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On 1/8/2019 8:21 PM, Viktor Dukhovni
wrote:
How do you plan to offer a built-in menu of algorithms that have not yet been added to OpenSSL?
I'm a bit confused as to why we would need to - if the underlying OpenSSL doesn't support a particular algorithm, then there's no need to disable it. The ideal would be that we ask OpenSSL what algorithms (and
protocol versions) it supports, and we export that list to the
user. However, practically we've found that we couldn't do that
even with TLS1.2, because (a) "openssl ciphers" (and the
underlying APIs) report PSK-* and other algorithms we don't intend
to support, and (b) the underlying OpenSSL includes support for
algorithms that our security policies don't allow us to support.
Also, there's the question of whether a particular algorithm or
protocol version is supported but disabled by default, or enabled
by default. For instance, today we support TLS 1.0, 1.1, and 1.2,
but 1.0 is disabled by default. That's a policy question that
OpenSSL can't help us with.
And if users are better off leaving the list alone, why encourage that with a fancy UI?
That's a good question, but at the same time we have a high-level UI policy that we don't offer "non-fancy" UIs.
However, as I think about it, I remember that we already need a softcoded list of algorithms, to avoid offering (e.g.) the PSK algorithms.In TLS 1.3, the handshake parameters are configured separately from the cipherlist. The use of (non-resumption) PSKs requires callbacks, so they're never enabled out of the box.It sounds like TLS 1.3 will need the same.Actually, it won't, nor did earlier versions, the ciphers were listed by "openssl ciphers -v", but they can't get activated without application support.
Right... we found that when we blindly asked for the cipher list,
it included ciphers that weren't actually operable because we
didn't have the associated application support. We had hoped to
be able to use relatively simple rules to determine the list of
allowable ciphers, but then found that we needed much more complex
rules than were desirable. -- Jordan Brown, Oracle ZFS Storage Appliance, Oracle Solaris |
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