On 20/06/17 06:11, Michael Paquier wrote:
On Tue, Jun 6, 2017 at 3:40 PM, Michael Paquier
As far as I can see, there are a couple of things that I still need to
work on to make people happy:
- Rework the generic APIs for TLS finish and endpoint so as any
implementation can use channel binding without inducing any extra code
footprint to be-secure.c and fe-secure.c.
- Implement endpoint, as Alvaro is saying for JDBC that would be nicer.
- Have a couple of tests for channel binding to allow people to test
the feature easily. Those will be in src/test/ssl/. It would be nice
as well to be able to enforce the channel binding type on libpq-side,
which is useful at least for testing. So we are going to need an
environment variable for this purpose, and a connection parameter.
Okay, here we go. Attached is a set of four patches:
- 0001 is some refactoring for the SSL tests so as other test suite in
src/test/ssl can take advantage of the connection routines. There is
nothing fancy here.
- 0002 is the implementation of tls-unique as channel binding. This
has been largely reworked since last submission, I have found on the
way a couple of bugs and some correctness issues.
- 0003 is a patch to add as connection parameters saslname and
saslchannelbinding. With support of more SASL mechanisms (PG10 has
SCRAM-SHA-256, I am adding SCRAM-SHA-256-PLUS here), saslname can be
used to enforce on the client-side the value of the SASL mechanism
chosen. saslchannelbinding does the same for the channel binding name.
This is very useful for testing, and a set of tests are added in
src/test/ssl/ for tls-unique and the SASL mechanisms. The tests cover
many scenarios, like downgrade attacks for example.
- 0004 is the implementation of tls-server-end-point, as Alvaro has
asked. Per RFC 5929, the binding data needs to be a hash of the server
certificate. If the signature algorithm of the certificate is MD5 or
SHA-1, then SHA-256 is used. Other signature algos like SHA-384 or 512
are used to hash the data. The hashed data is then encoded in base64
and sent to the server for verification. Tests using saslchannelname
have been added as well. It took me a while to find out that
OBJ_find_sigid_algs(X509_get_signature_nid(X509*)) needs to be used to
find out the algorithm of a certificate with OpenSSL.
With the tests directly in the patch, things are easy to run. WIth
PG10 stabilization work, of course I don't expect much feedback :)
But this set of patches looks like the direction we want to go so as
JDBC and libpq users can take advantage of channel binding with SCRAM.
This is awesome, Michael.
In the coming weeks, and once my PR for pgjdbc has been added, I
will work towards another patch to implement channel binding. Should be
reasonably easy now, thanks to this.
Álvaro Hernández Tortosa
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