/* -------------------------------------------------------------------------
 *
 * seclabel.c
 *    routines to support security label feature.
 *
 * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * -------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_seclabel.h"
#include "commands/seclabel.h"
#include "miscadmin.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/tqual.h"

/*
 * For most object types, the permissions-checking logic is simple enough
 * that it makes sense to just include it in CommentObject().  However,
 * attributes require a bit more checking.
 */
static void CheckAttributeSecLabel(Relation relation);

typedef struct
{
	const char *provider_name;
	check_object_relabel_type	hook;
} LabelProvider;

static List *label_provider_list = NIL;

/*
 * ExecSecLabelStmt --
 *
 * Apply a security label to a database object.
 */
void
ExecSecLabelStmt(SecLabelStmt *stmt)
{
	LabelProvider *provider = NULL;
	ObjectAddress	address;
	Relation		relation;
	ListCell	   *lc;

	/*
	 * Find the named label provider, or if none specified, check whether
	 * there's exactly one, and if so use it.
	 */
	if (stmt->provider == NULL)
	{
		if (label_provider_list == NIL)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("no security label providers have been loaded")));
		if (lnext(list_head(label_provider_list)) != NULL)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("must specify provider when multiple security label providers have been loaded")));
		provider = (LabelProvider *) linitial(label_provider_list);
	}
	else
	{
		foreach (lc, label_provider_list)
		{
			LabelProvider *lp = lfirst(lc);

			if (strcmp(stmt->provider, lp->provider_name) == 0)
			{
				provider = lp;
				break;
			}
		}
		if (provider == NULL)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
					 errmsg("security label provider \"%s\" is not loaded",
							stmt->provider)));
	}

	/*
	 * Translate the parser representation which identifies this object
	 * into an ObjectAddress. get_object_address() will throw an error if
     * the object does not exist, and will also acquire a lock on the
     * target to guard against concurrent modifications.
	 */
	address = get_object_address(stmt->objtype, stmt->objname, stmt->objargs,
								 &relation, ShareUpdateExclusiveLock);

	/* Privilege and integrity checks. */
	switch (stmt->objtype)
	{
		case OBJECT_SEQUENCE:
		case OBJECT_TABLE:
		case OBJECT_VIEW:
			if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
							   RelationGetRelationName(relation));
			break;
		case OBJECT_COLUMN:
			CheckAttributeSecLabel(relation);
			break;
		case OBJECT_TYPE:
			if (!pg_type_ownercheck(address.objectId, GetUserId()))
				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_TYPE,
							   format_type_be(address.objectId));
			break;
		case OBJECT_AGGREGATE:
		case OBJECT_FUNCTION:
			if (!pg_proc_ownercheck(address.objectId, GetUserId()))
				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_PROC,
							   NameListToString(stmt->objname));
			break;
		case OBJECT_SCHEMA:
			if (!pg_namespace_ownercheck(address.objectId, GetUserId()))
				aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_NAMESPACE,
							   strVal(linitial(stmt->objname)));
			break;
		case OBJECT_LANGUAGE:
			if (!superuser())
				ereport(ERROR,
						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
					 errmsg("must be superuser to comment on procedural language")));
			break;
		case OBJECT_LARGEOBJECT:
			if (!pg_largeobject_ownercheck(address.objectId, GetUserId()))
				ereport(ERROR,
						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
						 errmsg("must be owner of large object %u",
							address.objectId)));
			break;
		default:
			elog(ERROR, "unrecognized object type: %d",
				 (int) stmt->objtype);
	}

	/* Provider gets control here, may throw ERROR to veto new label. */
	(*provider->hook)(&address, stmt->label);

	/* Apply new label. */
	SetSecurityLabel(&address, provider->provider_name, stmt->label);

	/*
	 * If get_object_address() opened the relation for us, we close it to keep
	 * the reference count correct - but we retain any locks acquired by
	 * get_object_address() until commit time, to guard against concurrent
	 * activity.
	 */
	if (relation != NULL)
		relation_close(relation, NoLock);
}

/*
 * GetSecurityLabel returns the security label for a database object for a
 * given provider, or NULL if there is no such label.
 */
char *
GetSecurityLabel(const ObjectAddress *object, const char *provider)
{
	Relation	pg_seclabel;
	ScanKeyData	keys[4];
	SysScanDesc	scan;
	HeapTuple	tuple;
	Datum		datum;
	bool		isnull;
	char	   *seclabel = NULL;

	Assert(!IsSharedRelation(object->classId));

	ScanKeyInit(&keys[0],
				Anum_pg_seclabel_objoid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(object->objectId));
	ScanKeyInit(&keys[1],
				Anum_pg_seclabel_classoid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(object->classId));
	ScanKeyInit(&keys[2],
				Anum_pg_seclabel_objsubid,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum(object->objectSubId));
	ScanKeyInit(&keys[3],
				Anum_pg_seclabel_provider,
				BTEqualStrategyNumber, F_TEXTEQ,
				CStringGetTextDatum(provider));

	pg_seclabel = heap_open(SecLabelRelationId, AccessShareLock);

	scan = systable_beginscan(pg_seclabel, SecLabelObjectIndexId, true,
							  SnapshotNow, 4, keys);

	tuple = systable_getnext(scan);
	if (HeapTupleIsValid(tuple))
	{
		datum = heap_getattr(tuple, Anum_pg_seclabel_label,
							 RelationGetDescr(pg_seclabel), &isnull);
		if (!isnull)
			seclabel = TextDatumGetCString(datum);
	}
	systable_endscan(scan);

	heap_close(pg_seclabel, AccessShareLock);

	return seclabel;
}

/*
 * SetSecurityLabel attempts to set the security label for the specified
 * provider on the specified object to the given value.  NULL means that any
 * any existing label should be deleted.
 */
void
SetSecurityLabel(const ObjectAddress *object,
				 const char *provider, const char *label)
{
	Relation	pg_seclabel;
	ScanKeyData	keys[4];
	SysScanDesc	scan;
	HeapTuple	oldtup;
	HeapTuple	newtup = NULL;
	Datum		values[Natts_pg_seclabel];
	bool		nulls[Natts_pg_seclabel];
	bool		replaces[Natts_pg_seclabel];

	/* Security labels on shared objects are not supported. */
	Assert(!IsSharedRelation(object->classId));

	/* Prepare to form or update a tuple, if necessary. */
	memset(nulls, false, sizeof(nulls));
	memset(replaces, false, sizeof(replaces));
	values[Anum_pg_seclabel_objoid - 1] = ObjectIdGetDatum(object->objectId);
	values[Anum_pg_seclabel_classoid - 1] = ObjectIdGetDatum(object->classId);
	values[Anum_pg_seclabel_objsubid - 1] = Int32GetDatum(object->objectSubId);
	values[Anum_pg_seclabel_provider - 1] = CStringGetTextDatum(provider);
	if (label != NULL)
		values[Anum_pg_seclabel_label - 1] = CStringGetTextDatum(label);

	/* Use the index to search for a matching old tuple */
	ScanKeyInit(&keys[0],
				Anum_pg_seclabel_objoid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(object->objectId));
	ScanKeyInit(&keys[1],
				Anum_pg_seclabel_classoid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(object->classId));
	ScanKeyInit(&keys[2],
				Anum_pg_seclabel_objsubid,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum(object->objectSubId));
	ScanKeyInit(&keys[3],
				Anum_pg_seclabel_provider,
				BTEqualStrategyNumber, F_TEXTEQ,
				CStringGetTextDatum(provider));

	pg_seclabel = heap_open(SecLabelRelationId, RowExclusiveLock);

	scan = systable_beginscan(pg_seclabel, SecLabelObjectIndexId, true,
							  SnapshotNow, 4, keys);

	oldtup = systable_getnext(scan);
	if (HeapTupleIsValid(oldtup))
	{
		if (label == NULL)
			simple_heap_delete(pg_seclabel, &oldtup->t_self);
		else
		{
			replaces[Anum_pg_seclabel_label - 1] = true;
			newtup = heap_modify_tuple(oldtup, RelationGetDescr(pg_seclabel),
									   values, nulls, replaces);
			simple_heap_update(pg_seclabel, &oldtup->t_self, newtup);
		}
	}
	systable_endscan(scan);

	/* If we didn't find an old tuple, insert a new one */
	if (newtup == NULL && label != NULL)
	{
		newtup = heap_form_tuple(RelationGetDescr(pg_seclabel),
								 values, nulls);
		simple_heap_insert(pg_seclabel, newtup);
	}

	/* Update indexes, if necessary */
	if (newtup != NULL)
	{
		CatalogUpdateIndexes(pg_seclabel, newtup);
		heap_freetuple(newtup);
	}

	heap_close(pg_seclabel, RowExclusiveLock);
}

/*
 * DeleteSecurityLabel removes all security labels for an object (and any
 * sub-objects, if applicable).
 */
void
DeleteSecurityLabel(const ObjectAddress *object)
{
	Relation	pg_seclabel;
	ScanKeyData	skey[3];
	SysScanDesc	scan;
	HeapTuple	oldtup;
	int			nkeys;

	/* Security labels on shared objects are not supported. */
	if (IsSharedRelation(object->classId))
		return;

	ScanKeyInit(&skey[0],
				Anum_pg_seclabel_objoid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(object->objectId));
	ScanKeyInit(&skey[1],
				Anum_pg_seclabel_classoid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(object->classId));
	if (object->objectSubId != 0)
	{
		ScanKeyInit(&skey[2],
					Anum_pg_seclabel_objsubid,
					BTEqualStrategyNumber, F_INT4EQ,
					Int32GetDatum(object->objectSubId));
		nkeys = 3;
	}
	else
		nkeys = 2;

	pg_seclabel = heap_open(SecLabelRelationId, RowExclusiveLock);

	scan = systable_beginscan(pg_seclabel, SecLabelObjectIndexId, true,
							  SnapshotNow, nkeys, skey);
	while (HeapTupleIsValid(oldtup = systable_getnext(scan)))
		simple_heap_delete(pg_seclabel, &oldtup->t_self);
	systable_endscan(scan);

	heap_close(pg_seclabel, RowExclusiveLock);
}

/*
 * Check whether the user is allowed to comment on an attribute of the
 * specified relation.
 */
static void
CheckAttributeSecLabel(Relation relation)
{
	if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
					   RelationGetRelationName(relation));

	/*
	 * Allow security labels only on columns of tables, views, and composite
	 * types (which are the only relkinds for which pg_dump will dump labels).
	 */
	if (relation->rd_rel->relkind != RELKIND_RELATION &&
		relation->rd_rel->relkind != RELKIND_VIEW &&
		relation->rd_rel->relkind != RELKIND_COMPOSITE_TYPE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a table, view, or composite type",
						RelationGetRelationName(relation))));
}

void
register_label_provider(const char *provider_name, check_object_relabel_type hook)
{
	LabelProvider  *provider;
	MemoryContext	oldcxt;

	oldcxt = MemoryContextSwitchTo(TopMemoryContext);
	provider = palloc(sizeof(LabelProvider));
	provider->provider_name = pstrdup(provider_name);
	provider->hook = hook;
	label_provider_list = lappend(label_provider_list, provider);
	MemoryContextSwitchTo(oldcxt);
}