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-rw-r--r--auth-krb4.c368
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diff --git a/auth-krb4.c b/auth-krb4.c
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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"
26RCSID("$OpenBSD: auth-krb4.c,v 1.29 2003/02/21 10:34:48 mpech Exp $");
27
28#include "ssh.h"
29#include "ssh1.h"
30#include "packet.h"
31#include "xmalloc.h"
32#include "log.h"
33#include "servconf.h"
34#include "uidswap.h"
35#include "auth.h"
36
37#ifdef AFS
38#include "radix.h"
39#endif
40
41#ifdef KRB4
42extern ServerOptions options;
43
44static int
45krb4_init(void *context)
46{
47 static int cleanup_registered = 0;
48 Authctxt *authctxt = (Authctxt *)context;
49 const char *tkt_root = TKT_ROOT;
50 struct stat st;
51 int fd;
52
53 if (!authctxt->krb4_ticket_file) {
54 /* Set unique ticket string manually since we're still root. */
55 authctxt->krb4_ticket_file = xmalloc(MAXPATHLEN);
56#ifdef AFS
57 if (lstat("/ticket", &st) != -1)
58 tkt_root = "/ticket/";
59#endif /* AFS */
60 snprintf(authctxt->krb4_ticket_file, MAXPATHLEN, "%s%u_%ld",
61 tkt_root, authctxt->pw->pw_uid, (long)getpid());
62 krb_set_tkt_string(authctxt->krb4_ticket_file);
63 }
64 /* Register ticket cleanup in case of fatal error. */
65 if (!cleanup_registered) {
66 fatal_add_cleanup(krb4_cleanup_proc, authctxt);
67 cleanup_registered = 1;
68 }
69 /* Try to create our ticket file. */
70 if ((fd = mkstemp(authctxt->krb4_ticket_file)) != -1) {
71 close(fd);
72 return (1);
73 }
74 /* Ticket file exists - make sure user owns it (just passed ticket). */
75 if (lstat(authctxt->krb4_ticket_file, &st) != -1) {
76 if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
77 st.st_uid == authctxt->pw->pw_uid)
78 return (1);
79 }
80 /* Failure - cancel cleanup function, leaving ticket for inspection. */
81 log("WARNING: bad ticket file %s", authctxt->krb4_ticket_file);
82
83 fatal_remove_cleanup(krb4_cleanup_proc, authctxt);
84 cleanup_registered = 0;
85
86 xfree(authctxt->krb4_ticket_file);
87 authctxt->krb4_ticket_file = NULL;
88
89 return (0);
90}
91
92/*
93 * try krb4 authentication,
94 * return 1 on success, 0 on failure, -1 if krb4 is not available
95 */
96int
97auth_krb4_password(Authctxt *authctxt, const char *password)
98{
99 AUTH_DAT adata;
100 KTEXT_ST tkt;
101 struct hostent *hp;
102 struct passwd *pw;
103 char localhost[MAXHOSTNAMELEN], phost[INST_SZ], realm[REALM_SZ];
104 u_int32_t faddr;
105 int r;
106
107 if ((pw = authctxt->pw) == NULL)
108 return (0);
109
110 /*
111 * Try Kerberos password authentication only for non-root
112 * users and only if Kerberos is installed.
113 */
114 if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
115 /* Set up our ticket file. */
116 if (!krb4_init(authctxt)) {
117 log("Couldn't initialize Kerberos ticket file for %s!",
118 pw->pw_name);
119 goto failure;
120 }
121 /* Try to get TGT using our password. */
122 r = krb_get_pw_in_tkt((char *) pw->pw_name, "", realm,
123 "krbtgt", realm, DEFAULT_TKT_LIFE, (char *)password);
124 if (r != INTK_OK) {
125 debug("Kerberos v4 password authentication for %s "
126 "failed: %s", pw->pw_name, krb_err_txt[r]);
127 goto failure;
128 }
129 /* Successful authentication. */
130 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
131
132 /*
133 * Now that we have a TGT, try to get a local
134 * "rcmd" ticket to ensure that we are not talking
135 * to a bogus Kerberos server.
136 */
137 gethostname(localhost, sizeof(localhost));
138 strlcpy(phost, (char *)krb_get_phost(localhost),
139 sizeof(phost));
140 r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
141
142 if (r == KSUCCESS) {
143 if ((hp = gethostbyname(localhost)) == NULL) {
144 log("Couldn't get local host address!");
145 goto failure;
146 }
147 memmove((void *)&faddr, (void *)hp->h_addr,
148 sizeof(faddr));
149
150 /* Verify our "rcmd" ticket. */
151 r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
152 faddr, &adata, "");
153 if (r == RD_AP_UNDEC) {
154 /*
155 * Probably didn't have a srvtab on
156 * localhost. Disallow login.
157 */
158 log("Kerberos v4 TGT for %s unverifiable, "
159 "no srvtab installed? krb_rd_req: %s",
160 pw->pw_name, krb_err_txt[r]);
161 goto failure;
162 } else if (r != KSUCCESS) {
163 log("Kerberos v4 %s ticket unverifiable: %s",
164 KRB4_SERVICE_NAME, krb_err_txt[r]);
165 goto failure;
166 }
167 } else if (r == KDC_PR_UNKNOWN) {
168 /*
169 * Disallow login if no rcmd service exists, and
170 * log the error.
171 */
172 log("Kerberos v4 TGT for %s unverifiable: %s; %s.%s "
173 "not registered, or srvtab is wrong?", pw->pw_name,
174 krb_err_txt[r], KRB4_SERVICE_NAME, phost);
175 goto failure;
176 } else {
177 /*
178 * TGT is bad, forget it. Possibly spoofed!
179 */
180 debug("WARNING: Kerberos v4 TGT possibly spoofed "
181 "for %s: %s", pw->pw_name, krb_err_txt[r]);
182 goto failure;
183 }
184 /* Authentication succeeded. */
185 return (1);
186 } else
187 /* Logging in as root or no local Kerberos realm. */
188 debug("Unable to authenticate to Kerberos.");
189
190 failure:
191 krb4_cleanup_proc(authctxt);
192
193 if (!options.kerberos_or_local_passwd)
194 return (0);
195
196 /* Fall back to ordinary passwd authentication. */
197 return (-1);
198}
199
200void
201krb4_cleanup_proc(void *context)
202{
203 Authctxt *authctxt = (Authctxt *)context;
204 debug("krb4_cleanup_proc called");
205 if (authctxt->krb4_ticket_file) {
206 (void) dest_tkt();
207 xfree(authctxt->krb4_ticket_file);
208 authctxt->krb4_ticket_file = NULL;
209 }
210}
211
212int
213auth_krb4(Authctxt *authctxt, KTEXT auth, char **client, KTEXT reply)
214{
215 AUTH_DAT adat = {0};
216 Key_schedule schedule;
217 struct sockaddr_in local, foreign;
218 char instance[INST_SZ];
219 socklen_t slen;
220 u_int cksum;
221 int r, s;
222
223 s = packet_get_connection_in();
224
225 slen = sizeof(local);
226 memset(&local, 0, sizeof(local));
227 if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
228 debug("getsockname failed: %.100s", strerror(errno));
229 slen = sizeof(foreign);
230 memset(&foreign, 0, sizeof(foreign));
231 if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
232 debug("getpeername failed: %.100s", strerror(errno));
233 fatal_cleanup();
234 }
235 instance[0] = '*';
236 instance[1] = 0;
237
238 /* Get the encrypted request, challenge, and session key. */
239 if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance,
240 0, &adat, ""))) {
241 debug("Kerberos v4 krb_rd_req: %.100s", krb_err_txt[r]);
242 return (0);
243 }
244 des_key_sched((des_cblock *) adat.session, schedule);
245
246 *client = xmalloc(MAX_K_NAME_SZ);
247 (void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
248 *adat.pinst ? "." : "", adat.pinst, adat.prealm);
249
250 /* Check ~/.klogin authorization now. */
251 if (kuserok(&adat, authctxt->user) != KSUCCESS) {
252 log("Kerberos v4 .klogin authorization failed for %s to "
253 "account %s", *client, authctxt->user);
254 xfree(*client);
255 *client = NULL;
256 return (0);
257 }
258 /* Increment the checksum, and return it encrypted with the
259 session key. */
260 cksum = adat.checksum + 1;
261 cksum = htonl(cksum);
262
263 /* If we can't successfully encrypt the checksum, we send back an
264 empty message, admitting our failure. */
265 if ((r = krb_mk_priv((u_char *) & cksum, reply->dat, sizeof(cksum) + 1,
266 schedule, &adat.session, &local, &foreign)) < 0) {
267 debug("Kerberos v4 mk_priv: (%d) %s", r, krb_err_txt[r]);
268 reply->dat[0] = 0;
269 reply->length = 0;
270 } else
271 reply->length = r;
272
273 /* Clear session key. */
274 memset(&adat.session, 0, sizeof(adat.session));
275 return (1);
276}
277#endif /* KRB4 */
278
279#ifdef AFS
280int
281auth_krb4_tgt(Authctxt *authctxt, const char *string)
282{
283 CREDENTIALS creds;
284 struct passwd *pw;
285
286 if ((pw = authctxt->pw) == NULL)
287 goto failure;
288
289 temporarily_use_uid(pw);
290
291 if (!radix_to_creds(string, &creds)) {
292 log("Protocol error decoding Kerberos v4 TGT");
293 goto failure;
294 }
295 if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
296 strlcpy(creds.service, "krbtgt", sizeof creds.service);
297
298 if (strcmp(creds.service, "krbtgt")) {
299 log("Kerberos v4 TGT (%s%s%s@%s) rejected for %s",
300 creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
301 creds.realm, pw->pw_name);
302 goto failure;
303 }
304 if (!krb4_init(authctxt))
305 goto failure;
306
307 if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
308 goto failure;
309
310 if (save_credentials(creds.service, creds.instance, creds.realm,
311 creds.session, creds.lifetime, creds.kvno, &creds.ticket_st,
312 creds.issue_date) != KSUCCESS) {
313 debug("Kerberos v4 TGT refused: couldn't save credentials");
314 goto failure;
315 }
316 /* Successful authentication, passed all checks. */
317 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
318
319 debug("Kerberos v4 TGT accepted (%s%s%s@%s)",
320 creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
321 memset(&creds, 0, sizeof(creds));
322
323 restore_uid();
324
325 return (1);
326
327 failure:
328 krb4_cleanup_proc(authctxt);
329 memset(&creds, 0, sizeof(creds));
330 restore_uid();
331
332 return (0);
333}
334
335int
336auth_afs_token(Authctxt *authctxt, const char *token_string)
337{
338 CREDENTIALS creds;
339 struct passwd *pw;
340 uid_t uid;
341
342 if ((pw = authctxt->pw) == NULL)
343 return (0);
344
345 if (!radix_to_creds(token_string, &creds)) {
346 log("Protocol error decoding AFS token");
347 return (0);
348 }
349 if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
350 strlcpy(creds.service, "afs", sizeof creds.service);
351
352 if (strncmp(creds.pname, "AFS ID ", 7) == 0)
353 uid = atoi(creds.pname + 7);
354 else
355 uid = pw->pw_uid;
356
357 if (kafs_settoken(creds.realm, uid, &creds)) {
358 log("AFS token (%s@%s) rejected for %s",
359 creds.pname, creds.realm, pw->pw_name);
360 memset(&creds, 0, sizeof(creds));
361 return (0);
362 }
363 debug("AFS token accepted (%s@%s)", creds.pname, creds.realm);
364 memset(&creds, 0, sizeof(creds));
365
366 return (1);
367}
368#endif /* AFS */
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