bug#24604: Add '--no-preserve-roots' flag to 'rm' for better safety

[Pádraig Brady]

On 04/10/16 03:21, Mohammed Sadiq wrote:
> '--no-preserve-root' that can be used to ignore if the path is root when using
> the 'rm' command.
> 
> But as the most of the GNU commands accepts shortened flag as long as
> there is no ambiguity, this can be an issue too. So, 'rm --n' may have the
> same effect as 'rm --no-preserve-root'. There may be several users unaware
> of this feature which can cause several issues.
> 
> 1. A cracker may be able to trick a user to bring a system down using
> '--n' flag.
> 2. A folder/file name like '--n' as an argument to 'rm' command may
> try to delete
>     the whole files (in case a '/' too appears as an argument), and
> the user won't
>     find a reason why it happened.
> 
> One way to overcome this is set '--no-preserve-roots' too an alias for
> '--no-preserve-root'. This means that the user will have include the whole 
> flag
> to ignore root check (shortening will create an ambiguity).

An interesting idea.
The main focus of the --no-preserve-root option is to protect against
accidental insertion of a space with `rm -rf blah /` or `rm -rf $blah/`.
With malicious arguments though one can obfuscate using shell quoting,
and the recent ls quoting changes are more general protection against that.
In saying that I don't see any issue with this, and there is a slight
increase in protection, so I'd be 60:40 for making this change.

cheers,
Pádraig.