1 /*
2 * Copyright (c) 1999 Dug Song. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25 #include "includes.h"
26 RCSID("$OpenBSD: auth-krb4.c,v 1.28 2002/09/26 11:38:43 markus Exp $");
27
28 #pragma ident "%Z%%M% %I% %E% SMI"
29
30 #include "ssh.h"
31 #include "ssh1.h"
32 #include "packet.h"
33 #include "xmalloc.h"
34 #include "log.h"
35 #include "servconf.h"
36 #include "uidswap.h"
37 #include "auth.h"
38
39 #ifdef AFS
40 #include "radix.h"
41 #endif
42
43 #ifdef KRB4
44 extern ServerOptions options;
45
46 static int
47 krb4_init(void *context)
48 {
49 static int cleanup_registered = 0;
50 Authctxt *authctxt = (Authctxt *)context;
51 const char *tkt_root = TKT_ROOT;
52 struct stat st;
53 int fd;
54
55 if (!authctxt->krb4_ticket_file) {
56 /* Set unique ticket string manually since we're still root. */
57 authctxt->krb4_ticket_file = xmalloc(MAXPATHLEN);
58 #ifdef AFS
59 if (lstat("/ticket", &st) != -1)
60 tkt_root = "/ticket/";
61 #endif /* AFS */
62 snprintf(authctxt->krb4_ticket_file, MAXPATHLEN, "%s%u_%ld",
63 tkt_root, authctxt->pw->pw_uid, (long)getpid());
64 krb_set_tkt_string(authctxt->krb4_ticket_file);
65 }
66 /* Register ticket cleanup in case of fatal error. */
67 if (!cleanup_registered) {
68 fatal_add_cleanup(krb4_cleanup_proc, authctxt);
69 cleanup_registered = 1;
70 }
71 /* Try to create our ticket file. */
72 if ((fd = mkstemp(authctxt->krb4_ticket_file)) != -1) {
73 close(fd);
74 return (1);
75 }
76 /* Ticket file exists - make sure user owns it (just passed ticket). */
77 if (lstat(authctxt->krb4_ticket_file, &st) != -1) {
78 if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
79 st.st_uid == authctxt->pw->pw_uid)
80 return (1);
81 }
82 /* Failure - cancel cleanup function, leaving ticket for inspection. */
83 log("WARNING: bad ticket file %s", authctxt->krb4_ticket_file);
84
85 fatal_remove_cleanup(krb4_cleanup_proc, authctxt);
86 cleanup_registered = 0;
87
88 xfree(authctxt->krb4_ticket_file);
89 authctxt->krb4_ticket_file = NULL;
90
91 return (0);
92 }
93
94 /*
95 * try krb4 authentication,
96 * return 1 on success, 0 on failure, -1 if krb4 is not available
97 */
98 int
99 auth_krb4_password(Authctxt *authctxt, const char *password)
100 {
101 AUTH_DAT adata;
102 KTEXT_ST tkt;
103 struct hostent *hp;
104 struct passwd *pw;
105 char localhost[MAXHOSTNAMELEN], phost[INST_SZ], realm[REALM_SZ];
106 u_int32_t faddr;
107 int r;
108
109 if ((pw = authctxt->pw) == NULL)
110 return (0);
111
112 /*
113 * Try Kerberos password authentication only for non-root
114 * users and only if Kerberos is installed.
115 */
116 if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
117 /* Set up our ticket file. */
118 if (!krb4_init(authctxt)) {
119 log("Couldn't initialize Kerberos ticket file for %s!",
120 pw->pw_name);
121 goto failure;
122 }
123 /* Try to get TGT using our password. */
124 r = krb_get_pw_in_tkt((char *) pw->pw_name, "", realm,
125 "krbtgt", realm, DEFAULT_TKT_LIFE, (char *)password);
126 if (r != INTK_OK) {
127 debug("Kerberos v4 password authentication for %s "
128 "failed: %s", pw->pw_name, krb_err_txt[r]);
129 goto failure;
130 }
131 /* Successful authentication. */
132 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
133
134 /*
135 * Now that we have a TGT, try to get a local
136 * "rcmd" ticket to ensure that we are not talking
137 * to a bogus Kerberos server.
138 */
139 gethostname(localhost, sizeof(localhost));
140 strlcpy(phost, (char *)krb_get_phost(localhost),
141 sizeof(phost));
142 r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
143
144 if (r == KSUCCESS) {
145 if ((hp = gethostbyname(localhost)) == NULL) {
146 log("Couldn't get local host address!");
147 goto failure;
148 }
149 memmove((void *)&faddr, (void *)hp->h_addr,
150 sizeof(faddr));
151
152 /* Verify our "rcmd" ticket. */
153 r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
154 faddr, &adata, "");
155 if (r == RD_AP_UNDEC) {
156 /*
157 * Probably didn't have a srvtab on
158 * localhost. Disallow login.
159 */
160 log("Kerberos v4 TGT for %s unverifiable, "
161 "no srvtab installed? krb_rd_req: %s",
162 pw->pw_name, krb_err_txt[r]);
163 goto failure;
164 } else if (r != KSUCCESS) {
165 log("Kerberos v4 %s ticket unverifiable: %s",
166 KRB4_SERVICE_NAME, krb_err_txt[r]);
167 goto failure;
168 }
169 } else if (r == KDC_PR_UNKNOWN) {
170 /*
171 * Disallow login if no rcmd service exists, and
172 * log the error.
173 */
174 log("Kerberos v4 TGT for %s unverifiable: %s; %s.%s "
175 "not registered, or srvtab is wrong?", pw->pw_name,
176 krb_err_txt[r], KRB4_SERVICE_NAME, phost);
177 goto failure;
178 } else {
179 /*
180 * TGT is bad, forget it. Possibly spoofed!
181 */
182 debug("WARNING: Kerberos v4 TGT possibly spoofed "
183 "for %s: %s", pw->pw_name, krb_err_txt[r]);
184 goto failure;
185 }
186 /* Authentication succeeded. */
187 return (1);
188 } else
189 /* Logging in as root or no local Kerberos realm. */
190 debug("Unable to authenticate to Kerberos.");
191
192 failure:
193 krb4_cleanup_proc(authctxt);
194
195 if (!options.kerberos_or_local_passwd)
196 return (0);
197
198 /* Fall back to ordinary passwd authentication. */
199 return (-1);
200 }
201
202 void
203 krb4_cleanup_proc(void *context)
204 {
205 Authctxt *authctxt = (Authctxt *)context;
206 debug("krb4_cleanup_proc called");
207 if (authctxt->krb4_ticket_file) {
208 (void) dest_tkt();
209 xfree(authctxt->krb4_ticket_file);
210 authctxt->krb4_ticket_file = NULL;
211 }
212 }
213
214 int
215 auth_krb4(Authctxt *authctxt, KTEXT auth, char **client, KTEXT reply)
216 {
217 AUTH_DAT adat = {0};
218 Key_schedule schedule;
219 struct sockaddr_in local, foreign;
220 char instance[INST_SZ];
221 socklen_t slen;
222 u_int cksum;
223 int r, s;
224
225 s = packet_get_connection_in();
226
227 slen = sizeof(local);
228 memset(&local, 0, sizeof(local));
229 if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
230 debug("getsockname failed: %.100s", strerror(errno));
231 slen = sizeof(foreign);
232 memset(&foreign, 0, sizeof(foreign));
233 if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
234 debug("getpeername failed: %.100s", strerror(errno));
235 fatal_cleanup();
236 }
237 instance[0] = '*';
238 instance[1] = 0;
239
240 /* Get the encrypted request, challenge, and session key. */
241 if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance,
242 0, &adat, ""))) {
243 debug("Kerberos v4 krb_rd_req: %.100s", krb_err_txt[r]);
244 return (0);
245 }
246 des_key_sched((des_cblock *) adat.session, schedule);
247
248 *client = xmalloc(MAX_K_NAME_SZ);
249 (void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
250 *adat.pinst ? "." : "", adat.pinst, adat.prealm);
251
252 /* Check ~/.klogin authorization now. */
253 if (kuserok(&adat, authctxt->user) != KSUCCESS) {
254 log("Kerberos v4 .klogin authorization failed for %s to "
255 "account %s", *client, authctxt->user);
256 xfree(*client);
257 *client = NULL;
258 return (0);
259 }
260 /* Increment the checksum, and return it encrypted with the
261 session key. */
262 cksum = adat.checksum + 1;
263 cksum = htonl(cksum);
264
265 /* If we can't successfully encrypt the checksum, we send back an
266 empty message, admitting our failure. */
267 if ((r = krb_mk_priv((u_char *) & cksum, reply->dat, sizeof(cksum) + 1,
268 schedule, &adat.session, &local, &foreign)) < 0) {
269 debug("Kerberos v4 mk_priv: (%d) %s", r, krb_err_txt[r]);
270 reply->dat[0] = 0;
271 reply->length = 0;
272 } else
273 reply->length = r;
274
275 /* Clear session key. */
276 memset(&adat.session, 0, sizeof(&adat.session));
277 return (1);
278 }
279 #endif /* KRB4 */
280
281 #ifdef AFS
282 int
283 auth_krb4_tgt(Authctxt *authctxt, const char *string)
284 {
285 CREDENTIALS creds;
286 struct passwd *pw;
287
288 if ((pw = authctxt->pw) == NULL)
289 goto failure;
290
291 temporarily_use_uid(pw);
292
293 if (!radix_to_creds(string, &creds)) {
294 log("Protocol error decoding Kerberos v4 TGT");
295 goto failure;
296 }
297 if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
298 strlcpy(creds.service, "krbtgt", sizeof creds.service);
299
300 if (strcmp(creds.service, "krbtgt")) {
301 log("Kerberos v4 TGT (%s%s%s@%s) rejected for %s",
302 creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
303 creds.realm, pw->pw_name);
304 goto failure;
305 }
306 if (!krb4_init(authctxt))
307 goto failure;
308
309 if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
310 goto failure;
311
312 if (save_credentials(creds.service, creds.instance, creds.realm,
313 creds.session, creds.lifetime, creds.kvno, &creds.ticket_st,
314 creds.issue_date) != KSUCCESS) {
315 debug("Kerberos v4 TGT refused: couldn't save credentials");
316 goto failure;
317 }
318 /* Successful authentication, passed all checks. */
319 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
320
321 debug("Kerberos v4 TGT accepted (%s%s%s@%s)",
322 creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
323 memset(&creds, 0, sizeof(creds));
324
325 restore_uid();
326
327 return (1);
328
329 failure:
330 krb4_cleanup_proc(authctxt);
331 memset(&creds, 0, sizeof(creds));
332 restore_uid();
333
334 return (0);
335 }
336
337 int
338 auth_afs_token(Authctxt *authctxt, const char *token_string)
339 {
340 CREDENTIALS creds;
341 struct passwd *pw;
342 uid_t uid;
343
344 if ((pw = authctxt->pw) == NULL)
345 return (0);
346
347 if (!radix_to_creds(token_string, &creds)) {
348 log("Protocol error decoding AFS token");
349 return (0);
350 }
351 if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
352 strlcpy(creds.service, "afs", sizeof creds.service);
353
354 if (strncmp(creds.pname, "AFS ID ", 7) == 0)
355 uid = atoi(creds.pname + 7);
356 else
357 uid = pw->pw_uid;
358
359 if (kafs_settoken(creds.realm, uid, &creds)) {
360 log("AFS token (%s@%s) rejected for %s",
361 creds.pname, creds.realm, pw->pw_name);
362 memset(&creds, 0, sizeof(creds));
363 return (0);
364 }
365 debug("AFS token accepted (%s@%s)", creds.pname, creds.realm);
366 memset(&creds, 0, sizeof(creds));
367
368 return (1);
369 }
370 #endif /* AFS */