URL: https://github.com/freeipa/freeipa/pull/5213 Author: abbra Title: #5213: rpcserver: fallback to non-armored kinit in case of trusted domains Action: opened

PR body: """ MIT Kerberos implements FAST negotiation as specified in RFC 6806 section 11. The implementation relies on the caller to provide a hint whether FAST armoring must be used.

FAST armor can only be used when both client and KDC have a shared secret. When KDC is from a trusted domain, there is no way to have a shared secret between a generic Kerberos client and that KDC.

[MS-KILE] section 3.2.5.4 'Using FAST When the Realm Supports FAST' allows KILE clients (Kerberos clients) to have local settings that direct it to enforce use of FAST. This is equal to the current implementation of 'kinit' utility in MIT Kerberos requiring to use FAST if armor cache (option '-T') is provided.

[MS-KILE] section 3.3.5.7.4 defines a way for a computer from a different realm to use compound identity TGS-REQ to create FAST TGS-REQ explicitly armored with the computer's TGT. However, this method is not available to IPA framework as we don't have access to the IPA server's host key. In addition, 'kinit' utility does not support this method.

Active Directory has a policy to force use of FAST when client advertizes its use. Since we cannot know in advance whether a principal to obtain initial credentials for belongs to our realm or to a trusted one due to enterprise principal canonicalization, we have to try to kinit. Right now we fail unconditionally if FAST couldn't be used and libkrb5 communication with a KDC from the user realm (e.g. from a trusted forest) causes enforcement of a FAST.

In the latter case, as we cannot use FAST anyway, try to kinit again without advertizing FAST. This works even in the situations when FAST enforcement is enabled on Active Directory side: if client doesn't advertize FAST capability, it is not required. Additionally, FAST cannot be used for any practical need for a trusted domain's users yet.

Signed-off-by: Alexander Bokovoy abokovoy@redhat.com """

To pull the PR as Git branch: git remote add ghfreeipa https://github.com/freeipa/freeipa git fetch ghfreeipa pull/5213/head:pr5213 git checkout pr5213