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Fix has_column_privilege function corner case 

According to the comments, when an invalid or dropped column oid is passed
to has_column_privilege(), the intention has always been to return NULL.
However, when the caller had table level privilege the invalid/missing
column was never discovered, because table permissions were checked first.

Fix that by introducing extended versions of pg_attribute_acl(check|mask)
and pg_class_acl(check|mask) which take a new argument, is_missing. When
is_missing is NULL, the old behavior is preserved. But when is_missing is
passed by the caller, no ERROR is thrown for dropped or missing
columns/relations, and is_missing is flipped to true. This in turn allows
has_column_privilege to check for column privileges first, providing the
desired semantics.

Not backpatched since it is a user visible behavioral change with no previous
complaints, and the fix is a bit on the invasive side.

Author: Joe Conway
Reviewed-By: Tom Lane
Reported by: Ian Barwick
Discussion: https://postgr.es/m/flat/9b5f4311-157b-4164-7fe7-077b4fe8ed84%40joeconway.com
This commit is contained in:
Joe Conway 2021-03-31 13:55:25 -04:00
parent 86dc90056d
commit b12bd4869b
5 changed files with 143 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

116
src/backend/catalog/aclchk.c
View File

@ -3705,6 +3705,20 @@ pg_aclmask(ObjectType objtype, Oid table_oid, AttrNumber attnum, Oid roleid,
AclMode
pg_attribute_aclmask(Oid table_oid, AttrNumber attnum, Oid roleid,
AclMode mask, AclMaskHow how)
{
return pg_attribute_aclmask_ext(table_oid, attnum, roleid,
mask, how, NULL);
}
/*
* Exported routine for examining a user's privileges for a column
*
* Does the bulk of the work for pg_attribute_aclmask(), and allows other
* callers to avoid the missing attribute ERROR when is_missing is non-NULL.
*/
AclMode
pg_attribute_aclmask_ext(Oid table_oid, AttrNumber attnum, Oid roleid,
AclMode mask, AclMaskHow how, bool *is_missing)
{
AclMode result;
HeapTuple classTuple;
@ -3723,18 +3737,38 @@ pg_attribute_aclmask(Oid table_oid, AttrNumber attnum, Oid roleid,
ObjectIdGetDatum(table_oid),
Int16GetDatum(attnum));
if (!HeapTupleIsValid(attTuple))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("attribute %d of relation with OID %u does not exist",
attnum, table_oid)));
{
if (is_missing != NULL)
{
/* return "no privileges" instead of throwing an error */
*is_missing = true;
return 0;
}
else
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("attribute %d of relation with OID %u does not exist",
attnum, table_oid)));
}
attributeForm = (Form_pg_attribute) GETSTRUCT(attTuple);
/* Throw error on dropped columns, too */
/* Check dropped columns, too */
if (attributeForm->attisdropped)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("attribute %d of relation with OID %u does not exist",
attnum, table_oid)));
{
if (is_missing != NULL)
{
/* return "no privileges" instead of throwing an error */
*is_missing = true;
ReleaseSysCache(attTuple);
return 0;
}
else
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
errmsg("attribute %d of relation with OID %u does not exist",
attnum, table_oid)));
}
aclDatum = SysCacheGetAttr(ATTNUM, attTuple, Anum_pg_attribute_attacl,
&isNull);
@ -3790,6 +3824,19 @@ pg_attribute_aclmask(Oid table_oid, AttrNumber attnum, Oid roleid,
AclMode
pg_class_aclmask(Oid table_oid, Oid roleid,
AclMode mask, AclMaskHow how)
{
return pg_class_aclmask_ext(table_oid, roleid, mask, how, NULL);
}
/*
* Exported routine for examining a user's privileges for a table
*
* Does the bulk of the work for pg_class_aclmask(), and allows other
* callers to avoid the missing relation ERROR when is_missing is non-NULL.
*/
AclMode
pg_class_aclmask_ext(Oid table_oid, Oid roleid, AclMode mask,
AclMaskHow how, bool *is_missing)
{
AclMode result;
HeapTuple tuple;
@ -3804,10 +3851,20 @@ pg_class_aclmask(Oid table_oid, Oid roleid,
*/
tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(table_oid));
if (!HeapTupleIsValid(tuple))
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation with OID %u does not exist",
table_oid)));
{
if (is_missing != NULL)
{
/* return "no privileges" instead of throwing an error */
*is_missing = true;
return 0;
}
else
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation with OID %u does not exist",
table_oid)));
}
classForm = (Form_pg_class) GETSTRUCT(tuple);
/*
@ -4468,7 +4525,22 @@ AclResult
pg_attribute_aclcheck(Oid table_oid, AttrNumber attnum,
Oid roleid, AclMode mode)
{
if (pg_attribute_aclmask(table_oid, attnum, roleid, mode, ACLMASK_ANY) != 0)
return pg_attribute_aclcheck_ext(table_oid, attnum, roleid, mode, NULL);
}
/*
* Exported routine for checking a user's access privileges to a column
*
* Does the bulk of the work for pg_attribute_aclcheck(), and allows other
* callers to avoid the missing attribute ERROR when is_missing is non-NULL.
*/
AclResult
pg_attribute_aclcheck_ext(Oid table_oid, AttrNumber attnum,
Oid roleid, AclMode mode, bool *is_missing)
{
if (pg_attribute_aclmask_ext(table_oid, attnum, roleid, mode,
ACLMASK_ANY, is_missing) != 0)
return ACLCHECK_OK;
else
return ACLCHECK_NO_PRIV;
@ -4581,7 +4653,21 @@ pg_attribute_aclcheck_all(Oid table_oid, Oid roleid, AclMode mode,
AclResult
pg_class_aclcheck(Oid table_oid, Oid roleid, AclMode mode)
{
if (pg_class_aclmask(table_oid, roleid, mode, ACLMASK_ANY) != 0)
return pg_class_aclcheck_ext(table_oid, roleid, mode, NULL);
}
/*
* Exported routine for checking a user's access privileges to a table
*
* Does the bulk of the work for pg_class_aclcheck(), and allows other
* callers to avoid the missing relation ERROR when is_missing is non-NULL.
*/
AclResult
pg_class_aclcheck_ext(Oid table_oid, Oid roleid,
AclMode mode, bool *is_missing)
{
if (pg_class_aclmask_ext(table_oid, roleid, mode,
ACLMASK_ANY, is_missing) != 0)
return ACLCHECK_OK;
else
return ACLCHECK_NO_PRIV;

50
src/backend/utils/adt/acl.c
View File

@ -2444,8 +2444,7 @@ column_privilege_check(Oid tableoid, AttrNumber attnum,
Oid roleid, AclMode mode)
{
AclResult aclresult;
HeapTuple attTuple;
Form_pg_attribute attributeForm;
bool is_missing = false;
/*
* If convert_column_name failed, we can just return -1 immediately.
@ -2454,42 +2453,25 @@ column_privilege_check(Oid tableoid, AttrNumber attnum,
return -1;
/*
* First check if we have the privilege at the table level. We check
* existence of the pg_class row before risking calling pg_class_aclcheck.
* Note: it might seem there's a race condition against concurrent DROP,
* but really it's safe because there will be no syscache flush between
* here and there. So if we see the row in the syscache, so will
* pg_class_aclcheck.
* Check for column-level privileges first. This serves in
* part as a check on whether the column even exists, so we
* need to do it before checking table-level privilege.
*/
if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(tableoid)))
return -1;
aclresult = pg_class_aclcheck(tableoid, roleid, mode);
aclresult = pg_attribute_aclcheck_ext(tableoid, attnum, roleid,
mode, &is_missing);
if (aclresult == ACLCHECK_OK)
return true;
/*
* No table privilege, so try per-column privileges. Again, we have to
* check for dropped attribute first, and we rely on the syscache not to
* notice a concurrent drop before pg_attribute_aclcheck fetches the row.
*/
attTuple = SearchSysCache2(ATTNUM,
ObjectIdGetDatum(tableoid),
Int16GetDatum(attnum));
if (!HeapTupleIsValid(attTuple))
return 1;
else if (is_missing)
return -1;
attributeForm = (Form_pg_attribute) GETSTRUCT(attTuple);
if (attributeForm->attisdropped)
{
ReleaseSysCache(attTuple);
/* Next check if we have the privilege at the table level */
aclresult = pg_class_aclcheck_ext(tableoid, roleid, mode, &is_missing);
if (aclresult == ACLCHECK_OK)
return 1;
else if (is_missing)
return -1;
}
ReleaseSysCache(attTuple);
aclresult = pg_attribute_aclcheck(tableoid, attnum, roleid, mode);
return (aclresult == ACLCHECK_OK);
else
return 0;
}
/*

11
src/include/utils/acl.h
View File

@ -233,8 +233,14 @@ extern void RemoveRoleFromObjectACL(Oid roleid, Oid classid, Oid objid);
extern AclMode pg_attribute_aclmask(Oid table_oid, AttrNumber attnum,
Oid roleid, AclMode mask, AclMaskHow how);
extern AclMode pg_attribute_aclmask_ext(Oid table_oid, AttrNumber attnum,
Oid roleid, AclMode mask,
AclMaskHow how, bool *is_missing);
extern AclMode pg_class_aclmask(Oid table_oid, Oid roleid,
AclMode mask, AclMaskHow how);
extern AclMode pg_class_aclmask_ext(Oid table_oid, Oid roleid,
AclMode mask, AclMaskHow how,
bool *is_missing);
extern AclMode pg_database_aclmask(Oid db_oid, Oid roleid,
AclMode mask, AclMaskHow how);
extern AclMode pg_proc_aclmask(Oid proc_oid, Oid roleid,
@ -256,9 +262,14 @@ extern AclMode pg_type_aclmask(Oid type_oid, Oid roleid,
extern AclResult pg_attribute_aclcheck(Oid table_oid, AttrNumber attnum,
Oid roleid, AclMode mode);
extern AclResult pg_attribute_aclcheck_ext(Oid table_oid, AttrNumber attnum,
Oid roleid, AclMode mode,
bool *is_missing);
extern AclResult pg_attribute_aclcheck_all(Oid table_oid, Oid roleid,
AclMode mode, AclMaskHow how);
extern AclResult pg_class_aclcheck(Oid table_oid, Oid roleid, AclMode mode);
extern AclResult pg_class_aclcheck_ext(Oid table_oid, Oid roleid,
AclMode mode, bool *is_missing);
extern AclResult pg_database_aclcheck(Oid db_oid, Oid roleid, AclMode mode);
extern AclResult pg_proc_aclcheck(Oid proc_oid, Oid roleid, AclMode mode);
extern AclResult pg_language_aclcheck(Oid lang_oid, Oid roleid, AclMode mode);

14
src/test/regress/expected/privileges.out
View File

@ -1362,7 +1362,13 @@ select has_column_privilege('mytable','........pg.dropped.2........','select');
select has_column_privilege('mytable',2::int2,'select');
has_column_privilege
----------------------
t
(1 row)
select has_column_privilege('mytable',99::int2,'select');
has_column_privilege
----------------------
(1 row)
revoke select on table mytable from regress_priv_user3;
@ -1372,6 +1378,12 @@ select has_column_privilege('mytable',2::int2,'select');
(1 row)
select has_column_privilege('mytable',99::int2,'select');
has_column_privilege
----------------------
(1 row)
drop table mytable;
-- Grant options
SET SESSION AUTHORIZATION regress_priv_user1;

2
src/test/regress/sql/privileges.sql
View File

@ -836,8 +836,10 @@ alter table mytable drop column f2;
select has_column_privilege('mytable','f2','select');
select has_column_privilege('mytable','........pg.dropped.2........','select');
select has_column_privilege('mytable',2::int2,'select');
select has_column_privilege('mytable',99::int2,'select');
revoke select on table mytable from regress_priv_user3;
select has_column_privilege('mytable',2::int2,'select');
select has_column_privilege('mytable',99::int2,'select');
drop table mytable;
-- Grant options