Sorry for the spam, but after continuing to investigate, it looks like this
database shortcut only works for vertical trusts. A
krbtgt/a.viasat...@b.viasat.io principal only shows up in the realm it’s
created in. That definitely pushes me toward the “unintended/bug” end of the
spectrum, because otherwise the interface wouldn’t be uniform.
Stephan Kemper
ViaSat, Inc.
On 1/22/17, 12:42 PM, "Kemper, Stephan" <stephan.kem...@viasat.com> wrote:
Hello again!
Based on my previous question (“Cross-Realm Admins” from last month) we’re
now using a model with separate admin principals per realm, and a large keyring
of keytab files. This seems to be working *mostly* fine.
Where we run into issues is with creating the cross-realm trusts,
specifically one-way trusts with a sub-realm trusting our master realm. When
our automation tries to create the trust, it often fails with the following log
messages:
KerberosService - Running [kadmin, -r, A.VIASAT.IO, -p,
api/ad...@a.viasat.io, -kt, /path/to/keytab-A.VIASAT.IO, -q, add_principal -pw
**random stuff** krbtgt/a.viasat...@viasat.io]
WARNING: no policy specified for krbtgt/a.viasat...@viasat.io; defaulting
to no policy
Authenticating as principal api/ad...@a.viasat.io with keytab
/path/to/keytab-A.VIASAT.IO.
Principal "krbtgt/a.viasat...@viasat.io" created.
KerberosService - Running [kadmin, -r, VIASAT.IO, -p, api/ad...@viasat.io,
-kt, /path/to/keytab-VIASAT.IO, -q, add_principal -pw **the same random stuff**
krbtgt/a.viasat...@viasat.io]
WARNING: no policy specified for krbtgt/a.viasat...@viasat.io; defaulting
to no policy
add_principal: Principal or policy already exists while creating
"krbtgt/a.viasat...@viasat.io".
Authenticating as principal api/ad...@viasat.io with keytab
/path/to/keytab-VIASAT.IO.
The principals do not exist before this point, I am 100% certain. In our
system, all realms are backed by the same LDAP database, under the container
cn=Kerberos,dc=viasat,dc=io. So we have separate krbRealmContainer objects
cn=VIASAT.IO, cn=A.VIASAT.IO, and so on. What’s happening, based on my manual
duplication of these steps, is that the A.VIASAT.IO version of the principal is
somehow “spilling over” into VIASAT.IO. After diving into the code, it appears
this behavior is intentional: is_principal_in_realm() in ldap_misc.c explicitly
allows these cross-realm TGS principals, no matter which krbRealmContainer
they’re in.
So I have two questions: first, is this behavior truly expected, or is
there some kind of bug here? It seems like a nice shortcut, but I want to make
sure either way before we start depending on it in production. Second, if it
is expected, it’d be really nice for this feature to be documented. Is it OK
if I send in a pull request on GitHub, or some other patch for the docs to
reflect this?
Thanks,
Stephan Kemper
ViaSat, Inc.
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