Shibboleth Identity Provider Security Advisory 20130417a: Metadata Provider HTTPS Hostname Verification

[Brent Putman]

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Shibboleth Security Advisory [ 17 April 2013 ]

Identity Provider HTTPS Connections With HTTP-based Metadata Providers
Do Not Perform Hostname Verification
=======================================================================

The HTTPMetadataProvider and FileBackedHTTPMetadataProvider implementations
in the IdP make use of the Jakarta Commons HttpClient version 3.x. When
used with an HTTPS scheme, HttpClient by default does not perform
verification of the server hostname against the server's X.509 certificate.
The lack of hostname verification means that while the connection between
the IdP and HTTPS server is encrypted, the IdP has no way to verify
it's actually communicating with the appropriate HTTPS server hosting
the metadata.


Affected Versions
=================
Versions of the Identity Provider < 2.4.0

Note that if the remote metadata being retrieved with the provider is
signed using an XML signature by the metadata publisher or source, and
the provider is properly configured to validate this metadata signature,
then this issue has greatly reduced practical significance. In this case,
the use of HTTPS is unnecessary for authentication of the metadata source,
and any issues such as this concerning transport layer security, such as
certificate trust evaluation and hostname verification, are largely irrelevant.

Recommendations
===============
Upgrade to IdP 2.4.0 or greater, which configures an appropriate hostname
verifier for use with HttpClient, or publish and consume only signed
metadata along with appropriately-configured signature validation within
the metadata provider.

Note that in v2.4.0 and above, use of the provider configuration
option 'disregardSslCertificate' will disable hostname
verification as well as TLS certificate trust evaluation.


Credits
=======
Takeshi Nishimura, National Institute of Informatics, Japan

URL for this Security Advisory
http://shibboleth.net/community/advisories/secadv_20130417a.txt


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