# Re: Anyone else trying to write code to work with a provider other than their own?

Sharon Liu (sharon.liu@eng.sun.com)
Tue, 11 May 1999 09:46:18 -0700 (PDT)

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    Message-Id: <199905111648.JAA03659@shorter.eng.sun.com>

    Date: Tue, 11 May 1999 09:46:18 -0700 (PDT)

    From: Sharon Liu <sharon.liu@eng.sun.com>

    Subject: Re: Anyone else trying to write code to work with a provider other than  their own?

    To: java-security@java.sun.com, DavidTaylor@forge.com.au

David and Bernard,

As the number of JCE providers grows, interoperability becomes more and
more important. The JCK test suits should be helpful to catch interoperability
problems. The JCE/JCA spec will also evolve to address new problems. Thanks
a lot for your feedback.

Just let you know that Jan is out of office now. When he comes back, he may
share more insights regarding the issues you brought up.

> How about PKCS8EncodedKeySpecs? The key spec type and the exact ASN.1
> encoded data (or whatever else) acceptable to it should be written in stone.
> Public keys too.

PKCS#8 defines a standard for encoding private keys. The exact ASN.1 encoding
format is defined in PKCS#8. But we probably should also have that information
in the javadoc for PKCS8EncodedKeySpec.

> I had to figure out what the Sun CertificateFactory was passing into my key
> factory when a certificate was being parsed - that info should have been in
> either the Certificate or RSAKeyFactory documentation.

Please note: by default, JDK doesn't have a RSAKeyFactory. Currently, the
Sun X509 CertificateFactory passes an X509EncodedKeySpec to your key factory.
Multiple compatible key specifications may exist for the same key (more
information in the javadoc for KeyFactory). For example, a RSA public key may
be specified using RSAPublicKeySpec or X509EncodedKeySpec. So your key
factory for RSA should be able to handle RSAPublicKeySpec and
X509EncodedKeySpec. Then you don't need to figure out what the Sun
CertificateFactory passes to your key factory. And your key factory would
be able to work with CertificateFactory from other vendors.

> One provider wanted "RSA/ECB/NoPadding" and another wanted "RSA/1/NoPadding"
> or "RSA/2/NoPadding" and used the 1 or 2 to set some internal state...

As it said in the javadoc for Cipher, one can pass the name of the
requested transformation to the getInstance() method in Cipher class.
A transformation is of the form: algorithm/mode/padding.

As Bernard has pointed out, the ECB,CBC,OFB modes are all
well-known standards. But we may add a list of standard names
for modes, etc. - just similar to the list of standard algorithm
names.

[From Bernard]
> One thing I think that would really improve things is a publication of
> the Java compatibility kit for the JCE.

I'll try to find out what we can do about this.

> An expanded "How-to" document with guide-lines on what parts of the
> API are important for cross-compatibility would be most helpful too.

Sounds like a good suggestion. Thanks!

Sharon

> X-Authentication-Warning: ballin.forge.com.au: mail set sender to
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> To: java-security@java.sun.com
> CC: Jan Luehe <luehe@laguna.eng.sun.com>
> Subject: Anyone else trying to write code to work with a provider other than
their own?
> Content-Transfer-Encoding: 7bit
>
> Firstly, thanks for the clarification on doFinal and CBC mode.
>
> Some more comments on trying to work with different JCEs and providers:
>
> I have written a provider and I've tested those from IAIK, DSTC and ABA. And
> they're all different :( Makes it impossible to write provider independent
code!
>
> The frustrations I've had with RSA in different providers:
>
> What exactly goes into an X509EncodedKeySpec? Can it be used for both public
and
> private keys? RSAPrivateKeySpec and RSAPrivateCrtKeySpec are both obvious
enough
> but some providers never bother to check if the Crt interface has been passed
in
> and always just return an RSAPrivateKey. How about PKCS8EncodedKeySpecs? The
key
> spec type and the exact ASN.1 encoded data (or whatever else) acceptable to it
> should be written in stone. Public keys too. I had to figure out what the Sun
> CertificateFactory was passing into my key factory when a certificate was
being
> parsed - that info should have been in either the Certificate or RSAKeyFactory
> documentation.
>
> I've had to modify other people's providers to get a common code base. The
one's
> I can't modify I just can't use. That's obviously not what you want for the
JCE!
> Some examples:
>
> * ABA RSAKeyFactory private key options
> * -------------------------------------
> * AsciiEncodedKeySpec (their own spec): either an RSAPrivateKey or
> RSAPrivateCrtKey depending on how much info in the spec
> * PKCS8EncodedKeySpec: RSAPrivateCrtKey
> * RSAPrivateCrtSpec: RSAPrivateCrtKey
> * RSAPrivateKeySpec: RSAPrivateKey
> *
> * DSTC RSAKeyFactory private key options
> * --------------------------------------
> * RSAPrivateCrtSpec: RSAPrivateKey (they don't check for this so it's
caught
> as an RSAPrivateKeySpec)
> * RSAPrivateKeySpec: RSAPrivateKey
> * PKCS8EncodedKeySpec: RSAPrivateCrtKey
> * X509EncodedKeySpec: RSAPrivateCrtKey
> *
> * FORGE RSAKeyFactory private key options
> * ---------------------------------------
> * RSAPrivateCrtSpec: RSAPrivateCrtKey
> * RSAPrivateKeySpec: RSAPrivateKey
> * EncodedKeySpec: RSAPrivateCrtKey
>
>
> Onto the RSA cipher itself:
>
> One provider wanted "RSA/ECB/NoPadding" and another wanted "RSA/1/NoPadding"
or
> "RSA/2/NoPadding" and used the 1 or 2 to set some internal state...
>
> Other providers have choked when you passed them a key from another key
factory -
> they'd only use their own key implementations! Related to this is the provider
> that requires RSAPrivateCrtKeys and won't work with RSAPrivateKeys.
>
>
>
> CBC/IV clarification:
>
> Clarifying the IV lifecycle and whether the input and output buffers can be
the
> same in an update/doFinal call in the specification seems necessary (not just
a
> FAQ somewhere).
>
>
> Secret key creation and cipher use:
>
> Provider secret key factories have different requirements. Some don't have
> algorithm specific secret key factories meaning you use SecretKeySpecs to pass
in
> raw keys. If they do have algorithm specific factories some of them require
you
> use the generateSecret method and some of them require the translateKey method
to
> be used.
>
> Should all "bulk" ciphers be forced to accept SecretKeySpec as their keys
during
> the init call? If I can't get a secret key factory I have no choice.
>
> So I've seen: some providers don't give secret key factories so you give the
> cipher a SecretKeySpec, but some providers won't accept that and require you
to
> use a secret key factory - although these ones want you to call different
methods
> with the secret key spec.
>
> To be fair, some of this seems to have been caused by implementation being
done
> against outdated versions of the spec. But most of it is because the
> specification isn't laying the law clearly enough.
>
> Another point of contention here is update/doFinal themselves. Sorry if you
know
> this but I'll give a simple overview of the SSL protocol, after the key
exchange
> has been completed:
>
> The block ciphers have been initialised in CBC mode with a secret key and IV
> agreed up during the key exchange. There is one cipher for reading and one for
> writing.
>
> A typical encrypted FTP session from the point of view of the client might go:
>
> A: -> USER username (sent using send cipher - write cipher IV is updated)
> (waits for response)
> A: <- PASSWORD required (read using read cipher - read cipher IV is updated)
> (waits for response)
> A: -> PASS password (sent using send cipher - write cipher IV is updated)
> A <- user logged in, waiting for command (read using read cipher - read cipher
IV
> is updated)
>
> So, there are pauses in the conversation both ways. The cipher cannot be
> reinitialised at any point as CBC mode is being used and the IV will be reset.
> All data is sent and received in mulitples of the block size - this is
required
> by SSL.
>
> I am being told to use doFinal between messages to ensure things work
correctly.
> Clearly that is not an option unless I keep track of the IV each step of the
way
> so I can initialise the cipher with it between messages. If I'm going to do
that,
> why would I bother using CBC mode? Should the above be possible without
> initialising the cipher betwee messages?
>
> This was brought up becuase I've been told some providers that sit on top of
> hardware will cause me grief by buffering data or whatever. This is another
area
> that could use some clarification or example in the specification.
>
>
> The current game plan seems to be for everyone to write their own provider and
> use that. I'm trying to write software that uses a JCE and whatever providers
the
> user wants and I'm having a hard time of it.
>
> I've spent a lot of time reworking our software to use the JCE and providers
and
> sold management on the benefits of not writing our own and now have some egg
on
> my face.
>
> I like the idea of the JCE and providers, and I'm very impressed that people
like
> ABA and DSTC have put their code out as they have (as have FORGE). Sadly, we
had
> to do too much interpretation of the spec ourselves and have all done it
> differently. I'm just pointing out the interoperability problems I've had so
you
> can make that spec more clear!
>
> --
>
> Regards,
> David Taylor
>
> =======================================================================
> David Taylor e-mail DavidTaylor@forge.com.au
> Software Engineer
> Forge Research Pty Ltd Phone +61 2 9209 4175
> PO Box 598, Alexandria Fax +61 2 9209 4172
> NSW 1435, Australia Web http://www.forge.com.au
> =======================================================================
>
>

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