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Hi Dmitry,

It's a timely email - about 1 hour ago, Andy merged a PR that was tinkering with the contents of this bucket (adding a signature to the DHE to mitigate a MiTM).

Unfortunately, OpenSSL 1.0.2h is fairly new compared to the minimum version Xrootd must support (RHEL6's 1.0.1e).

What if we introduce a new bucket type for this and the extension that Andy just merged?  How accepting is the dCache code of new bucket types?

Brian

> On Dec 7, 2018, at 2:58 PM, Dmitry O Litvintsev <[log in to unmask]> wrote:
> 
> Hi, 
> 
> dCache uses bouncycastle (BC) java crypto library.
> When we updated to BC version 1.5 we started to see occasional 
> (about 1 in 200) exceptions:
> 
> javax.crypto.BadPaddingException: pad block corrupted
> 
> when using xrdcp with gsi security against dCache xrootd server. 
> (secure handshake fails).
> 
> We have tracked down the problem to the padding the secret with leading 
> zeroes when converting number to to byte array that has been introduced 
> in BC based on RFC 2631 (2.1.2) specification and the use of  DH_compute_key in  XrdCryptosslCipher in xrdcp client.
> 
> We replaced  DH_compute_key with DH_compute_key_padded calls and do not  
> observe the issue anymore. 
> 
> DH_compute_key_padded appears in openssl in version 1.0.2h  [25 Aug 2016]:
> 
> """
>  *) New function DH_compute_key_padded() to compute a DH key and pad with
>     leading zeroes if needed: this complies with SP800-56A et al.
>     [Steve Henson]
> 
> """
> 
> Are there principal objections/considerations of not using DH_compute_key_padded in XrdCryptosslCipher? (beyond compatibility issue - obviously a client implemented w/ DH_compute_key_padded would not work against server implemented  w/ DH_compute_key). 
> 
> If turns out there are no objections we could think of some backward-compatible way 
> of introducing these functions. 
> 
> Thank you,
> Dmitry
> 
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