/*-------------------------------------------------------------------------
 *
 * aclchk.c
 *	  Routines to check access control permissions.
 *
 * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/catalog/aclchk.c,v 1.66 2002/04/21 00:26:42 tgl Exp $
 *
 * NOTES
 *	  See acl.h.
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "catalog/catalog.h"
#include "catalog/catname.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_database.h"
#include "catalog/pg_group.h"
#include "catalog/pg_language.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_shadow.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "parser/parse_func.h"
#include "utils/acl.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


static void ExecuteGrantStmt_Relation(GrantStmt *stmt);
static void ExecuteGrantStmt_Database(GrantStmt *stmt);
static void ExecuteGrantStmt_Function(GrantStmt *stmt);
static void ExecuteGrantStmt_Language(GrantStmt *stmt);
static void ExecuteGrantStmt_Namespace(GrantStmt *stmt);

static const char *privilege_to_string(AclMode privilege);

static int32 aclcheck(Acl *acl, AclId id, uint32 idtype, AclMode mode);

/* warning messages, now more explicit. */
/* MUST correspond to the order of the ACLCHECK_* result codes in acl.h. */
const char * const aclcheck_error_strings[] = {
	"No error.",
	"Permission denied.",
	"Table does not exist.",
	"Must be table owner."
};


#ifdef ACLDEBUG
static
dumpacl(Acl *acl)
{
	int			i;
	AclItem    *aip;

	elog(DEBUG1, "acl size = %d, # acls = %d",
		 ACL_SIZE(acl), ACL_NUM(acl));
	aip = ACL_DAT(acl);
	for (i = 0; i < ACL_NUM(acl); ++i)
		elog(DEBUG1, "	acl[%d]: %s", i,
			 DatumGetCString(DirectFunctionCall1(aclitemout,
											 PointerGetDatum(aip + i))));
}
#endif   /* ACLDEBUG */


/*
 * If is_grant is true, adds the given privileges for the list of
 * grantees to the existing old_acl.  If is_grant is false, the
 * privileges for the given grantees are removed from old_acl.
 */
static Acl *
merge_acl_with_grant(Acl *old_acl, bool is_grant,
					 List *grantees, AclMode privileges)
{
	unsigned	modechg;
	List	   *j;
	Acl		   *new_acl;

	modechg = is_grant ? ACL_MODECHG_ADD : ACL_MODECHG_DEL;

#ifdef ACLDEBUG
	dumpacl(old_acl);
#endif
	new_acl = old_acl;

	foreach(j, grantees)
	{
		PrivGrantee *grantee = (PrivGrantee *) lfirst(j);
		AclItem		aclitem;
		uint32		idtype;

		if (grantee->username)
		{
			aclitem.ai_id = get_usesysid(grantee->username);
			idtype = ACL_IDTYPE_UID;
		}
		else if (grantee->groupname)
		{
			aclitem.ai_id = get_grosysid(grantee->groupname);
			idtype = ACL_IDTYPE_GID;
		}
		else
		{
			aclitem.ai_id = ACL_ID_WORLD;
			idtype = ACL_IDTYPE_WORLD;
		}

		ACLITEM_SET_PRIVS_IDTYPE(aclitem, privileges, idtype);

		new_acl = aclinsert3(new_acl, &aclitem, modechg);

#ifdef ACLDEBUG
		dumpacl(new_acl);
#endif
	}

	return new_acl;
}


/*
 * Called to execute the utility commands GRANT and REVOKE
 */
void
ExecuteGrantStmt(GrantStmt *stmt)
{
	switch (stmt->objtype)
	{
		case ACL_OBJECT_RELATION:
			ExecuteGrantStmt_Relation(stmt);
			break;
		case ACL_OBJECT_DATABASE:
			ExecuteGrantStmt_Database(stmt);
			break;
		case ACL_OBJECT_FUNCTION:
			ExecuteGrantStmt_Function(stmt);
			break;
		case ACL_OBJECT_LANGUAGE:
			ExecuteGrantStmt_Language(stmt);
			break;
		case ACL_OBJECT_NAMESPACE:
			ExecuteGrantStmt_Namespace(stmt);
			break;
		default:
			elog(ERROR, "bogus GrantStmt.objtype %d", (int) stmt->objtype);
	}
}

static void
ExecuteGrantStmt_Relation(GrantStmt *stmt)
{
	AclMode		privileges;
	List	   *i;

	if (lfirsti(stmt->privileges) == ACL_ALL_RIGHTS)
		privileges = ACL_ALL_RIGHTS_RELATION;
	else
	{
		privileges = ACL_NO_RIGHTS;
		foreach(i, stmt->privileges)
		{
			AclMode		priv = lfirsti(i);

			if (priv & ~((AclMode) ACL_ALL_RIGHTS_RELATION))
				elog(ERROR, "invalid privilege type %s for table object",
					 privilege_to_string(priv));
			privileges |= priv;
		}
	}

	foreach(i, stmt->objects)
	{
		RangeVar   *relvar = (RangeVar *) lfirst(i);
		Oid			relOid;
		Relation	relation;
		HeapTuple	tuple;
		Form_pg_class pg_class_tuple;
		Datum		aclDatum;
		bool		isNull;
		Acl		   *old_acl;
		Acl		   *new_acl;
		HeapTuple	newtuple;
		Datum		values[Natts_pg_class];
		char		nulls[Natts_pg_class];
		char		replaces[Natts_pg_class];

		/* open pg_class */
		relation = heap_openr(RelationRelationName, RowExclusiveLock);
		relOid = RangeVarGetRelid(relvar, false);
		tuple = SearchSysCache(RELOID,
							   ObjectIdGetDatum(relOid),
							   0, 0, 0);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "relation %u not found", relOid);
		pg_class_tuple = (Form_pg_class) GETSTRUCT(tuple);

		if (!pg_class_ownercheck(relOid, GetUserId()))
			elog(ERROR, "%s: permission denied",
				 relvar->relname);

		if (pg_class_tuple->relkind == RELKIND_INDEX)
			elog(ERROR, "\"%s\" is an index",
				 relvar->relname);

		/*
		 * If there's no ACL, create a default using the pg_class.relowner
		 * field.
		 */
		aclDatum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_relacl,
								   &isNull);
		if (isNull)
			old_acl = acldefault(ACL_OBJECT_RELATION,
								 pg_class_tuple->relowner);
		else
			/* get a detoasted copy of the ACL */
			old_acl = DatumGetAclPCopy(aclDatum);

		new_acl = merge_acl_with_grant(old_acl, stmt->is_grant,
									   stmt->grantees, privileges);

		/* finished building new ACL value, now insert it */
		MemSet(values, 0, sizeof(values));
		MemSet(nulls, ' ', sizeof(nulls));
		MemSet(replaces, ' ', sizeof(replaces));

		replaces[Anum_pg_class_relacl - 1] = 'r';
		values[Anum_pg_class_relacl - 1] = PointerGetDatum(new_acl);

		newtuple = heap_modifytuple(tuple, relation, values, nulls, replaces);

		ReleaseSysCache(tuple);

		simple_heap_update(relation, &newtuple->t_self, newtuple);

		{
			/* keep the catalog indexes up to date */
			Relation	idescs[Num_pg_class_indices];

			CatalogOpenIndices(Num_pg_class_indices, Name_pg_class_indices,
							   idescs);
			CatalogIndexInsert(idescs, Num_pg_class_indices, relation, newtuple);
			CatalogCloseIndices(Num_pg_class_indices, idescs);
		}

		pfree(old_acl);
		pfree(new_acl);

		heap_close(relation, RowExclusiveLock);
	}
}

static void
ExecuteGrantStmt_Database(GrantStmt *stmt)
{
	AclMode		privileges;
	List	   *i;

	if (lfirsti(stmt->privileges) == ACL_ALL_RIGHTS)
		privileges = ACL_ALL_RIGHTS_DATABASE;
	else
	{
		privileges = ACL_NO_RIGHTS;
		foreach(i, stmt->privileges)
		{
			AclMode		priv = lfirsti(i);

			if (priv & ~((AclMode) ACL_ALL_RIGHTS_DATABASE))
				elog(ERROR, "invalid privilege type %s for database object",
					 privilege_to_string(priv));
			privileges |= priv;
		}
	}

	foreach(i, stmt->objects)
	{
		char	   *dbname = strVal(lfirst(i));
		Relation	relation;
		ScanKeyData entry[1];
		HeapScanDesc scan;
		HeapTuple	tuple;
		Form_pg_database pg_database_tuple;
		Datum		aclDatum;
		bool		isNull;
		Acl		   *old_acl;
		Acl		   *new_acl;
		HeapTuple	newtuple;
		Datum		values[Natts_pg_database];
		char		nulls[Natts_pg_database];
		char		replaces[Natts_pg_database];

		relation = heap_openr(DatabaseRelationName, RowExclusiveLock);
		ScanKeyEntryInitialize(&entry[0], 0,
							   Anum_pg_database_datname, F_NAMEEQ,
							   CStringGetDatum(dbname));
		scan = heap_beginscan(relation, 0, SnapshotNow, 1, entry);
		tuple = heap_getnext(scan, 0);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "database \"%s\" not found", dbname);
		pg_database_tuple = (Form_pg_database) GETSTRUCT(tuple);

		if (!superuser() && pg_database_tuple->datdba != GetUserId())
			elog(ERROR, "permission denied");

		/*
		 * If there's no ACL, create a default.
		 */
		aclDatum = heap_getattr(tuple, Anum_pg_database_datacl,
								RelationGetDescr(relation), &isNull);
		if (isNull)
			old_acl = acldefault(ACL_OBJECT_DATABASE,
								 pg_database_tuple->datdba);
		else
			/* get a detoasted copy of the ACL */
			old_acl = DatumGetAclPCopy(aclDatum);

		new_acl = merge_acl_with_grant(old_acl, stmt->is_grant,
									   stmt->grantees, privileges);

		/* finished building new ACL value, now insert it */
		MemSet(values, 0, sizeof(values));
		MemSet(nulls, ' ', sizeof(nulls));
		MemSet(replaces, ' ', sizeof(replaces));

		replaces[Anum_pg_database_datacl - 1] = 'r';
		values[Anum_pg_database_datacl - 1] = PointerGetDatum(new_acl);

		newtuple = heap_modifytuple(tuple, relation, values, nulls, replaces);

		simple_heap_update(relation, &newtuple->t_self, newtuple);

		{
			/* keep the catalog indexes up to date */
			Relation	idescs[Num_pg_database_indices];

			CatalogOpenIndices(Num_pg_database_indices, Name_pg_database_indices,
							   idescs);
			CatalogIndexInsert(idescs, Num_pg_database_indices, relation, newtuple);
			CatalogCloseIndices(Num_pg_database_indices, idescs);
		}

		pfree(old_acl);
		pfree(new_acl);

		heap_endscan(scan);

		heap_close(relation, RowExclusiveLock);
	}
}

static void
ExecuteGrantStmt_Function(GrantStmt *stmt)
{
	AclMode		privileges;
	List	   *i;

	if (lfirsti(stmt->privileges) == ACL_ALL_RIGHTS)
		privileges = ACL_ALL_RIGHTS_FUNCTION;
	else
	{
		privileges = ACL_NO_RIGHTS;
		foreach(i, stmt->privileges)
		{
			AclMode		priv = lfirsti(i);

			if (priv & ~((AclMode) ACL_ALL_RIGHTS_FUNCTION))
				elog(ERROR, "invalid privilege type %s for function object",
					 privilege_to_string(priv));
			privileges |= priv;
		}
	}

	foreach(i, stmt->objects)
	{
		FuncWithArgs *func = (FuncWithArgs *) lfirst(i);
		Oid			oid;
		Relation	relation;
		HeapTuple	tuple;
		Form_pg_proc pg_proc_tuple;
		Datum		aclDatum;
		bool		isNull;
		Acl		   *old_acl;
		Acl		   *new_acl;
		HeapTuple	newtuple;
		Datum		values[Natts_pg_proc];
		char		nulls[Natts_pg_proc];
		char		replaces[Natts_pg_proc];

		oid = LookupFuncNameTypeNames(func->funcname, func->funcargs,
									  true, "GRANT");
		relation = heap_openr(ProcedureRelationName, RowExclusiveLock);
		tuple = SearchSysCache(PROCOID,
							   ObjectIdGetDatum(oid),
							   0, 0, 0);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "function %u not found", oid);
		pg_proc_tuple = (Form_pg_proc) GETSTRUCT(tuple);

		if (!pg_proc_ownercheck(oid, GetUserId()))
			elog(ERROR, "permission denied");

		/*
		 * If there's no ACL, create a default using the pg_proc.proowner
		 * field.
		 */
		aclDatum = SysCacheGetAttr(PROCOID, tuple, Anum_pg_proc_proacl,
								   &isNull);
		if (isNull)
			old_acl = acldefault(ACL_OBJECT_FUNCTION,
								 pg_proc_tuple->proowner);
		else
			/* get a detoasted copy of the ACL */
			old_acl = DatumGetAclPCopy(aclDatum);

		new_acl = merge_acl_with_grant(old_acl, stmt->is_grant,
									   stmt->grantees, privileges);

		/* finished building new ACL value, now insert it */
		MemSet(values, 0, sizeof(values));
		MemSet(nulls, ' ', sizeof(nulls));
		MemSet(replaces, ' ', sizeof(replaces));

		replaces[Anum_pg_proc_proacl - 1] = 'r';
		values[Anum_pg_proc_proacl - 1] = PointerGetDatum(new_acl);

		newtuple = heap_modifytuple(tuple, relation, values, nulls, replaces);

		ReleaseSysCache(tuple);

		simple_heap_update(relation, &newtuple->t_self, newtuple);

		{
			/* keep the catalog indexes up to date */
			Relation	idescs[Num_pg_proc_indices];

			CatalogOpenIndices(Num_pg_proc_indices, Name_pg_proc_indices,
							   idescs);
			CatalogIndexInsert(idescs, Num_pg_proc_indices, relation, newtuple);
			CatalogCloseIndices(Num_pg_proc_indices, idescs);
		}

		pfree(old_acl);
		pfree(new_acl);

		heap_close(relation, RowExclusiveLock);
	}
}

static void
ExecuteGrantStmt_Language(GrantStmt *stmt)
{
	AclMode		privileges;
	List	   *i;

	if (lfirsti(stmt->privileges) == ACL_ALL_RIGHTS)
		privileges = ACL_ALL_RIGHTS_LANGUAGE;
	else
	{
		privileges = ACL_NO_RIGHTS;
		foreach(i, stmt->privileges)
		{
			AclMode		priv = lfirsti(i);

			if (priv & ~((AclMode) ACL_ALL_RIGHTS_LANGUAGE))
				elog(ERROR, "invalid privilege type %s for language object",
					 privilege_to_string(priv));
			privileges |= priv;
		}
	}

	foreach(i, stmt->objects)
	{
		char	   *langname = strVal(lfirst(i));
		Relation	relation;
		HeapTuple	tuple;
		Form_pg_language pg_language_tuple;
		Datum		aclDatum;
		bool		isNull;
		Acl		   *old_acl;
		Acl		   *new_acl;
		HeapTuple	newtuple;
		Datum		values[Natts_pg_language];
		char		nulls[Natts_pg_language];
		char		replaces[Natts_pg_language];

		if (!superuser())
			elog(ERROR, "permission denied");

		relation = heap_openr(LanguageRelationName, RowExclusiveLock);
		tuple = SearchSysCache(LANGNAME,
							   PointerGetDatum(langname),
							   0, 0, 0);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "language \"%s\" not found", langname);
		pg_language_tuple = (Form_pg_language) GETSTRUCT(tuple);

		if (!pg_language_tuple->lanpltrusted)
			elog(ERROR, "language \"%s\" is not trusted", langname);

		/*
		 * If there's no ACL, create a default.
		 */
		aclDatum = SysCacheGetAttr(LANGNAME, tuple, Anum_pg_language_lanacl,
								   &isNull);
		if (isNull)
			old_acl = acldefault(ACL_OBJECT_LANGUAGE,
								 InvalidOid);
		else
			/* get a detoasted copy of the ACL */
			old_acl = DatumGetAclPCopy(aclDatum);

		new_acl = merge_acl_with_grant(old_acl, stmt->is_grant,
									   stmt->grantees, privileges);

		/* finished building new ACL value, now insert it */
		MemSet(values, 0, sizeof(values));
		MemSet(nulls, ' ', sizeof(nulls));
		MemSet(replaces, ' ', sizeof(replaces));

		replaces[Anum_pg_language_lanacl - 1] = 'r';
		values[Anum_pg_language_lanacl - 1] = PointerGetDatum(new_acl);

		newtuple = heap_modifytuple(tuple, relation, values, nulls, replaces);

		ReleaseSysCache(tuple);

		simple_heap_update(relation, &newtuple->t_self, newtuple);

		{
			/* keep the catalog indexes up to date */
			Relation	idescs[Num_pg_language_indices];

			CatalogOpenIndices(Num_pg_language_indices, Name_pg_language_indices,
							   idescs);
			CatalogIndexInsert(idescs, Num_pg_language_indices, relation, newtuple);
			CatalogCloseIndices(Num_pg_language_indices, idescs);
		}

		pfree(old_acl);
		pfree(new_acl);

		heap_close(relation, RowExclusiveLock);
	}
}

static void
ExecuteGrantStmt_Namespace(GrantStmt *stmt)
{
	AclMode		privileges;
	List	   *i;

	if (lfirsti(stmt->privileges) == ACL_ALL_RIGHTS)
		privileges = ACL_ALL_RIGHTS_NAMESPACE;
	else
	{
		privileges = ACL_NO_RIGHTS;
		foreach(i, stmt->privileges)
		{
			AclMode		priv = lfirsti(i);

			if (priv & ~((AclMode) ACL_ALL_RIGHTS_NAMESPACE))
				elog(ERROR, "invalid privilege type %s for namespace object",
					 privilege_to_string(priv));
			privileges |= priv;
		}
	}

	foreach(i, stmt->objects)
	{
		char	   *nspname = strVal(lfirst(i));
		Relation	relation;
		HeapTuple	tuple;
		Form_pg_namespace pg_namespace_tuple;
		Datum		aclDatum;
		bool		isNull;
		Acl		   *old_acl;
		Acl		   *new_acl;
		HeapTuple	newtuple;
		Datum		values[Natts_pg_namespace];
		char		nulls[Natts_pg_namespace];
		char		replaces[Natts_pg_namespace];

		relation = heap_openr(NamespaceRelationName, RowExclusiveLock);
		tuple = SearchSysCache(NAMESPACENAME,
							   CStringGetDatum(nspname),
							   0, 0, 0);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "namespace \"%s\" not found", nspname);
		pg_namespace_tuple = (Form_pg_namespace) GETSTRUCT(tuple);

		if (!pg_namespace_ownercheck(tuple->t_data->t_oid, GetUserId()))
			elog(ERROR, "permission denied");

		/*
		 * If there's no ACL, create a default using the pg_namespace.nspowner
		 * field.
		 */
		aclDatum = SysCacheGetAttr(NAMESPACENAME, tuple,
								   Anum_pg_namespace_nspacl,
								   &isNull);
		if (isNull)
			old_acl = acldefault(ACL_OBJECT_NAMESPACE,
								 pg_namespace_tuple->nspowner);
		else
			/* get a detoasted copy of the ACL */
			old_acl = DatumGetAclPCopy(aclDatum);

		new_acl = merge_acl_with_grant(old_acl, stmt->is_grant,
									   stmt->grantees, privileges);

		/* finished building new ACL value, now insert it */
		MemSet(values, 0, sizeof(values));
		MemSet(nulls, ' ', sizeof(nulls));
		MemSet(replaces, ' ', sizeof(replaces));

		replaces[Anum_pg_namespace_nspacl - 1] = 'r';
		values[Anum_pg_namespace_nspacl - 1] = PointerGetDatum(new_acl);

		newtuple = heap_modifytuple(tuple, relation, values, nulls, replaces);

		ReleaseSysCache(tuple);

		simple_heap_update(relation, &newtuple->t_self, newtuple);

		{
			/* keep the catalog indexes up to date */
			Relation	idescs[Num_pg_namespace_indices];

			CatalogOpenIndices(Num_pg_namespace_indices, Name_pg_namespace_indices,
							   idescs);
			CatalogIndexInsert(idescs, Num_pg_namespace_indices, relation, newtuple);
			CatalogCloseIndices(Num_pg_namespace_indices, idescs);
		}

		pfree(old_acl);
		pfree(new_acl);

		heap_close(relation, RowExclusiveLock);
	}
}


static const char *
privilege_to_string(AclMode privilege)
{
	switch (privilege)
	{
		case ACL_INSERT:
			return "INSERT";
		case ACL_SELECT:
			return "SELECT";
		case ACL_UPDATE:
			return "UPDATE";
		case ACL_DELETE:
			return "DELETE";
		case ACL_RULE:
			return "RULE";
		case ACL_REFERENCES:
			return "REFERENCES";
		case ACL_TRIGGER:
			return "TRIGGER";
		case ACL_EXECUTE:
			return "EXECUTE";
		case ACL_USAGE:
			return "USAGE";
		case ACL_CREATE:
			return "CREATE";
		case ACL_CREATE_TEMP:
			return "TEMP";
		default:
			elog(ERROR, "privilege_to_string: unrecognized privilege %d",
				 privilege);
	}
	return NULL;				/* appease compiler */
}


AclId
get_grosysid(char *groname)
{
	HeapTuple	tuple;
	AclId		id = 0;

	tuple = SearchSysCache(GRONAME,
						   PointerGetDatum(groname),
						   0, 0, 0);
	if (HeapTupleIsValid(tuple))
	{
		id = ((Form_pg_group) GETSTRUCT(tuple))->grosysid;
		ReleaseSysCache(tuple);
	}
	else
		elog(ERROR, "non-existent group \"%s\"", groname);
	return id;
}

/*
 * Convert group ID to name, or return NULL if group can't be found
 */
char *
get_groname(AclId grosysid)
{
	HeapTuple	tuple;
	char	   *name = NULL;

	tuple = SearchSysCache(GROSYSID,
						   ObjectIdGetDatum(grosysid),
						   0, 0, 0);
	if (HeapTupleIsValid(tuple))
	{
		name = pstrdup(NameStr(((Form_pg_group) GETSTRUCT(tuple))->groname));
		ReleaseSysCache(tuple);
	}
	return name;
}

/*
 * Is user a member of group?
 */
static bool
in_group(AclId uid, AclId gid)
{
	bool		result = false;
	HeapTuple	tuple;
	Datum		att;
	bool		isNull;
	IdList	   *glist;
	AclId	   *aidp;
	int			i,
				num;

	tuple = SearchSysCache(GROSYSID,
						   ObjectIdGetDatum(gid),
						   0, 0, 0);
	if (HeapTupleIsValid(tuple))
	{
		att = SysCacheGetAttr(GROSYSID,
							  tuple,
							  Anum_pg_group_grolist,
							  &isNull);
		if (!isNull)
		{
			/* be sure the IdList is not toasted */
			glist = DatumGetIdListP(att);
			/* scan it */
			num = IDLIST_NUM(glist);
			aidp = IDLIST_DAT(glist);
			for (i = 0; i < num; ++i)
			{
				if (aidp[i] == uid)
				{
					result = true;
					break;
				}
			}
			/* if IdList was toasted, free detoasted copy */
			if ((Pointer) glist != DatumGetPointer(att))
				pfree(glist);
		}
		ReleaseSysCache(tuple);
	}
	else
		elog(WARNING, "in_group: group %u not found", gid);
	return result;
}

/*
 * aclcheck
 *
 * Returns ACLCHECK_OK if the 'id' of type 'idtype' has ACL entries in 'acl'
 * to satisfy any one of the requirements of 'mode'.  Returns an appropriate
 * ACLCHECK_* error code otherwise.
 *
 * The ACL list is expected to be sorted in standard order.
 */
static int32
aclcheck(Acl *acl, AclId id, uint32 idtype, AclMode mode)
{
	AclItem    *aip,
			   *aidat;
	int			i,
				num;

	/*
	 * If ACL is null, default to "OK" --- this should not happen, since
	 * caller should have inserted appropriate default
	 */
	if (!acl)
	{
		elog(DEBUG1, "aclcheck: null ACL, returning OK");
		return ACLCHECK_OK;
	}

	num = ACL_NUM(acl);
	aidat = ACL_DAT(acl);

	/*
	 * We'll treat the empty ACL like that, too, although this is more
	 * like an error (i.e., you manually blew away your ACL array) -- the
	 * system never creates an empty ACL, since there must always be a
	 * "world" entry in the first slot.
	 */
	if (num < 1)
	{
		elog(DEBUG1, "aclcheck: zero-length ACL, returning OK");
		return ACLCHECK_OK;
	}

	/*
	 * "World" rights are applicable regardless of the passed-in ID, and
	 * since they're much the cheapest to check, check 'em first.
	 */
	if (ACLITEM_GET_IDTYPE(*aidat) != ACL_IDTYPE_WORLD)
		elog(ERROR, "aclcheck: first entry in ACL is not 'world' entry");
	if (aidat->ai_privs & mode)
	{
#ifdef ACLDEBUG
		elog(DEBUG1, "aclcheck: using world=%d", ACLITEM_GET_PRIVS(*aidat));
#endif
		return ACLCHECK_OK;
	}

	switch (idtype)
	{
		case ACL_IDTYPE_UID:
			/* See if permission is granted directly to user */
			for (i = 1, aip = aidat + 1;		/* skip world entry */
				 i < num && ACLITEM_GET_IDTYPE(*aip) == ACL_IDTYPE_UID;
				 ++i, ++aip)
			{
				if (aip->ai_id == id)
				{
#ifdef ACLDEBUG
					elog(DEBUG1, "aclcheck: found user %u/%d",
						 aip->ai_id, ACLITEM_GET_PRIVS(*aip));
#endif
					if (aip->ai_privs & mode)
						return ACLCHECK_OK;
				}
			}
			/* See if he has the permission via any group */
			for (;
				 i < num && ACLITEM_GET_IDTYPE(*aip) == ACL_IDTYPE_GID;
				 ++i, ++aip)
			{
				if (aip->ai_privs & mode)
				{
					if (in_group(id, aip->ai_id))
					{
#ifdef ACLDEBUG
						elog(DEBUG1, "aclcheck: found group %u/%d",
							 aip->ai_id, ACLITEM_GET_PRIVS(*aip));
#endif
						return ACLCHECK_OK;
					}
				}
			}
			break;
		case ACL_IDTYPE_GID:
			/* Look for this group ID */
			for (i = 1, aip = aidat + 1;		/* skip world entry */
				 i < num && ACLITEM_GET_IDTYPE(*aip) == ACL_IDTYPE_UID;
				 ++i, ++aip)
				 /* skip UID entry */ ;
			for (;
				 i < num && ACLITEM_GET_IDTYPE(*aip) == ACL_IDTYPE_GID;
				 ++i, ++aip)
			{
				if (aip->ai_id == id)
				{
#ifdef ACLDEBUG
					elog(DEBUG1, "aclcheck: found group %u/%d",
						 aip->ai_id, ACLITEM_GET_PRIVS(*aip));
#endif
					if (aip->ai_privs & mode)
						return ACLCHECK_OK;
				}
			}
			break;
		case ACL_IDTYPE_WORLD:
			/* Only check the world entry */
			break;
		default:
			elog(ERROR, "aclcheck: bogus ACL id type: %d", idtype);
			break;
	}

	/* If get here, he doesn't have the privilege nohow */
	return ACLCHECK_NO_PRIV;
}


/*
 * Exported routine for checking a user's access privileges to a table
 *
 * Returns an ACLCHECK_* result code.
 */
int32
pg_class_aclcheck(Oid table_oid, Oid userid, AclMode mode)
{
	int32		result;
	bool		usesuper,
				usecatupd;
	HeapTuple	tuple;
	Datum		aclDatum;
	bool		isNull;
	Acl		   *acl;

	/*
	 * Validate userid, find out if he is superuser, also get usecatupd
	 */
	tuple = SearchSysCache(SHADOWSYSID,
						   ObjectIdGetDatum(userid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_class_aclcheck: invalid user id %u", userid);

	usecatupd = ((Form_pg_shadow) GETSTRUCT(tuple))->usecatupd;

	ReleaseSysCache(tuple);

	usesuper = superuser_arg(userid);

	/*
	 * Now get the relation's tuple from pg_class
	 */
	tuple = SearchSysCache(RELOID,
						   ObjectIdGetDatum(table_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_class_aclcheck: relation %u not found", table_oid);

	/*
	 * Deny anyone permission to update a system catalog unless
	 * pg_shadow.usecatupd is set.	(This is to let superusers protect
	 * themselves from themselves.)
	 */
	if ((mode & (ACL_INSERT | ACL_UPDATE | ACL_DELETE)) &&
		!allowSystemTableMods &&
		IsSystemClass((Form_pg_class) GETSTRUCT(tuple)) &&
		!usecatupd)
	{
#ifdef ACLDEBUG
		elog(DEBUG1, "pg_class_aclcheck: catalog update: permission denied");
#endif
		ReleaseSysCache(tuple);
		return ACLCHECK_NO_PRIV;
	}

	/*
	 * Otherwise, superusers bypass all permission-checking.
	 */
	if (usesuper)
	{
#ifdef ACLDEBUG
		elog(DEBUG1, "pg_class_aclcheck: %u is superuser", userid);
#endif
		ReleaseSysCache(tuple);
		return ACLCHECK_OK;
	}

	/*
	 * Normal case: get the relation's ACL from pg_class
	 */
	aclDatum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_relacl,
							   &isNull);
	if (isNull)
	{
		/* No ACL, so build default ACL for rel */
		AclId		ownerId;

		ownerId = ((Form_pg_class) GETSTRUCT(tuple))->relowner;
		acl = acldefault(ACL_OBJECT_RELATION, ownerId);
		aclDatum = (Datum) 0;
	}
	else
	{
		/* detoast rel's ACL if necessary */
		acl = DatumGetAclP(aclDatum);
	}

	result = aclcheck(acl, userid, ACL_IDTYPE_UID, mode);

	/* if we have a detoasted copy, free it */
	if (acl && (Pointer) acl != DatumGetPointer(aclDatum))
		pfree(acl);

	ReleaseSysCache(tuple);

	return result;
}

/*
 * Exported routine for checking a user's access privileges to a database
 *
 * Returns an ACLCHECK_* result code.
 */
int32
pg_database_aclcheck(Oid db_oid, Oid userid, AclMode mode)
{
	int32		result;
	Relation	pg_database;
	ScanKeyData entry[1];
	HeapScanDesc scan;
	HeapTuple	tuple;
	Datum		aclDatum;
	bool		isNull;
	Acl		   *acl;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return ACLCHECK_OK;

	/*
	 * Get the database's ACL from pg_database
	 *
	 * There's no syscache for pg_database, so must look the hard way
	 */
	pg_database = heap_openr(DatabaseRelationName, AccessShareLock);
	ScanKeyEntryInitialize(&entry[0], 0x0,
						   ObjectIdAttributeNumber, F_OIDEQ,
						   ObjectIdGetDatum(db_oid));
	scan = heap_beginscan(pg_database, 0, SnapshotNow, 1, entry);
	tuple = heap_getnext(scan, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_database_aclcheck: database %u not found", db_oid);

	aclDatum = heap_getattr(tuple, Anum_pg_database_datacl,
							RelationGetDescr(pg_database), &isNull);

	if (isNull)
	{
		/* No ACL, so build default ACL */
		AclId		ownerId;

		ownerId = ((Form_pg_database) GETSTRUCT(tuple))->datdba;
		acl = acldefault(ACL_OBJECT_DATABASE, ownerId);
		aclDatum = (Datum) 0;
	}
	else
	{
		/* detoast ACL if necessary */
		acl = DatumGetAclP(aclDatum);
	}

	result = aclcheck(acl, userid, ACL_IDTYPE_UID, mode);

	/* if we have a detoasted copy, free it */
	if (acl && (Pointer) acl != DatumGetPointer(aclDatum))
		pfree(acl);

	heap_endscan(scan);
	heap_close(pg_database, AccessShareLock);

	return result;
}

/*
 * Exported routine for checking a user's access privileges to a function
 *
 * Returns an ACLCHECK_* result code.
 */
int32
pg_proc_aclcheck(Oid proc_oid, Oid userid, AclMode mode)
{
	int32		result;
	HeapTuple	tuple;
	Datum		aclDatum;
	bool		isNull;
	Acl		   *acl;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return ACLCHECK_OK;

	/*
	 * Get the function's ACL from pg_proc
	 */
	tuple = SearchSysCache(PROCOID,
						   ObjectIdGetDatum(proc_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_proc_aclcheck: function %u not found", proc_oid);

	aclDatum = SysCacheGetAttr(PROCOID, tuple, Anum_pg_proc_proacl,
							   &isNull);
	if (isNull)
	{
		/* No ACL, so build default ACL */
		AclId		ownerId;

		ownerId = ((Form_pg_proc) GETSTRUCT(tuple))->proowner;
		acl = acldefault(ACL_OBJECT_FUNCTION, ownerId);
		aclDatum = (Datum) 0;
	}
	else
	{
		/* detoast ACL if necessary */
		acl = DatumGetAclP(aclDatum);
	}

	result = aclcheck(acl, userid, ACL_IDTYPE_UID, mode);

	/* if we have a detoasted copy, free it */
	if (acl && (Pointer) acl != DatumGetPointer(aclDatum))
		pfree(acl);

	ReleaseSysCache(tuple);

	return result;
}

/*
 * Exported routine for checking a user's access privileges to a language
 *
 * Returns an ACLCHECK_* result code.
 */
int32
pg_language_aclcheck(Oid lang_oid, Oid userid, AclMode mode)
{
	int32		result;
	HeapTuple	tuple;
	Datum		aclDatum;
	bool		isNull;
	Acl		   *acl;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return ACLCHECK_OK;

	/*
	 * Get the function's ACL from pg_language
	 */
	tuple = SearchSysCache(LANGOID,
						   ObjectIdGetDatum(lang_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_language_aclcheck: language %u not found", lang_oid);

	aclDatum = SysCacheGetAttr(LANGOID, tuple, Anum_pg_language_lanacl,
							   &isNull);
	if (isNull)
	{
		/* No ACL, so build default ACL */
		acl = acldefault(ACL_OBJECT_LANGUAGE, InvalidOid);
		aclDatum = (Datum) 0;
	}
	else
	{
		/* detoast ACL if necessary */
		acl = DatumGetAclP(aclDatum);
	}

	result = aclcheck(acl, userid, ACL_IDTYPE_UID, mode);

	/* if we have a detoasted copy, free it */
	if (acl && (Pointer) acl != DatumGetPointer(aclDatum))
		pfree(acl);

	ReleaseSysCache(tuple);

	return result;
}

/*
 * Exported routine for checking a user's access privileges to a namespace
 *
 * Returns an ACLCHECK_* result code.
 */
int32
pg_namespace_aclcheck(Oid nsp_oid, Oid userid, AclMode mode)
{
	int32		result;
	HeapTuple	tuple;
	Datum		aclDatum;
	bool		isNull;
	Acl		   *acl;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return ACLCHECK_OK;

	/*
	 * Get the function's ACL from pg_namespace
	 */
	tuple = SearchSysCache(NAMESPACEOID,
						   ObjectIdGetDatum(nsp_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_namespace_aclcheck: namespace %u not found", nsp_oid);

	aclDatum = SysCacheGetAttr(NAMESPACEOID, tuple, Anum_pg_namespace_nspacl,
							   &isNull);
	if (isNull)
	{
		/* No ACL, so build default ACL */
		AclId		ownerId;

		ownerId = ((Form_pg_namespace) GETSTRUCT(tuple))->nspowner;
		acl = acldefault(ACL_OBJECT_NAMESPACE, ownerId);
		aclDatum = (Datum) 0;
	}
	else
	{
		/* detoast ACL if necessary */
		acl = DatumGetAclP(aclDatum);
	}

	result = aclcheck(acl, userid, ACL_IDTYPE_UID, mode);

	/* if we have a detoasted copy, free it */
	if (acl && (Pointer) acl != DatumGetPointer(aclDatum))
		pfree(acl);

	ReleaseSysCache(tuple);

	return result;
}


/*
 * Ownership check for a relation (specified by OID).
 */
bool
pg_class_ownercheck(Oid class_oid, Oid userid)
{
	HeapTuple	tuple;
	AclId		owner_id;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return true;

	tuple = SearchSysCache(RELOID,
						   ObjectIdGetDatum(class_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_class_ownercheck: relation %u not found", class_oid);

	owner_id = ((Form_pg_class) GETSTRUCT(tuple))->relowner;

	ReleaseSysCache(tuple);

	return userid == owner_id;
}

/*
 * Ownership check for a type (specified by OID).
 */
bool
pg_type_ownercheck(Oid type_oid, Oid userid)
{
	HeapTuple	tuple;
	AclId		owner_id;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return true;

	tuple = SearchSysCache(TYPEOID,
						   ObjectIdGetDatum(type_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_type_ownercheck: type %u not found", type_oid);

	owner_id = ((Form_pg_type) GETSTRUCT(tuple))->typowner;

	ReleaseSysCache(tuple);

	return userid == owner_id;
}

/*
 * Ownership check for an operator (specified by OID).
 */
bool
pg_oper_ownercheck(Oid oper_oid, Oid userid)
{
	HeapTuple	tuple;
	AclId		owner_id;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return true;

	tuple = SearchSysCache(OPEROID,
						   ObjectIdGetDatum(oper_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_oper_ownercheck: operator %u not found", oper_oid);

	owner_id = ((Form_pg_operator) GETSTRUCT(tuple))->oprowner;

	ReleaseSysCache(tuple);

	return userid == owner_id;
}

/*
 * Ownership check for a function (specified by OID).
 */
bool
pg_proc_ownercheck(Oid proc_oid, Oid userid)
{
	HeapTuple	tuple;
	AclId		owner_id;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return true;

	tuple = SearchSysCache(PROCOID,
						   ObjectIdGetDatum(proc_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_proc_ownercheck: function %u not found", proc_oid);

	owner_id = ((Form_pg_proc) GETSTRUCT(tuple))->proowner;

	ReleaseSysCache(tuple);

	return userid == owner_id;
}

/*
 * Ownership check for a namespace (specified by OID).
 */
bool
pg_namespace_ownercheck(Oid nsp_oid, Oid userid)
{
	HeapTuple	tuple;
	AclId		owner_id;

	/* Superusers bypass all permission checking. */
	if (superuser_arg(userid))
		return true;

	tuple = SearchSysCache(NAMESPACEOID,
						   ObjectIdGetDatum(nsp_oid),
						   0, 0, 0);
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "pg_namespace_ownercheck: namespace %u not found",
			 nsp_oid);

	owner_id = ((Form_pg_namespace) GETSTRUCT(tuple))->nspowner;

	ReleaseSysCache(tuple);

	return userid == owner_id;
}