Arbitrary filters through kitten?

[salmankhilji]

What if we allow kitten to run an arbitrary filter on the host machine? i.e., Run the given program on the host computer with these arguments and output the result to stdout.

Use Case #1

While running on embedded systems, such as Android, basic tools like awk and sed are often provided by busybox or toybox. These replacements are often limited and buggy. If we could run an arbitrary filter through kitten, we could do:

alias awk='kitten filter awk'
alias sed='kitten filter sed'

Now, we can run our local awk and sed on remote machines with all the bells and whistles.

Use Case #2

When running fzf locally, I like to specify a darker or lighter shade of the terminal background color. This is what I currently do:

color="$(kitty @ get-colors | sed -nr 's/^background\s+(.+)/\1/p' | xargs pastel darken 0.05 | pastel format)"

While this works locally on my machine, I would like to retain this capability within a script running on my Android device (or even SSH).

Luckily, pastel happens to provide pre-builts for arm so I could this on Android, but what if there wasn't a pre-built binary? Or what if I didn't want to have to install pastel on a remote host? The proposed feature in kitten would rid the need to have to manually cross compile such tools for embedded systems.

Another program that comes to mind is column. While this basic tool is available on most Linux systems, I have yet to find a pre-built for Android/arm.

Security Risks

Running an arbitrary program on our local machines from remote hosts is obviously a security risk. By running the following on the remote host:

kitten filter rm -rf ~/Documents

one could easily blow way important data on my local machine, so we may need to allow only a white-listed subset of filters that are specified in, say, kitty.conf. (GNU sed allows arbitrary program execution through the -e flag, so adding sed to the white-list would still be a security risk.)

Background

Initially, I thought of requesting a pastel like kitten that simply returned a subset of what pastel provides—primarily the lighten and darken commands. Then I thought that perhaps a more generic filter may allow other use cases.

[kovidgoyal]

I'm not a fan of this concept. It's got a huge security footprint and a is only useful on underpowered remote systems, which is a niche use case. For your specific usecase you can simply write a script that invokes the ssh kitten while setting a env var with the lighter and darker colors calculated on the local machine. Your remote script can use those env vars. Or you could even just have those env vars set in bashrc and have the ssh kitten forward them to the remote computer automatically.

[salmankhilji]

I'm not a fan of this concept. It's got a huge security footprint and a is only useful on underpowered remote systems, which is a niche use case. For your specific usecase you can simply write a script that invokes the ssh kitten while setting a env var with the lighter and darker colors calculated on the local machine. Your remote script can use those env vars. Or you could even just have those env vars set in bashrc and have the ssh kitten forward them to the remote computer automatically.

Yes, this is what I currently do:

setup_shell() {
  local background
  background="$(kitty @ get-colors | sed -nr 's/^background\s+(.+)/\1/p' | xargs pastel darken 0.05 | pastel format)"
  adb shell "
  print 'stty cols $(tput cols)\nstty rows $(tput lines)' >/data/.resize
  print 'COLOR_FZF=$background' >/data/.fzf-theme
  grep -qE '/data/\.mkshrc' /system/etc/mkshrc || print '\n[ -f /data/.mkshrc ] && . /data/.mkshrc' >>/system/etc/mkshrc
  "
}

The adb shell command runs the provided script on the Android device, which BTW has mksh, not bash.