I've been writing a number of bash scripts lately which get variables from a parameter or from a file. Some of the scripts run as root (using sudo)
This is on my notebook, so there aren't any other users to cause security problems in this situation, but ...
I'd like to be able to write a script I can release into the wild.
Probably, what this question does is make a strong case for not writing anything in bash where root/sudo is involved and input/parameters can't be trusted.
Other than locking everything down with sudoers, is there a way to read an arbitrary string into a bash program and parse it without allowing bash to expand it, potentially executing something along the way?
I don't see any solution for defending against a rogue parameter.
For a file, there might be a way, but it's not simple.
The string could be safely input to the script using read, but once it's in one or more variables, I can't see any method of accessing it that wouldn't involve potentially dangerous variable expansion.
I think it would be possible to read from a file using read -n 1 to get one character at a time in a loop into an array. That ought to defang just about anything, but it's a bit cumbersome having to reassemble everything character by character later.
I'm thinking of input like:
'$(rm -rf ./*)' or 'eval shutdown -h now'
or similar given as input which would run when a variable containing it was referenced. If the script was running as root, this could be a real problem!
Any ideas on how to address this other than, "Get a real programming language"?