full-disclosure - Samsung DVR authentication bypass

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Message-ID: <CAP-1Xub3+MhVoqA_uJ2m0_toTMM_UyJAPHvODn27V0LOf8GyFg@mail.gmail.com>
Date: Tue, 20 Aug 2013 19:11:04 +0200
From: Andrea Fabrizi <andrea.fabrizi@...il.com>
To: bugtraq@...urityfocus.com, websecurity@...appsec.org, 
 full-disclosure@...ts.grok.org.uk, webappsec@...urityfocus.com
Subject: Samsung DVR authentication bypass

**************************************************************
Title: Samsung DVR authentication bypass
Version affected: firmware version <= 1.10
Vendor: Samsung - www.samsung-security.com
Discovered by: Andrea Fabrizi
Email: andrea.fabrizi@...il.com
Web: http://www.andreafabrizi.it
Twitter: @andreaf83
Status: unpatched
**************************************************************

Samsung provides a wide range of DVR products, all working with nearly
the same firmware. The firmware it's a Linux embedded system that
expose a web interface through the lighttpd webserver and CGI pages.

The authenticated session is tracked using two cookies, called DATA1
and DATA2, containing respectively the base64 encoded username and
password. So, the first advise for the developers is to don't put the
user credentials into the cookies!

Anyway, the critical vulnerability is that in most of the CGI, the
session check is made in a wrong way, that allows to access protected
pages simply putting an arbitrary cookie into the HTTP request. Yes,
that's all.

This vulnerability allows remote unauthenticated users to:
- Get/set/delete username/password of local users (/cgi-bin/setup_user)
- Get/set DVR/Camera general configuration
- Get info about the device/storage
- Get/set the NTP server
- Get/set many other settings

Vulnerables CGIs:
- /cgi-bin/camera_privacy_area
- /cgi-bin/dev_camera
- /cgi-bin/dev_devinfo
- /cgi-bin/dev_devinfo2
- /cgi-bin/dev_hddalarm
- /cgi-bin/dev_modechange
- /cgi-bin/dev_monitor
- /cgi-bin/dev_pos
- /cgi-bin/dev_ptz
- /cgi-bin/dev_remote
- /cgi-bin/dev_spotout
- /cgi-bin/event_alarmsched
- /cgi-bin/event_motion_area
- /cgi-bin/event_motiondetect
- /cgi-bin/event_sensordetect
- /cgi-bin/event_tamper
- /cgi-bin/event_vldetect
- /cgi-bin/net_callback
- /cgi-bin/net_connmode
- /cgi-bin/net_ddns
- /cgi-bin/net_event
- /cgi-bin/net_group
- /cgi-bin/net_imagetrans
- /cgi-bin/net_recipient
- /cgi-bin/net_server
- /cgi-bin/net_snmp
- /cgi-bin/net_transprotocol
- /cgi-bin/net_user
- /cgi-bin/rec_event
- /cgi-bin/rec_eventrecduration
- /cgi-bin/rec_normal
- /cgi-bin/rec_recopt
- /cgi-bin/rec_recsched
- /cgi-bin/restart_page
- /cgi-bin/setup_admin_setup
- /cgi-bin/setup_datetimelang
- /cgi-bin/setup_group
- /cgi-bin/setup_holiday
- /cgi-bin/setup_ntp
- /cgi-bin/setup_systeminfo
- /cgi-bin/setup_user
- /cgi-bin/setup_userpwd
- /cgi-bin/webviewer

PoC exploit to list device users and password:
http://www.andreafabrizi.it/download.php?file=samsung_dvr.py

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