Re: TLS for localhost connections

[Dan Burkert]

A couple thoughts:

* You had to explicitly turn on the ADH and AECDH ciphers, right?  We
shouldn't be using those in any circumstances, but I don't think it would
change the results of your test.

* We've discussed adding checksums to the RPC system in the past, but
punted since we would get it 'for free' with TLS.  Perhaps we would want to
turn off checksums in the localhost scenario anyway, though?

* The solution of not wrapping the socket sounds reasonable.  We may need
to add a new RPC feature flag (e.g. TLS_LOCAL) so that we can be sure that
both sides recognize they are on a localhost connection.  Or perhaps this
isn't a problem and a connection can always be determined to be to the
localhost?

* The overhead of crypto hashes is highly dependent on the implementation.
For instance, some tests on my laptop (openssl speed md5 sha1 sha256 sha512
):

OpenSSL 0.9.8zg

The 'numbers' are in 1000s of bytes per second processed.
type 16 bytes 64 bytes256 bytes   1024 bytes   8192
bytes
md5  37815.63k   116197.14k   251336.60k   358376.77k
414424.95k
sha1 44766.06k   130830.68k   275829.53k   392799.78k
452215.48k
sha256   31386.52k73018.50k   132622.47k   161953.92k
175492.62k
sha512   20567.70k84586.04k   160368.90k   240929.09k
273687.68k

OpenSSL 1.0.2k

The 'numbers' are in 1000s of bytes per second processed.
type 16 bytes 64 bytes256 bytes   1024 bytes   8192
bytes
md5  55295.46k   158955.86k   360768.81k   510628.52k
580591.62k
sha1 66130.74k   188498.24k   443250.86k   685325.87k
824453.80k
sha256   69510.92k   153928.53k   275164.76k   349643.09k
379147.13k
sha512   44970.85k   175308.13k   304458.49k   448055.48k
524516.17k

sha1 is almost 50% faster, and sha512 is almost 100% faster.



On Thu, Feb 9, 2017 at 10:22 PM, Todd Lipcon  wrote:

> Hey folks,
>
> For those not following along, we're very close to the point where we'll be
> enabling TLS for all wire communication done by a Kudu cluster (at least
> when security features are enabled). One thing we've decided is important
> is to preserve good performance for applications like Spark and Impala
> which typically schedule tasks local to the data on the tablet servers, and
> we think that enabling TLS for these localhost connections will have an
> unacceptable performance hit.
>
> Our thinking was to continue to use TLS *authentication* to prevent MITM
> attacks (possible because we typically don't bind to low ports). But, we
> don't need TLS *encryption*.
>
> This is possible using the various TLS "NULL" ciphers -- we can have both
> the client and server notice that the remote peer is local and enable the
> NULL cipher suite. However, I did some research this evening and it looks
> like the NULL ciphers disable encryption but don't disable the MAC
> integrity portion of TLS. Best I can tell, there is no API to do so.
>
> I did some brief checks using openssl s_client and s_server on my laptop
> (openssl 1.0.2g, haswell), and got the following numbers for transferring
> 5GB:
>
> ADH-AES128-SHA
> Client: 42.2M cycles
> Server: 35.3M cycles
>
> AECDH-NULL-SHA: (closest NULL I could find to the above)
> Client: 36.2M cycles
> Server: 28.6M cycles
>
> no TLS at all (using netcat to a local TCP port):
> Client: 20.8M cycles
> Server: 10.0M cycles
>
> baseline: iperf -n 5000M localhost
> Client: 2.3M cycles
> Server: 1.8M cycles
> [not sure why this is so much faster than netcat - I guess because with
> netcat I was piping to /dev/null which still requires more syscalls?]
>
> (note that the client in all of these cases includes the 'dd' command to
> generate the data, which probably explains why it's 7-10M cycles more than
> the server in every case)
>
> To summarize, just disabling encryption has not much improvement, given
> that Intel chips now optimize AES. The checksumming itself adds more
> significant overhead than the encryption. This agrees with numbers I've
> seen around the web that crypto-strength checksums only go 1GB/sec or so
> max, typically much slower.
>
> Thinking about the best solution here, I think we should consider using TLS
> during negotiation, and then just completely dropping the TLS (i.e not
> wrapping the sockets in TlsSockets). I think this still gives us the
> protection against the localhost MITM (because the handshake would fail)
> and be trivially zero-overhead. Am I missing any big issues with this idea?
> Anyone got a better one?
>
> -Todd
> --
> Todd Lipcon
> Software Engineer, Cloudera
>

TLS for localhost connections

[Todd Lipcon]

Hey folks,

For those not following along, we're very close to the point where we'll be
enabling TLS for all wire communication done by a Kudu cluster (at least
when security features are enabled). One thing we've decided is important
is to preserve good performance for applications like Spark and Impala
which typically schedule tasks local to the data on the tablet servers, and
we think that enabling TLS for these localhost connections will have an
unacceptable performance hit.

Our thinking was to continue to use TLS *authentication* to prevent MITM
attacks (possible because we typically don't bind to low ports). But, we
don't need TLS *encryption*.

This is possible using the various TLS "NULL" ciphers -- we can have both
the client and server notice that the remote peer is local and enable the
NULL cipher suite. However, I did some research this evening and it looks
like the NULL ciphers disable encryption but don't disable the MAC
integrity portion of TLS. Best I can tell, there is no API to do so.

I did some brief checks using openssl s_client and s_server on my laptop
(openssl 1.0.2g, haswell), and got the following numbers for transferring
5GB:

ADH-AES128-SHA
Client: 42.2M cycles
Server: 35.3M cycles

AECDH-NULL-SHA: (closest NULL I could find to the above)
Client: 36.2M cycles
Server: 28.6M cycles

no TLS at all (using netcat to a local TCP port):
Client: 20.8M cycles
Server: 10.0M cycles

baseline: iperf -n 5000M localhost
Client: 2.3M cycles
Server: 1.8M cycles
[not sure why this is so much faster than netcat - I guess because with
netcat I was piping to /dev/null which still requires more syscalls?]

(note that the client in all of these cases includes the 'dd' command to
generate the data, which probably explains why it's 7-10M cycles more than
the server in every case)

To summarize, just disabling encryption has not much improvement, given
that Intel chips now optimize AES. The checksumming itself adds more
significant overhead than the encryption. This agrees with numbers I've
seen around the web that crypto-strength checksums only go 1GB/sec or so
max, typically much slower.

Thinking about the best solution here, I think we should consider using TLS
during negotiation, and then just completely dropping the TLS (i.e not
wrapping the sockets in TlsSockets). I think this still gives us the
protection against the localhost MITM (because the handshake would fail)
and be trivially zero-overhead. Am I missing any big issues with this idea?
Anyone got a better one?

-Todd
-- 
Todd Lipcon
Software Engineer, Cloudera

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