[OE-core] [PATCH v1] wic: Add --exclude-path option to rootfs source plugin.

[Kristian Amlie]

On 28/11/16 11:46, Ed Bartosh wrote:
> On Mon, Nov 28, 2016 at 08:07:05AM +0100, Kristian Amlie wrote:
>> On 25/11/16 17:33, Ed Bartosh wrote:
>>> On Fri, Nov 25, 2016 at 01:35:53PM +0100, Kristian Amlie wrote:
>>>> On 25/11/16 13:28, Maciej Borzęcki wrote:
>>>>> On Fri, Nov 25, 2016 at 11:15 AM, Kristian Amlie
>>>>>> +                # Disallow '..', because doing so could be quite disastrous
>>>>>> +                # (we will delete the directory).
>>>>>> +                remaining = path
>>>>>> +                while True:
>>>>>> +                    (head, tail) = os.path.split(remaining)
>>>>>> +                    if tail == '..':
>>>>>> +                        msger.error("'..' not allowed: --exclude-path=%s" % orig_path)
>>>>>> +                    elif head == "":
>>>>>> +                        break
>>>>>> +                    remaining = head
>>>>>
>>>>> Why not do this instead?
>>>>>
>>>>>     if '..' in path:
>>>>>         msger.error("'..' not allowed: --exclude-path=%s" % orig_path)
>>>>>
>>> would "'/..' in path" or something similar work?
>>
>> '/..my-file' is a valid file name, so no, it wouldn't work. I realize
>> that this would be uncommon, and it makes the check more complex, so I'm
>> ok with making it simpler if you want me to, but we have to trade
>> simplicity for correctness in that case.
>>
> OK, makes sense.
> 
> Would something like this work for you?
> 
>> mkdir -p /tmp/rootfs/bla/bla/bla/bla
>> python -c "import os;print os.path.realpath('/tmp/rootfs/bla/../bla/../bla/../bla/../').startswith('/tmp/rootfs/')"
> False
>> python -c "import os;print os.path.realpath('/tmp/rootfs/bla/../bla/../bla/bla/../').startswith('/tmp/rootfs/')"
> True

Ah, that's a good idea, makes it much simpler, and is still correct. I
will change to that.

-- 
Kristian