auth-krb4.c - third_party/openssh-portable - Git at Google

 /*
  * Copyright (c) 1999 Dug Song.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "includes.h"
 RCSID("$OpenBSD: auth-krb4.c,v 1.28 2002/09/26 11:38:43 markus Exp $");

 #include "ssh.h"
 #include "ssh1.h"
 #include "packet.h"
 #include "xmalloc.h"
 #include "log.h"
 #include "servconf.h"
 #include "uidswap.h"
 #include "auth.h"

 #ifdef AFS
 #include "radix.h"
 #endif

 #ifdef KRB4
 extern ServerOptions options;

 static int
 krb4_init(void *context)
 {
 	static int cleanup_registered = 0;
 	Authctxt *authctxt = (Authctxt *)context;
 	const char *tkt_root = TKT_ROOT;
 	struct stat st;
 	int fd;

 	if (!authctxt->krb4_ticket_file) {
 		/* Set unique ticket string manually since we're still root. */
 		authctxt->krb4_ticket_file = xmalloc(MAXPATHLEN);
 #ifdef AFS
 		if (lstat("/ticket", &st) != -1)
 			tkt_root = "/ticket/";
 #endif /* AFS */
 		snprintf(authctxt->krb4_ticket_file, MAXPATHLEN, "%s%u_%ld",
 		    tkt_root, authctxt->pw->pw_uid, (long)getpid());
 		krb_set_tkt_string(authctxt->krb4_ticket_file);
 	}
 	/* Register ticket cleanup in case of fatal error. */
 	if (!cleanup_registered) {
 		fatal_add_cleanup(krb4_cleanup_proc, authctxt);
 		cleanup_registered = 1;
 	}
 	/* Try to create our ticket file. */
 	if ((fd = mkstemp(authctxt->krb4_ticket_file)) != -1) {
 		close(fd);
 		return (1);
 	}
 	/* Ticket file exists - make sure user owns it (just passed ticket). */
 	if (lstat(authctxt->krb4_ticket_file, &st) != -1) {
 		if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
 		    st.st_uid == authctxt->pw->pw_uid)
 			return (1);
 	}
 	/* Failure - cancel cleanup function, leaving ticket for inspection. */
 	log("WARNING: bad ticket file %s", authctxt->krb4_ticket_file);

 	fatal_remove_cleanup(krb4_cleanup_proc, authctxt);
 	cleanup_registered = 0;

 	xfree(authctxt->krb4_ticket_file);
 	authctxt->krb4_ticket_file = NULL;

 	return (0);
 }

 /*
  * try krb4 authentication,
  * return 1 on success, 0 on failure, -1 if krb4 is not available
  */
 int
 auth_krb4_password(Authctxt *authctxt, const char *password)
 {
 	AUTH_DAT adata;
 	KTEXT_ST tkt;
 	struct hostent *hp;
 	struct passwd *pw;
 	char localhost[MAXHOSTNAMELEN], phost[INST_SZ], realm[REALM_SZ];
 	u_int32_t faddr;
 	int r;

 	if ((pw = authctxt->pw) == NULL)
 		return (0);

 	/*
 	 * Try Kerberos password authentication only for non-root
 	 * users and only if Kerberos is installed.
 	 */
 	if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
 		/* Set up our ticket file. */
 		if (!krb4_init(authctxt)) {
 			log("Couldn't initialize Kerberos ticket file for %s!",
 			    pw->pw_name);
 			goto failure;
 		}
 		/* Try to get TGT using our password. */
 		r = krb_get_pw_in_tkt((char *) pw->pw_name, "", realm,
 		    "krbtgt", realm, DEFAULT_TKT_LIFE, (char *)password);
 		if (r != INTK_OK) {
 			debug("Kerberos v4 password authentication for %s "
 			    "failed: %s", pw->pw_name, krb_err_txt[r]);
 			goto failure;
 		}
 		/* Successful authentication. */
 		chown(tkt_string(), pw->pw_uid, pw->pw_gid);

 		/*
 		 * Now that we have a TGT, try to get a local
 		 * "rcmd" ticket to ensure that we are not talking
 		 * to a bogus Kerberos server.
 		 */
 		gethostname(localhost, sizeof(localhost));
 		strlcpy(phost, (char *)krb_get_phost(localhost),
 		    sizeof(phost));
 		r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);

 		if (r == KSUCCESS) {
 			if ((hp = gethostbyname(localhost)) == NULL) {
 				log("Couldn't get local host address!");
 				goto failure;
 			}
 			memmove((void *)&faddr, (void *)hp->h_addr,
 			    sizeof(faddr));

 			/* Verify our "rcmd" ticket. */
 			r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
 			    faddr, &adata, "");
 			if (r == RD_AP_UNDEC) {
 				/*
 				 * Probably didn't have a srvtab on
 				 * localhost. Disallow login.
 				 */
 				log("Kerberos v4 TGT for %s unverifiable, "
 				    "no srvtab installed? krb_rd_req: %s",
 				    pw->pw_name, krb_err_txt[r]);
 				goto failure;
 			} else if (r != KSUCCESS) {
 				log("Kerberos v4 %s ticket unverifiable: %s",
 				    KRB4_SERVICE_NAME, krb_err_txt[r]);
 				goto failure;
 			}
 		} else if (r == KDC_PR_UNKNOWN) {
 			/*
 			 * Disallow login if no rcmd service exists, and
 			 * log the error.
 			 */
 			log("Kerberos v4 TGT for %s unverifiable: %s; %s.%s "
 			    "not registered, or srvtab is wrong?", pw->pw_name,
 			    krb_err_txt[r], KRB4_SERVICE_NAME, phost);
 			goto failure;
 		} else {
 			/*
 			 * TGT is bad, forget it. Possibly spoofed!
 			 */
 			debug("WARNING: Kerberos v4 TGT possibly spoofed "
 			    "for %s: %s", pw->pw_name, krb_err_txt[r]);
 			goto failure;
 		}
 		/* Authentication succeeded. */
 		return (1);
 	} else
 		/* Logging in as root or no local Kerberos realm. */
 		debug("Unable to authenticate to Kerberos.");

  failure:
 	krb4_cleanup_proc(authctxt);

 	if (!options.kerberos_or_local_passwd)
 		return (0);

 	/* Fall back to ordinary passwd authentication. */
 	return (-1);
 }

 void
 krb4_cleanup_proc(void *context)
 {
 	Authctxt *authctxt = (Authctxt *)context;
 	debug("krb4_cleanup_proc called");
 	if (authctxt->krb4_ticket_file) {
 		(void) dest_tkt();
 		xfree(authctxt->krb4_ticket_file);
 		authctxt->krb4_ticket_file = NULL;
 	}
 }

 int
 auth_krb4(Authctxt *authctxt, KTEXT auth, char **client, KTEXT reply)
 {
 	AUTH_DAT adat = {0};
 	Key_schedule schedule;
 	struct sockaddr_in local, foreign;
 	char instance[INST_SZ];
 	socklen_t slen;
 	u_int cksum;
 	int r, s;

 	s = packet_get_connection_in();

 	slen = sizeof(local);
 	memset(&local, 0, sizeof(local));
 	if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
 		debug("getsockname failed: %.100s", strerror(errno));
 	slen = sizeof(foreign);
 	memset(&foreign, 0, sizeof(foreign));
 	if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
 		debug("getpeername failed: %.100s", strerror(errno));
 		fatal_cleanup();
 	}
 	instance[0] = '*';
 	instance[1] = 0;

 	/* Get the encrypted request, challenge, and session key. */
 	if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance,
 	    0, &adat, ""))) {
 		debug("Kerberos v4 krb_rd_req: %.100s", krb_err_txt[r]);
 		return (0);
 	}
 	des_key_sched((des_cblock *) adat.session, schedule);

 	*client = xmalloc(MAX_K_NAME_SZ);
 	(void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
 	    *adat.pinst ? "." : "", adat.pinst, adat.prealm);

 	/* Check ~/.klogin authorization now. */
 	if (kuserok(&adat, authctxt->user) != KSUCCESS) {
 		log("Kerberos v4 .klogin authorization failed for %s to "
 		    "account %s", *client, authctxt->user);
 		xfree(*client);
 		*client = NULL;
 		return (0);
 	}
 	/* Increment the checksum, and return it encrypted with the
 	   session key. */
 	cksum = adat.checksum + 1;
 	cksum = htonl(cksum);

 	/* If we can't successfully encrypt the checksum, we send back an
 	   empty message, admitting our failure. */
 	if ((r = krb_mk_priv((u_char *) & cksum, reply->dat, sizeof(cksum) + 1,
 	    schedule, &adat.session, &local, &foreign)) < 0) {
 		debug("Kerberos v4 mk_priv: (%d) %s", r, krb_err_txt[r]);
 		reply->dat[0] = 0;
 		reply->length = 0;
 	} else
 		reply->length = r;

 	/* Clear session key. */
 	memset(&adat.session, 0, sizeof(&adat.session));
 	return (1);
 }
 #endif /* KRB4 */

 #ifdef AFS
 int
 auth_krb4_tgt(Authctxt *authctxt, const char *string)
 {
 	CREDENTIALS creds;
 	struct passwd *pw;

 	if ((pw = authctxt->pw) == NULL)
 		goto failure;

 	temporarily_use_uid(pw);

 	if (!radix_to_creds(string, &creds)) {
 		log("Protocol error decoding Kerberos v4 TGT");
 		goto failure;
 	}
 	if (strncmp(creds.service, "", 1) == 0)	/* backward compatibility */
 		strlcpy(creds.service, "krbtgt", sizeof creds.service);

 	if (strcmp(creds.service, "krbtgt")) {
 		log("Kerberos v4 TGT (%s%s%s@%s) rejected for %s",
 		    creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
 		    creds.realm, pw->pw_name);
 		goto failure;
 	}
 	if (!krb4_init(authctxt))
 		goto failure;

 	if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
 		goto failure;

 	if (save_credentials(creds.service, creds.instance, creds.realm,
 	    creds.session, creds.lifetime, creds.kvno, &creds.ticket_st,
 	    creds.issue_date) != KSUCCESS) {
 		debug("Kerberos v4 TGT refused: couldn't save credentials");
 		goto failure;
 	}
 	/* Successful authentication, passed all checks. */
 	chown(tkt_string(), pw->pw_uid, pw->pw_gid);

 	debug("Kerberos v4 TGT accepted (%s%s%s@%s)",
 	    creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
 	memset(&creds, 0, sizeof(creds));

 	restore_uid();

 	return (1);

  failure:
 	krb4_cleanup_proc(authctxt);
 	memset(&creds, 0, sizeof(creds));
 	restore_uid();

 	return (0);
 }

 int
 auth_afs_token(Authctxt *authctxt, const char *token_string)
 {
 	CREDENTIALS creds;
 	struct passwd *pw;
 	uid_t uid;

 	if ((pw = authctxt->pw) == NULL)
 		return (0);

 	if (!radix_to_creds(token_string, &creds)) {
 		log("Protocol error decoding AFS token");
 		return (0);
 	}
 	if (strncmp(creds.service, "", 1) == 0)	/* backward compatibility */
 		strlcpy(creds.service, "afs", sizeof creds.service);

 	if (strncmp(creds.pname, "AFS ID ", 7) == 0)
 		uid = atoi(creds.pname + 7);
 	else
 		uid = pw->pw_uid;

 	if (kafs_settoken(creds.realm, uid, &creds)) {
 		log("AFS token (%s@%s) rejected for %s",
 		    creds.pname, creds.realm, pw->pw_name);
 		memset(&creds, 0, sizeof(creds));
 		return (0);
 	}
 	debug("AFS token accepted (%s@%s)", creds.pname, creds.realm);
 	memset(&creds, 0, sizeof(creds));

 	return (1);
 }
 #endif /* AFS */
	/*
	* Copyright (c) 1999 Dug Song. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "includes.h"
	RCSID("$OpenBSD: auth-krb4.c,v 1.28 2002/09/26 11:38:43 markus Exp $");

	#include "ssh.h"
	#include "ssh1.h"
	#include "packet.h"
	#include "xmalloc.h"
	#include "log.h"
	#include "servconf.h"
	#include "uidswap.h"
	#include "auth.h"

	#ifdef AFS
	#include "radix.h"
	#endif

	#ifdef KRB4
	extern ServerOptions options;

	static int
	krb4_init(void *context)
	{
	static int cleanup_registered = 0;
	Authctxt authctxt = (Authctxt )context;
	const char *tkt_root = TKT_ROOT;
	struct stat st;
	int fd;

	if (!authctxt->krb4_ticket_file) {
	/* Set unique ticket string manually since we're still root. */
	authctxt->krb4_ticket_file = xmalloc(MAXPATHLEN);
	#ifdef AFS
	if (lstat("/ticket", &st) != -1)
	tkt_root = "/ticket/";
	#endif /* AFS */
	snprintf(authctxt->krb4_ticket_file, MAXPATHLEN, "%s%u_%ld",
	tkt_root, authctxt->pw->pw_uid, (long)getpid());
	krb_set_tkt_string(authctxt->krb4_ticket_file);
	}
	/* Register ticket cleanup in case of fatal error. */
	if (!cleanup_registered) {
	fatal_add_cleanup(krb4_cleanup_proc, authctxt);
	cleanup_registered = 1;
	}
	/* Try to create our ticket file. */
	if ((fd = mkstemp(authctxt->krb4_ticket_file)) != -1) {
	close(fd);
	return (1);
	}
	/* Ticket file exists - make sure user owns it (just passed ticket). */
	if (lstat(authctxt->krb4_ticket_file, &st) != -1) {
	if (st.st_mode == (S_IFREG \| S_IRUSR \| S_IWUSR) &&
	st.st_uid == authctxt->pw->pw_uid)
	return (1);
	}
	/* Failure - cancel cleanup function, leaving ticket for inspection. */
	log("WARNING: bad ticket file %s", authctxt->krb4_ticket_file);

	fatal_remove_cleanup(krb4_cleanup_proc, authctxt);
	cleanup_registered = 0;

	xfree(authctxt->krb4_ticket_file);
	authctxt->krb4_ticket_file = NULL;

	return (0);
	}

	/*
	* try krb4 authentication,
	* return 1 on success, 0 on failure, -1 if krb4 is not available
	*/
	int
	auth_krb4_password(Authctxt authctxt, const char password)
	{
	AUTH_DAT adata;
	KTEXT_ST tkt;
	struct hostent *hp;
	struct passwd *pw;
	char localhost[MAXHOSTNAMELEN], phost[INST_SZ], realm[REALM_SZ];
	u_int32_t faddr;
	int r;

	if ((pw = authctxt->pw) == NULL)
	return (0);

	/*
	* Try Kerberos password authentication only for non-root
	* users and only if Kerberos is installed.
	*/
	if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
	/* Set up our ticket file. */
	if (!krb4_init(authctxt)) {
	log("Couldn't initialize Kerberos ticket file for %s!",
	pw->pw_name);
	goto failure;
	}
	/* Try to get TGT using our password. */
	r = krb_get_pw_in_tkt((char *) pw->pw_name, "", realm,
	"krbtgt", realm, DEFAULT_TKT_LIFE, (char *)password);
	if (r != INTK_OK) {
	debug("Kerberos v4 password authentication for %s "
	"failed: %s", pw->pw_name, krb_err_txt[r]);
	goto failure;
	}
	/* Successful authentication. */
	chown(tkt_string(), pw->pw_uid, pw->pw_gid);

	/*
	* Now that we have a TGT, try to get a local
	* "rcmd" ticket to ensure that we are not talking
	* to a bogus Kerberos server.
	*/
	gethostname(localhost, sizeof(localhost));
	strlcpy(phost, (char *)krb_get_phost(localhost),
	sizeof(phost));
	r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);

	if (r == KSUCCESS) {
	if ((hp = gethostbyname(localhost)) == NULL) {
	log("Couldn't get local host address!");
	goto failure;
	}
	memmove((void )&faddr, (void )hp->h_addr,
	sizeof(faddr));

	/* Verify our "rcmd" ticket. */
	r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
	faddr, &adata, "");
	if (r == RD_AP_UNDEC) {
	/*
	* Probably didn't have a srvtab on
	* localhost. Disallow login.
	*/
	log("Kerberos v4 TGT for %s unverifiable, "
	"no srvtab installed? krb_rd_req: %s",
	pw->pw_name, krb_err_txt[r]);
	goto failure;
	} else if (r != KSUCCESS) {
	log("Kerberos v4 %s ticket unverifiable: %s",
	KRB4_SERVICE_NAME, krb_err_txt[r]);
	goto failure;
	}
	} else if (r == KDC_PR_UNKNOWN) {
	/*
	* Disallow login if no rcmd service exists, and
	* log the error.
	*/
	log("Kerberos v4 TGT for %s unverifiable: %s; %s.%s "
	"not registered, or srvtab is wrong?", pw->pw_name,
	krb_err_txt[r], KRB4_SERVICE_NAME, phost);
	goto failure;
	} else {
	/*
	* TGT is bad, forget it. Possibly spoofed!
	*/
	debug("WARNING: Kerberos v4 TGT possibly spoofed "
	"for %s: %s", pw->pw_name, krb_err_txt[r]);
	goto failure;
	}
	/* Authentication succeeded. */
	return (1);
	} else
	/* Logging in as root or no local Kerberos realm. */
	debug("Unable to authenticate to Kerberos.");

	failure:
	krb4_cleanup_proc(authctxt);

	if (!options.kerberos_or_local_passwd)
	return (0);

	/* Fall back to ordinary passwd authentication. */
	return (-1);
	}

	void
	krb4_cleanup_proc(void *context)
	{
	Authctxt authctxt = (Authctxt )context;
	debug("krb4_cleanup_proc called");
	if (authctxt->krb4_ticket_file) {
	(void) dest_tkt();
	xfree(authctxt->krb4_ticket_file);
	authctxt->krb4_ticket_file = NULL;
	}
	}

	int
	auth_krb4(Authctxt authctxt, KTEXT auth, char *client, KTEXT reply)
	{
	AUTH_DAT adat = {0};
	Key_schedule schedule;
	struct sockaddr_in local, foreign;
	char instance[INST_SZ];
	socklen_t slen;
	u_int cksum;
	int r, s;

	s = packet_get_connection_in();

	slen = sizeof(local);
	memset(&local, 0, sizeof(local));
	if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
	debug("getsockname failed: %.100s", strerror(errno));
	slen = sizeof(foreign);
	memset(&foreign, 0, sizeof(foreign));
	if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
	debug("getpeername failed: %.100s", strerror(errno));
	fatal_cleanup();
	}
	instance[0] = '*';
	instance[1] = 0;

	/* Get the encrypted request, challenge, and session key. */
	if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance,
	0, &adat, ""))) {
	debug("Kerberos v4 krb_rd_req: %.100s", krb_err_txt[r]);
	return (0);
	}
	des_key_sched((des_cblock *) adat.session, schedule);

	*client = xmalloc(MAX_K_NAME_SZ);
	(void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
	*adat.pinst ? "." : "", adat.pinst, adat.prealm);

	/* Check ~/.klogin authorization now. */
	if (kuserok(&adat, authctxt->user) != KSUCCESS) {
	log("Kerberos v4 .klogin authorization failed for %s to "
	"account %s", *client, authctxt->user);
	xfree(*client);
	*client = NULL;
	return (0);
	}
	/* Increment the checksum, and return it encrypted with the
	session key. */
	cksum = adat.checksum + 1;
	cksum = htonl(cksum);

	/* If we can't successfully encrypt the checksum, we send back an
	empty message, admitting our failure. */
	if ((r = krb_mk_priv((u_char *) & cksum, reply->dat, sizeof(cksum) + 1,
	schedule, &adat.session, &local, &foreign)) < 0) {
	debug("Kerberos v4 mk_priv: (%d) %s", r, krb_err_txt[r]);
	reply->dat[0] = 0;
	reply->length = 0;
	} else
	reply->length = r;

	/* Clear session key. */
	memset(&adat.session, 0, sizeof(&adat.session));
	return (1);
	}
	#endif /* KRB4 */

	#ifdef AFS
	int
	auth_krb4_tgt(Authctxt authctxt, const char string)
	{
	CREDENTIALS creds;
	struct passwd *pw;

	if ((pw = authctxt->pw) == NULL)
	goto failure;

	temporarily_use_uid(pw);

	if (!radix_to_creds(string, &creds)) {
	log("Protocol error decoding Kerberos v4 TGT");
	goto failure;
	}
	if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
	strlcpy(creds.service, "krbtgt", sizeof creds.service);

	if (strcmp(creds.service, "krbtgt")) {
	log("Kerberos v4 TGT (%s%s%s@%s) rejected for %s",
	creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
	creds.realm, pw->pw_name);
	goto failure;
	}
	if (!krb4_init(authctxt))
	goto failure;

	if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
	goto failure;

	if (save_credentials(creds.service, creds.instance, creds.realm,
	creds.session, creds.lifetime, creds.kvno, &creds.ticket_st,
	creds.issue_date) != KSUCCESS) {
	debug("Kerberos v4 TGT refused: couldn't save credentials");
	goto failure;
	}
	/* Successful authentication, passed all checks. */
	chown(tkt_string(), pw->pw_uid, pw->pw_gid);

	debug("Kerberos v4 TGT accepted (%s%s%s@%s)",
	creds.pname, creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
	memset(&creds, 0, sizeof(creds));

	restore_uid();

	return (1);

	failure:
	krb4_cleanup_proc(authctxt);
	memset(&creds, 0, sizeof(creds));
	restore_uid();

	return (0);
	}

	int
	auth_afs_token(Authctxt authctxt, const char token_string)
	{
	CREDENTIALS creds;
	struct passwd *pw;
	uid_t uid;

	if ((pw = authctxt->pw) == NULL)
	return (0);

	if (!radix_to_creds(token_string, &creds)) {
	log("Protocol error decoding AFS token");
	return (0);
	}
	if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
	strlcpy(creds.service, "afs", sizeof creds.service);

	if (strncmp(creds.pname, "AFS ID ", 7) == 0)
	uid = atoi(creds.pname + 7);
	else
	uid = pw->pw_uid;

	if (kafs_settoken(creds.realm, uid, &creds)) {
	log("AFS token (%s@%s) rejected for %s",
	creds.pname, creds.realm, pw->pw_name);
	memset(&creds, 0, sizeof(creds));
	return (0);
	}
	debug("AFS token accepted (%s@%s)", creds.pname, creds.realm);
	memset(&creds, 0, sizeof(creds));

	return (1);
	}
	#endif /* AFS */