# The patch below adds support for the deprecated 'gssapi' authentication
# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included
# in this release. The use of 'gssapi' is deprecated due to the presence of
# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not
# susceptible to.
#
# To use the patch apply it to a OpenSSH 3.8p1 source tree. After compiling,
# backwards compatibility may be obtained by supplying the
# 'GssapiEnableMitmAttack yes' option to either the client or server.
#
# It should be noted that this patch is being made available purely as a means
# of easing the process of moving to OpenSSH 3.8p1. Any new installations are
# recommended to use the 'gssapi-with-mic' mechanism. Existing installations
# are encouraged to upgrade as soon as possible.

Index: b/auth2-gss.c
===================================================================
--- a/auth2-gss.c
+++ b/auth2-gss.c
@@ -296,4 +296,10 @@ Authmethod method_gssapi = {
 	&options.gss_authentication
 };
 
+Authmethod method_gssapi_old = {
+	"gssapi",
+	userauth_gssapi,
+	&options.gss_enable_mitm
+};
+
 #endif /* GSSAPI */
Index: b/auth2.c
===================================================================
--- a/auth2.c
+++ b/auth2.c
@@ -71,6 +71,7 @@ extern Authmethod method_kbdint;
 extern Authmethod method_hostbased;
 #ifdef GSSAPI
 extern Authmethod method_gssapi;
+extern Authmethod method_gssapi_old;
 #endif
 
 Authmethod *authmethods[] = {
@@ -78,6 +79,7 @@ Authmethod *authmethods[] = {
 	&method_pubkey,
 #ifdef GSSAPI
 	&method_gssapi,
+	&method_gssapi_old,
 #endif
 	&method_passwd,
 	&method_kbdint,
Index: b/readconf.c
===================================================================
--- a/readconf.c
+++ b/readconf.c
@@ -146,7 +146,7 @@ typedef enum {
 	oHostKeyAlgorithms, oBindAddress, oPKCS11Provider,
 	oClearAllForwardings, oNoHostAuthenticationForLocalhost,
 	oEnableSSHKeysign, oRekeyLimit, oVerifyHostKeyDNS, oConnectTimeout,
-	oAddressFamily, oGssAuthentication, oGssDelegateCreds,
+	oAddressFamily, oGssAuthentication, oGssDelegateCreds, oGssEnableMITM,
 	oServerAliveInterval, oServerAliveCountMax, oIdentitiesOnly,
 	oSendEnv, oControlPath, oControlMaster, oControlPersist,
 	oHashKnownHosts,
@@ -193,9 +193,11 @@ static struct {
 #if defined(GSSAPI)
 	{ "gssapiauthentication", oGssAuthentication },
 	{ "gssapidelegatecredentials", oGssDelegateCreds },
+	{ "gssapienablemitmattack", oGssEnableMITM },
 #else
 	{ "gssapiauthentication", oUnsupported },
 	{ "gssapidelegatecredentials", oUnsupported },
+	{ "gssapienablemitmattack", oUnsupported },
 #endif
 	{ "fallbacktorsh", oDeprecated },
 	{ "usersh", oDeprecated },
@@ -897,6 +899,10 @@ parse_time:
 	case oGssDelegateCreds:
 		intptr = &options->gss_deleg_creds;
 		goto parse_flag;
+		
+	case oGssEnableMITM:
+		intptr = &options->gss_enable_mitm;
+		goto parse_flag;
 
 	case oBatchMode:
 		intptr = &options->batch_mode;
@@ -1602,6 +1608,7 @@ initialize_options(Options * options)
 	options->challenge_response_authentication = -1;
 	options->gss_authentication = -1;
 	options->gss_deleg_creds = -1;
+	options->gss_enable_mitm = -1;
 	options->password_authentication = -1;
 	options->kbd_interactive_authentication = -1;
 	options->kbd_interactive_devices = NULL;
@@ -1731,6 +1738,8 @@ fill_default_options(Options * options)
 		options->gss_authentication = 0;
 	if (options->gss_deleg_creds == -1)
 		options->gss_deleg_creds = 0;
+	if (options->gss_enable_mitm == -1)
+		options->gss_enable_mitm = 0;
 	if (options->password_authentication == -1)
 		options->password_authentication = 1;
 	if (options->kbd_interactive_authentication == -1)
Index: b/readconf.h
===================================================================
--- a/readconf.h
+++ b/readconf.h
@@ -46,6 +46,7 @@ typedef struct {
 					/* Try S/Key or TIS, authentication. */
 	int     gss_authentication;	/* Try GSS authentication */
 	int     gss_deleg_creds;	/* Delegate GSS credentials */
+	int 	gss_enable_mitm;	/* Enable old style gssapi auth */
 	int     password_authentication;	/* Try password
 						 * authentication. */
 	int     kbd_interactive_authentication; /* Try keyboard-interactive auth. */
Index: b/servconf.c
===================================================================
--- a/servconf.c
+++ b/servconf.c
@@ -119,6 +119,7 @@ initialize_server_options(ServerOptions
 	options->gss_authentication=-1;
 	options->gss_cleanup_creds = -1;
 	options->gss_strict_acceptor = -1;
+	options->gss_enable_mitm = -1;
 	options->password_authentication = -1;
 	options->kbd_interactive_authentication = -1;
 	options->challenge_response_authentication = -1;
@@ -279,6 +280,8 @@ fill_default_server_options(ServerOption
 		options->gss_cleanup_creds = 1;
 	if (options->gss_strict_acceptor == -1)
 		options->gss_strict_acceptor = 0;
+	if (options->gss_enable_mitm == -1)
+		options->gss_enable_mitm = 0;
 	if (options->password_authentication == -1)
 		options->password_authentication = 1;
 	if (options->kbd_interactive_authentication == -1)
@@ -411,7 +414,7 @@ typedef enum {
 	sHostbasedUsesNameFromPacketOnly, sHostbasedAcceptedKeyTypes,
 	sHostKeyAlgorithms,
 	sClientAliveInterval, sClientAliveCountMax, sAuthorizedKeysFile,
-	sGssAuthentication, sGssCleanupCreds, sGssStrictAcceptor,
+	sGssAuthentication, sGssCleanupCreds, sGssStrictAcceptor, sGssEnableMITM,
 	sAcceptEnv, sPermitTunnel,
 	sMatch, sPermitOpen, sForceCommand, sChrootDirectory,
 	sUsePrivilegeSeparation, sAllowAgentForwarding,
@@ -486,10 +489,12 @@ static struct {
 	{ "gssapiauthentication", sGssAuthentication, SSHCFG_ALL },
 	{ "gssapicleanupcredentials", sGssCleanupCreds, SSHCFG_GLOBAL },
 	{ "gssapistrictacceptorcheck", sGssStrictAcceptor, SSHCFG_GLOBAL },
+	{ "gssapienablemitmattack", sGssEnableMITM },
 #else
 	{ "gssapiauthentication", sUnsupported, SSHCFG_ALL },
 	{ "gssapicleanupcredentials", sUnsupported, SSHCFG_GLOBAL },
 	{ "gssapistrictacceptorcheck", sUnsupported, SSHCFG_GLOBAL },
+	{ "gssapienablemitmattack", sUnsupported },
 #endif
 	{ "passwordauthentication", sPasswordAuthentication, SSHCFG_ALL },
 	{ "kbdinteractiveauthentication", sKbdInteractiveAuthentication, SSHCFG_ALL },
@@ -1239,6 +1244,10 @@ process_server_config_line(ServerOptions
 		intptr = &options->gss_strict_acceptor;
 		goto parse_flag;
 
+	case sGssEnableMITM:
+		intptr = &options->gss_enable_mitm;
+		goto parse_flag;
+
 	case sPasswordAuthentication:
 		intptr = &options->password_authentication;
 		goto parse_flag;
Index: b/servconf.h
===================================================================
--- a/servconf.h
+++ b/servconf.h
@@ -119,6 +119,7 @@ typedef struct {
 						 * authenticated with Kerberos. */
 	int     gss_authentication;	/* If true, permit GSSAPI authentication */
 	int     gss_cleanup_creds;	/* If true, destroy cred cache on logout */
+        int     gss_enable_mitm;	/* If true, enable old style GSSAPI */
 	int     gss_strict_acceptor;	/* If true, restrict the GSSAPI acceptor name */
 	int     password_authentication;	/* If true, permit password
 						 * authentication. */
Index: b/ssh_config
===================================================================
--- a/ssh_config
+++ b/ssh_config
@@ -56,4 +56,11 @@ ForwardX11Trusted yes
 #   PermitLocalCommand no
 #   VisualHostKey no
 #   ProxyCommand ssh -q -W %h:%p gateway.example.com
+
+# Set this to 'yes' to enable support for the deprecated 'gssapi' authentication
+# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included
+# in this release. The use of 'gssapi' is deprecated due to the presence of 
+# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to.
+#   GSSAPIEnableMITMAttack no
+
 #   RekeyLimit 1G 1h
Index: b/sshconnect2.c
===================================================================
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -326,6 +326,11 @@ Authmethod authmethods[] = {
 		NULL,
 		&options.gss_authentication,
 		NULL},
+	{"gssapi",
+		userauth_gssapi,
+		NULL,
+		&options.gss_enable_mitm,
+		NULL},
 #endif
 	{"hostbased",
 		userauth_hostbased,
@@ -703,7 +708,9 @@ process_gssapi_token(void *ctxt, gss_buf
 
 	if (status == GSS_S_COMPLETE) {
 		/* send either complete or MIC, depending on mechanism */
-		if (!(flags & GSS_C_INTEG_FLAG)) {
+		
+		if (strcmp(authctxt->method->name,"gssapi") == 0 ||
+		    (!(flags & GSS_C_INTEG_FLAG))) {
 			packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
 			packet_send();
 		} else {
Index: b/sshd_config
===================================================================
--- a/sshd_config
+++ b/sshd_config
@@ -85,6 +85,13 @@ PasswordAuthentication no
 #GSSAPIAuthentication no
 #GSSAPICleanupCredentials yes
 
+# Set this to 'yes' to enable support for the deprecated 'gssapi' authentication
+# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included
+# in this release. The use of 'gssapi' is deprecated due to the presence of 
+# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to.
+#GSSAPIEnableMITMAttack no
+ 
+
 # Set this to 'yes' to enable PAM authentication, account processing,
 # and session processing. If this is enabled, PAM authentication will
 # be allowed through the ChallengeResponseAuthentication and