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Restrict virtual columns to use built-in functions and types

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Just like selecting from a view is exploitable (CVE-2024-7348),
selecting from a table with virtual generated columns is exploitable.
Users who are concerned about this can avoid selecting from views, but
telling them to avoid selecting from tables is less practical.

To address this, this changes it so that generation expressions for
virtual generated columns are restricted to using built-in functions
and types, and the columns are restricted to having a built-in type.
We assume that built-in functions and types cannot be exploited for
this purpose.

In the future, this could be expanded by some new mechanism to declare
other functions and types as safe or trusted for this purpose, but
that is to be designed.

(An alternative approach might have been to expand the
restrict_nonsystem_relation_kind GUC to handle this, like the fix for
CVE-2024-7348.  But that is kind of an ugly approach.  That fix had to
fit in the constraints of fixing an ancient vulnerability in all
branches.  Since virtual generated columns are new, we're free from
the constraints of the past, and we can and should use cleaner
options.)

Reported-by: Feike Steenbergen <feikesteenbergen@gmail.com>
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAK_s-G2Q7de8Q0qOYUR%3D_CTB5FzzVBm5iZjOp%2BmeVWpMpmfO0w%40mail.gmail.com
This commit is contained in:
Peter Eisentraut
2025-06-25 09:55:04 +02:00
parent 69e5cdc47f
commit 0cd69b3d7e
8 changed files with 163 additions and 35 deletions
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10
doc/src/sgml/ddl.sgml
View File

@ -419,6 +419,16 @@ CREATE TABLE people (
<varname>tableoid</varname>.
</para>
</listitem>
<listitem>
<para>
A virtual generated column cannot have a user-defined type, and the
generation expression of a virtual generated column must not reference
user-defined functions or types, that is, it can only use built-in
functions or types. This applies also indirectly, such as for functions
or types that underlie operators or casts. (This restriction does not
exist for stored generated columns.)
</para>
</listitem>
<listitem>
<para>
A generated column cannot have a column default or an identity definition.

9
doc/src/sgml/ref/create_table.sgml
View File

@ -924,6 +924,15 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
not other generated columns. Any functions and operators used must be
immutable. References to other tables are not allowed.
</para>
<para>
A virtual generated column cannot have a user-defined type, and the
generation expression of a virtual generated column must not reference
user-defined functions or types, that is, it can only use built-in
functions or types. This applies also indirectly, such as for functions
or types that underlie operators or casts. (This restriction does not
exist for stored generated columns.)
</para>
</listitem>
</varlistentry>

93
src/backend/catalog/heap.c
View File

@ -664,6 +664,15 @@ CheckAttributeType(const char *attname,
flags);
}
/*
* For consistency with check_virtual_generated_security().
*/
if ((flags & CHKATYPE_IS_VIRTUAL) && atttypid >= FirstUnpinnedObjectId)
ereport(ERROR,
errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("virtual generated column \"%s\" cannot have a user-defined type", attname),
errdetail("Virtual generated columns that make use of user-defined types are not yet supported."));
/*
* This might not be strictly invalid per SQL standard, but it is pretty
* useless, and it cannot be dumped, so we must disallow it.
@ -3215,6 +3224,86 @@ check_nested_generated(ParseState *pstate, Node *node)
check_nested_generated_walker(node, pstate);
}
/*
* Check security of virtual generated column expression.
*
* Just like selecting from a view is exploitable (CVE-2024-7348), selecting
* from a table with virtual generated columns is exploitable. Users who are
* concerned about this can avoid selecting from views, but telling them to
* avoid selecting from tables is less practical.
*
* To address this, this restricts generation expressions for virtual
* generated columns are restricted to using built-in functions and types. We
* assume that built-in functions and types cannot be exploited for this
* purpose. Note the overall security also requires that all functions in use
* a immutable. (For example, there are some built-in non-immutable functions
* that can run arbitrary SQL.) The immutability is checked elsewhere, since
* that is a property that needs to hold independent of security
* considerations.
*
* In the future, this could be expanded by some new mechanism to declare
* other functions and types as safe or trusted for this purpose, but that is
* to be designed.
*/
/*
* Callback for check_functions_in_node() that determines whether a function
* is user-defined.
*/
static bool
contains_user_functions_checker(Oid func_id, void *context)
{
return (func_id >= FirstUnpinnedObjectId);
}
/*
* Checks for all the things we don't want in the generation expressions of
* virtual generated columns for security reasons. Errors out if it finds
* one.
*/
static bool
check_virtual_generated_security_walker(Node *node, void *context)
{
ParseState *pstate = context;
if (node == NULL)
return false;
if (!IsA(node, List))
{
if (check_functions_in_node(node, contains_user_functions_checker, NULL))
ereport(ERROR,
errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("generation expression uses user-defined function"),
errdetail("Virtual generated columns that make use of user-defined functions are not yet supported."),
parser_errposition(pstate, exprLocation(node)));
/*
* check_functions_in_node() doesn't check some node types (see
* comment there). We handle CoerceToDomain and MinMaxExpr by
* checking for built-in types. The other listed node types cannot
* call user-definable SQL-visible functions.
*
* We furthermore need this type check to handle built-in, immutable
* polymorphic functions such as array_eq().
*/
if (exprType(node) >= FirstUnpinnedObjectId)
ereport(ERROR,
errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("generation expression uses user-defined type"),
errdetail("Virtual generated columns that make use of user-defined types are not yet supported."),
parser_errposition(pstate, exprLocation(node)));
}
return expression_tree_walker(node, check_virtual_generated_security_walker, context);
}
static void
check_virtual_generated_security(ParseState *pstate, Node *node)
{
check_virtual_generated_security_walker(node, pstate);
}
/*
* Take a raw default and convert it to a cooked format ready for
* storage.
@ -3254,6 +3343,10 @@ cookDefault(ParseState *pstate,
ereport(ERROR,
(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
errmsg("generation expression is not immutable")));
/* Check security of expressions for virtual generated column */
if (attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
check_virtual_generated_security(pstate, expr);
}
else
{

2
src/include/catalog/catversion.h
View File

@ -57,6 +57,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 202506121
#define CATALOG_VERSION_NO 202506251
#endif

43
src/test/regress/expected/generated_virtual.out
View File

@ -553,15 +553,11 @@ CREATE TABLE gtest4 (
a int,
b double_int GENERATED ALWAYS AS ((a * 2, a * 3)) VIRTUAL
);
INSERT INTO gtest4 VALUES (1), (6);
SELECT * FROM gtest4;
a | b
---+---------
1 | (2,3)
6 | (12,18)
(2 rows)
DROP TABLE gtest4;
ERROR: virtual generated column "b" cannot have a user-defined type
DETAIL: Virtual generated columns that make use of user-defined types are not yet supported.
--INSERT INTO gtest4 VALUES (1), (6);
--SELECT * FROM gtest4;
--DROP TABLE gtest4;
DROP TYPE double_int;
-- using tableoid is allowed
CREATE TABLE gtest_tableoid (
@ -604,9 +600,13 @@ INSERT INTO gtest11 VALUES (1, 10), (2, 20);
GRANT SELECT (a, c) ON gtest11 TO regress_user11;
CREATE FUNCTION gf1(a int) RETURNS int AS $$ SELECT a * 3 $$ IMMUTABLE LANGUAGE SQL;
REVOKE ALL ON FUNCTION gf1(int) FROM PUBLIC;
CREATE TABLE gtest12 (a int PRIMARY KEY, b int, c int GENERATED ALWAYS AS (gf1(b)) VIRTUAL);
INSERT INTO gtest12 VALUES (1, 10), (2, 20);
GRANT SELECT (a, c), INSERT ON gtest12 TO regress_user11;
CREATE TABLE gtest12 (a int PRIMARY KEY, b int, c int GENERATED ALWAYS AS (gf1(b)) VIRTUAL); -- fails, user-defined function
ERROR: generation expression uses user-defined function
LINE 1: ...nt PRIMARY KEY, b int, c int GENERATED ALWAYS AS (gf1(b)) VI...
^
DETAIL: Virtual generated columns that make use of user-defined functions are not yet supported.
--INSERT INTO gtest12 VALUES (1, 10), (2, 20);
--GRANT SELECT (a, c), INSERT ON gtest12 TO regress_user11;
SET ROLE regress_user11;
SELECT a, b FROM gtest11; -- not allowed
ERROR: permission denied for table gtest11
@ -619,15 +619,12 @@ SELECT a, c FROM gtest11; -- allowed
SELECT gf1(10); -- not allowed
ERROR: permission denied for function gf1
INSERT INTO gtest12 VALUES (3, 30), (4, 40); -- allowed (does not actually invoke the function)
SELECT a, c FROM gtest12; -- currently not allowed because of function permissions, should arguably be allowed
ERROR: permission denied for function gf1
--INSERT INTO gtest12 VALUES (3, 30), (4, 40); -- allowed (does not actually invoke the function)
--SELECT a, c FROM gtest12; -- currently not allowed because of function permissions, should arguably be allowed
RESET ROLE;
DROP FUNCTION gf1(int); -- fail
ERROR: cannot drop function gf1(integer) because other objects depend on it
DETAIL: column c of table gtest12 depends on function gf1(integer)
HINT: Use DROP ... CASCADE to drop the dependent objects too.
DROP TABLE gtest11, gtest12;
--DROP FUNCTION gf1(int); -- fail
DROP TABLE gtest11;
--DROP TABLE gtest12;
DROP FUNCTION gf1(int);
DROP USER regress_user11;
-- check constraints
@ -811,6 +808,12 @@ CREATE TABLE gtest24nn (a int, b gtestdomainnn GENERATED ALWAYS AS (a * 2) VIRTU
ERROR: virtual generated column "b" cannot have a domain type
--INSERT INTO gtest24nn (a) VALUES (4); -- ok
--INSERT INTO gtest24nn (a) VALUES (NULL); -- error
-- using user-defined type not yet supported
CREATE TABLE gtest24xxx (a gtestdomain1, b gtestdomain1, c int GENERATED ALWAYS AS (greatest(a, b)) VIRTUAL); -- error
ERROR: generation expression uses user-defined type
LINE 1: ...main1, b gtestdomain1, c int GENERATED ALWAYS AS (greatest(a...
^
DETAIL: Virtual generated columns that make use of user-defined types are not yet supported.
-- typed tables (currently not supported)
CREATE TYPE gtest_type AS (f1 integer, f2 text, f3 bigint);
CREATE TABLE gtest28 OF gtest_type (f1 WITH OPTIONS GENERATED ALWAYS AS (f2 *2) VIRTUAL);

12
src/test/regress/expected/publication.out
View File

@ -524,10 +524,16 @@ Tables from schemas:
"testpub_rf_schema2"
-- fail - virtual generated column uses user-defined function
-- (Actually, this already fails at CREATE TABLE rather than at CREATE
-- PUBLICATION, but let's keep the test in case the former gets
-- relaxed sometime.)
CREATE TABLE testpub_rf_tbl6 (id int PRIMARY KEY, x int, y int GENERATED ALWAYS AS (x * testpub_rf_func2()) VIRTUAL);
ERROR: generation expression uses user-defined function
LINE 1: ...RIMARY KEY, x int, y int GENERATED ALWAYS AS (x * testpub_rf...
^
DETAIL: Virtual generated columns that make use of user-defined functions are not yet supported.
CREATE PUBLICATION testpub7 FOR TABLE testpub_rf_tbl6 WHERE (y > 100);
ERROR: invalid publication WHERE expression
DETAIL: User-defined or built-in mutable functions are not allowed.
ERROR: relation "testpub_rf_tbl6" does not exist
-- test that SET EXPRESSION is rejected, because it could affect a row filter
SET client_min_messages = 'ERROR';
CREATE TABLE testpub_rf_tbl7 (id int PRIMARY KEY, x int, y int GENERATED ALWAYS AS (x * 111) VIRTUAL);
@ -541,7 +547,7 @@ DROP TABLE testpub_rf_tbl2;
DROP TABLE testpub_rf_tbl3;
DROP TABLE testpub_rf_tbl4;
DROP TABLE testpub_rf_tbl5;
DROP TABLE testpub_rf_tbl6;
--DROP TABLE testpub_rf_tbl6;
DROP TABLE testpub_rf_schema1.testpub_rf_tbl5;
DROP TABLE testpub_rf_schema2.testpub_rf_tbl6;
DROP SCHEMA testpub_rf_schema1;

24
src/test/regress/sql/generated_virtual.sql
View File

@ -253,10 +253,10 @@ CREATE TABLE gtest4 (
a int,
b double_int GENERATED ALWAYS AS ((a * 2, a * 3)) VIRTUAL
);
INSERT INTO gtest4 VALUES (1), (6);
SELECT * FROM gtest4;
--INSERT INTO gtest4 VALUES (1), (6);
--SELECT * FROM gtest4;
DROP TABLE gtest4;
--DROP TABLE gtest4;
DROP TYPE double_int;
-- using tableoid is allowed
@ -290,20 +290,21 @@ GRANT SELECT (a, c) ON gtest11 TO regress_user11;
CREATE FUNCTION gf1(a int) RETURNS int AS $$ SELECT a * 3 $$ IMMUTABLE LANGUAGE SQL;
REVOKE ALL ON FUNCTION gf1(int) FROM PUBLIC;
CREATE TABLE gtest12 (a int PRIMARY KEY, b int, c int GENERATED ALWAYS AS (gf1(b)) VIRTUAL);
INSERT INTO gtest12 VALUES (1, 10), (2, 20);
GRANT SELECT (a, c), INSERT ON gtest12 TO regress_user11;
CREATE TABLE gtest12 (a int PRIMARY KEY, b int, c int GENERATED ALWAYS AS (gf1(b)) VIRTUAL); -- fails, user-defined function
--INSERT INTO gtest12 VALUES (1, 10), (2, 20);
--GRANT SELECT (a, c), INSERT ON gtest12 TO regress_user11;
SET ROLE regress_user11;
SELECT a, b FROM gtest11; -- not allowed
SELECT a, c FROM gtest11; -- allowed
SELECT gf1(10); -- not allowed
INSERT INTO gtest12 VALUES (3, 30), (4, 40); -- allowed (does not actually invoke the function)
SELECT a, c FROM gtest12; -- currently not allowed because of function permissions, should arguably be allowed
--INSERT INTO gtest12 VALUES (3, 30), (4, 40); -- allowed (does not actually invoke the function)
--SELECT a, c FROM gtest12; -- currently not allowed because of function permissions, should arguably be allowed
RESET ROLE;
DROP FUNCTION gf1(int); -- fail
DROP TABLE gtest11, gtest12;
--DROP FUNCTION gf1(int); -- fail
DROP TABLE gtest11;
--DROP TABLE gtest12;
DROP FUNCTION gf1(int);
DROP USER regress_user11;
@ -463,6 +464,9 @@ CREATE TABLE gtest24nn (a int, b gtestdomainnn GENERATED ALWAYS AS (a * 2) VIRTU
--INSERT INTO gtest24nn (a) VALUES (4); -- ok
--INSERT INTO gtest24nn (a) VALUES (NULL); -- error
-- using user-defined type not yet supported
CREATE TABLE gtest24xxx (a gtestdomain1, b gtestdomain1, c int GENERATED ALWAYS AS (greatest(a, b)) VIRTUAL); -- error
-- typed tables (currently not supported)
CREATE TYPE gtest_type AS (f1 integer, f2 text, f3 bigint);
CREATE TABLE gtest28 OF gtest_type (f1 WITH OPTIONS GENERATED ALWAYS AS (f2 *2) VIRTUAL);

5
src/test/regress/sql/publication.sql
View File

@ -262,6 +262,9 @@ ALTER PUBLICATION testpub6 SET TABLES IN SCHEMA testpub_rf_schema2, TABLE testpu
RESET client_min_messages;
\dRp+ testpub6
-- fail - virtual generated column uses user-defined function
-- (Actually, this already fails at CREATE TABLE rather than at CREATE
-- PUBLICATION, but let's keep the test in case the former gets
-- relaxed sometime.)
CREATE TABLE testpub_rf_tbl6 (id int PRIMARY KEY, x int, y int GENERATED ALWAYS AS (x * testpub_rf_func2()) VIRTUAL);
CREATE PUBLICATION testpub7 FOR TABLE testpub_rf_tbl6 WHERE (y > 100);
-- test that SET EXPRESSION is rejected, because it could affect a row filter
@ -276,7 +279,7 @@ DROP TABLE testpub_rf_tbl2;
DROP TABLE testpub_rf_tbl3;
DROP TABLE testpub_rf_tbl4;
DROP TABLE testpub_rf_tbl5;
DROP TABLE testpub_rf_tbl6;
--DROP TABLE testpub_rf_tbl6;
DROP TABLE testpub_rf_schema1.testpub_rf_tbl5;
DROP TABLE testpub_rf_schema2.testpub_rf_tbl6;
DROP SCHEMA testpub_rf_schema1;