Annotation of src/usr.bin/ssh/auth1.c, Revision 1.43
1.1 markus 1: /*
2: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
3: * All rights reserved
1.4 deraadt 4: *
5: * As far as I am concerned, the code I have written for this software
6: * can be used freely for any purpose. Any derived versions of this
7: * software must be clearly marked as such, and if the derived work is
8: * incompatible with the protocol description in the RFC file, it must be
9: * called by a name other than "ssh" or "Secure Shell".
1.1 markus 10: */
11:
12: #include "includes.h"
1.43 ! itojun 13: RCSID("$OpenBSD: auth1.c,v 1.42 2002/08/22 21:33:58 markus Exp $");
1.1 markus 14:
15: #include "xmalloc.h"
16: #include "rsa.h"
1.12 markus 17: #include "ssh1.h"
1.1 markus 18: #include "packet.h"
19: #include "buffer.h"
20: #include "mpaux.h"
1.13 markus 21: #include "log.h"
1.1 markus 22: #include "servconf.h"
23: #include "compat.h"
24: #include "auth.h"
1.35 markus 25: #include "channels.h"
1.1 markus 26: #include "session.h"
1.25 dugsong 27: #include "uidswap.h"
1.38 provos 28: #include "monitor_wrap.h"
1.1 markus 29:
30: /* import */
31: extern ServerOptions options;
32:
33: /*
34: * convert ssh auth msg type into description
35: */
1.24 itojun 36: static char *
1.1 markus 37: get_authname(int type)
38: {
39: static char buf[1024];
40: switch (type) {
41: case SSH_CMSG_AUTH_PASSWORD:
42: return "password";
43: case SSH_CMSG_AUTH_RSA:
44: return "rsa";
45: case SSH_CMSG_AUTH_RHOSTS_RSA:
46: return "rhosts-rsa";
47: case SSH_CMSG_AUTH_RHOSTS:
48: return "rhosts";
1.11 markus 49: case SSH_CMSG_AUTH_TIS:
50: case SSH_CMSG_AUTH_TIS_RESPONSE:
51: return "challenge-response";
1.25 dugsong 52: #if defined(KRB4) || defined(KRB5)
1.1 markus 53: case SSH_CMSG_AUTH_KERBEROS:
54: return "kerberos";
55: #endif
56: }
57: snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
58: return buf;
59: }
60:
61: /*
1.11 markus 62: * read packets, try to authenticate the user and
63: * return only if authentication is successful
1.1 markus 64: */
1.24 itojun 65: static void
1.11 markus 66: do_authloop(Authctxt *authctxt)
1.1 markus 67: {
1.5 markus 68: int authenticated = 0;
1.8 markus 69: u_int bits;
1.29 markus 70: Key *client_host_key;
1.1 markus 71: BIGNUM *n;
72: char *client_user, *password;
1.11 markus 73: char info[1024];
1.8 markus 74: u_int dlen;
75: u_int ulen;
1.1 markus 76: int type = 0;
1.11 markus 77: struct passwd *pw = authctxt->pw;
78:
79: debug("Attempting authentication for %s%.100s.",
1.27 deraadt 80: authctxt->valid ? "" : "illegal user ", authctxt->user);
1.11 markus 81:
82: /* If the user has no password, accept authentication immediately. */
83: if (options.password_authentication &&
1.25 dugsong 84: #if defined(KRB4) || defined(KRB5)
1.11 markus 85: (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
86: #endif
1.38 provos 87: PRIVSEP(auth_password(authctxt, ""))) {
1.11 markus 88: auth_log(authctxt, 1, "without authentication", "");
89: return;
90: }
1.27 deraadt 91:
1.1 markus 92: /* Indicate that authentication is needed. */
93: packet_start(SSH_SMSG_FAILURE);
94: packet_send();
95: packet_write_wait();
96:
1.11 markus 97: for (;;) {
1.5 markus 98: /* default to fail */
99: authenticated = 0;
100:
1.11 markus 101: info[0] = '\0';
1.1 markus 102:
103: /* Get a packet from the client. */
1.34 markus 104: type = packet_read();
1.1 markus 105:
106: /* Process the packet. */
107: switch (type) {
108:
1.25 dugsong 109: #if defined(KRB4) || defined(KRB5)
1.1 markus 110: case SSH_CMSG_AUTH_KERBEROS:
111: if (!options.kerberos_authentication) {
112: verbose("Kerberos authentication disabled.");
113: } else {
1.25 dugsong 114: char *kdata = packet_get_string(&dlen);
1.32 markus 115: packet_check_eom();
1.27 deraadt 116:
1.25 dugsong 117: if (kdata[0] == 4) { /* KRB_PROT_VERSION */
118: #ifdef KRB4
119: KTEXT_ST tkt;
1.27 deraadt 120:
1.25 dugsong 121: tkt.length = dlen;
122: if (tkt.length < MAX_KTXT_LEN)
123: memcpy(tkt.dat, kdata, tkt.length);
1.27 deraadt 124:
1.25 dugsong 125: if (auth_krb4(authctxt, &tkt, &client_user)) {
126: authenticated = 1;
127: snprintf(info, sizeof(info),
128: " tktuser %.100s",
129: client_user);
130: xfree(client_user);
1.5 markus 131: }
1.25 dugsong 132: #endif /* KRB4 */
133: } else {
134: #ifdef KRB5
1.43 ! itojun 135: krb5_data tkt, reply;
1.25 dugsong 136: tkt.length = dlen;
137: tkt.data = kdata;
1.27 deraadt 138:
1.43 ! itojun 139: if (PRIVSEP(auth_krb5(authctxt, &tkt,
! 140: &client_user, &reply))) {
1.25 dugsong 141: authenticated = 1;
142: snprintf(info, sizeof(info),
143: " tktuser %.100s",
144: client_user);
1.43 ! itojun 145:
! 146: /* Send response to client */
! 147: packet_start(
! 148: SSH_SMSG_AUTH_KERBEROS_RESPONSE);
! 149: packet_put_string((char *)
! 150: reply.data, reply.length);
! 151: packet_send();
! 152: packet_write_wait();
! 153:
! 154: if (reply.length)
! 155: xfree(reply.data);
1.25 dugsong 156: xfree(client_user);
157: }
158: #endif /* KRB5 */
1.1 markus 159: }
1.11 markus 160: xfree(kdata);
1.1 markus 161: }
162: break;
1.25 dugsong 163: #endif /* KRB4 || KRB5 */
1.27 deraadt 164:
1.25 dugsong 165: #if defined(AFS) || defined(KRB5)
166: /* XXX - punt on backward compatibility here. */
167: case SSH_CMSG_HAVE_KERBEROS_TGT:
168: packet_send_debug("Kerberos TGT passing disabled before authentication.");
169: break;
170: #ifdef AFS
171: case SSH_CMSG_HAVE_AFS_TOKEN:
172: packet_send_debug("AFS token passing disabled before authentication.");
173: break;
174: #endif /* AFS */
175: #endif /* AFS || KRB5 */
1.27 deraadt 176:
1.1 markus 177: case SSH_CMSG_AUTH_RHOSTS:
178: if (!options.rhosts_authentication) {
179: verbose("Rhosts authentication disabled.");
180: break;
181: }
182: /*
183: * Get client user name. Note that we just have to
184: * trust the client; this is one reason why rhosts
185: * authentication is insecure. (Another is
186: * IP-spoofing on a local network.)
187: */
188: client_user = packet_get_string(&ulen);
1.32 markus 189: packet_check_eom();
1.1 markus 190:
1.5 markus 191: /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
1.1 markus 192: authenticated = auth_rhosts(pw, client_user);
193:
1.11 markus 194: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 195: xfree(client_user);
196: break;
197:
198: case SSH_CMSG_AUTH_RHOSTS_RSA:
199: if (!options.rhosts_rsa_authentication) {
200: verbose("Rhosts with RSA authentication disabled.");
201: break;
202: }
203: /*
204: * Get client user name. Note that we just have to
205: * trust the client; root on the client machine can
206: * claim to be any user.
207: */
208: client_user = packet_get_string(&ulen);
209:
210: /* Get the client host key. */
1.29 markus 211: client_host_key = key_new(KEY_RSA1);
1.1 markus 212: bits = packet_get_int();
1.33 markus 213: packet_get_bignum(client_host_key->rsa->e);
214: packet_get_bignum(client_host_key->rsa->n);
1.1 markus 215:
1.29 markus 216: if (bits != BN_num_bits(client_host_key->rsa->n))
1.5 markus 217: verbose("Warning: keysize mismatch for client_host_key: "
1.29 markus 218: "actual %d, announced %d",
1.41 deraadt 219: BN_num_bits(client_host_key->rsa->n), bits);
1.32 markus 220: packet_check_eom();
1.1 markus 221:
1.29 markus 222: authenticated = auth_rhosts_rsa(pw, client_user,
1.30 markus 223: client_host_key);
1.29 markus 224: key_free(client_host_key);
1.1 markus 225:
1.11 markus 226: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 227: xfree(client_user);
228: break;
229:
230: case SSH_CMSG_AUTH_RSA:
231: if (!options.rsa_authentication) {
232: verbose("RSA authentication disabled.");
233: break;
234: }
235: /* RSA authentication requested. */
1.29 markus 236: if ((n = BN_new()) == NULL)
237: fatal("do_authloop: BN_new failed");
1.33 markus 238: packet_get_bignum(n);
1.32 markus 239: packet_check_eom();
1.1 markus 240: authenticated = auth_rsa(pw, n);
241: BN_clear_free(n);
242: break;
243:
244: case SSH_CMSG_AUTH_PASSWORD:
245: if (!options.password_authentication) {
246: verbose("Password authentication disabled.");
247: break;
248: }
249: /*
250: * Read user password. It is in plain text, but was
251: * transmitted over the encrypted channel so it is
252: * not visible to an outside observer.
253: */
254: password = packet_get_string(&dlen);
1.32 markus 255: packet_check_eom();
1.1 markus 256:
257: /* Try authentication with the password. */
1.38 provos 258: authenticated = PRIVSEP(auth_password(authctxt, password));
1.1 markus 259:
260: memset(password, 0, strlen(password));
261: xfree(password);
262: break;
263:
264: case SSH_CMSG_AUTH_TIS:
265: debug("rcvd SSH_CMSG_AUTH_TIS");
1.23 markus 266: if (options.challenge_response_authentication == 1) {
267: char *challenge = get_challenge(authctxt);
1.11 markus 268: if (challenge != NULL) {
269: debug("sending challenge '%s'", challenge);
1.1 markus 270: packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
1.11 markus 271: packet_put_cstring(challenge);
1.23 markus 272: xfree(challenge);
1.1 markus 273: packet_send();
274: packet_write_wait();
275: continue;
276: }
277: }
278: break;
279: case SSH_CMSG_AUTH_TIS_RESPONSE:
280: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
1.23 markus 281: if (options.challenge_response_authentication == 1) {
1.1 markus 282: char *response = packet_get_string(&dlen);
1.11 markus 283: debug("got response '%s'", response);
1.32 markus 284: packet_check_eom();
1.11 markus 285: authenticated = verify_response(authctxt, response);
286: memset(response, 'r', dlen);
1.1 markus 287: xfree(response);
288: }
289: break;
290:
291: default:
292: /*
293: * Any unknown messages will be ignored (and failure
294: * returned) during authentication.
295: */
296: log("Unknown message during authentication: type %d", type);
297: break;
298: }
1.20 markus 299: #ifdef BSD_AUTH
300: if (authctxt->as) {
301: auth_close(authctxt->as);
302: authctxt->as = NULL;
303: }
304: #endif
1.11 markus 305: if (!authctxt->valid && authenticated)
306: fatal("INTERNAL ERROR: authenticated invalid user %s",
307: authctxt->user);
308:
309: /* Special handling for root */
1.42 markus 310: if (!use_privsep &&
311: authenticated && authctxt->pw->pw_uid == 0 &&
1.16 markus 312: !auth_root_allowed(get_authname(type)))
1.11 markus 313: authenticated = 0;
1.1 markus 314:
1.11 markus 315: /* Log before sending the reply */
316: auth_log(authctxt, authenticated, get_authname(type), info);
1.1 markus 317:
318: if (authenticated)
319: return;
320:
1.11 markus 321: if (authctxt->failures++ > AUTH_FAIL_MAX)
322: packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
1.1 markus 323:
324: packet_start(SSH_SMSG_FAILURE);
325: packet_send();
326: packet_write_wait();
327: }
328: }
329:
330: /*
331: * Performs authentication of an incoming connection. Session key has already
332: * been exchanged and encryption is enabled.
333: */
1.37 provos 334: Authctxt *
1.26 itojun 335: do_authentication(void)
1.1 markus 336: {
1.11 markus 337: Authctxt *authctxt;
1.8 markus 338: u_int ulen;
1.40 markus 339: char *user, *style = NULL;
1.1 markus 340:
341: /* Get the name of the user that we wish to log in as. */
1.34 markus 342: packet_read_expect(SSH_CMSG_USER);
1.1 markus 343:
344: /* Get the user name. */
345: user = packet_get_string(&ulen);
1.32 markus 346: packet_check_eom();
1.1 markus 347:
1.11 markus 348: if ((style = strchr(user, ':')) != NULL)
1.25 dugsong 349: *style++ = '\0';
1.11 markus 350:
1.40 markus 351: #ifdef KRB5
1.25 dugsong 352: /* XXX - SSH.com Kerberos v5 braindeath. */
1.40 markus 353: if ((datafellows & SSH_BUG_K5USER) &&
354: options.kerberos_authentication) {
355: char *p;
356: if ((p = strchr(user, '@')) != NULL)
357: *p = '\0';
358: }
359: #endif
1.27 deraadt 360:
1.11 markus 361: authctxt = authctxt_new();
362: authctxt->user = user;
363: authctxt->style = style;
364:
1.1 markus 365: /* Verify that the user is a valid user. */
1.39 markus 366: if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
1.11 markus 367: authctxt->valid = 1;
1.39 markus 368: else
1.11 markus 369: debug("do_authentication: illegal user %s", user);
1.17 markus 370:
1.39 markus 371: setproctitle("%s%s", authctxt->pw ? user : "unknown",
1.38 provos 372: use_privsep ? " [net]" : "");
1.1 markus 373:
374: /*
375: * If we are not running as root, the user must have the same uid as
376: * the server.
377: */
1.39 markus 378: if (!use_privsep && getuid() != 0 && authctxt->pw &&
379: authctxt->pw->pw_uid != getuid())
1.1 markus 380: packet_disconnect("Cannot change user when server not running as root.");
381:
1.11 markus 382: /*
383: * Loop until the user has been authenticated or the connection is
384: * closed, do_authloop() returns only if authentication is successful
385: */
386: do_authloop(authctxt);
1.1 markus 387:
388: /* The user has been authenticated and accepted. */
389: packet_start(SSH_SMSG_SUCCESS);
390: packet_send();
391: packet_write_wait();
392:
1.37 provos 393: return (authctxt);
1.1 markus 394: }
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