Disable SSLv2 default build, default negotiation and weak ciphers.

SSLv2 is by default disabled at build-time.  Builds that are not
configured with "enable-ssl2" will not support SSLv2.  Even if
"enable-ssl2" is used, users who want to negotiate SSLv2 via the
version-flexible SSLv23_method() will need to explicitly call either
of:

    SSL_CTX_clear_options(ctx, SSL_OP_NO_SSLv2);
or
    SSL_clear_options(ssl, SSL_OP_NO_SSLv2);

as appropriate.  Even if either of those is used, or the application
explicitly uses the version-specific SSLv2_method() or its client
or server variants, SSLv2 ciphers vulnerable to exhaustive search
key recovery have been removed.  Specifically, the SSLv2 40-bit
EXPORT ciphers, and SSLv2 56-bit DES are no longer available.

Mitigation for CVE-2016-0800

Reviewed-by: Emilia Käsper <emilia@openssl.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/Configure b/Configure
index 0a5ffac750..ea74c91537 100755
--- a/Configure
+++ b/Configure
@@ -724,8 +724,9 @@ my %disabled = ( # "what"         => "comment" [or special keyword "experimental
 		 "md2"            => "default",
 		 "rc5"            => "default",
 		 "rfc3779"	  => "default",
-		 "sctp"       => "default",
+		 "sctp"           => "default",
 		 "shared"         => "default",
+		 "ssl2"           => "default",
 		 "store"	  => "experimental",
 		 "unit-test"	  => "default",
 		 "zlib"           => "default",