GnuTLS: RSA Signature Forgery

Background

GnuTLS is an implementation of SSL 3.0 and TLS 1.0.

Description

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.

Impact

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.

Workaround

There is no known workaround at this time.

Resolution

All GnuTLS users should update both packages:

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