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SECURITY: Two New Problems Found

Posted on May 2, 2005

We are currently preparing new releases that will correct these problems in freshly initdb'd installations. However, because these problems are really incorrect system catalog entries, updating to a new release will NOT by itself solve the problems in an existing installation. Instead, it is necessary for the database administrator to fix the catalog entries manually, as described below. We are releasing this advisory to encourage administrators of PostgreSQL installations to perform these fixes as soon as possible.

Character conversion vulnerability

The more severe of the two errors is that the functions that support client-to-server character set conversion can be called from SQL commands by unprivileged users, but these functions are not designed to be safe against malicious choices of argument values. This problem exists in PostgreSQL 7.3.* through 8.0.*. The recommended fix is to disable public EXECUTE access for these functions. This does not affect normal usage of the functions for character set conversion, but it will prevent misuse.

To accomplish this change, execute the following SQL command as a superuser:

``

UPDATE pg_proc SET proacl = '{=}'

WHERE pronamespace = 11 AND pronargs = 5

AND proargtypes[2] = 'cstring'::regtype;

In 7.3.* through 8.0.*, this should report having updated 90 rows. 7.4 and later will report a "WARNING: defaulting grantor to user ID 1" which can be ignored.

The above command must be carried out in *each* database of an installation, including template1, and ideally including template0 as well. If you do not fix the template databases then any subsequently created databases will contain the same vulnerability. template1 can be fixed in the same way as any other database, but fixing template0 requires additional steps. First, from any database issue

``

UPDATE pg_database SET datallowconn = true WHERE datname = 'template0';

Next connect to template0 and perform the pg_proc update. Finally, do

``

-- re-freeze template0:

VACUUM FREEZE;

-- and protect it against future alterations:

UPDATE pg_database SET datallowconn = false WHERE datname = 'template0';

tsearch2 vulnerability

The other error is that the contrib/tsearch2 module misdeclares several functions as returning type "internal" when they do not have any "internal" argument. This breaks the type safety of "internal" by allowing users to construct SQL commands that invoke other functions accepting "internal" arguments. The consequences of this have not been investigated in detail, but it is certainly at least possible to crash the backend.

This error affects PostgreSQL 7.4 and later, but only if you have installed the contrib/tsearch2 module. The recommended fix is to change the misdeclared functions so that they accept an "internal" argument and therefore cannot be called directly from SQL commands.

To do this, execute the following command as a superuser:

``

UPDATE pg_proc SET proargtypes[0] = 'internal'::regtype

WHERE oid IN (

'dex_init(text)'::regprocedure,

'snb_en_init(text)'::regprocedure,

'snb_ru_init(text)'::regprocedure,

'spell_init(text)'::regprocedure,

'syn_init(text)'::regprocedure

);

This should report 5 rows updated. (If it fails with a message like "function "dex_init(text)" does not exist", then either tsearch2 is not installed in this database, or you already did the update.)

You will need to do this in *each* database in which you have installed tsearch2, including template1. You need not worry about template0, however, since it will certainly not contain tsearch2.

If you frequently install tsearch2 in new databases, you will also want to modify the tsearch.sql script to declare these functions as taking type internal in the first place. (The script fix will be part of the upcoming releases, so you may be able to wait for those.)

On behalf of the PostgreSQL core committee, I'd like to apologize for any problems that may arise from these errors.

regards, tom lane

This post has been migrated from a previous version of the PostgreSQL website. We apologise for any formatting issues caused by the migration.


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