Annotation of src/usr.bin/ssh/auth-krb4.c, Revision 1.15
1.1 deraadt 1: /*
1.10 deraadt 2: * Dug Song <dugsong@UMICH.EDU>
3: * Kerberos v4 authentication and ticket-passing routines.
4: */
1.1 deraadt 5:
6: #include "includes.h"
7: #include "packet.h"
8: #include "xmalloc.h"
9: #include "ssh.h"
1.11 markus 10: #include "servconf.h"
1.1 deraadt 11:
1.15 ! djm 12: RCSID("$OpenBSD$");
! 13:
1.1 deraadt 14: #ifdef KRB4
1.6 markus 15: char *ticket = NULL;
1.11 markus 16:
17: extern ServerOptions options;
18:
19: /*
20: * try krb4 authentication,
21: * return 1 on success, 0 on failure, -1 if krb4 is not available
22: */
23:
1.14 markus 24: int
1.11 markus 25: auth_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
85: * localhost. Allow login.
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]);
90: } else if (r != KSUCCESS) {
91: log("Kerberos V4 %s ticket unverifiable: %s",
92: KRB4_SERVICE_NAME, krb_err_txt[r]);
93: goto kerberos_auth_failure;
94: }
95: } else if (r == KDC_PR_UNKNOWN) {
96: /*
97: * Allow login if no rcmd service exists, but
98: * log the error.
99: */
100: log("Kerberos V4 TGT for %s unverifiable: %s; %s.%s "
101: "not registered, or srvtab is wrong?", pw->pw_name,
102: krb_err_txt[r], KRB4_SERVICE_NAME, phost);
103: } else {
104: /*
105: * TGT is bad, forget it. Possibly spoofed!
106: */
107: packet_send_debug("WARNING: Kerberos V4 TGT "
108: "possibly spoofed for %s: %s",
109: pw->pw_name, krb_err_txt[r]);
110: goto kerberos_auth_failure;
111: }
112:
113: /* Authentication succeeded. */
114: return 1;
115:
116: kerberos_auth_failure:
117: krb4_cleanup_proc(NULL);
118:
119: if (!options.kerberos_or_local_passwd)
120: return 0;
121: } else {
122: /* Logging in as root or no local Kerberos realm. */
123: packet_send_debug("Unable to authenticate to Kerberos.");
124: }
125: /* Fall back to ordinary passwd authentication. */
126: return -1;
127: }
1.6 markus 128:
129: void
130: krb4_cleanup_proc(void *ignore)
1.1 deraadt 131: {
1.9 markus 132: debug("krb4_cleanup_proc called");
133: if (ticket) {
134: (void) dest_tkt();
135: xfree(ticket);
136: ticket = NULL;
137: }
1.6 markus 138: }
139:
1.14 markus 140: int
1.9 markus 141: krb4_init(uid_t uid)
1.6 markus 142: {
1.9 markus 143: static int cleanup_registered = 0;
1.13 markus 144: const char *tkt_root = TKT_ROOT;
1.9 markus 145: struct stat st;
146: int fd;
147:
148: if (!ticket) {
149: /* Set unique ticket string manually since we're still root. */
150: ticket = xmalloc(MAXPATHLEN);
1.1 deraadt 151: #ifdef AFS
1.9 markus 152: if (lstat("/ticket", &st) != -1)
153: tkt_root = "/ticket/";
1.1 deraadt 154: #endif /* AFS */
1.9 markus 155: snprintf(ticket, MAXPATHLEN, "%s%d_%d", tkt_root, uid, getpid());
156: (void) krb_set_tkt_string(ticket);
157: }
158: /* Register ticket cleanup in case of fatal error. */
159: if (!cleanup_registered) {
160: fatal_add_cleanup(krb4_cleanup_proc, NULL);
161: cleanup_registered = 1;
162: }
163: /* Try to create our ticket file. */
164: if ((fd = mkstemp(ticket)) != -1) {
165: close(fd);
166: return 1;
167: }
168: /* Ticket file exists - make sure user owns it (just passed ticket). */
169: if (lstat(ticket, &st) != -1) {
170: if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
171: st.st_uid == uid)
172: return 1;
173: }
174: /* Failure - cancel cleanup function, leaving bad ticket for inspection. */
175: log("WARNING: bad ticket file %s", ticket);
176: fatal_remove_cleanup(krb4_cleanup_proc, NULL);
177: cleanup_registered = 0;
178: xfree(ticket);
179: ticket = NULL;
180:
181: return 0;
1.1 deraadt 182: }
183:
1.14 markus 184: int
1.9 markus 185: auth_krb4(const char *server_user, KTEXT auth, char **client)
1.1 deraadt 186: {
1.9 markus 187: AUTH_DAT adat = {0};
188: KTEXT_ST reply;
189: char instance[INST_SZ];
190: int r, s;
1.12 markus 191: socklen_t slen;
1.9 markus 192: u_int cksum;
193: Key_schedule schedule;
194: struct sockaddr_in local, foreign;
195:
196: s = packet_get_connection_in();
197:
1.12 markus 198: slen = sizeof(local);
1.9 markus 199: memset(&local, 0, sizeof(local));
1.12 markus 200: if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
1.9 markus 201: debug("getsockname failed: %.100s", strerror(errno));
1.12 markus 202: slen = sizeof(foreign);
1.9 markus 203: memset(&foreign, 0, sizeof(foreign));
1.12 markus 204: if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
1.9 markus 205: debug("getpeername failed: %.100s", strerror(errno));
206: fatal_cleanup();
207: }
208: instance[0] = '*';
209: instance[1] = 0;
210:
211: /* Get the encrypted request, challenge, and session key. */
212: if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance, 0, &adat, ""))) {
213: packet_send_debug("Kerberos V4 krb_rd_req: %.100s", krb_err_txt[r]);
214: return 0;
215: }
216: des_key_sched((des_cblock *) adat.session, schedule);
217:
218: *client = xmalloc(MAX_K_NAME_SZ);
219: (void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
1.10 deraadt 220: *adat.pinst ? "." : "", adat.pinst, adat.prealm);
1.9 markus 221:
222: /* Check ~/.klogin authorization now. */
223: if (kuserok(&adat, (char *) server_user) != KSUCCESS) {
224: packet_send_debug("Kerberos V4 .klogin authorization failed!");
225: log("Kerberos V4 .klogin authorization failed for %s to account %s",
226: *client, server_user);
227: xfree(*client);
228: return 0;
229: }
230: /* Increment the checksum, and return it encrypted with the
231: session key. */
232: cksum = adat.checksum + 1;
233: cksum = htonl(cksum);
234:
235: /* If we can't successfully encrypt the checksum, we send back an
236: empty message, admitting our failure. */
237: if ((r = krb_mk_priv((u_char *) & cksum, reply.dat, sizeof(cksum) + 1,
1.10 deraadt 238: schedule, &adat.session, &local, &foreign)) < 0) {
1.9 markus 239: packet_send_debug("Kerberos V4 mk_priv: (%d) %s", r, krb_err_txt[r]);
240: reply.dat[0] = 0;
241: reply.length = 0;
242: } else
243: reply.length = r;
244:
245: /* Clear session key. */
246: memset(&adat.session, 0, sizeof(&adat.session));
247:
248: packet_start(SSH_SMSG_AUTH_KERBEROS_RESPONSE);
249: packet_put_string((char *) reply.dat, reply.length);
250: packet_send();
251: packet_write_wait();
252: return 1;
1.1 deraadt 253: }
254: #endif /* KRB4 */
255:
256: #ifdef AFS
1.14 markus 257: int
1.9 markus 258: auth_kerberos_tgt(struct passwd *pw, const char *string)
1.1 deraadt 259: {
1.9 markus 260: CREDENTIALS creds;
261:
262: if (!radix_to_creds(string, &creds)) {
263: log("Protocol error decoding Kerberos V4 tgt");
264: packet_send_debug("Protocol error decoding Kerberos V4 tgt");
265: goto auth_kerberos_tgt_failure;
266: }
267: if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
268: strlcpy(creds.service, "krbtgt", sizeof creds.service);
269:
270: if (strcmp(creds.service, "krbtgt")) {
271: log("Kerberos V4 tgt (%s%s%s@%s) rejected for %s", creds.pname,
1.10 deraadt 272: creds.pinst[0] ? "." : "", creds.pinst, creds.realm,
273: pw->pw_name);
1.9 markus 274: packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for %s",
1.10 deraadt 275: creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
276: creds.realm, pw->pw_name);
1.9 markus 277: goto auth_kerberos_tgt_failure;
278: }
279: if (!krb4_init(pw->pw_uid))
280: goto auth_kerberos_tgt_failure;
281:
282: if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
283: goto auth_kerberos_tgt_failure;
284:
285: if (save_credentials(creds.service, creds.instance, creds.realm,
1.10 deraadt 286: creds.session, creds.lifetime, creds.kvno,
287: &creds.ticket_st, creds.issue_date) != KSUCCESS) {
1.9 markus 288: packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
289: goto auth_kerberos_tgt_failure;
290: }
291: /* Successful authentication, passed all checks. */
292: chown(tkt_string(), pw->pw_uid, pw->pw_gid);
293:
294: packet_send_debug("Kerberos V4 tgt accepted (%s.%s@%s, %s%s%s@%s)",
1.10 deraadt 295: creds.service, creds.instance, creds.realm, creds.pname,
296: creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
1.9 markus 297: memset(&creds, 0, sizeof(creds));
298: packet_start(SSH_SMSG_SUCCESS);
299: packet_send();
300: packet_write_wait();
301: return 1;
302:
303: auth_kerberos_tgt_failure:
304: krb4_cleanup_proc(NULL);
305: memset(&creds, 0, sizeof(creds));
306: packet_start(SSH_SMSG_FAILURE);
307: packet_send();
308: packet_write_wait();
309: return 0;
1.1 deraadt 310: }
311:
1.14 markus 312: int
1.9 markus 313: auth_afs_token(struct passwd *pw, const char *token_string)
1.1 deraadt 314: {
1.9 markus 315: CREDENTIALS creds;
316: uid_t uid = pw->pw_uid;
1.1 deraadt 317:
1.9 markus 318: if (!radix_to_creds(token_string, &creds)) {
319: log("Protocol error decoding AFS token");
320: packet_send_debug("Protocol error decoding AFS token");
321: packet_start(SSH_SMSG_FAILURE);
322: packet_send();
323: packet_write_wait();
324: return 0;
325: }
326: if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
327: strlcpy(creds.service, "afs", sizeof creds.service);
328:
329: if (strncmp(creds.pname, "AFS ID ", 7) == 0)
330: uid = atoi(creds.pname + 7);
331:
332: if (kafs_settoken(creds.realm, uid, &creds)) {
333: log("AFS token (%s@%s) rejected for %s", creds.pname, creds.realm,
334: pw->pw_name);
335: packet_send_debug("AFS token (%s@%s) rejected for %s", creds.pname,
1.10 deraadt 336: creds.realm, pw->pw_name);
1.9 markus 337: memset(&creds, 0, sizeof(creds));
338: packet_start(SSH_SMSG_FAILURE);
339: packet_send();
340: packet_write_wait();
341: return 0;
342: }
343: packet_send_debug("AFS token accepted (%s@%s, %s@%s)", creds.service,
1.10 deraadt 344: creds.realm, creds.pname, creds.realm);
1.9 markus 345: memset(&creds, 0, sizeof(creds));
346: packet_start(SSH_SMSG_SUCCESS);
347: packet_send();
348: packet_write_wait();
349: return 1;
1.1 deraadt 350: }
351: #endif /* AFS */
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