
979: retval = defval;
980: if (strcmp(buf, "yes") == 0)
981: retval = 1;
982: if (strcmp(buf, "no") == 0)
983: retval = 0;
984:
985: if (retval != -1)
986: {
987: if (f != stdin)
988: fclose(f);
989: return retval;
990: }
991: }
992: }
993:
994: /* Starts a dialog with the server, and authenticates the current user on the
995: server. This does not need any extra privileges. The basic connection
996: to the server must already have been established before this is called.
997: User is the remote user; if it is NULL, the current local user name will
998: be used. Anonymous indicates that no rhosts authentication will be used.
999: If login fails, this function prints an error and never returns.
1000: This function does not require super-user privileges. */
1001:
1.3 provos 1002: void ssh_login(int host_key_valid,
1003: RSA *own_host_key,
1.1 deraadt 1004: const char *orighost,
1.12 provos 1005: struct sockaddr_in *hostaddr,
1.1 deraadt 1006: Options *options, uid_t original_real_uid)
1007: {
1008: int i, type;
1009: char *password;
1010: struct passwd *pw;
1.3 provos 1011: BIGNUM *key;
1.12 provos 1012: RSA *host_key, *file_key;
1.3 provos 1013: RSA *public_key;
1.1 deraadt 1014: unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1015: const char *server_user, *local_user;
1.15 provos 1016: char *cp, *host, *ip = NULL;
1.1 deraadt 1017: unsigned char check_bytes[8];
1018: unsigned int supported_ciphers, supported_authentications, protocol_flags;
1019: HostStatus host_status;
1.12 provos 1020: HostStatus ip_status;
1.20 provos 1021: int host_ip_differ = 0;
1.15 provos 1022: int local = (ntohl(hostaddr->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1.1 deraadt 1023: int payload_len, clen, sum_len = 0;
1.5 dugsong 1024: u_int32_t rand = 0;
1.1 deraadt 1025:
1.15 provos 1026: if (options->check_host_ip)
1027: ip = xstrdup(inet_ntoa(hostaddr->sin_addr));
1028:
1.1 deraadt 1029: /* Convert the user-supplied hostname into all lowercase. */
1030: host = xstrdup(orighost);
1031: for (cp = host; *cp; cp++)
1032: if (isupper(*cp))
1033: *cp = tolower(*cp);
1034:
1035: /* Exchange protocol version identification strings with the server. */
1036: ssh_exchange_identification();
1037:
1038: /* Put the connection into non-blocking mode. */
1039: packet_set_nonblocking();
1040:
1041: /* Get local user name. Use it as server user if no user name
1042: was given. */
1043: pw = getpwuid(original_real_uid);
1044: if (!pw)
1045: fatal("User id %d not found from user database.", original_real_uid);
1046: local_user = xstrdup(pw->pw_name);
1047: server_user = options->user ? options->user : local_user;
1048:
1049: debug("Waiting for server public key.");
1050:
1051: /* Wait for a public key packet from the server. */
1052: packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
1053:
1054: /* Get check bytes from the packet. */
1055: for (i = 0; i < 8; i++)
1056: check_bytes[i] = packet_get_char();
1057:
1058: /* Get the public key. */
1.3 provos 1059: public_key = RSA_new();
1060: packet_get_int(); /* bits */
1061: public_key->e = BN_new();
1062: packet_get_bignum(public_key->e, &clen);
1.1 deraadt 1063: sum_len += clen;
1.3 provos 1064: public_key->n = BN_new();
1065: packet_get_bignum(public_key->n, &clen);
1.1 deraadt 1066: sum_len += clen;
1067:
1068: /* Get the host key. */
1.3 provos 1069: host_key = RSA_new();
1070: packet_get_int(); /* bits */
1071: host_key->e = BN_new();
1072: packet_get_bignum(host_key->e, &clen);
1.1 deraadt 1073: sum_len += clen;
1.3 provos 1074: host_key->n = BN_new();
1075: packet_get_bignum(host_key->n, &clen);
1.1 deraadt 1076: sum_len += clen;
1077:
1.13 provos 1078: /* Store the host key from the known host file in here
1079: * so that we can compare it with the key for the IP
1080: * address. */
1081: file_key = RSA_new();
1082: file_key->n = BN_new();
1083: file_key->e = BN_new();
1.12 provos 1084:
1.1 deraadt 1085: /* Get protocol flags. */
1086: protocol_flags = packet_get_int();
1087: packet_set_protocol_flags(protocol_flags);
1088:
1089: /* Get supported cipher types. */
1090: supported_ciphers = packet_get_int();
1091:
1092: /* Get supported authentication types. */
1093: supported_authentications = packet_get_int();
1094:
1095: debug("Received server public key (%d bits) and host key (%d bits).",
1.3 provos 1096: BN_num_bits(public_key->n), BN_num_bits(host_key->n));
1.1 deraadt 1097:
1098: packet_integrity_check(payload_len,
1099: 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
1100: SSH_SMSG_PUBLIC_KEY);
1101:
1102: /* Compute the session id. */
1.3 provos 1103: compute_session_id(session_id, check_bytes,
1104: BN_num_bits(host_key->n), host_key->n,
1105: BN_num_bits(public_key->n), public_key->n);
1.1 deraadt 1106:
1107: /* Check if the host key is present in the user\'s list of known hosts
1108: or in the systemwide list. */
1109: host_status = check_host_in_hostfile(options->user_hostfile,
1.3 provos 1110: host, BN_num_bits(host_key->n),
1.12 provos 1111: host_key->e, host_key->n,
1112: file_key->e, file_key->n);
1.1 deraadt 1113: if (host_status == HOST_NEW)
1114: host_status = check_host_in_hostfile(options->system_hostfile, host,
1.3 provos 1115: BN_num_bits(host_key->n),
1.12 provos 1116: host_key->e, host_key->n,
1117: file_key->e, file_key->n);
1.1 deraadt 1118: /* Force accepting of the host key for localhost and 127.0.0.1.
1119: The problem is that if the home directory is NFS-mounted to multiple
1120: machines, localhost will refer to a different machine in each of them,
1121: and the user will get bogus HOST_CHANGED warnings. This essentially
1122: disables host authentication for localhost; however, this is probably
1123: not a real problem. */
1.15 provos 1124: if (local) {
1125: debug("Forcing accepting of host key for localhost.");
1126: host_status = HOST_OK;
1127: }
1.1 deraadt 1128:
1.14 provos 1129: /* Also perform check for the ip address, skip the check if we are
1130: localhost or the hostname was an ip address to begin with */
1.15 provos 1131: if (options->check_host_ip && !local && strcmp(host, ip)) {
1.12 provos 1132: RSA *ip_key = RSA_new();
1133: ip_key->n = BN_new();
1134: ip_key->e = BN_new();
1.15 provos 1135: ip_status = check_host_in_hostfile(options->user_hostfile, ip,
1.12 provos 1136: BN_num_bits(host_key->n),
1137: host_key->e, host_key->n,
1138: ip_key->e, ip_key->n);
1139:
1140: if (ip_status == HOST_NEW)
1.15 provos 1141: ip_status = check_host_in_hostfile(options->system_hostfile, ip,
1.12 provos 1142: BN_num_bits(host_key->n),
1143: host_key->e, host_key->n,
1144: ip_key->e, ip_key->n);
1.20 provos 1145: if (host_status == HOST_CHANGED &&
1146: (ip_status != HOST_CHANGED ||
1147: (BN_cmp(ip_key->e, file_key->e) || BN_cmp(ip_key->n, file_key->n))))
1148: host_ip_differ = 1;
1.12 provos 1149:
1150: RSA_free(ip_key);
1151: } else
1152: ip_status = host_status;
1.13 provos 1153:
1154: RSA_free(file_key);
1.12 provos 1155:
1156: switch (host_status) {
1157: case HOST_OK:
1158: /* The host is known and the key matches. */
1159: debug("Host '%.200s' is known and matches the host key.", host);
1160: if (options->check_host_ip) {
1161: if (ip_status == HOST_NEW) {
1.15 provos 1162: if (!add_host_to_hostfile(options->user_hostfile, ip,
1.12 provos 1163: BN_num_bits(host_key->n),
1164: host_key->e, host_key->n))
1165: log("Failed to add the host ip to the list of known hosts (%.30s).",
1166: options->user_hostfile);
1167: else
1.15 provos 1168: log("Warning: Permanently added host ip '%.30s' to the list of known hosts.", ip);
1.12 provos 1169: } else if (ip_status != HOST_OK)
1.15 provos 1170: log("Warning: the host key differ from the key of the ip address '%.30s' differs", ip);
1.12 provos 1171: }
1172:
1173: break;
1174: case HOST_NEW:
1.1 deraadt 1175: {
1.12 provos 1176: char hostline[1000], *hostp = hostline;
1.1 deraadt 1177: /* The host is new. */
1.12 provos 1178: if (options->strict_host_key_checking == 1) {
1179: /* User has requested strict host key checking. We will not
1180: add the host key automatically. The only alternative left
1181: is to abort. */
1182: fatal("No host key is known for %.200s and you have requested strict checking.", host);
1183: } else if (options->strict_host_key_checking == 2) { /* The default */
1184: char prompt[1024];
1185: snprintf(prompt, sizeof(prompt),
1186: "The authenticity of host '%.200s' can't be established.\n"
1187: "Are you sure you want to continue connecting (yes/no)? ",
1188: host);
1189: if (!read_yes_or_no(prompt, -1))
1190: fatal("Aborted by user!\n");
1191: }
1192:
1.15 provos 1193: if (options->check_host_ip && ip_status == HOST_NEW && strcmp(host, ip))
1194: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1.12 provos 1195: else
1196: hostp = host;
1197:
1.1 deraadt 1198: /* If not in strict mode, add the key automatically to the local
1199: known_hosts file. */
1.12 provos 1200: if (!add_host_to_hostfile(options->user_hostfile, hostp,
1.3 provos 1201: BN_num_bits(host_key->n),
1202: host_key->e, host_key->n))
1.1 deraadt 1203: log("Failed to add the host to the list of known hosts (%.500s).",
1204: options->user_hostfile);
1205: else
1.12 provos 1206: log("Warning: Permanently added '%.200s' to the list of known hosts.",
1207: hostp);
1.1 deraadt 1208: break;
1209: }
1.12 provos 1210: case HOST_CHANGED:
1211: if (options->check_host_ip) {
1.20 provos 1212: if (host_ip_differ) {
1.12 provos 1213: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.19 markus 1214: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1.12 provos 1215: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1216: error("The host key for %s has changed,", host);
1.15 provos 1217: error("but the key for the according IP address %s has", ip);
1.12 provos 1218: error("a different status. This could either mean that DNS");
1219: error("SPOOFING is happening or the IP address for the host");
1220: error("and its host key have changed at the same time");
1221: }
1222: }
1223:
1224: /* The host key has changed. */
1225: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1226: error("@ WARNING: HOST IDENTIFICATION HAS CHANGED! @");
1227: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1228: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1229: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1230: error("It is also possible that the host key has just been changed.");
1231: error("Please contact your system administrator.");
1232: error("Add correct host key in %.100s to get rid of this message.",
1233: options->user_hostfile);
1234:
1235: /* If strict host key checking is in use, the user will have to edit
1236: the key manually and we can only abort. */
1237: if (options->strict_host_key_checking)
1238: fatal("Host key for %.200s has changed and you have requested strict checking.", host);
1239:
1240: /* If strict host key checking has not been requested, allow the
1.19 markus 1241: connection but without password authentication or
1242: agent forwarding. */
1243: if (options->password_authentication) {
1244: error("Password authentication is disabled to avoid trojan horses.");
1245: options->password_authentication = 0;
1246: }
1247: if (options->forward_agent) {
1248: error("Agent forwarding is disabled to avoid trojan horses.");
1249: options->forward_agent = 0;
1250: }
1.12 provos 1251: /* XXX Should permit the user to change to use the new id. This could
1252: be done by converting the host key to an identifying sentence, tell
1253: that the host identifies itself by that sentence, and ask the user
1254: if he/she whishes to accept the authentication. */
1255: break;
1256: }
1.15 provos 1257:
1258: if (options->check_host_ip)
1259: xfree(ip);
1.12 provos 1260:
1.1 deraadt 1261: /* Generate a session key. */
1.3 provos 1262: arc4random_stir();
1.1 deraadt 1263:
1264: /* Generate an encryption key for the session. The key is a 256 bit
1265: random number, interpreted as a 32-byte key, with the least significant
1266: 8 bits being the first byte of the key. */
1.3 provos 1267: for (i = 0; i < 32; i++) {
1268: if (i % 4 == 0)
1269: rand = arc4random();
1270: session_key[i] = rand & 0xff;
1271: rand >>= 8;
1272: }
1.1 deraadt 1273:
1274: /* According to the protocol spec, the first byte of the session key is
1275: the highest byte of the integer. The session key is xored with the
1276: first 16 bytes of the session id. */
1.3 provos 1277: key = BN_new();
1278: BN_set_word(key, 0);
1.1 deraadt 1279: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++)
1280: {
1.3 provos 1281: BN_lshift(key, key, 8);
1.1 deraadt 1282: if (i < 16)
1.3 provos 1283: BN_add_word(key, session_key[i] ^ session_id[i]);
1.1 deraadt 1284: else
1.3 provos 1285: BN_add_word(key, session_key[i]);
1.1 deraadt 1286: }
1287:
1288: /* Encrypt the integer using the public key and host key of the server
1289: (key with smaller modulus first). */
1.3 provos 1290: if (BN_cmp(public_key->n, host_key->n) < 0)
1.1 deraadt 1291: {
1292: /* Public key has smaller modulus. */
1.3 provos 1293: assert(BN_num_bits(host_key->n) >=
1294: BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED);
1.1 deraadt 1295:
1.3 provos 1296: rsa_public_encrypt(key, key, public_key);
1297: rsa_public_encrypt(key, key, host_key);
1.1 deraadt 1298: }
1299: else
1300: {
1301: /* Host key has smaller modulus (or they are equal). */
1.3 provos 1302: assert(BN_num_bits(public_key->n) >=
1303: BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED);
1.1 deraadt 1304:
1.3 provos 1305: rsa_public_encrypt(key, key, host_key);
1306: rsa_public_encrypt(key, key, public_key);
1.1 deraadt 1307: }
1308:
1.3 provos 1309: if (options->cipher == SSH_CIPHER_NOT_SET) {
1.1 deraadt 1310: if (cipher_mask() & supported_ciphers & (1 << ssh_cipher_default))
1311: options->cipher = ssh_cipher_default;
1.3 provos 1312: else {
1313: debug("Cipher %d not supported, using %.100s instead.",
1314: cipher_name(ssh_cipher_default),
1315: cipher_name(SSH_FALLBACK_CIPHER));
1316: options->cipher = SSH_FALLBACK_CIPHER;
1317: }
1318: }
1.1 deraadt 1319:
1320: /* Check that the selected cipher is supported. */
1321: if (!(supported_ciphers & (1 << options->cipher)))
1322: fatal("Selected cipher type %.100s not supported by server.",
1323: cipher_name(options->cipher));
1324:
1325: debug("Encryption type: %.100s", cipher_name(options->cipher));
1326:
1327: /* Send the encrypted session key to the server. */
1328: packet_start(SSH_CMSG_SESSION_KEY);
1329: packet_put_char(options->cipher);
1330:
1331: /* Send the check bytes back to the server. */
1332: for (i = 0; i < 8; i++)
1333: packet_put_char(check_bytes[i]);
1334:
1335: /* Send the encrypted encryption key. */
1.3 provos 1336: packet_put_bignum(key);
1.1 deraadt 1337:
1338: /* Send protocol flags. */
1339: packet_put_int(SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1340:
1341: /* Send the packet now. */
1342: packet_send();
1343: packet_write_wait();
1344:
1345: /* Destroy the session key integer and the public keys since we no longer
1346: need them. */
1.3 provos 1347: BN_clear_free(key);
1348: RSA_free(public_key);
1349: RSA_free(host_key);
1.1 deraadt 1350:
1351: debug("Sent encrypted session key.");
1352:
1353: /* Set the encryption key. */
1354: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH,
1355: options->cipher, 1);
1356:
1357: /* We will no longer need the session key here. Destroy any extra copies. */
1358: memset(session_key, 0, sizeof(session_key));
1359:
1360: /* Expect a success message from the server. Note that this message will
1361: be received in encrypted form. */
1362: packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
1363:
1364: debug("Received encrypted confirmation.");
1365:
1366: /* Send the name of the user to log in as on the server. */
1367: packet_start(SSH_CMSG_USER);
1368: packet_put_string(server_user, strlen(server_user));
1369: packet_send();
1370: packet_write_wait();
1371:
1372: /* The server should respond with success if no authentication is needed
1373: (the user has no password). Otherwise the server responds with
1374: failure. */
1375: type = packet_read(&payload_len);
1376: if (type == SSH_SMSG_SUCCESS)
1377: return; /* Connection was accepted without authentication. */
1378: if (type != SSH_SMSG_FAILURE)
1379: packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
1380: type);
1381:
1.5 dugsong 1382: #ifdef AFS
1.1 deraadt 1383: /* Try Kerberos tgt passing if the server supports it. */
1384: if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
1.5 dugsong 1385: options->kerberos_tgt_passing)
1386: {
1387: if (options->cipher == SSH_CIPHER_NONE)
1388: log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
1389: (void)send_kerberos_tgt();
1390: }
1391:
1.1 deraadt 1392: /* Try AFS token passing if the server supports it. */
1393: if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
1394: options->afs_token_passing && k_hasafs()) {
1395: if (options->cipher == SSH_CIPHER_NONE)
1396: log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
1397: send_afs_tokens();
1398: }
1399: #endif /* AFS */
1400:
1.5 dugsong 1401: #ifdef KRB4
1.1 deraadt 1402: if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
1403: options->kerberos_authentication)
1404: {
1.5 dugsong 1405: debug("Trying Kerberos authentication.");
1.1 deraadt 1406: if (try_kerberos_authentication()) {
1407: /* The server should respond with success or failure. */
1408: type = packet_read(&payload_len);
1409: if (type == SSH_SMSG_SUCCESS)
1410: return; /* Successful connection. */
1411: if (type != SSH_SMSG_FAILURE)
1412: packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
1413: }
1414: }
1415: #endif /* KRB4 */
1416:
1417: /* Use rhosts authentication if running in privileged socket and we do not
1418: wish to remain anonymous. */
1419: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
1420: options->rhosts_authentication)
1421: {
1422: debug("Trying rhosts authentication.");
1423: packet_start(SSH_CMSG_AUTH_RHOSTS);
1424: packet_put_string(local_user, strlen(local_user));
1425: packet_send();
1426: packet_write_wait();
1427:
1428: /* The server should respond with success or failure. */
1429: type = packet_read(&payload_len);
1430: if (type == SSH_SMSG_SUCCESS)
1431: return; /* Successful connection. */
1432: if (type != SSH_SMSG_FAILURE)
1433: packet_disconnect("Protocol error: got %d in response to rhosts auth",
1434: type);
1435: }
1436:
1437: /* Try .rhosts or /etc/hosts.equiv authentication with RSA host
1438: authentication. */
1439: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
1440: options->rhosts_rsa_authentication && host_key_valid)
1441: {
1442: if (try_rhosts_rsa_authentication(local_user, own_host_key))
1443: return; /* Successful authentication. */
1444: }
1445:
1446: /* Try RSA authentication if the server supports it. */
1447: if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
1448: options->rsa_authentication)
1449: {
1450: /* Try RSA authentication using the authentication agent. The agent
1451: is tried first because no passphrase is needed for it, whereas
1452: identity files may require passphrases. */
1453: if (try_agent_authentication())
1454: return; /* Successful connection. */
1455:
1456: /* Try RSA authentication for each identity. */
1457: for (i = 0; i < options->num_identity_files; i++)
1458: if (try_rsa_authentication(pw, options->identity_files[i],
1459: !options->batch_mode))
1460: return; /* Successful connection. */
1461: }
1462:
1463: /* Try password authentication if the server supports it. */
1464: if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
1465: options->password_authentication && !options->batch_mode)
1466: {
1.4 provos 1467: char prompt[80];
1468: snprintf(prompt, sizeof(prompt), "%.30s@%.30s's password: ",
1469: server_user, host);
1.1 deraadt 1470: debug("Doing password authentication.");
1471: if (options->cipher == SSH_CIPHER_NONE)
1472: log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
1.16 dugsong 1473: for (i = 0; i < options->number_of_password_prompts; i++) {
1.18 markus 1474: if (i != 0)
1475: error("Permission denied, please try again.");
1.16 dugsong 1476: password = read_passphrase(prompt, 0);
1477: packet_start(SSH_CMSG_AUTH_PASSWORD);
1478: packet_put_string(password, strlen(password));
1479: memset(password, 0, strlen(password));
1480: xfree(password);
1481: packet_send();
1482: packet_write_wait();
1483:
1484: type = packet_read(&payload_len);
1485: if (type == SSH_SMSG_SUCCESS)
1486: return; /* Successful connection. */
1487: if (type != SSH_SMSG_FAILURE)
1488: packet_disconnect("Protocol error: got %d in response to passwd auth", type);
1489: }
1.1 deraadt 1490: }
1491:
1492: /* All authentication methods have failed. Exit with an error message. */
1493: fatal("Permission denied.");
1494: /*NOTREACHED*/
1495: }
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