Re: AW: AW: Problem in Decryption

[Vishal Mahajan]

Dittmann,

I am in sync with you as far as encryption (element/element-content) is 
concerned. The point I was trying to make was that 
decryptElementContent() method does not remove all the child nodes of 
the element. It simply replaces the EncryptedData with the decrypted 
fragment. Also please note that the behavior of decryptElement() and 
decryptElementContent() methods is exactly the same.

Thanks,

Vishal

Dittmann Werner wrote:

Vishal,

that depeneds: if you encrypt/decrypt in Element mode
then it is correct. If you encrypt/decrypt in Content
mode then the methods are:
 encryptElementContent(...)
 decryptElementContent(...)
As you can see in encryptElementContent, it constructs a
DocumentFragment that contains _all_ child nodes
(including text nodes, other element nodes, PI nodes,
comment node,...) of an Element node if the _contents_
of that Element node shall be encrypted.
Element mode just takes the Element node and performs
encryption of that node. 

IMO this is as defined in XML-Enc specs.

Regards,
Werner
 

-----Ursprüngliche Nachricht-----
Von: Vishal Mahajan [mailto:[EMAIL PROTECTED] 
Gesendet: Mittwoch, 11. Februar 2004 12:33
An: [EMAIL PROTECTED]
Betreff: Re: AW: Problem in Decryption

Hi Dittmann,

Dittmann Werner wrote:

   

Vishal, Berin

during some encrypt/decrypt tests with signature:

This is mainly a problem for "content" mode encryption.
AFAIK, during encryption XMLCipher creates a document fragment
with the content, serializes and encrypts it. Decryption
is reverse. After decryption XMLCipher first removes
(or shall remove) all child-nodes of the element e.g. 
CreditCard, then puts in the nodes of the document 
fragment (effectivly restores the original content).

     

I looked at the code again and  don't think it's happening this way. 
Only a replace child operation is being done (all child nodes are not 
being removed). I am looking at the XMLCipher.decryptElement() method.

Please correct me if I am wrong.

Thanks,

Vishal

   

Thus, IMHO, there is no problem with Signature/Encrypt.
During our test we already did tests signature/encryption
in content mode.
Regards,
Werner


     

-----Ursprüngliche Nachricht-----
Von: Vishal Mahajan [mailto:[EMAIL PROTECTED] 
Gesendet: Mittwoch, 11. Februar 2004 08:35
An: [EMAIL PROTECTED]
Betreff: Re: Problem in Decryption

Hi Berin,

I agree with your reading of the spec. But, the spec does 
       

not prevent 
   

the encrypter from putting whitespaces between the tags of 
EncryptedData 
and its parent node. Also there are example encrypted 
documents like the 
following in the spec:

    <EncryptedData xmlns='http://www.w3.org/2001/04/xmlenc#'
     Type='http://www.w3.org/2001/04/xmlenc#Content'>
      <CipherData>
        <CipherValue>A23B45C56</CipherValue>
      </CipherData>
    </EncryptedData>
Other thing to note is that if the document was signed prior to 
encryption, the signature verification would fail. I think 
       

this is an 
   

important interop issue. What do you think?

Thanks,
Vishal
Berin Lautenbach wrote:

  

       

Vishal,

I ran accross this when I was doing the checks for the 
         

Merlin Interop
   

examples - which have white space prior to the EncryptedData 
    

         

node, even
  

       

when that node is of type "element content".  According to 
    

         

the spec (from
  

       

section 4.2) :
#####################################
"The decryptor SHOULD support the ability to replace the 
    

         

EncryptedData
  

       

element with the decrypted 'element' or element 'content' 
    

         

represented by
  

       

the UTF-8 encoded characters. The decryptor is NOT REQUIRED 
    

         

to perform
  

       

validation on the result of this replacement operation."
######################################
The key words for me were in the first sentance - "...replace the
EncryptedData element with the decrypted 'element' or element
'content'...".
There is no mention of the parent of the EncryptedData, or 
         

any of the
   

surrounding nodes, so my reading is that the libraries (both 
    

         

the C++ and
  

       

Java libraries have this behaviour) are doing the correct thing.
Happy to be corrected if someone can find something else 
         

in the spec!
   

Cheers,
  Berin


    

         

Hi All,

I think there is a problem in the decryption process of the 
      

           

XMLCipher
  

       

class. To put the problem across, here's my question:

If there is some whitespace between the tags of 
      

           

EncryptedData and its
  

       

parent (See the example below) and the Type attribute of the
EncryptedData corresponds to "element content", then the current
implementation simply replaces the EncryptedData with the 
           

decrypted
   

DocumentFragment. Shouldn't it first remove the existing contents
(whitespace, etc) of the parent node of EncryptedData and 
           

then do an
   

appendChild(DocumentFragment) on the parent?

<CreditCard Limit='5,000' Currency='USD'>
 <EncryptedData xmlns='http://www.w3.org/2001/04/xmlenc#'
  Type='http://www.w3.org/2001/04/xmlenc#Content'>
   <CipherData>
     <CipherValue>A23B45C56</CipherValue>
   </CipherData>
 </EncryptedData>
</CreditCard>
If this is accepted as a bug, I even have a patch for it.
      

           

Should I also
  

       

raise a bugzilla?

Thanks,
Vishal