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8efc0c15 1/*
5260325f 2 * Dug Song <dugsong@UMICH.EDU>
3 * Kerberos v4 authentication and ticket-passing routines.
4 */
8efc0c15 5
6#include "includes.h"
7#include "packet.h"
8#include "xmalloc.h"
9#include "ssh.h"
57112b5a 10#include "servconf.h"
8efc0c15 11
14a9a859 12RCSID("$OpenBSD: auth-krb4.c,v 1.17 2000/08/28 03:50:54 deraadt Exp $");
e5a0294f 13
8efc0c15 14#ifdef KRB4
6a17f9c2 15char *ticket = NULL;
16
57112b5a 17extern ServerOptions options;
18
19/*
20 * try krb4 authentication,
21 * return 1 on success, 0 on failure, -1 if krb4 is not available
22 */
23
6ae2364d 24int
57112b5a 25auth_krb4_password(struct passwd * pw, const char *password)
26{
27 AUTH_DAT adata;
28 KTEXT_ST tkt;
29 struct hostent *hp;
30 unsigned long faddr;
31 char localhost[MAXHOSTNAMELEN];
32 char phost[INST_SZ];
33 char realm[REALM_SZ];
34 int r;
35
36 /*
37 * Try Kerberos password authentication only for non-root
38 * users and only if Kerberos is installed.
39 */
40 if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
41
42 /* Set up our ticket file. */
43 if (!krb4_init(pw->pw_uid)) {
44 log("Couldn't initialize Kerberos ticket file for %s!",
45 pw->pw_name);
46 goto kerberos_auth_failure;
47 }
48 /* Try to get TGT using our password. */
49 r = krb_get_pw_in_tkt((char *) pw->pw_name, "",
50 realm, "krbtgt", realm,
51 DEFAULT_TKT_LIFE, (char *) password);
52 if (r != INTK_OK) {
53 packet_send_debug("Kerberos V4 password "
54 "authentication for %s failed: %s",
55 pw->pw_name, krb_err_txt[r]);
56 goto kerberos_auth_failure;
57 }
58 /* Successful authentication. */
59 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
60
61 /*
62 * Now that we have a TGT, try to get a local
63 * "rcmd" ticket to ensure that we are not talking
64 * to a bogus Kerberos server.
65 */
66 (void) gethostname(localhost, sizeof(localhost));
67 (void) strlcpy(phost, (char *) krb_get_phost(localhost),
68 INST_SZ);
69 r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
70
71 if (r == KSUCCESS) {
72 if (!(hp = gethostbyname(localhost))) {
73 log("Couldn't get local host address!");
74 goto kerberos_auth_failure;
75 }
76 memmove((void *) &faddr, (void *) hp->h_addr,
77 sizeof(faddr));
78
79 /* Verify our "rcmd" ticket. */
80 r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
81 faddr, &adata, "");
82 if (r == RD_AP_UNDEC) {
83 /*
84 * Probably didn't have a srvtab on
c345cf9d 85 * localhost. Disallow login.
57112b5a 86 */
87 log("Kerberos V4 TGT for %s unverifiable, "
88 "no srvtab installed? krb_rd_req: %s",
89 pw->pw_name, krb_err_txt[r]);
c345cf9d 90 goto kerberos_auth_failure;
57112b5a 91 } else if (r != KSUCCESS) {
92 log("Kerberos V4 %s ticket unverifiable: %s",
93 KRB4_SERVICE_NAME, krb_err_txt[r]);
94 goto kerberos_auth_failure;
95 }
96 } else if (r == KDC_PR_UNKNOWN) {
97 /*
c345cf9d 98 * Disallow login if no rcmd service exists, and
57112b5a 99 * log the error.
100 */
101 log("Kerberos V4 TGT for %s unverifiable: %s; %s.%s "
102 "not registered, or srvtab is wrong?", pw->pw_name,
103 krb_err_txt[r], KRB4_SERVICE_NAME, phost);
c345cf9d 104 goto kerberos_auth_failure;
57112b5a 105 } else {
106 /*
107 * TGT is bad, forget it. Possibly spoofed!
108 */
109 packet_send_debug("WARNING: Kerberos V4 TGT "
110 "possibly spoofed for %s: %s",
111 pw->pw_name, krb_err_txt[r]);
112 goto kerberos_auth_failure;
113 }
114
115 /* Authentication succeeded. */
116 return 1;
117
118kerberos_auth_failure:
119 krb4_cleanup_proc(NULL);
120
121 if (!options.kerberos_or_local_passwd)
122 return 0;
123 } else {
124 /* Logging in as root or no local Kerberos realm. */
125 packet_send_debug("Unable to authenticate to Kerberos.");
126 }
127 /* Fall back to ordinary passwd authentication. */
128 return -1;
129}
130
6a17f9c2 131void
132krb4_cleanup_proc(void *ignore)
133{
5260325f 134 debug("krb4_cleanup_proc called");
135 if (ticket) {
136 (void) dest_tkt();
137 xfree(ticket);
138 ticket = NULL;
139 }
6a17f9c2 140}
141
6ae2364d 142int
5260325f 143krb4_init(uid_t uid)
8efc0c15 144{
5260325f 145 static int cleanup_registered = 0;
4fe2af09 146 const char *tkt_root = TKT_ROOT;
5260325f 147 struct stat st;
148 int fd;
149
150 if (!ticket) {
151 /* Set unique ticket string manually since we're still root. */
152 ticket = xmalloc(MAXPATHLEN);
8efc0c15 153#ifdef AFS
5260325f 154 if (lstat("/ticket", &st) != -1)
155 tkt_root = "/ticket/";
8efc0c15 156#endif /* AFS */
14a9a859 157 snprintf(ticket, MAXPATHLEN, "%s%u_%d", tkt_root, uid, getpid());
5260325f 158 (void) krb_set_tkt_string(ticket);
159 }
160 /* Register ticket cleanup in case of fatal error. */
161 if (!cleanup_registered) {
162 fatal_add_cleanup(krb4_cleanup_proc, NULL);
163 cleanup_registered = 1;
164 }
165 /* Try to create our ticket file. */
166 if ((fd = mkstemp(ticket)) != -1) {
167 close(fd);
168 return 1;
169 }
170 /* Ticket file exists - make sure user owns it (just passed ticket). */
171 if (lstat(ticket, &st) != -1) {
172 if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
173 st.st_uid == uid)
174 return 1;
175 }
176 /* Failure - cancel cleanup function, leaving bad ticket for inspection. */
177 log("WARNING: bad ticket file %s", ticket);
178 fatal_remove_cleanup(krb4_cleanup_proc, NULL);
179 cleanup_registered = 0;
180 xfree(ticket);
181 ticket = NULL;
182
183 return 0;
8efc0c15 184}
185
6ae2364d 186int
5260325f 187auth_krb4(const char *server_user, KTEXT auth, char **client)
8efc0c15 188{
5260325f 189 AUTH_DAT adat = {0};
190 KTEXT_ST reply;
191 char instance[INST_SZ];
192 int r, s;
610cd5c6 193 socklen_t slen;
5260325f 194 u_int cksum;
195 Key_schedule schedule;
196 struct sockaddr_in local, foreign;
197
198 s = packet_get_connection_in();
199
610cd5c6 200 slen = sizeof(local);
5260325f 201 memset(&local, 0, sizeof(local));
610cd5c6 202 if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
5260325f 203 debug("getsockname failed: %.100s", strerror(errno));
610cd5c6 204 slen = sizeof(foreign);
5260325f 205 memset(&foreign, 0, sizeof(foreign));
610cd5c6 206 if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
5260325f 207 debug("getpeername failed: %.100s", strerror(errno));
208 fatal_cleanup();
209 }
210 instance[0] = '*';
211 instance[1] = 0;
212
213 /* Get the encrypted request, challenge, and session key. */
214 if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance, 0, &adat, ""))) {
215 packet_send_debug("Kerberos V4 krb_rd_req: %.100s", krb_err_txt[r]);
216 return 0;
217 }
218 des_key_sched((des_cblock *) adat.session, schedule);
219
220 *client = xmalloc(MAX_K_NAME_SZ);
221 (void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
222 *adat.pinst ? "." : "", adat.pinst, adat.prealm);
223
224 /* Check ~/.klogin authorization now. */
225 if (kuserok(&adat, (char *) server_user) != KSUCCESS) {
226 packet_send_debug("Kerberos V4 .klogin authorization failed!");
227 log("Kerberos V4 .klogin authorization failed for %s to account %s",
228 *client, server_user);
229 xfree(*client);
230 return 0;
231 }
232 /* Increment the checksum, and return it encrypted with the
233 session key. */
234 cksum = adat.checksum + 1;
235 cksum = htonl(cksum);
236
237 /* If we can't successfully encrypt the checksum, we send back an
238 empty message, admitting our failure. */
239 if ((r = krb_mk_priv((u_char *) & cksum, reply.dat, sizeof(cksum) + 1,
240 schedule, &adat.session, &local, &foreign)) < 0) {
241 packet_send_debug("Kerberos V4 mk_priv: (%d) %s", r, krb_err_txt[r]);
242 reply.dat[0] = 0;
243 reply.length = 0;
244 } else
245 reply.length = r;
246
247 /* Clear session key. */
248 memset(&adat.session, 0, sizeof(&adat.session));
249
250 packet_start(SSH_SMSG_AUTH_KERBEROS_RESPONSE);
251 packet_put_string((char *) reply.dat, reply.length);
252 packet_send();
253 packet_write_wait();
254 return 1;
8efc0c15 255}
256#endif /* KRB4 */
257
258#ifdef AFS
6ae2364d 259int
5260325f 260auth_kerberos_tgt(struct passwd *pw, const char *string)
8efc0c15 261{
5260325f 262 CREDENTIALS creds;
263
264 if (!radix_to_creds(string, &creds)) {
265 log("Protocol error decoding Kerberos V4 tgt");
266 packet_send_debug("Protocol error decoding Kerberos V4 tgt");
267 goto auth_kerberos_tgt_failure;
268 }
269 if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
270 strlcpy(creds.service, "krbtgt", sizeof creds.service);
271
272 if (strcmp(creds.service, "krbtgt")) {
273 log("Kerberos V4 tgt (%s%s%s@%s) rejected for %s", creds.pname,
274 creds.pinst[0] ? "." : "", creds.pinst, creds.realm,
275 pw->pw_name);
276 packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for %s",
277 creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
278 creds.realm, pw->pw_name);
279 goto auth_kerberos_tgt_failure;
280 }
281 if (!krb4_init(pw->pw_uid))
282 goto auth_kerberos_tgt_failure;
283
284 if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
285 goto auth_kerberos_tgt_failure;
286
287 if (save_credentials(creds.service, creds.instance, creds.realm,
288 creds.session, creds.lifetime, creds.kvno,
289 &creds.ticket_st, creds.issue_date) != KSUCCESS) {
290 packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
291 goto auth_kerberos_tgt_failure;
292 }
293 /* Successful authentication, passed all checks. */
294 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
295
296 packet_send_debug("Kerberos V4 tgt accepted (%s.%s@%s, %s%s%s@%s)",
297 creds.service, creds.instance, creds.realm, creds.pname,
298 creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
299 memset(&creds, 0, sizeof(creds));
300 packet_start(SSH_SMSG_SUCCESS);
301 packet_send();
302 packet_write_wait();
303 return 1;
304
305auth_kerberos_tgt_failure:
306 krb4_cleanup_proc(NULL);
307 memset(&creds, 0, sizeof(creds));
308 packet_start(SSH_SMSG_FAILURE);
309 packet_send();
310 packet_write_wait();
311 return 0;
8efc0c15 312}
313
6ae2364d 314int
5260325f 315auth_afs_token(struct passwd *pw, const char *token_string)
8efc0c15 316{
5260325f 317 CREDENTIALS creds;
318 uid_t uid = pw->pw_uid;
319
320 if (!radix_to_creds(token_string, &creds)) {
321 log("Protocol error decoding AFS token");
322 packet_send_debug("Protocol error decoding AFS token");
323 packet_start(SSH_SMSG_FAILURE);
324 packet_send();
325 packet_write_wait();
326 return 0;
327 }
328 if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
329 strlcpy(creds.service, "afs", sizeof creds.service);
330
331 if (strncmp(creds.pname, "AFS ID ", 7) == 0)
332 uid = atoi(creds.pname + 7);
333
334 if (kafs_settoken(creds.realm, uid, &creds)) {
335 log("AFS token (%s@%s) rejected for %s", creds.pname, creds.realm,
336 pw->pw_name);
337 packet_send_debug("AFS token (%s@%s) rejected for %s", creds.pname,
338 creds.realm, pw->pw_name);
339 memset(&creds, 0, sizeof(creds));
340 packet_start(SSH_SMSG_FAILURE);
341 packet_send();
342 packet_write_wait();
343 return 0;
344 }
345 packet_send_debug("AFS token accepted (%s@%s, %s@%s)", creds.service,
346 creds.realm, creds.pname, creds.realm);
347 memset(&creds, 0, sizeof(creds));
348 packet_start(SSH_SMSG_SUCCESS);
349 packet_send();
350 packet_write_wait();
351 return 1;
8efc0c15 352}
353#endif /* AFS */
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