Somebody asked me a few questions regarding the FRITZ!Boxes, and I think, it makes sense to answer them here on this blog.
No, I haven’t been digging into the FRITZ!Boxes “at levels well below the standard web UI”.
There is no SSH server, that comes with the FRITZ!Boxes.There are private web-sites, where you can find a ready-made dropbear SSH server. I got mine that way. And a gkrellmd as well.
There should be a way, to create yourself a development system targeted towards the “busybox” on your particular FRITZ!Box, but there are various slightly different processors being employed. I wasn’t successful there, when I tried. There is ip-phone-forum.de, where the FRITZ!Boxes get discussed a lot, but the preferred language there is German, although they would most certainly try to answer question, that people ask in English.But the threads are mostly in German. Be aware, that the main community for the FRITZ!Boxes is located in Germany and I guess also in Austria and in Switzlerland. You may also find a HOWTO, that explains how to set up a development environment.
But actually … – see above!
The “international” 7390 “speaks” English, but I don’t think, there a lot on frequent firmware updates for it. They only provide frequent firmware updates for their resp. battleship, and that is “certainly” not the *international* version of the 7390 but the “German” version — but how do I actually know? I don’t own an international 7390, I only brought one to Martinique and saw it working for like 2 weeks.
I assume the firewall on the FRITZ!Boxes is homegrown.
What tools and languages are available?
Well, basically they use the “busybox” software and what is built into that.
Nowadays there is also a “lua” interpreter provided. AVM seem to use that for CGI purposes.
perl etc. are regarded far to resource hungry.