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IBM DB2 Buffer Overflow Vulnerabilities (rec2xml, generate_distfile)
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SUMMARY
IBM's DB2 database server contains a procedure, generate_distfile. This
procedure suffers from a stack based buffer overflow vulnerability. IBM's
DB2 database server contains a function, rec2xml, used to format a string
in XML. This function suffers from a stack based buffer overflow
vulnerability.
DETAILS
Vulnerable Systems:
* DB2 8.1/7.x
Buffer Overflow Vulnerability in rec2xml:
By passing an overly long 3rd parameter to the rec2xml function a stack
based buffer can be overflowed, overwriting the saved return address on
the stack. This allows an attacker to control the flow of execution and
the opportunity to execute arbitrary code.
Buffer Overflow Vulnerability in generate_distfile:
The generate_distfile procedure is vulnerable to a buffer overflow
vulnerability. generate_distfile is implemented as a C function, exported
by db2dbappext.dll. It takes as its third parameter the name of a file.
This parameter can be up to 255 characters long. One of the sub functions
of generate_distfile takes the third parameter, the user supplied
filename, and appends it to the directory where DB2 has been installed. It
does this by creating a 264 byte buffer on the stack. The subfunction then
calls sqloInstancePath() to get the install path for DB2. This returns
C:\PROGRA~1\IBM\SQLLIB\DB2. \tmp\ is then appended to this.
After \tmp\ is appended the user supplied filename is appended using a
while loop that continues to copy data until a NULL terminator is found.
Because the DB2 install path (C:\PROGRA~1\IBM\SQLLIB\DB2\tmp\) takes up
some of the buffer, if the user has supplied a third parameter of 255
bytes the stack based buffer is overflowed.
However, once the buffer is overflowed, as well as overwriting the saved
return address, a pointer is also overwritten. This pointer points to a
buffer where the resulting full path should be copied to. This interrupts
a straight return address overwrite exploit; however it can still easily
be exploited in several ways. Due to the fact that the attacker "owns"
the pointer to where the path is copied to, they can write arbitrary data
to an arbitrary location allowing a full compromise. Once such method
would be to overwrite the pointer to the Windows UnhandledExceptionFilter
function; as access violations aren't handled, the UEF kicks in an as the
attacker controls the UEF the flow of execution can be redirected by the
attacker to arbitrary code.
* Note - whilst the discussion has used Windows paths *nix versions of
DB2 are also vulnerable.
Vendor Status:
IBM has written a patch and can be obtained with the latest FixPak.
<http://www-306.ibm.com/software/data/db2/udb/support/downloadv8.html>
DB2 v8.1
<http://www-306.ibm.com/software/data/db2/udb/support/downloadv7.html>
DB2 v7.x
ADDITIONAL INFORMATION
The information has been provided by <mailto:nisr@nextgenss.com>
NGSSoftware Insight Security Research.
The original article can be found at:
<http://www.ngssoftware.com/advisories/db223122004K.txt>
http://www.ngssoftware.com/advisories/db223122004K.txt and
<http://www.ngssoftware.com/advisories/db223122004L.txt>
http://www.ngssoftware.com/advisories/db223122004L.txt
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