[UNIX] Vulnerability in OpenCA Signature Verification

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To: list@securiteam.com
Date: 19 Jan 2004 12:56:17 +0200

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  Vulnerability in OpenCA Signature Verification
------------------------------------------------------------------------

SUMMARY

 <http://www.openca.org/> OpenCA Project is "an open organization aimed to
provide a framework for PKI studying and development of related projects".

A flaw in OpenCA could cause OpenCA to accept a signature from a
certificate if the certificate's chain is trusted byte chain directory of
OpenCA. This means that a certificate from another PKI can authorize
operations on the used PKI if the chain of the used signature certificate
can establish a trust relationship to the actually used PKI.

DETAILS

Vulnerable Systems:
 * OpenCA version 0.9.1.6 and prior

Immune Systems:
 * OpenCA version 0.9.1.7 and newer

CVE Information:
 <http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0004>
CAN-2004-0004

OpenCA has a library for common crypto operations - crypto-utils.lib. This
library includes a function to check a signature(libCheckSignature). The
function loads the used signature certificate from OpenCA's database and
finally ensures that the used signature certificate is identical with the
certificate in the database. The comparison of the certificate in the
database and the certificate of the signer was only performed on base of
the serial of the certificate. The design of the function can cause the
acceptance of a signature if the chain of the signature can create a trust
relationship to the chain directory of OpenCA and a certificate with a
matching serial exists in the used PKI.
A security risk is present for people who are using digital signatures to
secure approved requests or role based access control (RBAC).

Workaround:
The following patch can be applied to fix the vulnerability:

-----BEGIN PATCH-----
--- src/common/lib/functions/crypto-utils.lib 2004-01-15
12:10:45.000000000 +0100
+++ src/common/lib/functions/crypto-utils.lib.new 2004-01-15
12:10:06.000000000 +0100
@@ -201,7 +201,7 @@
                                                "__ERRVAL__",
$OpenCA::X509::errval);
                         return undef;
                 }

- last if ( $tmpCert->getSerial() eq $sigCert->getSerial()
);
+ last if ( $tmpCert->getPEM() eq $sigCert->getPEM() );
                 $sigCert = undef;
         }

-----END PATCH-----

Solution:
Upgrade to 0.9.1.7 and use newer snapshots than
openca-SNAP-20040114.tar.gz.

ADDITIONAL INFORMATION

The information has been provided by
<mailto:michael.bel@cms.hu-berlin.de> Michael Bell.

The original article can be found at:
<http://www.openca.org/news/CAN-2004-0004.txt>
http://www.openca.org/news/CAN-2004-0004.txt.

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