Add support for Kerberos credential delegation

Support GSSAPI/Kerberos credentials being delegated to the server by a
client.  With this, a user authenticating to PostgreSQL using Kerberos
(GSSAPI) credentials can choose to delegate their credentials to the
PostgreSQL server (which can choose to accept them, or not), allowing
the server to then use those delegated credentials to connect to
another service, such as with postgres_fdw or dblink or theoretically
any other service which is able to be authenticated using Kerberos.

Both postgres_fdw and dblink are changed to allow non-superuser
password-less connections but only when GSSAPI credentials have been
delegated to the server by the client and GSSAPI is used to
authenticate to the remote system.

Authors: Stephen Frost, Peifeng Qiu
Reviewed-By: David Christensen
Discussion: https://postgr.es/m/CO1PR05MB8023CC2CB575E0FAAD7DF4F8A8E29@CO1PR05MB8023.namprd05.prod.outlook.com

25 files changed, 523 insertions, 58 deletions

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 41aafe0b87..c123f10989 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -979,7 +979,8 @@ CREATE VIEW pg_stat_gssapi AS
             S.pid,
             S.gss_auth AS gss_authenticated,
             S.gss_princ AS principal,
-            S.gss_enc AS encrypted
+            S.gss_enc AS encrypted,
+            S.gss_deleg AS credentials_delegated
     FROM pg_stat_get_activity(NULL) AS S
     WHERE S.client_port IS NOT NULL;
 
diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index dca02271dc..6e1977fa62 100644
--- a/src/backend/foreign/foreign.c
+++ b/src/backend/foreign/foreign.c
@@ -574,6 +574,7 @@ static const struct ConnectionOption libpq_conninfo_options[] = {
 	{"requiressl", ForeignServerRelationId},
 	{"sslmode", ForeignServerRelationId},
 	{"gsslib", ForeignServerRelationId},
+	{"gssdeleg", ForeignServerRelationId},
 	{NULL, InvalidOid}
 };
 
diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index bc0cf26b12..00ec9da284 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -165,6 +165,7 @@ static int	CheckCertAuth(Port *port);
  */
 char	   *pg_krb_server_keyfile;
 bool		pg_krb_caseins_users;
+bool		pg_gss_accept_deleg;
 
 
 /*----------------------------------------------------------------
@@ -918,6 +919,7 @@ pg_GSS_recvauth(Port *port)
 	int			mtype;
 	StringInfoData buf;
 	gss_buffer_desc gbuf;
+	gss_cred_id_t delegated_creds;
 
 	/*
 	 * Use the configured keytab, if there is one.  Unfortunately, Heimdal
@@ -947,6 +949,9 @@ pg_GSS_recvauth(Port *port)
 	 */
 	port->gss->ctx = GSS_C_NO_CONTEXT;
 
+	delegated_creds = GSS_C_NO_CREDENTIAL;
+	port->gss->delegated_creds = false;
+
 	/*
 	 * Loop through GSSAPI message exchange. This exchange can consist of
 	 * multiple messages sent in both directions. First message is always from
@@ -997,7 +1002,7 @@ pg_GSS_recvauth(Port *port)
 										  &port->gss->outbuf,
 										  &gflags,
 										  NULL,
-										  NULL);
+										  pg_gss_accept_deleg ? &delegated_creds : NULL);
 
 		/* gbuf no longer used */
 		pfree(buf.data);
@@ -1009,6 +1014,12 @@ pg_GSS_recvauth(Port *port)
 
 		CHECK_FOR_INTERRUPTS();
 
+		if (delegated_creds != GSS_C_NO_CREDENTIAL && gflags & GSS_C_DELEG_FLAG)
+		{
+			pg_store_delegated_credential(delegated_creds);
+			port->gss->delegated_creds = true;
+		}
+
 		if (port->gss->outbuf.length != 0)
 		{
 			/*
diff --git a/src/backend/libpq/be-gssapi-common.c b/src/backend/libpq/be-gssapi-common.c
index fb39c760d8..64d41e5291 100644
--- a/src/backend/libpq/be-gssapi-common.c
+++ b/src/backend/libpq/be-gssapi-common.c
@@ -92,3 +92,56 @@ pg_GSS_error(const char *errmsg,
 			(errmsg_internal("%s", errmsg),
 			 errdetail_internal("%s: %s", msg_major, msg_minor)));
 }
+
+/*
+ * Store the credentials passed in into the memory cache for later usage.
+ *
+ * This allows credentials to be delegated to us for us to use to connect
+ * to other systems with, using, e.g. postgres_fdw or dblink.
+ */
+#define GSS_MEMORY_CACHE "MEMORY:"
+void
+pg_store_delegated_credential(gss_cred_id_t cred)
+{
+	OM_uint32	major,
+				minor;
+	gss_OID_set mech;
+	gss_cred_usage_t usage;
+	gss_key_value_element_desc cc;
+	gss_key_value_set_desc ccset;
+
+	cc.key = "ccache";
+	cc.value = GSS_MEMORY_CACHE;
+	ccset.count = 1;
+	ccset.elements = &cc;
+
+	/* Make the delegated credential only available to current process */
+	major = gss_store_cred_into(&minor,
+								cred,
+								GSS_C_INITIATE, /* credential only used for
+												 * starting libpq connection */
+								GSS_C_NULL_OID, /* store all */
+								true,	/* overwrite */
+								true,	/* make default */
+								&ccset,
+								&mech,
+								&usage);
+
+	if (major != GSS_S_COMPLETE)
+	{
+		pg_GSS_error("gss_store_cred", major, minor);
+	}
+
+	/* Credential stored, so we can release our credential handle. */
+	major = gss_release_cred(&minor, &cred);
+	if (major != GSS_S_COMPLETE)
+	{
+		pg_GSS_error("gss_release_cred", major, minor);
+	}
+
+	/*
+	 * Set KRB5CCNAME for this backend, so that later calls to
+	 * gss_acquire_cred will find the delegated credentials we stored.
+	 */
+	setenv("KRB5CCNAME", GSS_MEMORY_CACHE, 1);
+}
diff --git a/src/backend/libpq/be-secure-gssapi.c b/src/backend/libpq/be-secure-gssapi.c
index 3b55f43199..73f8ce8554 100644
--- a/src/backend/libpq/be-secure-gssapi.c
+++ b/src/backend/libpq/be-secure-gssapi.c
@@ -497,6 +497,7 @@ secure_open_gssapi(Port *port)
 	bool		complete_next = false;
 	OM_uint32	major,
 				minor;
+	gss_cred_id_t delegated_creds;
 
 	/*
 	 * Allocate subsidiary Port data for GSSAPI operations.
@@ -504,6 +505,9 @@ secure_open_gssapi(Port *port)
 	port->gss = (pg_gssinfo *)
 		MemoryContextAllocZero(TopMemoryContext, sizeof(pg_gssinfo));
 
+	delegated_creds = GSS_C_NO_CREDENTIAL;
+	port->gss->delegated_creds = false;
+
 	/*
 	 * Allocate buffers and initialize state variables.  By malloc'ing the
 	 * buffers at this point, we avoid wasting static data space in processes
@@ -588,7 +592,8 @@ secure_open_gssapi(Port *port)
 									   GSS_C_NO_CREDENTIAL, &input,
 									   GSS_C_NO_CHANNEL_BINDINGS,
 									   &port->gss->name, NULL, &output, NULL,
-									   NULL, NULL);
+									   NULL, pg_gss_accept_deleg ? &delegated_creds : NULL);
+
 		if (GSS_ERROR(major))
 		{
 			pg_GSS_error(_("could not accept GSSAPI security context"),
@@ -605,6 +610,12 @@ secure_open_gssapi(Port *port)
 			complete_next = true;
 		}
 
+		if (delegated_creds != GSS_C_NO_CREDENTIAL)
+		{
+			pg_store_delegated_credential(delegated_creds);
+			port->gss->delegated_creds = true;
+		}
+
 		/* Done handling the incoming packet, reset our buffer */
 		PqGSSRecvLength = 0;
 
@@ -731,3 +742,16 @@ be_gssapi_get_princ(Port *port)
 
 	return port->gss->princ;
 }
+
+/*
+ * Return if GSSAPI delegated credentials were included on this
+ * connection.
+ */
+bool
+be_gssapi_get_deleg(Port *port)
+{
+	if (!port || !port->gss)
+		return NULL;
+
+	return port->gss->delegated_creds;
+}
diff --git a/src/backend/utils/activity/backend_status.c b/src/backend/utils/activity/backend_status.c
index 608d01ea0d..391d5de043 100644
--- a/src/backend/utils/activity/backend_status.c
+++ b/src/backend/utils/activity/backend_status.c
@@ -384,6 +384,7 @@ pgstat_bestart(void)
 		lbeentry.st_gss = true;
 		lgssstatus.gss_auth = be_gssapi_get_auth(MyProcPort);
 		lgssstatus.gss_enc = be_gssapi_get_enc(MyProcPort);
+		lgssstatus.gss_deleg = be_gssapi_get_deleg(MyProcPort);
 		if (princ)
 			strlcpy(lgssstatus.gss_princ, princ, NAMEDATALEN);
 	}
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 840e9ad86c..6b3c464db8 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -303,7 +303,7 @@ pg_stat_get_progress_info(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_activity(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_ACTIVITY_COLS	30
+#define PG_STAT_GET_ACTIVITY_COLS	31
 	int			num_backends = pgstat_fetch_stat_numbackends();
 	int			curr_backend;
 	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
@@ -395,7 +395,7 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			pfree(clipped_activity);
 
 			/* leader_pid */
-			nulls[28] = true;
+			nulls[29] = true;
 
 			proc = BackendPidGetProc(beentry->st_procpid);
 
@@ -432,8 +432,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 				 */
 				if (leader && leader->pid != beentry->st_procpid)
 				{
-					values[28] = Int32GetDatum(leader->pid);
-					nulls[28] = false;
+					values[29] = Int32GetDatum(leader->pid);
+					nulls[29] = false;
 				}
 				else if (beentry->st_backendType == B_BG_WORKER)
 				{
@@ -441,8 +441,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 
 					if (leader_pid != InvalidPid)
 					{
-						values[28] = Int32GetDatum(leader_pid);
-						nulls[28] = false;
+						values[29] = Int32GetDatum(leader_pid);
+						nulls[29] = false;
 					}
 				}
 			}
@@ -600,6 +600,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 				values[25] = BoolGetDatum(beentry->st_gssstatus->gss_auth); /* gss_auth */
 				values[26] = CStringGetTextDatum(beentry->st_gssstatus->gss_princ);
 				values[27] = BoolGetDatum(beentry->st_gssstatus->gss_enc);	/* GSS Encryption in use */
+				values[28] = BoolGetDatum(beentry->st_gssstatus->gss_deleg);	/* GSS credentials
+																				 * delegated */
 			}
 			else
 			{
@@ -607,11 +609,13 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 				nulls[26] = true;	/* No GSS principal */
 				values[27] = BoolGetDatum(false);	/* GSS Encryption not in
 													 * use */
+				values[28] = BoolGetDatum(false);	/* GSS credentials not
+													 * delegated */
 			}
 			if (beentry->st_query_id == 0)
-				nulls[29] = true;
+				nulls[30] = true;
 			else
-				values[29] = UInt64GetDatum(beentry->st_query_id);
+				values[30] = UInt64GetDatum(beentry->st_query_id);
 		}
 		else
 		{
@@ -640,6 +644,7 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			nulls[27] = true;
 			nulls[28] = true;
 			nulls[29] = true;
+			nulls[30] = true;
 		}
 
 		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 60feae0f1b..5af87a7868 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -282,15 +282,17 @@ PerformAuthentication(Port *port)
 
 			if (princ)
 				appendStringInfo(&logmsg,
-								 _(" GSS (authenticated=%s, encrypted=%s, principal=%s)"),
+								 _(" GSS (authenticated=%s, encrypted=%s, deleg_credentials=%s, principal=%s)"),
 								 be_gssapi_get_auth(port) ? _("yes") : _("no"),
 								 be_gssapi_get_enc(port) ? _("yes") : _("no"),
+								 be_gssapi_get_deleg(port) ? _("yes") : _("no"),
 								 princ);
 			else
 				appendStringInfo(&logmsg,
-								 _(" GSS (authenticated=%s, encrypted=%s)"),
+								 _(" GSS (authenticated=%s, encrypted=%s, deleg_credentials=%s)"),
 								 be_gssapi_get_auth(port) ? _("yes") : _("no"),
-								 be_gssapi_get_enc(port) ? _("yes") : _("no"));
+								 be_gssapi_get_enc(port) ? _("yes") : _("no"),
+								 be_gssapi_get_deleg(port) ? _("yes") : _("no"));
 		}
 #endif
 
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index cf7f465ddb..97edc61a14 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -1727,6 +1727,16 @@ struct config_bool ConfigureNamesBool[] =
 	},
 
 	{
+		{"gss_accept_deleg", PGC_SIGHUP, CONN_AUTH_AUTH,
+			gettext_noop("Sets whether GSSAPI delegation should be accepted from the client."),
+			NULL
+		},
+		&pg_gss_accept_deleg,
+		false,
+		NULL, NULL, NULL
+	},
+
+	{
 		{"escape_string_warning", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
 			gettext_noop("Warn about backslash escapes in ordinary string literals."),
 			NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index e715aff3b8..dce5049bc2 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -101,6 +101,7 @@
 # GSSAPI using Kerberos
 #krb_server_keyfile = 'FILE:${sysconfdir}/krb5.keytab'
 #krb_caseins_users = off
+#gss_accept_deleg = off
 
 # - SSL -
 
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3605a5a14c..6291d76a4c 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5438,9 +5438,9 @@
   proname => 'pg_stat_get_activity', prorows => '100', proisstrict => 'f',
   proretset => 't', provolatile => 's', proparallel => 'r',
   prorettype => 'record', proargtypes => 'int4',
-  proallargtypes => '{int4,oid,int4,oid,text,text,text,text,text,timestamptz,timestamptz,timestamptz,timestamptz,inet,text,int4,xid,xid,text,bool,text,text,int4,text,numeric,text,bool,text,bool,int4,int8}',
-  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,leader_pid,query_id}',
+  proallargtypes => '{int4,oid,int4,oid,text,text,text,text,text,timestamptz,timestamptz,timestamptz,timestamptz,inet,text,int4,xid,xid,text,bool,text,text,int4,text,numeric,text,bool,text,bool,bool,int4,int8}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{pid,datid,pid,usesysid,application_name,state,query,wait_event_type,wait_event,xact_start,query_start,backend_start,state_change,client_addr,client_hostname,client_port,backend_xid,backend_xmin,backend_type,ssl,sslversion,sslcipher,sslbits,ssl_client_dn,ssl_client_serial,ssl_issuer_dn,gss_auth,gss_princ,gss_enc,gss_deleg,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
 { oid => '3318',
   descr => 'statistics: information about progress of backends running maintenance command',
diff --git a/src/include/libpq/auth.h b/src/include/libpq/auth.h
index 9916c99df1..e4d0e38c1e 100644
--- a/src/include/libpq/auth.h
+++ b/src/include/libpq/auth.h
@@ -18,6 +18,7 @@
 
 extern PGDLLIMPORT char *pg_krb_server_keyfile;
 extern PGDLLIMPORT bool pg_krb_caseins_users;
+extern PGDLLIMPORT bool pg_gss_accept_deleg;
 extern PGDLLIMPORT char *pg_krb_realm;
 
 extern void ClientAuthentication(Port *port);
diff --git a/src/include/libpq/be-gssapi-common.h b/src/include/libpq/be-gssapi-common.h
index facd24ff7f..0381f0ce77 100644
--- a/src/include/libpq/be-gssapi-common.h
+++ b/src/include/libpq/be-gssapi-common.h
@@ -18,13 +18,16 @@
 
 #if defined(HAVE_GSSAPI_H)
 #include <gssapi.h>
+#include <gssapi_ext.h>
 #else
 #include <gssapi/gssapi.h>
+#include <gssapi/gssapi_ext.h>
 #endif
 
 extern void pg_GSS_error(const char *errmsg,
 						 OM_uint32 maj_stat, OM_uint32 min_stat);
 
+extern void pg_store_delegated_credential(gss_cred_id_t cred);
 #endif							/* ENABLE_GSS */
 
 #endif							/* BE_GSSAPI_COMMON_H */
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index ac6407e9f6..e9df4295e2 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -84,6 +84,7 @@ typedef struct
 								 * GSSAPI auth was not used */
 	bool		auth;			/* GSSAPI Authentication used */
 	bool		enc;			/* GSSAPI encryption in use */
+	bool		delegated_creds;	/* GSSAPI Delegated credentials */
 #endif
 } pg_gssinfo;
 #endif
@@ -328,6 +329,7 @@ extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 extern bool be_gssapi_get_auth(Port *port);
 extern bool be_gssapi_get_enc(Port *port);
 extern const char *be_gssapi_get_princ(Port *port);
+extern bool be_gssapi_get_deleg(Port *port);
 
 /* Read and write to a GSSAPI-encrypted connection. */
 extern ssize_t be_gssapi_read(Port *port, void *ptr, size_t len);
diff --git a/src/include/utils/backend_status.h b/src/include/utils/backend_status.h
index f7bd83113a..9651cb1d0c 100644
--- a/src/include/utils/backend_status.h
+++ b/src/include/utils/backend_status.h
@@ -77,6 +77,7 @@ typedef struct PgBackendGSSStatus
 	char		gss_princ[NAMEDATALEN]; /* GSSAPI Principal used to auth */
 	bool		gss_auth;		/* If GSSAPI authentication was used */
 	bool		gss_enc;		/* If encryption is being used */
+	bool		gss_deleg;		/* If credentials delegated */
 
 } PgBackendGSSStatus;
 
diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt
index e8bcc88370..7ded77aff3 100644
--- a/src/interfaces/libpq/exports.txt
+++ b/src/interfaces/libpq/exports.txt
@@ -186,3 +186,4 @@ PQpipelineStatus          183
 PQsetTraceFlags           184
 PQmblenBounded            185
 PQsendFlushRequest        186
+PQconnectionUsedGSSAPI    187
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index b0550e6332..fe2634230a 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -58,7 +58,8 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 {
 	OM_uint32	maj_stat,
 				min_stat,
-				lmin_s;
+				lmin_s,
+				gss_flags = GSS_C_MUTUAL_FLAG;
 	gss_buffer_desc ginbuf;
 	gss_buffer_desc goutbuf;
 
@@ -92,12 +93,19 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 		ginbuf.value = NULL;
 	}
 
+	/* Only try to acquire credentials if GSS delegation isn't disabled. */
+	if (!pg_GSS_have_cred_cache(&conn->gcred))
+		conn->gcred = GSS_C_NO_CREDENTIAL;
+
+	if (conn->gssdeleg && pg_strcasecmp(conn->gssdeleg, "enable") == 0)
+		gss_flags |= GSS_C_DELEG_FLAG;
+
 	maj_stat = gss_init_sec_context(&min_stat,
-									GSS_C_NO_CREDENTIAL,
+									conn->gcred,
 									&conn->gctx,
 									conn->gtarg_nam,
 									GSS_C_NO_OID,
-									GSS_C_MUTUAL_FLAG,
+									gss_flags,
 									0,
 									GSS_C_NO_CHANNEL_BINDINGS,
 									(ginbuf.value == NULL) ? GSS_C_NO_BUFFER : &ginbuf,
@@ -139,6 +147,7 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 	{
 		conn->client_finished_auth = true;
 		gss_release_name(&lmin_s, &conn->gtarg_nam);
+		conn->gssapi_used = true;
 	}
 
 	return STATUS_OK;
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 40fef0e2c8..fcd3d0d9a3 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -343,6 +343,10 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"GSS-library", "", 7,	/* sizeof("gssapi") == 7 */
 	offsetof(struct pg_conn, gsslib)},
 
+	{"gssdeleg", "PGGSSDELEG", NULL, NULL,
+		"GSS-delegation", "", 8,	/* sizeof("disable") == 8 */
+	offsetof(struct pg_conn, gssdeleg)},
+
 	{"replication", NULL, NULL, NULL,
 		"Replication", "D", 5,
 	offsetof(struct pg_conn, replication)},
@@ -617,6 +621,7 @@ pqDropServerData(PGconn *conn)
 	conn->auth_req_received = false;
 	conn->client_finished_auth = false;
 	conn->password_needed = false;
+	conn->gssapi_used = false;
 	conn->write_failed = false;
 	free(conn->write_err_msg);
 	conn->write_err_msg = NULL;
@@ -4448,6 +4453,7 @@ freePGconn(PGconn *conn)
 	free(conn->gssencmode);
 	free(conn->krbsrvname);
 	free(conn->gsslib);
+	free(conn->gssdeleg);
 	free(conn->connip);
 	/* Note that conn->Pfdebug is not ours to close or free */
 	free(conn->write_err_msg);
@@ -7313,6 +7319,17 @@ PQconnectionUsedPassword(const PGconn *conn)
 }
 
 int
+PQconnectionUsedGSSAPI(const PGconn *conn)
+{
+	if (!conn)
+		return false;
+	if (conn->gssapi_used)
+		return true;
+	else
+		return false;
+}
+
+int
 PQclientEncoding(const PGconn *conn)
 {
 	if (!conn || conn->status != CONNECTION_OK)
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 038e847b7e..bf87ae3fd1 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -477,7 +477,8 @@ pqsecure_open_gss(PGconn *conn)
 {
 	ssize_t		ret;
 	OM_uint32	major,
-				minor;
+				minor,
+				gss_flags = GSS_REQUIRED_FLAGS;
 	uint32		netlen;
 	PostgresPollingStatusType result;
 	gss_buffer_desc input = GSS_C_EMPTY_BUFFER,
@@ -621,13 +622,30 @@ pqsecure_open_gss(PGconn *conn)
 	if (ret != STATUS_OK)
 		return PGRES_POLLING_FAILED;
 
+	if (conn->gssdeleg && pg_strcasecmp(conn->gssdeleg, "enable") == 0)
+	{
+		/* Acquire credentials if possbile */
+		if (conn->gcred == GSS_C_NO_CREDENTIAL)
+			(void) pg_GSS_have_cred_cache(&conn->gcred);
+
+		/*
+		 * We have credentials and gssdeleg is enabled, so request credential
+		 * delegation.  This may or may not actually result in credentials
+		 * being delegated- it depends on if the forwardable flag has been set
+		 * in the credential and if the server is configured to accept
+		 * delegated credentials.
+		 */
+		if (conn->gcred != GSS_C_NO_CREDENTIAL)
+			gss_flags |= GSS_C_DELEG_FLAG;
+	}
+
 	/*
 	 * Call GSS init context, either with an empty input, or with a complete
 	 * packet from the server.
 	 */
 	major = gss_init_sec_context(&minor, conn->gcred, &conn->gctx,
 								 conn->gtarg_nam, GSS_C_NO_OID,
-								 GSS_REQUIRED_FLAGS, 0, 0, &input, NULL,
+								 gss_flags, 0, 0, &input, NULL,
 								 &output, NULL, NULL);
 
 	/* GSS Init Sec Context uses the whole packet, so clear it */
@@ -647,6 +665,7 @@ pqsecure_open_gss(PGconn *conn)
 		 * to do GSS wrapping/unwrapping.
 		 */
 		conn->gssenc = true;
+		conn->gssapi_used = true;
 
 		/* Clean up */
 		gss_release_cred(&minor, &conn->gcred);
diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index f3d9220496..7476dbe0e9 100644
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -354,6 +354,7 @@ extern int	PQbackendPID(const PGconn *conn);
 extern PGpipelineStatus PQpipelineStatus(const PGconn *conn);
 extern int	PQconnectionNeedsPassword(const PGconn *conn);
 extern int	PQconnectionUsedPassword(const PGconn *conn);
+extern int	PQconnectionUsedGSSAPI(const PGconn *conn);
 extern int	PQclientEncoding(const PGconn *conn);
 extern int	PQsetClientEncoding(PGconn *conn, const char *encoding);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index d93e976ca5..ce0167c1b6 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -404,6 +404,7 @@ struct pg_conn
 	char	   *krbsrvname;		/* Kerberos service name */
 	char	   *gsslib;			/* What GSS library to use ("gssapi" or
 								 * "sspi") */
+	char	   *gssdeleg;		/* Try to delegate GSS credentials? */
 	char	   *ssl_min_protocol_version;	/* minimum TLS protocol version */
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
@@ -465,6 +466,7 @@ struct pg_conn
 	int			sversion;		/* server version, e.g. 70401 for 7.4.1 */
 	bool		auth_req_received;	/* true if any type of auth req received */
 	bool		password_needed;	/* true if server demanded a password */
+	bool		gssapi_used;	/* true if authenticated via gssapi */
 	bool		sigpipe_so;		/* have we masked SIGPIPE via SO_NOSIGPIPE? */
 	bool		sigpipe_flag;	/* can we mask SIGPIPE via MSG_NOSIGNAL? */
 	bool		write_failed;	/* have we had a write failure on sock? */
diff --git a/src/test/kerberos/Makefile b/src/test/kerberos/Makefile
index 7765f3f93b..f460d2c0e7 100644
--- a/src/test/kerberos/Makefile
+++ b/src/test/kerberos/Makefile
@@ -13,6 +13,9 @@ subdir = src/test/kerberos
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
+EXTRA_INSTALL += contrib/postgres_fdw
+EXTRA_INSTALL += contrib/dblink
+
 export with_gssapi with_krb_srvnam
 
 check:
diff --git a/src/test/kerberos/t/001_auth.pl b/src/test/kerberos/t/001_auth.pl
index 458246b4d7..bf12752529 100644
--- a/src/test/kerberos/t/001_auth.pl
+++ b/src/test/kerberos/t/001_auth.pl
@@ -7,6 +7,9 @@
 # that the server-side pg_stat_gssapi view reports what we expect to
 # see for each test and that SYSTEM_USER returns what we expect to see.
 #
+# Also test that GSSAPI delegation is working properly and that those
+# credentials can be used to make dblink / postgres_fdw connections.
+#
 # Since this requires setting up a full KDC, it doesn't make much sense
 # to have multiple test scripts (since they'd have to also create their
 # own KDC and that could cause race conditions or other problems)- so
@@ -56,6 +59,7 @@ elsif ($^O eq 'linux')
 
 my $krb5_config  = 'krb5-config';
 my $kinit        = 'kinit';
+my $klist        = 'klist';
 my $kdb5_util    = 'kdb5_util';
 my $kadmin_local = 'kadmin.local';
 my $krb5kdc      = 'krb5kdc';
@@ -64,6 +68,7 @@ if ($krb5_bin_dir && -d $krb5_bin_dir)
 {
 	$krb5_config = $krb5_bin_dir . '/' . $krb5_config;
 	$kinit       = $krb5_bin_dir . '/' . $kinit;
+	$klist       = $krb5_bin_dir . '/' . $klist;
 }
 if ($krb5_sbin_dir && -d $krb5_sbin_dir)
 {
@@ -86,6 +91,8 @@ my $kdc_datadir = "${PostgreSQL::Test::Utils::tmp_check}/krb5kdc";
 my $kdc_pidfile = "${PostgreSQL::Test::Utils::tmp_check}/krb5kdc.pid";
 my $keytab      = "${PostgreSQL::Test::Utils::tmp_check}/krb5.keytab";
 
+my $pgpass      = "${PostgreSQL::Test::Utils::tmp_check}/.pgpass";
+
 my $dbname      = 'postgres';
 my $username    = 'test1';
 my $application = '001_auth.pl';
@@ -100,6 +107,14 @@ $stdout =~ m/Kerberos 5 release ([0-9]+\.[0-9]+)/
   or BAIL_OUT("could not get Kerberos version");
 $krb5_version = $1;
 
+# Construct a pgpass file to make sure we don't use it
+append_to_file(
+	$pgpass,
+	'*:*:*:*:abc123'
+);
+
+chmod 0600, $pgpass;
+
 # Build the krb5.conf to use.
 #
 # Explicitly specify the default (test) realm and the KDC for
@@ -126,12 +141,14 @@ kdc = FILE:$kdc_log
 dns_lookup_realm = false
 dns_lookup_kdc = false
 default_realm = $realm
+forwardable = false
 rdns = false
 
 [realms]
 $realm = {
     kdc = $hostaddr:$kdc_port
-}!);
+}
+!);
 
 append_to_file(
 	$kdc_conf,
@@ -204,7 +221,28 @@ lc_messages = 'C'
 });
 $node->start;
 
+my $port = $node->port();
+
 $node->safe_psql('postgres', 'CREATE USER test1;');
+$node->safe_psql('postgres', "CREATE USER test2 WITH ENCRYPTED PASSWORD 'abc123';");
+$node->safe_psql('postgres', 'CREATE EXTENSION postgres_fdw;');
+$node->safe_psql('postgres', 'CREATE EXTENSION dblink;');
+$node->safe_psql('postgres', "CREATE SERVER s1 FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host '$host', hostaddr '$hostaddr', port '$port', dbname 'postgres');");
+$node->safe_psql('postgres', "CREATE SERVER s2 FOREIGN DATA WRAPPER postgres_fdw OPTIONS (port '$port', dbname 'postgres', passfile '$pgpass');");
+
+$node->safe_psql('postgres', 'GRANT USAGE ON FOREIGN SERVER s1 TO test1;');
+
+$node->safe_psql('postgres', "CREATE USER MAPPING FOR test1 SERVER s1 OPTIONS (user 'test1');");
+$node->safe_psql('postgres', "CREATE USER MAPPING FOR test1 SERVER s2 OPTIONS (user 'test2');");
+
+$node->safe_psql('postgres', "CREATE TABLE t1 (c1 int);");
+$node->safe_psql('postgres', "INSERT INTO t1 VALUES (1);");
+$node->safe_psql('postgres', "CREATE FOREIGN TABLE tf1 (c1 int) SERVER s1 OPTIONS (schema_name 'public', table_name 't1');");
+$node->safe_psql('postgres', "GRANT SELECT ON t1 TO test1;");
+$node->safe_psql('postgres', "GRANT SELECT ON tf1 TO test1;");
+
+$node->safe_psql('postgres', "CREATE FOREIGN TABLE tf2 (c1 int) SERVER s2 OPTIONS (schema_name 'public', table_name 't1');");
+$node->safe_psql('postgres', "GRANT SELECT ON tf2 TO test1;");
 
 # Set up a table for SYSTEM_USER parallel worker testing.
 $node->safe_psql('postgres',
@@ -271,12 +309,16 @@ sub test_query
 
 unlink($node->data_dir . '/pg_hba.conf');
 $node->append_conf('pg_hba.conf',
-	qq{host all all $hostaddr/32 gss map=mymap});
+	qq{
+local all test2 scram-sha-256
+host all all $hostaddr/32 gss map=mymap
+});
 $node->restart;
 
 test_access($node, 'test1', 'SELECT true', 2, '', 'fails without ticket');
 
 run_log [ $kinit, 'test1' ], \$test1_password or BAIL_OUT($?);
+run_log [ $klist, '-f' ] or BAIL_OUT($?);
 
 test_access(
 	$node,
@@ -294,35 +336,58 @@ $node->restart;
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated AND encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
 	'',
-	'succeeds with mapping with default gssencmode and host hba',
+	'succeeds with mapping with default gssencmode and host hba, ticket not forwardable',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
 );
 
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated AND encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
 	'gssencmode=prefer',
-	'succeeds with GSS-encrypted access preferred with host hba',
+	'succeeds with GSS-encrypted access preferred with host hba, ticket not forwardable',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
 );
+
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated AND encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
 	'gssencmode=require',
-	'succeeds with GSS-encrypted access required with host hba',
+	'succeeds with GSS-encrypted access required with host hba, ticket not forwardable',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
 );
 
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
+	0,
+	'gssencmode=prefer gssdeleg=enable',
+	'succeeds with GSS-encrypted access preferred with host hba and credentials not delegated even though asked for (ticket not forwardable)',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
+);
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
+	0,
+	'gssencmode=require gssdeleg=enable',
+	'succeeds with GSS-encrypted access required with host hba and credentials not delegated even though asked for (ticket not forwardable)',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
+);
+
+
 # Test that we can transport a reasonable amount of data.
 test_query(
 	$node,
@@ -389,29 +454,164 @@ test_query(
 
 unlink($node->data_dir . '/pg_hba.conf');
 $node->append_conf('pg_hba.conf',
-	qq{hostgssenc all all $hostaddr/32 gss map=mymap});
+	qq{
+    local all test2 scram-sha-256
+	hostgssenc all all $hostaddr/32 gss map=mymap
+});
+
+string_replace_file($krb5_conf, "forwardable = false", "forwardable = true");
+
+run_log [ $kinit, 'test1' ], \$test1_password or BAIL_OUT($?);
+run_log [ $klist, '-f' ] or BAIL_OUT($?);
+
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated from pg_stat_gssapi where pid = pg_backend_pid();',
+	0,
+	'gssencmode=prefer gssdeleg=enable',
+	'succeeds with GSS-encrypted access preferred and hostgssenc hba and credentials not forwarded (server does not accept them, default)',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
+);
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated from pg_stat_gssapi where pid = pg_backend_pid();',
+	0,
+	'gssencmode=require gssdeleg=enable',
+	'succeeds with GSS-encrypted access required and hostgssenc hba and credentials not forwarded (server does not accept them, default)',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
+);
+
+$node->append_conf('postgresql.conf',
+	qq{gss_accept_deleg=off});
+$node->restart;
+
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated from pg_stat_gssapi where pid = pg_backend_pid();',
+	0,
+	'gssencmode=prefer gssdeleg=enable',
+	'succeeds with GSS-encrypted access preferred and hostgssenc hba and credentials not forwarded (server does not accept them, explicitly disabled)',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
+);
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated from pg_stat_gssapi where pid = pg_backend_pid();',
+	0,
+	'gssencmode=require gssdeleg=enable',
+	'succeeds with GSS-encrypted access required and hostgssenc hba and credentials not forwarded (server does not accept them, explicitly disabled)',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
+);
+
+$node->append_conf('postgresql.conf',
+	qq{gss_accept_deleg=on});
 $node->restart;
 
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated AND encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND encrypted AND credentials_delegated from pg_stat_gssapi where pid = pg_backend_pid();',
+	0,
+	'gssencmode=prefer gssdeleg=enable',
+	'succeeds with GSS-encrypted access preferred and hostgssenc hba and credentials forwarded',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=yes, principal=test1\@$realm)"
+);
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND credentials_delegated from pg_stat_gssapi where pid = pg_backend_pid();',
+	0,
+	'gssencmode=require gssdeleg=enable',
+	'succeeds with GSS-encrypted access required and hostgssenc hba and credentials forwarded',
+	"connection authenticated: identity=\"test1\@$realm\" method=gss",
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=yes, principal=test1\@$realm)"
+);
+test_access(
+	$node,
+	'test1',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
 	'gssencmode=prefer',
-	'succeeds with GSS-encrypted access preferred and hostgssenc hba',
+	'succeeds with GSS-encrypted access preferred and hostgssenc hba and credentials not forwarded',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
 );
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated AND encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND encrypted AND NOT credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
-	'gssencmode=require',
-	'succeeds with GSS-encrypted access required and hostgssenc hba',
+	'gssencmode=require gssdeleg=disable',
+	'succeeds with GSS-encrypted access required and hostgssenc hba and credentials explicitly not forwarded',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=no, principal=test1\@$realm)"
+);
+
+my $psql_out = '';
+my $psql_stderr = '';
+my $psql_rc = '';
+
+$psql_rc = $node->psql(
+    'postgres',
+	"SELECT * FROM dblink('user=test1 dbname=$dbname host=$host hostaddr=$hostaddr port=$port','select 1') as t1(c1 int);",
+	connstr => "user=test1 host=$host hostaddr=$hostaddr gssencmode=require gssdeleg=disable",
+	stdout => \$psql_out,
+	stderr => \$psql_stderr
+);
+is($psql_rc,'3','dblink attempt fails without delegated credentials');
+like($psql_stderr, qr/password or GSSAPI delegated credentials required/,'dblink does not work without delegated credentials');
+like($psql_out, qr/^$/,'dblink does not work without delegated credentials');
+
+$psql_out = '';
+$psql_stderr = '';
+
+$psql_rc = $node->psql(
+    'postgres',
+	"SELECT * FROM dblink('user=test2 dbname=$dbname port=$port passfile=$pgpass','select 1') as t1(c1 int);",
+	connstr => "user=test1 host=$host hostaddr=$hostaddr gssencmode=require gssdeleg=disable",
+	stdout => \$psql_out,
+	stderr => \$psql_stderr
 );
+is($psql_rc,'3','dblink does not work without delegated credentials and with passfile');
+like($psql_stderr, qr/password or GSSAPI delegated credentials required/,'dblink does not work without delegated credentials and with passfile');
+like($psql_out, qr/^$/,'dblink does not work without delegated credentials and with passfile');
+
+$psql_out = '';
+$psql_stderr = '';
+
+$psql_rc = $node->psql(
+    'postgres',
+	"TABLE tf1;",
+	connstr => "user=test1 host=$host hostaddr=$hostaddr gssencmode=require gssdeleg=disable",
+	stdout => \$psql_out,
+	stderr => \$psql_stderr
+);
+is($psql_rc,'3','postgres_fdw does not work without delegated credentials');
+like($psql_stderr, qr/password or GSSAPI delegated credentials required/,'postgres_fdw does not work without delegated credentials');
+like($psql_out, qr/^$/,'postgres_fdw does not work without delegated credentials');
+
+$psql_out = '';
+$psql_stderr = '';
+
+$psql_rc = $node->psql(
+    'postgres',
+	"TABLE tf2;",
+	connstr => "user=test1 host=$host hostaddr=$hostaddr gssencmode=require gssdeleg=disable",
+	stdout => \$psql_out,
+	stderr => \$psql_stderr
+);
+is($psql_rc,'3','postgres_fdw does not work without delegated credentials and with passfile');
+like($psql_stderr, qr/password or GSSAPI delegated credentials required/,'postgres_fdw does not work without delegated credentials and with passfile');
+like($psql_out, qr/^$/,'postgres_fdw does not work without delegated credentials and with passfile');
+
 test_access($node, 'test1', 'SELECT true', 2, 'gssencmode=disable',
 	'fails with GSS encryption disabled and hostgssenc hba');
 
@@ -427,54 +627,123 @@ $node->connect_ok(
 
 unlink($node->data_dir . '/pg_hba.conf');
 $node->append_conf('pg_hba.conf',
-	qq{hostnogssenc all all $hostaddr/32 gss map=mymap});
+	qq{
+    local all test2 scram-sha-256
+	hostnogssenc all all $hostaddr/32 gss map=mymap
+});
 $node->restart;
 
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated and not encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND NOT encrypted AND credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
-	'gssencmode=prefer',
+	'gssencmode=prefer gssdeleg=enable',
 	'succeeds with GSS-encrypted access preferred and hostnogssenc hba, but no encryption',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=no, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=no, deleg_credentials=yes, principal=test1\@$realm)"
 );
 test_access($node, 'test1', 'SELECT true', 2, 'gssencmode=require',
 	'fails with GSS-encrypted access required and hostnogssenc hba');
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated and not encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND NOT encrypted AND credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
-	'gssencmode=disable',
+	'gssencmode=disable gssdeleg=enable',
 	'succeeds with GSS encryption disabled and hostnogssenc hba',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=no, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=no, deleg_credentials=yes, principal=test1\@$realm)"
+);
+
+test_query(
+	$node,
+	'test1',
+	"SELECT * FROM dblink('user=test1 dbname=$dbname host=$host hostaddr=$hostaddr port=$port','select 1') as t1(c1 int);",
+	qr/^1$/s,
+	'gssencmode=prefer gssdeleg=enable',
+	'dblink works not-encrypted (server not configured to accept encrypted GSSAPI connections)');
+
+test_query(
+	$node,
+	'test1',
+	"TABLE tf1;",
+	qr/^1$/s,
+	'gssencmode=prefer gssdeleg=enable',
+	'postgres_fdw works not-encrypted (server not configured to accept encrypted GSSAPI connections)');
+
+$psql_out = '';
+$psql_stderr = '';
+
+$psql_rc = $node->psql(
+    'postgres',
+	"SELECT * FROM dblink('user=test2 dbname=$dbname port=$port passfile=$pgpass','select 1') as t1(c1 int);",
+	connstr => "user=test1 host=$host hostaddr=$hostaddr gssencmode=prefer gssdeleg=enable",
+	stdout => \$psql_out,
+	stderr => \$psql_stderr
+);
+is($psql_rc,'3','dblink does not work with delegated credentials and with passfile');
+like($psql_stderr, qr/password or GSSAPI delegated credentials required/,'dblink does not work with delegated credentials and with passfile');
+like($psql_out, qr/^$/,'dblink does not work with delegated credentials and with passfile');
+
+$psql_out = '';
+$psql_stderr = '';
+
+$psql_rc = $node->psql(
+    'postgres',
+	"TABLE tf2;",
+	connstr => "user=test1 host=$host hostaddr=$hostaddr gssencmode=prefer gssdeleg=enable",
+	stdout => \$psql_out,
+	stderr => \$psql_stderr
 );
+is($psql_rc,'3','postgres_fdw does not work with delegated credentials and with passfile');
+like($psql_stderr, qr/password or GSSAPI delegated credentials required/,'postgres_fdw does not work with delegated credentials and with passfile');
+like($psql_out, qr/^$/,'postgres_fdw does not work with delegated credentials and with passfile');
 
 truncate($node->data_dir . '/pg_ident.conf', 0);
 unlink($node->data_dir . '/pg_hba.conf');
 $node->append_conf('pg_hba.conf',
-	qq{host all all $hostaddr/32 gss include_realm=0});
+	qq{
+    local all test2 scram-sha-256
+	host all all $hostaddr/32 gss include_realm=0
+});
 $node->restart;
 
 test_access(
 	$node,
 	'test1',
-	'SELECT gss_authenticated AND encrypted from pg_stat_gssapi where pid = pg_backend_pid();',
+	'SELECT gss_authenticated AND encrypted AND credentials_delegated FROM pg_stat_gssapi WHERE pid = pg_backend_pid();',
 	0,
-	'',
+	'gssdeleg=enable',
 	'succeeds with include_realm=0 and defaults',
 	"connection authenticated: identity=\"test1\@$realm\" method=gss",
-	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, principal=test1\@$realm)"
+	"connection authorized: user=$username database=$dbname application_name=$application GSS (authenticated=yes, encrypted=yes, deleg_credentials=yes, principal=test1\@$realm)"
 );
 
+test_query(
+	$node,
+	'test1',
+	"SELECT * FROM dblink('user=test1 dbname=$dbname host=$host hostaddr=$hostaddr port=$port password=1234','select 1') as t1(c1 int);",
+	qr/^1$/s,
+	'gssencmode=require gssdeleg=enable',
+	'dblink works encrypted');
+
+test_query(
+	$node,
+	'test1',
+	"TABLE tf1;",
+	qr/^1$/s,
+	'gssencmode=require gssdeleg=enable',
+	'postgres_fdw works encrypted');
+
 # Reset pg_hba.conf, and cause a usermap failure with an authentication
 # that has passed.
 unlink($node->data_dir . '/pg_hba.conf');
 $node->append_conf('pg_hba.conf',
-	qq{host all all $hostaddr/32 gss include_realm=0 krb_realm=EXAMPLE.ORG});
+	qq{
+    local all test2 scram-sha-256
+	host all all $hostaddr/32 gss include_realm=0 krb_realm=EXAMPLE.ORG
+});
 $node->restart;
 
 test_access(
diff --git a/src/test/perl/PostgreSQL/Test/Utils.pm b/src/test/perl/PostgreSQL/Test/Utils.pm
index 878e12b15e..9249954b49 100644
--- a/src/test/perl/PostgreSQL/Test/Utils.pm
+++ b/src/test/perl/PostgreSQL/Test/Utils.pm
@@ -65,6 +65,7 @@ our @EXPORT = qw(
   slurp_dir
   slurp_file
   append_to_file
+  string_replace_file
   check_mode_recursive
   chmod_recursive
   check_pg_config
@@ -549,6 +550,32 @@ sub append_to_file
 
 =pod
 
+=item string_replace_file(filename, find, replace)
+
+Find and replace string of a given file.
+
+=cut
+
+sub string_replace_file
+{
+	my ($filename, $find, $replace) = @_;
+	open(my $in, '<', $filename);
+	my $content;
+	while(<$in>)
+	{
+		$_ =~ s/$find/$replace/;
+		$content = $content.$_;
+	}
+	close $in;
+	open(my $out, '>', $filename);
+	print $out $content;
+	close($out);
+
+	return;
+}
+
+=pod
+
 =item check_mode_recursive(dir, expected_dir_mode, expected_file_mode, ignore_list)
 
 Check that all file/dir modes in a directory match the expected values,
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index d939d8067e..8337bac5db 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1759,7 +1759,7 @@ pg_stat_activity| SELECT s.datid,
     s.query_id,
     s.query,
     s.backend_type
-   FROM ((pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, leader_pid, query_id)
+   FROM ((pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, gss_deleg, leader_pid, query_id)
      LEFT JOIN pg_database d ON ((s.datid = d.oid)))
      LEFT JOIN pg_authid u ON ((s.usesysid = u.oid)));
 pg_stat_all_indexes| SELECT c.oid AS relid,
@@ -1874,8 +1874,9 @@ pg_stat_database_conflicts| SELECT oid AS datid,
 pg_stat_gssapi| SELECT pid,
     gss_auth AS gss_authenticated,
     gss_princ AS principal,
-    gss_enc AS encrypted
-   FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, leader_pid, query_id)
+    gss_enc AS encrypted,
+    gss_deleg AS credentials_delegated
+   FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, gss_deleg, leader_pid, query_id)
   WHERE (client_port IS NOT NULL);
 pg_stat_io| SELECT backend_type,
     io_object,
@@ -2073,7 +2074,7 @@ pg_stat_replication| SELECT s.pid,
     w.sync_priority,
     w.sync_state,
     w.reply_time
-   FROM ((pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, leader_pid, query_id)
+   FROM ((pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, gss_deleg, leader_pid, query_id)
      JOIN pg_stat_get_wal_senders() w(pid, state, sent_lsn, write_lsn, flush_lsn, replay_lsn, write_lag, flush_lag, replay_lag, sync_priority, sync_state, reply_time) ON ((s.pid = w.pid)))
      LEFT JOIN pg_authid u ON ((s.usesysid = u.oid)));
 pg_stat_replication_slots| SELECT s.slot_name,
@@ -2107,7 +2108,7 @@ pg_stat_ssl| SELECT pid,
     ssl_client_dn AS client_dn,
     ssl_client_serial AS client_serial,
     ssl_issuer_dn AS issuer_dn
-   FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, leader_pid, query_id)
+   FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, gss_deleg, leader_pid, query_id)
   WHERE (client_port IS NOT NULL);
 pg_stat_subscription| SELECT su.oid AS subid,
     su.subname,