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

5 files changed, 10 insertions, 3 deletions

diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3605a5a14cd..6291d76a4c1 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 9916c99df17..e4d0e38c1ee 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 facd24ff7f9..0381f0ce771 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 ac6407e9f61..e9df4295e20 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 f7bd83113ac..9651cb1d0c0 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;