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Avoid repeated name lookups during table and index DDL.

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If the name lookups come to different conclusions due to concurrent
activity, we might perform some parts of the DDL on a different table
than other parts.  At least in the case of CREATE INDEX, this can be
used to cause the permissions checks to be performed against a
different table than the index creation, allowing for a privilege
escalation attack.

This changes the calling convention for DefineIndex, CreateTrigger,
transformIndexStmt, transformAlterTableStmt, CheckIndexCompatible
(in 9.2 and newer), and AlterTable (in 9.1 and older).  In addition,
CheckRelationOwnership is removed in 9.2 and newer and the calling
convention is changed in older branches.  A field has also been added
to the Constraint node (FkConstraint in 8.4).  Third-party code calling
these functions or using the Constraint node will require updating.

Report by Andres Freund.  Patch by Robert Haas and Andres Freund,
reviewed by Tom Lane.

Security: CVE-2014-0062
This commit is contained in:
Robert Haas
2014-02-17 09:33:31 -05:00
parent 540b4e5bc8
commit 5f173040e3
18 changed files with 233 additions and 157 deletions
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73
src/backend/tcop/utility.c
View File

@@ -78,49 +78,6 @@ static void ProcessUtilitySlow(Node *parsetree,
static void ExecDropStmt(DropStmt *stmt, bool isTopLevel);
/*
* Verify user has ownership of specified relation, else ereport.
*
* If noCatalogs is true then we also deny access to system catalogs,
* except when allowSystemTableMods is true.
*/
void
CheckRelationOwnership(RangeVar *rel, bool noCatalogs)
{
Oid relOid;
HeapTuple tuple;
/*
* XXX: This is unsafe in the presence of concurrent DDL, since it is
* called before acquiring any lock on the target relation. However,
* locking the target relation (especially using something like
* AccessExclusiveLock) before verifying that the user has permissions is
* not appealing either.
*/
relOid = RangeVarGetRelid(rel, NoLock, false);
tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relOid));
if (!HeapTupleIsValid(tuple)) /* should not happen */
elog(ERROR, "cache lookup failed for relation %u", relOid);
if (!pg_class_ownercheck(relOid, GetUserId()))
aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
rel->relname);
if (noCatalogs)
{
if (!allowSystemTableMods &&
IsSystemClass(relOid, (Form_pg_class) GETSTRUCT(tuple)))
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("permission denied: \"%s\" is a system catalog",
rel->relname)));
}
ReleaseSysCache(tuple);
}
/*
* CommandIsReadOnly: is an executable query read-only?
*
@@ -1019,7 +976,8 @@ ProcessUtilitySlow(Node *parsetree,
if (OidIsValid(relid))
{
/* Run parse analysis ... */
stmts = transformAlterTableStmt(atstmt, queryString);
stmts = transformAlterTableStmt(relid, atstmt,
queryString);
/* ... and do it */
foreach(l, stmts)
@@ -1160,18 +1118,36 @@ ProcessUtilitySlow(Node *parsetree,
case T_IndexStmt: /* CREATE INDEX */
{
IndexStmt *stmt = (IndexStmt *) parsetree;
Oid relid;
LOCKMODE lockmode;
if (stmt->concurrent)
PreventTransactionChain(isTopLevel,
"CREATE INDEX CONCURRENTLY");
CheckRelationOwnership(stmt->relation, true);
/*
* Look up the relation OID just once, right here at the
* beginning, so that we don't end up repeating the name
* lookup later and latching onto a different relation
* partway through. To avoid lock upgrade hazards, it's
* important that we take the strongest lock that will
* eventually be needed here, so the lockmode calculation
* needs to match what DefineIndex() does.
*/
lockmode = stmt->concurrent ? ShareUpdateExclusiveLock
: ShareLock;
relid =
RangeVarGetRelidExtended(stmt->relation, lockmode,
false, false,
RangeVarCallbackOwnsRelation,
NULL);
/* Run parse analysis ... */
stmt = transformIndexStmt(stmt, queryString);
stmt = transformIndexStmt(relid, stmt, queryString);
/* ... and do it */
DefineIndex(stmt,
DefineIndex(relid, /* OID of heap relation */
stmt,
InvalidOid, /* no predefined OID */
false, /* is_alter_table */
true, /* check_rights */
@@ -1276,7 +1252,8 @@ ProcessUtilitySlow(Node *parsetree,
case T_CreateTrigStmt:
(void) CreateTrigger((CreateTrigStmt *) parsetree, queryString,
InvalidOid, InvalidOid, false);
InvalidOid, InvalidOid, InvalidOid,
InvalidOid, false);
break;
case T_CreatePLangStmt: