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GnuTLS: RSA Signature Forgery


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200609-15 / gnutls
Release Date September 26, 2006
Latest Revision September 26, 2006: 01
Impact normal
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
net-libs/gnutls < 1.4.4 >= 1.4.4 All supported architectures

Related bugreports: #147682


GnuTLS fails to handle excess data which could allow an attacker to forge a PKCS #1 v1.5 signature.

2.  Impact Information


GnuTLS is an implementation of SSL 3.0 and TLS 1.0.


verify.c fails to properly handle excess data in digestAlgorithm.parameters field while generating a hash when using an RSA key with exponent 3. RSA keys that use exponent 3 are commonplace.


Remote attackers could forge PKCS #1 v1.5 signatures that are signed with an RSA key, preventing GnuTLS from correctly verifying X.509 and other certificates that use PKCS.

3.  Resolution Information


There is no known workaround at this time.


All GnuTLS users should update both packages:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --update --ask --verbose ">=net-libs/gnutls-1.4.4"

4.  References


Page updated September 26, 2006

Summary: This is a Gentoo Linux Security Advisory

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