On 12-4-2018 16:51, Alex Peshkoff via Firebird-devel wrote:
On 04/12/18 16:51, Mark Rotteveel wrote:
On 12-4-2018 15:31, Alex Peshkoff via Firebird-devel wrote:
On 04/12/18 15:18, Mark Rotteveel wrote:
How does the protocol for the database encryption callback work? If
I look at the implementation in Firebird ADO.net, it just tries and
keep sending the same key in a while loop until Firebird responds
with something other than op_crypt_key_callback, which seems a bit
weird.
Looks like at the other side there is _VERY_ strange plugin.
Certainly having such behavior in the code is serious bug in ADO.net.
Technically the Firebird client code also uses a loop though.
Yes, but instead of sending same key it's passing data from server to
the passed by client interface and returns an answer from it to server.
In case of no intreface it returns empy answer, and be sure - server
knows that it means 'no key from client'.
But does this mean that there is only a single op_crypt_key_callback
from server to client, or can there actually be multiple (eg if there is
a more complex handshake?)?
Other question: how does this work with named keys? Is it still a
responsibility from the server-side plugin to communicate this in a
implementation specific way?
With right design of plugin this will not happen - interface should
make sure there is correct KeyHolder on the server before sending a
key. Certainly with an approach described by you in ADO key may get
lost. But when crypt is used in this way key may get lost in many
other scenarios.
And how would a client do that?
For example - KeyHolder has a private key of RSA pair, client software -
a public one. Before sending something over the wire it's encrypted with
public RSA, to decrypt it private part of pair is needed. Servers that
do not have right private RSA key can receive the message but it's a
garbage for them. Actual protocol should better be more complex - at
least with salt to avoid sending same packet for same key.
To me it sounds like parts of this should have been defined within the
Firebird implementation and protocol itself, it is now very easy to
write plugins that are vulnerable to replay attacks.
Mark
--
Mark Rotteveel
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