Our initiator supports configuration-driven delegation of destination
TGTs.
This commit adds acceptor-side handling of destination TGT policy to
reject storing of non-destination TGTs when destination TGTs are
desired.
Currently we use the same appdefault for this.
Background:
A root TGT is one of the form krbtgt/REALM@SAME-REALM.
A destination TGT is a root TGT for the same realm as the acceptor
service's realm.
Normally clients delegate a root TGT for the client's realm.
In some deployments clients may want to delegate destination TGTs as
a form of constrained delegation: so that the destination service
cannot use the delegated credential to impersonate the client
principal to services in its home realm (due to KDC lineage/transit
checks). In those deployments there may not even be a route back to
the KDCs of the client's realm, and attempting to use a
non-destination TGT might even lead to timeouts.
This is needed so that sshd and such can get make practical use of the
"ccache" key in GSS cred stores.
This commit only changes the store path, not the acquisition path.
gss_store_cred_into*() will now switch the new cred cache to be the
primary/default cred cache when
- the caller requested it and,
- if the caller passed in a user name, the creds' principal is the best
principal for the named user.
A principal is the best principal for a user when the principal has just
one component, the component is the user's username, and the realm is
the configured user_realm.
- Formalize the TYPE:collection_name:subsidiary_name naming scheme for
ccaches in ccache collections
- KEYRING: ccaches are weird because they have one more optional field: the
"anchor", so rather than just assume a naming convention everywhere, we
add new functions as well
- Add krb5_cc_{resolve,default}_sub() that allows one to specify a
"subsidiary" ccache name in a collection separately from the
collection name
- Add krb5_cc_{resolve,default}_for() which take a principal name,
unparse it, and use it as the subsidiary ccache name (with colons
replaced)
- Make kinit use the new interfaces
- Add missing DIR ccache iteration functionality
- Revamps test_cc
- Add krb5_cc_get_collection() and krb5_cc_get_subsidiary()
- Bump the ccops SPI version number
- Add gss_store_cred_into2()
- Make MEMORY:anonymous not linked into the global MEMORY ccache
collection, and uses this for delegated cred handles
TBD:
- Split this up into a krb5 change and gss mech_krb5 change?
- Add krb5_cc_init_and_store() utility, per Greg's suggestion?
krb5_cc_cache_match() searches all ccache collections for a ccache that
has credentials for a given principal name. This includes MEMORY
ccaches, which means it can find the same ccache as is referenced by a
GSS cred handle given to gss_store_cred(), which means that
gss_store_cred() can fail.
For now we work around this by including a private variant of
krb5_cc_cache_match() that only searches the default ccache, not all
collections. Eventually we should ensure that krb5_cc_default() also
searches all collection-type (other than MEMORY) ccaches for a default
credential, then we can go back to using krb5_cc_cache_match() (though
we'll need to make sure that MEMORY is searched last or not at all).
Implement the GSS-API credential store API extensions defined by MIT here:
https://k5wiki.kerberos.org/wiki/Projects/Credential_Store_extensions
Note: we kill off gss_acquire_cred_ext() here. This was never a public API,
although mechanisms could have implemented it and I briefly used it in my
BrowserID prototype mechanism. gss_acquire_cred_ext_from() occupies the place
in the dispatch table where gss_acquire_cred_ext() used to, but this structure
was never visible outside Heimdal (i.e. it is only used by internal
mechanisms);
(Mechanisms that need to accept arbitrary key/value dictionaries from
applications should now implement gss_acquire_cred_from().)
