Multiple vulnerabilities on D-Link DIR-645 devices
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[ADVISORY INFORMATION]
Title:    Multiple vulnerabilities on D-Link DIR-645 devices
Discovery date: 06/03/2013
Release date:   02/08/2013
Advisory URL:   http://roberto.greyhats.it/advisories/20130801-dlink-dir645.txt
Credits:        Roberto Paleari (roberto@greyhats.it, twitter: @rpaleari)

[AFFECTED PRODUCTS]
This security vulnerability affects the following products and firmware
versions:
   * D-Link DIR-645, 1.03B08
Other products and firmware versions could also be vulnerable, but they were
not checked.

[VULNERABILITY DETAILS]
This router model is affected by multiple security vulnerabilities. All of them
are exploitable by remote, unauthenticated attackers. Details are outlined in
the following, including some proof-of-concepts.

1. Buffer overflow on "post_login.xml"
   
   Invoking the "post_login.xml" server-side script, attackers can specify a
   "hash" password value that is used to authenticate the user. This hash value
   is eventually processed by the "/usr/sbin/widget" local binary. However, the
   latter copies the user-controlled hash into a statically-allocated buffer,
   allowing attackers to overwrite adjacent memory locations.

   As a proof-of-concept, the following URL allows attackers to control the
   return value saved on the stack (the vulnerability is triggered when
   executing "/usr/sbin/widget"):

     curl http://<target ip>/post_login.xml?hash=AAA...AAABBBB

   The value of the "hash" HTTP GET parameter consists in 292 occurrences of
   the 'A' character, followed by four occurrences of character 'B'. In our lab
   setup, characters 'B' overwrite the saved program counter (%ra).


2. Buffer overflow on "hedwig.cgi"

   Another buffer overflow affects the "hedwig.cgi" CGI script. Unauthenticated
   remote attackers can invoke this CGI with an overly-long cookie value that
   can overflow a program buffer and overwrite the saved program address.

   Proof-of-concept:
     curl -b uid=$(perl -e 'print "A"x1400;') -d 'test' http://<target ip>/hedwig.cgi


3. Buffer overflow on "authentication.cgi"

   The third buffer overflow vulnerability affects the "authentication.cgi" CGI
   script. This time the issue affects the HTTP POST paramter named
   "password". Again, this vulnerability can be abused to achieve remote code
   execution. As for all the previous issues, no authentication is required.

   Proof-of-concept:
     curl -b uid=test -d $(perl -e 'print "uid=test&password=asd" . "A"x2024;') http://<target ip>/authentication.cgi


4. Cross-site scripting on "bind.php"

   Proof-of-concept:
    curl "http://<target ip>/parentalcontrols/bind.php?deviceid=test'\"/><script>alert(1)</script><"


5. Cross-site scripting on "info.php"

   Proof-of-concept:
     curl "http://<target ip>/info.php?RESULT=testme\", msgArray); alert(1); //"


6. Cross-site scripting on "bsc_sms_send.php"

   Proof-of-concept:
     curl "http://<target ip>/bsc_sms_send.php?receiver=testme\"/><script>alert(1);</script><div"


[REMEDIATION]
D-Link has released an updated firmware version (1.04) that addresses this
issue. The firmware is already available on D-Link web site, at the following
URL:
http://www.dlink.com/us/en/home-solutions/connect/routers/dir-645-wireless-n-home-router-1000

[DISCLAIMER]
The author is not responsible for the misuse of the information provided in
this security advisory. The advisory is a service to the professional security
community. There are NO WARRANTIES with regard to this information. Any
application or distribution of this information constitutes acceptance AS IS,
at the user's own risk. This information is subject to change without notice.