Security researchers have demonstrated a way to forge digital signatures that can fool the OpenSSL software used in many secure web servers and virtual private networks (VPN). The OpenSSL Project has issued patches to address the weakness, and is urging users to upgrade or install the patches.
The signature forgery technique was first demonstrated by Daniel Bleichenbacher, a cryptographer at Bell Labs, at the CRYPTO 2006 conference last month. While the forgery only works on specific keys (known as PKCS #1 v1.), these keys are used by some certificate authorities in SSL server certificates.
"All software that uses OpenSSL to verify X.509 certificates is potentially vulnerable, as well as any other use of PKCS #1 v1.5," OpenSSL said in its advisory. "This includes software that uses OpenSSL for SSL or TLS." OpenSSL versions up to 0.9.7j and 0.9.8b are affected.
OpenSSL is an open source toolkit implementing the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols, and is used in security products from numerous vendors.