diff -up openssh-5.6p1/auth-krb5.c.kuserok openssh-5.6p1/auth-krb5.c
--- openssh-5.6p1/auth-krb5.c.kuserok	2010-11-15 10:08:05.000000000 +0100
+++ openssh-5.6p1/auth-krb5.c	2010-11-15 10:11:02.000000000 +0100
@@ -54,6 +54,20 @@
 
 extern ServerOptions	 options;
 
+int
+ssh_krb5_kuserok(krb5_context krb5_ctx, krb5_principal krb5_user, const char *client)
+{
+	if (options.use_kuserok)
+		return krb5_kuserok(krb5_ctx, krb5_user, client);
+	else {
+		char kuser[65];
+
+		if (krb5_aname_to_localname(krb5_ctx, krb5_user, sizeof(kuser), kuser))
+			return 0;
+		return strcmp(kuser, client) == 0;
+	}
+}
+
 static int
 krb5_init(void *context)
 {
@@ -146,7 +160,7 @@ auth_krb5_password(Authctxt *authctxt, c
 	if (problem)
 		goto out;
 
-	if (!krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user, client)) {
+	if (!ssh_krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user, client)) {
 		problem = -1;
 		goto out;
 	}
diff -up openssh-5.6p1/gss-serv-krb5.c.kuserok openssh-5.6p1/gss-serv-krb5.c
--- openssh-5.6p1/gss-serv-krb5.c.kuserok	2010-11-15 10:08:05.000000000 +0100
+++ openssh-5.6p1/gss-serv-krb5.c	2010-11-15 10:12:35.000000000 +0100
@@ -57,6 +57,7 @@ extern ServerOptions options;
 #endif
 
 static krb5_context krb_context = NULL;
+extern int ssh_krb5_kuserok(krb5_context, krb5_principal, const char *);
 
 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
 
@@ -97,7 +98,7 @@ ssh_gssapi_krb5_userok(ssh_gssapi_client
 		    krb5_get_err_text(krb_context, retval));
 		return 0;
 	}
-	if (krb5_kuserok(krb_context, princ, name)) {
+	if (ssh_krb5_kuserok(krb_context, princ, name)) {
 		retval = 1;
 		logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
 		    name, (char *)client->displayname.value);
diff -up openssh-5.6p1/servconf.c.kuserok openssh-5.6p1/servconf.c
--- openssh-5.6p1/servconf.c.kuserok	2010-11-15 10:08:05.000000000 +0100
+++ openssh-5.6p1/servconf.c	2010-11-15 10:08:05.000000000 +0100
@@ -138,6 +138,7 @@ initialize_server_options(ServerOptions 
 	options->revoked_keys_file = NULL;
 	options->trusted_user_ca_keys = NULL;
 	options->authorized_principals_file = NULL;
+	options->use_kuserok = -1;
 }
 
 void
@@ -286,6 +287,8 @@ fill_default_server_options(ServerOption
 	if (use_privsep == -1)
 		use_privsep = 1;
 
+	if (options->use_kuserok == -1)
+		options->use_kuserok = 1;
 #ifndef HAVE_MMAP
 	if (use_privsep && options->compression == 1) {
 		error("This platform does not support both privilege "
@@ -307,7 +310,7 @@ typedef enum {
 	sPermitRootLogin, sLogFacility, sLogLevel,
 	sRhostsRSAAuthentication, sRSAAuthentication,
 	sKerberosAuthentication, sKerberosOrLocalPasswd, sKerberosTicketCleanup,
-	sKerberosGetAFSToken,
+	sKerberosGetAFSToken, sKerberosUseKuserok,
 	sKerberosTgtPassing, sChallengeResponseAuthentication,
 	sPasswordAuthentication, sKbdInteractiveAuthentication,
 	sListenAddress, sAddressFamily,
@@ -377,11 +380,13 @@ static struct {
 #else
 	{ "kerberosgetafstoken", sUnsupported, SSHCFG_GLOBAL },
 #endif
+	{ "kerberosusekuserok", sKerberosUseKuserok, SSHCFG_ALL },
 #else
 	{ "kerberosauthentication", sUnsupported, SSHCFG_ALL },
 	{ "kerberosorlocalpasswd", sUnsupported, SSHCFG_GLOBAL },
 	{ "kerberosticketcleanup", sUnsupported, SSHCFG_GLOBAL },
 	{ "kerberosgetafstoken", sUnsupported, SSHCFG_GLOBAL },
+	{ "kerberosusekuserok", sUnsupported, SSHCFG_ALL },
 #endif
 	{ "kerberostgtpassing", sUnsupported, SSHCFG_GLOBAL },
 	{ "afstokenpassing", sUnsupported, SSHCFG_GLOBAL },
@@ -1341,6 +1346,10 @@ process_server_config_line(ServerOptions
 		*activep = value;
 		break;
 
+	case sKerberosUseKuserok:
+		intptr = &options->use_kuserok;
+		goto parse_flag;
+
 	case sPermitOpen:
 		arg = strdelim(&cp);
 		if (!arg || *arg == '\0')
@@ -1525,6 +1534,7 @@ copy_set_server_options(ServerOptions *d
 	M_CP_INTOPT(x11_use_localhost);
 	M_CP_INTOPT(max_sessions);
 	M_CP_INTOPT(max_authtries);
+	M_CP_INTOPT(use_kuserok);
 
 	M_CP_STROPT(banner);
 	if (preauth)
@@ -1745,6 +1755,7 @@ dump_config(ServerOptions *o)
 	dump_cfg_fmtint(sUseDNS, o->use_dns);
 	dump_cfg_fmtint(sAllowTcpForwarding, o->allow_tcp_forwarding);
 	dump_cfg_fmtint(sUsePrivilegeSeparation, use_privsep);
+	dump_cfg_fmtint(sKerberosUseKuserok, o->use_kuserok);
 
 	/* string arguments */
 	dump_cfg_string(sPidFile, o->pid_file);
diff -up openssh-5.6p1/servconf.h.kuserok openssh-5.6p1/servconf.h
--- openssh-5.6p1/servconf.h.kuserok	2010-11-15 10:08:05.000000000 +0100
+++ openssh-5.6p1/servconf.h	2010-11-15 10:08:05.000000000 +0100
@@ -157,6 +157,7 @@ typedef struct {
 
 	int	num_permitted_opens;
 
+	int	use_kuserok;
 	char   *chroot_directory;
 	char   *revoked_keys_file;
 	char   *trusted_user_ca_keys;
diff -up openssh-5.6p1/sshd_config.5.kuserok openssh-5.6p1/sshd_config.5
--- openssh-5.6p1/sshd_config.5.kuserok	2010-11-15 10:08:05.000000000 +0100
+++ openssh-5.6p1/sshd_config.5	2010-11-15 10:08:05.000000000 +0100
@@ -564,6 +564,10 @@ Specifies whether to automatically destr
 file on logout.
 The default is
 .Dq yes .
+.It Cm KerberosUseKuserok
+Specifies whether to look at .k5login file for user's aliases.
+The default is
+.Dq yes .
 .It Cm KeyRegenerationInterval
 In protocol version 1, the ephemeral server key is automatically regenerated
 after this many seconds (if it has been used).
@@ -694,6 +698,7 @@ Available keywords are
 .Cm HostbasedUsesNameFromPacketOnly ,
 .Cm KbdInteractiveAuthentication ,
 .Cm KerberosAuthentication ,
+.Cm KerberosUseKuserok ,
 .Cm MaxAuthTries ,
 .Cm MaxSessions ,
 .Cm PubkeyAuthentication ,
diff -up openssh-5.6p1/sshd_config.kuserok openssh-5.6p1/sshd_config
--- openssh-5.6p1/sshd_config.kuserok	2010-11-15 10:08:05.000000000 +0100
+++ openssh-5.6p1/sshd_config	2010-11-15 10:08:05.000000000 +0100
@@ -72,6 +72,7 @@ ChallengeResponseAuthentication no
 #KerberosOrLocalPasswd yes
 #KerberosTicketCleanup yes
 #KerberosGetAFSToken no
+#KerberosUseKuserok yes
 
 # GSSAPI options
 #GSSAPIAuthentication no