On 5.3.2014 16:02, Petr Spacek wrote:
On 5.3.2014 14:21, Simo Sorce wrote:
On Wed, 2014-03-05 at 10:53 +0100, Petr Spacek wrote:
On 5.3.2014 08:48, Jan Cholasta wrote:
On 5.3.2014 05:10, Simo Sorce wrote:
On Tue, 2014-03-04 at 18:32 -0500, Dmitri Pal wrote:
Remote means that there is a PKCS#11 library that can be loaded
into a
process and would remotely connect to a central server via
LDAP/REST/whatever. My point is that library should be light weight
and always talk to a local service like SSSD rather than have a
remote
interface. In this case SSSD on the server can talk to the vault or
IPA LDAP directly and all consumers would use PKCS#11 interface
exposed by SSSD

Something like this...

Yes this is the setting we are discussing, the actual specific
discussion is how SSSD gets the information.

Honza proposed to use a PKCS#11-like schema to store data in LDAP
given
DNS will need something similar, however the more we wandered into the
discussion the more I got convinced the Vault is probably a better
place
to store this material than the LDAP tree itself at least for prvate
keys.

I only proposed something that would work for my needs (i.e. storing
certificates and associated trust policy) and would be ready for
4.0. Can you
say the same thing about the vault?
I agree with Honza. I think that proposed LDAP schema is perfectly
fits the
purpose *for public* information like certificates and public keys.

And I agree with you and Honza as well that the proposal is ok for
*public* information.

For public key material only though I am not sure a pkcs#11 schema
will
necessarily be useful. It might, but we do not use it for public SSH
keys. And we also already have schema for public User or Servers X509
certs.

Support for SSH public keys was implemented like 2 years ago, way
before any
talk about the vault or PKCS#11 even started. As for certs, the
proposed
schema works on top of RFC 4523, which is the cert schema you mention.


We need to define something for DNS public keys, but they are already
published in DNS Records too if I am not wrong, would that be
sufficient
as a storage for the public part ? I am assuming the private keys are
No, we need full PKCS#11 for OpenDNSSEC at least.

Well, you need a pkcs#11 library interface, the backing store could be
anything,
but I do see the advantage of using a common schema so that SSSD can
retrieve data
to present through that interface in a simplified and consistent way.

Note that PKCS#11 in SSSD will give us generic mechanism for process/key
separation (it is practically the same thing GSS-Proxy, just general
purpose).
This comes 'for free' if we implement PKCS#11 so please stop
searching for
workarounds :-)

I am not looking for workarounds for the interface between SSSD and
consuming libraries. I am trying to evaluate what we could use this
schema for before jumping into it.

stored in the Vault and they can be files in the format used by bind ?
BIND files are very hackish and we need to do PKCS#11->BIND files
conversion
anyway because OpenDNSSEC supports only PKCS#11 and nothing else.

I plan to use PKCS#11 directly from BIND so we can drop the format
conversion
code and rely on pure PKCS#11 instead of bunch of hacks scripts.

Ok.

So the information would be scattered in different places, using
different
formats and accessed using different protocols? I'm fine with that,
but it is
way beyond my original idea, so please let whoever is in charge of
the vault
implement the PKCS#11 module themselves.

Honza, clearly if something different is proposed work will be split
between those that need to implement it in various ways, this will
simply require to separate the pkcs#11 module into 2 parts, a 'feeder'
that implements the pkcs#11 interface and a pluggable 'gatherer' that
implements retrieval for specific stuff. No worries there.

- IMHO public information should be stored in LDAP schema as proposed.
- I agree that Vault is the right choice to store secrets.
- I propose to combine these two: Store public information in LDAP
and store
private keys in PKCS#8 blob as a secret in Vault.
- This LDAP+Vault combo can be accessible over PKCS#11 interface.
- Note that this will work even without vault if you want to store
public
information only (like CA certs and NSS trust objects).

Works for me.

The only problem is that we need to use REST API from SSSD. Plain
LDAP is
already implemented in SSSD so it requires less code. I guess that we
will
need something like libipavault library...

We'll need a helper process unless we can find a fully async library to
deal with the vault. Authentication to the vault over REST-like APIs
will also be an interesting problem ...

Let me summarize what we have:

We agree that
=============
- PKCS#11 is the right interface for key manipulation and certificate
retrieval.
- We can have PKCS#11 client library talking to local SSSD so the data
retrieval logic can be hidden in SSSD (something like "PKCS-responder").


Open questions/variants to discuss are
==============
a) Do not invent any new schema for certificates and public keys. A set
of "PKCS-providers" in SSSD will aggregate the data from various sources
and transform them to appropriate format.

A heavy machinery in SSSD will convert existing data in IPA LDAP tree to
PKCS#11 objects presented over PKCS#11 interface.

Petr requested a diagram for this scenario; see attachment.


- CA certs will be pulled from cn=CAcert,cn=ipa,cn=etc,dc=ipa,dc=example
and transformed to required format. ("PKCS-CA-provider")

(note: actually, not cn=CAcert)

- Other data except DNSSEC keys (like user certificates) will be handled
specially by special provider. (Most likely this provider will stay
unimplemented :-))
- DNS public keys can be stored as DNS records and converted to format
appropriate for PKCS#11 somehow. One problem is that sometimes you need
to generate keys but do not publish them in DNS zone. Situations like
this will require special handling. ("PKCS-DNSSEC-provider")
- DNS private keys are special case because they require special
handling for key wrapping. Sub-variant are:
  aa) Use IPA vault. It requires Vault support in IPA 4.0 (for DNSSEC)
and also client-side support in SSSD. (special
"PKCS-DNSSEC-vault-provider")
  ab) Use some simpler single-purpose key wrapping mechanism designed
specially for DNSSEC. Implement the key un/wrapping in special code path
in SSSD. ("PKCS-DNSSEC-simple-provider")


b) Use a new schema for generic PKCS#11 module in LDAP. The generic
"PKCS-ldap-provider" will simply 1:1 map the data in LDAP to objects
presented over PKCS#11 interface.
- DNS public keys, CA certs and generally all public data will be stored
in the new schema in plain text.
- This approach supports user certificates and all other use cases out
of the box.
- Private keys needs special handling:
  aa) Use IPA vault. It requires Vault support in IPA 4.0 (for DNSSEC)
and also client-side support in SSSD.
  ab) Use some simpler single-purpose key wrapping mechanism. (Proposal
with wrapping keys stored in LDAP is on the mailing list.) Implement the
key un/wrapping in special code path in "PKCS-ldap-provider". The
difference is that now we don't need to call any REST API from SSSD and
we can read all the data from LDAP or file system.


Personally, I agree with the pluggable approach with various PKCS
providers but I still can see the value in variant (b) with LDAP schema
designed specifically for PKCS#11.

+1


It enables us to use generic PKCS#11 interface in all applications and
we do not need to tweak SSSD providers specifically for each use case.
IMHO it is also easier to implement on SSSD side of things. The only
problem is that we didn't agree on a key wrapping mechanism.


Maybe we can start with generic LDAP schema and some simple key wrapping
mechanism for now and gradually add support for Vault in the future.
SSSD will be pluggable so we will not be tied to the simpler mechanism
forever.

Also, I'm not insisting on storing wrapping keys in LDAP. In theory, we
could store one wrapping key per-user on disk and let SSSD to read that
key when user logs in.

Let's finally decide what to do! Please keep in mind that we need
something feasible and reasonably secure for DNSSEC and CA rotation 4.0.



--
Jan Cholasta

<<attachment: sssd-pkcs11.svg>>

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