Annotation of src/usr.bin/ssh/auth1.c, Revision 1.48
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"
1.48 ! itojun 13: RCSID("$OpenBSD: auth1.c,v 1.47 2003/02/06 21:22:42 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
1.44 markus 119: KTEXT_ST tkt, reply;
1.25 dugsong 120: tkt.length = dlen;
121: if (tkt.length < MAX_KTXT_LEN)
122: memcpy(tkt.dat, kdata, tkt.length);
1.27 deraadt 123:
1.44 markus 124: if (PRIVSEP(auth_krb4(authctxt, &tkt,
125: &client_user, &reply))) {
1.25 dugsong 126: authenticated = 1;
127: snprintf(info, sizeof(info),
128: " tktuser %.100s",
129: client_user);
1.44 markus 130:
131: packet_start(
132: SSH_SMSG_AUTH_KERBEROS_RESPONSE);
133: packet_put_string((char *)
134: reply.dat, reply.length);
135: packet_send();
136: packet_write_wait();
137:
1.25 dugsong 138: xfree(client_user);
1.5 markus 139: }
1.25 dugsong 140: #endif /* KRB4 */
141: } else {
142: #ifdef KRB5
1.43 itojun 143: krb5_data tkt, reply;
1.25 dugsong 144: tkt.length = dlen;
145: tkt.data = kdata;
1.27 deraadt 146:
1.43 itojun 147: if (PRIVSEP(auth_krb5(authctxt, &tkt,
148: &client_user, &reply))) {
1.25 dugsong 149: authenticated = 1;
150: snprintf(info, sizeof(info),
151: " tktuser %.100s",
152: client_user);
1.45 deraadt 153:
1.43 itojun 154: /* Send response to client */
155: packet_start(
156: SSH_SMSG_AUTH_KERBEROS_RESPONSE);
157: packet_put_string((char *)
158: reply.data, reply.length);
159: packet_send();
160: packet_write_wait();
161:
162: if (reply.length)
163: xfree(reply.data);
1.25 dugsong 164: xfree(client_user);
165: }
166: #endif /* KRB5 */
1.1 markus 167: }
1.11 markus 168: xfree(kdata);
1.1 markus 169: }
170: break;
1.25 dugsong 171: #endif /* KRB4 || KRB5 */
1.27 deraadt 172:
1.25 dugsong 173: #if defined(AFS) || defined(KRB5)
174: /* XXX - punt on backward compatibility here. */
175: case SSH_CMSG_HAVE_KERBEROS_TGT:
176: packet_send_debug("Kerberos TGT passing disabled before authentication.");
177: break;
178: #ifdef AFS
179: case SSH_CMSG_HAVE_AFS_TOKEN:
180: packet_send_debug("AFS token passing disabled before authentication.");
181: break;
182: #endif /* AFS */
183: #endif /* AFS || KRB5 */
1.27 deraadt 184:
1.1 markus 185: case SSH_CMSG_AUTH_RHOSTS:
186: if (!options.rhosts_authentication) {
187: verbose("Rhosts authentication disabled.");
188: break;
189: }
190: /*
191: * Get client user name. Note that we just have to
192: * trust the client; this is one reason why rhosts
193: * authentication is insecure. (Another is
194: * IP-spoofing on a local network.)
195: */
196: client_user = packet_get_string(&ulen);
1.32 markus 197: packet_check_eom();
1.1 markus 198:
1.5 markus 199: /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
1.1 markus 200: authenticated = auth_rhosts(pw, client_user);
201:
1.11 markus 202: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 203: xfree(client_user);
204: break;
205:
206: case SSH_CMSG_AUTH_RHOSTS_RSA:
207: if (!options.rhosts_rsa_authentication) {
208: verbose("Rhosts with RSA authentication disabled.");
209: break;
210: }
211: /*
212: * Get client user name. Note that we just have to
213: * trust the client; root on the client machine can
214: * claim to be any user.
215: */
216: client_user = packet_get_string(&ulen);
217:
218: /* Get the client host key. */
1.29 markus 219: client_host_key = key_new(KEY_RSA1);
1.1 markus 220: bits = packet_get_int();
1.33 markus 221: packet_get_bignum(client_host_key->rsa->e);
222: packet_get_bignum(client_host_key->rsa->n);
1.1 markus 223:
1.29 markus 224: if (bits != BN_num_bits(client_host_key->rsa->n))
1.5 markus 225: verbose("Warning: keysize mismatch for client_host_key: "
1.29 markus 226: "actual %d, announced %d",
1.41 deraadt 227: BN_num_bits(client_host_key->rsa->n), bits);
1.32 markus 228: packet_check_eom();
1.1 markus 229:
1.29 markus 230: authenticated = auth_rhosts_rsa(pw, client_user,
1.30 markus 231: client_host_key);
1.29 markus 232: key_free(client_host_key);
1.1 markus 233:
1.11 markus 234: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 235: xfree(client_user);
236: break;
237:
238: case SSH_CMSG_AUTH_RSA:
239: if (!options.rsa_authentication) {
240: verbose("RSA authentication disabled.");
241: break;
242: }
243: /* RSA authentication requested. */
1.29 markus 244: if ((n = BN_new()) == NULL)
245: fatal("do_authloop: BN_new failed");
1.33 markus 246: packet_get_bignum(n);
1.32 markus 247: packet_check_eom();
1.1 markus 248: authenticated = auth_rsa(pw, n);
249: BN_clear_free(n);
250: break;
251:
252: case SSH_CMSG_AUTH_PASSWORD:
253: if (!options.password_authentication) {
254: verbose("Password authentication disabled.");
255: break;
256: }
257: /*
258: * Read user password. It is in plain text, but was
259: * transmitted over the encrypted channel so it is
260: * not visible to an outside observer.
261: */
262: password = packet_get_string(&dlen);
1.32 markus 263: packet_check_eom();
1.1 markus 264:
265: /* Try authentication with the password. */
1.38 provos 266: authenticated = PRIVSEP(auth_password(authctxt, password));
1.1 markus 267:
268: memset(password, 0, strlen(password));
269: xfree(password);
270: break;
271:
272: case SSH_CMSG_AUTH_TIS:
273: debug("rcvd SSH_CMSG_AUTH_TIS");
1.23 markus 274: if (options.challenge_response_authentication == 1) {
275: char *challenge = get_challenge(authctxt);
1.11 markus 276: if (challenge != NULL) {
277: debug("sending challenge '%s'", challenge);
1.1 markus 278: packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
1.11 markus 279: packet_put_cstring(challenge);
1.23 markus 280: xfree(challenge);
1.1 markus 281: packet_send();
282: packet_write_wait();
283: continue;
284: }
285: }
286: break;
287: case SSH_CMSG_AUTH_TIS_RESPONSE:
288: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
1.23 markus 289: if (options.challenge_response_authentication == 1) {
1.1 markus 290: char *response = packet_get_string(&dlen);
1.32 markus 291: packet_check_eom();
1.11 markus 292: authenticated = verify_response(authctxt, response);
293: memset(response, 'r', dlen);
1.1 markus 294: xfree(response);
295: }
296: break;
297:
298: default:
299: /*
300: * Any unknown messages will be ignored (and failure
301: * returned) during authentication.
302: */
1.48 ! itojun 303: logit("Unknown message during authentication: type %d", type);
1.1 markus 304: break;
305: }
1.20 markus 306: #ifdef BSD_AUTH
307: if (authctxt->as) {
308: auth_close(authctxt->as);
309: authctxt->as = NULL;
310: }
311: #endif
1.11 markus 312: if (!authctxt->valid && authenticated)
313: fatal("INTERNAL ERROR: authenticated invalid user %s",
314: authctxt->user);
315:
316: /* Special handling for root */
1.47 markus 317: if (authenticated && authctxt->pw->pw_uid == 0 &&
1.16 markus 318: !auth_root_allowed(get_authname(type)))
1.11 markus 319: authenticated = 0;
1.1 markus 320:
1.11 markus 321: /* Log before sending the reply */
322: auth_log(authctxt, authenticated, get_authname(type), info);
1.1 markus 323:
324: if (authenticated)
325: return;
326:
1.11 markus 327: if (authctxt->failures++ > AUTH_FAIL_MAX)
328: packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
1.1 markus 329:
330: packet_start(SSH_SMSG_FAILURE);
331: packet_send();
332: packet_write_wait();
333: }
334: }
335:
336: /*
337: * Performs authentication of an incoming connection. Session key has already
338: * been exchanged and encryption is enabled.
339: */
1.37 provos 340: Authctxt *
1.26 itojun 341: do_authentication(void)
1.1 markus 342: {
1.11 markus 343: Authctxt *authctxt;
1.8 markus 344: u_int ulen;
1.40 markus 345: char *user, *style = NULL;
1.1 markus 346:
347: /* Get the name of the user that we wish to log in as. */
1.34 markus 348: packet_read_expect(SSH_CMSG_USER);
1.1 markus 349:
350: /* Get the user name. */
351: user = packet_get_string(&ulen);
1.32 markus 352: packet_check_eom();
1.1 markus 353:
1.11 markus 354: if ((style = strchr(user, ':')) != NULL)
1.25 dugsong 355: *style++ = '\0';
1.11 markus 356:
1.40 markus 357: #ifdef KRB5
1.25 dugsong 358: /* XXX - SSH.com Kerberos v5 braindeath. */
1.40 markus 359: if ((datafellows & SSH_BUG_K5USER) &&
360: options.kerberos_authentication) {
361: char *p;
362: if ((p = strchr(user, '@')) != NULL)
363: *p = '\0';
364: }
365: #endif
1.27 deraadt 366:
1.11 markus 367: authctxt = authctxt_new();
368: authctxt->user = user;
369: authctxt->style = style;
370:
1.1 markus 371: /* Verify that the user is a valid user. */
1.39 markus 372: if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
1.11 markus 373: authctxt->valid = 1;
1.39 markus 374: else
1.11 markus 375: debug("do_authentication: illegal user %s", user);
1.17 markus 376:
1.39 markus 377: setproctitle("%s%s", authctxt->pw ? user : "unknown",
1.38 provos 378: use_privsep ? " [net]" : "");
1.1 markus 379:
380: /*
381: * If we are not running as root, the user must have the same uid as
382: * the server.
383: */
1.39 markus 384: if (!use_privsep && getuid() != 0 && authctxt->pw &&
385: authctxt->pw->pw_uid != getuid())
1.1 markus 386: packet_disconnect("Cannot change user when server not running as root.");
387:
1.11 markus 388: /*
389: * Loop until the user has been authenticated or the connection is
390: * closed, do_authloop() returns only if authentication is successful
391: */
392: do_authloop(authctxt);
1.1 markus 393:
394: /* The user has been authenticated and accepted. */
395: packet_start(SSH_SMSG_SUCCESS);
396: packet_send();
397: packet_write_wait();
398:
1.37 provos 399: return (authctxt);
1.1 markus 400: }
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