Annotation of src/usr.bin/ssh/sshconnect1.c, Revision 1.36
1.1 markus 1: /*
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: * Code to connect to a remote host, and to perform the client side of the
6: * login (authentication) dialog.
7: *
1.6 deraadt 8: * As far as I am concerned, the code I have written for this software
9: * can be used freely for any purpose. Any derived versions of this
10: * software must be clearly marked as such, and if the derived work is
11: * incompatible with the protocol description in the RFC file, it must be
12: * called by a name other than "ssh" or "Secure Shell".
1.1 markus 13: */
14:
15: #include "includes.h"
1.36 ! markus 16: RCSID("$OpenBSD: sshconnect1.c,v 1.35 2001/06/23 15:12:21 itojun Exp $");
1.1 markus 17:
18: #include <openssl/bn.h>
19: #include <openssl/evp.h>
20:
1.18 markus 21: #ifdef KRB4
22: #include <krb.h>
23: #endif
24: #ifdef AFS
25: #include <kafs.h>
1.19 markus 26: #include "radix.h"
1.18 markus 27: #endif
28:
29: #include "ssh.h"
30: #include "ssh1.h"
1.1 markus 31: #include "xmalloc.h"
32: #include "rsa.h"
33: #include "buffer.h"
34: #include "packet.h"
35: #include "mpaux.h"
36: #include "uidswap.h"
1.18 markus 37: #include "log.h"
1.1 markus 38: #include "readconf.h"
39: #include "key.h"
1.4 markus 40: #include "authfd.h"
1.1 markus 41: #include "sshconnect.h"
42: #include "authfile.h"
1.18 markus 43: #include "readpass.h"
44: #include "cipher.h"
45: #include "canohost.h"
1.1 markus 46:
47: /* Session id for the current session. */
1.13 markus 48: u_char session_id[16];
49: u_int supported_authentications = 0;
1.1 markus 50:
51: extern Options options;
52: extern char *__progname;
53:
54: /*
55: * Checks if the user has an authentication agent, and if so, tries to
56: * authenticate using the agent.
57: */
1.35 itojun 58: static int
1.24 itojun 59: try_agent_authentication(void)
1.1 markus 60: {
1.5 markus 61: int type;
1.1 markus 62: char *comment;
63: AuthenticationConnection *auth;
1.13 markus 64: u_char response[16];
65: u_int i;
1.5 markus 66: int plen, clen;
67: Key *key;
68: BIGNUM *challenge;
1.1 markus 69:
70: /* Get connection to the agent. */
71: auth = ssh_get_authentication_connection();
72: if (!auth)
73: return 0;
74:
75: challenge = BN_new();
76:
77: /* Loop through identities served by the agent. */
1.5 markus 78: for (key = ssh_get_first_identity(auth, &comment, 1);
79: key != NULL;
80: key = ssh_get_next_identity(auth, &comment, 1)) {
1.1 markus 81:
82: /* Try this identity. */
83: debug("Trying RSA authentication via agent with '%.100s'", comment);
84: xfree(comment);
85:
86: /* Tell the server that we are willing to authenticate using this key. */
87: packet_start(SSH_CMSG_AUTH_RSA);
1.5 markus 88: packet_put_bignum(key->rsa->n);
1.1 markus 89: packet_send();
90: packet_write_wait();
91:
92: /* Wait for server's response. */
93: type = packet_read(&plen);
94:
95: /* The server sends failure if it doesn\'t like our key or
96: does not support RSA authentication. */
97: if (type == SSH_SMSG_FAILURE) {
98: debug("Server refused our key.");
1.5 markus 99: key_free(key);
1.1 markus 100: continue;
101: }
102: /* Otherwise it should have sent a challenge. */
103: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
104: packet_disconnect("Protocol error during RSA authentication: %d",
105: type);
106:
107: packet_get_bignum(challenge, &clen);
108:
109: packet_integrity_check(plen, clen, type);
110:
111: debug("Received RSA challenge from server.");
112:
113: /* Ask the agent to decrypt the challenge. */
1.5 markus 114: if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) {
115: /*
116: * The agent failed to authenticate this identifier
117: * although it advertised it supports this. Just
118: * return a wrong value.
119: */
1.1 markus 120: log("Authentication agent failed to decrypt challenge.");
121: memset(response, 0, sizeof(response));
122: }
1.5 markus 123: key_free(key);
1.1 markus 124: debug("Sending response to RSA challenge.");
125:
126: /* Send the decrypted challenge back to the server. */
127: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
128: for (i = 0; i < 16; i++)
129: packet_put_char(response[i]);
130: packet_send();
131: packet_write_wait();
132:
133: /* Wait for response from the server. */
134: type = packet_read(&plen);
135:
136: /* The server returns success if it accepted the authentication. */
137: if (type == SSH_SMSG_SUCCESS) {
1.14 markus 138: ssh_close_authentication_connection(auth);
1.5 markus 139: BN_clear_free(challenge);
1.1 markus 140: debug("RSA authentication accepted by server.");
141: return 1;
142: }
143: /* Otherwise it should return failure. */
144: if (type != SSH_SMSG_FAILURE)
145: packet_disconnect("Protocol error waiting RSA auth response: %d",
146: type);
147: }
1.14 markus 148: ssh_close_authentication_connection(auth);
1.1 markus 149: BN_clear_free(challenge);
150: debug("RSA authentication using agent refused.");
151: return 0;
152: }
153:
154: /*
155: * Computes the proper response to a RSA challenge, and sends the response to
156: * the server.
157: */
1.35 itojun 158: static void
1.1 markus 159: respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
160: {
1.13 markus 161: u_char buf[32], response[16];
1.1 markus 162: MD5_CTX md;
163: int i, len;
164:
165: /* Decrypt the challenge using the private key. */
1.21 markus 166: /* XXX think about Bleichenbacher, too */
167: if (rsa_private_decrypt(challenge, challenge, prv) <= 0)
168: packet_disconnect(
169: "respond_to_rsa_challenge: rsa_private_decrypt failed");
1.1 markus 170:
171: /* Compute the response. */
172: /* The response is MD5 of decrypted challenge plus session id. */
173: len = BN_num_bytes(challenge);
174: if (len <= 0 || len > sizeof(buf))
1.21 markus 175: packet_disconnect(
176: "respond_to_rsa_challenge: bad challenge length %d", len);
1.1 markus 177:
178: memset(buf, 0, sizeof(buf));
179: BN_bn2bin(challenge, buf + sizeof(buf) - len);
180: MD5_Init(&md);
181: MD5_Update(&md, buf, 32);
182: MD5_Update(&md, session_id, 16);
183: MD5_Final(response, &md);
184:
185: debug("Sending response to host key RSA challenge.");
186:
187: /* Send the response back to the server. */
188: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
189: for (i = 0; i < 16; i++)
190: packet_put_char(response[i]);
191: packet_send();
192: packet_write_wait();
193:
194: memset(buf, 0, sizeof(buf));
195: memset(response, 0, sizeof(response));
196: memset(&md, 0, sizeof(md));
197: }
198:
199: /*
200: * Checks if the user has authentication file, and if so, tries to authenticate
201: * the user using it.
202: */
1.35 itojun 203: static int
1.1 markus 204: try_rsa_authentication(const char *authfile)
205: {
206: BIGNUM *challenge;
1.36 ! markus 207: Key *public, *private;
! 208: char buf[300], *passphrase, *comment;
! 209: int i, type, quit, plen, clen;
1.1 markus 210:
211: /* Try to load identification for the authentication key. */
1.29 markus 212: /* XXKEYLOAD */
213: public = key_load_public_type(KEY_RSA1, authfile, &comment);
214: if (public == NULL) {
1.1 markus 215: /* Could not load it. Fail. */
216: return 0;
217: }
218: debug("Trying RSA authentication with key '%.100s'", comment);
219:
220: /* Tell the server that we are willing to authenticate using this key. */
221: packet_start(SSH_CMSG_AUTH_RSA);
222: packet_put_bignum(public->rsa->n);
223: packet_send();
224: packet_write_wait();
225:
226: /* We no longer need the public key. */
227: key_free(public);
228:
229: /* Wait for server's response. */
230: type = packet_read(&plen);
231:
232: /*
233: * The server responds with failure if it doesn\'t like our key or
234: * doesn\'t support RSA authentication.
235: */
236: if (type == SSH_SMSG_FAILURE) {
237: debug("Server refused our key.");
238: xfree(comment);
239: return 0;
240: }
241: /* Otherwise, the server should respond with a challenge. */
242: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
243: packet_disconnect("Protocol error during RSA authentication: %d", type);
244:
245: /* Get the challenge from the packet. */
246: challenge = BN_new();
247: packet_get_bignum(challenge, &clen);
248:
249: packet_integrity_check(plen, clen, type);
250:
251: debug("Received RSA challenge from server.");
252:
253: /*
254: * Load the private key. Try first with empty passphrase; if it
255: * fails, ask for a passphrase.
256: */
1.29 markus 257: private = key_load_private_type(KEY_RSA1, authfile, "", NULL);
1.36 ! markus 258: if (private == NULL && !options.batch_mode) {
! 259: snprintf(buf, sizeof(buf),
! 260: "Enter passphrase for RSA key '%.100s': ", comment);
! 261: for (i = 0; i < options.number_of_password_prompts; i++) {
1.1 markus 262: passphrase = read_passphrase(buf, 0);
1.36 ! markus 263: if (strcmp(passphrase, "") != 0) {
! 264: private = key_load_private_type(KEY_RSA1,
! 265: authfile, passphrase, NULL);
! 266: quit = 0;
! 267: } else {
! 268: debug2("no passphrase given, try next key");
! 269: quit = 1;
! 270: }
1.1 markus 271: memset(passphrase, 0, strlen(passphrase));
272: xfree(passphrase);
1.36 ! markus 273: if (private != NULL || quit)
! 274: break;
! 275: debug2("bad passphrase given, try again...");
1.1 markus 276: }
277: }
278: /* We no longer need the comment. */
279: xfree(comment);
1.36 ! markus 280:
! 281: if (private == NULL) {
! 282: if (!options.batch_mode)
! 283: error("Bad passphrase.");
! 284:
! 285: /* Send a dummy response packet to avoid protocol error. */
! 286: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
! 287: for (i = 0; i < 16; i++)
! 288: packet_put_char(0);
! 289: packet_send();
! 290: packet_write_wait();
! 291:
! 292: /* Expect the server to reject it... */
! 293: packet_read_expect(&plen, SSH_SMSG_FAILURE);
! 294: BN_clear_free(challenge);
! 295: return 0;
! 296: }
1.1 markus 297:
298: /* Compute and send a response to the challenge. */
299: respond_to_rsa_challenge(challenge, private->rsa);
300:
301: /* Destroy the private key. */
302: key_free(private);
303:
304: /* We no longer need the challenge. */
305: BN_clear_free(challenge);
306:
307: /* Wait for response from the server. */
308: type = packet_read(&plen);
309: if (type == SSH_SMSG_SUCCESS) {
310: debug("RSA authentication accepted by server.");
311: return 1;
312: }
313: if (type != SSH_SMSG_FAILURE)
314: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
315: debug("RSA authentication refused.");
316: return 0;
317: }
318:
319: /*
320: * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
321: * authentication and RSA host authentication.
322: */
1.35 itojun 323: static int
1.29 markus 324: try_rhosts_rsa_authentication(const char *local_user, Key * host_key)
1.1 markus 325: {
326: int type;
327: BIGNUM *challenge;
328: int plen, clen;
329:
330: debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
331:
332: /* Tell the server that we are willing to authenticate using this key. */
333: packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
1.33 markus 334: packet_put_cstring(local_user);
1.29 markus 335: packet_put_int(BN_num_bits(host_key->rsa->n));
336: packet_put_bignum(host_key->rsa->e);
337: packet_put_bignum(host_key->rsa->n);
1.1 markus 338: packet_send();
339: packet_write_wait();
340:
341: /* Wait for server's response. */
342: type = packet_read(&plen);
343:
344: /* The server responds with failure if it doesn't admit our
345: .rhosts authentication or doesn't know our host key. */
346: if (type == SSH_SMSG_FAILURE) {
347: debug("Server refused our rhosts authentication or host key.");
348: return 0;
349: }
350: /* Otherwise, the server should respond with a challenge. */
351: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
352: packet_disconnect("Protocol error during RSA authentication: %d", type);
353:
354: /* Get the challenge from the packet. */
355: challenge = BN_new();
356: packet_get_bignum(challenge, &clen);
357:
358: packet_integrity_check(plen, clen, type);
359:
360: debug("Received RSA challenge for host key from server.");
361:
362: /* Compute a response to the challenge. */
1.29 markus 363: respond_to_rsa_challenge(challenge, host_key->rsa);
1.1 markus 364:
365: /* We no longer need the challenge. */
366: BN_clear_free(challenge);
367:
368: /* Wait for response from the server. */
369: type = packet_read(&plen);
370: if (type == SSH_SMSG_SUCCESS) {
371: debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
372: return 1;
373: }
374: if (type != SSH_SMSG_FAILURE)
375: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
376: debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
377: return 0;
378: }
379:
380: #ifdef KRB4
1.35 itojun 381: static int
1.24 itojun 382: try_kerberos_authentication(void)
1.1 markus 383: {
384: KTEXT_ST auth; /* Kerberos data */
385: char *reply;
386: char inst[INST_SZ];
387: char *realm;
388: CREDENTIALS cred;
389: int r, type, plen;
390: socklen_t slen;
391: Key_schedule schedule;
392: u_long checksum, cksum;
393: MSG_DAT msg_data;
394: struct sockaddr_in local, foreign;
395: struct stat st;
396:
397: /* Don't do anything if we don't have any tickets. */
398: if (stat(tkt_string(), &st) < 0)
399: return 0;
400:
1.22 markus 401: strncpy(inst, (char *) krb_get_phost(get_canonical_hostname(1)), INST_SZ);
1.1 markus 402:
1.22 markus 403: realm = (char *) krb_realmofhost(get_canonical_hostname(1));
1.1 markus 404: if (!realm) {
1.22 markus 405: debug("Kerberos V4: no realm for %s", get_canonical_hostname(1));
1.1 markus 406: return 0;
407: }
408: /* This can really be anything. */
409: checksum = (u_long) getpid();
410:
411: r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
412: if (r != KSUCCESS) {
413: debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
414: return 0;
415: }
416: /* Get session key to decrypt the server's reply with. */
417: r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
418: if (r != KSUCCESS) {
419: debug("get_cred failed: %s", krb_err_txt[r]);
420: return 0;
421: }
422: des_key_sched((des_cblock *) cred.session, schedule);
423:
424: /* Send authentication info to server. */
425: packet_start(SSH_CMSG_AUTH_KERBEROS);
426: packet_put_string((char *) auth.dat, auth.length);
427: packet_send();
428: packet_write_wait();
429:
430: /* Zero the buffer. */
431: (void) memset(auth.dat, 0, MAX_KTXT_LEN);
432:
433: slen = sizeof(local);
434: memset(&local, 0, sizeof(local));
435: if (getsockname(packet_get_connection_in(),
436: (struct sockaddr *) & local, &slen) < 0)
437: debug("getsockname failed: %s", strerror(errno));
438:
439: slen = sizeof(foreign);
440: memset(&foreign, 0, sizeof(foreign));
441: if (getpeername(packet_get_connection_in(),
442: (struct sockaddr *) & foreign, &slen) < 0) {
443: debug("getpeername failed: %s", strerror(errno));
444: fatal_cleanup();
445: }
446: /* Get server reply. */
447: type = packet_read(&plen);
448: switch (type) {
449: case SSH_SMSG_FAILURE:
450: /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
451: debug("Kerberos V4 authentication failed.");
452: return 0;
453: break;
454:
455: case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
456: /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
457: debug("Kerberos V4 authentication accepted.");
458:
459: /* Get server's response. */
1.13 markus 460: reply = packet_get_string((u_int *) &auth.length);
1.1 markus 461: memcpy(auth.dat, reply, auth.length);
462: xfree(reply);
463:
464: packet_integrity_check(plen, 4 + auth.length, type);
465:
466: /*
467: * If his response isn't properly encrypted with the session
468: * key, and the decrypted checksum fails to match, he's
469: * bogus. Bail out.
470: */
471: r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
472: &foreign, &local, &msg_data);
473: if (r != KSUCCESS) {
474: debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
475: packet_disconnect("Kerberos V4 challenge failed!");
476: }
477: /* Fetch the (incremented) checksum that we supplied in the request. */
478: (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum));
479: cksum = ntohl(cksum);
480:
481: /* If it matches, we're golden. */
482: if (cksum == checksum + 1) {
483: debug("Kerberos V4 challenge successful.");
484: return 1;
485: } else
486: packet_disconnect("Kerberos V4 challenge failed!");
487: break;
488:
489: default:
490: packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
491: }
492: return 0;
493: }
494:
495: #endif /* KRB4 */
496:
497: #ifdef AFS
1.35 itojun 498: static int
1.24 itojun 499: send_kerberos_tgt(void)
1.1 markus 500: {
501: CREDENTIALS *creds;
502: char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
503: int r, type, plen;
504: char buffer[8192];
505: struct stat st;
506:
507: /* Don't do anything if we don't have any tickets. */
508: if (stat(tkt_string(), &st) < 0)
509: return 0;
510:
511: creds = xmalloc(sizeof(*creds));
512:
513: if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
514: debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]);
515: return 0;
516: }
517: if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
518: debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
519: return 0;
520: }
521: if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
522: debug("Kerberos V4 ticket expired: %s", TKT_FILE);
523: return 0;
524: }
1.13 markus 525: creds_to_radix(creds, (u_char *)buffer, sizeof buffer);
1.1 markus 526: xfree(creds);
527:
528: packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
1.33 markus 529: packet_put_cstring(buffer);
1.1 markus 530: packet_send();
531: packet_write_wait();
532:
533: type = packet_read(&plen);
534:
535: if (type == SSH_SMSG_FAILURE)
536: debug("Kerberos TGT for realm %s rejected.", prealm);
537: else if (type != SSH_SMSG_SUCCESS)
538: packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
539:
540: return 1;
541: }
542:
1.35 itojun 543: static void
1.1 markus 544: send_afs_tokens(void)
545: {
546: CREDENTIALS creds;
547: struct ViceIoctl parms;
548: struct ClearToken ct;
549: int i, type, len, plen;
550: char buf[2048], *p, *server_cell;
551: char buffer[8192];
552:
553: /* Move over ktc_GetToken, here's something leaner. */
554: for (i = 0; i < 100; i++) { /* just in case */
555: parms.in = (char *) &i;
556: parms.in_size = sizeof(i);
557: parms.out = buf;
558: parms.out_size = sizeof(buf);
559: if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
560: break;
561: p = buf;
562:
563: /* Get secret token. */
1.13 markus 564: memcpy(&creds.ticket_st.length, p, sizeof(u_int));
1.1 markus 565: if (creds.ticket_st.length > MAX_KTXT_LEN)
566: break;
1.13 markus 567: p += sizeof(u_int);
1.1 markus 568: memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
569: p += creds.ticket_st.length;
570:
571: /* Get clear token. */
572: memcpy(&len, p, sizeof(len));
573: if (len != sizeof(struct ClearToken))
574: break;
575: p += sizeof(len);
576: memcpy(&ct, p, len);
577: p += len;
578: p += sizeof(len); /* primary flag */
579: server_cell = p;
580:
581: /* Flesh out our credentials. */
582: strlcpy(creds.service, "afs", sizeof creds.service);
583: creds.instance[0] = '\0';
584: strlcpy(creds.realm, server_cell, REALM_SZ);
585: memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
586: creds.issue_date = ct.BeginTimestamp;
587: creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
588: creds.kvno = ct.AuthHandle;
589: snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
590: creds.pinst[0] = '\0';
591:
592: /* Encode token, ship it off. */
1.15 deraadt 593: if (creds_to_radix(&creds, (u_char *) buffer, sizeof buffer) <= 0)
1.1 markus 594: break;
595: packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
1.33 markus 596: packet_put_cstring(buffer);
1.1 markus 597: packet_send();
598: packet_write_wait();
599:
600: /* Roger, Roger. Clearance, Clarence. What's your vector,
601: Victor? */
602: type = packet_read(&plen);
603:
604: if (type == SSH_SMSG_FAILURE)
605: debug("AFS token for cell %s rejected.", server_cell);
606: else if (type != SSH_SMSG_SUCCESS)
607: packet_disconnect("Protocol error on AFS token response: %d", type);
608: }
609: }
610:
611: #endif /* AFS */
612:
613: /*
614: * Tries to authenticate with any string-based challenge/response system.
615: * Note that the client code is not tied to s/key or TIS.
616: */
1.35 itojun 617: static int
1.32 markus 618: try_challenge_response_authentication(void)
1.1 markus 619: {
620: int type, i;
621: int payload_len;
1.13 markus 622: u_int clen;
1.12 markus 623: char prompt[1024];
1.1 markus 624: char *challenge, *response;
625:
1.20 markus 626: debug("Doing challenge reponse authentication.");
1.1 markus 627:
1.12 markus 628: for (i = 0; i < options.number_of_password_prompts; i++) {
629: /* request a challenge */
630: packet_start(SSH_CMSG_AUTH_TIS);
631: packet_send();
632: packet_write_wait();
1.1 markus 633:
1.12 markus 634: type = packet_read(&payload_len);
635: if (type != SSH_SMSG_FAILURE &&
636: type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
637: packet_disconnect("Protocol error: got %d in response "
1.20 markus 638: "to SSH_CMSG_AUTH_TIS", type);
1.12 markus 639: }
640: if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
1.20 markus 641: debug("No challenge.");
1.12 markus 642: return 0;
643: }
644: challenge = packet_get_string(&clen);
645: packet_integrity_check(payload_len, (4 + clen), type);
1.16 markus 646: snprintf(prompt, sizeof prompt, "%s%s", challenge,
647: strchr(challenge, '\n') ? "" : "\nResponse: ");
1.12 markus 648: xfree(challenge);
1.1 markus 649: if (i != 0)
650: error("Permission denied, please try again.");
1.12 markus 651: if (options.cipher == SSH_CIPHER_NONE)
652: log("WARNING: Encryption is disabled! "
653: "Reponse will be transmitted in clear text.");
654: response = read_passphrase(prompt, 0);
655: if (strcmp(response, "") == 0) {
656: xfree(response);
657: break;
658: }
1.1 markus 659: packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
1.27 markus 660: ssh_put_password(response);
1.1 markus 661: memset(response, 0, strlen(response));
662: xfree(response);
663: packet_send();
664: packet_write_wait();
665: type = packet_read(&payload_len);
666: if (type == SSH_SMSG_SUCCESS)
667: return 1;
668: if (type != SSH_SMSG_FAILURE)
669: packet_disconnect("Protocol error: got %d in response "
1.20 markus 670: "to SSH_CMSG_AUTH_TIS_RESPONSE", type);
1.1 markus 671: }
672: /* failure */
673: return 0;
674: }
675:
676: /*
677: * Tries to authenticate with plain passwd authentication.
678: */
1.35 itojun 679: static int
1.1 markus 680: try_password_authentication(char *prompt)
681: {
682: int type, i, payload_len;
683: char *password;
684:
685: debug("Doing password authentication.");
686: if (options.cipher == SSH_CIPHER_NONE)
687: log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
688: for (i = 0; i < options.number_of_password_prompts; i++) {
689: if (i != 0)
690: error("Permission denied, please try again.");
691: password = read_passphrase(prompt, 0);
692: packet_start(SSH_CMSG_AUTH_PASSWORD);
1.27 markus 693: ssh_put_password(password);
1.1 markus 694: memset(password, 0, strlen(password));
695: xfree(password);
696: packet_send();
697: packet_write_wait();
698:
699: type = packet_read(&payload_len);
700: if (type == SSH_SMSG_SUCCESS)
701: return 1;
702: if (type != SSH_SMSG_FAILURE)
703: packet_disconnect("Protocol error: got %d in response to passwd auth", type);
704: }
705: /* failure */
706: return 0;
707: }
708:
709: /*
710: * SSH1 key exchange
711: */
712: void
713: ssh_kex(char *host, struct sockaddr *hostaddr)
714: {
715: int i;
716: BIGNUM *key;
717: RSA *host_key;
718: RSA *public_key;
719: Key k;
720: int bits, rbits;
721: int ssh_cipher_default = SSH_CIPHER_3DES;
1.13 markus 722: u_char session_key[SSH_SESSION_KEY_LENGTH];
723: u_char cookie[8];
724: u_int supported_ciphers;
725: u_int server_flags, client_flags;
1.1 markus 726: int payload_len, clen, sum_len = 0;
727: u_int32_t rand = 0;
728:
729: debug("Waiting for server public key.");
730:
731: /* Wait for a public key packet from the server. */
732: packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
733:
734: /* Get cookie from the packet. */
735: for (i = 0; i < 8; i++)
736: cookie[i] = packet_get_char();
737:
738: /* Get the public key. */
739: public_key = RSA_new();
740: bits = packet_get_int();/* bits */
741: public_key->e = BN_new();
742: packet_get_bignum(public_key->e, &clen);
743: sum_len += clen;
744: public_key->n = BN_new();
745: packet_get_bignum(public_key->n, &clen);
746: sum_len += clen;
747:
748: rbits = BN_num_bits(public_key->n);
749: if (bits != rbits) {
750: log("Warning: Server lies about size of server public key: "
751: "actual size is %d bits vs. announced %d.", rbits, bits);
752: log("Warning: This may be due to an old implementation of ssh.");
753: }
754: /* Get the host key. */
755: host_key = RSA_new();
756: bits = packet_get_int();/* bits */
757: host_key->e = BN_new();
758: packet_get_bignum(host_key->e, &clen);
759: sum_len += clen;
760: host_key->n = BN_new();
761: packet_get_bignum(host_key->n, &clen);
762: sum_len += clen;
763:
764: rbits = BN_num_bits(host_key->n);
765: if (bits != rbits) {
766: log("Warning: Server lies about size of server host key: "
767: "actual size is %d bits vs. announced %d.", rbits, bits);
768: log("Warning: This may be due to an old implementation of ssh.");
769: }
770:
771: /* Get protocol flags. */
772: server_flags = packet_get_int();
773: packet_set_protocol_flags(server_flags);
774:
775: supported_ciphers = packet_get_int();
776: supported_authentications = packet_get_int();
777:
778: debug("Received server public key (%d bits) and host key (%d bits).",
779: BN_num_bits(public_key->n), BN_num_bits(host_key->n));
780:
781: packet_integrity_check(payload_len,
782: 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
783: SSH_SMSG_PUBLIC_KEY);
1.9 markus 784: k.type = KEY_RSA1;
1.1 markus 785: k.rsa = host_key;
1.34 markus 786: if (verify_host_key(host, hostaddr, &k) == -1)
787: fatal("host_key verification failed");
1.1 markus 788:
789: client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
790:
791: compute_session_id(session_id, cookie, host_key->n, public_key->n);
792:
793: /* Generate a session key. */
794: arc4random_stir();
795:
796: /*
797: * Generate an encryption key for the session. The key is a 256 bit
798: * random number, interpreted as a 32-byte key, with the least
799: * significant 8 bits being the first byte of the key.
800: */
801: for (i = 0; i < 32; i++) {
802: if (i % 4 == 0)
803: rand = arc4random();
804: session_key[i] = rand & 0xff;
805: rand >>= 8;
806: }
807:
808: /*
809: * According to the protocol spec, the first byte of the session key
810: * is the highest byte of the integer. The session key is xored with
811: * the first 16 bytes of the session id.
812: */
813: key = BN_new();
814: BN_set_word(key, 0);
815: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
816: BN_lshift(key, key, 8);
817: if (i < 16)
818: BN_add_word(key, session_key[i] ^ session_id[i]);
819: else
820: BN_add_word(key, session_key[i]);
821: }
822:
823: /*
824: * Encrypt the integer using the public key and host key of the
825: * server (key with smaller modulus first).
826: */
827: if (BN_cmp(public_key->n, host_key->n) < 0) {
828: /* Public key has smaller modulus. */
829: if (BN_num_bits(host_key->n) <
830: BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
831: fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
832: "SSH_KEY_BITS_RESERVED %d",
833: BN_num_bits(host_key->n),
834: BN_num_bits(public_key->n),
835: SSH_KEY_BITS_RESERVED);
836: }
837: rsa_public_encrypt(key, key, public_key);
838: rsa_public_encrypt(key, key, host_key);
839: } else {
840: /* Host key has smaller modulus (or they are equal). */
841: if (BN_num_bits(public_key->n) <
842: BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
843: fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
844: "SSH_KEY_BITS_RESERVED %d",
845: BN_num_bits(public_key->n),
846: BN_num_bits(host_key->n),
847: SSH_KEY_BITS_RESERVED);
848: }
849: rsa_public_encrypt(key, key, host_key);
850: rsa_public_encrypt(key, key, public_key);
851: }
852:
853: /* Destroy the public keys since we no longer need them. */
854: RSA_free(public_key);
855: RSA_free(host_key);
856:
1.11 markus 857: if (options.cipher == SSH_CIPHER_NOT_SET) {
858: if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default))
859: options.cipher = ssh_cipher_default;
860: } else if (options.cipher == SSH_CIPHER_ILLEGAL ||
1.10 markus 861: !(cipher_mask_ssh1(1) & (1 << options.cipher))) {
1.3 markus 862: log("No valid SSH1 cipher, using %.100s instead.",
1.7 markus 863: cipher_name(ssh_cipher_default));
864: options.cipher = ssh_cipher_default;
1.1 markus 865: }
866: /* Check that the selected cipher is supported. */
867: if (!(supported_ciphers & (1 << options.cipher)))
868: fatal("Selected cipher type %.100s not supported by server.",
869: cipher_name(options.cipher));
870:
871: debug("Encryption type: %.100s", cipher_name(options.cipher));
872:
873: /* Send the encrypted session key to the server. */
874: packet_start(SSH_CMSG_SESSION_KEY);
875: packet_put_char(options.cipher);
876:
877: /* Send the cookie back to the server. */
878: for (i = 0; i < 8; i++)
879: packet_put_char(cookie[i]);
880:
881: /* Send and destroy the encrypted encryption key integer. */
882: packet_put_bignum(key);
883: BN_clear_free(key);
884:
885: /* Send protocol flags. */
886: packet_put_int(client_flags);
887:
888: /* Send the packet now. */
889: packet_send();
890: packet_write_wait();
891:
892: debug("Sent encrypted session key.");
893:
894: /* Set the encryption key. */
895: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
896:
897: /* We will no longer need the session key here. Destroy any extra copies. */
898: memset(session_key, 0, sizeof(session_key));
899:
900: /*
901: * Expect a success message from the server. Note that this message
902: * will be received in encrypted form.
903: */
904: packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
905:
906: debug("Received encrypted confirmation.");
907: }
908:
909: /*
910: * Authenticate user
911: */
912: void
1.30 markus 913: ssh_userauth1(const char *local_user, const char *server_user, char *host,
914: Key **keys, int nkeys)
1.1 markus 915: {
916: int i, type;
917: int payload_len;
918:
919: if (supported_authentications == 0)
1.30 markus 920: fatal("ssh_userauth1: server supports no auth methods");
1.1 markus 921:
922: /* Send the name of the user to log in as on the server. */
923: packet_start(SSH_CMSG_USER);
1.33 markus 924: packet_put_cstring(server_user);
1.1 markus 925: packet_send();
926: packet_write_wait();
927:
928: /*
929: * The server should respond with success if no authentication is
930: * needed (the user has no password). Otherwise the server responds
931: * with failure.
932: */
933: type = packet_read(&payload_len);
934:
935: /* check whether the connection was accepted without authentication. */
936: if (type == SSH_SMSG_SUCCESS)
937: return;
938: if (type != SSH_SMSG_FAILURE)
939: packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
940: type);
941:
942: #ifdef AFS
943: /* Try Kerberos tgt passing if the server supports it. */
944: if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
945: options.kerberos_tgt_passing) {
946: if (options.cipher == SSH_CIPHER_NONE)
947: log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
948: (void) send_kerberos_tgt();
949: }
950: /* Try AFS token passing if the server supports it. */
951: if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
952: options.afs_token_passing && k_hasafs()) {
953: if (options.cipher == SSH_CIPHER_NONE)
954: log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
955: send_afs_tokens();
956: }
957: #endif /* AFS */
958:
959: #ifdef KRB4
960: if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
961: options.kerberos_authentication) {
962: debug("Trying Kerberos authentication.");
963: if (try_kerberos_authentication()) {
964: /* The server should respond with success or failure. */
965: type = packet_read(&payload_len);
966: if (type == SSH_SMSG_SUCCESS)
967: return;
968: if (type != SSH_SMSG_FAILURE)
969: packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
970: }
971: }
972: #endif /* KRB4 */
973:
974: /*
975: * Use rhosts authentication if running in privileged socket and we
976: * do not wish to remain anonymous.
977: */
978: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
979: options.rhosts_authentication) {
980: debug("Trying rhosts authentication.");
981: packet_start(SSH_CMSG_AUTH_RHOSTS);
1.33 markus 982: packet_put_cstring(local_user);
1.1 markus 983: packet_send();
984: packet_write_wait();
985:
986: /* The server should respond with success or failure. */
987: type = packet_read(&payload_len);
988: if (type == SSH_SMSG_SUCCESS)
989: return;
990: if (type != SSH_SMSG_FAILURE)
991: packet_disconnect("Protocol error: got %d in response to rhosts auth",
992: type);
993: }
994: /*
995: * Try .rhosts or /etc/hosts.equiv authentication with RSA host
996: * authentication.
997: */
998: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
1.30 markus 999: options.rhosts_rsa_authentication) {
1000: for (i = 0; i < nkeys; i++) {
1.31 markus 1001: if (keys[i] != NULL && keys[i]->type == KEY_RSA1 &&
1.30 markus 1002: try_rhosts_rsa_authentication(local_user, keys[i]))
1003: return;
1004: }
1.1 markus 1005: }
1006: /* Try RSA authentication if the server supports it. */
1007: if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
1008: options.rsa_authentication) {
1009: /*
1010: * Try RSA authentication using the authentication agent. The
1011: * agent is tried first because no passphrase is needed for
1012: * it, whereas identity files may require passphrases.
1013: */
1014: if (try_agent_authentication())
1015: return;
1016:
1017: /* Try RSA authentication for each identity. */
1018: for (i = 0; i < options.num_identity_files; i++)
1.28 markus 1019: if (options.identity_keys[i] != NULL &&
1020: options.identity_keys[i]->type == KEY_RSA1 &&
1.9 markus 1021: try_rsa_authentication(options.identity_files[i]))
1.1 markus 1022: return;
1023: }
1.20 markus 1024: /* Try challenge response authentication if the server supports it. */
1.1 markus 1025: if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
1.32 markus 1026: options.challenge_response_authentication && !options.batch_mode) {
1027: if (try_challenge_response_authentication())
1.1 markus 1028: return;
1029: }
1030: /* Try password authentication if the server supports it. */
1031: if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
1032: options.password_authentication && !options.batch_mode) {
1033: char prompt[80];
1034:
1.23 itojun 1035: snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
1.1 markus 1036: server_user, host);
1037: if (try_password_authentication(prompt))
1038: return;
1039: }
1040: /* All authentication methods have failed. Exit with an error message. */
1041: fatal("Permission denied.");
1042: /* NOTREACHED */
1043: }
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