fetch extension - use local filename from content-dispositionheader

[Sean Bryant]

Matt Emmerton wrote:

>>Matt Emmerton wrote on Thu, Dec 29, 2005 at 10:09:03PM -0500:
>>    
>>
>>>>Sean Bryant wrote:
>>>>        
>>>>
>>>>>Barney Wolff wrote:
>>>>>
>>>>>          
>>>>>
>>>>>>On Thu, Dec 29, 2005 at 07:33:38PM -0500, Martin Cracauer wrote:
>>>>>>
>>>>>>
>>>>>>            
>>>>>>
>>>>>>>I'm a bit rusty, so please point me to style mistakes in the
>>>>>>>              
>>>>>>>
>appended
>  
>
>>>>>>>diff.
>>>>>>>The following diff implements a "-O" option to fetch(1), which,
>>>>>>>              
>>>>>>>
>when
>  
>
>>>>>>>set, will make fetch use a local filename supplied by the server
>>>>>>>              
>>>>>>>
>in a
>  
>
>>>>>>>Content-Disposition header.
>>>>>>>
>>>>>>>              
>>>>>>>
>>>>>>Have you considered the security implications of this option?
>>>>>>
>>>>>>
>>>>>>
>>>>>>            
>>>>>>
>>>>>Its just an extra option. I'm sure the details could be summed up in
>>>>>          
>>>>>
>the
>  
>
>>>>>man page.
>>>>>          
>>>>>
>>>>I think what Barney means is that if you run fetch(1) as root and the
>>>>server returns the filename as "/sbin/init" bad things will happen.
>>>>The data returned in Content-Disposition should be used with caution.
>>>>        
>>>>
>>>Would checking to see if the target file exists, and if so, abort the
>>>operation and display a warning be sufficient to address the security
>>>issues?  Of course, we'd need some kind of "force" option to override
>>>      
>>>
>this
>  
>
>>>for the foot-shooting folks, and -f is already taken, but that could
>>>      
>>>
>easily
>  
>
>>>be documented as a "limitation" of this option.
>>>      
>>>
>>I don't like it since it derives too much from standard behavior which
>>is to use a local name derived from the URL, even if it exists.
>>
>>Also, not overwriting files doesn't cut it for security, you could
>>e.g. create a nonexisting .rhosts or .ssh/authorized_keys or play
>>similar games.
>>
>>Forbidding "/" will set the security to the same level as the base
>>functionality.  I like that.
>>    
>>
>
>Agreed, although it still leaves open all the security loopholes that were
>mentioned, given the proper cwd and malicious intent on the server end.
>
>--
>Matt Emmerton
>
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>  
>
Well the programmer can only do so much, after that its up to the user.
Sanitize the filename before writing it. just escape troublesome 
characters.