Annotation of src/usr.bin/ssh/auth1.c, Revision 1.30
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"
1.30 ! markus 13: RCSID("$OpenBSD: auth1.c,v 1.29 2001/12/27 18:22:16 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"
25: #include "session.h"
1.18 markus 26: #include "misc.h"
1.25 dugsong 27: #include "uidswap.h"
1.1 markus 28:
29: /* import */
30: extern ServerOptions options;
31:
32: /*
33: * convert ssh auth msg type into description
34: */
1.24 itojun 35: static char *
1.1 markus 36: get_authname(int type)
37: {
38: static char buf[1024];
39: switch (type) {
40: case SSH_CMSG_AUTH_PASSWORD:
41: return "password";
42: case SSH_CMSG_AUTH_RSA:
43: return "rsa";
44: case SSH_CMSG_AUTH_RHOSTS_RSA:
45: return "rhosts-rsa";
46: case SSH_CMSG_AUTH_RHOSTS:
47: return "rhosts";
1.11 markus 48: case SSH_CMSG_AUTH_TIS:
49: case SSH_CMSG_AUTH_TIS_RESPONSE:
50: return "challenge-response";
1.25 dugsong 51: #if defined(KRB4) || defined(KRB5)
1.1 markus 52: case SSH_CMSG_AUTH_KERBEROS:
53: return "kerberos";
54: #endif
55: }
56: snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
57: return buf;
58: }
59:
60: /*
1.11 markus 61: * read packets, try to authenticate the user and
62: * return only if authentication is successful
1.1 markus 63: */
1.24 itojun 64: static void
1.11 markus 65: do_authloop(Authctxt *authctxt)
1.1 markus 66: {
1.5 markus 67: int authenticated = 0;
1.8 markus 68: u_int bits;
1.29 markus 69: Key *client_host_key;
1.1 markus 70: BIGNUM *n;
71: char *client_user, *password;
1.11 markus 72: char info[1024];
1.8 markus 73: u_int dlen;
1.1 markus 74: int plen, nlen, elen;
1.8 markus 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
1.20 markus 87: 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. */
104: type = packet_read(&plen);
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);
1.27 deraadt 115:
1.25 dugsong 116: packet_integrity_check(plen, 4 + dlen, type);
1.27 deraadt 117:
1.25 dugsong 118: if (kdata[0] == 4) { /* KRB_PROT_VERSION */
119: #ifdef KRB4
120: KTEXT_ST tkt;
1.27 deraadt 121:
1.25 dugsong 122: tkt.length = dlen;
123: if (tkt.length < MAX_KTXT_LEN)
124: memcpy(tkt.dat, kdata, tkt.length);
1.27 deraadt 125:
1.25 dugsong 126: if (auth_krb4(authctxt, &tkt, &client_user)) {
127: authenticated = 1;
128: snprintf(info, sizeof(info),
129: " tktuser %.100s",
130: client_user);
131: xfree(client_user);
1.5 markus 132: }
1.25 dugsong 133: #endif /* KRB4 */
134: } else {
135: #ifdef KRB5
136: krb5_data tkt;
137: tkt.length = dlen;
138: tkt.data = kdata;
1.27 deraadt 139:
1.25 dugsong 140: if (auth_krb5(authctxt, &tkt, &client_user)) {
141: authenticated = 1;
142: snprintf(info, sizeof(info),
143: " tktuser %.100s",
144: client_user);
145: xfree(client_user);
146: }
147: #endif /* KRB5 */
1.1 markus 148: }
1.11 markus 149: xfree(kdata);
1.1 markus 150: }
151: break;
1.25 dugsong 152: #endif /* KRB4 || KRB5 */
1.27 deraadt 153:
1.25 dugsong 154: #if defined(AFS) || defined(KRB5)
155: /* XXX - punt on backward compatibility here. */
156: case SSH_CMSG_HAVE_KERBEROS_TGT:
157: packet_send_debug("Kerberos TGT passing disabled before authentication.");
158: break;
159: #ifdef AFS
160: case SSH_CMSG_HAVE_AFS_TOKEN:
161: packet_send_debug("AFS token passing disabled before authentication.");
162: break;
163: #endif /* AFS */
164: #endif /* AFS || KRB5 */
1.27 deraadt 165:
1.1 markus 166: case SSH_CMSG_AUTH_RHOSTS:
167: if (!options.rhosts_authentication) {
168: verbose("Rhosts authentication disabled.");
169: break;
170: }
171: /*
172: * Get client user name. Note that we just have to
173: * trust the client; this is one reason why rhosts
174: * authentication is insecure. (Another is
175: * IP-spoofing on a local network.)
176: */
177: client_user = packet_get_string(&ulen);
178: packet_integrity_check(plen, 4 + ulen, type);
179:
1.5 markus 180: /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
1.1 markus 181: authenticated = auth_rhosts(pw, client_user);
182:
1.11 markus 183: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 184: xfree(client_user);
185: break;
186:
187: case SSH_CMSG_AUTH_RHOSTS_RSA:
188: if (!options.rhosts_rsa_authentication) {
189: verbose("Rhosts with RSA authentication disabled.");
190: break;
191: }
192: /*
193: * Get client user name. Note that we just have to
194: * trust the client; root on the client machine can
195: * claim to be any user.
196: */
197: client_user = packet_get_string(&ulen);
198:
199: /* Get the client host key. */
1.29 markus 200: client_host_key = key_new(KEY_RSA1);
1.1 markus 201: bits = packet_get_int();
1.29 markus 202: packet_get_bignum(client_host_key->rsa->e, &elen);
203: packet_get_bignum(client_host_key->rsa->n, &nlen);
1.1 markus 204:
1.29 markus 205: if (bits != BN_num_bits(client_host_key->rsa->n))
1.5 markus 206: verbose("Warning: keysize mismatch for client_host_key: "
1.29 markus 207: "actual %d, announced %d",
208: BN_num_bits(client_host_key->rsa->n), bits);
1.1 markus 209: packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
210:
1.29 markus 211: authenticated = auth_rhosts_rsa(pw, client_user,
1.30 ! markus 212: client_host_key);
1.29 markus 213: key_free(client_host_key);
1.1 markus 214:
1.11 markus 215: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 216: xfree(client_user);
217: break;
218:
219: case SSH_CMSG_AUTH_RSA:
220: if (!options.rsa_authentication) {
221: verbose("RSA authentication disabled.");
222: break;
223: }
224: /* RSA authentication requested. */
1.29 markus 225: if ((n = BN_new()) == NULL)
226: fatal("do_authloop: BN_new failed");
1.1 markus 227: packet_get_bignum(n, &nlen);
228: packet_integrity_check(plen, nlen, type);
229: authenticated = auth_rsa(pw, n);
230: BN_clear_free(n);
231: break;
232:
233: case SSH_CMSG_AUTH_PASSWORD:
234: if (!options.password_authentication) {
235: verbose("Password authentication disabled.");
236: break;
237: }
238: /*
239: * Read user password. It is in plain text, but was
240: * transmitted over the encrypted channel so it is
241: * not visible to an outside observer.
242: */
243: password = packet_get_string(&dlen);
244: packet_integrity_check(plen, 4 + dlen, type);
245:
246: /* Try authentication with the password. */
1.20 markus 247: authenticated = auth_password(authctxt, password);
1.1 markus 248:
249: memset(password, 0, strlen(password));
250: xfree(password);
251: break;
252:
253: case SSH_CMSG_AUTH_TIS:
254: debug("rcvd SSH_CMSG_AUTH_TIS");
1.23 markus 255: if (options.challenge_response_authentication == 1) {
256: char *challenge = get_challenge(authctxt);
1.11 markus 257: if (challenge != NULL) {
258: debug("sending challenge '%s'", challenge);
1.1 markus 259: packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
1.11 markus 260: packet_put_cstring(challenge);
1.23 markus 261: xfree(challenge);
1.1 markus 262: packet_send();
263: packet_write_wait();
264: continue;
265: }
266: }
267: break;
268: case SSH_CMSG_AUTH_TIS_RESPONSE:
269: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
1.23 markus 270: if (options.challenge_response_authentication == 1) {
1.1 markus 271: char *response = packet_get_string(&dlen);
1.11 markus 272: debug("got response '%s'", response);
1.1 markus 273: packet_integrity_check(plen, 4 + dlen, type);
1.11 markus 274: authenticated = verify_response(authctxt, response);
275: memset(response, 'r', dlen);
1.1 markus 276: xfree(response);
277: }
278: break;
279:
280: default:
281: /*
282: * Any unknown messages will be ignored (and failure
283: * returned) during authentication.
284: */
285: log("Unknown message during authentication: type %d", type);
286: break;
287: }
1.20 markus 288: #ifdef BSD_AUTH
289: if (authctxt->as) {
290: auth_close(authctxt->as);
291: authctxt->as = NULL;
292: }
293: #endif
1.11 markus 294: if (!authctxt->valid && authenticated)
295: fatal("INTERNAL ERROR: authenticated invalid user %s",
296: authctxt->user);
297:
298: /* Special handling for root */
1.16 markus 299: if (authenticated && authctxt->pw->pw_uid == 0 &&
300: !auth_root_allowed(get_authname(type)))
1.11 markus 301: authenticated = 0;
1.1 markus 302:
1.11 markus 303: /* Log before sending the reply */
304: auth_log(authctxt, authenticated, get_authname(type), info);
1.1 markus 305:
306: if (authenticated)
307: return;
308:
1.11 markus 309: if (authctxt->failures++ > AUTH_FAIL_MAX)
310: packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
1.1 markus 311:
312: packet_start(SSH_SMSG_FAILURE);
313: packet_send();
314: packet_write_wait();
315: }
316: }
317:
318: /*
319: * Performs authentication of an incoming connection. Session key has already
320: * been exchanged and encryption is enabled.
321: */
322: void
1.26 itojun 323: do_authentication(void)
1.1 markus 324: {
1.11 markus 325: Authctxt *authctxt;
326: struct passwd *pw;
1.1 markus 327: int plen;
1.8 markus 328: u_int ulen;
1.25 dugsong 329: char *p, *user, *style = NULL;
1.1 markus 330:
331: /* Get the name of the user that we wish to log in as. */
332: packet_read_expect(&plen, SSH_CMSG_USER);
333:
334: /* Get the user name. */
335: user = packet_get_string(&ulen);
336: packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
337:
1.11 markus 338: if ((style = strchr(user, ':')) != NULL)
1.25 dugsong 339: *style++ = '\0';
1.11 markus 340:
1.25 dugsong 341: /* XXX - SSH.com Kerberos v5 braindeath. */
342: if ((p = strchr(user, '@')) != NULL)
343: *p = '\0';
1.27 deraadt 344:
1.11 markus 345: authctxt = authctxt_new();
346: authctxt->user = user;
347: authctxt->style = style;
348:
1.1 markus 349: /* Verify that the user is a valid user. */
350: pw = getpwnam(user);
1.5 markus 351: if (pw && allowed_user(pw)) {
1.11 markus 352: authctxt->valid = 1;
353: pw = pwcopy(pw);
1.5 markus 354: } else {
1.11 markus 355: debug("do_authentication: illegal user %s", user);
1.5 markus 356: pw = NULL;
357: }
1.11 markus 358: authctxt->pw = pw;
1.17 markus 359:
360: setproctitle("%s", pw ? user : "unknown");
1.1 markus 361:
362: /*
363: * If we are not running as root, the user must have the same uid as
364: * the server.
365: */
1.5 markus 366: if (getuid() != 0 && pw && pw->pw_uid != getuid())
1.1 markus 367: packet_disconnect("Cannot change user when server not running as root.");
368:
1.11 markus 369: /*
370: * Loop until the user has been authenticated or the connection is
371: * closed, do_authloop() returns only if authentication is successful
372: */
373: do_authloop(authctxt);
1.1 markus 374:
375: /* The user has been authenticated and accepted. */
376: packet_start(SSH_SMSG_SUCCESS);
377: packet_send();
378: packet_write_wait();
379:
380: /* Perform session preparation. */
1.21 markus 381: do_authenticated(authctxt);
1.1 markus 382: }
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