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

[Pádraig Brady]

On 04/10/16 12:38, Pádraig Brady wrote:
> 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.

This would break scripts that used shortened --no-preserve for example,
though that's quite unlikely to be used.

Implementation is attached.

Pádraig

rm--n.patch
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