Annotation of src/usr.bin/ssh/auth-krb4.c, Revision 1.11
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:
12: #ifdef KRB4
1.6 markus 13: char *ticket = NULL;
1.11 ! markus 14:
! 15: extern ServerOptions options;
! 16:
! 17: /*
! 18: * try krb4 authentication,
! 19: * return 1 on success, 0 on failure, -1 if krb4 is not available
! 20: */
! 21:
! 22: int
! 23: auth_krb4_password(struct passwd * pw, const char *password)
! 24: {
! 25: AUTH_DAT adata;
! 26: KTEXT_ST tkt;
! 27: struct hostent *hp;
! 28: unsigned long faddr;
! 29: char localhost[MAXHOSTNAMELEN];
! 30: char phost[INST_SZ];
! 31: char realm[REALM_SZ];
! 32: int r;
! 33:
! 34: /*
! 35: * Try Kerberos password authentication only for non-root
! 36: * users and only if Kerberos is installed.
! 37: */
! 38: if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
! 39:
! 40: /* Set up our ticket file. */
! 41: if (!krb4_init(pw->pw_uid)) {
! 42: log("Couldn't initialize Kerberos ticket file for %s!",
! 43: pw->pw_name);
! 44: goto kerberos_auth_failure;
! 45: }
! 46: /* Try to get TGT using our password. */
! 47: r = krb_get_pw_in_tkt((char *) pw->pw_name, "",
! 48: realm, "krbtgt", realm,
! 49: DEFAULT_TKT_LIFE, (char *) password);
! 50: if (r != INTK_OK) {
! 51: packet_send_debug("Kerberos V4 password "
! 52: "authentication for %s failed: %s",
! 53: pw->pw_name, krb_err_txt[r]);
! 54: goto kerberos_auth_failure;
! 55: }
! 56: /* Successful authentication. */
! 57: chown(tkt_string(), pw->pw_uid, pw->pw_gid);
! 58:
! 59: /*
! 60: * Now that we have a TGT, try to get a local
! 61: * "rcmd" ticket to ensure that we are not talking
! 62: * to a bogus Kerberos server.
! 63: */
! 64: (void) gethostname(localhost, sizeof(localhost));
! 65: (void) strlcpy(phost, (char *) krb_get_phost(localhost),
! 66: INST_SZ);
! 67: r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
! 68:
! 69: if (r == KSUCCESS) {
! 70: if (!(hp = gethostbyname(localhost))) {
! 71: log("Couldn't get local host address!");
! 72: goto kerberos_auth_failure;
! 73: }
! 74: memmove((void *) &faddr, (void *) hp->h_addr,
! 75: sizeof(faddr));
! 76:
! 77: /* Verify our "rcmd" ticket. */
! 78: r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
! 79: faddr, &adata, "");
! 80: if (r == RD_AP_UNDEC) {
! 81: /*
! 82: * Probably didn't have a srvtab on
! 83: * localhost. Allow login.
! 84: */
! 85: log("Kerberos V4 TGT for %s unverifiable, "
! 86: "no srvtab installed? krb_rd_req: %s",
! 87: pw->pw_name, krb_err_txt[r]);
! 88: } else if (r != KSUCCESS) {
! 89: log("Kerberos V4 %s ticket unverifiable: %s",
! 90: KRB4_SERVICE_NAME, krb_err_txt[r]);
! 91: goto kerberos_auth_failure;
! 92: }
! 93: } else if (r == KDC_PR_UNKNOWN) {
! 94: /*
! 95: * Allow login if no rcmd service exists, but
! 96: * log the error.
! 97: */
! 98: log("Kerberos V4 TGT for %s unverifiable: %s; %s.%s "
! 99: "not registered, or srvtab is wrong?", pw->pw_name,
! 100: krb_err_txt[r], KRB4_SERVICE_NAME, phost);
! 101: } else {
! 102: /*
! 103: * TGT is bad, forget it. Possibly spoofed!
! 104: */
! 105: packet_send_debug("WARNING: Kerberos V4 TGT "
! 106: "possibly spoofed for %s: %s",
! 107: pw->pw_name, krb_err_txt[r]);
! 108: goto kerberos_auth_failure;
! 109: }
! 110:
! 111: /* Authentication succeeded. */
! 112: return 1;
! 113:
! 114: kerberos_auth_failure:
! 115: krb4_cleanup_proc(NULL);
! 116:
! 117: if (!options.kerberos_or_local_passwd)
! 118: return 0;
! 119: } else {
! 120: /* Logging in as root or no local Kerberos realm. */
! 121: packet_send_debug("Unable to authenticate to Kerberos.");
! 122: }
! 123: /* Fall back to ordinary passwd authentication. */
! 124: return -1;
! 125: }
1.6 markus 126:
127: void
128: krb4_cleanup_proc(void *ignore)
1.1 deraadt 129: {
1.9 markus 130: debug("krb4_cleanup_proc called");
131: if (ticket) {
132: (void) dest_tkt();
133: xfree(ticket);
134: ticket = NULL;
135: }
1.6 markus 136: }
137:
1.9 markus 138: int
139: krb4_init(uid_t uid)
1.6 markus 140: {
1.9 markus 141: static int cleanup_registered = 0;
142: char *tkt_root = TKT_ROOT;
143: struct stat st;
144: int fd;
145:
146: if (!ticket) {
147: /* Set unique ticket string manually since we're still root. */
148: ticket = xmalloc(MAXPATHLEN);
1.1 deraadt 149: #ifdef AFS
1.9 markus 150: if (lstat("/ticket", &st) != -1)
151: tkt_root = "/ticket/";
1.1 deraadt 152: #endif /* AFS */
1.9 markus 153: snprintf(ticket, MAXPATHLEN, "%s%d_%d", tkt_root, uid, getpid());
154: (void) krb_set_tkt_string(ticket);
155: }
156: /* Register ticket cleanup in case of fatal error. */
157: if (!cleanup_registered) {
158: fatal_add_cleanup(krb4_cleanup_proc, NULL);
159: cleanup_registered = 1;
160: }
161: /* Try to create our ticket file. */
162: if ((fd = mkstemp(ticket)) != -1) {
163: close(fd);
164: return 1;
165: }
166: /* Ticket file exists - make sure user owns it (just passed ticket). */
167: if (lstat(ticket, &st) != -1) {
168: if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
169: st.st_uid == uid)
170: return 1;
171: }
172: /* Failure - cancel cleanup function, leaving bad ticket for inspection. */
173: log("WARNING: bad ticket file %s", ticket);
174: fatal_remove_cleanup(krb4_cleanup_proc, NULL);
175: cleanup_registered = 0;
176: xfree(ticket);
177: ticket = NULL;
178:
179: return 0;
1.1 deraadt 180: }
181:
1.9 markus 182: int
183: auth_krb4(const char *server_user, KTEXT auth, char **client)
1.1 deraadt 184: {
1.9 markus 185: AUTH_DAT adat = {0};
186: KTEXT_ST reply;
187: char instance[INST_SZ];
188: int r, s;
189: u_int cksum;
190: Key_schedule schedule;
191: struct sockaddr_in local, foreign;
192:
193: s = packet_get_connection_in();
194:
195: r = sizeof(local);
196: memset(&local, 0, sizeof(local));
197: if (getsockname(s, (struct sockaddr *) & local, &r) < 0)
198: debug("getsockname failed: %.100s", strerror(errno));
199: r = sizeof(foreign);
200: memset(&foreign, 0, sizeof(foreign));
201: if (getpeername(s, (struct sockaddr *) & foreign, &r) < 0) {
202: debug("getpeername failed: %.100s", strerror(errno));
203: fatal_cleanup();
204: }
205: instance[0] = '*';
206: instance[1] = 0;
207:
208: /* Get the encrypted request, challenge, and session key. */
209: if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance, 0, &adat, ""))) {
210: packet_send_debug("Kerberos V4 krb_rd_req: %.100s", krb_err_txt[r]);
211: return 0;
212: }
213: des_key_sched((des_cblock *) adat.session, schedule);
214:
215: *client = xmalloc(MAX_K_NAME_SZ);
216: (void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
1.10 deraadt 217: *adat.pinst ? "." : "", adat.pinst, adat.prealm);
1.9 markus 218:
219: /* Check ~/.klogin authorization now. */
220: if (kuserok(&adat, (char *) server_user) != KSUCCESS) {
221: packet_send_debug("Kerberos V4 .klogin authorization failed!");
222: log("Kerberos V4 .klogin authorization failed for %s to account %s",
223: *client, server_user);
224: xfree(*client);
225: return 0;
226: }
227: /* Increment the checksum, and return it encrypted with the
228: session key. */
229: cksum = adat.checksum + 1;
230: cksum = htonl(cksum);
231:
232: /* If we can't successfully encrypt the checksum, we send back an
233: empty message, admitting our failure. */
234: if ((r = krb_mk_priv((u_char *) & cksum, reply.dat, sizeof(cksum) + 1,
1.10 deraadt 235: schedule, &adat.session, &local, &foreign)) < 0) {
1.9 markus 236: packet_send_debug("Kerberos V4 mk_priv: (%d) %s", r, krb_err_txt[r]);
237: reply.dat[0] = 0;
238: reply.length = 0;
239: } else
240: reply.length = r;
241:
242: /* Clear session key. */
243: memset(&adat.session, 0, sizeof(&adat.session));
244:
245: packet_start(SSH_SMSG_AUTH_KERBEROS_RESPONSE);
246: packet_put_string((char *) reply.dat, reply.length);
247: packet_send();
248: packet_write_wait();
249: return 1;
1.1 deraadt 250: }
251: #endif /* KRB4 */
252:
253: #ifdef AFS
1.9 markus 254: int
255: auth_kerberos_tgt(struct passwd *pw, const char *string)
1.1 deraadt 256: {
1.9 markus 257: CREDENTIALS creds;
258:
259: if (!radix_to_creds(string, &creds)) {
260: log("Protocol error decoding Kerberos V4 tgt");
261: packet_send_debug("Protocol error decoding Kerberos V4 tgt");
262: goto auth_kerberos_tgt_failure;
263: }
264: if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
265: strlcpy(creds.service, "krbtgt", sizeof creds.service);
266:
267: if (strcmp(creds.service, "krbtgt")) {
268: log("Kerberos V4 tgt (%s%s%s@%s) rejected for %s", creds.pname,
1.10 deraadt 269: creds.pinst[0] ? "." : "", creds.pinst, creds.realm,
270: pw->pw_name);
1.9 markus 271: packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for %s",
1.10 deraadt 272: creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
273: creds.realm, pw->pw_name);
1.9 markus 274: goto auth_kerberos_tgt_failure;
275: }
276: if (!krb4_init(pw->pw_uid))
277: goto auth_kerberos_tgt_failure;
278:
279: if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
280: goto auth_kerberos_tgt_failure;
281:
282: if (save_credentials(creds.service, creds.instance, creds.realm,
1.10 deraadt 283: creds.session, creds.lifetime, creds.kvno,
284: &creds.ticket_st, creds.issue_date) != KSUCCESS) {
1.9 markus 285: packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
286: goto auth_kerberos_tgt_failure;
287: }
288: /* Successful authentication, passed all checks. */
289: chown(tkt_string(), pw->pw_uid, pw->pw_gid);
290:
291: packet_send_debug("Kerberos V4 tgt accepted (%s.%s@%s, %s%s%s@%s)",
1.10 deraadt 292: creds.service, creds.instance, creds.realm, creds.pname,
293: creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
1.9 markus 294: memset(&creds, 0, sizeof(creds));
295: packet_start(SSH_SMSG_SUCCESS);
296: packet_send();
297: packet_write_wait();
298: return 1;
299:
300: auth_kerberos_tgt_failure:
301: krb4_cleanup_proc(NULL);
302: memset(&creds, 0, sizeof(creds));
303: packet_start(SSH_SMSG_FAILURE);
304: packet_send();
305: packet_write_wait();
306: return 0;
1.1 deraadt 307: }
308:
1.9 markus 309: int
310: auth_afs_token(struct passwd *pw, const char *token_string)
1.1 deraadt 311: {
1.9 markus 312: CREDENTIALS creds;
313: uid_t uid = pw->pw_uid;
1.1 deraadt 314:
1.9 markus 315: if (!radix_to_creds(token_string, &creds)) {
316: log("Protocol error decoding AFS token");
317: packet_send_debug("Protocol error decoding AFS token");
318: packet_start(SSH_SMSG_FAILURE);
319: packet_send();
320: packet_write_wait();
321: return 0;
322: }
323: if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
324: strlcpy(creds.service, "afs", sizeof creds.service);
325:
326: if (strncmp(creds.pname, "AFS ID ", 7) == 0)
327: uid = atoi(creds.pname + 7);
328:
329: if (kafs_settoken(creds.realm, uid, &creds)) {
330: log("AFS token (%s@%s) rejected for %s", creds.pname, creds.realm,
331: pw->pw_name);
332: packet_send_debug("AFS token (%s@%s) rejected for %s", creds.pname,
1.10 deraadt 333: creds.realm, pw->pw_name);
1.9 markus 334: memset(&creds, 0, sizeof(creds));
335: packet_start(SSH_SMSG_FAILURE);
336: packet_send();
337: packet_write_wait();
338: return 0;
339: }
340: packet_send_debug("AFS token accepted (%s@%s, %s@%s)", creds.service,
1.10 deraadt 341: creds.realm, creds.pname, creds.realm);
1.9 markus 342: memset(&creds, 0, sizeof(creds));
343: packet_start(SSH_SMSG_SUCCESS);
344: packet_send();
345: packet_write_wait();
346: return 1;
1.1 deraadt 347: }
348: #endif /* AFS */
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