D-Link DWR-956M Configuration File Format

[Chris-vdWest]

This is the router I received from Telkom for FLLA. I also have a DIR-825 G1 from Afrihost. For the 825 the config file was a .tar.gz which contained a JSON file, easy to open and edit. The 956-M saved a file default.cfg which looks like this when typed out:

I thought this was something like uuencoding, of which I knew years ago, had to Google creatively to find that name again. I then found out I can decode this file as base 64, dumped with hexdump -C it looks like this:



I noticed there is a 0x00 character between lines, so replaced them with end of line

cat default | tr "\000" "\n" | less, giving a more readable/editable file:


The question is, what are those bytes,
61 35 36 30 65 39 64 65 36 65 31 36 65 35 62 35 |a560e9de6e16e5b5 32 32 34 62 31 63 31 31 35 34 32 62 30 38 37 64 224b1c11542b087d0a FLSH at the start of the file. It ends on



The purpose of my question is just to be in control, to be able to edit and load back a config file. The other day I could not disable TR-069 on the DIR-825 and I did it by editing the JSON, put it back in a tar.gz and reload while disconnected from the WAN.

Any help would be highly appreciated!

Chris

 

[dabean]

It looks like an MD5 sum to me.

 

[Chris-vdWest]

Thanks dabean, good suggestion, I think there will be a checksum somewhere to prevent it from loading a damaged file. Question is where is it exactly, and which part of the file do I have to cut out to calculate the checksum. Can be the first 32 bytes of the file, which are 32 ascii characters used to represent 16 hex bytes, which is the size of MD5sum. When I have time, I will change one byte in the router (e.g. one letter of SSID name) and see if these 32 bytes change.