Annotation of src/usr.bin/ssh/sshconnect1.c, Revision 1.22
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"
1.22 ! markus 16: RCSID("$OpenBSD: sshconnect1.c,v 1.21 2001/01/29 19:47:31 markus 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: */
58: int
59: try_agent_authentication()
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: */
158: void
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: */
203: int
204: try_rsa_authentication(const char *authfile)
205: {
206: BIGNUM *challenge;
207: Key *public;
208: Key *private;
209: char *passphrase, *comment;
210: int type, i;
211: int plen, clen;
212:
213: /* Try to load identification for the authentication key. */
1.9 markus 214: public = key_new(KEY_RSA1);
1.1 markus 215: if (!load_public_key(authfile, public, &comment)) {
216: key_free(public);
217: /* Could not load it. Fail. */
218: return 0;
219: }
220: debug("Trying RSA authentication with key '%.100s'", comment);
221:
222: /* Tell the server that we are willing to authenticate using this key. */
223: packet_start(SSH_CMSG_AUTH_RSA);
224: packet_put_bignum(public->rsa->n);
225: packet_send();
226: packet_write_wait();
227:
228: /* We no longer need the public key. */
229: key_free(public);
230:
231: /* Wait for server's response. */
232: type = packet_read(&plen);
233:
234: /*
235: * The server responds with failure if it doesn\'t like our key or
236: * doesn\'t support RSA authentication.
237: */
238: if (type == SSH_SMSG_FAILURE) {
239: debug("Server refused our key.");
240: xfree(comment);
241: return 0;
242: }
243: /* Otherwise, the server should respond with a challenge. */
244: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
245: packet_disconnect("Protocol error during RSA authentication: %d", type);
246:
247: /* Get the challenge from the packet. */
248: challenge = BN_new();
249: packet_get_bignum(challenge, &clen);
250:
251: packet_integrity_check(plen, clen, type);
252:
253: debug("Received RSA challenge from server.");
254:
1.9 markus 255: private = key_new(KEY_RSA1);
1.1 markus 256: /*
257: * Load the private key. Try first with empty passphrase; if it
258: * fails, ask for a passphrase.
259: */
260: if (!load_private_key(authfile, "", private, NULL)) {
261: char buf[300];
262: snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ",
263: comment);
264: if (!options.batch_mode)
265: passphrase = read_passphrase(buf, 0);
266: else {
267: debug("Will not query passphrase for %.100s in batch mode.",
268: comment);
269: passphrase = xstrdup("");
270: }
271:
272: /* Load the authentication file using the pasphrase. */
273: if (!load_private_key(authfile, passphrase, private, NULL)) {
274: memset(passphrase, 0, strlen(passphrase));
275: xfree(passphrase);
276: error("Bad passphrase.");
277:
278: /* Send a dummy response packet to avoid protocol error. */
279: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
280: for (i = 0; i < 16; i++)
281: packet_put_char(0);
282: packet_send();
283: packet_write_wait();
284:
285: /* Expect the server to reject it... */
286: packet_read_expect(&plen, SSH_SMSG_FAILURE);
287: xfree(comment);
1.14 markus 288: key_free(private);
289: BN_clear_free(challenge);
1.1 markus 290: return 0;
291: }
292: /* Destroy the passphrase. */
293: memset(passphrase, 0, strlen(passphrase));
294: xfree(passphrase);
295: }
296: /* We no longer need the comment. */
297: xfree(comment);
298:
299: /* Compute and send a response to the challenge. */
300: respond_to_rsa_challenge(challenge, private->rsa);
301:
302: /* Destroy the private key. */
303: key_free(private);
304:
305: /* We no longer need the challenge. */
306: BN_clear_free(challenge);
307:
308: /* Wait for response from the server. */
309: type = packet_read(&plen);
310: if (type == SSH_SMSG_SUCCESS) {
311: debug("RSA authentication accepted by server.");
312: return 1;
313: }
314: if (type != SSH_SMSG_FAILURE)
315: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
316: debug("RSA authentication refused.");
317: return 0;
318: }
319:
320: /*
321: * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
322: * authentication and RSA host authentication.
323: */
324: int
325: try_rhosts_rsa_authentication(const char *local_user, RSA * host_key)
326: {
327: int type;
328: BIGNUM *challenge;
329: int plen, clen;
330:
331: debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
332:
333: /* Tell the server that we are willing to authenticate using this key. */
334: packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
335: packet_put_string(local_user, strlen(local_user));
336: packet_put_int(BN_num_bits(host_key->n));
337: packet_put_bignum(host_key->e);
338: packet_put_bignum(host_key->n);
339: packet_send();
340: packet_write_wait();
341:
342: /* Wait for server's response. */
343: type = packet_read(&plen);
344:
345: /* The server responds with failure if it doesn't admit our
346: .rhosts authentication or doesn't know our host key. */
347: if (type == SSH_SMSG_FAILURE) {
348: debug("Server refused our rhosts authentication or host key.");
349: return 0;
350: }
351: /* Otherwise, the server should respond with a challenge. */
352: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
353: packet_disconnect("Protocol error during RSA authentication: %d", type);
354:
355: /* Get the challenge from the packet. */
356: challenge = BN_new();
357: packet_get_bignum(challenge, &clen);
358:
359: packet_integrity_check(plen, clen, type);
360:
361: debug("Received RSA challenge for host key from server.");
362:
363: /* Compute a response to the challenge. */
364: respond_to_rsa_challenge(challenge, host_key);
365:
366: /* We no longer need the challenge. */
367: BN_clear_free(challenge);
368:
369: /* Wait for response from the server. */
370: type = packet_read(&plen);
371: if (type == SSH_SMSG_SUCCESS) {
372: debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
373: return 1;
374: }
375: if (type != SSH_SMSG_FAILURE)
376: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
377: debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
378: return 0;
379: }
380:
381: #ifdef KRB4
382: int
383: try_kerberos_authentication()
384: {
385: KTEXT_ST auth; /* Kerberos data */
386: char *reply;
387: char inst[INST_SZ];
388: char *realm;
389: CREDENTIALS cred;
390: int r, type, plen;
391: socklen_t slen;
392: Key_schedule schedule;
393: u_long checksum, cksum;
394: MSG_DAT msg_data;
395: struct sockaddr_in local, foreign;
396: struct stat st;
397:
398: /* Don't do anything if we don't have any tickets. */
399: if (stat(tkt_string(), &st) < 0)
400: return 0;
401:
1.22 ! markus 402: strncpy(inst, (char *) krb_get_phost(get_canonical_hostname(1)), INST_SZ);
1.1 markus 403:
1.22 ! markus 404: realm = (char *) krb_realmofhost(get_canonical_hostname(1));
1.1 markus 405: if (!realm) {
1.22 ! markus 406: debug("Kerberos V4: no realm for %s", get_canonical_hostname(1));
1.1 markus 407: return 0;
408: }
409: /* This can really be anything. */
410: checksum = (u_long) getpid();
411:
412: r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
413: if (r != KSUCCESS) {
414: debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
415: return 0;
416: }
417: /* Get session key to decrypt the server's reply with. */
418: r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
419: if (r != KSUCCESS) {
420: debug("get_cred failed: %s", krb_err_txt[r]);
421: return 0;
422: }
423: des_key_sched((des_cblock *) cred.session, schedule);
424:
425: /* Send authentication info to server. */
426: packet_start(SSH_CMSG_AUTH_KERBEROS);
427: packet_put_string((char *) auth.dat, auth.length);
428: packet_send();
429: packet_write_wait();
430:
431: /* Zero the buffer. */
432: (void) memset(auth.dat, 0, MAX_KTXT_LEN);
433:
434: slen = sizeof(local);
435: memset(&local, 0, sizeof(local));
436: if (getsockname(packet_get_connection_in(),
437: (struct sockaddr *) & local, &slen) < 0)
438: debug("getsockname failed: %s", strerror(errno));
439:
440: slen = sizeof(foreign);
441: memset(&foreign, 0, sizeof(foreign));
442: if (getpeername(packet_get_connection_in(),
443: (struct sockaddr *) & foreign, &slen) < 0) {
444: debug("getpeername failed: %s", strerror(errno));
445: fatal_cleanup();
446: }
447: /* Get server reply. */
448: type = packet_read(&plen);
449: switch (type) {
450: case SSH_SMSG_FAILURE:
451: /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
452: debug("Kerberos V4 authentication failed.");
453: return 0;
454: break;
455:
456: case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
457: /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
458: debug("Kerberos V4 authentication accepted.");
459:
460: /* Get server's response. */
1.13 markus 461: reply = packet_get_string((u_int *) &auth.length);
1.1 markus 462: memcpy(auth.dat, reply, auth.length);
463: xfree(reply);
464:
465: packet_integrity_check(plen, 4 + auth.length, type);
466:
467: /*
468: * If his response isn't properly encrypted with the session
469: * key, and the decrypted checksum fails to match, he's
470: * bogus. Bail out.
471: */
472: r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
473: &foreign, &local, &msg_data);
474: if (r != KSUCCESS) {
475: debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
476: packet_disconnect("Kerberos V4 challenge failed!");
477: }
478: /* Fetch the (incremented) checksum that we supplied in the request. */
479: (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum));
480: cksum = ntohl(cksum);
481:
482: /* If it matches, we're golden. */
483: if (cksum == checksum + 1) {
484: debug("Kerberos V4 challenge successful.");
485: return 1;
486: } else
487: packet_disconnect("Kerberos V4 challenge failed!");
488: break;
489:
490: default:
491: packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
492: }
493: return 0;
494: }
495:
496: #endif /* KRB4 */
497:
498: #ifdef AFS
499: int
500: send_kerberos_tgt()
501: {
502: CREDENTIALS *creds;
503: char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
504: int r, type, plen;
505: char buffer[8192];
506: struct stat st;
507:
508: /* Don't do anything if we don't have any tickets. */
509: if (stat(tkt_string(), &st) < 0)
510: return 0;
511:
512: creds = xmalloc(sizeof(*creds));
513:
514: if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
515: debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]);
516: return 0;
517: }
518: if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
519: debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
520: return 0;
521: }
522: if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
523: debug("Kerberos V4 ticket expired: %s", TKT_FILE);
524: return 0;
525: }
1.13 markus 526: creds_to_radix(creds, (u_char *)buffer, sizeof buffer);
1.1 markus 527: xfree(creds);
528:
529: packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
530: packet_put_string(buffer, strlen(buffer));
531: packet_send();
532: packet_write_wait();
533:
534: type = packet_read(&plen);
535:
536: if (type == SSH_SMSG_FAILURE)
537: debug("Kerberos TGT for realm %s rejected.", prealm);
538: else if (type != SSH_SMSG_SUCCESS)
539: packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
540:
541: return 1;
542: }
543:
544: void
545: send_afs_tokens(void)
546: {
547: CREDENTIALS creds;
548: struct ViceIoctl parms;
549: struct ClearToken ct;
550: int i, type, len, plen;
551: char buf[2048], *p, *server_cell;
552: char buffer[8192];
553:
554: /* Move over ktc_GetToken, here's something leaner. */
555: for (i = 0; i < 100; i++) { /* just in case */
556: parms.in = (char *) &i;
557: parms.in_size = sizeof(i);
558: parms.out = buf;
559: parms.out_size = sizeof(buf);
560: if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
561: break;
562: p = buf;
563:
564: /* Get secret token. */
1.13 markus 565: memcpy(&creds.ticket_st.length, p, sizeof(u_int));
1.1 markus 566: if (creds.ticket_st.length > MAX_KTXT_LEN)
567: break;
1.13 markus 568: p += sizeof(u_int);
1.1 markus 569: memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
570: p += creds.ticket_st.length;
571:
572: /* Get clear token. */
573: memcpy(&len, p, sizeof(len));
574: if (len != sizeof(struct ClearToken))
575: break;
576: p += sizeof(len);
577: memcpy(&ct, p, len);
578: p += len;
579: p += sizeof(len); /* primary flag */
580: server_cell = p;
581:
582: /* Flesh out our credentials. */
583: strlcpy(creds.service, "afs", sizeof creds.service);
584: creds.instance[0] = '\0';
585: strlcpy(creds.realm, server_cell, REALM_SZ);
586: memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
587: creds.issue_date = ct.BeginTimestamp;
588: creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
589: creds.kvno = ct.AuthHandle;
590: snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
591: creds.pinst[0] = '\0';
592:
593: /* Encode token, ship it off. */
1.15 deraadt 594: if (creds_to_radix(&creds, (u_char *) buffer, sizeof buffer) <= 0)
1.1 markus 595: break;
596: packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
597: packet_put_string(buffer, strlen(buffer));
598: packet_send();
599: packet_write_wait();
600:
601: /* Roger, Roger. Clearance, Clarence. What's your vector,
602: Victor? */
603: type = packet_read(&plen);
604:
605: if (type == SSH_SMSG_FAILURE)
606: debug("AFS token for cell %s rejected.", server_cell);
607: else if (type != SSH_SMSG_SUCCESS)
608: packet_disconnect("Protocol error on AFS token response: %d", type);
609: }
610: }
611:
612: #endif /* AFS */
613:
614: /*
615: * Tries to authenticate with any string-based challenge/response system.
616: * Note that the client code is not tied to s/key or TIS.
617: */
618: int
1.20 markus 619: try_challenge_reponse_authentication()
1.1 markus 620: {
621: int type, i;
622: int payload_len;
1.13 markus 623: u_int clen;
1.12 markus 624: char prompt[1024];
1.1 markus 625: char *challenge, *response;
626:
1.20 markus 627: debug("Doing challenge reponse authentication.");
1.1 markus 628:
1.12 markus 629: for (i = 0; i < options.number_of_password_prompts; i++) {
630: /* request a challenge */
631: packet_start(SSH_CMSG_AUTH_TIS);
632: packet_send();
633: packet_write_wait();
1.1 markus 634:
1.12 markus 635: type = packet_read(&payload_len);
636: if (type != SSH_SMSG_FAILURE &&
637: type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
638: packet_disconnect("Protocol error: got %d in response "
1.20 markus 639: "to SSH_CMSG_AUTH_TIS", type);
1.12 markus 640: }
641: if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
1.20 markus 642: debug("No challenge.");
1.12 markus 643: return 0;
644: }
645: challenge = packet_get_string(&clen);
646: packet_integrity_check(payload_len, (4 + clen), type);
1.16 markus 647: snprintf(prompt, sizeof prompt, "%s%s", challenge,
648: strchr(challenge, '\n') ? "" : "\nResponse: ");
1.12 markus 649: xfree(challenge);
1.1 markus 650: if (i != 0)
651: error("Permission denied, please try again.");
1.12 markus 652: if (options.cipher == SSH_CIPHER_NONE)
653: log("WARNING: Encryption is disabled! "
654: "Reponse will be transmitted in clear text.");
655: response = read_passphrase(prompt, 0);
656: if (strcmp(response, "") == 0) {
657: xfree(response);
658: break;
659: }
1.1 markus 660: packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
661: packet_put_string(response, strlen(response));
662: memset(response, 0, strlen(response));
663: xfree(response);
664: packet_send();
665: packet_write_wait();
666: type = packet_read(&payload_len);
667: if (type == SSH_SMSG_SUCCESS)
668: return 1;
669: if (type != SSH_SMSG_FAILURE)
670: packet_disconnect("Protocol error: got %d in response "
1.20 markus 671: "to SSH_CMSG_AUTH_TIS_RESPONSE", type);
1.1 markus 672: }
673: /* failure */
674: return 0;
675: }
676:
677: /*
678: * Tries to authenticate with plain passwd authentication.
679: */
680: int
681: try_password_authentication(char *prompt)
682: {
683: int type, i, payload_len;
684: char *password;
685:
686: debug("Doing password authentication.");
687: if (options.cipher == SSH_CIPHER_NONE)
688: log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
689: for (i = 0; i < options.number_of_password_prompts; i++) {
690: if (i != 0)
691: error("Permission denied, please try again.");
692: password = read_passphrase(prompt, 0);
693: packet_start(SSH_CMSG_AUTH_PASSWORD);
694: packet_put_string(password, strlen(password));
695: memset(password, 0, strlen(password));
696: xfree(password);
697: packet_send();
698: packet_write_wait();
699:
700: type = packet_read(&payload_len);
701: if (type == SSH_SMSG_SUCCESS)
702: return 1;
703: if (type != SSH_SMSG_FAILURE)
704: packet_disconnect("Protocol error: got %d in response to passwd auth", type);
705: }
706: /* failure */
707: return 0;
708: }
709:
710: /*
711: * SSH1 key exchange
712: */
713: void
714: ssh_kex(char *host, struct sockaddr *hostaddr)
715: {
716: int i;
717: BIGNUM *key;
718: RSA *host_key;
719: RSA *public_key;
720: Key k;
721: int bits, rbits;
722: int ssh_cipher_default = SSH_CIPHER_3DES;
1.13 markus 723: u_char session_key[SSH_SESSION_KEY_LENGTH];
724: u_char cookie[8];
725: u_int supported_ciphers;
726: u_int server_flags, client_flags;
1.1 markus 727: int payload_len, clen, sum_len = 0;
728: u_int32_t rand = 0;
729:
730: debug("Waiting for server public key.");
731:
732: /* Wait for a public key packet from the server. */
733: packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
734:
735: /* Get cookie from the packet. */
736: for (i = 0; i < 8; i++)
737: cookie[i] = packet_get_char();
738:
739: /* Get the public key. */
740: public_key = RSA_new();
741: bits = packet_get_int();/* bits */
742: public_key->e = BN_new();
743: packet_get_bignum(public_key->e, &clen);
744: sum_len += clen;
745: public_key->n = BN_new();
746: packet_get_bignum(public_key->n, &clen);
747: sum_len += clen;
748:
749: rbits = BN_num_bits(public_key->n);
750: if (bits != rbits) {
751: log("Warning: Server lies about size of server public key: "
752: "actual size is %d bits vs. announced %d.", rbits, bits);
753: log("Warning: This may be due to an old implementation of ssh.");
754: }
755: /* Get the host key. */
756: host_key = RSA_new();
757: bits = packet_get_int();/* bits */
758: host_key->e = BN_new();
759: packet_get_bignum(host_key->e, &clen);
760: sum_len += clen;
761: host_key->n = BN_new();
762: packet_get_bignum(host_key->n, &clen);
763: sum_len += clen;
764:
765: rbits = BN_num_bits(host_key->n);
766: if (bits != rbits) {
767: log("Warning: Server lies about size of server host key: "
768: "actual size is %d bits vs. announced %d.", rbits, bits);
769: log("Warning: This may be due to an old implementation of ssh.");
770: }
771:
772: /* Get protocol flags. */
773: server_flags = packet_get_int();
774: packet_set_protocol_flags(server_flags);
775:
776: supported_ciphers = packet_get_int();
777: supported_authentications = packet_get_int();
778:
779: debug("Received server public key (%d bits) and host key (%d bits).",
780: BN_num_bits(public_key->n), BN_num_bits(host_key->n));
781:
782: packet_integrity_check(payload_len,
783: 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
784: SSH_SMSG_PUBLIC_KEY);
1.9 markus 785: k.type = KEY_RSA1;
1.1 markus 786: k.rsa = host_key;
787: check_host_key(host, hostaddr, &k,
788: options.user_hostfile, options.system_hostfile);
789:
790: client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
791:
792: compute_session_id(session_id, cookie, host_key->n, public_key->n);
793:
794: /* Generate a session key. */
795: arc4random_stir();
796:
797: /*
798: * Generate an encryption key for the session. The key is a 256 bit
799: * random number, interpreted as a 32-byte key, with the least
800: * significant 8 bits being the first byte of the key.
801: */
802: for (i = 0; i < 32; i++) {
803: if (i % 4 == 0)
804: rand = arc4random();
805: session_key[i] = rand & 0xff;
806: rand >>= 8;
807: }
808:
809: /*
810: * According to the protocol spec, the first byte of the session key
811: * is the highest byte of the integer. The session key is xored with
812: * the first 16 bytes of the session id.
813: */
814: key = BN_new();
815: BN_set_word(key, 0);
816: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
817: BN_lshift(key, key, 8);
818: if (i < 16)
819: BN_add_word(key, session_key[i] ^ session_id[i]);
820: else
821: BN_add_word(key, session_key[i]);
822: }
823:
824: /*
825: * Encrypt the integer using the public key and host key of the
826: * server (key with smaller modulus first).
827: */
828: if (BN_cmp(public_key->n, host_key->n) < 0) {
829: /* Public key has smaller modulus. */
830: if (BN_num_bits(host_key->n) <
831: BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
832: fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
833: "SSH_KEY_BITS_RESERVED %d",
834: BN_num_bits(host_key->n),
835: BN_num_bits(public_key->n),
836: SSH_KEY_BITS_RESERVED);
837: }
838: rsa_public_encrypt(key, key, public_key);
839: rsa_public_encrypt(key, key, host_key);
840: } else {
841: /* Host key has smaller modulus (or they are equal). */
842: if (BN_num_bits(public_key->n) <
843: BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
844: fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
845: "SSH_KEY_BITS_RESERVED %d",
846: BN_num_bits(public_key->n),
847: BN_num_bits(host_key->n),
848: SSH_KEY_BITS_RESERVED);
849: }
850: rsa_public_encrypt(key, key, host_key);
851: rsa_public_encrypt(key, key, public_key);
852: }
853:
854: /* Destroy the public keys since we no longer need them. */
855: RSA_free(public_key);
856: RSA_free(host_key);
857:
1.11 markus 858: if (options.cipher == SSH_CIPHER_NOT_SET) {
859: if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default))
860: options.cipher = ssh_cipher_default;
861: } else if (options.cipher == SSH_CIPHER_ILLEGAL ||
1.10 markus 862: !(cipher_mask_ssh1(1) & (1 << options.cipher))) {
1.3 markus 863: log("No valid SSH1 cipher, using %.100s instead.",
1.7 markus 864: cipher_name(ssh_cipher_default));
865: options.cipher = ssh_cipher_default;
1.1 markus 866: }
867: /* Check that the selected cipher is supported. */
868: if (!(supported_ciphers & (1 << options.cipher)))
869: fatal("Selected cipher type %.100s not supported by server.",
870: cipher_name(options.cipher));
871:
872: debug("Encryption type: %.100s", cipher_name(options.cipher));
873:
874: /* Send the encrypted session key to the server. */
875: packet_start(SSH_CMSG_SESSION_KEY);
876: packet_put_char(options.cipher);
877:
878: /* Send the cookie back to the server. */
879: for (i = 0; i < 8; i++)
880: packet_put_char(cookie[i]);
881:
882: /* Send and destroy the encrypted encryption key integer. */
883: packet_put_bignum(key);
884: BN_clear_free(key);
885:
886: /* Send protocol flags. */
887: packet_put_int(client_flags);
888:
889: /* Send the packet now. */
890: packet_send();
891: packet_write_wait();
892:
893: debug("Sent encrypted session key.");
894:
895: /* Set the encryption key. */
896: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
897:
898: /* We will no longer need the session key here. Destroy any extra copies. */
899: memset(session_key, 0, sizeof(session_key));
900:
901: /*
902: * Expect a success message from the server. Note that this message
903: * will be received in encrypted form.
904: */
905: packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
906:
907: debug("Received encrypted confirmation.");
908: }
909:
910: /*
911: * Authenticate user
912: */
913: void
914: ssh_userauth(
1.15 deraadt 915: const char *local_user,
916: const char *server_user,
1.1 markus 917: char *host,
918: int host_key_valid, RSA *own_host_key)
919: {
920: int i, type;
921: int payload_len;
922:
923: if (supported_authentications == 0)
924: fatal("ssh_userauth: server supports no auth methods");
925:
926: /* Send the name of the user to log in as on the server. */
927: packet_start(SSH_CMSG_USER);
928: packet_put_string(server_user, strlen(server_user));
929: packet_send();
930: packet_write_wait();
931:
932: /*
933: * The server should respond with success if no authentication is
934: * needed (the user has no password). Otherwise the server responds
935: * with failure.
936: */
937: type = packet_read(&payload_len);
938:
939: /* check whether the connection was accepted without authentication. */
940: if (type == SSH_SMSG_SUCCESS)
941: return;
942: if (type != SSH_SMSG_FAILURE)
943: packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
944: type);
945:
946: #ifdef AFS
947: /* Try Kerberos tgt passing if the server supports it. */
948: if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
949: options.kerberos_tgt_passing) {
950: if (options.cipher == SSH_CIPHER_NONE)
951: log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
952: (void) send_kerberos_tgt();
953: }
954: /* Try AFS token passing if the server supports it. */
955: if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
956: options.afs_token_passing && k_hasafs()) {
957: if (options.cipher == SSH_CIPHER_NONE)
958: log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
959: send_afs_tokens();
960: }
961: #endif /* AFS */
962:
963: #ifdef KRB4
964: if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
965: options.kerberos_authentication) {
966: debug("Trying Kerberos authentication.");
967: if (try_kerberos_authentication()) {
968: /* The server should respond with success or failure. */
969: type = packet_read(&payload_len);
970: if (type == SSH_SMSG_SUCCESS)
971: return;
972: if (type != SSH_SMSG_FAILURE)
973: packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
974: }
975: }
976: #endif /* KRB4 */
977:
978: /*
979: * Use rhosts authentication if running in privileged socket and we
980: * do not wish to remain anonymous.
981: */
982: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
983: options.rhosts_authentication) {
984: debug("Trying rhosts authentication.");
985: packet_start(SSH_CMSG_AUTH_RHOSTS);
986: packet_put_string(local_user, strlen(local_user));
987: packet_send();
988: packet_write_wait();
989:
990: /* The server should respond with success or failure. */
991: type = packet_read(&payload_len);
992: if (type == SSH_SMSG_SUCCESS)
993: return;
994: if (type != SSH_SMSG_FAILURE)
995: packet_disconnect("Protocol error: got %d in response to rhosts auth",
996: type);
997: }
998: /*
999: * Try .rhosts or /etc/hosts.equiv authentication with RSA host
1000: * authentication.
1001: */
1002: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
1003: options.rhosts_rsa_authentication && host_key_valid) {
1004: if (try_rhosts_rsa_authentication(local_user, own_host_key))
1005: return;
1006: }
1007: /* Try RSA authentication if the server supports it. */
1008: if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
1009: options.rsa_authentication) {
1010: /*
1011: * Try RSA authentication using the authentication agent. The
1012: * agent is tried first because no passphrase is needed for
1013: * it, whereas identity files may require passphrases.
1014: */
1015: if (try_agent_authentication())
1016: return;
1017:
1018: /* Try RSA authentication for each identity. */
1019: for (i = 0; i < options.num_identity_files; i++)
1.9 markus 1020: if (options.identity_files_type[i] == KEY_RSA1 &&
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)) &&
1.20 markus 1026: options.challenge_reponse_authentication && !options.batch_mode) {
1027: if (try_challenge_reponse_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:
1035: snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
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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