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List:       botan-devel
Subject:    [Botan-devel] AES, CBC with ISO10126 padding handling
From:       daniel () parker-software ! com (Daniel Tallentire)
Date:       2008-12-08 16:49:53
Message-ID: 116DF9BC608B1D4DA08AABD98B7709E748F3C19D () PSLDC ! parkersoft ! co ! uk
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Hi Jack,


Awesome - thanks, works perfectly!


Is there any documentation on which objects I should / shouldn't delete? It looks \
like the Pipe destructor will destroy the Filter etc that are contained inside it?

Thanks,

Daniel


-----Original Message-----
From: botan-devel-bounces@randombit.net [mailto:botan-devel-bounces at randombit.net] \
                On Behalf Of Jack Lloyd
Sent: 06 December 2008 13:27
To: Botan development list
Subject: Re: [Botan-devel] AES, CBC with ISO10126 padding handling

On Sat, Dec 06, 2008 at 11:49:24AM +0000, Daniel Tallentire wrote:

Hi Daniel,

> I have written a small class to handle this incoming padding (I don't 
> need to generate the padding, only to handle it - the current
> PKCS7 would be fine if it didn't check that the remaining bytes were 
> set to the same digit), and I can easily recompile Botan with this 
> modification in place - however, I was wondering if it is possible to 
> add a padding method without compiling Botan?  The existing library 
> for Ubuntu etc work straight away for me, and this is the only change 
> I need to make.

Yes. However it is somewhat the case of good/bad/ugly. In 1.6 (the version shipped \
with most distros) you need to create and register a new engine, which will then \
provide this padding scheme without having to modify the lib itself. I've attached an \
example.

This engine stuff works with 1.6, but not with 1.8 (which is the new stable version \
being released next Monday). However, that is ultimately good because instead, in 1.8 \
you can simply say  new CBC_Decryption(new AES_128, new ISO10126_Padding) and avoid \
the mess.

[...]
> If it isn't possible to do it without compiling botan, what is the best place to \
> override?   
> get_bc_pad in algolist.cpp would seem to be the most sensible, just 
> adding the line HANDLE_TYPE_NO_ARGS("ISO10126", ISO10126_Padding);
> 
> would do the trick?

This would do it as well.

-Jack


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