Introduction

My router is NetGear WNR512v3, cheap model from 2010’s; I had been worried about its security for 5 years until 2022, when I finally had time and experience to hack it.

Beginning

I started with research and found GitHub with firmware and README attached to it, which explains how to connect to the router. So, the plan was simple:

1. connect via telnet
2. execute programs
3. profit

But what if there is a… Stumbling block

Connecting and reviewing specs

That was easy. Just telnet 192.168.1.1 with entering user and password, which are using the same word “root”. After examining all directories, I find very interesting thing - my router uses UClibC as standard C language system library. That and many other things made process of finding information and compilers more complicated and time consuming, MIPS architecture didn’t help either.

Transferring data to router

Luckily, router version of busybox has tftp utility, that’s making process straightforward. To transfer data from and to the router I just need tftp server running on my PC.

Executing some programs

Finding working binaries

I tried very hard; found GitHubs with MIPS binaries. The result of running them is one - segmentation fault or SIGSEGV for short, which means they tryed to access memory that didn’t belong to them.

Finding working compilers

I found a list of compilers built for Linux and Windows. Firstly I tried Green Hills MIPS compiler, after 12 minutes of extracting 3GB archive, then compiling simple program, I realised - it doesn’t work for MIPS v1(program crashes with invalid instruction error). Then I tried some old Phillips compiler, it doesn’t work too. None of compilers from that list work.

Finally result

I looked up on UClibC website and found… Fully working MIPS v1 UClibC compiler! I thought “Finally!”, but then segmentation fault when ran compiled lua. I was so exhausted and burned out at the end that couldn’t finish my plan.

Conclusion

I spent more than 14 days to find working compiler… My router doesn’t allow outside access to admin panel and my ISP doesn’t portforward telnet protocol.

P.S: I throw that router in a trash a long time ago, maybe now I would pull something more cool with router I dunno.