acl.c

/*-------------------------------------------------------------------------
 *
 * acl.c
 *	  Basic access control list data structures manipulation routines.
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/adt/acl.c,v 1.130 2006/01/21 02:16:19 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>

#include "catalog/namespace.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_type.h"
#include "commands/dbcommands.h"
#include "commands/tablespace.h"
#include "miscadmin.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/syscache.h"


/*
 * We frequently need to test whether a given role is a member of some other
 * role.  In most of these tests the "given role" is the same, namely the
 * active current user.  So we can optimize it by keeping a cached list of
 * all the roles the "given role" is a member of, directly or indirectly.
 * The cache is flushed whenever we detect a change in pg_auth_members.
 *
 * There are actually two caches, one computed under "has_privs" rules
 * (do not recurse where rolinherit isn't true) and one computed under
 * "is_member" rules (recurse regardless of rolinherit).
 *
 * Possibly this mechanism should be generalized to allow caching membership
 * info for multiple roles?
 *
 * The has_privs cache is:
 * cached_privs_role is the role OID the cache is for.
 * cached_privs_roles is an OID list of roles that cached_privs_role
 *		has the privileges of (always including itself).
 * The cache is valid if cached_privs_role is not InvalidOid.
 *
 * The is_member cache is similarly:
 * cached_member_role is the role OID the cache is for.
 * cached_membership_roles is an OID list of roles that cached_member_role
 *		is a member of (always including itself).
 * The cache is valid if cached_member_role is not InvalidOid.
 */
static Oid	cached_privs_role = InvalidOid;
static List *cached_privs_roles = NIL;
static Oid	cached_member_role = InvalidOid;
static List *cached_membership_roles = NIL;


static const char *getid(const char *s, char *n);
static void putid(char *p, const char *s);
static Acl *allocacl(int n);
static void check_acl(const Acl *acl);
static const char *aclparse(const char *s, AclItem *aip);
static bool aclitem_match(const AclItem *a1, const AclItem *a2);
static void check_circularity(const Acl *old_acl, const AclItem *mod_aip,
				  Oid ownerId);
static Acl *recursive_revoke(Acl *acl, Oid grantee, AclMode revoke_privs,
				 Oid ownerId, DropBehavior behavior);
static int	oidComparator(const void *arg1, const void *arg2);

static AclMode convert_priv_string(text *priv_type_text);

static Oid	convert_table_name(text *tablename);
static AclMode convert_table_priv_string(text *priv_type_text);
static Oid	convert_database_name(text *databasename);
static AclMode convert_database_priv_string(text *priv_type_text);
static Oid	convert_function_name(text *functionname);
static AclMode convert_function_priv_string(text *priv_type_text);
static Oid	convert_language_name(text *languagename);
static AclMode convert_language_priv_string(text *priv_type_text);
static Oid	convert_schema_name(text *schemaname);
static AclMode convert_schema_priv_string(text *priv_type_text);
static Oid	convert_tablespace_name(text *tablespacename);
static AclMode convert_tablespace_priv_string(text *priv_type_text);
static AclMode convert_role_priv_string(text *priv_type_text);
static AclResult pg_role_aclcheck(Oid role_oid, Oid roleid, AclMode mode);

static void RoleMembershipCacheCallback(Datum arg, Oid relid);


/*
 * getid
 *		Consumes the first alphanumeric string (identifier) found in string
 *		's', ignoring any leading white space.	If it finds a double quote
 *		it returns the word inside the quotes.
 *
 * RETURNS:
 *		the string position in 's' that points to the next non-space character
 *		in 's', after any quotes.  Also:
 *		- loads the identifier into 'n'.  (If no identifier is found, 'n'
 *		  contains an empty string.)  'n' must be NAMEDATALEN bytes.
 */
static const char *
getid(const char *s, char *n)
{
	int			len = 0;
	bool		in_quotes = false;

	Assert(s && n);

	while (isspace((unsigned char) *s))
		s++;
	/* This code had better match what putid() does, below */
	for (;
		 *s != '\0' &&
		 (isalnum((unsigned char) *s) ||
		  *s == '_' ||
		  *s == '"' ||
		  in_quotes);
		 s++)
	{
		if (*s == '"')
		{
			/* safe to look at next char (could be '\0' though) */
			if (*(s + 1) != '"')
			{
				in_quotes = !in_quotes;
				continue;
			}
			/* it's an escaped double quote; skip the escaping char */
			s++;
		}

		/* Add the character to the string */
		if (len >= NAMEDATALEN - 1)
			ereport(ERROR,
					(errcode(ERRCODE_NAME_TOO_LONG),
					 errmsg("identifier too long"),
					 errdetail("Identifier must be less than %d characters.",
							   NAMEDATALEN)));

		n[len++] = *s;
	}
	n[len] = '\0';
	while (isspace((unsigned char) *s))
		s++;
	return s;
}

/*
 * Write a role name at *p, adding double quotes if needed.
 * There must be at least (2*NAMEDATALEN)+2 bytes available at *p.
 * This needs to be kept in sync with copyAclUserName in pg_dump/dumputils.c
 */
static void
putid(char *p, const char *s)
{
	const char *src;
	bool		safe = true;

	for (src = s; *src; src++)
	{
		/* This test had better match what getid() does, above */
		if (!isalnum((unsigned char) *src) && *src != '_')
		{
			safe = false;
			break;
		}
	}
	if (!safe)
		*p++ = '"';
	for (src = s; *src; src++)
	{
		/* A double quote character in a username is encoded as "" */
		if (*src == '"')
			*p++ = '"';
		*p++ = *src;
	}
	if (!safe)
		*p++ = '"';
	*p = '\0';
}

/*
 * aclparse
 *		Consumes and parses an ACL specification of the form:
 *				[group|user] [A-Za-z0-9]*=[rwaR]*
 *		from string 's', ignoring any leading white space or white space
 *		between the optional id type keyword (group|user) and the actual
 *		ACL specification.
 *
 *		The group|user decoration is unnecessary in the roles world,
 *		but we still accept it for backward compatibility.
 *
 *		This routine is called by the parser as well as aclitemin(), hence
 *		the added generality.
 *
 * RETURNS:
 *		the string position in 's' immediately following the ACL
 *		specification.	Also:
 *		- loads the structure pointed to by 'aip' with the appropriate
 *		  UID/GID, id type identifier and mode type values.
 */
static const char *
aclparse(const char *s, AclItem *aip)
{
	AclMode		privs,
				goption,
				read;
	char		name[NAMEDATALEN];
	char		name2[NAMEDATALEN];

	Assert(s && aip);

#ifdef ACLDEBUG
	elog(LOG, "aclparse: input = \"%s\"", s);
#endif
	s = getid(s, name);
	if (*s != '=')
	{
		/* we just read a keyword, not a name */
		if (strcmp(name, "group") != 0 && strcmp(name, "user") != 0)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("unrecognized key word: \"%s\"", name),
					 errhint("ACL key word must be \"group\" or \"user\".")));
		s = getid(s, name);		/* move s to the name beyond the keyword */
		if (name[0] == '\0')
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("missing name"),
					 errhint("A name must follow the \"group\" or \"user\" key word.")));
	}

	if (*s != '=')
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
				 errmsg("missing \"=\" sign")));

	privs = goption = ACL_NO_RIGHTS;

	for (++s, read = 0; isalpha((unsigned char) *s) || *s == '*'; s++)
	{
		switch (*s)
		{
			case '*':
				goption |= read;
				break;
			case ACL_INSERT_CHR:
				read = ACL_INSERT;
				break;
			case ACL_SELECT_CHR:
				read = ACL_SELECT;
				break;
			case ACL_UPDATE_CHR:
				read = ACL_UPDATE;
				break;
			case ACL_DELETE_CHR:
				read = ACL_DELETE;
				break;
			case ACL_RULE_CHR:
				read = ACL_RULE;
				break;
			case ACL_REFERENCES_CHR:
				read = ACL_REFERENCES;
				break;
			case ACL_TRIGGER_CHR:
				read = ACL_TRIGGER;
				break;
			case ACL_EXECUTE_CHR:
				read = ACL_EXECUTE;
				break;
			case ACL_USAGE_CHR:
				read = ACL_USAGE;
				break;
			case ACL_CREATE_CHR:
				read = ACL_CREATE;
				break;
			case ACL_CREATE_TEMP_CHR:
				read = ACL_CREATE_TEMP;
				break;
			default:
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					  errmsg("invalid mode character: must be one of \"%s\"",
							 ACL_ALL_RIGHTS_STR)));
		}

		privs |= read;
	}

	if (name[0] == '\0')
		aip->ai_grantee = ACL_ID_PUBLIC;
	else
		aip->ai_grantee = get_roleid_checked(name);

	/*
	 * XXX Allow a degree of backward compatibility by defaulting the grantor
	 * to the superuser.
	 */
	if (*s == '/')
	{
		s = getid(s + 1, name2);
		if (name2[0] == '\0')
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
					 errmsg("a name must follow the \"/\" sign")));
		aip->ai_grantor = get_roleid_checked(name2);
	}
	else
	{
		aip->ai_grantor = BOOTSTRAP_SUPERUSERID;
		ereport(WARNING,
				(errcode(ERRCODE_INVALID_GRANTOR),
				 errmsg("defaulting grantor to user ID %u",
						BOOTSTRAP_SUPERUSERID)));
	}

	ACLITEM_SET_PRIVS_GOPTIONS(*aip, privs, goption);

#ifdef ACLDEBUG
	elog(LOG, "aclparse: correctly read [%u %x %x]",
		 aip->ai_grantee, privs, goption);
#endif

	return s;
}

/*
 * allocacl
 *		Allocates storage for a new Acl with 'n' entries.
 *
 * RETURNS:
 *		the new Acl
 */
static Acl *
allocacl(int n)
{
	Acl		   *new_acl;
	Size		size;

	if (n < 0)
		elog(ERROR, "invalid size: %d", n);
	size = ACL_N_SIZE(n);
	new_acl = (Acl *) palloc0(size);
	new_acl->size = size;
	new_acl->ndim = 1;
	new_acl->dataoffset = 0;	/* we never put in any nulls */
	new_acl->elemtype = ACLITEMOID;
	ARR_LBOUND(new_acl)[0] = 1;
	ARR_DIMS(new_acl)[0] = n;
	return new_acl;
}

/*
 * Verify that an ACL array is acceptable (one-dimensional and has no nulls)
 */
static void
check_acl(const Acl *acl)
{
	if (ARR_ELEMTYPE(acl) != ACLITEMOID)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("ACL array contains wrong datatype")));
	if (ARR_NDIM(acl) != 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("ACL arrays must be one-dimensional")));
	if (ARR_HASNULL(acl))
		ereport(ERROR,
				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
				 errmsg("ACL arrays must not contain nulls")));
}

/*
 * aclitemin
 *		Allocates storage for, and fills in, a new AclItem given a string
 *		's' that contains an ACL specification.  See aclparse for details.
 *
 * RETURNS:
 *		the new AclItem
 */
Datum
aclitemin(PG_FUNCTION_ARGS)
{
	const char *s = PG_GETARG_CSTRING(0);
	AclItem    *aip;

	aip = (AclItem *) palloc(sizeof(AclItem));
	s = aclparse(s, aip);
	while (isspace((unsigned char) *s))
		++s;
	if (*s)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
			   errmsg("extra garbage at the end of the ACL specification")));

	PG_RETURN_ACLITEM_P(aip);
}

/*
 * aclitemout
 *		Allocates storage for, and fills in, a new null-delimited string
 *		containing a formatted ACL specification.  See aclparse for details.
 *
 * RETURNS:
 *		the new string
 */
Datum
aclitemout(PG_FUNCTION_ARGS)
{
	AclItem    *aip = PG_GETARG_ACLITEM_P(0);
	char	   *p;
	char	   *out;
	HeapTuple	htup;
	unsigned	i;

	out = palloc(strlen("=/") +
				 2 * N_ACL_RIGHTS +
				 2 * (2 * NAMEDATALEN + 2) +
				 1);

	p = out;
	*p = '\0';

	if (aip->ai_grantee != ACL_ID_PUBLIC)
	{
		htup = SearchSysCache(AUTHOID,
							  ObjectIdGetDatum(aip->ai_grantee),
							  0, 0, 0);
		if (HeapTupleIsValid(htup))
		{
			putid(p, NameStr(((Form_pg_authid) GETSTRUCT(htup))->rolname));
			ReleaseSysCache(htup);
		}
		else
		{
			/* Generate numeric OID if we don't find an entry */
			sprintf(p, "%u", aip->ai_grantee);
		}
	}
	while (*p)
		++p;

	*p++ = '=';

	for (i = 0; i < N_ACL_RIGHTS; ++i)
	{
		if (ACLITEM_GET_PRIVS(*aip) & (1 << i))
			*p++ = ACL_ALL_RIGHTS_STR[i];
		if (ACLITEM_GET_GOPTIONS(*aip) & (1 << i))
			*p++ = '*';
	}

	*p++ = '/';
	*p = '\0';

	htup = SearchSysCache(AUTHOID,
						  ObjectIdGetDatum(aip->ai_grantor),
						  0, 0, 0);
	if (HeapTupleIsValid(htup))
	{
		putid(p, NameStr(((Form_pg_authid) GETSTRUCT(htup))->rolname));
		ReleaseSysCache(htup);
	}
	else
	{
		/* Generate numeric OID if we don't find an entry */
		sprintf(p, "%u", aip->ai_grantor);
	}

	PG_RETURN_CSTRING(out);
}

/*
 * aclitem_match
 *		Two AclItems are considered to match iff they have the same
 *		grantee and grantor; the privileges are ignored.
 */
static bool
aclitem_match(const AclItem *a1, const AclItem *a2)
{
	return a1->ai_grantee == a2->ai_grantee &&
		a1->ai_grantor == a2->ai_grantor;
}

/*
 * aclitem equality operator
 */
Datum
aclitem_eq(PG_FUNCTION_ARGS)
{
	AclItem    *a1 = PG_GETARG_ACLITEM_P(0);
	AclItem    *a2 = PG_GETARG_ACLITEM_P(1);
	bool		result;

	result = a1->ai_privs == a2->ai_privs &&
		a1->ai_grantee == a2->ai_grantee &&
		a1->ai_grantor == a2->ai_grantor;
	PG_RETURN_BOOL(result);
}

/*
 * aclitem hash function
 *
 * We make aclitems hashable not so much because anyone is likely to hash
 * them, as because we want array equality to work on aclitem arrays, and
 * with the typcache mechanism we must have a hash or btree opclass.
 */
Datum
hash_aclitem(PG_FUNCTION_ARGS)
{
	AclItem    *a = PG_GETARG_ACLITEM_P(0);

	/* not very bright, but avoids any issue of padding in struct */
	PG_RETURN_UINT32((uint32) (a->ai_privs + a->ai_grantee + a->ai_grantor));
}


/*
 * acldefault()  --- create an ACL describing default access permissions
 *
 * Change this routine if you want to alter the default access policy for
 * newly-created objects (or any object with a NULL acl entry).
 */
Acl *
acldefault(GrantObjectType objtype, Oid ownerId)
{
	AclMode		world_default;
	AclMode		owner_default;
	Acl		   *acl;
	AclItem    *aip;

	switch (objtype)
	{
		case ACL_OBJECT_RELATION:
			world_default = ACL_NO_RIGHTS;
			owner_default = ACL_ALL_RIGHTS_RELATION;
			break;
		case ACL_OBJECT_SEQUENCE:
			world_default = ACL_NO_RIGHTS;
			owner_default = ACL_ALL_RIGHTS_SEQUENCE;
			break;
		case ACL_OBJECT_DATABASE:
			world_default = ACL_CREATE_TEMP;	/* not NO_RIGHTS! */
			owner_default = ACL_ALL_RIGHTS_DATABASE;
			break;
		case ACL_OBJECT_FUNCTION:
			/* Grant EXECUTE by default, for now */
			world_default = ACL_EXECUTE;
			owner_default = ACL_ALL_RIGHTS_FUNCTION;
			break;
		case ACL_OBJECT_LANGUAGE:
			/* Grant USAGE by default, for now */
			world_default = ACL_USAGE;
			owner_default = ACL_ALL_RIGHTS_LANGUAGE;
			break;
		case ACL_OBJECT_NAMESPACE:
			world_default = ACL_NO_RIGHTS;
			owner_default = ACL_ALL_RIGHTS_NAMESPACE;
			break;
		case ACL_OBJECT_TABLESPACE:
			world_default = ACL_NO_RIGHTS;
			owner_default = ACL_ALL_RIGHTS_TABLESPACE;
			break;
		default:
			elog(ERROR, "unrecognized objtype: %d", (int) objtype);
			world_default = ACL_NO_RIGHTS;		/* keep compiler quiet */
			owner_default = ACL_NO_RIGHTS;
			break;
	}

	acl = allocacl((world_default != ACL_NO_RIGHTS) ? 2 : 1);
	aip = ACL_DAT(acl);

	if (world_default != ACL_NO_RIGHTS)
	{
		aip->ai_grantee = ACL_ID_PUBLIC;
		aip->ai_grantor = ownerId;
		ACLITEM_SET_PRIVS_GOPTIONS(*aip, world_default, ACL_NO_RIGHTS);
		aip++;
	}

	/*
	 * Note that the owner's entry shows all ordinary privileges but no grant
	 * options.  This is because his grant options come "from the system" and
	 * not from his own efforts.  (The SQL spec says that the owner's rights
	 * come from a "_SYSTEM" authid.)  However, we do consider that the
	 * owner's ordinary privileges are self-granted; this lets him revoke
	 * them.  We implement the owner's grant options without any explicit
	 * "_SYSTEM"-like ACL entry, by internally special-casing the owner
	 * whereever we are testing grant options.
	 */
	aip->ai_grantee = ownerId;
	aip->ai_grantor = ownerId;
	ACLITEM_SET_PRIVS_GOPTIONS(*aip, owner_default, ACL_NO_RIGHTS);

	return acl;
}


/*
 * Update an ACL array to add or remove specified privileges.
 *
 *	old_acl: the input ACL array
 *	mod_aip: defines the privileges to be added, removed, or substituted
 *	modechg: ACL_MODECHG_ADD, ACL_MODECHG_DEL, or ACL_MODECHG_EQL
 *	ownerId: Oid of object owner
 *	behavior: RESTRICT or CASCADE behavior for recursive removal
 *
 * ownerid and behavior are only relevant when the update operation specifies
 * deletion of grant options.
 *
 * The result is a modified copy; the input object is not changed.
 *
 * NB: caller is responsible for having detoasted the input ACL, if needed.
 */
Acl *
aclupdate(const Acl *old_acl, const AclItem *mod_aip,
		  int modechg, Oid ownerId, DropBehavior behavior)
{
	Acl		   *new_acl = NULL;
	AclItem    *old_aip,
			   *new_aip = NULL;
	AclMode		old_rights,
				old_goptions,
				new_rights,
				new_goptions;
	int			dst,
				num;

	/* Caller probably already checked old_acl, but be safe */
	check_acl(old_acl);

	/* If granting grant options, check for circularity */
	if (modechg != ACL_MODECHG_DEL &&
		ACLITEM_GET_GOPTIONS(*mod_aip) != ACL_NO_RIGHTS)
		check_circularity(old_acl, mod_aip, ownerId);

	num = ACL_NUM(old_acl);
	old_aip = ACL_DAT(old_acl);

	/*
	 * Search the ACL for an existing entry for this grantee and grantor. If
	 * one exists, just modify the entry in-place (well, in the same position,
	 * since we actually return a copy); otherwise, insert the new entry at
	 * the end.
	 */

	for (dst = 0; dst < num; ++dst)
	{
		if (aclitem_match(mod_aip, old_aip + dst))
		{
			/* found a match, so modify existing item */
			new_acl = allocacl(num);
			new_aip = ACL_DAT(new_acl);
			memcpy(new_acl, old_acl, ACL_SIZE(old_acl));
			break;
		}
	}

	if (dst == num)
	{
		/* need to append a new item */
		new_acl = allocacl(num + 1);
		new_aip = ACL_DAT(new_acl);
		memcpy(new_aip, old_aip, num * sizeof(AclItem));

		/* initialize the new entry with no permissions */
		new_aip[dst].ai_grantee = mod_aip->ai_grantee;
		new_aip[dst].ai_grantor = mod_aip->ai_grantor;
		ACLITEM_SET_PRIVS_GOPTIONS(new_aip[dst],
								   ACL_NO_RIGHTS, ACL_NO_RIGHTS);
		num++;					/* set num to the size of new_acl */
	}

	old_rights = ACLITEM_GET_RIGHTS(new_aip[dst]);
	old_goptions = ACLITEM_GET_GOPTIONS(new_aip[dst]);

	/* apply the specified permissions change */
	switch (modechg)
	{
		case ACL_MODECHG_ADD:
			ACLITEM_SET_RIGHTS(new_aip[dst],
							   old_rights | ACLITEM_GET_RIGHTS(*mod_aip));
			break;
		case ACL_MODECHG_DEL:
			ACLITEM_SET_RIGHTS(new_aip[dst],
							   old_rights & ~ACLITEM_GET_RIGHTS(*mod_aip));
			break;
		case ACL_MODECHG_EQL:
			ACLITEM_SET_RIGHTS(new_aip[dst],
							   ACLITEM_GET_RIGHTS(*mod_aip));
			break;
	}

	new_rights = ACLITEM_GET_RIGHTS(new_aip[dst]);
	new_goptions = ACLITEM_GET_GOPTIONS(new_aip[dst]);

	/*
	 * If the adjusted entry has no permissions, delete it from the list.
	 */
	if (new_rights == ACL_NO_RIGHTS)
	{
		memmove(new_aip + dst,
				new_aip + dst + 1,
				(num - dst - 1) * sizeof(AclItem));
		ARR_DIMS(new_acl)[0] = num - 1;
		ARR_SIZE(new_acl) -= sizeof(AclItem);
	}

	/*
	 * Remove abandoned privileges (cascading revoke).	Currently we can only
	 * handle this when the grantee is not PUBLIC.
	 */
	if ((old_goptions & ~new_goptions) != 0)
	{
		Assert(mod_aip->ai_grantee != ACL_ID_PUBLIC);
		new_acl = recursive_revoke(new_acl, mod_aip->ai_grantee,
								   (old_goptions & ~new_goptions),
								   ownerId, behavior);
	}

	return new_acl;
}

/*
 * Update an ACL array to reflect a change of owner to the parent object
 *
 *	old_acl: the input ACL array (must not be NULL)
 *	oldOwnerId: Oid of the old object owner
 *	newOwnerId: Oid of the new object owner
 *
 * The result is a modified copy; the input object is not changed.
 *
 * NB: caller is responsible for having detoasted the input ACL, if needed.
 */
Acl *
aclnewowner(const Acl *old_acl, Oid oldOwnerId, Oid newOwnerId)
{
	Acl		   *new_acl;
	AclItem    *new_aip;
	AclItem    *old_aip;
	AclItem    *dst_aip;
	AclItem    *src_aip;
	AclItem    *targ_aip;
	bool		newpresent = false;
	int			dst,
				src,
				targ,
				num;

	check_acl(old_acl);

	/*
	 * Make a copy of the given ACL, substituting new owner ID for old
	 * wherever it appears as either grantor or grantee.  Also note if the new
	 * owner ID is already present.
	 */
	num = ACL_NUM(old_acl);
	old_aip = ACL_DAT(old_acl);
	new_acl = allocacl(num);
	new_aip = ACL_DAT(new_acl);
	memcpy(new_aip, old_aip, num * sizeof(AclItem));
	for (dst = 0, dst_aip = new_aip; dst < num; dst++, dst_aip++)
	{
		if (dst_aip->ai_grantor == oldOwnerId)
			dst_aip->ai_grantor = newOwnerId;
		else if (dst_aip->ai_grantor == newOwnerId)
			newpresent = true;
		if (dst_aip->ai_grantee == oldOwnerId)
			dst_aip->ai_grantee = newOwnerId;
		else if (dst_aip->ai_grantee == newOwnerId)
			newpresent = true;
	}

	/*
	 * If the old ACL contained any references to the new owner, then we may
	 * now have generated an ACL containing duplicate entries.	Find them and
	 * merge them so that there are not duplicates.  (This is relatively
	 * expensive since we use a stupid O(N^2) algorithm, but it's unlikely to
	 * be the normal case.)
	 *
	 * To simplify deletion of duplicate entries, we temporarily leave them in
	 * the array but set their privilege masks to zero; when we reach such an
	 * entry it's just skipped.  (Thus, a side effect of this code will be to
	 * remove privilege-free entries, should there be any in the input.)  dst
	 * is the next output slot, targ is the currently considered input slot
	 * (always >= dst), and src scans entries to the right of targ looking for
	 * duplicates.	Once an entry has been emitted to dst it is known
	 * duplicate-free and need not be considered anymore.
	 */
	if (newpresent)
	{
		dst = 0;
		for (targ = 0, targ_aip = new_aip; targ < num; targ++, targ_aip++)
		{
			/* ignore if deleted in an earlier pass */
			if (ACLITEM_GET_RIGHTS(*targ_aip) == ACL_NO_RIGHTS)
				continue;
			/* find and merge any duplicates */
			for (src = targ + 1, src_aip = targ_aip + 1; src < num;
				 src++, src_aip++)
			{
				if (ACLITEM_GET_RIGHTS(*src_aip) == ACL_NO_RIGHTS)
					continue;
				if (aclitem_match(targ_aip, src_aip))
				{
					ACLITEM_SET_RIGHTS(*targ_aip,
									   ACLITEM_GET_RIGHTS(*targ_aip) |
									   ACLITEM_GET_RIGHTS(*src_aip));
					/* mark the duplicate deleted */
					ACLITEM_SET_RIGHTS(*src_aip, ACL_NO_RIGHTS);
				}
			}
			/* and emit to output */
			new_aip[dst] = *targ_aip;
			dst++;
		}
		/* Adjust array size to be 'dst' items */
		ARR_DIMS(new_acl)[0] = dst;
		ARR_SIZE(new_acl) = ACL_N_SIZE(dst);
	}

	return new_acl;
}


/*
 * When granting grant options, we must disallow attempts to set up circular
 * chains of grant options.  Suppose A (the object owner) grants B some
 * privileges with grant option, and B re-grants them to C.  If C could
 * grant the privileges to B as well, then A would be unable to effectively
 * revoke the privileges from B, since recursive_revoke would consider that
 * B still has 'em from C.
 *
 * We check for this by recursively deleting all grant options belonging to
 * the target grantee, and then seeing if the would-be grantor still has the
 * grant option or not.
 */
static void
check_circularity(const Acl *old_acl, const AclItem *mod_aip,
				  Oid ownerId)
{
	Acl		   *acl;
	AclItem    *aip;
	int			i,
				num;
	AclMode		own_privs;

	check_acl(old_acl);

	/*
	 * For now, grant options can only be granted to roles, not PUBLIC.
	 * Otherwise we'd have to work a bit harder here.
	 */
	Assert(mod_aip->ai_grantee != ACL_ID_PUBLIC);

	/* The owner always has grant options, no need to check */
	if (mod_aip->ai_grantor == ownerId)
		return;

	/* Make a working copy */
	acl = allocacl(ACL_NUM(old_acl));
	memcpy(acl, old_acl, ACL_SIZE(old_acl));

	/* Zap all grant options of target grantee, plus what depends on 'em */
cc_restart:
	num = ACL_NUM(acl);
	aip = ACL_DAT(acl);
	for (i = 0; i < num; i++)
	{
		if (aip[i].ai_grantee == mod_aip->ai_grantee &&
			ACLITEM_GET_GOPTIONS(aip[i]) != ACL_NO_RIGHTS)
		{
			Acl		   *new_acl;

			/* We'll actually zap ordinary privs too, but no matter */
			new_acl = aclupdate(acl, &aip[i], ACL_MODECHG_DEL,
								ownerId, DROP_CASCADE);

			pfree(acl);
			acl = new_acl;

			goto cc_restart;
		}
	}

	/* Now we can compute grantor's independently-derived privileges */
	own_privs = aclmask(acl,
						mod_aip->ai_grantor,
						ownerId,
						ACL_GRANT_OPTION_FOR(ACLITEM_GET_GOPTIONS(*mod_aip)),
						ACLMASK_ALL);
	own_privs = ACL_OPTION_TO_PRIVS(own_privs);

	if ((ACLITEM_GET_GOPTIONS(*mod_aip) & ~own_privs) != 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_GRANT_OPERATION),
		errmsg("grant options cannot be granted back to your own grantor")));

	pfree(acl);
}


/*
 * Ensure that no privilege is "abandoned".  A privilege is abandoned
 * if the user that granted the privilege loses the grant option.  (So
 * the chain through which it was granted is broken.)  Either the
 * abandoned privileges are revoked as well, or an error message is
 * printed, depending on the drop behavior option.
 *
 *	acl: the input ACL list
 *	grantee: the user from whom some grant options have been revoked
 *	revoke_privs: the grant options being revoked
 *	ownerId: Oid of object owner
 *	behavior: RESTRICT or CASCADE behavior for recursive removal
 *
 * The input Acl object is pfree'd if replaced.
 */
static Acl *
recursive_revoke(Acl *acl,
				 Oid grantee,
				 AclMode revoke_privs,
				 Oid ownerId,
				 DropBehavior behavior)
{
	AclMode		still_has;
	AclItem    *aip;
	int			i,
				num;

	check_acl(acl);

	/* The owner can never truly lose grant options, so short-circuit */
	if (grantee == ownerId)
		return acl;

	/* The grantee might still have the privileges via another grantor */
	still_has = aclmask(acl, grantee, ownerId,
						ACL_GRANT_OPTION_FOR(revoke_privs),
						ACLMASK_ALL);
	revoke_privs &= ~still_has;
	if (revoke_privs == ACL_NO_RIGHTS)
		return acl;

restart:
	num = ACL_NUM(acl);
	aip = ACL_DAT(acl);
	for (i = 0; i < num; i++)
	{
		if (aip[i].ai_grantor == grantee
			&& (ACLITEM_GET_PRIVS(aip[i]) & revoke_privs) != 0)
		{
			AclItem		mod_acl;
			Acl		   *new_acl;

			if (behavior == DROP_RESTRICT)
				ereport(ERROR,
						(errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
						 errmsg("dependent privileges exist"),
						 errhint("Use CASCADE to revoke them too.")));

			mod_acl.ai_grantor = grantee;
			mod_acl.ai_grantee = aip[i].ai_grantee;
			ACLITEM_SET_PRIVS_GOPTIONS(mod_acl,
									   revoke_privs,
									   revoke_privs);

			new_acl = aclupdate(acl, &mod_acl, ACL_MODECHG_DEL,
								ownerId, behavior);

			pfree(acl);
			acl = new_acl;

			goto restart;
		}
	}

	return acl;
}


/*
 * aclmask --- compute bitmask of all privileges held by roleid.
 *
 * When 'how' = ACLMASK_ALL, this simply returns the privilege bits
 * held by the given roleid according to the given ACL list, ANDed
 * with 'mask'.  (The point of passing 'mask' is to let the routine
 * exit early if all privileges of interest have been found.)
 *
 * When 'how' = ACLMASK_ANY, returns as soon as any bit in the mask