diff -up openssh-7.4p1/gss-serv-krb5.c.GSSAPIEnablek5users openssh-7.4p1/gss-serv-krb5.c

--- openssh-7.4p1/gss-serv-krb5.c.GSSAPIEnablek5users	2016-12-23 15:18:40.615216100 +0100

+++ openssh-7.4p1/gss-serv-krb5.c	2016-12-23 15:18:40.628216102 +0100

@@ -279,7 +279,6 @@ ssh_gssapi_krb5_cmdok(krb5_principal pri

 	FILE *fp;

 	char file[MAXPATHLEN];

 	char *line = NULL;

-	char kuser[65]; /* match krb5_kuserok() */

 	struct stat st;

 	struct passwd *pw = the_authctxt->pw;

 	int found_principal = 0;

@@ -288,7 +287,7 @@ ssh_gssapi_krb5_cmdok(krb5_principal pri

 	snprintf(file, sizeof(file), "%s/.k5users", pw->pw_dir);

 	/* If both .k5login and .k5users DNE, self-login is ok. */

-	if (!k5login_exists && (access(file, F_OK) == -1)) {

+	if ( !options.enable_k5users || (!k5login_exists && (access(file, F_OK) == -1))) {

                 return ssh_krb5_kuserok(krb_context, principal, luser,

                                         k5login_exists);

 	}

diff -up openssh-7.4p1/servconf.c.GSSAPIEnablek5users openssh-7.4p1/servconf.c

--- openssh-7.4p1/servconf.c.GSSAPIEnablek5users	2016-12-23 15:18:40.615216100 +0100

+++ openssh-7.4p1/servconf.c	2016-12-23 15:35:36.354401156 +0100

@@ -168,6 +168,7 @@ initialize_server_options(ServerOptions

 	options->gss_store_rekey = -1;

 	options->gss_kex_algorithms = NULL;

 	options->use_kuserok = -1;

+	options->enable_k5users = -1;

 	options->password_authentication = -1;

 	options->kbd_interactive_authentication = -1;

 	options->challenge_response_authentication = -1;

@@ -345,6 +346,8 @@ fill_default_server_options(ServerOption

 #endif

 	if (options->use_kuserok == -1)

 		options->use_kuserok = 1;

+	if (options->enable_k5users == -1)

+		options->enable_k5users = 0;

 	if (options->password_authentication == -1)

 		options->password_authentication = 1;

 	if (options->kbd_interactive_authentication == -1)

@@ -418,7 +421,7 @@ typedef enum {

 	sHostbasedUsesNameFromPacketOnly, sHostbasedAcceptedAlgorithms,

 	sHostKeyAlgorithms, sPerSourceMaxStartups, sPerSourceNetBlockSize,

 	sClientAliveInterval, sClientAliveCountMax, sAuthorizedKeysFile,

-	sGssAuthentication, sGssCleanupCreds, sGssStrictAcceptor,

+	sGssAuthentication, sGssCleanupCreds, sGssEnablek5users, sGssStrictAcceptor,

 	sGssKeyEx, sGssKexAlgorithms, sGssStoreRekey,

 	sAcceptEnv, sSetEnv, sPermitTunnel,

 	sMatch, sPermitOpen, sPermitListen, sForceCommand, sChrootDirectory,

@@ -497,14 +500,16 @@ static struct {

 	{ "gssapikeyexchange", sGssKeyEx, SSHCFG_GLOBAL },

 	{ "gssapistorecredentialsonrekey", sGssStoreRekey, SSHCFG_GLOBAL },

 	{ "gssapikexalgorithms", sGssKexAlgorithms, SSHCFG_GLOBAL },

+	{ "gssapienablek5users", sGssEnablek5users, SSHCFG_ALL },

 #else

 	{ "gssapiauthentication", sUnsupported, SSHCFG_ALL },

 	{ "gssapicleanupcredentials", sUnsupported, SSHCFG_GLOBAL },

 	{ "gssapicleanupcreds", sUnsupported, SSHCFG_GLOBAL },

 	{ "gssapistrictacceptorcheck", sUnsupported, SSHCFG_GLOBAL },

 	{ "gssapikeyexchange", sUnsupported, SSHCFG_GLOBAL },

 	{ "gssapistorecredentialsonrekey", sUnsupported, SSHCFG_GLOBAL },

 	{ "gssapikexalgorithms", sUnsupported, SSHCFG_GLOBAL },

+	{ "gssapienablek5users", sUnsupported, SSHCFG_ALL },

 #endif

 	{ "gssusesessionccache", sUnsupported, SSHCFG_GLOBAL },

 	{ "gssapiusesessioncredcache", sUnsupported, SSHCFG_GLOBAL },

@@ -1653,6 +1658,10 @@ process_server_config_line(ServerOptions

 		intptr = &options->use_kuserok;

 		goto parse_flag;

+	case sGssEnablek5users:

+		intptr = &options->enable_k5users;

+		goto parse_flag;

+

 	case sPermitListen:

 	case sPermitOpen:

 		if (opcode == sPermitListen) {

@@ -2026,6 +2035,7 @@ copy_set_server_options(ServerOptions *d

 	M_CP_INTOPT(ip_qos_interactive);

 	M_CP_INTOPT(ip_qos_bulk);

 	M_CP_INTOPT(use_kuserok);

+	M_CP_INTOPT(enable_k5users);

 	M_CP_INTOPT(rekey_limit);

 	M_CP_INTOPT(rekey_interval);

 	M_CP_INTOPT(log_level);

@@ -2320,6 +2330,7 @@ dump_config(ServerOptions *o)

 # endif

 	dump_cfg_fmtint(sKerberosUniqueCCache, o->kerberos_unique_ccache);

 	dump_cfg_fmtint(sKerberosUseKuserok, o->use_kuserok);

+	dump_cfg_fmtint(sGssEnablek5users, o->enable_k5users);

 #endif

 #ifdef GSSAPI

 	dump_cfg_fmtint(sGssAuthentication, o->gss_authentication);

diff -up openssh-7.4p1/servconf.h.GSSAPIEnablek5users openssh-7.4p1/servconf.h

--- openssh-7.4p1/servconf.h.GSSAPIEnablek5users	2016-12-23 15:18:40.616216100 +0100

+++ openssh-7.4p1/servconf.h	2016-12-23 15:18:40.629216102 +0100

@@ -174,6 +174,7 @@ typedef struct {

	int     kerberos_unique_ccache;		/* If true, the acquired ticket will

						 * be stored in per-session ccache */

 	int	use_kuserok;

+	int		enable_k5users;

 	int     gss_authentication;	/* If true, permit GSSAPI authentication */

 	int     gss_keyex;		/* If true, permit GSSAPI key exchange */

 	int     gss_cleanup_creds;	/* If true, destroy cred cache on logout */

diff -up openssh-7.4p1/sshd_config.5.GSSAPIEnablek5users openssh-7.4p1/sshd_config.5

--- openssh-7.4p1/sshd_config.5.GSSAPIEnablek5users	2016-12-23 15:18:40.630216103 +0100

+++ openssh-7.4p1/sshd_config.5	2016-12-23 15:36:21.607408435 +0100

@@ -628,6 +628,12 @@ Specifies whether to automatically destr

 on logout.

 The default is

 .Cm yes .

+.It Cm GSSAPIEnablek5users

+Specifies whether to look at .k5users file for GSSAPI authentication

+access control. Further details are described in

+.Xr ksu 1 .

+The default is

+.Cm no .

 .It Cm GSSAPIKeyExchange

 Specifies whether key exchange based on GSSAPI is allowed. GSSAPI key exchange

 doesn't rely on ssh keys to verify host identity.

diff -up openssh-7.4p1/sshd_config.GSSAPIEnablek5users openssh-7.4p1/sshd_config

--- openssh-7.4p1/sshd_config.GSSAPIEnablek5users	2016-12-23 15:18:40.616216100 +0100

+++ openssh-7.4p1/sshd_config	2016-12-23 15:18:40.631216103 +0100

@@ -80,6 +80,7 @@ GSSAPIAuthentication yes

 #GSSAPICleanupCredentials yes

 #GSSAPIStrictAcceptorCheck yes

 #GSSAPIKeyExchange no

+#GSSAPIEnablek5users no

 # Set this to 'yes' to enable PAM authentication, account processing,

 # and session processing. If this is enabled, PAM authentication will