[Freeipa-devel] [PATCH] 0097 Add options to write lightweight CA cert or chain to file
Fraser Tweedale
ftweedal at redhat.com
Fri Aug 19 11:11:56 UTC 2016
Bump for review.
On Wed, Aug 17, 2016 at 12:09:39AM +1000, Fraser Tweedale wrote:
> On Tue, Aug 16, 2016 at 08:10:08AM +0200, Jan Cholasta wrote:
> > On 16.8.2016 07:24, Fraser Tweedale wrote:
> > > On Mon, Aug 15, 2016 at 08:19:33AM +0200, Jan Cholasta wrote:
> > > > On 9.8.2016 16:47, Fraser Tweedale wrote:
> > > > > On Mon, Aug 08, 2016 at 10:49:27AM +0200, Jan Cholasta wrote:
> > > > > > On 8.8.2016 09:06, Fraser Tweedale wrote:
> > > > > > > On Mon, Aug 08, 2016 at 08:54:05AM +0200, Jan Cholasta wrote:
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > On 8.8.2016 06:34, Fraser Tweedale wrote:
> > > > > > > > > Please review the attached patch with adds --certificate-out and
> > > > > > > > > --certificate-chain-out options to `ca-show' command.
> > > > > > > > >
> > > > > > > > > Note that --certificate-chain-out currently writes a bogus file due
> > > > > > > > > to a bug in Dogtag that will be fixed in this week's build.
> > > > > > > > >
> > > > > > > > > https://fedorahosted.org/freeipa/ticket/6178
> > > > > > > >
> > > > > > > > 1) The client-side *-out options should be defined on the client side, not
> > > > > > > > on the server side.
> > > > > > > >
> > > > > > > Will option defined on client side be propagated to, and observable
> > > > > > > in the ipaserver plugin? The ipaserver plugin needs to observe that
> > > > > > > *-out has been requested and executes additional command(s) on that
> > > > > > > basis.
> > > > > >
> > > > > > Is there a reason not to *always* return the certs?
> > > > > >
> > > > > We hit Dogtag to retrieve them.
> > > >
> > > > I don't think that's an issue in a -show command.
> > > >
> > > cert_show is invoked by other commands (cert_find*, cert_show,
> > > cert_request, cert_status, ca_del) but these all hit Dogtag anyway
> > > so I suppose that's fine. I'll return the cert *and* the chain in
> > > separate attributes, unconditionally.
> > >
> > > > >
> > > > > > >
> > > > > > > >
> > > > > > > > 2) I don't think there should be additional information included in summary
> > > > > > > > (and it definitely should not be multi-line). I would rather inform the user
> > > > > > > > via an error message when unable to write the files.
> > > > > > > >
> > > > > > > I was just following the pattern of other commands that write certs,
> > > > > > > profile config, etc. Apart from consistency with other commands I
> > > > > > > agree that there is no need to have it. So I will remove it.
> > > > > > >
> > > > > > > > If you think there is an actual value in informing the user about
> > > > > > > > successfully writing the files, please use ipalib.messages for the job.
> > > > > > > >
> > > > > > > >
> > > > > > > > 3) IMO a better format for the certificate chain than PKCS#7 would be
> > > > > > > > concatenated PEM, as that's the most commonly used format in IPA (in
> > > > > > > > installers, there are no cert chains in API commands ATM).
> > > > > > > >
> > > > > > > Sure, but the main use case isn't IPA. Other apps require PKCS #7
> > > > > > > or concatenated PEMs, but sometimes they must be concatenated
> > > > > > > forward, and othertimes backwards. There is no one size fits all.
> > > > > >
> > > > > > True, which is exactly why I think we should at least be self-consistent and
> > > > > > use concatenated PEM (and multi-value DER over the wire).
> > > > > >
> > > > > Dogtag returns a PKCS7 (either DER or PEM, according to HTTP Accept
> > > > > header).
> > > > >
> > > > > If we want list-of-PEMs between server and client we have to convert
> > > > > on the server. Do we have a good way of doing this without exec'ing
> > > > > `openssl pkcs7' on the server? Is it acceptable to exec 'openssl'
> > > > > to do the conversion on the server? python-nss does not have PKCS7
> > > > > functions and I am not keen on adding a pyasn1 PKCS7 parser just for
> > > > > the sake of pushing bits as list-of-PEMs.
> > > >
> > > > I'm afraid we can't avoid conversion to/from PKCS#7 one way or the other.
> > > > For example, if we added a call to retrieve external CA chain using certs
> > > > from cn=certificates,cn=ipa,cn=etc, we would have to convert the result to
> > > > PKCS#7 if it was our cert chain format of choice.
> > > >
> > > > What we can avoid though is executing "openssl pkcs7" to do the conversion -
> > > > we can use an approach similar to our DNSSEC code and use python-cffi to
> > > > call libcrypto's PKCS#7 conversion routines instead.
> > > >
> > > I had a look at the OpenSSL API for parsing PKCS #7; now I prefer to
> > > exec `openssl' to do the job :)
> > >
> > > I will transmit DER-encoded PKCS #7 object on the wire; we cannot
> > > used multi-valued DER attribute because order is important. Client
> > > will convert to PEMs.
> >
> > Well, my point was not to send PKCS#7 over the wire, so that clients
> > (including 3rd party clients) do not have to convert from PKCS#7 themselves.
> >
> > In fact we can use multi-valued DER - whatever you send over the wire from
> > the server will be received in the exact same order by the client. Even if
> > it wasn't, you can easily restore the order by matching issuer and subject
> > names of the certificates.
> >
> > >
> > > Should have new patch on list this afternoon.
> > >
> > > Thanks,
> > > Fraser
> > >
> > > > >
> > > > > FWIW, man pages and code suggest that PKCS #7 is accepted in
> > > > > installer, etc.
> > > >
> > > > True, but that's a relatively new feature (since 4.1) and the installer
> > > > internally executes "openssl pkcs7" to convert PKCS #7 to list of certs :-)
> > > >
> > > > >
> > > > > > > We can add an option to control the format later, but for now,
> > > > > > > Dogtag returns a PKCS #7 (PEM or DER) so let's go with that. Worst
> > > > > > > case is an admin has to invoke `openssl pkcs7' and concat the certs
> > > > > > > themselves.
> > > > > >
> > > > > > AFAIK none of NSS, OpenSSL or p11-kit can use PKCS#7 cert chains directly,
> > > > > > so I'm afraid the worst case would happen virtually always.
> > > > > >
> > > > > If you're OK with invoking OpenSSL on the client to convert PKCS #7
> > > > > to list-of-PEMs (similar to what is done in
> > > > > ipapython.certdb.NSSDatabase) then we can have the client perform
> > > > > the conversion.
> > > >
> > > > See above.
> > > >
> > > > >
> > > > > > >
> > > > > > > >
> > > > > > > > 4) Over the wire, the certs should be DER-formatted, as that's the most
> > > > > > > > common wire format in other API commands.
> > > > > > > >
> > > > > > > OK.
> > > > > > >
> > > > > > > >
> > > > > > > > 5) What is the benefit in having the CA cert and the rest of the chain
> > > > > > > > separate? For end-entity certs it makes sense to separate the cert from the
> > > > > > > > CA chain, but for CA certs, you usually want the full chain, no?
> > > > > > > >
> > > > > > > If you want to anchor trust directly at a subca (e.g. restrict VPN
> > > > > > > login to certs issued by VPN sub-CA) then you often just want the
> > > > > > > cert. The chain option does subsume it, at cost of more work for
> > > > > > > administrators with this use case. I think it makes sense to keep
> > > > > > > both options.
> > > > > >
> > > > > > Does it? From what you described above, you either want just the sub-CA
> > > > > > cert, or the full chain including the sub-CA cert, in which case it might
> > > > > > make more sense to have a single --out option and a --chain flag.
> > > > > >
> > > > > How about --certificate-out which defaults to single cert, but does
> > > > > chain (as list-of-PEMs) when --chain flag given.
> > > > >
> > > > > Per https://fedorahosted.org/freeipa/ticket/5166 let's not add more
> > > > > `--out' options.
> > > >
> > > > +1
> > > >
> Updated patch 0097-2 attached, and new patch 0099 which must be
> applied first.
>
> I have implemented the suggested changes, except for cffi (I execute
> `openssl pkcs7' instead).
>
> There are two new output attributes on the wire, 'certificate'
> (single-value DER X.509), and 'certificate_chain' (ordered
> multi-value DER X.509). They are always returned. The first cert
> in the chain is always the same as 'certificate'; obviously this is
> redunant but I have left it this way because I think usage is
> clearer.
>
> Thanks,
> Fraser
> From 77d7d0185bcf3cb86f56bd128507a8e2cfedc775 Mon Sep 17 00:00:00 2001
> From: Fraser Tweedale <ftweedal at redhat.com>
> Date: Tue, 16 Aug 2016 13:16:58 +1000
> Subject: [PATCH] Add function for extracting PEM certs from PKCS #7
>
> Add a single function for extracting X.509 certs in PEM format from
> a PKCS #7 object. Refactor sites that execute ``openssl pkcs7`` to
> use the new function.
>
> Part of: https://fedorahosted.org/freeipa/ticket/6178
> ---
> ipalib/x509.py | 21 ++++++++++++++++-
> ipapython/certdb.py | 14 ++++-------
> ipaserver/install/cainstance.py | 52 +++++++++++++++--------------------------
> 3 files changed, 43 insertions(+), 44 deletions(-)
>
> diff --git a/ipalib/x509.py b/ipalib/x509.py
> index 82194922d151a1b0f2df03df3578ad45b43b71c9..782519ce45e05e09d4dc02d41a537daab84db9e4 100644
> --- a/ipalib/x509.py
> +++ b/ipalib/x509.py
> @@ -50,11 +50,12 @@ from ipalib import util
> from ipalib import errors
> from ipaplatform.paths import paths
> from ipapython.dn import DN
> +from ipapython import ipautil
>
> PEM = 0
> DER = 1
>
> -PEM_REGEX = re.compile(r'(?<=-----BEGIN CERTIFICATE-----).*?(?=-----END CERTIFICATE-----)', re.DOTALL)
> +PEM_REGEX = re.compile(r'-----BEGIN CERTIFICATE-----.*?-----END CERTIFICATE-----', re.DOTALL)
>
> EKU_SERVER_AUTH = '1.3.6.1.5.5.7.3.1'
> EKU_CLIENT_AUTH = '1.3.6.1.5.5.7.3.2'
> @@ -144,6 +145,24 @@ def load_certificate_list(data, dbdir=None):
> certs = [load_certificate(cert, PEM, dbdir) for cert in certs]
> return certs
>
> +
> +def pkcs7_to_pems(data, datatype=PEM):
> + """
> + Extract certificates from a PKCS #7 object.
> +
> + Return a ``list`` of X.509 PEM strings.
> +
> + May throw ``ipautil.CalledProcessError`` on invalid data.
> +
> + """
> + cmd = [
> + paths.OPENSSL, "pkcs7", "-print_certs",
> + "-inform", "PEM" if datatype == PEM else "DER",
> + ]
> + result = ipautil.run(cmd, stdin=data, capture_output=True)
> + return PEM_REGEX.findall(result.output)
> +
> +
> def load_certificate_list_from_file(filename, dbdir=None):
> """
> Load a certificate list from a PEM file.
> diff --git a/ipapython/certdb.py b/ipapython/certdb.py
> index e19f712d82f160ebc5de9c5b8d6627cb941c2cef..fd18023794a2daace60efd97aff54180b8409bbd 100644
> --- a/ipapython/certdb.py
> +++ b/ipapython/certdb.py
> @@ -270,13 +270,11 @@ class NSSDatabase(object):
> continue
>
> if label in ('PKCS7', 'PKCS #7 SIGNED DATA', 'CERTIFICATE'):
> - args = [
> - paths.OPENSSL, 'pkcs7',
> - '-print_certs',
> - ]
> try:
> - result = ipautil.run(
> - args, stdin=body, capture_output=True)
> + certs = x509.pkcs7_to_pems(body)
> + extracted_certs += '\n'.join(certs) + '\n'
> + loaded = True
> + continue
> except ipautil.CalledProcessError as e:
> if label == 'CERTIFICATE':
> root_logger.warning(
> @@ -287,10 +285,6 @@ class NSSDatabase(object):
> "Skipping PKCS#7 in %s at line %s: %s",
> filename, line, e)
> continue
> - else:
> - extracted_certs += result.output + '\n'
> - loaded = True
> - continue
>
> if label in ('PRIVATE KEY', 'ENCRYPTED PRIVATE KEY',
> 'RSA PRIVATE KEY', 'DSA PRIVATE KEY',
> diff --git a/ipaserver/install/cainstance.py b/ipaserver/install/cainstance.py
> index 070498fe8a394802ea55f848a268e2b6563ec472..12c973c8acdcb0e657d92695dc28043b29966f2c 100644
> --- a/ipaserver/install/cainstance.py
> +++ b/ipaserver/install/cainstance.py
> @@ -839,44 +839,30 @@ class CAInstance(DogtagInstance):
> # makes openssl throw up.
> data = base64.b64decode(chain)
>
> - result = ipautil.run(
> - [paths.OPENSSL,
> - "pkcs7",
> - "-inform",
> - "DER",
> - "-print_certs",
> - ], stdin=data, capture_output=True)
> - certlist = result.output
> + certlist = x509.pkcs7_to_pems(data, x509.DER)
>
> # Ok, now we have all the certificates in certs, walk through it
> # and pull out each certificate and add it to our database
>
> - st = 1
> - en = 0
> - subid = 0
> ca_dn = DN(('CN','Certificate Authority'), self.subject_base)
> - while st > 0:
> - st = certlist.find('-----BEGIN', en)
> - en = certlist.find('-----END', en+1)
> - if st > 0:
> - try:
> - (chain_fd, chain_name) = tempfile.mkstemp()
> - os.write(chain_fd, certlist[st:en+25])
> - os.close(chain_fd)
> - (_rdn, subject_dn) = certs.get_cert_nickname(certlist[st:en+25])
> - if subject_dn == ca_dn:
> - nick = get_ca_nickname(self.realm)
> - trust_flags = 'CT,C,C'
> - else:
> - nick = str(subject_dn)
> - trust_flags = ',,'
> - self.__run_certutil(
> - ['-A', '-t', trust_flags, '-n', nick, '-a',
> - '-i', chain_name]
> - )
> - finally:
> - os.remove(chain_name)
> - subid += 1
> + for cert in certlist:
> + try:
> + (chain_fd, chain_name) = tempfile.mkstemp()
> + os.write(chain_fd, cert)
> + os.close(chain_fd)
> + (_rdn, subject_dn) = certs.get_cert_nickname(cert)
> + if subject_dn == ca_dn:
> + nick = get_ca_nickname(self.realm)
> + trust_flags = 'CT,C,C'
> + else:
> + nick = str(subject_dn)
> + trust_flags = ',,'
> + self.__run_certutil(
> + ['-A', '-t', trust_flags, '-n', nick, '-a',
> + '-i', chain_name]
> + )
> + finally:
> + os.remove(chain_name)
>
> def __request_ra_certificate(self):
> # Create a noise file for generating our private key
> --
> 2.5.5
>
> From 4779e2cd4c30b896dbe914c095c0dbc068e38b63 Mon Sep 17 00:00:00 2001
> From: Fraser Tweedale <ftweedal at redhat.com>
> Date: Mon, 8 Aug 2016 14:27:20 +1000
> Subject: [PATCH] Add options to write lightweight CA cert or chain to file
>
> Administrators need a way to retrieve the certificate or certificate
> chain of an IPA-managed lightweight CA. Add output attributes to
> `ca_show' containing the CA certificate and chain (as multiple DER
> values), and add the `--certificate-out' option and `--chain' flag
> as client-side options for writing one or the other to a file.
>
> Fixes: https://fedorahosted.org/freeipa/ticket/6178
> ---
> ipaclient/plugins/ca.py | 47 +++++++++++++++++++++++++++++++++++++++++++++
> ipaserver/plugins/ca.py | 34 ++++++++++++++++++++++++++++----
> ipaserver/plugins/dogtag.py | 12 ++++++++++++
> 3 files changed, 89 insertions(+), 4 deletions(-)
> create mode 100644 ipaclient/plugins/ca.py
>
> diff --git a/ipaclient/plugins/ca.py b/ipaclient/plugins/ca.py
> new file mode 100644
> index 0000000000000000000000000000000000000000..63770ff42af10f3f7d9419b692107433ddb35198
> --- /dev/null
> +++ b/ipaclient/plugins/ca.py
> @@ -0,0 +1,47 @@
> +#
> +# Copyright (C) 2016 FreeIPA Contributors see COPYING for license
> +#
> +
> +import base64
> +from ipaclient.frontend import MethodOverride
> +from ipalib import util, x509, Flag, Str
> +from ipalib.plugable import Registry
> +from ipalib.text import _
> +
> +register = Registry()
> +
> +
> + at register(override=True, no_fail=True)
> +class ca_show(MethodOverride):
> +
> + takes_options = (
> + Str('certificate_out?',
> + doc=_('Write certificate to file'),
> + include='cli',
> + ),
> + Flag('chain',
> + default=False,
> + doc=_('Write certificate chain instead of single certificate'),
> + include='cli',
> + ),
> + )
> +
> + def forward(self, *keys, **options):
> + filename = None
> + if 'certificate_out' in options:
> + filename = options.pop('certificate_out')
> + util.check_writable_file(filename)
> + chain = options.pop('chain', False)
> +
> + result = super(ca_show, self).forward(*keys, **options)
> + if filename:
> + to_pem = lambda x: x509.make_pem(base64.b64encode(x))
> + if chain:
> + ders = result['result']['certificate_chain']
> + data = '\n'.join(map(to_pem, ders))
> + else:
> + data = to_pem(result['result']['certificate'])
> + with open(filename, 'wb') as f:
> + f.write(data)
> +
> + return result
> diff --git a/ipaserver/plugins/ca.py b/ipaserver/plugins/ca.py
> index 966ae2b1bdb4bb0207dfa58f0e9c951bc930f766..2e1787707bf002455478c969cd1914692c743b9c 100644
> --- a/ipaserver/plugins/ca.py
> +++ b/ipaserver/plugins/ca.py
> @@ -2,14 +2,14 @@
> # Copyright (C) 2016 FreeIPA Contributors see COPYING for license
> #
>
> -from ipalib import api, errors, DNParam, Str
> +from ipalib import api, errors, Bytes, DNParam, Str
> from ipalib.constants import IPA_CA_CN
> from ipalib.plugable import Registry
> from ipaserver.plugins.baseldap import (
> LDAPObject, LDAPSearch, LDAPCreate, LDAPDelete,
> LDAPUpdate, LDAPRetrieve)
> from ipaserver.plugins.cert import ca_enabled_check
> -from ipalib import _, ngettext
> +from ipalib import _, ngettext, x509
>
>
> __doc__ = _("""
> @@ -140,9 +140,35 @@ class ca_find(LDAPSearch):
> class ca_show(LDAPRetrieve):
> __doc__ = _("Display the properties of a CA.")
>
> - def execute(self, *args, **kwargs):
> + has_output_params = LDAPRetrieve.has_output_params + (
> + Bytes(
> + 'certificate',
> + label=_("Certificate"),
> + doc=_("X.509 certificate"),
> + flags={'no_display'},
> + ),
> + Bytes(
> + 'certificate_chain*',
> + label=_("Certificate chain"),
> + doc=_("PKCS #7 certificate chain"),
> + flags={'no_display'},
> + ),
> + )
> +
> + def execute(self, *keys, **options):
> ca_enabled_check()
> - return super(ca_show, self).execute(*args, **kwargs)
> + result = super(ca_show, self).execute(*keys, **options)
> +
> + ca_id = result['result']['ipacaid'][0]
> + with self.api.Backend.ra_lightweight_ca as ca_api:
> + result['result']['certificate'] = ca_api.read_ca_cert(ca_id)
> +
> + pkcs7_der = ca_api.read_ca_chain(ca_id)
> + pems = x509.pkcs7_to_pems(pkcs7_der, x509.DER)
> + ders = (x509.normalize_certificate(pem) for pem in pems)
> + result['result']['certificate_chain'] = list(ders)
> +
> + return result
>
>
> @register()
> diff --git a/ipaserver/plugins/dogtag.py b/ipaserver/plugins/dogtag.py
> index aef1e888eb1b6c273c1fd12cbf4912407f8f8132..1fd3106e0ae723eb30dbe32c61e637790f6085d2 100644
> --- a/ipaserver/plugins/dogtag.py
> +++ b/ipaserver/plugins/dogtag.py
> @@ -2205,6 +2205,18 @@ class ra_lightweight_ca(RestClient):
> except:
> raise errors.RemoteRetrieveError(reason=_("Response from CA was not valid JSON"))
>
> + def read_ca_cert(self, ca_id):
> + status, resp_headers, resp_body = self._ssldo(
> + 'GET', '{}/cert'.format(ca_id),
> + headers={'Accept': 'application/pkix-cert'})
> + return resp_body
> +
> + def read_ca_chain(self, ca_id):
> + status, resp_headers, resp_body = self._ssldo(
> + 'GET', '{}/chain'.format(ca_id),
> + headers={'Accept': 'application/pkcs7-mime'})
> + return resp_body
> +
> def disable_ca(self, ca_id):
> self._ssldo(
> 'POST', ca_id + '/disable',
> --
> 2.5.5
>
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