I agree with *almost* everything Sumit said. See my inline comments below.

On 16.12.2016 11:53, Sumit Bose wrote:
On Tue, Dec 06, 2016 at 04:39:10PM +0100, Florence Blanc-Renaud wrote:
Hi,

I have started a feature description for the Certificate Identity Mapping at
the following location:
http://www.freeipa.org/page/V4/Certificate_Identity_Mapping

This is a first step, focusing on the interface we would like to provide. It
still contains open questions, some of which are linked to the corresponding
design on SSSD side:
https://fedorahosted.org/sssd/wiki/DesignDocs/MatchingAndMappingCertificates
https://fedorahosted.org/sssd/wiki/DesignDocs/SmartcardsAndMultipleIdentities

Comments, concerns and suggestions are welcome. Thanks!

Hi Flo,

thank you very much for setting up the page.

My comments are mostly about the commands.

certmappingconfig-mod:

* --enable=Boolean: if this option is 'False' SSSD will basically show
  the current behavior and just look up the certificates directly. But I
  wonder if the option is needed at all because not adding any mapping
  rules would have the same effect.

  What is the scope here, only the IPA domain, or all trusted domains as
  well? If it is for trusted domains as well will the certmappingrule-*
  commands and user-{add/remove}-certmapping return an error?

  So, in general I see an overlap with the mapping rules and I think it
  would be clearer to drop this option and do the lookups according to
  the mapping rules.

* --prompt-username=Boolean: the description implies that this option is
  synonymous to 1:1 mapping, but it is not. On Linux authentication in
  most cases use a user name either by directly asking (e.g. /bin/login)
  or using the current user name (e.g. sudo). So, according to its name
  it would only control if gdm is allowed to ask for an (optional) user
  name.

  If the option is renamed to e.g. --force-1-to-1-mapping to really
  enforce a 1:1 mapping then it would make sense to derived to gdm
  behavior. I.e. if 1:1 mapping is enforce it makes no sense for gdm to
  ask for a user name and if it is not enforced then it makes sense to
  offer and optional user name input field.

* --enable-username-mismatch=Boolean: I think this option can be
  dropped. My test so far show that if a non-matching hint is given on a
  Windows client authentication fails.

* --alternate-attribute=STRING: I think this option isn't needed as
  well. For IPA server-side we should decide on an attribute name and
  add it to the schema for user objects. On the client side the
  attribute name can be taken from the mapping rule.A


certmappingrule.*:

* ISSUERDN: it looks like you want to use issuerName here. In
  certificateRecord it it used with LDAP ordering and I would prefer
  LDAP ordering at all points where we have a choice. Unfortunately in the
  issuer-subject mapping AD dictates X.500 ordering.

LDAP ordering should indeed be preferred, as it is used everywhere else in IPA. We can convert to/from X.500 ordering where necessary, when possible.


* DOMAINDN: does this refer to the nsslapd-certmap-basedn attribute in
  the example? My intention in the SSSD design-page was to specify the
  domain (as in DNS domain/IPA domain/trusted domain) where the matching
  user should be searched. Different domains might certificates from
  different issuers and some domains might not even use certificates.
  With this information SSSD does not have to search any domain trusted
  by IPA from a given certificate, but look only at domains listed here
  (the attribute should be a multi-value one).

  There are objects in the LDAP tree for each trusted domain which are
  used by SSSD so using a DN syntax would be valid here.

We use domain names rather than DNs to refer to domains everywhere else in the framework. I don't think this place should be an exception.


* LDAPSEARCHFILTER: I think a separate option is not need. LDAP search
  filters should just be a special kind of mapping rules. I can image in
  syntax like: <LDAPFILTER:(&(cn=%A)(email=%B)(authType=pkinit))>. I
  think the difficult part with the LDAP filters will to define sensible
  templates.

I'm not sure I understand. Could you please elaborate a little bit?

  But as long as we keep the general mapping rule syntax
  flexible the LDAP filter rules can be added in a later version.

IMHO it should be the other way round and LDAP filters should be implemented first, as they offer all the flexibility we need (all of the other fields can be easily implemented on top of LDAP filters) and are by default extensible without having to update servers and clients.


* enable/disable: I think this is a good idea and would be consistent
  with other rules like HBAC and sudo

* user-{add/mod} LOGIN --certmappingdata DATA: I think it might be
  better to not add this option and only implement the
  'user-{add/remove}-certmapping' commands

* user-{add/remove}-certmapping: you say '... almost any type of mapping,
  or a more user-friendly API ...'. I would not say 'or' but 'and' and
  implement both

* ipaCertMappingEnableMismatch and ipaCertMappingAlternateIdAttribute; I
  think both are note needed, see above

* altSecurityIdentities: I would prefer to use a different name and OID.
  Using the same definition as AD would imo imply that it can be used in
  the same way as in AD. But e.g. AD also supports other content like
  KERBEROS:alternative_user_principal@AD.DOMAIN which we will not
  support.

* issuerName vs ipaCAIssuerDN: I would prefer issuerName because it is
  general UTF-8 and not DN syntax (1.3.6.1.4.1.1466.115.121.1.12). Since
  the issuer DN in general will not be a DN from the local LDAP tree I
  think the UTF-8 version fits better.

I think it's worth mentioning that if the attribute used DN syntax and matching, we wouldn't have to worry about normalizing the issuer name before searching for it, as DS would do that for us.


* nsslapd-certmap-basedn, see DOMAINDN above

* altSecurityIdentities example: X.500 ordering is used by AD here and
  unfortunately I think we have to adopt it at least for this specific
  usage, here is an ldapsearch output from AD:

altSecurityIdentities:
X509:<I>DC=devel,DC=ad,CN=ad-AD-SERVER-CA<S>DC=devel,DC
 =ad,CN=Users,CN=t u,E=test.user@email.domain
altSecurityIdentities: X509:<I>O=Red Hat,OU=prod,CN=Certificate
Authority<S>DC
 =com,DC=redhat,OU=users,OID.0.9.2342.19200300.100.1.1=sbose,E=sb...@redhat.co
 m,CN=Sumit Bose Sumit Bose

* Certificate Mapping Administrators or re-use Certificate
  Administrators: I would prefer a new 'Certificate Mapping
  Administrators'

* Users can manage their own X.509 certificate mappings? I'm not sure
  here, at the first glance I would say no. How are OTP tokens handled?
  Maybe this would be a candidate for certmappingconfig-* option?

I think a better question is "How is userCertificate handled?"

Anyway, self-service permissions can be enabled/disabled, so there is really no need for a new certmappingconfig option.


That's all :-)

bye,
Sumit



--
Jan Cholasta

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