auth-krb4.c

/*
 *    Dug Song <dugsong@UMICH.EDU>
 *    Kerberos v4 authentication and ticket-passing routines.
 */

#include "includes.h"
#include "packet.h"
#include "xmalloc.h"
#include "ssh.h"

#ifdef KRB4
char *ticket = NULL;

void
krb4_cleanup_proc(void *ignore)
{
	debug("krb4_cleanup_proc called");
	if (ticket) {
		(void) dest_tkt();
		xfree(ticket);
		ticket = NULL;
	}
}

int 
krb4_init(uid_t uid)
{
	static int cleanup_registered = 0;
	char *tkt_root = TKT_ROOT;
	struct stat st;
	int fd;

	if (!ticket) {
		/* Set unique ticket string manually since we're still root. */
		ticket = xmalloc(MAXPATHLEN);
#ifdef AFS
		if (lstat("/ticket", &st) != -1)
			tkt_root = "/ticket/";
#endif /* AFS */
		snprintf(ticket, MAXPATHLEN, "%s%d_%d", tkt_root, uid, getpid());
		(void) krb_set_tkt_string(ticket);
	}
	/* Register ticket cleanup in case of fatal error. */
	if (!cleanup_registered) {
		fatal_add_cleanup(krb4_cleanup_proc, NULL);
		cleanup_registered = 1;
	}
	/* Try to create our ticket file. */
	if ((fd = mkstemp(ticket)) != -1) {
		close(fd);
		return 1;
	}
	/* Ticket file exists - make sure user owns it (just passed ticket). */
	if (lstat(ticket, &st) != -1) {
		if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
		    st.st_uid == uid)
			return 1;
	}
	/* Failure - cancel cleanup function, leaving bad ticket for inspection. */
	log("WARNING: bad ticket file %s", ticket);
	fatal_remove_cleanup(krb4_cleanup_proc, NULL);
	cleanup_registered = 0;
	xfree(ticket);
	ticket = NULL;

	return 0;
}

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

	s = packet_get_connection_in();

	r = sizeof(local);
	memset(&local, 0, sizeof(local));
	if (getsockname(s, (struct sockaddr *) & local, &r) < 0)
		debug("getsockname failed: %.100s", strerror(errno));
	r = sizeof(foreign);
	memset(&foreign, 0, sizeof(foreign));
	if (getpeername(s, (struct sockaddr *) & foreign, &r) < 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, ""))) {
		packet_send_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, (char *) server_user) != KSUCCESS) {
		packet_send_debug("Kerberos V4 .klogin authorization failed!");
		log("Kerberos V4 .klogin authorization failed for %s to account %s",
		    *client, server_user);
		xfree(*client);
		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) {
		packet_send_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));

	packet_start(SSH_SMSG_AUTH_KERBEROS_RESPONSE);
	packet_put_string((char *) reply.dat, reply.length);
	packet_send();
	packet_write_wait();
	return 1;
}
#endif /* KRB4 */

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

	if (!radix_to_creds(string, &creds)) {
		log("Protocol error decoding Kerberos V4 tgt");
		packet_send_debug("Protocol error decoding Kerberos V4 tgt");
		goto auth_kerberos_tgt_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);
		packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for %s",
		    creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
		    creds.realm, pw->pw_name);
		goto auth_kerberos_tgt_failure;
	}
	if (!krb4_init(pw->pw_uid))
		goto auth_kerberos_tgt_failure;

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

	if (save_credentials(creds.service, creds.instance, creds.realm,
	    creds.session, creds.lifetime, creds.kvno,
	    &creds.ticket_st, creds.issue_date) != KSUCCESS) {
		packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
		goto auth_kerberos_tgt_failure;
	}
	/* Successful authentication, passed all checks. */
	chown(tkt_string(), pw->pw_uid, pw->pw_gid);

	packet_send_debug("Kerberos V4 tgt accepted (%s.%s@%s, %s%s%s@%s)",
	    creds.service, creds.instance, creds.realm, creds.pname,
	    creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
	memset(&creds, 0, sizeof(creds));
	packet_start(SSH_SMSG_SUCCESS);
	packet_send();
	packet_write_wait();
	return 1;

auth_kerberos_tgt_failure:
	krb4_cleanup_proc(NULL);
	memset(&creds, 0, sizeof(creds));
	packet_start(SSH_SMSG_FAILURE);
	packet_send();
	packet_write_wait();
	return 0;
}

int 
auth_afs_token(struct passwd *pw, const char *token_string)
{
	CREDENTIALS creds;
	uid_t uid = pw->pw_uid;

	if (!radix_to_creds(token_string, &creds)) {
		log("Protocol error decoding AFS token");
		packet_send_debug("Protocol error decoding AFS token");
		packet_start(SSH_SMSG_FAILURE);
		packet_send();
		packet_write_wait();
		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);

	if (kafs_settoken(creds.realm, uid, &creds)) {
		log("AFS token (%s@%s) rejected for %s", creds.pname, creds.realm,
		    pw->pw_name);
		packet_send_debug("AFS token (%s@%s) rejected for %s", creds.pname,
		    creds.realm, pw->pw_name);
		memset(&creds, 0, sizeof(creds));
		packet_start(SSH_SMSG_FAILURE);
		packet_send();
		packet_write_wait();
		return 0;
	}
	packet_send_debug("AFS token accepted (%s@%s, %s@%s)", creds.service,
	    creds.realm, creds.pname, creds.realm);
	memset(&creds, 0, sizeof(creds));
	packet_start(SSH_SMSG_SUCCESS);
	packet_send();
	packet_write_wait();
	return 1;
}
#endif /* AFS */