Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.58
1.1 deraadt 1: /*
1.39 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
5: * Created: Sat Mar 18 22:15:47 1995 ylo
6: * Code to connect to a remote host, and to perform the client side of the
7: * login (authentication) dialog.
8: */
1.1 deraadt 9:
10: #include "includes.h"
1.58 ! markus 11: RCSID("$OpenBSD: sshconnect.c,v 1.57 2000/03/16 20:56:14 markus Exp $");
1.1 deraadt 12:
1.3 provos 13: #include <ssl/bn.h>
1.1 deraadt 14: #include "xmalloc.h"
15: #include "rsa.h"
16: #include "ssh.h"
17: #include "packet.h"
18: #include "authfd.h"
19: #include "cipher.h"
20: #include "mpaux.h"
21: #include "uidswap.h"
1.21 markus 22: #include "compat.h"
1.27 markus 23: #include "readconf.h"
1.1 deraadt 24:
1.58 ! markus 25: #include <ssl/rsa.h>
! 26: #include <ssl/dsa.h>
1.24 deraadt 27: #include <ssl/md5.h>
1.58 ! markus 28: #include "key.h"
! 29: #include "hostfile.h"
1.10 deraadt 30:
1.1 deraadt 31: /* Session id for the current session. */
32: unsigned char session_id[16];
33:
1.51 markus 34: /* authentications supported by server */
35: unsigned int supported_authentications;
36:
1.43 markus 37: extern Options options;
1.50 markus 38: extern char *__progname;
1.43 markus 39:
1.39 deraadt 40: /*
41: * Connect to the given ssh server using a proxy command.
42: */
1.3 provos 43: int
1.41 markus 44: ssh_proxy_connect(const char *host, u_short port, uid_t original_real_uid,
1.3 provos 45: const char *proxy_command)
1.1 deraadt 46: {
1.38 markus 47: Buffer command;
48: const char *cp;
49: char *command_string;
50: int pin[2], pout[2];
51: int pid;
1.49 markus 52: char strport[NI_MAXSERV];
1.38 markus 53:
54: /* Convert the port number into a string. */
1.49 markus 55: snprintf(strport, sizeof strport, "%hu", port);
1.38 markus 56:
57: /* Build the final command string in the buffer by making the
58: appropriate substitutions to the given proxy command. */
59: buffer_init(&command);
60: for (cp = proxy_command; *cp; cp++) {
61: if (cp[0] == '%' && cp[1] == '%') {
62: buffer_append(&command, "%", 1);
63: cp++;
64: continue;
65: }
66: if (cp[0] == '%' && cp[1] == 'h') {
67: buffer_append(&command, host, strlen(host));
68: cp++;
69: continue;
70: }
71: if (cp[0] == '%' && cp[1] == 'p') {
1.49 markus 72: buffer_append(&command, strport, strlen(strport));
1.38 markus 73: cp++;
74: continue;
75: }
76: buffer_append(&command, cp, 1);
77: }
78: buffer_append(&command, "\0", 1);
79:
80: /* Get the final command string. */
81: command_string = buffer_ptr(&command);
82:
83: /* Create pipes for communicating with the proxy. */
84: if (pipe(pin) < 0 || pipe(pout) < 0)
85: fatal("Could not create pipes to communicate with the proxy: %.100s",
86: strerror(errno));
87:
88: debug("Executing proxy command: %.500s", command_string);
89:
90: /* Fork and execute the proxy command. */
91: if ((pid = fork()) == 0) {
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: if (dup2(pin[0], 0) < 0)
101: perror("dup2 stdin");
102: close(pin[0]);
103: }
104: close(pout[0]);
105: if (dup2(pout[1], 1) < 0)
106: perror("dup2 stdout");
107: /* Cannot be 1 because pin allocated two descriptors. */
108: close(pout[1]);
109:
110: /* Stderr is left as it is so that error messages get
111: printed on 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
118: extra 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. */
135: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 136:
1.38 markus 137: return 1;
1.1 deraadt 138: }
139:
1.39 deraadt 140: /*
141: * Creates a (possibly privileged) socket for use as the ssh connection.
142: */
1.38 markus 143: int
1.49 markus 144: ssh_create_socket(uid_t original_real_uid, int privileged, int family)
1.1 deraadt 145: {
1.38 markus 146: int sock;
1.1 deraadt 147:
1.40 markus 148: /*
149: * If we are running as root and want to connect to a privileged
150: * port, bind our own socket to a privileged port.
151: */
1.38 markus 152: if (privileged) {
153: int p = IPPORT_RESERVED - 1;
1.49 markus 154: sock = rresvport_af(&p, family);
1.38 markus 155: if (sock < 0)
1.55 markus 156: error("rresvport: af=%d %.100s", family, strerror(errno));
157: else
158: debug("Allocated local port %d.", p);
1.38 markus 159: } else {
1.46 markus 160: /*
161: * Just create an ordinary socket on arbitrary port. We use
162: * the user's uid to create the socket.
163: */
1.38 markus 164: temporarily_use_uid(original_real_uid);
1.49 markus 165: sock = socket(family, SOCK_STREAM, 0);
1.38 markus 166: if (sock < 0)
1.49 markus 167: error("socket: %.100s", strerror(errno));
1.38 markus 168: restore_uid();
169: }
170: return sock;
1.1 deraadt 171: }
172:
1.39 deraadt 173: /*
1.49 markus 174: * Opens a TCP/IP connection to the remote server on the given host.
175: * The address of the remote host will be returned in hostaddr.
176: * If port is 0, the default port will be used. If anonymous is zero,
1.39 deraadt 177: * a privileged port will be allocated to make the connection.
178: * This requires super-user privileges if anonymous is false.
179: * Connection_attempts specifies the maximum number of tries (one per
180: * second). If proxy_command is non-NULL, it specifies the command (with %h
181: * and %p substituted for host and port, respectively) to use to contact
182: * the daemon.
183: */
1.38 markus 184: int
1.49 markus 185: ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
1.41 markus 186: u_short port, int connection_attempts,
1.38 markus 187: int anonymous, uid_t original_real_uid,
188: const char *proxy_command)
1.1 deraadt 189: {
1.49 markus 190: int sock = -1, attempt;
1.38 markus 191: struct servent *sp;
1.49 markus 192: struct addrinfo hints, *ai, *aitop;
193: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
194: int gaierr;
1.38 markus 195: struct linger linger;
196:
197: debug("ssh_connect: getuid %d geteuid %d anon %d",
198: (int) getuid(), (int) geteuid(), anonymous);
199:
200: /* Get default port if port has not been set. */
201: if (port == 0) {
202: sp = getservbyname(SSH_SERVICE_NAME, "tcp");
203: if (sp)
204: port = ntohs(sp->s_port);
205: else
206: port = SSH_DEFAULT_PORT;
207: }
208: /* If a proxy command is given, connect using it. */
209: if (proxy_command != NULL)
210: return ssh_proxy_connect(host, port, original_real_uid, proxy_command);
211:
212: /* No proxy command. */
213:
1.49 markus 214: memset(&hints, 0, sizeof(hints));
215: hints.ai_family = IPv4or6;
216: hints.ai_socktype = SOCK_STREAM;
217: snprintf(strport, sizeof strport, "%d", port);
218: if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
1.50 markus 219: fatal("%s: %.100s: %s", __progname, host,
220: gai_strerror(gaierr));
1.38 markus 221:
1.46 markus 222: /*
223: * Try to connect several times. On some machines, the first time
224: * will sometimes fail. In general socket code appears to behave
225: * quite magically on many machines.
226: */
1.38 markus 227: for (attempt = 0; attempt < connection_attempts; attempt++) {
228: if (attempt > 0)
229: debug("Trying again...");
230:
1.49 markus 231: /* Loop through addresses for this host, and try each one in
232: sequence until the connection succeeds. */
233: for (ai = aitop; ai; ai = ai->ai_next) {
234: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
235: continue;
236: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
237: ntop, sizeof(ntop), strport, sizeof(strport),
238: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
239: error("ssh_connect: getnameinfo failed");
240: continue;
241: }
242: debug("Connecting to %.200s [%.100s] port %s.",
243: host, ntop, strport);
244:
245: /* Create a socket for connecting. */
246: sock = ssh_create_socket(original_real_uid,
247: !anonymous && geteuid() == 0 && port < IPPORT_RESERVED,
248: ai->ai_family);
249: if (sock < 0)
250: continue;
251:
252: /* Connect to the host. We use the user's uid in the
253: * hope that it will help with tcp_wrappers showing
254: * the remote uid as root.
1.40 markus 255: */
1.38 markus 256: temporarily_use_uid(original_real_uid);
1.49 markus 257: if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) {
258: /* Successful connection. */
259: memcpy(hostaddr, ai->ai_addr, sizeof(*hostaddr));
1.38 markus 260: restore_uid();
261: break;
1.49 markus 262: } else {
1.38 markus 263: debug("connect: %.100s", strerror(errno));
264: restore_uid();
1.40 markus 265: /*
266: * Close the failed socket; there appear to
267: * be some problems when reusing a socket for
268: * which connect() has already returned an
269: * error.
270: */
1.38 markus 271: shutdown(sock, SHUT_RDWR);
272: close(sock);
273: }
274: }
1.49 markus 275: if (ai)
276: break; /* Successful connection. */
1.1 deraadt 277:
1.38 markus 278: /* Sleep a moment before retrying. */
279: sleep(1);
280: }
1.49 markus 281:
282: freeaddrinfo(aitop);
283:
1.38 markus 284: /* Return failure if we didn't get a successful connection. */
285: if (attempt >= connection_attempts)
286: return 0;
287:
288: debug("Connection established.");
289:
1.40 markus 290: /*
291: * Set socket options. We would like the socket to disappear as soon
292: * as it has been closed for whatever reason.
293: */
294: /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1.38 markus 295: linger.l_onoff = 1;
296: linger.l_linger = 5;
297: setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
298:
299: /* Set the connection. */
300: packet_set_connection(sock, sock);
1.1 deraadt 301:
1.38 markus 302: return 1;
1.1 deraadt 303: }
304:
1.39 deraadt 305: /*
306: * Checks if the user has an authentication agent, and if so, tries to
307: * authenticate using the agent.
308: */
1.3 provos 309: int
310: try_agent_authentication()
1.1 deraadt 311: {
1.38 markus 312: int status, type;
313: char *comment;
314: AuthenticationConnection *auth;
315: unsigned char response[16];
316: unsigned int i;
317: BIGNUM *e, *n, *challenge;
318:
319: /* Get connection to the agent. */
320: auth = ssh_get_authentication_connection();
321: if (!auth)
322: return 0;
323:
324: e = BN_new();
325: n = BN_new();
326: challenge = BN_new();
327:
328: /* Loop through identities served by the agent. */
329: for (status = ssh_get_first_identity(auth, e, n, &comment);
330: status;
331: status = ssh_get_next_identity(auth, e, n, &comment)) {
332: int plen, clen;
333:
334: /* Try this identity. */
335: debug("Trying RSA authentication via agent with '%.100s'", comment);
336: xfree(comment);
337:
338: /* Tell the server that we are willing to authenticate using this key. */
339: packet_start(SSH_CMSG_AUTH_RSA);
340: packet_put_bignum(n);
341: packet_send();
342: packet_write_wait();
343:
344: /* Wait for server's response. */
345: type = packet_read(&plen);
346:
347: /* The server sends failure if it doesn\'t like our key or
348: does not support RSA authentication. */
349: if (type == SSH_SMSG_FAILURE) {
350: debug("Server refused our key.");
351: continue;
352: }
353: /* Otherwise it should have sent a challenge. */
354: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
355: packet_disconnect("Protocol error during RSA authentication: %d",
356: type);
357:
358: packet_get_bignum(challenge, &clen);
359:
360: packet_integrity_check(plen, clen, type);
361:
362: debug("Received RSA challenge from server.");
363:
364: /* Ask the agent to decrypt the challenge. */
365: if (!ssh_decrypt_challenge(auth, e, n, challenge,
366: session_id, 1, response)) {
367: /* The agent failed to authenticate this identifier although it
368: advertised it supports this. Just return a wrong value. */
369: log("Authentication agent failed to decrypt challenge.");
370: memset(response, 0, sizeof(response));
371: }
372: debug("Sending response to RSA challenge.");
1.1 deraadt 373:
1.38 markus 374: /* Send the decrypted challenge back to the server. */
375: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
376: for (i = 0; i < 16; i++)
377: packet_put_char(response[i]);
378: packet_send();
379: packet_write_wait();
380:
381: /* Wait for response from the server. */
382: type = packet_read(&plen);
383:
384: /* The server returns success if it accepted the authentication. */
385: if (type == SSH_SMSG_SUCCESS) {
386: debug("RSA authentication accepted by server.");
387: BN_clear_free(e);
388: BN_clear_free(n);
389: BN_clear_free(challenge);
390: return 1;
391: }
392: /* Otherwise it should return failure. */
393: if (type != SSH_SMSG_FAILURE)
394: packet_disconnect("Protocol error waiting RSA auth response: %d",
395: type);
396: }
397:
398: BN_clear_free(e);
399: BN_clear_free(n);
400: BN_clear_free(challenge);
401:
402: debug("RSA authentication using agent refused.");
403: return 0;
1.1 deraadt 404: }
405:
1.39 deraadt 406: /*
407: * Computes the proper response to a RSA challenge, and sends the response to
408: * the server.
409: */
1.3 provos 410: void
1.38 markus 411: respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
1.1 deraadt 412: {
1.38 markus 413: unsigned char buf[32], response[16];
414: MD5_CTX md;
415: int i, len;
416:
417: /* Decrypt the challenge using the private key. */
418: rsa_private_decrypt(challenge, challenge, prv);
419:
420: /* Compute the response. */
421: /* The response is MD5 of decrypted challenge plus session id. */
422: len = BN_num_bytes(challenge);
423: if (len <= 0 || len > sizeof(buf))
424: packet_disconnect("respond_to_rsa_challenge: bad challenge length %d",
425: len);
426:
427: memset(buf, 0, sizeof(buf));
428: BN_bn2bin(challenge, buf + sizeof(buf) - len);
429: MD5_Init(&md);
430: MD5_Update(&md, buf, 32);
431: MD5_Update(&md, session_id, 16);
432: MD5_Final(response, &md);
433:
434: debug("Sending response to host key RSA challenge.");
435:
436: /* Send the response back to the server. */
437: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
438: for (i = 0; i < 16; i++)
439: packet_put_char(response[i]);
440: packet_send();
441: packet_write_wait();
442:
443: memset(buf, 0, sizeof(buf));
444: memset(response, 0, sizeof(response));
445: memset(&md, 0, sizeof(md));
1.1 deraadt 446: }
447:
1.39 deraadt 448: /*
449: * Checks if the user has authentication file, and if so, tries to authenticate
450: * the user using it.
451: */
1.3 provos 452: int
1.43 markus 453: try_rsa_authentication(const char *authfile)
1.1 deraadt 454: {
1.38 markus 455: BIGNUM *challenge;
456: RSA *private_key;
457: RSA *public_key;
458: char *passphrase, *comment;
459: int type, i;
460: int plen, clen;
461:
462: /* Try to load identification for the authentication key. */
463: public_key = RSA_new();
464: if (!load_public_key(authfile, public_key, &comment)) {
465: RSA_free(public_key);
1.43 markus 466: /* Could not load it. Fail. */
467: return 0;
1.38 markus 468: }
469: debug("Trying RSA authentication with key '%.100s'", comment);
470:
471: /* Tell the server that we are willing to authenticate using this key. */
472: packet_start(SSH_CMSG_AUTH_RSA);
473: packet_put_bignum(public_key->n);
474: packet_send();
475: packet_write_wait();
476:
477: /* We no longer need the public key. */
478: RSA_free(public_key);
479:
480: /* Wait for server's response. */
481: type = packet_read(&plen);
482:
1.40 markus 483: /*
484: * The server responds with failure if it doesn\'t like our key or
485: * doesn\'t support RSA authentication.
486: */
1.38 markus 487: if (type == SSH_SMSG_FAILURE) {
488: debug("Server refused our key.");
489: xfree(comment);
1.43 markus 490: return 0;
1.38 markus 491: }
492: /* Otherwise, the server should respond with a challenge. */
493: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
494: packet_disconnect("Protocol error during RSA authentication: %d", type);
495:
496: /* Get the challenge from the packet. */
497: challenge = BN_new();
498: packet_get_bignum(challenge, &clen);
499:
500: packet_integrity_check(plen, clen, type);
501:
502: debug("Received RSA challenge from server.");
503:
504: private_key = RSA_new();
1.40 markus 505: /*
506: * Load the private key. Try first with empty passphrase; if it
507: * fails, ask for a passphrase.
508: */
1.38 markus 509: if (!load_private_key(authfile, "", private_key, NULL)) {
510: char buf[300];
511: snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ",
1.45 deraadt 512: comment);
1.38 markus 513: if (!options.batch_mode)
514: passphrase = read_passphrase(buf, 0);
515: else {
516: debug("Will not query passphrase for %.100s in batch mode.",
517: comment);
518: passphrase = xstrdup("");
519: }
520:
521: /* Load the authentication file using the pasphrase. */
522: if (!load_private_key(authfile, passphrase, private_key, NULL)) {
523: memset(passphrase, 0, strlen(passphrase));
524: xfree(passphrase);
525: error("Bad passphrase.");
526:
527: /* Send a dummy response packet to avoid protocol error. */
528: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
529: for (i = 0; i < 16; i++)
530: packet_put_char(0);
531: packet_send();
532: packet_write_wait();
533:
534: /* Expect the server to reject it... */
535: packet_read_expect(&plen, SSH_SMSG_FAILURE);
536: xfree(comment);
537: return 0;
538: }
539: /* Destroy the passphrase. */
540: memset(passphrase, 0, strlen(passphrase));
541: xfree(passphrase);
542: }
543: /* We no longer need the comment. */
544: xfree(comment);
545:
546: /* Compute and send a response to the challenge. */
547: respond_to_rsa_challenge(challenge, private_key);
548:
549: /* Destroy the private key. */
550: RSA_free(private_key);
551:
552: /* We no longer need the challenge. */
553: BN_clear_free(challenge);
554:
555: /* Wait for response from the server. */
556: type = packet_read(&plen);
557: if (type == SSH_SMSG_SUCCESS) {
558: debug("RSA authentication accepted by server.");
559: return 1;
560: }
561: if (type != SSH_SMSG_FAILURE)
562: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
563: debug("RSA authentication refused.");
564: return 0;
1.1 deraadt 565: }
566:
1.39 deraadt 567: /*
568: * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
569: * authentication and RSA host authentication.
570: */
1.3 provos 571: int
1.38 markus 572: try_rhosts_rsa_authentication(const char *local_user, RSA * host_key)
1.1 deraadt 573: {
1.38 markus 574: int type;
575: BIGNUM *challenge;
576: int plen, clen;
577:
578: debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
579:
580: /* Tell the server that we are willing to authenticate using this key. */
581: packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
582: packet_put_string(local_user, strlen(local_user));
583: packet_put_int(BN_num_bits(host_key->n));
584: packet_put_bignum(host_key->e);
585: packet_put_bignum(host_key->n);
586: packet_send();
587: packet_write_wait();
588:
589: /* Wait for server's response. */
590: type = packet_read(&plen);
591:
592: /* The server responds with failure if it doesn't admit our
593: .rhosts authentication or doesn't know our host key. */
594: if (type == SSH_SMSG_FAILURE) {
595: debug("Server refused our rhosts authentication or host key.");
596: return 0;
597: }
598: /* Otherwise, the server should respond with a challenge. */
599: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
600: packet_disconnect("Protocol error during RSA authentication: %d", type);
601:
602: /* Get the challenge from the packet. */
603: challenge = BN_new();
604: packet_get_bignum(challenge, &clen);
605:
606: packet_integrity_check(plen, clen, type);
607:
608: debug("Received RSA challenge for host key from server.");
609:
610: /* Compute a response to the challenge. */
611: respond_to_rsa_challenge(challenge, host_key);
612:
613: /* We no longer need the challenge. */
614: BN_clear_free(challenge);
615:
616: /* Wait for response from the server. */
617: type = packet_read(&plen);
618: if (type == SSH_SMSG_SUCCESS) {
619: debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
620: return 1;
621: }
622: if (type != SSH_SMSG_FAILURE)
623: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
624: debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
625: return 0;
1.1 deraadt 626: }
627:
628: #ifdef KRB4
1.38 markus 629: int
630: try_kerberos_authentication()
1.1 deraadt 631: {
1.38 markus 632: KTEXT_ST auth; /* Kerberos data */
633: char *reply;
634: char inst[INST_SZ];
635: char *realm;
636: CREDENTIALS cred;
637: int r, type, plen;
1.57 markus 638: socklen_t slen;
1.38 markus 639: Key_schedule schedule;
640: u_long checksum, cksum;
641: MSG_DAT msg_data;
642: struct sockaddr_in local, foreign;
643: struct stat st;
644:
645: /* Don't do anything if we don't have any tickets. */
646: if (stat(tkt_string(), &st) < 0)
647: return 0;
648:
649: strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ);
650:
651: realm = (char *) krb_realmofhost(get_canonical_hostname());
652: if (!realm) {
653: debug("Kerberos V4: no realm for %s", get_canonical_hostname());
654: return 0;
655: }
656: /* This can really be anything. */
657: checksum = (u_long) getpid();
658:
659: r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
660: if (r != KSUCCESS) {
661: debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
662: return 0;
663: }
664: /* Get session key to decrypt the server's reply with. */
665: r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
666: if (r != KSUCCESS) {
667: debug("get_cred failed: %s", krb_err_txt[r]);
668: return 0;
669: }
670: des_key_sched((des_cblock *) cred.session, schedule);
671:
672: /* Send authentication info to server. */
673: packet_start(SSH_CMSG_AUTH_KERBEROS);
674: packet_put_string((char *) auth.dat, auth.length);
675: packet_send();
676: packet_write_wait();
677:
678: /* Zero the buffer. */
679: (void) memset(auth.dat, 0, MAX_KTXT_LEN);
680:
1.57 markus 681: slen = sizeof(local);
1.38 markus 682: memset(&local, 0, sizeof(local));
683: if (getsockname(packet_get_connection_in(),
1.57 markus 684: (struct sockaddr *) & local, &slen) < 0)
1.38 markus 685: debug("getsockname failed: %s", strerror(errno));
686:
1.57 markus 687: slen = sizeof(foreign);
1.38 markus 688: memset(&foreign, 0, sizeof(foreign));
689: if (getpeername(packet_get_connection_in(),
1.57 markus 690: (struct sockaddr *) & foreign, &slen) < 0) {
1.38 markus 691: debug("getpeername failed: %s", strerror(errno));
692: fatal_cleanup();
693: }
694: /* Get server reply. */
695: type = packet_read(&plen);
696: switch (type) {
697: case SSH_SMSG_FAILURE:
698: /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
699: debug("Kerberos V4 authentication failed.");
700: return 0;
701: break;
702:
703: case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
704: /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
705: debug("Kerberos V4 authentication accepted.");
706:
707: /* Get server's response. */
708: reply = packet_get_string((unsigned int *) &auth.length);
709: memcpy(auth.dat, reply, auth.length);
710: xfree(reply);
711:
712: packet_integrity_check(plen, 4 + auth.length, type);
713:
1.40 markus 714: /*
715: * If his response isn't properly encrypted with the session
716: * key, and the decrypted checksum fails to match, he's
717: * bogus. Bail out.
718: */
1.38 markus 719: r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
720: &foreign, &local, &msg_data);
721: if (r != KSUCCESS) {
722: debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
723: packet_disconnect("Kerberos V4 challenge failed!");
724: }
725: /* Fetch the (incremented) checksum that we supplied in the request. */
726: (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum));
727: cksum = ntohl(cksum);
728:
729: /* If it matches, we're golden. */
730: if (cksum == checksum + 1) {
731: debug("Kerberos V4 challenge successful.");
732: return 1;
733: } else
734: packet_disconnect("Kerberos V4 challenge failed!");
735: break;
736:
737: default:
738: packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
739: }
740: return 0;
1.1 deraadt 741: }
1.38 markus 742:
1.1 deraadt 743: #endif /* KRB4 */
744:
745: #ifdef AFS
1.38 markus 746: int
747: send_kerberos_tgt()
1.1 deraadt 748: {
1.38 markus 749: CREDENTIALS *creds;
750: char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
751: int r, type, plen;
1.57 markus 752: char buffer[8192];
1.38 markus 753: struct stat st;
754:
755: /* Don't do anything if we don't have any tickets. */
756: if (stat(tkt_string(), &st) < 0)
757: return 0;
758:
759: creds = xmalloc(sizeof(*creds));
760:
761: if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
762: debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]);
763: return 0;
764: }
765: if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
766: debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
767: return 0;
768: }
769: if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
770: debug("Kerberos V4 ticket expired: %s", TKT_FILE);
771: return 0;
772: }
1.57 markus 773: creds_to_radix(creds, (unsigned char *)buffer);
1.38 markus 774: xfree(creds);
775:
776: packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
1.57 markus 777: packet_put_string(buffer, strlen(buffer));
1.38 markus 778: packet_send();
779: packet_write_wait();
780:
781: type = packet_read(&plen);
1.1 deraadt 782:
1.38 markus 783: if (type == SSH_SMSG_FAILURE)
784: debug("Kerberos TGT for realm %s rejected.", prealm);
785: else if (type != SSH_SMSG_SUCCESS)
786: packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
787:
788: return 1;
1.1 deraadt 789: }
790:
1.38 markus 791: void
792: send_afs_tokens(void)
1.1 deraadt 793: {
1.38 markus 794: CREDENTIALS creds;
795: struct ViceIoctl parms;
796: struct ClearToken ct;
797: int i, type, len, plen;
798: char buf[2048], *p, *server_cell;
1.57 markus 799: char buffer[8192];
1.38 markus 800:
801: /* Move over ktc_GetToken, here's something leaner. */
802: for (i = 0; i < 100; i++) { /* just in case */
803: parms.in = (char *) &i;
804: parms.in_size = sizeof(i);
805: parms.out = buf;
806: parms.out_size = sizeof(buf);
807: if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
808: break;
809: p = buf;
810:
811: /* Get secret token. */
812: memcpy(&creds.ticket_st.length, p, sizeof(unsigned int));
813: if (creds.ticket_st.length > MAX_KTXT_LEN)
814: break;
815: p += sizeof(unsigned int);
816: memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
817: p += creds.ticket_st.length;
818:
819: /* Get clear token. */
820: memcpy(&len, p, sizeof(len));
821: if (len != sizeof(struct ClearToken))
822: break;
823: p += sizeof(len);
824: memcpy(&ct, p, len);
825: p += len;
826: p += sizeof(len); /* primary flag */
827: server_cell = p;
828:
829: /* Flesh out our credentials. */
830: strlcpy(creds.service, "afs", sizeof creds.service);
831: creds.instance[0] = '\0';
832: strlcpy(creds.realm, server_cell, REALM_SZ);
833: memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
834: creds.issue_date = ct.BeginTimestamp;
835: creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
836: creds.kvno = ct.AuthHandle;
837: snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
838: creds.pinst[0] = '\0';
839:
840: /* Encode token, ship it off. */
1.57 markus 841: if (!creds_to_radix(&creds, (unsigned char*) buffer))
1.38 markus 842: break;
843: packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
1.57 markus 844: packet_put_string(buffer, strlen(buffer));
1.38 markus 845: packet_send();
846: packet_write_wait();
847:
848: /* Roger, Roger. Clearance, Clarence. What's your vector,
849: Victor? */
850: type = packet_read(&plen);
851:
852: if (type == SSH_SMSG_FAILURE)
853: debug("AFS token for cell %s rejected.", server_cell);
854: else if (type != SSH_SMSG_SUCCESS)
855: packet_disconnect("Protocol error on AFS token response: %d", type);
856: }
1.1 deraadt 857: }
1.38 markus 858:
1.1 deraadt 859: #endif /* AFS */
860:
1.39 deraadt 861: /*
1.43 markus 862: * Tries to authenticate with any string-based challenge/response system.
863: * Note that the client code is not tied to s/key or TIS.
864: */
865: int
866: try_skey_authentication()
867: {
1.57 markus 868: int type, i;
869: int payload_len;
870: unsigned int clen;
1.43 markus 871: char *challenge, *response;
872:
873: debug("Doing skey authentication.");
874:
875: /* request a challenge */
876: packet_start(SSH_CMSG_AUTH_TIS);
877: packet_send();
878: packet_write_wait();
879:
880: type = packet_read(&payload_len);
881: if (type != SSH_SMSG_FAILURE &&
882: type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
883: packet_disconnect("Protocol error: got %d in response "
884: "to skey-auth", type);
885: }
886: if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
887: debug("No challenge for skey authentication.");
888: return 0;
889: }
1.57 markus 890: challenge = packet_get_string(&clen);
891: packet_integrity_check(payload_len, (4 + clen), type);
1.43 markus 892: if (options.cipher == SSH_CIPHER_NONE)
893: log("WARNING: Encryption is disabled! "
894: "Reponse will be transmitted in clear text.");
895: fprintf(stderr, "%s\n", challenge);
1.54 markus 896: xfree(challenge);
1.43 markus 897: fflush(stderr);
898: for (i = 0; i < options.number_of_password_prompts; i++) {
899: if (i != 0)
900: error("Permission denied, please try again.");
901: response = read_passphrase("Response: ", 0);
902: packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
903: packet_put_string(response, strlen(response));
904: memset(response, 0, strlen(response));
905: xfree(response);
906: packet_send();
907: packet_write_wait();
908: type = packet_read(&payload_len);
909: if (type == SSH_SMSG_SUCCESS)
910: return 1;
911: if (type != SSH_SMSG_FAILURE)
912: packet_disconnect("Protocol error: got %d in response "
913: "to skey-auth-reponse", type);
914: }
915: /* failure */
916: return 0;
917: }
918:
919: /*
920: * Tries to authenticate with plain passwd authentication.
921: */
922: int
923: try_password_authentication(char *prompt)
924: {
925: int type, i, payload_len;
926: char *password;
927:
928: debug("Doing password authentication.");
929: if (options.cipher == SSH_CIPHER_NONE)
930: log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
931: for (i = 0; i < options.number_of_password_prompts; i++) {
932: if (i != 0)
933: error("Permission denied, please try again.");
934: password = read_passphrase(prompt, 0);
935: packet_start(SSH_CMSG_AUTH_PASSWORD);
936: packet_put_string(password, strlen(password));
937: memset(password, 0, strlen(password));
938: xfree(password);
939: packet_send();
940: packet_write_wait();
941:
942: type = packet_read(&payload_len);
943: if (type == SSH_SMSG_SUCCESS)
944: return 1;
945: if (type != SSH_SMSG_FAILURE)
946: packet_disconnect("Protocol error: got %d in response to passwd auth", type);
947: }
948: /* failure */
949: return 0;
950: }
951:
952: /*
1.39 deraadt 953: * Waits for the server identification string, and sends our own
954: * identification string.
955: */
1.38 markus 956: void
957: ssh_exchange_identification()
1.1 deraadt 958: {
1.38 markus 959: char buf[256], remote_version[256]; /* must be same size! */
960: int remote_major, remote_minor, i;
961: int connection_in = packet_get_connection_in();
962: int connection_out = packet_get_connection_out();
963:
964: /* Read other side\'s version identification. */
965: for (i = 0; i < sizeof(buf) - 1; i++) {
1.56 markus 966: int len = read(connection_in, &buf[i], 1);
967: if (len < 0)
1.38 markus 968: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
1.56 markus 969: if (len != 1)
970: fatal("ssh_exchange_identification: Connection closed by remote host");
1.38 markus 971: if (buf[i] == '\r') {
972: buf[i] = '\n';
973: buf[i + 1] = 0;
974: break;
975: }
976: if (buf[i] == '\n') {
977: buf[i + 1] = 0;
978: break;
979: }
980: }
981: buf[sizeof(buf) - 1] = 0;
982:
1.40 markus 983: /*
984: * Check that the versions match. In future this might accept
985: * several versions and set appropriate flags to handle them.
986: */
1.38 markus 987: if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor,
988: remote_version) != 3)
989: fatal("Bad remote protocol version identification: '%.100s'", buf);
990: debug("Remote protocol version %d.%d, remote software version %.100s",
991: remote_major, remote_minor, remote_version);
992:
993: /* Check if the remote protocol version is too old. */
994: if (remote_major == 1 && remote_minor < 3)
995: fatal("Remote machine has too old SSH software version.");
996:
997: /* We speak 1.3, too. */
998: if (remote_major == 1 && remote_minor == 3) {
999: enable_compat13();
1.53 markus 1000: if (options.forward_agent) {
1001: log("Agent forwarding disabled for protocol 1.3");
1.38 markus 1002: options.forward_agent = 0;
1003: }
1004: }
1.1 deraadt 1005: #if 0
1.40 markus 1006: /*
1007: * Removed for now, to permit compatibility with latter versions. The
1008: * server will reject our version and disconnect if it doesn't
1009: * support it.
1010: */
1.38 markus 1011: if (remote_major != PROTOCOL_MAJOR)
1012: fatal("Protocol major versions differ: %d vs. %d",
1013: PROTOCOL_MAJOR, remote_major);
1.1 deraadt 1014: #endif
1015:
1.38 markus 1016: /* Send our own protocol version identification. */
1017: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.45 deraadt 1018: PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
1019: if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 1020: fatal("write: %.100s", strerror(errno));
1.1 deraadt 1021: }
1022:
1023: int ssh_cipher_default = SSH_CIPHER_3DES;
1024:
1.38 markus 1025: int
1026: read_yes_or_no(const char *prompt, int defval)
1.1 deraadt 1027: {
1.38 markus 1028: char buf[1024];
1029: FILE *f;
1030: int retval = -1;
1031:
1032: if (isatty(0))
1033: f = stdin;
1034: else
1035: f = fopen("/dev/tty", "rw");
1036:
1037: if (f == NULL)
1038: return 0;
1039:
1040: fflush(stdout);
1041:
1042: while (1) {
1043: fprintf(stderr, "%s", prompt);
1044: if (fgets(buf, sizeof(buf), f) == NULL) {
1045: /* Print a newline (the prompt probably didn\'t have one). */
1046: fprintf(stderr, "\n");
1047: strlcpy(buf, "no", sizeof buf);
1048: }
1049: /* Remove newline from response. */
1050: if (strchr(buf, '\n'))
1051: *strchr(buf, '\n') = 0;
1052:
1053: if (buf[0] == 0)
1054: retval = defval;
1055: if (strcmp(buf, "yes") == 0)
1056: retval = 1;
1057: if (strcmp(buf, "no") == 0)
1058: retval = 0;
1059:
1060: if (retval != -1) {
1061: if (f != stdin)
1062: fclose(f);
1063: return retval;
1064: }
1.1 deraadt 1065: }
1066: }
1067:
1.39 deraadt 1068: /*
1.46 markus 1069: * check whether the supplied host key is valid, return only if ok.
1.39 deraadt 1070: */
1.46 markus 1071:
1.38 markus 1072: void
1.58 ! markus 1073: check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1.1 deraadt 1074: {
1.58 ! markus 1075: Key *file_key;
1.46 markus 1076: char *ip = NULL;
1.38 markus 1077: char hostline[1000], *hostp;
1078: HostStatus host_status;
1079: HostStatus ip_status;
1.49 markus 1080: int local = 0, host_ip_differ = 0;
1081: char ntop[NI_MAXHOST];
1082:
1083: /*
1084: * Force accepting of the host key for loopback/localhost. The
1085: * problem is that if the home directory is NFS-mounted to multiple
1086: * machines, localhost will refer to a different machine in each of
1087: * them, and the user will get bogus HOST_CHANGED warnings. This
1088: * essentially disables host authentication for localhost; however,
1089: * this is probably not a real problem.
1090: */
1091: switch (hostaddr->sa_family) {
1092: case AF_INET:
1093: local = (ntohl(((struct sockaddr_in *)hostaddr)->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1094: break;
1095: case AF_INET6:
1096: local = IN6_IS_ADDR_LOOPBACK(&(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
1097: break;
1098: default:
1099: local = 0;
1100: break;
1101: }
1102: if (local) {
1103: debug("Forcing accepting of host key for loopback/localhost.");
1104: return;
1105: }
1.42 markus 1106:
1107: /*
1.44 markus 1108: * Turn off check_host_ip for proxy connects, since
1.42 markus 1109: * we don't have the remote ip-address
1110: */
1111: if (options.proxy_command != NULL && options.check_host_ip)
1112: options.check_host_ip = 0;
1.38 markus 1113:
1.49 markus 1114: if (options.check_host_ip) {
1115: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
1116: NULL, 0, NI_NUMERICHOST) != 0)
1117: fatal("check_host_key: getnameinfo failed");
1118: ip = xstrdup(ntop);
1119: }
1.38 markus 1120:
1.46 markus 1121: /*
1122: * Store the host key from the known host file in here so that we can
1123: * compare it with the key for the IP address.
1124: */
1.58 ! markus 1125: file_key = key_new(host_key->type);
1.38 markus 1126:
1.40 markus 1127: /*
1128: * Check if the host key is present in the user\'s list of known
1129: * hosts or in the systemwide list.
1130: */
1.58 ! markus 1131: host_status = check_host_in_hostfile(options.user_hostfile, host, host_key, file_key);
1.38 markus 1132: if (host_status == HOST_NEW)
1.58 ! markus 1133: host_status = check_host_in_hostfile(options.system_hostfile, host, host_key, file_key);
1.40 markus 1134: /*
1135: * Also perform check for the ip address, skip the check if we are
1136: * localhost or the hostname was an ip address to begin with
1137: */
1.38 markus 1138: if (options.check_host_ip && !local && strcmp(host, ip)) {
1.58 ! markus 1139: Key *ip_key = key_new(host_key->type);
! 1140: ip_status = check_host_in_hostfile(options.user_hostfile, ip, host_key, ip_key);
1.38 markus 1141:
1142: if (ip_status == HOST_NEW)
1.58 ! markus 1143: ip_status = check_host_in_hostfile(options.system_hostfile, ip, host_key, ip_key);
1.38 markus 1144: if (host_status == HOST_CHANGED &&
1.58 ! markus 1145: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 1146: host_ip_differ = 1;
1147:
1.58 ! markus 1148: key_free(ip_key);
1.38 markus 1149: } else
1150: ip_status = host_status;
1151:
1.58 ! markus 1152: key_free(file_key);
1.38 markus 1153:
1154: switch (host_status) {
1155: case HOST_OK:
1156: /* The host is known and the key matches. */
1157: debug("Host '%.200s' is known and matches the host key.", host);
1158: if (options.check_host_ip) {
1159: if (ip_status == HOST_NEW) {
1.58 ! markus 1160: if (!add_host_to_hostfile(options.user_hostfile, ip, host_key))
1.38 markus 1161: log("Failed to add the host key for IP address '%.30s' to the list of known hosts (%.30s).",
1162: ip, options.user_hostfile);
1163: else
1164: log("Warning: Permanently added host key for IP address '%.30s' to the list of known hosts.",
1165: ip);
1166: } else if (ip_status != HOST_OK)
1167: log("Warning: the host key for '%.200s' differs from the key for the IP address '%.30s'",
1168: host, ip);
1169: }
1170: break;
1171: case HOST_NEW:
1172: /* The host is new. */
1173: if (options.strict_host_key_checking == 1) {
1174: /* User has requested strict host key checking. We will not add the host key
1175: automatically. The only alternative left is to abort. */
1176: fatal("No host key is known for %.200s and you have requested strict checking.", host);
1177: } else if (options.strict_host_key_checking == 2) {
1178: /* The default */
1179: char prompt[1024];
1.58 ! markus 1180: char *fp = key_fingerprint(host_key);
1.38 markus 1181: snprintf(prompt, sizeof(prompt),
1.45 deraadt 1182: "The authenticity of host '%.200s' can't be established.\n"
1.58 ! markus 1183: "Key fingerprint is %s.\n"
1.45 deraadt 1184: "Are you sure you want to continue connecting (yes/no)? ",
1.58 ! markus 1185: host, fp);
1.38 markus 1186: if (!read_yes_or_no(prompt, -1))
1187: fatal("Aborted by user!\n");
1188: }
1189: if (options.check_host_ip && ip_status == HOST_NEW && strcmp(host, ip)) {
1190: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1191: hostp = hostline;
1192: } else
1193: hostp = host;
1194:
1195: /* If not in strict mode, add the key automatically to the local known_hosts file. */
1.58 ! markus 1196: if (!add_host_to_hostfile(options.user_hostfile, hostp, host_key))
1.38 markus 1197: log("Failed to add the host to the list of known hosts (%.500s).",
1198: options.user_hostfile);
1199: else
1200: log("Warning: Permanently added '%.200s' to the list of known hosts.",
1201: hostp);
1202: break;
1203: case HOST_CHANGED:
1204: if (options.check_host_ip && host_ip_differ) {
1205: char *msg;
1206: if (ip_status == HOST_NEW)
1207: msg = "is unknown";
1208: else if (ip_status == HOST_OK)
1209: msg = "is unchanged";
1210: else
1211: msg = "has a different value";
1212: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1213: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1214: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1215: error("The host key for %s has changed,", host);
1216: error("and the key for the according IP address %s", ip);
1217: error("%s. This could either mean that", msg);
1218: error("DNS SPOOFING is happening or the IP address for the host");
1219: error("and its host key have changed at the same time");
1220: }
1221: /* The host key has changed. */
1222: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.47 markus 1223: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1.38 markus 1224: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1225: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1226: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1227: error("It is also possible that the host key has just been changed.");
1228: error("Please contact your system administrator.");
1229: error("Add correct host key in %.100s to get rid of this message.",
1230: options.user_hostfile);
1231:
1.40 markus 1232: /*
1233: * If strict host key checking is in use, the user will have
1234: * to edit the key manually and we can only abort.
1235: */
1.38 markus 1236: if (options.strict_host_key_checking)
1237: fatal("Host key for %.200s has changed and you have requested strict checking.", host);
1238:
1.40 markus 1239: /*
1240: * If strict host key checking has not been requested, allow
1241: * the connection but without password authentication or
1242: * agent forwarding.
1243: */
1.38 markus 1244: if (options.password_authentication) {
1245: error("Password authentication is disabled to avoid trojan horses.");
1246: options.password_authentication = 0;
1247: }
1248: if (options.forward_agent) {
1249: error("Agent forwarding is disabled to avoid trojan horses.");
1250: options.forward_agent = 0;
1251: }
1.40 markus 1252: /*
1253: * XXX Should permit the user to change to use the new id.
1254: * This could be done by converting the host key to an
1255: * identifying sentence, tell that the host identifies itself
1256: * by that sentence, and ask the user if he/she whishes to
1257: * accept the authentication.
1258: */
1.38 markus 1259: break;
1260: }
1261: if (options.check_host_ip)
1262: xfree(ip);
1.46 markus 1263: }
1.58 ! markus 1264: void
! 1265: check_rsa_host_key(char *host, struct sockaddr *hostaddr, RSA *host_key)
! 1266: {
! 1267: Key k;
! 1268: k.type = KEY_RSA;
! 1269: k.rsa = host_key;
! 1270: check_host_key(host, hostaddr, &k);
! 1271: }
1.46 markus 1272:
1273: /*
1.51 markus 1274: * SSH1 key exchange
1.46 markus 1275: */
1276: void
1.51 markus 1277: ssh_kex(char *host, struct sockaddr *hostaddr)
1.46 markus 1278: {
1.51 markus 1279: int i;
1.46 markus 1280: BIGNUM *key;
1281: RSA *host_key;
1282: RSA *public_key;
1283: int bits, rbits;
1284: unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1.51 markus 1285: unsigned char cookie[8];
1286: unsigned int supported_ciphers;
1.46 markus 1287: unsigned int server_flags, client_flags;
1288: int payload_len, clen, sum_len = 0;
1289: u_int32_t rand = 0;
1290:
1291: debug("Waiting for server public key.");
1292:
1293: /* Wait for a public key packet from the server. */
1294: packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
1295:
1.51 markus 1296: /* Get cookie from the packet. */
1.46 markus 1297: for (i = 0; i < 8; i++)
1.51 markus 1298: cookie[i] = packet_get_char();
1.46 markus 1299:
1300: /* Get the public key. */
1301: public_key = RSA_new();
1302: bits = packet_get_int();/* bits */
1303: public_key->e = BN_new();
1304: packet_get_bignum(public_key->e, &clen);
1305: sum_len += clen;
1306: public_key->n = BN_new();
1307: packet_get_bignum(public_key->n, &clen);
1308: sum_len += clen;
1309:
1310: rbits = BN_num_bits(public_key->n);
1311: if (bits != rbits) {
1312: log("Warning: Server lies about size of server public key: "
1313: "actual size is %d bits vs. announced %d.", rbits, bits);
1314: log("Warning: This may be due to an old implementation of ssh.");
1315: }
1316: /* Get the host key. */
1317: host_key = RSA_new();
1318: bits = packet_get_int();/* bits */
1319: host_key->e = BN_new();
1320: packet_get_bignum(host_key->e, &clen);
1321: sum_len += clen;
1322: host_key->n = BN_new();
1323: packet_get_bignum(host_key->n, &clen);
1324: sum_len += clen;
1325:
1326: rbits = BN_num_bits(host_key->n);
1327: if (bits != rbits) {
1328: log("Warning: Server lies about size of server host key: "
1329: "actual size is %d bits vs. announced %d.", rbits, bits);
1330: log("Warning: This may be due to an old implementation of ssh.");
1331: }
1332:
1333: /* Get protocol flags. */
1334: server_flags = packet_get_int();
1335: packet_set_protocol_flags(server_flags);
1336:
1337: supported_ciphers = packet_get_int();
1338: supported_authentications = packet_get_int();
1339:
1340: debug("Received server public key (%d bits) and host key (%d bits).",
1341: BN_num_bits(public_key->n), BN_num_bits(host_key->n));
1342:
1343: packet_integrity_check(payload_len,
1344: 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
1345: SSH_SMSG_PUBLIC_KEY);
1346:
1.58 ! markus 1347: check_rsa_host_key(host, hostaddr, host_key);
1.46 markus 1348:
1349: client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
1350:
1.51 markus 1351: compute_session_id(session_id, cookie, host_key->n, public_key->n);
1.38 markus 1352:
1353: /* Generate a session key. */
1354: arc4random_stir();
1355:
1.40 markus 1356: /*
1357: * Generate an encryption key for the session. The key is a 256 bit
1358: * random number, interpreted as a 32-byte key, with the least
1359: * significant 8 bits being the first byte of the key.
1360: */
1.38 markus 1361: for (i = 0; i < 32; i++) {
1362: if (i % 4 == 0)
1363: rand = arc4random();
1364: session_key[i] = rand & 0xff;
1365: rand >>= 8;
1366: }
1367:
1.40 markus 1368: /*
1369: * According to the protocol spec, the first byte of the session key
1370: * is the highest byte of the integer. The session key is xored with
1371: * the first 16 bytes of the session id.
1372: */
1.38 markus 1373: key = BN_new();
1374: BN_set_word(key, 0);
1375: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
1376: BN_lshift(key, key, 8);
1377: if (i < 16)
1378: BN_add_word(key, session_key[i] ^ session_id[i]);
1379: else
1380: BN_add_word(key, session_key[i]);
1381: }
1382:
1.40 markus 1383: /*
1384: * Encrypt the integer using the public key and host key of the
1385: * server (key with smaller modulus first).
1386: */
1.38 markus 1387: if (BN_cmp(public_key->n, host_key->n) < 0) {
1388: /* Public key has smaller modulus. */
1389: if (BN_num_bits(host_key->n) <
1390: BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
1391: fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
1392: "SSH_KEY_BITS_RESERVED %d",
1393: BN_num_bits(host_key->n),
1394: BN_num_bits(public_key->n),
1395: SSH_KEY_BITS_RESERVED);
1396: }
1397: rsa_public_encrypt(key, key, public_key);
1398: rsa_public_encrypt(key, key, host_key);
1399: } else {
1400: /* Host key has smaller modulus (or they are equal). */
1401: if (BN_num_bits(public_key->n) <
1402: BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
1403: fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
1404: "SSH_KEY_BITS_RESERVED %d",
1405: BN_num_bits(public_key->n),
1406: BN_num_bits(host_key->n),
1407: SSH_KEY_BITS_RESERVED);
1408: }
1409: rsa_public_encrypt(key, key, host_key);
1410: rsa_public_encrypt(key, key, public_key);
1411: }
1412:
1.52 markus 1413: /* Destroy the public keys since we no longer need them. */
1414: RSA_free(public_key);
1415: RSA_free(host_key);
1416:
1.38 markus 1417: if (options.cipher == SSH_CIPHER_NOT_SET) {
1418: if (cipher_mask() & supported_ciphers & (1 << ssh_cipher_default))
1419: options.cipher = ssh_cipher_default;
1420: else {
1421: debug("Cipher %s not supported, using %.100s instead.",
1422: cipher_name(ssh_cipher_default),
1423: cipher_name(SSH_FALLBACK_CIPHER));
1424: options.cipher = SSH_FALLBACK_CIPHER;
1425: }
1426: }
1427: /* Check that the selected cipher is supported. */
1428: if (!(supported_ciphers & (1 << options.cipher)))
1429: fatal("Selected cipher type %.100s not supported by server.",
1430: cipher_name(options.cipher));
1431:
1432: debug("Encryption type: %.100s", cipher_name(options.cipher));
1433:
1434: /* Send the encrypted session key to the server. */
1435: packet_start(SSH_CMSG_SESSION_KEY);
1436: packet_put_char(options.cipher);
1437:
1.51 markus 1438: /* Send the cookie back to the server. */
1.38 markus 1439: for (i = 0; i < 8; i++)
1.51 markus 1440: packet_put_char(cookie[i]);
1.38 markus 1441:
1.52 markus 1442: /* Send and destroy the encrypted encryption key integer. */
1.38 markus 1443: packet_put_bignum(key);
1.52 markus 1444: BN_clear_free(key);
1.38 markus 1445:
1446: /* Send protocol flags. */
1.46 markus 1447: packet_put_int(client_flags);
1.38 markus 1448:
1449: /* Send the packet now. */
1450: packet_send();
1451: packet_write_wait();
1452:
1453: debug("Sent encrypted session key.");
1454:
1455: /* Set the encryption key. */
1456: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
1457:
1458: /* We will no longer need the session key here. Destroy any extra copies. */
1459: memset(session_key, 0, sizeof(session_key));
1460:
1.40 markus 1461: /*
1462: * Expect a success message from the server. Note that this message
1463: * will be received in encrypted form.
1464: */
1.38 markus 1465: packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
1466:
1467: debug("Received encrypted confirmation.");
1.51 markus 1468: }
1469:
1470: /*
1471: * Authenticate user
1472: */
1473: void
1474: ssh_userauth(int host_key_valid, RSA *own_host_key,
1475: uid_t original_real_uid, char *host)
1476: {
1477: int i, type;
1478: int payload_len;
1479: struct passwd *pw;
1480: const char *server_user, *local_user;
1481:
1482: /* Get local user name. Use it as server user if no user name was given. */
1483: pw = getpwuid(original_real_uid);
1484: if (!pw)
1485: fatal("User id %d not found from user database.", original_real_uid);
1486: local_user = xstrdup(pw->pw_name);
1487: server_user = options.user ? options.user : local_user;
1.38 markus 1488:
1489: /* Send the name of the user to log in as on the server. */
1490: packet_start(SSH_CMSG_USER);
1491: packet_put_string(server_user, strlen(server_user));
1.16 dugsong 1492: packet_send();
1493: packet_write_wait();
1.38 markus 1494:
1.40 markus 1495: /*
1496: * The server should respond with success if no authentication is
1497: * needed (the user has no password). Otherwise the server responds
1498: * with failure.
1499: */
1.16 dugsong 1500: type = packet_read(&payload_len);
1.38 markus 1501:
1502: /* check whether the connection was accepted without authentication. */
1.16 dugsong 1503: if (type == SSH_SMSG_SUCCESS)
1.38 markus 1504: return;
1.16 dugsong 1505: if (type != SSH_SMSG_FAILURE)
1.38 markus 1506: packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
1507: type);
1508:
1509: #ifdef AFS
1510: /* Try Kerberos tgt passing if the server supports it. */
1511: if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
1512: options.kerberos_tgt_passing) {
1513: if (options.cipher == SSH_CIPHER_NONE)
1514: log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
1515: (void) send_kerberos_tgt();
1516: }
1517: /* Try AFS token passing if the server supports it. */
1518: if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
1519: options.afs_token_passing && k_hasafs()) {
1520: if (options.cipher == SSH_CIPHER_NONE)
1521: log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
1522: send_afs_tokens();
1523: }
1524: #endif /* AFS */
1525:
1526: #ifdef KRB4
1527: if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
1528: options.kerberos_authentication) {
1529: debug("Trying Kerberos authentication.");
1530: if (try_kerberos_authentication()) {
1531: /* The server should respond with success or failure. */
1532: type = packet_read(&payload_len);
1533: if (type == SSH_SMSG_SUCCESS)
1534: return;
1535: if (type != SSH_SMSG_FAILURE)
1536: packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
1537: }
1538: }
1539: #endif /* KRB4 */
1540:
1.40 markus 1541: /*
1542: * Use rhosts authentication if running in privileged socket and we
1543: * do not wish to remain anonymous.
1544: */
1.38 markus 1545: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
1546: options.rhosts_authentication) {
1547: debug("Trying rhosts authentication.");
1548: packet_start(SSH_CMSG_AUTH_RHOSTS);
1549: packet_put_string(local_user, strlen(local_user));
1550: packet_send();
1551: packet_write_wait();
1552:
1553: /* The server should respond with success or failure. */
1554: type = packet_read(&payload_len);
1555: if (type == SSH_SMSG_SUCCESS)
1556: return;
1557: if (type != SSH_SMSG_FAILURE)
1558: packet_disconnect("Protocol error: got %d in response to rhosts auth",
1559: type);
1560: }
1.40 markus 1561: /*
1562: * Try .rhosts or /etc/hosts.equiv authentication with RSA host
1563: * authentication.
1564: */
1.38 markus 1565: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
1566: options.rhosts_rsa_authentication && host_key_valid) {
1567: if (try_rhosts_rsa_authentication(local_user, own_host_key))
1568: return;
1569: }
1570: /* Try RSA authentication if the server supports it. */
1571: if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
1572: options.rsa_authentication) {
1.40 markus 1573: /*
1574: * Try RSA authentication using the authentication agent. The
1575: * agent is tried first because no passphrase is needed for
1576: * it, whereas identity files may require passphrases.
1577: */
1.38 markus 1578: if (try_agent_authentication())
1579: return;
1580:
1581: /* Try RSA authentication for each identity. */
1582: for (i = 0; i < options.num_identity_files; i++)
1.43 markus 1583: if (try_rsa_authentication(options.identity_files[i]))
1.38 markus 1584: return;
1585: }
1586: /* Try skey authentication if the server supports it. */
1587: if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
1588: options.skey_authentication && !options.batch_mode) {
1.43 markus 1589: if (try_skey_authentication())
1590: return;
1.38 markus 1591: }
1592: /* Try password authentication if the server supports it. */
1593: if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
1594: options.password_authentication && !options.batch_mode) {
1595: char prompt[80];
1.45 deraadt 1596:
1.43 markus 1597: snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
1.45 deraadt 1598: server_user, host);
1.43 markus 1599: if (try_password_authentication(prompt))
1600: return;
1.38 markus 1601: }
1602: /* All authentication methods have failed. Exit with an error message. */
1603: fatal("Permission denied.");
1604: /* NOTREACHED */
1.51 markus 1605: }
1606: /*
1607: * Starts a dialog with the server, and authenticates the current user on the
1608: * server. This does not need any extra privileges. The basic connection
1609: * to the server must already have been established before this is called.
1610: * If login fails, this function prints an error and never returns.
1611: * This function does not require super-user privileges.
1612: */
1613: void
1614: ssh_login(int host_key_valid, RSA *own_host_key, const char *orighost,
1615: struct sockaddr *hostaddr, uid_t original_real_uid)
1616: {
1617: char *host, *cp;
1618:
1619: /* Convert the user-supplied hostname into all lowercase. */
1620: host = xstrdup(orighost);
1621: for (cp = host; *cp; cp++)
1622: if (isupper(*cp))
1623: *cp = tolower(*cp);
1624:
1625: /* Exchange protocol version identification strings with the server. */
1626: ssh_exchange_identification();
1627:
1628: /* Put the connection into non-blocking mode. */
1629: packet_set_nonblocking();
1630:
1631: supported_authentications = 0;
1632: /* key exchange */
1633: ssh_kex(host, hostaddr);
1634: if (supported_authentications == 0)
1635: fatal("supported_authentications == 0.");
1.58 ! markus 1636:
1.51 markus 1637: /* authenticate user */
1638: ssh_userauth(host_key_valid, own_host_key, original_real_uid, host);
1.1 deraadt 1639: }
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