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Multiple Issues with MySQL User Defined Functions

AppSecInc Team SHATTER Security Advisory MYSQL05-V0003
http://www.appsecinc.com/resources/alerts/mysql/2005-003.html
August 08, 2005

Risk level: LOW

Credits: This vulnerability was discovered and researched by Reid
Borsuk of Application Security Inc.

Affected Versions:
ALL

Background:
User-defined functions in MySQL allow a user in the database to call
binary libraries on the operating system. Creating a user-defined
function requires insert privileges on the mysql.func table.

Details:
By using specially crafted CREATE FUNCTION requests it may be possible
for attackers to halt the system or execute remote code on some
systems. Two specific issues are detailed below.

1) If an attacker asks a Windows based MySQL server to load an invalid
library file the application will hang until a dialog box is
acknowledged on the server. By requesting one of the many non-library
files included in the PATH by default on Windows installations a
server will be effectively halted. This is due to the fact that the
Windows function LoadLibraryEx() will block when loading an invalid
library file with the following message:

"The application or DLL XXXX is not a valid Windows image. Please
check this against your installation diskette."

It should be noted that this is a Windows specific issue; other
operating systems are not likely to be affected.

An attacker attempting to exploit this issue must have insert
privileges on the mysql.func table. This is a high level of privilege
that is not normally given to untrusted users.

2) MySQL attempts to filter execution of arbitrary libraries by
requiring any UDF libraries to have either XXX_deinit() or XXX_init()
functions defined. This is intended to prevent an attacker from
including any libraries that were not specifically programmed to work
with MySQL. Unfortunately this function naming convention is
relatively common and default libraries may have these functions defined.

For instance, the "jpeg1x32.dll" and "jpeg2x32.dll" libraries,
included by default with Windows 2000 have these functions defined.
This allows an attacker to load the jpeg_cmp() function from
"jpeg1x32.dll" and the jpeg_decmp() function from "jpeg2x32.dll". When
either of these functions is called, the MySQL daemon will crash due
to improper argument passing.

Both the jpeg_cmp_init() and jpeg_decmp_init() functions assumes there
are 6 arguments waiting for it on the stack. One of these, Arg 6
(EBP+0x1C) is assumed to be a pointer to a memory location. Areas of
the memory past this pointer are later overwritten by other arguments
passed to this function. Due to the fact that Arg 4 (EBP+0x14) through
Arg 6 (EBP+0x1C) are not used prior to this call, it may be possible
to pollute the stack and overwrite arbitrary memory locations with
attacker supplied values.

Although this is a Windows specific example, it is possible that other
operating systems are affected.

Exploiting this vulnerability would require the ability to create
user-defined functions. This is not typically granted to untrusted
users, however given this vulnerability you should understand the
ramifications of granting the ability to create user-defined functions.

Workaround:
Restrict access to create user-defined functions.

Vendor Status:
Vendor was contacted and declined to produce a patch.

Fix:
None is available.

Links:
Application Security, Inc advisory:
http://www.appsecinc.com/resources/alerts/mysql/2005-003.html

- --
_____________________________________________
Application Security, Inc.
www.appsecinc.com
AppSecInc is the leading provider of database security solutions for
the enterprise. AppSecInc products proactively secure enterprise
applications at more than 300 organizations around the world by
discovering, assessing, and protecting the database against rapidly
changing security threats. By securing data at its source, we enable
organizations to more confidently extend their business with
customers, partners and suppliers. Our security experts, combined with
our strong support team, deliver up-to-date application safeguards
that minimize risk and eliminate its impact on business.

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