This upstream commit uses unsecured DNS to translate the host name. This causes the client to switch to a different host name, not the one in the configuration, thus breaking Kerberos security. commit fc8a8c6582c5e3b7a8a3a4b887061ba7a3f150a1 Author: Mike McLean <mikem> Date: Fri May 13 10:47:55 2016 -0400 parse host from baseurl in _serverPrincipal() krb auth working now diff --git a/koji/__init__.py b/koji/__init__.py index aceaeb5..a7bf055 100644 --- a/koji/__init__.py +++ b/koji/__init__.py @@ -1945,13 +1945,13 @@ class ClientSession(object): def _serverPrincipal(self, cprinc): """Get the Kerberos principal of the server we're connecting to, based on baseurl.""" + + uri = urlparse.urlsplit(self.baseurl) + host, port = urllib.splitport(uri[1]) if self.opts.get('krb_rdns', True): - servername = socket.getfqdn(self._host) + servername = socket.getfqdn(host) else: - servername = self._host - #portspec = servername.find(':') - #if portspec != -1: - # servername = servername[:portspec] + servername = host realm = cprinc.realm service = self.opts.get('krbservice', 'host')
This bug appears to have been reported against 'rawhide' during the Fedora 28 development cycle. Changing version to '28'.
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This code does not change the host name that Koji connects to. This function, _serverPrincipal(), is used to determine which Kerberos principal that we generate our auth request for. This is done to handle situations where the server url uses a cname, but the hub's principal is using the actual host name. This behavior is controllable via the `krb_rdns` and `krb_canon_host` options. So, you can turn these off if you don't like them. It is also only used in the older kerberos auth path. The newer gssapi auth path for kerberos does not do this (though note that krb itself has a dns_canonicalize_hostname option that defaults to true). Koji is not using kerberos to validate the server, but only to authenticate. Koji uses ssl to validate the server, and nothing in this function will affect that.
Hopefully that answers the questions about this? If there's any further ones, please open an upstream ticket for faster reply.