Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.26
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"
1.26 ! markus 18: RCSID("$Id: sshconnect.c,v 1.25 1999/11/02 19:42:36 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);
1.25 markus 452: if (len <= 0 || len > sizeof(buf))
453: packet_disconnect("respond_to_rsa_challenge: bad challenge length %d",
454: len);
455:
1.3 provos 456: memset(buf, 0, sizeof(buf));
457: BN_bn2bin(challenge, buf + sizeof(buf) - len);
1.24 deraadt 458: MD5_Init(&md);
459: MD5_Update(&md, buf, 32);
460: MD5_Update(&md, session_id, 16);
461: MD5_Final(response, &md);
1.1 deraadt 462:
463: debug("Sending response to host key RSA challenge.");
464:
465: /* Send the response back to the server. */
466: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
467: for (i = 0; i < 16; i++)
468: packet_put_char(response[i]);
469: packet_send();
470: packet_write_wait();
471:
472: memset(buf, 0, sizeof(buf));
473: memset(response, 0, sizeof(response));
474: memset(&md, 0, sizeof(md));
475: }
476:
477: /* Checks if the user has authentication file, and if so, tries to authenticate
478: the user using it. */
479:
1.3 provos 480: int
481: try_rsa_authentication(struct passwd *pw, const char *authfile,
482: int may_ask_passphrase)
1.1 deraadt 483: {
1.3 provos 484: BIGNUM *challenge;
485: RSA *private_key;
486: RSA *public_key;
1.1 deraadt 487: char *passphrase, *comment;
488: int type, i;
489: int plen, clen;
490:
491: /* Try to load identification for the authentication key. */
1.3 provos 492: public_key = RSA_new();
493: if (!load_public_key(authfile, public_key, &comment)) {
494: RSA_free(public_key);
1.1 deraadt 495: return 0; /* Could not load it. Fail. */
1.3 provos 496: }
1.1 deraadt 497:
498: debug("Trying RSA authentication with key '%.100s'", comment);
499:
500: /* Tell the server that we are willing to authenticate using this key. */
501: packet_start(SSH_CMSG_AUTH_RSA);
1.3 provos 502: packet_put_bignum(public_key->n);
1.1 deraadt 503: packet_send();
504: packet_write_wait();
505:
506: /* We no longer need the public key. */
1.3 provos 507: RSA_free(public_key);
1.1 deraadt 508:
509: /* Wait for server's response. */
510: type = packet_read(&plen);
511:
512: /* The server responds with failure if it doesn\'t like our key or doesn\'t
513: support RSA authentication. */
514: if (type == SSH_SMSG_FAILURE)
515: {
516: debug("Server refused our key.");
517: xfree(comment);
518: return 0; /* Server refuses to authenticate with this key. */
519: }
520:
521: /* Otherwise, the server should respond with a challenge. */
522: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
523: packet_disconnect("Protocol error during RSA authentication: %d", type);
524:
525: /* Get the challenge from the packet. */
1.3 provos 526: challenge = BN_new();
527: packet_get_bignum(challenge, &clen);
1.1 deraadt 528:
529: packet_integrity_check(plen, clen, type);
530:
531: debug("Received RSA challenge from server.");
532:
1.3 provos 533: private_key = RSA_new();
1.1 deraadt 534: /* Load the private key. Try first with empty passphrase; if it fails,
535: ask for a passphrase. */
1.3 provos 536: if (!load_private_key(authfile, "", private_key, NULL))
1.1 deraadt 537: {
538: char buf[300];
539: /* Request passphrase from the user. We read from /dev/tty to make
540: this work even if stdin has been redirected. If running in
541: batch mode, we just use the empty passphrase, which will fail and
542: return. */
1.6 deraadt 543: snprintf(buf, sizeof buf,
544: "Enter passphrase for RSA key '%.100s': ", comment);
1.1 deraadt 545: if (may_ask_passphrase)
546: passphrase = read_passphrase(buf, 0);
547: else
548: {
549: debug("Will not query passphrase for %.100s in batch mode.",
550: comment);
551: passphrase = xstrdup("");
552: }
553:
554: /* Load the authentication file using the pasphrase. */
1.3 provos 555: if (!load_private_key(authfile, passphrase, private_key, NULL))
1.1 deraadt 556: {
557: memset(passphrase, 0, strlen(passphrase));
558: xfree(passphrase);
559: error("Bad passphrase.");
560:
561: /* Send a dummy response packet to avoid protocol error. */
562: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
563: for (i = 0; i < 16; i++)
564: packet_put_char(0);
565: packet_send();
566: packet_write_wait();
567:
568: /* Expect the server to reject it... */
569: packet_read_expect(&plen, SSH_SMSG_FAILURE);
570: xfree(comment);
571: return 0;
572: }
573:
574: /* Destroy the passphrase. */
575: memset(passphrase, 0, strlen(passphrase));
576: xfree(passphrase);
577: }
578:
579: /* We no longer need the comment. */
580: xfree(comment);
581:
582: /* Compute and send a response to the challenge. */
1.3 provos 583: respond_to_rsa_challenge(challenge, private_key);
1.1 deraadt 584:
585: /* Destroy the private key. */
1.3 provos 586: RSA_free(private_key);
1.1 deraadt 587:
588: /* We no longer need the challenge. */
1.3 provos 589: BN_clear_free(challenge);
1.1 deraadt 590:
591: /* Wait for response from the server. */
592: type = packet_read(&plen);
593: if (type == SSH_SMSG_SUCCESS)
594: {
595: debug("RSA authentication accepted by server.");
596: return 1;
597: }
598: if (type != SSH_SMSG_FAILURE)
599: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
600: debug("RSA authentication refused.");
601: return 0;
602: }
603:
604: /* Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
605: authentication and RSA host authentication. */
606:
1.3 provos 607: int
608: try_rhosts_rsa_authentication(const char *local_user, RSA *host_key)
1.1 deraadt 609: {
610: int type;
1.3 provos 611: BIGNUM *challenge;
1.1 deraadt 612: int plen, clen;
613:
614: debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
615:
616: /* Tell the server that we are willing to authenticate using this key. */
617: packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
618: packet_put_string(local_user, strlen(local_user));
1.3 provos 619: packet_put_int(BN_num_bits(host_key->n));
620: packet_put_bignum(host_key->e);
621: packet_put_bignum(host_key->n);
1.1 deraadt 622: packet_send();
623: packet_write_wait();
624:
625: /* Wait for server's response. */
626: type = packet_read(&plen);
627:
628: /* The server responds with failure if it doesn't admit our .rhosts
629: authentication or doesn't know our host key. */
630: if (type == SSH_SMSG_FAILURE)
631: {
632: debug("Server refused our rhosts authentication or host key.");
633: return 0; /* Server refuses to authenticate us with this method. */
634: }
635:
636: /* Otherwise, the server should respond with a challenge. */
637: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
638: packet_disconnect("Protocol error during RSA authentication: %d", type);
639:
640: /* Get the challenge from the packet. */
1.3 provos 641: challenge = BN_new();
642: packet_get_bignum(challenge, &clen);
1.1 deraadt 643:
644: packet_integrity_check(plen, clen, type);
645:
646: debug("Received RSA challenge for host key from server.");
647:
648: /* Compute a response to the challenge. */
1.3 provos 649: respond_to_rsa_challenge(challenge, host_key);
1.1 deraadt 650:
651: /* We no longer need the challenge. */
1.3 provos 652: BN_clear_free(challenge);
1.1 deraadt 653:
654: /* Wait for response from the server. */
655: type = packet_read(&plen);
656: if (type == SSH_SMSG_SUCCESS)
657: {
658: debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
659: return 1;
660: }
661: if (type != SSH_SMSG_FAILURE)
662: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
663: debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
664: return 0;
665: }
666:
667: #ifdef KRB4
668: int try_kerberos_authentication()
669: {
670: KTEXT_ST auth; /* Kerberos data */
671: char *reply;
672: char inst[INST_SZ];
673: char *realm;
674: CREDENTIALS cred;
1.5 dugsong 675: int r, type, plen;
1.1 deraadt 676: Key_schedule schedule;
677: u_long checksum, cksum;
678: MSG_DAT msg_data;
679: struct sockaddr_in local, foreign;
680: struct stat st;
681:
682: /* Don't do anything if we don't have any tickets. */
683: if (stat(tkt_string(), &st) < 0) return 0;
684:
685: strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ);
686:
687: realm = (char *)krb_realmofhost(get_canonical_hostname());
688: if (!realm) {
1.5 dugsong 689: debug("Kerberos V4: no realm for %s", get_canonical_hostname());
1.1 deraadt 690: return 0;
691: }
692: /* This can really be anything. */
693: checksum = (u_long) getpid();
694:
695: r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
696: if (r != KSUCCESS) {
1.5 dugsong 697: debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
1.1 deraadt 698: return 0;
699: }
700: /* Get session key to decrypt the server's reply with. */
701: r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
702: if (r != KSUCCESS) {
1.5 dugsong 703: debug("get_cred failed: %s", krb_err_txt[r]);
1.1 deraadt 704: return 0;
705: }
706: des_key_sched((des_cblock *)cred.session, schedule);
707:
708: /* Send authentication info to server. */
709: packet_start(SSH_CMSG_AUTH_KERBEROS);
710: packet_put_string((char *)auth.dat, auth.length);
711: packet_send();
712: packet_write_wait();
713:
1.5 dugsong 714: /* Zero the buffer. */
1.1 deraadt 715: (void) memset(auth.dat, 0, MAX_KTXT_LEN);
716:
717: r = sizeof(local);
718: memset(&local, 0, sizeof(local));
719: if (getsockname(packet_get_connection_in(),
720: (struct sockaddr *) &local, &r) < 0)
1.5 dugsong 721: debug("getsockname failed: %s", strerror(errno));
1.1 deraadt 722:
723: r = sizeof(foreign);
724: memset(&foreign, 0, sizeof(foreign));
725: if (getpeername(packet_get_connection_in(),
726: (struct sockaddr *)&foreign, &r) < 0)
1.5 dugsong 727: debug("getpeername failed: %s", strerror(errno));
1.1 deraadt 728:
729: /* Get server reply. */
730: type = packet_read(&plen);
731: switch(type) {
732:
733: case SSH_SMSG_FAILURE: /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
734: debug("Kerberos V4 authentication failed.");
735: return 0;
736: break;
737:
738: case SSH_SMSG_AUTH_KERBEROS_RESPONSE: /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
739: debug("Kerberos V4 authentication accepted.");
740:
741: /* Get server's response. */
742: reply = packet_get_string((unsigned int *)&auth.length);
743: memcpy(auth.dat, reply, auth.length);
744: xfree(reply);
745:
746: packet_integrity_check(plen, 4 + auth.length, type);
747:
748: /* If his response isn't properly encrypted with the session key,
749: and the decrypted checksum fails to match, he's bogus. Bail out. */
750: r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
751: &foreign, &local, &msg_data);
752: if (r != KSUCCESS) {
1.5 dugsong 753: debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
1.1 deraadt 754: packet_disconnect("Kerberos V4 challenge failed!");
755: }
1.5 dugsong 756: /* Fetch the (incremented) checksum that we supplied in the request. */
1.1 deraadt 757: (void)memcpy((char *)&cksum, (char *)msg_data.app_data, sizeof(cksum));
758: cksum = ntohl(cksum);
759:
760: /* If it matches, we're golden. */
761: if (cksum == checksum + 1) {
762: debug("Kerberos V4 challenge successful.");
763: return 1;
764: }
765: else
766: packet_disconnect("Kerberos V4 challenge failed!");
767: break;
768:
769: default:
770: packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
771: }
772: return 0;
773: }
774: #endif /* KRB4 */
775:
776: #ifdef AFS
777: int send_kerberos_tgt()
778: {
779: CREDENTIALS *creds;
780: char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
1.5 dugsong 781: int r, type, plen;
1.1 deraadt 782: unsigned char buffer[8192];
783: struct stat st;
784:
785: /* Don't do anything if we don't have any tickets. */
786: if (stat(tkt_string(), &st) < 0) return 0;
787:
1.5 dugsong 788: creds = xmalloc(sizeof(*creds));
1.1 deraadt 789:
1.5 dugsong 790: if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
791: debug("Kerberos V4 tf_fullname failed: %s",krb_err_txt[r]);
1.1 deraadt 792: return 0;
1.5 dugsong 793: }
794: if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
795: debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
1.1 deraadt 796: return 0;
797: }
798: if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
1.5 dugsong 799: debug("Kerberos V4 ticket expired: %s", TKT_FILE);
1.1 deraadt 800: return 0;
801: }
802:
803: creds_to_radix(creds, buffer);
804: xfree(creds);
805:
806: packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
807: packet_put_string((char *)buffer, strlen(buffer));
808: packet_send();
809: packet_write_wait();
810:
811: type = packet_read(&plen);
1.5 dugsong 812:
1.1 deraadt 813: if (type == SSH_SMSG_FAILURE)
1.5 dugsong 814: debug("Kerberos TGT for realm %s rejected.", prealm);
1.1 deraadt 815: else if (type != SSH_SMSG_SUCCESS)
816: packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
817:
818: return 1;
819: }
820:
821: void send_afs_tokens(void)
822: {
823: CREDENTIALS creds;
824: struct ViceIoctl parms;
825: struct ClearToken ct;
1.5 dugsong 826: int i, type, len, plen;
1.1 deraadt 827: char buf[2048], *p, *server_cell;
828: unsigned char buffer[8192];
829:
830: /* Move over ktc_GetToken, here's something leaner. */
831: for (i = 0; i < 100; i++) { /* just in case */
832: parms.in = (char *)&i;
833: parms.in_size = sizeof(i);
834: parms.out = buf;
835: parms.out_size = sizeof(buf);
836: if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) break;
837: p = buf;
838:
839: /* Get secret token. */
840: memcpy(&creds.ticket_st.length, p, sizeof(unsigned int));
841: if (creds.ticket_st.length > MAX_KTXT_LEN) break;
842: p += sizeof(unsigned int);
843: memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
844: p += creds.ticket_st.length;
845:
846: /* Get clear token. */
847: memcpy(&len, p, sizeof(len));
848: if (len != sizeof(struct ClearToken)) break;
849: p += sizeof(len);
850: memcpy(&ct, p, len);
851: p += len;
852: p += sizeof(len); /* primary flag */
853: server_cell = p;
854:
855: /* Flesh out our credentials. */
1.6 deraadt 856: strlcpy(creds.service, "afs", sizeof creds.service);
1.1 deraadt 857: creds.instance[0] = '\0';
1.6 deraadt 858: strlcpy(creds.realm, server_cell, REALM_SZ);
1.1 deraadt 859: memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
860: creds.issue_date = ct.BeginTimestamp;
861: creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
862: creds.kvno = ct.AuthHandle;
1.5 dugsong 863: snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
1.1 deraadt 864: creds.pinst[0] = '\0';
865:
866: /* Encode token, ship it off. */
867: if (!creds_to_radix(&creds, buffer)) break;
868: packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
869: packet_put_string((char *)buffer, strlen(buffer));
870: packet_send();
871: packet_write_wait();
872:
873: /* Roger, Roger. Clearance, Clarence. What's your vector, Victor? */
874: type = packet_read(&plen);
875:
876: if (type == SSH_SMSG_FAILURE)
1.5 dugsong 877: debug("AFS token for cell %s rejected.", server_cell);
1.1 deraadt 878: else if (type != SSH_SMSG_SUCCESS)
879: packet_disconnect("Protocol error on AFS token response: %d", type);
880: }
881: }
882: #endif /* AFS */
883:
884: /* Waits for the server identification string, and sends our own identification
885: string. */
886:
887: void ssh_exchange_identification()
888: {
889: char buf[256], remote_version[256]; /* must be same size! */
890: int remote_major, remote_minor, i;
891: int connection_in = packet_get_connection_in();
892: int connection_out = packet_get_connection_out();
1.17 markus 893: extern Options options;
1.1 deraadt 894:
895: /* Read other side\'s version identification. */
896: for (i = 0; i < sizeof(buf) - 1; i++)
897: {
898: if (read(connection_in, &buf[i], 1) != 1)
899: fatal("read: %.100s", strerror(errno));
900: if (buf[i] == '\r')
901: {
902: buf[i] = '\n';
903: buf[i + 1] = 0;
904: break;
905: }
906: if (buf[i] == '\n')
907: {
908: buf[i + 1] = 0;
909: break;
910: }
911: }
912: buf[sizeof(buf) - 1] = 0;
913:
914: /* Check that the versions match. In future this might accept several
915: versions and set appropriate flags to handle them. */
916: if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor,
917: remote_version) != 3)
918: fatal("Bad remote protocol version identification: '%.100s'", buf);
919: debug("Remote protocol version %d.%d, remote software version %.100s",
920: remote_major, remote_minor, remote_version);
1.17 markus 921:
1.22 markus 922: /* Check if the remote protocol version is too old. */
923: if (remote_major == 1 && remote_minor < 3)
924: fatal("Remote machine has too old SSH software version.");
1.21 markus 925:
1.22 markus 926: /* We speak 1.3, too. */
1.21 markus 927: if (remote_major == 1 && remote_minor == 3) {
928: enable_compat13();
929: if (options.forward_agent && strcmp(remote_version, SSH_VERSION) != 0) {
930: log("Agent forwarding disabled, remote version '%s' is not compatible.",
1.23 markus 931: remote_version);
1.17 markus 932: options.forward_agent = 0;
933: }
1.21 markus 934: }
1.1 deraadt 935: #if 0
936: /* Removed for now, to permit compatibility with latter versions. The server
937: will reject our version and disconnect if it doesn't support it. */
938: if (remote_major != PROTOCOL_MAJOR)
939: fatal("Protocol major versions differ: %d vs. %d",
940: PROTOCOL_MAJOR, remote_major);
941: #endif
942:
943: /* Send our own protocol version identification. */
1.6 deraadt 944: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.1 deraadt 945: PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
946: if (write(connection_out, buf, strlen(buf)) != strlen(buf))
947: fatal("write: %.100s", strerror(errno));
948: }
949:
950: int ssh_cipher_default = SSH_CIPHER_3DES;
951:
952: int read_yes_or_no(const char *prompt, int defval)
953: {
954: char buf[1024];
955: FILE *f;
956: int retval = -1;
957:
958: if (isatty(0))
959: f = stdin;
960: else
961: f = fopen("/dev/tty", "rw");
962:
963: if (f == NULL)
964: return 0;
965:
966: fflush(stdout);
967:
968: while (1)
969: {
970: fprintf(stderr, "%s", prompt);
971: if (fgets(buf, sizeof(buf), f) == NULL)
972: {
973: /* Print a newline (the prompt probably didn\'t have one). */
974: fprintf(stderr, "\n");
1.6 deraadt 975: strlcpy(buf, "no", sizeof buf);
1.1 deraadt 976: }
977: /* Remove newline from response. */
978: if (strchr(buf, '\n'))
979: *strchr(buf, '\n') = 0;
980:
981: if (buf[0] == 0)
982: retval = defval;
983: if (strcmp(buf, "yes") == 0)
984: retval = 1;
985: if (strcmp(buf, "no") == 0)
986: retval = 0;
987:
988: if (retval != -1)
989: {
990: if (f != stdin)
991: fclose(f);
992: return retval;
993: }
994: }
995: }
996:
997: /* Starts a dialog with the server, and authenticates the current user on the
998: server. This does not need any extra privileges. The basic connection
999: to the server must already have been established before this is called.
1000: User is the remote user; if it is NULL, the current local user name will
1001: be used. Anonymous indicates that no rhosts authentication will be used.
1002: If login fails, this function prints an error and never returns.
1003: This function does not require super-user privileges. */
1004:
1.3 provos 1005: void ssh_login(int host_key_valid,
1006: RSA *own_host_key,
1.1 deraadt 1007: const char *orighost,
1.12 provos 1008: struct sockaddr_in *hostaddr,
1.1 deraadt 1009: Options *options, uid_t original_real_uid)
1010: {
1011: int i, type;
1012: char *password;
1013: struct passwd *pw;
1.3 provos 1014: BIGNUM *key;
1.12 provos 1015: RSA *host_key, *file_key;
1.3 provos 1016: RSA *public_key;
1.26 ! markus 1017: int bits, rbits;
1.1 deraadt 1018: unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1019: const char *server_user, *local_user;
1.15 provos 1020: char *cp, *host, *ip = NULL;
1.1 deraadt 1021: unsigned char check_bytes[8];
1022: unsigned int supported_ciphers, supported_authentications, protocol_flags;
1023: HostStatus host_status;
1.12 provos 1024: HostStatus ip_status;
1.20 provos 1025: int host_ip_differ = 0;
1.15 provos 1026: int local = (ntohl(hostaddr->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1.1 deraadt 1027: int payload_len, clen, sum_len = 0;
1.5 dugsong 1028: u_int32_t rand = 0;
1.1 deraadt 1029:
1.15 provos 1030: if (options->check_host_ip)
1031: ip = xstrdup(inet_ntoa(hostaddr->sin_addr));
1032:
1.1 deraadt 1033: /* Convert the user-supplied hostname into all lowercase. */
1034: host = xstrdup(orighost);
1035: for (cp = host; *cp; cp++)
1036: if (isupper(*cp))
1037: *cp = tolower(*cp);
1038:
1039: /* Exchange protocol version identification strings with the server. */
1040: ssh_exchange_identification();
1041:
1042: /* Put the connection into non-blocking mode. */
1043: packet_set_nonblocking();
1044:
1045: /* Get local user name. Use it as server user if no user name
1046: was given. */
1047: pw = getpwuid(original_real_uid);
1048: if (!pw)
1049: fatal("User id %d not found from user database.", original_real_uid);
1050: local_user = xstrdup(pw->pw_name);
1051: server_user = options->user ? options->user : local_user;
1052:
1053: debug("Waiting for server public key.");
1054:
1055: /* Wait for a public key packet from the server. */
1056: packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
1057:
1058: /* Get check bytes from the packet. */
1059: for (i = 0; i < 8; i++)
1060: check_bytes[i] = packet_get_char();
1061:
1062: /* Get the public key. */
1.3 provos 1063: public_key = RSA_new();
1.26 ! markus 1064: bits = packet_get_int(); /* bits */
1.3 provos 1065: public_key->e = BN_new();
1066: packet_get_bignum(public_key->e, &clen);
1.1 deraadt 1067: sum_len += clen;
1.3 provos 1068: public_key->n = BN_new();
1069: packet_get_bignum(public_key->n, &clen);
1.1 deraadt 1070: sum_len += clen;
1071:
1.26 ! markus 1072: rbits = BN_num_bits(public_key->n);
! 1073: if (bits != rbits) {
! 1074: log("Warning: Server lies about size of server public key,");
! 1075: log("Warning: this may be due to an old implementation of ssh.");
! 1076: log("Warning: (actual size %d bits, announced size %d bits)", rbits, bits);
! 1077: }
! 1078:
1.1 deraadt 1079: /* Get the host key. */
1.3 provos 1080: host_key = RSA_new();
1.26 ! markus 1081: bits = packet_get_int(); /* bits */
1.3 provos 1082: host_key->e = BN_new();
1083: packet_get_bignum(host_key->e, &clen);
1.1 deraadt 1084: sum_len += clen;
1.3 provos 1085: host_key->n = BN_new();
1086: packet_get_bignum(host_key->n, &clen);
1.1 deraadt 1087: sum_len += clen;
1.26 ! markus 1088:
! 1089: rbits = BN_num_bits(host_key->n);
! 1090: if (bits != rbits) {
! 1091: log("Warning: Server lies about size of server host key,");
! 1092: log("Warning: this may be due to an old implementation of ssh.");
! 1093: log("Warning: (actual size %d bits, announced size %d bits)", rbits, bits);
! 1094: }
1.1 deraadt 1095:
1.13 provos 1096: /* Store the host key from the known host file in here
1097: * so that we can compare it with the key for the IP
1098: * address. */
1099: file_key = RSA_new();
1100: file_key->n = BN_new();
1101: file_key->e = BN_new();
1.12 provos 1102:
1.1 deraadt 1103: /* Get protocol flags. */
1104: protocol_flags = packet_get_int();
1105: packet_set_protocol_flags(protocol_flags);
1106:
1107: /* Get supported cipher types. */
1108: supported_ciphers = packet_get_int();
1109:
1110: /* Get supported authentication types. */
1111: supported_authentications = packet_get_int();
1112:
1113: debug("Received server public key (%d bits) and host key (%d bits).",
1.3 provos 1114: BN_num_bits(public_key->n), BN_num_bits(host_key->n));
1.1 deraadt 1115:
1116: packet_integrity_check(payload_len,
1117: 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
1118: SSH_SMSG_PUBLIC_KEY);
1119:
1120: /* Compute the session id. */
1.3 provos 1121: compute_session_id(session_id, check_bytes,
1122: BN_num_bits(host_key->n), host_key->n,
1123: BN_num_bits(public_key->n), public_key->n);
1.1 deraadt 1124:
1125: /* Check if the host key is present in the user\'s list of known hosts
1126: or in the systemwide list. */
1127: host_status = check_host_in_hostfile(options->user_hostfile,
1.3 provos 1128: host, BN_num_bits(host_key->n),
1.12 provos 1129: host_key->e, host_key->n,
1130: file_key->e, file_key->n);
1.1 deraadt 1131: if (host_status == HOST_NEW)
1132: host_status = check_host_in_hostfile(options->system_hostfile, host,
1.3 provos 1133: BN_num_bits(host_key->n),
1.12 provos 1134: host_key->e, host_key->n,
1135: file_key->e, file_key->n);
1.1 deraadt 1136: /* Force accepting of the host key for localhost and 127.0.0.1.
1137: The problem is that if the home directory is NFS-mounted to multiple
1138: machines, localhost will refer to a different machine in each of them,
1139: and the user will get bogus HOST_CHANGED warnings. This essentially
1140: disables host authentication for localhost; however, this is probably
1141: not a real problem. */
1.15 provos 1142: if (local) {
1143: debug("Forcing accepting of host key for localhost.");
1144: host_status = HOST_OK;
1145: }
1.1 deraadt 1146:
1.14 provos 1147: /* Also perform check for the ip address, skip the check if we are
1148: localhost or the hostname was an ip address to begin with */
1.15 provos 1149: if (options->check_host_ip && !local && strcmp(host, ip)) {
1.12 provos 1150: RSA *ip_key = RSA_new();
1151: ip_key->n = BN_new();
1152: ip_key->e = BN_new();
1.15 provos 1153: ip_status = check_host_in_hostfile(options->user_hostfile, ip,
1.12 provos 1154: BN_num_bits(host_key->n),
1155: host_key->e, host_key->n,
1156: ip_key->e, ip_key->n);
1157:
1158: if (ip_status == HOST_NEW)
1.15 provos 1159: ip_status = check_host_in_hostfile(options->system_hostfile, ip,
1.12 provos 1160: BN_num_bits(host_key->n),
1161: host_key->e, host_key->n,
1162: ip_key->e, ip_key->n);
1.20 provos 1163: if (host_status == HOST_CHANGED &&
1164: (ip_status != HOST_CHANGED ||
1165: (BN_cmp(ip_key->e, file_key->e) || BN_cmp(ip_key->n, file_key->n))))
1166: host_ip_differ = 1;
1.12 provos 1167:
1168: RSA_free(ip_key);
1169: } else
1170: ip_status = host_status;
1.13 provos 1171:
1172: RSA_free(file_key);
1.12 provos 1173:
1174: switch (host_status) {
1175: case HOST_OK:
1176: /* The host is known and the key matches. */
1177: debug("Host '%.200s' is known and matches the host key.", host);
1178: if (options->check_host_ip) {
1179: if (ip_status == HOST_NEW) {
1.15 provos 1180: if (!add_host_to_hostfile(options->user_hostfile, ip,
1.12 provos 1181: BN_num_bits(host_key->n),
1182: host_key->e, host_key->n))
1183: log("Failed to add the host ip to the list of known hosts (%.30s).",
1184: options->user_hostfile);
1185: else
1.15 provos 1186: log("Warning: Permanently added host ip '%.30s' to the list of known hosts.", ip);
1.12 provos 1187: } else if (ip_status != HOST_OK)
1.15 provos 1188: log("Warning: the host key differ from the key of the ip address '%.30s' differs", ip);
1.12 provos 1189: }
1190:
1191: break;
1192: case HOST_NEW:
1.1 deraadt 1193: {
1.12 provos 1194: char hostline[1000], *hostp = hostline;
1.1 deraadt 1195: /* The host is new. */
1.12 provos 1196: if (options->strict_host_key_checking == 1) {
1197: /* User has requested strict host key checking. We will not
1198: add the host key automatically. The only alternative left
1199: is to abort. */
1200: fatal("No host key is known for %.200s and you have requested strict checking.", host);
1201: } else if (options->strict_host_key_checking == 2) { /* The default */
1202: char prompt[1024];
1203: snprintf(prompt, sizeof(prompt),
1204: "The authenticity of host '%.200s' can't be established.\n"
1205: "Are you sure you want to continue connecting (yes/no)? ",
1206: host);
1207: if (!read_yes_or_no(prompt, -1))
1208: fatal("Aborted by user!\n");
1209: }
1210:
1.15 provos 1211: if (options->check_host_ip && ip_status == HOST_NEW && strcmp(host, ip))
1212: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1.12 provos 1213: else
1214: hostp = host;
1215:
1.1 deraadt 1216: /* If not in strict mode, add the key automatically to the local
1217: known_hosts file. */
1.12 provos 1218: if (!add_host_to_hostfile(options->user_hostfile, hostp,
1.3 provos 1219: BN_num_bits(host_key->n),
1220: host_key->e, host_key->n))
1.1 deraadt 1221: log("Failed to add the host to the list of known hosts (%.500s).",
1222: options->user_hostfile);
1223: else
1.12 provos 1224: log("Warning: Permanently added '%.200s' to the list of known hosts.",
1225: hostp);
1.1 deraadt 1226: break;
1227: }
1.12 provos 1228: case HOST_CHANGED:
1229: if (options->check_host_ip) {
1.20 provos 1230: if (host_ip_differ) {
1.12 provos 1231: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.19 markus 1232: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1.12 provos 1233: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1234: error("The host key for %s has changed,", host);
1.15 provos 1235: error("but the key for the according IP address %s has", ip);
1.12 provos 1236: error("a different status. This could either mean that DNS");
1237: error("SPOOFING is happening or the IP address for the host");
1238: error("and its host key have changed at the same time");
1239: }
1240: }
1241:
1242: /* The host key has changed. */
1243: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1244: error("@ WARNING: HOST IDENTIFICATION HAS CHANGED! @");
1245: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1246: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1247: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1248: error("It is also possible that the host key has just been changed.");
1249: error("Please contact your system administrator.");
1250: error("Add correct host key in %.100s to get rid of this message.",
1251: options->user_hostfile);
1252:
1253: /* If strict host key checking is in use, the user will have to edit
1254: the key manually and we can only abort. */
1255: if (options->strict_host_key_checking)
1256: fatal("Host key for %.200s has changed and you have requested strict checking.", host);
1257:
1258: /* If strict host key checking has not been requested, allow the
1.19 markus 1259: connection but without password authentication or
1260: agent forwarding. */
1261: if (options->password_authentication) {
1262: error("Password authentication is disabled to avoid trojan horses.");
1263: options->password_authentication = 0;
1264: }
1265: if (options->forward_agent) {
1266: error("Agent forwarding is disabled to avoid trojan horses.");
1267: options->forward_agent = 0;
1268: }
1.12 provos 1269: /* XXX Should permit the user to change to use the new id. This could
1270: be done by converting the host key to an identifying sentence, tell
1271: that the host identifies itself by that sentence, and ask the user
1272: if he/she whishes to accept the authentication. */
1273: break;
1274: }
1.15 provos 1275:
1276: if (options->check_host_ip)
1277: xfree(ip);
1.12 provos 1278:
1.1 deraadt 1279: /* Generate a session key. */
1.3 provos 1280: arc4random_stir();
1.1 deraadt 1281:
1282: /* Generate an encryption key for the session. The key is a 256 bit
1283: random number, interpreted as a 32-byte key, with the least significant
1284: 8 bits being the first byte of the key. */
1.3 provos 1285: for (i = 0; i < 32; i++) {
1286: if (i % 4 == 0)
1287: rand = arc4random();
1288: session_key[i] = rand & 0xff;
1289: rand >>= 8;
1290: }
1.1 deraadt 1291:
1292: /* According to the protocol spec, the first byte of the session key is
1293: the highest byte of the integer. The session key is xored with the
1294: first 16 bytes of the session id. */
1.3 provos 1295: key = BN_new();
1296: BN_set_word(key, 0);
1.1 deraadt 1297: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++)
1298: {
1.3 provos 1299: BN_lshift(key, key, 8);
1.1 deraadt 1300: if (i < 16)
1.3 provos 1301: BN_add_word(key, session_key[i] ^ session_id[i]);
1.1 deraadt 1302: else
1.3 provos 1303: BN_add_word(key, session_key[i]);
1.1 deraadt 1304: }
1305:
1306: /* Encrypt the integer using the public key and host key of the server
1307: (key with smaller modulus first). */
1.3 provos 1308: if (BN_cmp(public_key->n, host_key->n) < 0)
1.1 deraadt 1309: {
1310: /* Public key has smaller modulus. */
1.25 markus 1311: if (BN_num_bits(host_key->n) <
1312: BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
1313: fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
1314: "SSH_KEY_BITS_RESERVED %d",
1315: BN_num_bits(host_key->n),
1316: BN_num_bits(public_key->n),
1317: SSH_KEY_BITS_RESERVED);
1318: }
1.1 deraadt 1319:
1.3 provos 1320: rsa_public_encrypt(key, key, public_key);
1321: rsa_public_encrypt(key, key, host_key);
1.1 deraadt 1322: }
1323: else
1324: {
1325: /* Host key has smaller modulus (or they are equal). */
1.25 markus 1326: if (BN_num_bits(public_key->n) <
1327: BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
1328: fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
1329: "SSH_KEY_BITS_RESERVED %d",
1330: BN_num_bits(public_key->n),
1331: BN_num_bits(host_key->n),
1332: SSH_KEY_BITS_RESERVED);
1333: }
1.1 deraadt 1334:
1.3 provos 1335: rsa_public_encrypt(key, key, host_key);
1336: rsa_public_encrypt(key, key, public_key);
1.1 deraadt 1337: }
1338:
1.3 provos 1339: if (options->cipher == SSH_CIPHER_NOT_SET) {
1.1 deraadt 1340: if (cipher_mask() & supported_ciphers & (1 << ssh_cipher_default))
1341: options->cipher = ssh_cipher_default;
1.3 provos 1342: else {
1343: debug("Cipher %d not supported, using %.100s instead.",
1344: cipher_name(ssh_cipher_default),
1345: cipher_name(SSH_FALLBACK_CIPHER));
1346: options->cipher = SSH_FALLBACK_CIPHER;
1347: }
1348: }
1.1 deraadt 1349:
1350: /* Check that the selected cipher is supported. */
1351: if (!(supported_ciphers & (1 << options->cipher)))
1352: fatal("Selected cipher type %.100s not supported by server.",
1353: cipher_name(options->cipher));
1354:
1355: debug("Encryption type: %.100s", cipher_name(options->cipher));
1356:
1357: /* Send the encrypted session key to the server. */
1358: packet_start(SSH_CMSG_SESSION_KEY);
1359: packet_put_char(options->cipher);
1360:
1361: /* Send the check bytes back to the server. */
1362: for (i = 0; i < 8; i++)
1363: packet_put_char(check_bytes[i]);
1364:
1365: /* Send the encrypted encryption key. */
1.3 provos 1366: packet_put_bignum(key);
1.1 deraadt 1367:
1368: /* Send protocol flags. */
1369: packet_put_int(SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1370:
1371: /* Send the packet now. */
1372: packet_send();
1373: packet_write_wait();
1374:
1375: /* Destroy the session key integer and the public keys since we no longer
1376: need them. */
1.3 provos 1377: BN_clear_free(key);
1378: RSA_free(public_key);
1379: RSA_free(host_key);
1.1 deraadt 1380:
1381: debug("Sent encrypted session key.");
1382:
1383: /* Set the encryption key. */
1384: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH,
1385: options->cipher, 1);
1386:
1387: /* We will no longer need the session key here. Destroy any extra copies. */
1388: memset(session_key, 0, sizeof(session_key));
1389:
1390: /* Expect a success message from the server. Note that this message will
1391: be received in encrypted form. */
1392: packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
1393:
1394: debug("Received encrypted confirmation.");
1395:
1396: /* Send the name of the user to log in as on the server. */
1397: packet_start(SSH_CMSG_USER);
1398: packet_put_string(server_user, strlen(server_user));
1399: packet_send();
1400: packet_write_wait();
1401:
1402: /* The server should respond with success if no authentication is needed
1403: (the user has no password). Otherwise the server responds with
1404: failure. */
1405: type = packet_read(&payload_len);
1406: if (type == SSH_SMSG_SUCCESS)
1407: return; /* Connection was accepted without authentication. */
1408: if (type != SSH_SMSG_FAILURE)
1409: packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
1410: type);
1411:
1.5 dugsong 1412: #ifdef AFS
1.1 deraadt 1413: /* Try Kerberos tgt passing if the server supports it. */
1414: if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
1.5 dugsong 1415: options->kerberos_tgt_passing)
1416: {
1417: if (options->cipher == SSH_CIPHER_NONE)
1418: log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
1419: (void)send_kerberos_tgt();
1420: }
1421:
1.1 deraadt 1422: /* Try AFS token passing if the server supports it. */
1423: if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
1424: options->afs_token_passing && k_hasafs()) {
1425: if (options->cipher == SSH_CIPHER_NONE)
1426: log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
1427: send_afs_tokens();
1428: }
1429: #endif /* AFS */
1430:
1.5 dugsong 1431: #ifdef KRB4
1.1 deraadt 1432: if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
1433: options->kerberos_authentication)
1434: {
1.5 dugsong 1435: debug("Trying Kerberos authentication.");
1.1 deraadt 1436: if (try_kerberos_authentication()) {
1437: /* The server should respond with success or failure. */
1438: type = packet_read(&payload_len);
1439: if (type == SSH_SMSG_SUCCESS)
1440: return; /* Successful connection. */
1441: if (type != SSH_SMSG_FAILURE)
1442: packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
1443: }
1444: }
1445: #endif /* KRB4 */
1446:
1447: /* Use rhosts authentication if running in privileged socket and we do not
1448: wish to remain anonymous. */
1449: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
1450: options->rhosts_authentication)
1451: {
1452: debug("Trying rhosts authentication.");
1453: packet_start(SSH_CMSG_AUTH_RHOSTS);
1454: packet_put_string(local_user, strlen(local_user));
1455: packet_send();
1456: packet_write_wait();
1457:
1458: /* The server should respond with success or failure. */
1459: type = packet_read(&payload_len);
1460: if (type == SSH_SMSG_SUCCESS)
1461: return; /* Successful connection. */
1462: if (type != SSH_SMSG_FAILURE)
1463: packet_disconnect("Protocol error: got %d in response to rhosts auth",
1464: type);
1465: }
1466:
1467: /* Try .rhosts or /etc/hosts.equiv authentication with RSA host
1468: authentication. */
1469: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
1470: options->rhosts_rsa_authentication && host_key_valid)
1471: {
1472: if (try_rhosts_rsa_authentication(local_user, own_host_key))
1473: return; /* Successful authentication. */
1474: }
1475:
1476: /* Try RSA authentication if the server supports it. */
1477: if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
1478: options->rsa_authentication)
1479: {
1480: /* Try RSA authentication using the authentication agent. The agent
1481: is tried first because no passphrase is needed for it, whereas
1482: identity files may require passphrases. */
1483: if (try_agent_authentication())
1484: return; /* Successful connection. */
1485:
1486: /* Try RSA authentication for each identity. */
1487: for (i = 0; i < options->num_identity_files; i++)
1488: if (try_rsa_authentication(pw, options->identity_files[i],
1489: !options->batch_mode))
1490: return; /* Successful connection. */
1491: }
1492:
1493: /* Try password authentication if the server supports it. */
1494: if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
1495: options->password_authentication && !options->batch_mode)
1496: {
1.4 provos 1497: char prompt[80];
1498: snprintf(prompt, sizeof(prompt), "%.30s@%.30s's password: ",
1499: server_user, host);
1.1 deraadt 1500: debug("Doing password authentication.");
1501: if (options->cipher == SSH_CIPHER_NONE)
1502: log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
1.16 dugsong 1503: for (i = 0; i < options->number_of_password_prompts; i++) {
1.18 markus 1504: if (i != 0)
1505: error("Permission denied, please try again.");
1.16 dugsong 1506: password = read_passphrase(prompt, 0);
1507: packet_start(SSH_CMSG_AUTH_PASSWORD);
1508: packet_put_string(password, strlen(password));
1509: memset(password, 0, strlen(password));
1510: xfree(password);
1511: packet_send();
1512: packet_write_wait();
1513:
1514: type = packet_read(&payload_len);
1515: if (type == SSH_SMSG_SUCCESS)
1516: return; /* Successful connection. */
1517: if (type != SSH_SMSG_FAILURE)
1518: packet_disconnect("Protocol error: got %d in response to passwd auth", type);
1519: }
1.1 deraadt 1520: }
1521:
1522: /* All authentication methods have failed. Exit with an error message. */
1523: fatal("Permission denied.");
1524: /*NOTREACHED*/
1525: }
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