Re: [boost] [review] Review of Nowide (Unicode) starts today

Subject: Re: [boost] [review] Review of Nowide (Unicode) starts today
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2017-06-12 22:52:47

On 12/06/2017 22:05, Peter Dimov via Boost wrote:
> Artyom Beilis wrote:
>> Deny of Service Attack Example:
>>
>>     - User creates a file with invalid UTF-16
>>     - System monitors the file system and adds it to the XML report in
>> WTF-8 format
>>     - The central server does not accept the XML since it fails UTF-8
>> validation
>>     - User does whatever he wants without monitoring
>>     - It removes the file
>>     - There were no reports generated during the period user needed
>> -DOS attack
> 
> I can't help but note that the same attack would work under Unix. The
> user can easily create a file with an invalid UTF-8 name. And, since the
> library doesn't enforce valid UTF-8 on POSIX (right?) it would pass
> through.

Also, running sanitisation on UTF sequences is laudable and all, but
what about the 80-90% of code which will never, ever feed strings from
untrusted remote parties to system APIs? Do they pay for the UTF
sequence validation too?

Like Peter and many of us, I have a personal "nowide" library too. It
simply wraps the *W() Win32 APIs consuming 16 bit characters with a call
to the NT kernel function for converting UTF-8 to UTF-16 which is
RtlUTF8ToUnicodeN().

It does nothing else fancy, it leaves it entirely up to the Windows
kernel what that conversion means. I'd suggest that the nowide library
ought to keep things similarly simple.

Niall

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