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Shibboleth Service Provider Security Advisory [3 August 2018]

An updated version of the Shibboleth Service Provider software
is now available which includes an updated version of a third-party
dependency that corrects a denial of service vulnerability.

Platforms on which xml-security-c is an OS-supplied component,
such as Debian Linux, will need to ensure their vendor has supplied
an updated package to correct the issue.


Shibboleth SP software crashes on malformed KeyInfo content
===============================================================
SAML messages, assertions, and metadata all commonly make use of
the XML Signature KeyInfo construct, which expresses information
about keys and certificates used in signing or encrypting XML.

The Apache Santuario XML Security for C++ library contained code
paths at risk of dereferencing null pointers when processing
various kinds of malformed KeyInfo hints typically found in signed
or encrypted XML. The usual effect is a crash, and in the case of
the SP software, a crash in the shibd daemon, which prevents access
to protected resources until the daemon is restarted.

We will be conducting a more thorough review of both this code
base and our own for more issues of a similar nature, but for the
time being an immediate fix was made to the xml-security-c library
and an updated version of the SP software for Windows includes this
fixed version.

The version of xml-security-c containing the fix is V2.0.1.

As outlined further below, the older branch of the xml-security-c
library used by the SP V2 software is no longer maintained, and
so this represents the first major issue necessitating an upgrade
to V3 to correct. The bug *does* manifest itself in most or all
older versions.

Recommendations
===============
Ensure that V2.0.1 or later of the xml-security-c library is used.

For Windows installations, V3.0.2 of the Shibboleth SP is now
available[1][2] and contains this fix.

Older Windows installations (prior to V3.0) will NOT be binary
compatible with the xsec_2_0.dll library and must be upgraded
to V3.0.2

Linux installations relying on official RPM packages can upgrade to
the latest package versions to obtain the fix. If your system already
includes V2.0.0 of the xml-security-c library, then you MAY address
the issue by updating only that package. Shibboleth and OpenSAML
packages built against older versions, such as V1.7.x, will not
be compatible with the newer version.

Sites that have deployed by building their own copy of xml-security-c
should ensure that they upgrade to V2.0.1 of that package, or patch
older versions as desired.

Sites that rely on an OS-supplied version of xml-security-c will need
to contact their OS vendor for a fixed version, or manually build a
new or patched version.

Credits
=======
Thanks to Cerberus, Palo Alto Networks for reporting the issue to the
Apache Santuario project.

[1] https://shibboleth.net/downloads/service-provider/latest/win32/
[2] https://shibboleth.net/downloads/service-provider/latest/win64/

URL for this Security Advisory:
https://shibboleth.net/community/advisories/secadv_20180803.txt

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