Heimdal 1.5 and 1.5.1

Release Notes - Heimdal - Version Heimdal 1.5

New features

 - Support GSS name extensions/attributes

 - SHA512 support

 - No Kerberos 4 support

 - Basic support for MIT Admin protocol (SECGSS flavor)

   in kadmind (extract keytab)

 - Replace editline with libedit

Release Notes - Heimdal - Version Heimdal 1.5.1

 Bug fixes
 - Fix building on Solaris, requires c99
 - Fix building on Windows
 - Build system updates


http://www.h5l.org/dist/src/heimdal-1.5.1.tar.gz

Heimdal 1.4

Release Notes - Heimdal - Version Heimdal 1.4

 New features

 - Support for reading MIT database file directly
 - KCM is polished up and now used in production
 - NTLM first class citizen, credentials stored in KCM
 - Table driven ASN.1 compiler, smaller!, not enabled by default
 - Native Windows client support

Notes

 - Disabled write support NDBM hdb backend (read still in there) since
   it can't handle large records, please migrate to a diffrent backend
   (like BDB4)

Heimdal 1.3.0 and 1.3.1

It was over a year ago last release was made, today we have published 1.3.1. We already released 1.3.0 last week but was never announced it.

Here is summary of change that included in the release:

Major changes in 1.3.1

• Make work with OpenLDAPs krb5 overlay

Major changes in 1.3.0

• Partial support for MIT kadmind rpc protocol in kadmind


• Better support for finding keytab entries when using SPN aliases in the KDC


• Support BER in ASN.1 library (needed for CMS)


• Support decryption in Keychain private keys


• Support for new sqlite based credential cache


• Try both KDC referals and the common DNS reverse lookup in GSS-API


• Fix the KCM to not leak resources on failure


• Add IPv6 support to iprop


• Support localization of error strings in


• kinit/klist/kdestroy and Kerberos library


• Remove Kerberos 4 support in application (still in KDC)


• Deprecate DES


• Support i18n password in windows domains (using UTF-8)


• More complete API emulation of OpenSSL in hcrypto


• Support for ECDSA and ECDH when linking with OpenSSL

There are more changes in the patch train, and I assume that you all don't have to wait other year before 1.4 gets out

Release Notes - Heimdal - Version Heimdal 1.3.1

Bug fixes

- Make work with OpenLDAPs krb5 overlay

Release Notes - Heimdal - Version Heimdal 1.3

New features

- Partial support for MIT kadmind rpc protocol in kadmind

- Better support for finding keytab entries when using SPN aliases in the KDC

- Support BER in ASN.1 library (needed for CMS)

- Support decryption in Keychain private keys

- Support for new sqlite based credential cache

- Try both KDC referals and the common DNS reverse lookup in GSS-API

- Fix the KCM to not leak resources on failure

- Add IPv6 support to iprop

- Support localization of error strings in

kinit/klist/kdestroy and Kerberos library

- Remove Kerberos 4 support in application (still in KDC)

- Deprecate DES

- Support i18n password in windows domains (using UTF-8)

- More complete API emulation of OpenSSL in hcrypto

- Support for ECDSA and ECDH when linking with OpenSSL

API changes

- Support for settin friendly name on credential caches

- Move to using doxygen to generate documentation.

- Sprinkling __attribute__((depricated)) for old function to be removed

- Support to export LAST-REQUST information in AS-REQ

- Support for client deferrals in in AS-REQ

- Add seek support for krb5_storage.

- Support for split AS-REQ, first step for IA-KERB

- Fix many memory leaks and bugs

- Improved regression test

- Support krb5_cccol

- Switch to krb5_set_error_message

- Support krb5_crypto_*_iov

- Switch to use EVP for most function

- Use SOCK_CLOEXEC and O_CLOEXEC (close on exec)

- Add support for GSS_C_DELEG_POLICY_FLAG

- Add krb5_cc_[gs]et_config to store data in the credential caches

- PTY testing application

Bugfixes

- Make building on AIX6 possible.

- Bugfixes in LDAP KDC code to make it more stable

- Make ipropd-slave reconnect when master down gown

Using krb5_cc_[gs]et_config

Or how everything turned into a nail

Maybe this should be titled, how everything turned into a nail when I got a hammer. There are a couple of use cases I want to discuss first, and then why krb5_cc_[gs]et_config() isn't useable for everything.

First out is Windows, you just talked to a Windows AD KDC to get your TGT, but you need to do slight tweeks to make it work better on
Windows, so turn on insecure^HWindows behavior when we use this this credential cache. We make it up with a global setting using krb5_cc_[sg]_config().

Next thing that comes is negative caching of TGS requests (fetching service tickets). Now this seems very stupid to do, but for practical reason is not.

If you want to use HTTP Negotiate and have it default turned on in you http client, you can get bad behaviors in case of the webserver announces support for Negotiate and the client can't get service tickets for that realm. You don't want to have the performance loss of having to ask the KDC over and over again for the same ticket that you can't get.

The the state HTTP negotiate doesn't work should probably be in the http client instead, but sometimes that not possible, just think of running curl in a shell script and looping a couple of times, when you are tired enough of DNS timeouts, not answering KDC, referrals that doesn't lead anywhere, etc, you can let me know.

Third problem is ticket forwarding, it will get you into the same problem. If you want to do a lot of forwarding of your ticket, again maybe because of HTTP Negotiate, then you don't want to hit the KDC for every request. Again we can use krb5_cc_[gs]et_config to store the
forwarding credential for this entry.

So when is krb5_cc_[gs]et_config not useful

So when you renew your credentials you loose all your state, so if you want to keep your state you better store it somewhere else. So that said, having the Windows behavior flag in the krb5_cc_[gs]et_config is probably not good idea. There needs to be somewhere else that this kind of information is stored.

The use of of gss_accept_sec_context (ASC)

This is continuation of the previous article about ISC.

The gssapi function ASC (gss_accept_sec_context) is also complicated,
function, one can argue ASC is simpler then ISC since ASC only takes
11 arguments.

OM_uint32
gss_accept_sec_context
           (OM_uint32 * /*minor_status*/,
            gss_ctx_id_t * /*context_handle*/,
            const gss_cred_id_t /*acceptor_cred_handle*/,
            const gss_buffer_t /*input_token_buffer*/,
            const gss_channel_bindings_t /*input_chan_bindings*/,
            gss_name_t * /*src_name*/,
            gss_OID * /*mech_type*/,
            gss_buffer_t /*output_token*/,
            OM_uint32 * /*ret_flags*/,
            OM_uint32 * /*time_rec*/,
            gss_cred_id_t * /*delegated_cred_handle*/
           );

Again, just like ISC the main problem is that consumers if this interface tries to pass in too much information, less is usually better.

Not passing in a credential

If consumers instead of passing a credential checked the name afterward it would work in more situations. For example, using the GSSAPI Kerberos mech as an acceptor: when the client connects the server doesn't know what name the client used, and if the server specifies a credential (thus an implicitly a name) the client have selected another name, ASC will fail.

Do when do server and client not patch up on names ? There are plent of examples, where: HTTP/www, http/www.example.com is the one to start with. Kerberos is case sensitive and client might expect aliases to work.

The logic flow for ASC

The flow of a server part of gss-api negotiation looks like this:

in = null;
do {
   ret = gss_accept_sec_context(in, out);
   if (GSS_ERROR(ret))
      abort();
  send_message(out);
  if (ret == GSS_C_CONTINUE)
      in = read_message();
} while (ret == GSS_C_CONTINUE);

if (check_return_flags())
   abort();

if (check_that_name_is_ok(ctx))
   abort();

/* done */

Cross compiling Heimdal

We got some feedback that it would be good if it was possible to cross compile Heimdal and with some minor works that is now possible.

Its all documented at http://www.h5l.org/compile.html#cross, as usual libtool is somewhat in the way. The current problem that that libtool is not aware of the target's build environment, but it seems to work anyway. Oh well.

The code is all patch of master and will be in the soon to be release Heimdal 1.3.

The use of of gss_init_sec_context (ISC)

ISC

Lets start to dissect some of the GSS-API functions, first out in gss_init_sec_context (ISC for short).

The gssapi function ISC is a very complicated function, just look at the 13 arguments it takes, and for every round its call in an authentication some of them need to be same, and some need to change.

OM_uint32
gss_init_sec_context
           (OM_uint32 * /*minor_status*/,
            const gss_cred_id_t /*initiator_cred_handle*/,
            gss_ctx_id_t * /*context_handle*/,
            const gss_name_t /*target_name*/,
            const gss_OID /*mech_type*/,
            OM_uint32 /*req_flags*/,
            OM_uint32 /*time_req*/,
            const gss_channel_bindings_t /*input_chan_bindings*/,
            const gss_buffer_t /*input_token*/,
            gss_OID * /*actual_mech_type*/,
            gss_buffer_t /*output_token*/,
            OM_uint32 * /*ret_flags*/,
            OM_uint32 * /*time_rec*/
           );

In that 13 that lays the confusion, to make make ISC work you only need to pass in 7 arguments, you can leave the other 6 to a default values, in fact, this will probably make it work better in most cases.

gss_init_sec_context(&minor_status, GSS_C_NO_CREDENTIAL, &ctx, &target_name, GSS_C_NO_OID,
    GSS_C_MUTUAL_FLAG, GSS_C_INDEFINITE, GSS_C_NO_CHANNEL_BINDINGS, &in, NULL, &out, &ret_flags, NULL);

You need to check that ret_flags is what you wanted in flags, the reason is that the server might downgarde your security to a level you don't find acceptiable, like no encryption (leaving out GSS_C_CONF_FLAG).

The logic flow for ISC

The flow of a client part of gss-api negotiation looks like this:

name = gss_import_name("service@server", GSS_C_NT_HOSTBASED_SERVICE);

if (client_name && client_name_type) {
   cname = gss_import_name(client_name, client_name_type);
   cred = gss_acquire_cred(cname, GSS_C_INITIATE);
} else
   cred = NULL;

in = null;
do {
   ret = gss_init_sec_context(in, out);
   if (GSS_ERROR(ret))
      abort();
  send_message(out);
  if (ret == GSS_C_CONTINUE)
      in = read_message();
} while (ret == GSS_C_CONTINUE);

if (check_return_flags())
   abort();

/* done */

Next out is gss_accept_sec_context (ASC)

ASC is the awesome function, mostly every time we have to fix 3rd party code that uses ASC the resolution is mostly always to remove code

Support for ECDSA and ECDH in PK-INIT

Heimdal now support support for ECDSA (Elliptic curve, signature mode) and ECDH (Elliptic curve, key exchange mode) when compiled with OpenSSL, no hcrypto support yet. Using ECDSA is turned on when using EC certificates, both the signature verification and CMS is done using EC certificate.

ECDH is turned used when using ECDSA, so also its also used when using EC certificates on the client. There is missing negotiation of EC curves, so the code is not future safe, but its something that we'll add in the future.  Part of the regression test now uses the EC certificate. hxtool needs support for generating EC keys and exporting the SubjectPublicKeyInfo before its can sign certificates, neither of them too hard.

Too much of the OpenSSL EC implementation is hidden, so right now its not possible to load plugins. So no support for PKCS11 or Keychain based private keys.

New PKINIT bits, anonymous and enterprise support

I've just added anonymous Kerberos/pkinit to the KDC and the client libraries. Still only AS-REQ, what is missing is TGS-REQ and GSS-API support.

kinit --anonymous REALM

What have been implemented is draft-ietf-krb-wg-anon-04.

At the same time support for enterprise names when using PK-INIT slipped it. This is very cool, just point a cert, and the kinit will search the cert for a windows nt-name, use that with a client referrals (enterprise name) and return you a ticket for your real principal name. The only problem is that right now windows 2008 DC doesn't return client referrals PA-DATA, so that why we use --windows in the example below, it disable the client check.

kinit --windows --pk-enterprise --canon -C FILE:w2k8.pem WINDOWS2008.DOMAIN

The implementation show that the krb5_get_init_creds and friends need to be more aware PK-INIT and certificate selection. The reason the interface look the way it does is to avoid exposing that we are using hx509 beneath the kerberos library. So far I've not come up with a good langauge to express what certificate to select.

There is a query language in hx509, but its not something that you want to expose users too. Here are some examples:

%{certificate.issuer} == "C=SE,CN=hx509 Test Root CA"
%{certificate.subject} TAILMATCH "C=SE"
%{certificate.hash.sha1} EQ "412120212A2CBFD777DE5499ECB4724345F33F16"

Heimdal will show up for the Interop event in Redmond at the end of March, part of that we will do PK-INIT testing.

One things that really should be working by the is support for EC certificate and ECDSA, right now that support it not there in hx509 or hcrypto.

Setting up PK-INIT with Heimdal

Setting up Heimdal with PK-INIT is very easy. Heimdal by itself contains all the tools so you can do the setup. We assume that you don't have CA when we do the setup.

Some facts

The realm name we are going to use is EXAMPLE.ORG, the kdc is named kdc.example.org, the user is user@EXMAPLE.ORG.

Create the certificates needed

First we create the CA certificate. The create file ca.pem contains both private key and the certificate, you should make sure the private key is removed when distributing the certificate to clients and the KDC.

hxtool issue-certificate \
          --self-signed \
          --issue-ca \
          --generate-key=rsa \
          --subject="CN=CA,DC=example,DC=org" \
          --certificate="FILE:ca.pem"

Then the user's certificate, here we add the PK-INIT options for a
PK-INIT client.

hxtool issue-certificate \
          --ca-certificate=FILE:ca.pem \
          --generate-key=rsa \
          --type="pkinit-client" \
          --pk-init-principal="user@EXAMPLE.ORG" \
          --subject="cn=user,DC=example,DC=org" \
          --certificate="FILE:user.pem"

Last we create the KDC's certificate, here we add the PK-INIT options
for a PK-INIT client.

hxtool issue-certificate \
          --ca-certificate=FILE:ca.pem \
          --generate-key=rsa \
          --type="pkinit-kdc" \
          --pk-init-principal="krbtgt/EXAMPLE.ORG@EXAMPLE.ORG" \
          --subject="cn=kdc,DC=example,DC=org" \
          --certificate="FILE:kdc.pem"

Creating the database

Just for completeness we are including the setup of your KDC here

kadmin -l -r EXAMPLE.COM
kadmin> init EXAMPLE.ORG

Lets add our user to the database.

kadmin> add user
kadmin> modify --pkinit-acl=cn=user,DC=example,DC=org --attribute=+requires-pre-auth user

That all that needs to do to create the database and set up the user.

Setting up the KDC configuration

All KDC configuration is stored in /etc/krb5.conf (or /var/heimdal/kdc.conf), the content should contain this:

[kdc]
	enable-pkinit = true
	pkinit_identity = FILE:kdc.pem
	pkinit_anchors = FILE:ca.pem

Start the KDC

Start the KDC

/usr/heimdal/libexec/kdc --detach

Get tickets using PK-INIT

First we need to configure the trust anchors (what certificate authorities) to trust for the client.

[appdefaults]
	pkinit_anchors = FILE:ca.pem

Now we can get the ticket.

kinit -C FILE:user.pem user@EXAMPLE.COM

Fetching tickets over EAP

Or how to talk to the Kerberos KDC over your appliation protocol

Talking to the KDC with no network

Sometimes you want to talk to the KDC when there is limited or direct network. Or your application simply knows better how to communicate with the KDC.

For example, if it was possible to use EAP with GSS-API so it run Kerberos initial ticket fetching over the EAP channel, this is not so far off given the new IAKERB gss-api mechanism that Larry Zhu is proposing (currently in last call). With his mechanism you can talk to the KDC and get initial and service tickets for a service over a gss-api channel.

First the when you login to the network using EAP the network topology looks like this:

Client ---[EAP over wavelan]---> Wavelan access point ---[radius]---> Radius server

First you authenticate to the radius server, and the radius server tells the access point to let you out on the network, and then you get a IP address from the DHCP server. So why doesn't this fit together with the Kerberos stack.

In the classial appliation the world looks like this:

Application -> GSS-API -> Kerberos mechanism <--[Kerberos protocol]--> KDC
                 |
              [token]
                 |
  appl <---------/
   |
   |
   \
    ------[application protocol]---->  server

But when you are in an about to use EAP to login to the network, theKerberos mechanism have no way to talk to the KDC, the only channel you have EAP the channel to the Radius server.

So the obvious solution is to let the Kerberos mechanism talk though the EAP channel over the the Radius server, and have the radius server forward over the packets over the the KDC.

The problem with Kerberos krb5_get_init_creds()

The Kerberos function krb5_get_init_creds() is that it expect to be able to resolve the DNS information to the KDC and then talk to the KDC to get initial tickets, so deep inside the function there is a function that will send of a packet the the KDC.

As described above, this wont work since the Kerberos library have no network connection to the KDC, it have to talk to the KDC thought the GSS-API layer.

The replacement function, krb5_init_creds()

So the new function krb5_init_creds() and krb5_init_creds_step() instead of sending of the packet to the KDC, return the packet that is supposed to be sent off to the KDC, and the expect the caller to call
krb5_init_creds_step() with whatever the KDC returned. There is a helper function that does all this: krb5_init_creds_get().

So krb5_get_init_creds_password() is now implmented in terms of the new functions. And is as described below.

krb5_get_init_creds_password()
{
   krb5_init_creds_init(&ctx);
   krb5_init_creds_get(ctx);
   krb5_init_creds_free(ctx);
}

krb5_init_creds_get(ctx)
{
    while(1) {
       ret = krb5_init_creds_step(ctx,inpacket, &outpacket);
       if (ret != CONTINUE)
         break;
       krb5_send_to_kdc(outnpacket, &inpacket);
    }
}

GSS-API usage of krb5_init_creds_step()

This way GSS-API mech can take advantage of the split stack and instead of sending the packet to the KDC, send of the packet over to GSS-API peer and when it get back the reply, stuff the answer back into krb5_init_creds_step() to continue the dance. 

Application -> GSS-API <--> Kerberos mechanism

                 |
              [token]
                 |
  appl <---------/
   |
   |
   \
    ------[application protocol]---->  server <--[Kerberos protocol]--> KDC

Now, someone just need to implement IAKERB to use this functionallity.

The krb5-cc-[gs]et-config API

I've created a new API to the krb5_ functions, its for storing Kerberos related data in the credential cache.

• Realm configuration that is fetched runtime, for that the target is a domain that only should have Kerberos canonlization done and not dns canonlization


• Forwarded tickets, to avoid re-fetching the from the KDC

krb5_cc_get_config
krb5_is_config_principal
krb5_cc_set_config

There is a patch for MIT Kerberos that also includes this interface, so hopefully it will be included in MIT Kerberos 1.7.

ok-as-delegate and GSS-API

Background

To forward your Kerberos credential from a gss-api client to a server you turn on the flag GSS_C_DELEG_FLAG. This will, as part of the authentication, forward your tickets to the server.

The problem is that you don't want to turn on this just for every server your what to authenticate to, because most of them should probably not be trusted with your tickets.

To solve this Microsoft added an extention to the Kerberos, that was added to RFC4120 (The Kerberos protocol RFC). The extention is called ok-as-delegate and is a ticket flag. Using the flag the client can determine that the system administrator thinks about the host, if it should be delegated too or not.

Non Microsoft sites have been using GSS-API implementations that doesn't honor the flag ok-as-delegate and most of them never has set the ok-as-delegate flag. In some cases the sites are using Kerberos implementations that doesn't even support setting the ok-as-delegate flag in the Kerberos database.

Users at these sites have grown accustomed to the behavior ok GSS_C_DELEG_FLAG and changing the GSS-API implementation behind them to make GSS_C_DELEG_FLAG honor the ok-as-delegate flag will only make people upset.

New flag

What we can do it introduce a new flag GSS_C_DELEG_POLICY_FLAG that is defined to honor the flag ok-as-delegate.

The flag GSS_C_DELEG_POLICY_FLAG is a local flag that is never seen on the wire. And, its only used by the initator, the acceptor never see the flag.

There are four cases where GSS_C_DELEG_POLICY_FLAG and GSS_C_DELEG_FLAG interact with each other and the resulting return flags.

• Neither flag set
  do nothing with regard to delegation


• GSS_C_DELEG_FLAG set
  always try go delegate and set GSS_C_DELEG_FLAG in the return flags if successful


• GSS_C_DELEG_POLIY_FLAG set
  try to delegate if ok-as-delegate is set, delegate and set GSS_C_DELEG_FLAG and GSS_C_DELEG_POLICY_FLAG in the return flags if successful


• GSS_C_DELEG_FLAG and GSS_C_DELEG_POLIY_FLAG setalways try to delegate, set GSS_C_DELEG_FLAG if successful in the return flags if successful. Also, if successful and ok-as-delegate was set on the service ticket, set GSS_C_DELEG_POLICY_FLAG in the return flags.

Cross realm ?

What is missing is how ok-as-delegate and GSS_C_DELEG_POLICY_FLAG should work in the cross realm case. RFC4120 is quiet on this issue, the flag on ok-as-delegate doesn't mean anything on the cross realm tgt. The question is how this should be dealt with.

The obvious answer is define a meaning on the cross realm tgt ticket for ok-as-delegate, but how will that interact with existing deployments.

Current behavior is for released MIT and heimdal is that the flag is ignored. For Microsoft clients is that they honor the flag for windows domains, and to external realms they allow delegation is a flag is set on the realm configuration on the client.

Any good ideas out there ?

DES will die in Heimdal 1.3

A long long time ago DES was standardized (1973, before I was born). Some 30 years later (2003) is was withdrawn as a standard by NIST, today 5 years later, its time for DES to finally die. Last year you could brute force DES in 6.4 days by buying a machine for $10000. So last year was the time for you to migrate to better encryption types for your Kerberos realm.

If you really are in love with DES and can't stand to be without it, now its the time to add "[libdefaults] allow_weak_crypto = true"to your configuration file so that your love wont die when you upgrade next time. If you want to check your configuration, the code is already commited to trunk in the source repro.

Application that will stop working are old Kerberos 4 tools and telnet/telnetd.

Heimdal-1.3 will deprecate DES

PS there is an exception for AFS to allow it still to use DES encryption types.

Do you want Heimdal to speak Swedish to you ?

As part of Heimdal 1.3 we have been adding i18n support to the base libraries and some of the Kerberos user utilites using GNU Gettext. It should also work with other localization packages like the MacOS X CoreFoundation's CFCopyLocalizedString with some minor code hacking.

We that work on Heimdal only know Swedish and English, so can can help translate the error strings. You don't need to download special tool, just go to Heimdal at launchpad and you translate the strings there. Just let us know that you have started to do the work so that we will remember to download your translations before release (or when you want to sync to you can test how it feels to get heimdal in your language.

Adding support for referrals in GSS-API

We can implement referrals support for Kerberos mk_req API or do it for GSS-API. For me its an easy choice, most consumers uses GSS-API, lets go for that.

DNS canonicalition happens when we pass in a GSS_C_NT_HOSTBASED_SERVICE based name into gss_import_name(), so its only that case we really need to care about. DNS canonlisation is done by krb5_sname_to_principal(), see documentation in Heimdal trunk.

The simple solution is that in gss_import_name() we the hostname to krb5_sname_to_principal(), instead we mark up the principal as magic-unresolved. Now there are some places where we should return the name in its native form, and that is after gss_init_sec_context() is done by gss_inquire_context(), and gss_canonicalize_name(). We also need to deal with these magic-unresolved names in gss_acquire_cred() and gss_export_name().

So lets go over the four cases when we have a magic-unresolved.

gss_init_sec_context(), we try first to get Kerberos credentials using TGS-REQ using the sort name and hope that its an valid alias, if no, we call back to the old way with krb5_sname_to_principal(). Right, we update the name in the context to what we used.

gss_acquire_cred() same thing here, first try literal, then krb5_sname_to_principal().

gss_inquire_context(), this is simple gss_init_sec_context() will have solve the problem for us, just copy out the string.

gss_canonicalize_name() here we don't have a chance, so I guess, we want to have the canonicalized name, so I used the krb5_sname_to_principal() to canonicalize the name.

So where to store this magic-unresolved bit ? Well it happens to be so that the Kerberos gss-api mech uses Kerberos principals (krb5_principal) so there no extra bit where we can save the info. So, instead we hook the krb5_principal name type field and misuse that. Any time we will export or use the principal, we'll convert back to KRB5_NT_SRV_HST that it would have been if we used krb5_sname_to_principal().

Kerberos ticket extentions

Last Sunday I updated the draft Kerberos ticket extensions to version -02.

Ticket extentions are to enable PK-CROSS and other applications that want to send clear text data in the ticket between the KDC and the server.

The update included and extension to the Kerberos protocol, a much cleaner extention protocol wise, at the same time it requires update clients. The reason I did both was the comment from Ken Raeburn that though the new protocol was horrible (which it is) and Kerberos should stay pretty, so I made the protocol stay pretty.

There is still the issue with protection, may I just should just give up making it truly extensionally and just include a checksum using the same key as the Ticket.enc-data is encrypted with.

PKINIT works with Samba4 + windows XP

Today we got a patch from Sho Hosoda that add back the Windows XP SP2 support to Heimdal PK-INIT support. With this we can use smart cards to logins a Samba4 domain, this is way cool and why we started this work several years ago.

http://www.h5l.org/fisheye/changelog/heimdal/?cs=23861

Referrals

This is something I brough up at IETF72 in Dublin, Ireland.

Kerberos (in the non Microsoft world) have always used DNS map to Kerberos principals. Sam Hartman describes the issue more here: http://www.painless-security.com/blog/2008/08/krb-dns/

My idea doesn't come from how to secure Kerberos (I already know that using DNS is bad), it comes from how to make Kerberos useful for users in the transition. Having client configuration really sucks, its horrible and a really pain to upgrade, and when you think you solved it, someone installs a old krb5.conf that "have always worked" and was "needed for some reason I can't remember". The reason it worked was because they forced the client to not upgrade, and the reason is that they have a broken application that can't do the right thing. Do I sound bitter, well, kind of.

My idea is that the realm annouces in the krb5tgt that is support referrals and all entires are populated that the clients are supposed to be allowed to use. Ie, both host/shell@EXAMPLE.COM and host/shell.example.com@EXAMPLE.COM are in the Kerberos database. So when then user types in ssh shell, the library should just ignore that.

I've been experimenting with Heimdal to do this and have come some futher then when I talked at IETF with regard to practical problem.

First its hard to know what realm you are going to end up in, mostly because the interactions between name selection, dns canonlisation and referrals. The old way was simple:

1. host = getnamebyaddr(getaddrbyname(hosthost))


2. target = { service, host } @ getrealmforhost(host)


3. ticket = get-service-ticket(target)

Using what the user provided seems simple.

1. target = { service, hostname } @ get-realm(client-tgt)


2. ticket = get-service-ticket(target)


3. if ticket == null and compat: then ticket = old-method(hostname)


4. use ticket

where get-service-ticket is this:

1. tgt = get-tgt(client-principal)


2. service-ticket = tgs-req(tgt, target, [canon])


3. if (referrals(service-tkt)): then update(target, tgt = service-ticket), goto 2


4. return service-ticket

So lets say we are the user foo@FOO.COM and we want to login to
the machine shell.

shell (aka shell.foo.com) is really part of BAR.COM service and since FOO.COM's KDC knows that, its going to return a referral.

We are getting a referrals back, and the referral say that we should go to BAR.COM and what target principal to use.

In the AD world this is simple, all SPNs are part of the global catalog, so all KDC in the forest can figure out what the user really wanted. IN a pure Kerberos enviroment, its not that simple since this helicopter-view of the worlds doesn't exist. So in the pure environment we can't use short names when the short name is in another realm. We can only do hostname to realm mappings. Also note that the Global catalog on spans a forest, so in the multi-forest environment, Windows KDC also resolves to mapping full names into DNS names.

So a flag in the credential cache is probably a good idea to tell the client to turn off DNS-canon, but on the other hand, if the KDC turns on this flag, it also better support referrals and have a global view for its referral world if it want to support non-fqdn types of names.

Heimdal have had server referral for quite some time now, MIT Kerberos have not (they have it in the client though).

GSS_C_DELEG_POLICY_FLAG and cross realm

I've been working on the draft for GSS_C_DELEG_POLICY_FLAG lately. One thing I have added is th reason why we need this document. This was requested by reviewers.

Its for legacy deployments that can't update Kerberos today and can't/don't want to change behavior.

Getting the flag defined and the behavior clarified is only the first step of this process. The second is to make sure it works in the cross realm case too. The proposal I have is to make it an MUST that all intermediate cross realm tgt tickets also have ok-as-delegate flag set. It seems Microsoft does it that was and I've asked them if I've read their spec is correctly.