Hi,
Thanks very much for the feedback! Some responses below; I hope you'll
let me know what you think of my reasoning.
On 07/20/2016 04:20 AM, Jan Cholasta wrote:
Hi,
On 17.6.2016 00:06, Ben Lipton wrote:
On 06/14/2016 08:27 AM, Ben Lipton wrote:
Hello all,
I have written up a design proposal for making certificate requests
easier to generate when using alternate certificate profiles:
http://www.freeipa.org/page/V4/Automatic_Certificate_Request_Generation.
The use case for this is described in
https://fedorahosted.org/freeipa/ticket/4899. I will be working on
implementing this design over the next couple of months. If you have
the time and interest, please take a look and share any comments or
concerns that you have.
Thanks!
Ben
Just a quick update to say that I've created a new document that covers
the proposed schema additions in a more descriptive way (with diagrams!)
I'm very new to developing with LDAP, so some more experienced eyes on
the proposal would be very helpful, even if you don't have time to
absorb the full design. Please take a look at
http://www.freeipa.org/page/V4/Automatic_Certificate_Request_Generation/Schema
if you have a chance.
I finally had a chance to take a look at this, here are some comments:
1) I don't like how transformation rules are tied to a particular
helper and have to be duplicated for each of them. They should be
generic and work with any helper, as helpers are just an
implementation detail and their resulting data is the same.
In fact, I think I would prefer if the CSR was generated using
python-cryptography's CertificateSigningRequestBuilder [1] rather than
openssl or certutil or any other command line tool.
There are lots of tools that users might want to use to manage their
private keys, so I don't know if we can assume that whatever library we
prefer will actually be able to access the private key to sign a CSR,
which is why I thought it would be useful to support more than one. The
purpose of the mapping rule is to tie together the transformation rules
that produce the same data into an object that's
implementation-agnostic, so that profiles referencing those rules are
automatically compatible with all the helper options.
I do agree that it would be preferable to target APIs rather than
command-line tools. When looking at the openSSL and NSS APIs I came to
the conclusion that they would be more difficult than the command-line
tools to target, as a first implementation. However, I haven't really
looked at python-cryptography, and maybe it would have been a good choice.
2) The schema seems unnecessarily complex. I think all we need is a
single new multi-value attribute in certprofile. For your S/MIME
example, it could be something like:
attr: subjectname=CN={subject.cn},{subject_base}
attr: san_rfc822name={subject.email}
attr: san_directoryname={subject.dn}
This is turning out to be a common (and, I think, reasonable) reaction
to the proposal. It is rather complex, and I worry that it will be
difficult to configure. On the other hand, there is some hidden
complexity to enabling a simpler config format, as well. One of the
goals of the project as it was presented to me was to allow the creation
of profiles that add certificate extensions *that FreeIPA doesn't yet
know about*. With the current proposal, one only has to add a rule
generating text that the helper will understand. With your suggestion,
if there's a mapping between "san_directoryname" and the corresponding
API calls or configuration lines, we need some way for users to augment
that mapping without changing the code. If there's no mapping, and it's
just done with text processing, we need enough in the config format to
be able to generate fairly complex structures:
builder = builder.subject_name(x509.Name(u'CN=user,O=EXAMPLE.COM'))
builder =
builder.add_extension(x509.SubjectAlternativeName([x509.RFC822Name(u'u...@example.com'),
x509.DirectoryName(x509.Name(u'CN=user,O=EXAMPLE.COM'))]), False)
and we need to do it without it being equivalent to calling eval() on
the config attributes. I'm not sure how to achieve this (is it safe to
call getattr(x509, extensiontype)(value) where extensiontype and value
are user-specified?) and it definitely would have to be tied to a
particular library/tool.
Ben
Honza
[1]
<https://cryptography.io/en/latest/x509/reference/#x-509-csr-certificate-signing-request-builder-object>
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