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Revision 34482

  • ext/openssl/ossl_ssl.c: Add SSL constants and allow to unset SSL option to prevent BEAST attack. See [Bug #5353].

In OpenSSL, OP_DONT_INSERT_EMPTY_FRAGMENTS is used to prevent
TLS-CBC-IV vulunerability described at
http://www.openssl.org/~bodo/tls-cbc.txt
It's known issue of TLSv1/SSLv3 but it attracts lots of attention
these days as BEAST attack. (CVE-2011-3389)

Until now ossl sets OP_ALL at SSLContext allocation and call
SSL_CTX_set_options at connection. SSL_CTX_set_options updates the
value by using |= so bits set by OP_ALL cannot be unset afterwards.

This commit changes to call SSL_CTX_set_options only 1 time for each
SSLContext. It sets the specified value if SSLContext#options= are
called and sets OP_ALL if not.

To help users to unset bits in OP_ALL, this commit also adds several
constant to SSL such as
OpenSSL::SSL::OP_DONT_INSERT_EMPTY_FRAGMENTS. These constants were
not exposed in Ruby because there's no way to unset bits in OP_ALL
before.

Following is an example to enable 0/n split for BEAST prevention.

ctx.options = OP_ALL & ~OP_DONT_INSERT_EMPTY_FRAGMENTS
  • test/openssl/test_ssl.rb: Test above option exists.