openssl -- multiple vulnerabilities
OpenSSL project reports:
- Historically OpenSSL only ever generated DH parameters based on "safe"
primes. More recently (in version 1.0.2) support was provided for
generating X9.42 style parameter files such as those required for RFC 5114
support. The primes used in such files may not be "safe". Where an
application is using DH configured with parameters based on primes that are
not "safe" then an attacker could use this fact to find a peer's private
DH exponent. This attack requires that the attacker complete multiple
handshakes in which the peer uses the same private DH exponent. For example
this could be used to discover a TLS server's private DH exponent if it's
reusing the private DH exponent or it's using a static DH ciphersuite.
OpenSSL provides the option SSL_OP_SINGLE_DH_USE for ephemeral DH (DHE) in
TLS. It is not on by default. If the option is not set then the server
reuses the same private DH exponent for the life of the server process and
would be vulnerable to this attack. It is believed that many popular
applications do set this option and would therefore not be at risk.
- A malicious client can negotiate SSLv2 ciphers that have been disabled on
the server and complete SSLv2 handshakes even if all SSLv2 ciphers have
been disabled, provided that the SSLv2 protocol was not also disabled via
Copyright © 2003-2005 Jacques Vidrine and contributors.
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