Annotation of src/usr.bin/ssh/sshconnect1.c, Revision 1.18
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"
1.18 ! markus 16: RCSID("$OpenBSD: sshconnect1.c,v 1.17 2001/01/19 15:55:12 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: #include "radix.h"
! 24: #endif
! 25: #ifdef AFS
! 26: #include <kafs.h>
! 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. */
166: rsa_private_decrypt(challenge, challenge, prv);
167:
168: /* Compute the response. */
169: /* The response is MD5 of decrypted challenge plus session id. */
170: len = BN_num_bytes(challenge);
171: if (len <= 0 || len > sizeof(buf))
172: packet_disconnect("respond_to_rsa_challenge: bad challenge length %d",
173: len);
174:
175: memset(buf, 0, sizeof(buf));
176: BN_bn2bin(challenge, buf + sizeof(buf) - len);
177: MD5_Init(&md);
178: MD5_Update(&md, buf, 32);
179: MD5_Update(&md, session_id, 16);
180: MD5_Final(response, &md);
181:
182: debug("Sending response to host key RSA challenge.");
183:
184: /* Send the response back to the server. */
185: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
186: for (i = 0; i < 16; i++)
187: packet_put_char(response[i]);
188: packet_send();
189: packet_write_wait();
190:
191: memset(buf, 0, sizeof(buf));
192: memset(response, 0, sizeof(response));
193: memset(&md, 0, sizeof(md));
194: }
195:
196: /*
197: * Checks if the user has authentication file, and if so, tries to authenticate
198: * the user using it.
199: */
200: int
201: try_rsa_authentication(const char *authfile)
202: {
203: BIGNUM *challenge;
204: Key *public;
205: Key *private;
206: char *passphrase, *comment;
207: int type, i;
208: int plen, clen;
209:
210: /* Try to load identification for the authentication key. */
1.9 markus 211: public = key_new(KEY_RSA1);
1.1 markus 212: if (!load_public_key(authfile, public, &comment)) {
213: key_free(public);
214: /* Could not load it. Fail. */
215: return 0;
216: }
217: debug("Trying RSA authentication with key '%.100s'", comment);
218:
219: /* Tell the server that we are willing to authenticate using this key. */
220: packet_start(SSH_CMSG_AUTH_RSA);
221: packet_put_bignum(public->rsa->n);
222: packet_send();
223: packet_write_wait();
224:
225: /* We no longer need the public key. */
226: key_free(public);
227:
228: /* Wait for server's response. */
229: type = packet_read(&plen);
230:
231: /*
232: * The server responds with failure if it doesn\'t like our key or
233: * doesn\'t support RSA authentication.
234: */
235: if (type == SSH_SMSG_FAILURE) {
236: debug("Server refused our key.");
237: xfree(comment);
238: return 0;
239: }
240: /* Otherwise, the server should respond with a challenge. */
241: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
242: packet_disconnect("Protocol error during RSA authentication: %d", type);
243:
244: /* Get the challenge from the packet. */
245: challenge = BN_new();
246: packet_get_bignum(challenge, &clen);
247:
248: packet_integrity_check(plen, clen, type);
249:
250: debug("Received RSA challenge from server.");
251:
1.9 markus 252: private = key_new(KEY_RSA1);
1.1 markus 253: /*
254: * Load the private key. Try first with empty passphrase; if it
255: * fails, ask for a passphrase.
256: */
257: if (!load_private_key(authfile, "", private, NULL)) {
258: char buf[300];
259: snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ",
260: comment);
261: if (!options.batch_mode)
262: passphrase = read_passphrase(buf, 0);
263: else {
264: debug("Will not query passphrase for %.100s in batch mode.",
265: comment);
266: passphrase = xstrdup("");
267: }
268:
269: /* Load the authentication file using the pasphrase. */
270: if (!load_private_key(authfile, passphrase, private, NULL)) {
271: memset(passphrase, 0, strlen(passphrase));
272: xfree(passphrase);
273: error("Bad passphrase.");
274:
275: /* Send a dummy response packet to avoid protocol error. */
276: packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
277: for (i = 0; i < 16; i++)
278: packet_put_char(0);
279: packet_send();
280: packet_write_wait();
281:
282: /* Expect the server to reject it... */
283: packet_read_expect(&plen, SSH_SMSG_FAILURE);
284: xfree(comment);
1.14 markus 285: key_free(private);
286: BN_clear_free(challenge);
1.1 markus 287: return 0;
288: }
289: /* Destroy the passphrase. */
290: memset(passphrase, 0, strlen(passphrase));
291: xfree(passphrase);
292: }
293: /* We no longer need the comment. */
294: xfree(comment);
295:
296: /* Compute and send a response to the challenge. */
297: respond_to_rsa_challenge(challenge, private->rsa);
298:
299: /* Destroy the private key. */
300: key_free(private);
301:
302: /* We no longer need the challenge. */
303: BN_clear_free(challenge);
304:
305: /* Wait for response from the server. */
306: type = packet_read(&plen);
307: if (type == SSH_SMSG_SUCCESS) {
308: debug("RSA authentication accepted by server.");
309: return 1;
310: }
311: if (type != SSH_SMSG_FAILURE)
312: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
313: debug("RSA authentication refused.");
314: return 0;
315: }
316:
317: /*
318: * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
319: * authentication and RSA host authentication.
320: */
321: int
322: try_rhosts_rsa_authentication(const char *local_user, RSA * host_key)
323: {
324: int type;
325: BIGNUM *challenge;
326: int plen, clen;
327:
328: debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
329:
330: /* Tell the server that we are willing to authenticate using this key. */
331: packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
332: packet_put_string(local_user, strlen(local_user));
333: packet_put_int(BN_num_bits(host_key->n));
334: packet_put_bignum(host_key->e);
335: packet_put_bignum(host_key->n);
336: packet_send();
337: packet_write_wait();
338:
339: /* Wait for server's response. */
340: type = packet_read(&plen);
341:
342: /* The server responds with failure if it doesn't admit our
343: .rhosts authentication or doesn't know our host key. */
344: if (type == SSH_SMSG_FAILURE) {
345: debug("Server refused our rhosts authentication or host key.");
346: return 0;
347: }
348: /* Otherwise, the server should respond with a challenge. */
349: if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
350: packet_disconnect("Protocol error during RSA authentication: %d", type);
351:
352: /* Get the challenge from the packet. */
353: challenge = BN_new();
354: packet_get_bignum(challenge, &clen);
355:
356: packet_integrity_check(plen, clen, type);
357:
358: debug("Received RSA challenge for host key from server.");
359:
360: /* Compute a response to the challenge. */
361: respond_to_rsa_challenge(challenge, host_key);
362:
363: /* We no longer need the challenge. */
364: BN_clear_free(challenge);
365:
366: /* Wait for response from the server. */
367: type = packet_read(&plen);
368: if (type == SSH_SMSG_SUCCESS) {
369: debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
370: return 1;
371: }
372: if (type != SSH_SMSG_FAILURE)
373: packet_disconnect("Protocol error waiting RSA auth response: %d", type);
374: debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
375: return 0;
376: }
377:
378: #ifdef KRB4
379: int
380: try_kerberos_authentication()
381: {
382: KTEXT_ST auth; /* Kerberos data */
383: char *reply;
384: char inst[INST_SZ];
385: char *realm;
386: CREDENTIALS cred;
387: int r, type, plen;
388: socklen_t slen;
389: Key_schedule schedule;
390: u_long checksum, cksum;
391: MSG_DAT msg_data;
392: struct sockaddr_in local, foreign;
393: struct stat st;
394:
395: /* Don't do anything if we don't have any tickets. */
396: if (stat(tkt_string(), &st) < 0)
397: return 0;
398:
399: strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ);
400:
401: realm = (char *) krb_realmofhost(get_canonical_hostname());
402: if (!realm) {
403: debug("Kerberos V4: no realm for %s", get_canonical_hostname());
404: return 0;
405: }
406: /* This can really be anything. */
407: checksum = (u_long) getpid();
408:
409: r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
410: if (r != KSUCCESS) {
411: debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
412: return 0;
413: }
414: /* Get session key to decrypt the server's reply with. */
415: r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
416: if (r != KSUCCESS) {
417: debug("get_cred failed: %s", krb_err_txt[r]);
418: return 0;
419: }
420: des_key_sched((des_cblock *) cred.session, schedule);
421:
422: /* Send authentication info to server. */
423: packet_start(SSH_CMSG_AUTH_KERBEROS);
424: packet_put_string((char *) auth.dat, auth.length);
425: packet_send();
426: packet_write_wait();
427:
428: /* Zero the buffer. */
429: (void) memset(auth.dat, 0, MAX_KTXT_LEN);
430:
431: slen = sizeof(local);
432: memset(&local, 0, sizeof(local));
433: if (getsockname(packet_get_connection_in(),
434: (struct sockaddr *) & local, &slen) < 0)
435: debug("getsockname failed: %s", strerror(errno));
436:
437: slen = sizeof(foreign);
438: memset(&foreign, 0, sizeof(foreign));
439: if (getpeername(packet_get_connection_in(),
440: (struct sockaddr *) & foreign, &slen) < 0) {
441: debug("getpeername failed: %s", strerror(errno));
442: fatal_cleanup();
443: }
444: /* Get server reply. */
445: type = packet_read(&plen);
446: switch (type) {
447: case SSH_SMSG_FAILURE:
448: /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
449: debug("Kerberos V4 authentication failed.");
450: return 0;
451: break;
452:
453: case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
454: /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
455: debug("Kerberos V4 authentication accepted.");
456:
457: /* Get server's response. */
1.13 markus 458: reply = packet_get_string((u_int *) &auth.length);
1.1 markus 459: memcpy(auth.dat, reply, auth.length);
460: xfree(reply);
461:
462: packet_integrity_check(plen, 4 + auth.length, type);
463:
464: /*
465: * If his response isn't properly encrypted with the session
466: * key, and the decrypted checksum fails to match, he's
467: * bogus. Bail out.
468: */
469: r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
470: &foreign, &local, &msg_data);
471: if (r != KSUCCESS) {
472: debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
473: packet_disconnect("Kerberos V4 challenge failed!");
474: }
475: /* Fetch the (incremented) checksum that we supplied in the request. */
476: (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum));
477: cksum = ntohl(cksum);
478:
479: /* If it matches, we're golden. */
480: if (cksum == checksum + 1) {
481: debug("Kerberos V4 challenge successful.");
482: return 1;
483: } else
484: packet_disconnect("Kerberos V4 challenge failed!");
485: break;
486:
487: default:
488: packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
489: }
490: return 0;
491: }
492:
493: #endif /* KRB4 */
494:
495: #ifdef AFS
496: int
497: send_kerberos_tgt()
498: {
499: CREDENTIALS *creds;
500: char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
501: int r, type, plen;
502: char buffer[8192];
503: struct stat st;
504:
505: /* Don't do anything if we don't have any tickets. */
506: if (stat(tkt_string(), &st) < 0)
507: return 0;
508:
509: creds = xmalloc(sizeof(*creds));
510:
511: if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
512: debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]);
513: return 0;
514: }
515: if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
516: debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
517: return 0;
518: }
519: if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
520: debug("Kerberos V4 ticket expired: %s", TKT_FILE);
521: return 0;
522: }
1.13 markus 523: creds_to_radix(creds, (u_char *)buffer, sizeof buffer);
1.1 markus 524: xfree(creds);
525:
526: packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
527: packet_put_string(buffer, strlen(buffer));
528: packet_send();
529: packet_write_wait();
530:
531: type = packet_read(&plen);
532:
533: if (type == SSH_SMSG_FAILURE)
534: debug("Kerberos TGT for realm %s rejected.", prealm);
535: else if (type != SSH_SMSG_SUCCESS)
536: packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
537:
538: return 1;
539: }
540:
541: void
542: send_afs_tokens(void)
543: {
544: CREDENTIALS creds;
545: struct ViceIoctl parms;
546: struct ClearToken ct;
547: int i, type, len, plen;
548: char buf[2048], *p, *server_cell;
549: char buffer[8192];
550:
551: /* Move over ktc_GetToken, here's something leaner. */
552: for (i = 0; i < 100; i++) { /* just in case */
553: parms.in = (char *) &i;
554: parms.in_size = sizeof(i);
555: parms.out = buf;
556: parms.out_size = sizeof(buf);
557: if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
558: break;
559: p = buf;
560:
561: /* Get secret token. */
1.13 markus 562: memcpy(&creds.ticket_st.length, p, sizeof(u_int));
1.1 markus 563: if (creds.ticket_st.length > MAX_KTXT_LEN)
564: break;
1.13 markus 565: p += sizeof(u_int);
1.1 markus 566: memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
567: p += creds.ticket_st.length;
568:
569: /* Get clear token. */
570: memcpy(&len, p, sizeof(len));
571: if (len != sizeof(struct ClearToken))
572: break;
573: p += sizeof(len);
574: memcpy(&ct, p, len);
575: p += len;
576: p += sizeof(len); /* primary flag */
577: server_cell = p;
578:
579: /* Flesh out our credentials. */
580: strlcpy(creds.service, "afs", sizeof creds.service);
581: creds.instance[0] = '\0';
582: strlcpy(creds.realm, server_cell, REALM_SZ);
583: memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
584: creds.issue_date = ct.BeginTimestamp;
585: creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
586: creds.kvno = ct.AuthHandle;
587: snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
588: creds.pinst[0] = '\0';
589:
590: /* Encode token, ship it off. */
1.15 deraadt 591: if (creds_to_radix(&creds, (u_char *) buffer, sizeof buffer) <= 0)
1.1 markus 592: break;
593: packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
594: packet_put_string(buffer, strlen(buffer));
595: packet_send();
596: packet_write_wait();
597:
598: /* Roger, Roger. Clearance, Clarence. What's your vector,
599: Victor? */
600: type = packet_read(&plen);
601:
602: if (type == SSH_SMSG_FAILURE)
603: debug("AFS token for cell %s rejected.", server_cell);
604: else if (type != SSH_SMSG_SUCCESS)
605: packet_disconnect("Protocol error on AFS token response: %d", type);
606: }
607: }
608:
609: #endif /* AFS */
610:
611: /*
612: * Tries to authenticate with any string-based challenge/response system.
613: * Note that the client code is not tied to s/key or TIS.
614: */
615: int
616: try_skey_authentication()
617: {
618: int type, i;
619: int payload_len;
1.13 markus 620: u_int clen;
1.12 markus 621: char prompt[1024];
1.1 markus 622: char *challenge, *response;
623:
624: debug("Doing skey authentication.");
625:
1.12 markus 626: for (i = 0; i < options.number_of_password_prompts; i++) {
627: /* request a challenge */
628: packet_start(SSH_CMSG_AUTH_TIS);
629: packet_send();
630: packet_write_wait();
1.1 markus 631:
1.12 markus 632: type = packet_read(&payload_len);
633: if (type != SSH_SMSG_FAILURE &&
634: type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
635: packet_disconnect("Protocol error: got %d in response "
636: "to skey-auth", type);
637: }
638: if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
639: debug("No challenge for skey authentication.");
640: return 0;
641: }
642: challenge = packet_get_string(&clen);
643: packet_integrity_check(payload_len, (4 + clen), type);
1.16 markus 644: snprintf(prompt, sizeof prompt, "%s%s", challenge,
645: strchr(challenge, '\n') ? "" : "\nResponse: ");
1.12 markus 646: xfree(challenge);
1.1 markus 647: if (i != 0)
648: error("Permission denied, please try again.");
1.12 markus 649: if (options.cipher == SSH_CIPHER_NONE)
650: log("WARNING: Encryption is disabled! "
651: "Reponse will be transmitted in clear text.");
652: response = read_passphrase(prompt, 0);
653: if (strcmp(response, "") == 0) {
654: xfree(response);
655: break;
656: }
1.1 markus 657: packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
658: packet_put_string(response, strlen(response));
659: memset(response, 0, strlen(response));
660: xfree(response);
661: packet_send();
662: packet_write_wait();
663: type = packet_read(&payload_len);
664: if (type == SSH_SMSG_SUCCESS)
665: return 1;
666: if (type != SSH_SMSG_FAILURE)
667: packet_disconnect("Protocol error: got %d in response "
1.12 markus 668: "to skey-auth-reponse", type);
1.1 markus 669: }
670: /* failure */
671: return 0;
672: }
673:
674: /*
675: * Tries to authenticate with plain passwd authentication.
676: */
677: int
678: try_password_authentication(char *prompt)
679: {
680: int type, i, payload_len;
681: char *password;
682:
683: debug("Doing password authentication.");
684: if (options.cipher == SSH_CIPHER_NONE)
685: log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
686: for (i = 0; i < options.number_of_password_prompts; i++) {
687: if (i != 0)
688: error("Permission denied, please try again.");
689: password = read_passphrase(prompt, 0);
690: packet_start(SSH_CMSG_AUTH_PASSWORD);
691: packet_put_string(password, strlen(password));
692: memset(password, 0, strlen(password));
693: xfree(password);
694: packet_send();
695: packet_write_wait();
696:
697: type = packet_read(&payload_len);
698: if (type == SSH_SMSG_SUCCESS)
699: return 1;
700: if (type != SSH_SMSG_FAILURE)
701: packet_disconnect("Protocol error: got %d in response to passwd auth", type);
702: }
703: /* failure */
704: return 0;
705: }
706:
707: /*
708: * SSH1 key exchange
709: */
710: void
711: ssh_kex(char *host, struct sockaddr *hostaddr)
712: {
713: int i;
714: BIGNUM *key;
715: RSA *host_key;
716: RSA *public_key;
717: Key k;
718: int bits, rbits;
719: int ssh_cipher_default = SSH_CIPHER_3DES;
1.13 markus 720: u_char session_key[SSH_SESSION_KEY_LENGTH];
721: u_char cookie[8];
722: u_int supported_ciphers;
723: u_int server_flags, client_flags;
1.1 markus 724: int payload_len, clen, sum_len = 0;
725: u_int32_t rand = 0;
726:
727: debug("Waiting for server public key.");
728:
729: /* Wait for a public key packet from the server. */
730: packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
731:
732: /* Get cookie from the packet. */
733: for (i = 0; i < 8; i++)
734: cookie[i] = packet_get_char();
735:
736: /* Get the public key. */
737: public_key = RSA_new();
738: bits = packet_get_int();/* bits */
739: public_key->e = BN_new();
740: packet_get_bignum(public_key->e, &clen);
741: sum_len += clen;
742: public_key->n = BN_new();
743: packet_get_bignum(public_key->n, &clen);
744: sum_len += clen;
745:
746: rbits = BN_num_bits(public_key->n);
747: if (bits != rbits) {
748: log("Warning: Server lies about size of server public key: "
749: "actual size is %d bits vs. announced %d.", rbits, bits);
750: log("Warning: This may be due to an old implementation of ssh.");
751: }
752: /* Get the host key. */
753: host_key = RSA_new();
754: bits = packet_get_int();/* bits */
755: host_key->e = BN_new();
756: packet_get_bignum(host_key->e, &clen);
757: sum_len += clen;
758: host_key->n = BN_new();
759: packet_get_bignum(host_key->n, &clen);
760: sum_len += clen;
761:
762: rbits = BN_num_bits(host_key->n);
763: if (bits != rbits) {
764: log("Warning: Server lies about size of server host key: "
765: "actual size is %d bits vs. announced %d.", rbits, bits);
766: log("Warning: This may be due to an old implementation of ssh.");
767: }
768:
769: /* Get protocol flags. */
770: server_flags = packet_get_int();
771: packet_set_protocol_flags(server_flags);
772:
773: supported_ciphers = packet_get_int();
774: supported_authentications = packet_get_int();
775:
776: debug("Received server public key (%d bits) and host key (%d bits).",
777: BN_num_bits(public_key->n), BN_num_bits(host_key->n));
778:
779: packet_integrity_check(payload_len,
780: 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
781: SSH_SMSG_PUBLIC_KEY);
1.9 markus 782: k.type = KEY_RSA1;
1.1 markus 783: k.rsa = host_key;
784: check_host_key(host, hostaddr, &k,
785: options.user_hostfile, options.system_hostfile);
786:
787: client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
788:
789: compute_session_id(session_id, cookie, host_key->n, public_key->n);
790:
791: /* Generate a session key. */
792: arc4random_stir();
793:
794: /*
795: * Generate an encryption key for the session. The key is a 256 bit
796: * random number, interpreted as a 32-byte key, with the least
797: * significant 8 bits being the first byte of the key.
798: */
799: for (i = 0; i < 32; i++) {
800: if (i % 4 == 0)
801: rand = arc4random();
802: session_key[i] = rand & 0xff;
803: rand >>= 8;
804: }
805:
806: /*
807: * According to the protocol spec, the first byte of the session key
808: * is the highest byte of the integer. The session key is xored with
809: * the first 16 bytes of the session id.
810: */
811: key = BN_new();
812: BN_set_word(key, 0);
813: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
814: BN_lshift(key, key, 8);
815: if (i < 16)
816: BN_add_word(key, session_key[i] ^ session_id[i]);
817: else
818: BN_add_word(key, session_key[i]);
819: }
820:
821: /*
822: * Encrypt the integer using the public key and host key of the
823: * server (key with smaller modulus first).
824: */
825: if (BN_cmp(public_key->n, host_key->n) < 0) {
826: /* Public key has smaller modulus. */
827: if (BN_num_bits(host_key->n) <
828: BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
829: fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
830: "SSH_KEY_BITS_RESERVED %d",
831: BN_num_bits(host_key->n),
832: BN_num_bits(public_key->n),
833: SSH_KEY_BITS_RESERVED);
834: }
835: rsa_public_encrypt(key, key, public_key);
836: rsa_public_encrypt(key, key, host_key);
837: } else {
838: /* Host key has smaller modulus (or they are equal). */
839: if (BN_num_bits(public_key->n) <
840: BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
841: fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
842: "SSH_KEY_BITS_RESERVED %d",
843: BN_num_bits(public_key->n),
844: BN_num_bits(host_key->n),
845: SSH_KEY_BITS_RESERVED);
846: }
847: rsa_public_encrypt(key, key, host_key);
848: rsa_public_encrypt(key, key, public_key);
849: }
850:
851: /* Destroy the public keys since we no longer need them. */
852: RSA_free(public_key);
853: RSA_free(host_key);
854:
1.11 markus 855: if (options.cipher == SSH_CIPHER_NOT_SET) {
856: if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default))
857: options.cipher = ssh_cipher_default;
858: } else if (options.cipher == SSH_CIPHER_ILLEGAL ||
1.10 markus 859: !(cipher_mask_ssh1(1) & (1 << options.cipher))) {
1.3 markus 860: log("No valid SSH1 cipher, using %.100s instead.",
1.7 markus 861: cipher_name(ssh_cipher_default));
862: options.cipher = ssh_cipher_default;
1.1 markus 863: }
864: /* Check that the selected cipher is supported. */
865: if (!(supported_ciphers & (1 << options.cipher)))
866: fatal("Selected cipher type %.100s not supported by server.",
867: cipher_name(options.cipher));
868:
869: debug("Encryption type: %.100s", cipher_name(options.cipher));
870:
871: /* Send the encrypted session key to the server. */
872: packet_start(SSH_CMSG_SESSION_KEY);
873: packet_put_char(options.cipher);
874:
875: /* Send the cookie back to the server. */
876: for (i = 0; i < 8; i++)
877: packet_put_char(cookie[i]);
878:
879: /* Send and destroy the encrypted encryption key integer. */
880: packet_put_bignum(key);
881: BN_clear_free(key);
882:
883: /* Send protocol flags. */
884: packet_put_int(client_flags);
885:
886: /* Send the packet now. */
887: packet_send();
888: packet_write_wait();
889:
890: debug("Sent encrypted session key.");
891:
892: /* Set the encryption key. */
893: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
894:
895: /* We will no longer need the session key here. Destroy any extra copies. */
896: memset(session_key, 0, sizeof(session_key));
897:
898: /*
899: * Expect a success message from the server. Note that this message
900: * will be received in encrypted form.
901: */
902: packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
903:
904: debug("Received encrypted confirmation.");
905: }
906:
907: /*
908: * Authenticate user
909: */
910: void
911: ssh_userauth(
1.15 deraadt 912: const char *local_user,
913: const char *server_user,
1.1 markus 914: char *host,
915: int host_key_valid, RSA *own_host_key)
916: {
917: int i, type;
918: int payload_len;
919:
920: if (supported_authentications == 0)
921: fatal("ssh_userauth: server supports no auth methods");
922:
923: /* Send the name of the user to log in as on the server. */
924: packet_start(SSH_CMSG_USER);
925: packet_put_string(server_user, strlen(server_user));
926: packet_send();
927: packet_write_wait();
928:
929: /*
930: * The server should respond with success if no authentication is
931: * needed (the user has no password). Otherwise the server responds
932: * with failure.
933: */
934: type = packet_read(&payload_len);
935:
936: /* check whether the connection was accepted without authentication. */
937: if (type == SSH_SMSG_SUCCESS)
938: return;
939: if (type != SSH_SMSG_FAILURE)
940: packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
941: type);
942:
943: #ifdef AFS
944: /* Try Kerberos tgt passing if the server supports it. */
945: if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
946: options.kerberos_tgt_passing) {
947: if (options.cipher == SSH_CIPHER_NONE)
948: log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
949: (void) send_kerberos_tgt();
950: }
951: /* Try AFS token passing if the server supports it. */
952: if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
953: options.afs_token_passing && k_hasafs()) {
954: if (options.cipher == SSH_CIPHER_NONE)
955: log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
956: send_afs_tokens();
957: }
958: #endif /* AFS */
959:
960: #ifdef KRB4
961: if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
962: options.kerberos_authentication) {
963: debug("Trying Kerberos authentication.");
964: if (try_kerberos_authentication()) {
965: /* The server should respond with success or failure. */
966: type = packet_read(&payload_len);
967: if (type == SSH_SMSG_SUCCESS)
968: return;
969: if (type != SSH_SMSG_FAILURE)
970: packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
971: }
972: }
973: #endif /* KRB4 */
974:
975: /*
976: * Use rhosts authentication if running in privileged socket and we
977: * do not wish to remain anonymous.
978: */
979: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
980: options.rhosts_authentication) {
981: debug("Trying rhosts authentication.");
982: packet_start(SSH_CMSG_AUTH_RHOSTS);
983: packet_put_string(local_user, strlen(local_user));
984: packet_send();
985: packet_write_wait();
986:
987: /* The server should respond with success or failure. */
988: type = packet_read(&payload_len);
989: if (type == SSH_SMSG_SUCCESS)
990: return;
991: if (type != SSH_SMSG_FAILURE)
992: packet_disconnect("Protocol error: got %d in response to rhosts auth",
993: type);
994: }
995: /*
996: * Try .rhosts or /etc/hosts.equiv authentication with RSA host
997: * authentication.
998: */
999: if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
1000: options.rhosts_rsa_authentication && host_key_valid) {
1001: if (try_rhosts_rsa_authentication(local_user, own_host_key))
1002: return;
1003: }
1004: /* Try RSA authentication if the server supports it. */
1005: if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
1006: options.rsa_authentication) {
1007: /*
1008: * Try RSA authentication using the authentication agent. The
1009: * agent is tried first because no passphrase is needed for
1010: * it, whereas identity files may require passphrases.
1011: */
1012: if (try_agent_authentication())
1013: return;
1014:
1015: /* Try RSA authentication for each identity. */
1016: for (i = 0; i < options.num_identity_files; i++)
1.9 markus 1017: if (options.identity_files_type[i] == KEY_RSA1 &&
1018: try_rsa_authentication(options.identity_files[i]))
1.1 markus 1019: return;
1020: }
1021: /* Try skey authentication if the server supports it. */
1022: if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
1023: options.skey_authentication && !options.batch_mode) {
1024: if (try_skey_authentication())
1025: return;
1026: }
1027: /* Try password authentication if the server supports it. */
1028: if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
1029: options.password_authentication && !options.batch_mode) {
1030: char prompt[80];
1031:
1032: snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
1033: server_user, host);
1034: if (try_password_authentication(prompt))
1035: return;
1036: }
1037: /* All authentication methods have failed. Exit with an error message. */
1038: fatal("Permission denied.");
1039: /* NOTREACHED */
1040: }
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