Question about xml-signature algorithm used by Shibboleth IdP

[WULMS Alexander]

Hi,

Thanks for the extended reply. It answers my question.

I really appreciate your idea of being able to configure the signing algorithm on a relying-party specific basis in v3. It would allow to use the strongest signing algorithm supported by an SP.

Kind regards,
Alex


From: users-bounces at shibboleth.net [mailto:users-bounces at shibboleth.net] On Behalf Of Brent Putman
Sent: Friday, August 12, 2011 9:40 PM
To: users at shibboleth.net
Subject: Re: Question about xml-signature algorithm used by Shibboleth IdP



On 8/12/11 11:46 AM, WULMS Alexander wrote:
Hi,

I have noticed that by default, Shibboleth 2.3 uses SHA1 algorithm to calculate the hash-value for the xml-signature (to build the SAML response) and then encrypts the hash with RSA-2048.


Right.  Note however that the RSA signature crypto algorithm variant used is determined directly by your signing key, so if you want a different size (e.g. 4096) or wanted to use DSA instead, etc, you can can just change to use a different signing key (credential) in your config and the signing process will pick that up.





Are the algorithms used to calculate the signature configurable? I have not been able to find information about this in the documentation. I assume that the encryption algorithm is determined by the certificate used but I don't know about the hash algorithm.


Ask Chad said, it's somewhat low-level and we don't currently expose it as a config option.  It can be done with a custom Spring bean. If you really want to change the digest algorithm, and can write a little bit of Java, see this thread:

http://groups.google.com/group/shibboleth-users/browse_thread/thread/2cea3427ff41b994/689a15b2d072dbcf

That thread was talking about changing a different crypto property for XML encryption, not signature, but the idea is still the same.  The code that is pointed to is a little old, you might have to fix up the dependency versions in the POM, etc, but the Spring bean source should give you an idea as to what to do.  Just call:

secConfig.registerSignatureAlgorithmURI("RSA", SignatureConstants.ALGO_ID_SIGNATURE_RSA_SHA1)

replacing the constant with the algorithm ID that you want.

Note that that will be a global change to the IdP, for all relying parties.  We have discussed possibly having support for configuring this on a relying-party specific basis in v3.


HTH,
Brent



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