JCA design for RFC 7748

[Michael StJohns]

On 8/16/2017 12:31 PM, Xuelei Fan wrote:
> On 8/16/2017 8:18 AM, Adam Petcher wrote:
>>>>
>>>> I don't worry about this issue any more.  At present, each 
>>>> java.security.Key has three characters (see the API Java doc):
>>>> . an algorithm
>>>> . an encoded form
>>>> . a format
>>>>
>>>> The format could be "X.509", and could be "RAW" (like 
>>>> ByteArrayValue.getValue()).  I would suggest have the named curve 
>>>> in the algorithm characters, and use "RAW" as the encode format.
>>>> If X.509 encoding is required, KeyFactory.getKeySpec​() could do it.
>>> Um... I think that doesn't make a lot of sense.  The default 
>>> contract for public keys is X.509 and the default for private keys 
>>> is PKCS#8. Almost all uses of the encoded formats are related to 
>>> PKIX related functions.   (See for info the javadoc for PublicKey).
>>
>> I'm concerned about this, too. Ideally, we want PKI code to handle 
>> these new keys without modification. The javadoc wording makes it a 
>> little unclear whether public keys *must* use X.509 encoding, but 
>> using other encodings for public keys would probably be surprising.
> I have not had a conclusion, but I was wondering if almost all uses of 
> the encoded formats are related to PKIX related functions, whether it 
> is still a priority to support encoding other than X.509?
>
> So far, I think our proposal works.  The concern is mainly about how 
> to *simplify* the transaction between two formats (Raw, PKIX, XML and 
> JSON) in applications.  I don't worry about the transaction too much 
> as it is doable with our current proposal, but just not as 
> straightforward as exposing the RAW public key.
>
> If we want to simplify the transaction, I see your concerns of my 
> proposal above.  We may keep using "X.509" for default, and define a 
> new key spec.  The encoded form for X.509 is as:
>
>      SubjectPublicKeyInfo ::= SEQUENCE {
>          algorithm AlgorithmIdentifier,
>          subjectPublicKey BIT STRING
>      }
>
> The new encoded form could be just the subjectPublicKey field in the 
> SubjectPublicKeyInfo above.
>
> However, I'm not very sure of how common the transaction is required 
> and whether it is beyond the threshold to be a public API in JRE.

There's a proposed defined format for PKIX keys on the new curves - the 
IETF CURDLE working group is working through that.  JCA should use that 
and not invent something new.


>
>
> >
> > The new keys remain tagged as ECKeys.  Old code won't notice (because
> > old code is using old curves).  New code (new providers) will have to
> > pay attention to EllipticCurve and ECField information if its handling
> > both types of curves.  As is the case now, no provider need support
> > every curve or even every field type.
> >
> My concern is about the case to use old provider and new provider all 
> together at the same time.  JDK is a multiple providers coexisting 
> environment.  We cannot grant that old code only uses old curves (old 
> providers) and new code only uses new curves (new providers).

I did see this email and commented on it.  I think you're still missing 
the point that not every provider implements (or is required to 
implement) every curve.  And in fact I argued that it was somewhat 
stupid that the underlying C code in the SunEC provider was at odds with 
the code in the SunEC java side with respect to known curves and how 
they were handled. (Subject was RFR 8182999: SunEC throws 
ProviderException on invalid curves).


Consider - currently if I don't specify a provider, and there are two 
providers, and the lower priority provider implements "curveFoobar" but 
the higher priority provider does not, and I use an ECGenParameterSpec 
of "curveFoobar" to try and generate a key, I get a failure because I 
got the higher priority provider (which gets selected because JCA 
doesn't yet know that I want curveFoobar ) that doesn't do that curve.  
I need to specify the same provider throughout the entire process to 
make sure things work as expected AND I need to specify the provider 
that implements the curve I want.


This is the same for ANY current publicly known curve - different 
providers may implement all some or none of them.  So extending this 
model for the curve25519 stuff isn't going to be any different old 
provider and new provider wise than is currently the case.   If you want 
the new curves, you have to specify the new providers.  If the new and 
old providers don't implement the same curves, you may need to deal with 
two different providers simultaneously - and that's not something that 
just happens.

I don't think your concerns are valid.  I may still be missing something 
here - but would ask for a real-world example that actually shows breakage.

Treat these simply as new curves and let's move forward with very 
minimal changes to the public API.


Mike





>
> There is an example in my August 10 reply:
>
> http://mail.openjdk.java.net/pipermail/security-dev/2017-August/016199.html 
>
>
> Xuelei