This commit adds support for kx509 in libkrb5, and revamps the KDC's
kx509 service (fixing bugs, adding features).
Of note is that kx509 is attempted optimistically by the client, with
the certificate and private key stored in the ccache, and optionally in
an external PEM or DER file.
NOTE: We do not optimistically use kx509 in krb5_cc_store_cred() if the
ccache is a MEMORY ccache so we don't generate a key when
accepting a GSS context with a delegated credential.
kx509 protocol issues to be fixed in an upcoming commit:
- no proof of possession (this is mostly not too bad, but we'll want to
fix it by using CSRs)
- no algorithm agility (only plain RSA is supported)
- very limited (no way to request any options in regards to the
requested cert)
- error codes are not very useful
Things we're adding in this commit:
- libkrb5 kx509 client
- automatic kx509 usage hooked in via krb5_cc_store_cred() of start TGT
- per-realm templates on the KDC side
- per-realm issuer certificates
- send error messages on the KDC side
(this is essential to avoid client-side timeouts on error)
- authenticate as many error messages
- add a protocol probe feature so we can avoid generating a
keypair if the service is not enabled
(once we add support for ECC algorithms we won't need this
anymore; the issue is that RSA keygen is slow)
- support for different types of client principals, not just username:
- host-based service and domain-based service, each with its own
template set per-{realm, service} or per-service
(the idea is to support issuance of server certificates too, not
just client/user certs)
- more complete support for SAN types
- tests (including that PKINIT->kx509->PKINIT works, which makes it
possible to have "delegation" of PKIX credentials by just delegating
Kerberos credentials)
- document the protocol in lib/krb5/kx509.c
Future work:
- add option for longer-ticket-lifetime service certs
- add support for ECDSA, and some day for ed25519 and ed448
- reuse private key when running kinit
(this will require rethinking how we trigger optimistic kx509
usage)
- HDB lookup for:
- optional revocation check (not strictly necessary)
- adding to certificates those SANs listed in HDB
- hostname aliases (dNSName SANs)
- rfc822Name (email)
- XMPP SANs
- id-pkinit-san (a user could have aliases too)
- support username wild-card A RRs, ala OSKT/krb5_admin
i.e., if a host/f.q.d.n principal asks for a certificate for
some service at some-label.f.q.d.n, then issue it
(this is not needed at OSKT sites because OSKT already
supports keying such service principals, which means kx509
will issue certificates for them, however, it would be nice
to be able to have this independent of OSKT)
(a better way to do this would be to integrate more of OSKT
into Heimdal proper)
- a kx509 command, or heimtools kx509 subcommand for explicitly
attempting use of the kx509 protocol (as opposed to implicit, as is
done in kinit via krb5_cc_store_cred() magic right now)
Issues:
- optimistically trying kx509 on start realm TGT store -> timeout issues!
- newer KDCs will return errors because of this commit; older ones
will not, which causes timouts
- need a separate timeout setting for kx509 for optimistic case
- need a [realm] config item and DNS SRV RR lookup for whether a
realm is expected to support kx509 service
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().)
Solaris make won't allow @echo in a shell command string as there is no
command called @echo, and it passes the whole shell command to the shell
without poaching off the @ itself first
This is part of the fix to #173. MSFT RODCs insist on the name type for
krbtgt principals be set to KRB5_NT_SRV_INST.
Commentary from Jeffrey Altman <jaltman@secure-endpoints.com>
As reported by David Mulder of Dell's Quest, Active Directory will
return a BAD_INTEGRITY error when a request for a krbtgt service
ticket is received with principal type NT-PRINCIPAL instead of NT-SRV-INST
as required by RFC 4120.
[Nico: RFC4120 does not require this. See the description of the
name-type field of PrincipalName on page 55.]
ERROR: VAS_ERR_KRB5: Failed to obtain credentials.
Client: SLED10-32$@F.QAS,
Service: SLED10-32$@F.QAS, Server: ad2-f.f.qas
Caused by: KRB5KRB_AP_ERR_BAD_INTEGRITY (-1765328353): Decrypt integrity check failed
Microsoft began enforcing principal type checking for RODCs in 2008R2.
Microsoft does state that ALL krgtgt/REALM tickets SHOULD be sent using
principal name type of KRB5_NT_SRV_INST instead of KRB5_NT_PRINCIPAL.
From Microsoft:
"I believe we discovered the problem. There isn't a bug in Windows.
There's been a code change to address another issue which puts in additional
checks for Kerberos tickets. The problem is with the Unix clients when the
client request a TGT. The Unix clients are using Name-type Principal
[KRB_NT_PRINCIPAL (1)] instead of using Name-type Service and Instance
[KRB_NT_SRV_INST (2)]...."
This change assigns the NT-SRV-INST principal type each time a krbtgt
service principal is created. Unlike Microsoft, the Heimdal mostly does
not care about the name-type of any principals, with the exception of
referrals, where the name type is needed to decide how to find a
next-hop realm.
Bugs exposed by 61720a0:
- test_context --client-name=... --mech-type=ntlm ... fails;
- gss_acquire_cred() with desired_mech=NTLM and
desired_name==GSS_C_NO_NAME fails;
- gss_init_sec_context() with non-default cred handle calls the
mechanism even when the given cred handle has no element for the
requencet mechanism.
tests/gss/check-ntlm works by accident: gss_acquire_cred() with
desired_mechs==GSS_C_NO_OID_SET succeeds mostly because there are
Kerberos credentials available, and then the subsequent
gss_init_sec_context() call works because of the third bug described
above.
Put kdc last in tests/Makefile.am. There's two tests in tests/kdc
that have been failing for a long time, and that causes the
remaining tests to not be run. By putting kdc last those tests do
run.
Works for krb5 and SPNEGO mechanisms. Kerberos credentials are passed as
credential cache names, or if there are memory based credentials, inband in the protocol. This means that the credentials buffers must be keep secret.
As documented by IBM (they have the wrong prototype though)
and GGF (GSS-API Extensions) back in 2001
