Public Key Document Signing for Oslo Messaging

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The PKI version of the Keystone tokens use a standard format for cryptographic signing of documents. Crypto Message Syntax (CMS) is the mechanism behind S/MIME and is well supported by the major cryptographic libraries: OpenSSL and NSS both have well documented CMS support. Messaging in OpenStack requires guaranteed identification of the author.

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certmonger-session

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There is more to the certmonger story. A lot more. After my last attempt I tried to use certmonger:

  • as a user-launched process
  • to get a user certificate
  • direct from the dogtag instance behind FreeIPA

I was not 100% successful, but the attempt did have some positive results.

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FreeIPA web call from Python

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This was a response to a post of mine in 2010. The comment was unformatted in the response, and I wanted to get it readable. Its a great example of making a Kerberized web call.

Courtesy of Rich Megginson

Note: requires MIT kerberos 1.11 or later if you want to skip doing the kinit, and just let the script do the kinit implicitly with the keytab.

import kerberos
import sys
import os
from requests.auth import AuthBase
import requests
import json
 
class IPAAuth(AuthBase):
    def __init__(self, hostname, keytab):
        self.hostname = hostname
        self.keytab = keytab
        self.token = None
 
        self.refresh_auth()
 
    def __call__(self, request):
        if not self.token:
            self.refresh_auth()
 
        request.headers['Authorization'] = 'negotiate ' + self.token
 
        return request
 
    def refresh_auth(self):
        if self.keytab:
            os.environ['KRB5_CLIENT_KTNAME'] = self.keytab
        else:
            LOG.warn('No IPA client kerberos keytab file given')
        service = "HTTP@" + self.hostname
        flags = kerberos.GSS_C_MUTUAL_FLAG | kerberos.GSS_C_SEQUENCE_FLAG
        try:
            (_, vc) = kerberos.authGSSClientInit(service, flags)
        except kerberos.GSSError, e:
            LOG.error("caught kerberos exception %r" % e)
            raise e
        try:
            kerberos.authGSSClientStep(vc, "")
        except kerberos.GSSError, e:
            LOG.error("caught kerberos exception %r" % e)
            raise e
        self.token = kerberos.authGSSClientResponse(vc)
 
 
hostname, url, keytab, cacert = sys.argv[1:]
 
request = requests.Session()
request.auth = IPAAuth(hostname, keytab)
ipaurl = 'https://%s/ipa' % hostname
jsonurl = url % {'hostname': hostname}
request.headers.update({'Content-Type': 'application/json',
                        'Referer': ipaurl})
request.verify = cacert
 
myargs = {'method': 'dnsrecord_add',
          'params': [["testdomain.com", "test4.testdomain.com"],
                     {'a_part_ip_address': '172.31.11.4'}],
          'id': 0}
resp = request.post(jsonurl, data=json.dumps(myargs))
print resp.json()
 
myargs = {'method': 'dnsrecord_find', 'params': [["testdomain.com"], {}], 'id': 0}
resp = request.post(jsonurl, data=json.dumps(myargs))
print resp.json()

Run the script like this:

python script.py ipahost.domain.tld ‘https://%(hostname)s/ipa/json’ myuser.keytab /etc/ipa/ca.crt

Using Certmonger to Generate a selfsign Cert for CMS

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We want to replace the shell call to openssl for certificate generation in Keystone (and the rest of OpenStack) with calls to Certmonger. Certmonger supports both OpenSSL and NSS. Certmonger can support a selfsigned approach, as well as tie in to a real Certificate Authority. Here are the steps I took to test out selfsigning, as well as my notes for follow on work.
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Splitting a patch

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To make things easier for your code reviewer, each patch should be small, and hold one well defined change. I break this rule all the time, and it comes back to bite me. What happens is that I get heads down coding, and I have a solution that involves changes to wide number of files and subsystems, new abstractions, etc. Here is how I am currently dealing with breaking down a big patch.

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