Looking at my embedded Linux device. Connection refused to default ports with either ssh or telnet clinet, but not the ftp port. I have root pwd because the web front end of the device uses the true root password for administrative web page access. So am ftp'd in as root. Is it possible to configure and activate telnet or ssh with only ftp access so that I can remote in to a command line on this device? (In the mean time I'm going to poke around inside the case and see whether it has a serial tty console.)
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1Even if you change the configuration files, without the ability to restart the services, you won’t be able to access the server through SSH. Your best hope is that the administrator page itself allows you to enable SSH. Without more information I don’t anyone can answer this question– RamhoundJun 2, 2020 at 11:29
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It would be a massive security hole if you could do this.– KeltariJun 3, 2020 at 21:21
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I’m ftp’d in as root and was wondering whether if telnetd might be part of the image and there would be a static file I could edit so that the telnet service would be on instead of off at boot time. As I said, planning to pop the cover and possibly find a serial tty on a header. For my application I can just use a RPi and be done with it, but would like to bend this proprietary thing to my will so it does my bidding while still being the appliance that it is. Thanks all for your comments.– MAXdBJun 5, 2020 at 0:40
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2 Answers
It does not matter whether Linux is embedded or not. It doesn't even matter whether it is Linux or not. FTP does not let you run commands on the remote system.
You would also need to login to FTP as root to able to access the system config files, and hopefully that is disabled for appropriate security. Really, FTP should be disabled for everybody since the protocol is inherently insecure.
You say you have the root password so you should have full access to the device. Without details of which device you're using it is hard to say more about how to make this work. Somewhere in the web interface should be what you're looking for. Try searching through the docs or screens for "service", "init", or "systemd".
Another possibility is that if you can plug in a USB cable to your device you could get a terminal session going that way. https://learn.sparkfun.com/tutorials/terminal-basics/all might help you get this going.
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-1 because FTP (which is a protocol) does allow running commands on the remote system, using the SITE command in the protocol (some command line programs may use an internal command called QUOT or quote, to utilize the protocol's SITE command). The effect of SITE depends on the server; This is not considered a mandatory part of the protocol to implement, but the protocol does allow for it. I've seen a server that enables a search command, but a server could offer whatever services it wants (e.g., reboot).– TOOGAMSep 15, 2020 at 6:50
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The SITE subcommand is very rarely available or enabled, even in server environments where it might be useful. I doubt it is even implemented in most embedded applications, which is the context for this question.– chicksSep 15, 2020 at 19:31
Upon further searching, found that the device has a dev kit available that allows building an image with the changes/additions I need, and compressing and flashing the image over to the device.