NGSSoftware Insight Security Research Advisory Name: IBM DB2 generate_distfile buffer overflow Systems Affected: DB2 8.1/7.x Severity: High risk Vendor URL: http://www.ibm.com/ Author: David Litchfield [ david at ngssoftware.com ] Relates to: http://www.nextgenss.com/advisories/db2-01.txt Date of Public Advisory: 23rd December 2004 Advisory number: #NISR2122004L Advisory URL: http://www.ngssoftware.com/advisories/db223122004L.txt Description *********** IBM's DB2 database server contains a procedure, generate_distfile. This procedure suffers from a stack based buffer overflow vulnerability. Details ******* 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 thrid 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 interupts 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. Fix Information *************** 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 NGSSQuirreL for DB2 (http://www.nextgenss.com/db2.htm) can be used to assess whether your DB2 server is vulnerable to this. About NGSSoftware ***************** NGSSoftware design, research and develop intelligent, advanced application security assessment scanners. Based in the United Kingdom, NGSSoftware have offices in the South of London and the East Coast of Scotland. NGSSoftware's sister company NGSConsulting, offers best of breed security consulting services, specialising in application, host and network security assessments. http://www.ngssoftware.com/ Telephone +44 208 401 0070 Fax +44 208 401 0076 enquiries@xxxxxxxxxxxxxxx
