Photo by Alex Chumak on Unsplash
Accessing root shell of my home router
2 min read
Vendor: FiberHome Telecommunication Technologies Co. Ltd
Software Version: 3.10L.02.A2pB022g.d20h
Bootloader (CFE) Version: before 1.0.37-5.12
Analyzing Attack Points
I had the following services enabled:
I had previously connected to FTP but the
ls commands never worked so I didn't bother diving into it more.
I had no experience w/ SNMP and TFTP so my only option was to try TELNET.
The password for FTP was the same as the default HTTP login one. What was interesting is that I had changed my HTTP login password, and that also changed the password of telnet login to the one I updated to, so my login to telnet was pretty straight forward.
It was a typical telnet instance that I had also seen way back when I first tinkered w/ telnet on the router. It had the common telnet commands along w/ some specific ones like testing LEDs on the router, but that was not much fun.
There was one command in special that I liked, the
ps command. I felt like the memory of the router was always on the edge, so I thought why not see what processes are running and if I can find something. The output was pretty normal, showing some
dhcpd, init etc but there were some lines that caught my attention
PID Uid VmSize Stat Command 37 admin 316 S -sh 12120 admin 280 S sh -c ps 12121 admin 272 R ps
So this meant some shell processes were running, and the last two ones were because of me issuing the
The heading caught my attention. I entered
ps as a command, and yes the table also says that
ps is a command. Now, if all these are commands, would
sh -c ps, or if I trim it down to just
sh be a valid command?
I tried that and was pleased to see the following output:
BusyBox v1.00 (2011.08.24-03:20+0000) Built-in shell (msh) Enter 'help' for a list of built-in commands. #
I was dropped into a shell, and issuing
ls now showed all the linux folders like
etc, var etc. I could now see all the files, files that had the values for configuring WAN, DHCP, NAS etc.
Seeing the busybox version, it seems the software was never updated after 2011 so it was bound to have more flaws, one of them being what I had just discovered.
Overall it was a good first step in me trying out security testing.