Fix compilation warnings with libselinux 3.1 in contrib/sepgsql/

Upstream SELinux has recently marked security_context_t as officially
deprecated, causing warnings with -Wdeprecated-declarations.  This is
considered as legacy code for some time now by upstream as
security_context_t got removed from most of the code tree during the
development of 2.3 back in 2014.

This removes all the references to security_context_t in sepgsql/ to be
consistent with SELinux, fixing the warnings.  Note that this does not
impact the minimum version of libselinux supported.

This has been applied first as 1f32136 for 14~, but no other branches
got the call.  This is in line with the recent project policy to have no
warnings in branches where builds should still be supported (9.2~ as of
today).  Per discussion with Tom Lane and Álvaro Herrera.

Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/20200813012735.GC11663@paquier.xyz
Discussion: https://postgr.es/m/20221103181028.raqta27jcuypor4l@alvherre.pgsql
Backpatch-through: 9.2

contrib/sepgsql/label.c

@@ -122,7 +122,7 @@ sepgsql_set_client_label(const char *new_label)
 		tcontext = client_label_peer;
 	else
 	{
-		if (security_check_context_raw((security_context_t) new_label) < 0)
+		if (security_check_context_raw(new_label) < 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_NAME),
 					 errmsg("SELinux: invalid security label: \"%s\"",
@@ -462,9 +462,9 @@ sepgsql_get_label(Oid classId, Oid objectId, int32 subId)
 	object.objectSubId = subId;
 
 	label = GetSecurityLabel(&object, SEPGSQL_LABEL_TAG);
-	if (!label || security_check_context_raw((security_context_t) label))
+	if (!label || security_check_context_raw(label))
 	{
-		security_context_t unlabeled;
+		char	   *unlabeled;
 
 		if (security_get_initial_context_raw("unlabeled", &unlabeled) < 0)
 			ereport(ERROR,
@@ -499,7 +499,7 @@ sepgsql_object_relabel(const ObjectAddress *object, const char *seclabel)
 	 * context of selinux.
 	 */
 	if (seclabel &&
-		security_check_context_raw((security_context_t) seclabel) < 0)
+		security_check_context_raw(seclabel) < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_NAME),
 				 errmsg("SELinux: invalid security label: \"%s\"", seclabel)));
@@ -741,7 +741,7 @@ exec_object_restorecon(struct selabel_handle *sehnd, Oid catalogId)
 		char	   *objname;
 		int			objtype = 1234;
 		ObjectAddress object;
-		security_context_t context;
+		char	   *context;
 
 		/*
 		 * The way to determine object name depends on object classes. So, any

contrib/sepgsql/selinux.c

@@ -767,8 +767,8 @@ sepgsql_compute_avd(const char *scontext,
 	 * Ask SELinux what is allowed set of permissions on a pair of the
 	 * security contexts and the given object class.
 	 */
-	if (security_compute_av_flags_raw((security_context_t) scontext,
-									  (security_context_t) tcontext,
+	if (security_compute_av_flags_raw(scontext,
+									  tcontext,
 									  tclass_ex, 0, &avd_ex) < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INTERNAL_ERROR),
@@ -839,7 +839,7 @@ sepgsql_compute_create(const char *scontext,
 					   uint16 tclass,
 					   const char *objname)
 {
-	security_context_t ncontext;
+	char	   *ncontext;
 	security_class_t tclass_ex;
 	const char *tclass_name;
 	char	   *result;
@@ -854,8 +854,8 @@ sepgsql_compute_create(const char *scontext,
 	 * Ask SELinux what is the default context for the given object class on a
 	 * pair of security contexts
 	 */
-	if (security_compute_create_name_raw((security_context_t) scontext,
-										 (security_context_t) tcontext,
+	if (security_compute_create_name_raw(scontext,
+										 tcontext,
 										 tclass_ex,
 										 objname,
 										 &ncontext) < 0)

contrib/sepgsql/uavc.c

@@ -177,7 +177,7 @@ sepgsql_avc_unlabeled(void)
 {
 	if (!avc_unlabeled)
 	{
-		security_context_t unlabeled;
+		char	   *unlabeled;
 
 		if (security_get_initial_context_raw("unlabeled", &unlabeled) < 0)
 			ereport(ERROR,
@@ -225,7 +225,7 @@ sepgsql_avc_compute(const char *scontext, const char *tcontext, uint16 tclass)
 	 * policy is reloaded, validation status shall be kept, so we also cache
 	 * whether the supplied security context was valid, or not.
 	 */
-	if (security_check_context_raw((security_context_t) tcontext) != 0)
+	if (security_check_context_raw(tcontext) != 0)
 		ucontext = sepgsql_avc_unlabeled();
 
 	/*