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Publique! CMS SQL Injection Vulnerabilities



Publique! CMS SQL Injection Vulnerabilities
Publique! CMS SQL Injection Vulnerabilities



=====[ Tempest Security Intelligence - Advisory #01 / 2010 ]============


       SQL injection vulnerability in Publique! Framework
       --------------------------------------------------

  Authors:
Christophe de la Fuente 
           Gustavo Pimentel Bittencourt 


=====[ Table of Contents ]================================
 1. Overview
 2. Detailed description
 3. Additional context & Solutions
 4. References
 5. Thanks


=====[ Overview ]=====================================

 * System affected: Publique! version 2.3 (Other versions may be vulnerable)
 * Release date: 25 January 2010
 * Impact: Successful exploitation of this vulnerability may lead to remote
           server compromise due the ability to recover administrative
           credentials of Publique! management interface.


 Publique! is a Content Management System (CMS) for Web applications by F=E1brica
 Digital [1]. This framework claims to be designed for non-computer specialists,
 enabling them to update web site content directly from the internet.

 This product is largely used in Brazil by companies from various areas such as
 universities, government organizations, banks and independent product
vendors [2].

 A remotely exploitable vulnerability was found in the framework core component.
 Exploitation of this bug does not require authentication and will lead to
 remotely exposed potentially sensitive information from the Publique! database.
 Particularly, an attacker can extract usernames and passwords needed to
 authenticate to the administrative interface and gain full control of the web
 site and (depending on certain conditions) the server itself.


=====[ Detailed description ]===============================
 Publique! references each page with a specific ID ("sid") that the framework
 uses in most of URLs. For instance, to access the page referred by ID=1, the
 following URL is used:

 http://your_website.com/publique/cgi/cgilua.exe/sys/start.htm?sid=1

 It was found that Publique! does not validate properly the "sid" parameter
 value and causes this input to be interpreted as a SQL command instead of
 ordinary data.

 The following error is displayed when a simple quote is added after the
 original value (sid=1'):

 ------------------------------------------------------------------------------

 Content-type: text/html
 CGILua message
 Lua error on configuration (or extension)

   Error:       unexpected type to index table
   Active Stack:
     function _ERRORMESSAGE at C code
     function _initStart at //S/Publique/work/carregal/sys/reader/start.lua
     main of //S/Publique/work/carregal/sys/reader/start.lua
     function old_dofile at C code
     function dofile at
//S/Publique/work/carregal/cgi/cgilua/cgilua.conf/pos_env.lua
     main of string " write("") dofile(ReaderDir.."start.bin")
write("\n") det", 2
     function dostring at C code
     function: 0042E0D0 at
//S/Publique/work/carregal/cgi/cgilua/cgilua.conf/preprocess.lua
     function: 0042A8C8 at
//S/Publique/work/carregal/cgi/cgilua/cgilua.conf/preprocess.lua
     function: 0035CE60 at
//S/Publique/work/carregal/cgi/cgilua/cgilua.conf/cgilua.lua
     function: 0035D650 at
//S/Publique/work/carregal/cgi/cgilua/cgilua.conf/cgilua.lua
     main of //S/Publique/work/carregal/cgi/cgilua/cgilua.conf/cgilua.lua

 CGILua 3.2.1 CGI  =C2=A91995-99.

 ------------------------------------------------------------------------------

 After several tests, it appears that the framework is executing two SQL queries
 sequentially and the error is issued by the first query. It is unlikely that
 the bug could be exploited using conventional methods. However, it is possible
 to extract information from the database using Time-Based Blind SQL
Injection [3].

 Basically, this consists of using some time-taking SQL operations (e.g.
 the BENCHMARK() MySQL built-in function) that will delay server responses if
 the specific condition is satisfied. By monitoring the response time, it is
 possible to know if the conditional expression is True or False.

 Using this technique, it is possible to extract the usernames and passwords
 needed to authenticate into the Publique! management interface. Database
 information can be retrieved by testing the ASCII value of each character
 returned by the injected query.

 For example, the following payload may be used to extract the ASCII value of
 the first character returned by the query:

 http://your_website.com/publique/cgi/cgilua.exe/sys/start.htm?sid=1))+UNION+ALL
 +SELECT+IF((ASCII(SUBSTRING((SELECT+CONCAT(F_Login,':',F_Password)+FROM
 +Publique.T_Actor+LIMIT+1+OFFSET+0),1,1))>97),BENCHMARK(1000000,MD5('A')),0)%23

 This query first concatenates "F_Login" and "F_Password" columns of the
 internal table "T_Actor" and returns the first row (thanks to the "LIMIT 1
 OFFSET 0" statement). Then, it checks if the ASCII value of the first character
 returned is greater than 97 (the letter 'a'). If the condition is satisfied it
 will trigger the BENCHMARK function, causing a significant delay in the server
 response (approximately 4 seconds using our test lab). By repeating the query
 with different values to compare to, it is possible to retrieve the exact value
 of the first character. The complete string can be extracted by reproducing the
 process for each character.

 Although the password is encrypted, it is possible to discover it. After
 further investigation and reverse engineering the Lua pre-compiled binaries of
 Publique! framework, it appears that the encryption algorithm used is
 reversible (i.e. is not a hashing function).

 Basically, before storing passwords in the database, the framework encrypts
 them with two CGILUA [4] built-in functions: "crypt()" [5] and "encode()" [6].
 Since the key used by the encryption algorithm is hard-coded in Publique!
 binaries, it is possible to retrieve the plain password from the cypher by
 using the two following built-in functions: "decrypt()" and "decode()".

 These plain credentials could be used to log into the Publique! management
 interface, enabling the framework upload functionality, and eventually
 permitting an attacker to install malicious code on the remote server, for
 example.


=====[ Other contexts & Solutions ]===========================
 As usual [7], we contacted the vendor. After 45 days waiting, F=E1brica Digital
 did not provide us a public URL to a fix which addresses this problem to attach
 in this publication.


=====[ Thanks ]=======================================
 - Tempest Security Intelligence [8] - Tempest Pentest Team
 - Evandro Curvelo Hora 


=====[ References ]=====================================
 [1] http://www.fabricadigital.com.br/
 [2] http://www.fabricadigital.com.br/publique/cgi/cgilua.exe/sys/start.htm?sid=34&UserActiveTemplate=fabrica2007
 [3] http://www.owasp.org/index.php/Blind_SQL_Injection
 [4] https://web.tecgraf.puc-rio.br/cgilua/index2.html
 [5] https://web.tecgraf.puc-rio.br/cgilua/secao5.html#crypt
 [6] https://web.tecgraf.puc-rio.br/cgilua/secao5.html#encode
 [7] http://www.cert.org/kb/vul_disclosure.html
 [8] http://www.tempest.com.br/


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