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Improved version of patch to protect pg_get_expr() against misuse:
look through join alias Vars to avoid breaking join queries, and move the test to someplace where it will catch more possible ways of calling a function. We still ought to throw away the whole thing in favor of a data-type-based solution, but that's not feasible in the back branches. Completion of back-port of my patch of yesterday.
This commit is contained in:
Tom Lane
parent
8e21bf5250
commit
1eef280d61
@ -8,16 +8,13 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.179.4.4 2010/06/30 18:11:31 heikki Exp $
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* $PostgreSQL: pgsql/src/backend/parser/parse_expr.c,v 1.179.4.5 2010/07/30 17:57:24 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "catalog/catname.h"
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#include "catalog/pg_attrdef.h"
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#include "catalog/pg_constraint.h"
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#include "catalog/pg_operator.h"
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#include "catalog/pg_proc.h"
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#include "commands/dbcommands.h"
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@ -35,7 +32,6 @@
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#include "parser/parse_relation.h"
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#include "parser/parse_type.h"
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#include "utils/builtins.h"
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#include "utils/fmgroids.h"
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#include "utils/lsyscache.h"
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#include "utils/syscache.h"
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@ -439,82 +435,6 @@ transformExpr(ParseState *pstate, Node *expr)
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fn->agg_star,
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fn->agg_distinct,
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false);
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/*
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* pg_get_expr() is a system function that exposes the
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* expression deparsing functionality in ruleutils.c to users.
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* Very handy, but it was later realized that the functions in
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* ruleutils.c don't check the input rigorously, assuming it to
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* come from system catalogs and to therefore be valid. That
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* makes it easy for a user to crash the backend by passing a
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* maliciously crafted string representation of an expression
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* to pg_get_expr().
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*
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* There's a lot of code in ruleutils.c, so it's not feasible
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* to add water-proof input checking after the fact. Even if
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* we did it once, it would need to be taken into account in
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* any future patches too.
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*
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* Instead, we restrict pg_rule_expr() to only allow input from
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* system catalogs instead. This is a hack, but it's the most
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* robust and easiest to backpatch way of plugging the
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* vulnerability.
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*
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* This is transparent to the typical usage pattern of
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* "pg_get_expr(systemcolumn, ...)", but will break
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* "pg_get_expr('foo', ...)", even if 'foo' is a valid
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* expression fetched earlier from a system catalog. Hopefully
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* there's isn't many clients doing that out there.
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*/
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if (result && IsA(result, FuncExpr) && !superuser())
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{
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FuncExpr *fe = (FuncExpr *) result;
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if (fe->funcid == F_PG_GET_EXPR ||
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fe->funcid == F_PG_GET_EXPR_EXT)
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{
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Expr *arg = linitial(fe->args);
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bool allowed = false;
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/*
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* Check that the argument came directly from one of the
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* allowed system catalog columns
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*/
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if (IsA(arg, Var))
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{
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Var *var = (Var *) arg;
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RangeTblEntry *rte;
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rte = GetRTEByRangeTablePosn(pstate,
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var->varno, var->varlevelsup);
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if (rte->relid == get_system_catalog_relid(IndexRelationName))
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{
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if (var->varattno == Anum_pg_index_indexprs ||
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var->varattno == Anum_pg_index_indpred)
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allowed = true;
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}
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else if (rte->relid == get_system_catalog_relid(AttrDefaultRelationName))
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{
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if (var->varattno == Anum_pg_attrdef_adbin)
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allowed = true;
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}
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else if (rte->relid == get_system_catalog_relid(ConstraintRelationName))
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{
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if (var->varattno == Anum_pg_constraint_conbin)
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allowed = true;
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}
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else if (rte->relid == get_system_catalog_relid(TypeRelationName))
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{
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if (var->varattno == Anum_pg_type_typdefaultbin)
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allowed = true;
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}
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}
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if (!allowed)
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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errmsg("argument to pg_get_expr() must come from system catalogs")));
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}
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}
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break;
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}
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case T_SubLink:
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/parser/parse_func.c,v 1.175 2004/12/31 22:00:27 pgsql Exp $
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* $PostgreSQL: pgsql/src/backend/parser/parse_func.c,v 1.175.4.1 2010/07/30 17:57:24 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -16,9 +16,12 @@
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#include "access/heapam.h"
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#include "catalog/catname.h"
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#include "catalog/pg_attrdef.h"
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#include "catalog/pg_constraint.h"
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#include "catalog/pg_inherits.h"
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#include "catalog/pg_proc.h"
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#include "lib/stringinfo.h"
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#include "miscadmin.h"
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#include "nodes/makefuncs.h"
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#include "parser/parse_agg.h"
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#include "parser/parse_coerce.h"
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@ -255,6 +258,9 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
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errmsg("aggregates may not return sets")));
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}
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/* Hack to protect pg_get_expr() against misuse */
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check_pg_get_expr_args(pstate, funcid, fargs);
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return retval;
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}
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@ -1406,3 +1412,100 @@ LookupFuncNameTypeNames(List *funcname, List *argtypes, bool noError)
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return LookupFuncName(funcname, argcount, argoids, noError);
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}
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/*
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* pg_get_expr() is a system function that exposes the expression
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* deparsing functionality in ruleutils.c to users. Very handy, but it was
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* later realized that the functions in ruleutils.c don't check the input
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* rigorously, assuming it to come from system catalogs and to therefore
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* be valid. That makes it easy for a user to crash the backend by passing
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* a maliciously crafted string representation of an expression to
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* pg_get_expr().
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*
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* There's a lot of code in ruleutils.c, so it's not feasible to add
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* water-proof input checking after the fact. Even if we did it once, it
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* would need to be taken into account in any future patches too.
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*
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* Instead, we restrict pg_rule_expr() to only allow input from system
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* catalogs. This is a hack, but it's the most robust and easiest
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* to backpatch way of plugging the vulnerability.
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*
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* This is transparent to the typical usage pattern of
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* "pg_get_expr(systemcolumn, ...)", but will break "pg_get_expr('foo',
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* ...)", even if 'foo' is a valid expression fetched earlier from a
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* system catalog. Hopefully there aren't many clients doing that out there.
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*/
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void
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check_pg_get_expr_args(ParseState *pstate, Oid fnoid, List *args)
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{
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bool allowed = false;
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Node *arg;
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int netlevelsup;
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/* if not being called for pg_get_expr, do nothing */
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if (fnoid != F_PG_GET_EXPR && fnoid != F_PG_GET_EXPR_EXT)
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return;
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/* superusers are allowed to call it anyway (dubious) */
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if (superuser())
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return;
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/*
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* The first argument must be a Var referencing one of the allowed
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* system-catalog columns. It could be a join alias Var, though.
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*/
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Assert(list_length(args) > 1);
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arg = (Node *) linitial(args);
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netlevelsup = 0;
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restart:
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if (IsA(arg, Var))
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{
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Var *var = (Var *) arg;
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RangeTblEntry *rte;
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netlevelsup += var->varlevelsup;
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rte = GetRTEByRangeTablePosn(pstate, var->varno, netlevelsup);
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if (rte->rtekind == RTE_JOIN)
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{
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/* Expand join alias reference */
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if (var->varattno > 0 &&
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var->varattno <= list_length(rte->joinaliasvars))
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{
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arg = (Node *) list_nth(rte->joinaliasvars, var->varattno - 1);
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goto restart;
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}
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}
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else if (rte->rtekind == RTE_RELATION)
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{
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if (rte->relid == get_system_catalog_relid(IndexRelationName))
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{
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if (var->varattno == Anum_pg_index_indexprs ||
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var->varattno == Anum_pg_index_indpred)
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allowed = true;
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}
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else if (rte->relid == get_system_catalog_relid(AttrDefaultRelationName))
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{
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if (var->varattno == Anum_pg_attrdef_adbin)
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allowed = true;
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}
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else if (rte->relid == get_system_catalog_relid(ConstraintRelationName))
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{
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if (var->varattno == Anum_pg_constraint_conbin)
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allowed = true;
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}
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else if (rte->relid == get_system_catalog_relid(TypeRelationName))
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{
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if (var->varattno == Anum_pg_type_typdefaultbin)
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allowed = true;
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}
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}
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}
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if (!allowed)
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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errmsg("argument to pg_get_expr() must come from system catalogs")));
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}
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/parser/parse_oper.c,v 1.81 2004/12/31 22:00:27 pgsql Exp $
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* $PostgreSQL: pgsql/src/backend/parser/parse_oper.c,v 1.81.4.1 2010/07/30 17:57:24 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -932,6 +932,9 @@ make_scalar_array_op(ParseState *pstate, List *opname,
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result->useOr = useOr;
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result->args = args;
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/* Hack to protect pg_get_expr() against misuse */
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check_pg_get_expr_args(pstate, opform->oprcode, args);
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ReleaseSysCache(tup);
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return (Expr *) result;
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@ -1005,5 +1008,8 @@ make_op_expr(ParseState *pstate, Operator op,
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result->opretset = get_func_retset(opform->oprcode);
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result->args = args;
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/* Hack to protect pg_get_expr() against misuse */
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check_pg_get_expr_args(pstate, opform->oprcode, args);
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return (Expr *) result;
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}
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/parser/parse_func.h,v 1.53 2004/12/31 22:03:38 pgsql Exp $
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* $PostgreSQL: pgsql/src/include/parser/parse_func.h,v 1.53.4.1 2010/07/30 17:57:25 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -78,4 +78,6 @@ extern Oid LookupFuncName(List *funcname, int nargs, const Oid *argtypes,
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extern Oid LookupFuncNameTypeNames(List *funcname, List *argtypes,
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bool noError);
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extern void check_pg_get_expr_args(ParseState *pstate, Oid fnoid, List *args);
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#endif /* PARSE_FUNC_H */
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