On 21/05/2024 13.11, Djerk Geurts wrote:
Thank you, that’s really helpful, especially how to test.
For the 3CX service I do indeed need to add the GSS_USE_PROXY=yes, but
as a side note, I’ll need to work out which service needs it as there
are many daemons that make up 3CX. Anyway, this is on my todo list.
What I need to do first is create a Service Principal for this service
to use. The GSS proxy config references the local uid, but how does it
match the SPN? I guess I’m not clear on the service name as the host
and REALM parts are straight forward. Is the username used for this?
If so the SPN should be phonesystem/FQDN@REALM, as the uid is a
number, so can I assume that the local machine uses the local account
name belonging to the uid for this?
GSS-Proxy uses the power of Unix sockets. "GSS_USE_PROXY=yes" enables
the interposer library in the client. When the interposer intercepts
some GSS-API calls and forwards them to GSS-Proxy's Unix domain socket.
The proxy daemon uses getsockopt() with SO_PEERCRED to get the euid and
egid of the client from the Linux Kernel. In your case, it maps euid 998
to "service/3CXPBX" and "3cxpbx.keytab". In client keytab mode,
GSS-Proxy then uses the SPN of the first keytab slot. The keytab
contains the SPN:
# ktutil
ktutil: rkt /var/lib/ipa/gssproxy/http.keytab
ktutil: l
slot KVNO Principal
---- ----
1 1 HTTP/server.ipa-hcc.test@IPA-HCC.TEST
2 1 HTTP/server.ipa-hcc.test@IPA-HCC.TEST
3 1 HTTP/server.ipa-hcc.test@IPA-HCC.TEST
4 1 HTTP/server.ipa-hcc.test@IPA-HCC.TEST