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From "Christopher Lamb" <christopher.l...@ch.ibm.com>
Subject Re: Using Kerby kerb-client as an alternative for GSS-API.... Sgt Request fails
Date Tue, 09 May 2017 05:34:08 GMT

Hi all

I can now retrieve the Tgt from the creds-cache, and request a Sgt. However
I am now bouncing between 2 errors. "ERR BAD OPTION" and "ERR GENERIC".

If I create the Tgt with the clientPrincipal, the request is rejected by
the KDC with "ERR BAD OPTION".

Examining the request with Wireshark shows a cname element in the req-body.
This is not present in successful requests via GSS-API.

        cname
            name-type: kRB5-NT-PRINCIPAL (1)
            cname-string: 1 item
                CNameString: lamb

The KDC log shows "TGT NOT PROXIABLE:" for the failed request.


On the other hand, if I fill the clientPrincipal on the Tgt with null the
request is rejected by the KDC with "ERR GENERIC".

The cname element is no longer present in the request body (which now looks
identical that made by GSS-API).

The KDC logs show "ASN.1 structure is missing a required field". I suspect
this refers to the encrypted "app-req/authenticator/cname",
which debugging shows is now null!


private TgtTicket retrieveCachedTicket(File ccacheFile) throws KrbException
{

	Ticket ticket = null;
	PrincipalName clientPrincipal = null;
	EncAsRepPart encKdcRepPart = null;

	if (ccacheFile.exists() && ccacheFile.canRead()) {
		CredentialCache cCache = new CredentialCache();
		try {
			cCache.load(ccacheFile);

			List<Credential> credentials = cCache.getCredentials();

			for (Credential cred : credentials) {
				//we only want a tgt
				if (cred.getServerName().toString().startsWith
("krbtgt")) {
					ticket = cred.getTicket();
					clientPrincipal = cred.getClientName();

					encKdcRepPart = new EncAsRepPart();
					encKdcRepPart.setAuthTime(cred.getAuthTime
());
					encKdcRepPart.setCaddr
(cred.getClientAddresses());
					encKdcRepPart.setEndTime(cred.getEndTime());
					encKdcRepPart.setFlags(cred.getTicketFlags
());
					encKdcRepPart.setKey(cred.getKey());
					encKdcRepPart.setRenewTill(cred.getRenewTill
());
					encKdcRepPart.setSname(cred.getServerName());
					encKdcRepPart.setSrealm(cred.getServerName
().getRealm());
					encKdcRepPart.setStartTime(cred.getStartTime
());
				}
			}

		} catch (IOException e) {
			throw new KrbException("Failed to load credentials", e);
		}
	} else {
		throw new IllegalArgumentException("Invalid ccache file, "
				+ "does not exist, or is not readable: " +
ccacheFile.getAbsolutePath());
	}
	return new TgtTicket(ticket, encKdcRepPart, clientPrincipal);
}


private void getKerbyServiceTicket() {
	try {
		File confFileDir = new File
("/home/lamb/OTMS/kerberosTesting/");
		KrbClient krbClient = new KrbClient(confFileDir);

		krbClient.setKdcHost("kdc.acme.com");
    krbClient.setAllowUdp(true);
		krbClient.setAllowTcp(true);
		krbClient.setKdcUdpPort(88);
		krbClient.setKdcTcpPort(88);
		krbClient.init();

		File credsCache = new File("/tmp/krb5cc_9337");

		TgtTicket tgtTicket = retrieveCachedTicket(credsCache);

		KOptions requestOptions = new KOptions();
		requestOptions.add(KrbKdcOption.PROXIABLE, true);
		requestOptions.add(KrbKdcOption.FORWARDABLE);
		requestOptions.add(KrbKdcOption.CANONICALIZE, true);
		requestOptions.add(KrbKdcOption.RENEWABLE_OK, false);
		requestOptions.add(KrbOption.USE_TGT, tgtTicket);

		requestOptions.add(KrbOption.SERVER_PRINCIPAL,
"HTTP/app-srv.acme.com@ACME.COM");

		SgtTicket sgtTicket = krbClient.requestSgt(requestOptions);


	} catch (KrbException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}

}

Rejected Request "BAD OPTION":

tgs-req
    pvno: 5
    msg-type: krb-tgs-req (12)
    padata: 1 item
        PA-DATA PA-TGS-REQ
            padata-type: kRB5-PADATA-TGS-REQ (1)
                padata-value:
6e82023b30820237a003020105a10302010ea20703050000...
                    ap-req
                        pvno: 5
                        msg-type: krb-ap-req (14)
                        Padding: 0
                        ap-options: 00000000
                            0... .... = reserved: False
                            .0.. .... = use-session-key: False
                            ..0. .... = mutual-required: False
                        ticket
                            tkt-vno: 5
                            realm: ACME.COM
                            sname
                                name-type: kRB5-NT-PRINCIPAL (1)
                                sname-string: 2 items
                                    SNameString: krbtgt
                                    SNameString: ACME.COM
                            enc-part
                                etype: eTYPE-AES256-CTS-HMAC-SHA1-96 (18)
                                kvno: 1
                                cipher:
c2da50b960fdfdc44e098ee243f0aa698cfad82b8867fb98...
                        authenticator
                            etype: eTYPE-AES256-CTS-HMAC-SHA1-96 (18)
                            cipher:
5e944cb16b72c6cb12b830b91e83ca84b3b7eadfb364e7da...
    req-body
        Padding: 0
        kdc-options: 50010000 (forwardable, proxiable, canonicalize)
            0... .... = reserved: False
            .1.. .... = forwardable: True
            ..0. .... = forwarded: False
            ...1 .... = proxiable: True
            .... 0... = proxy: False
            .... .0.. = allow-postdate: False
            .... ..0. = postdated: False
            .... ...0 = unused7: False
            0... .... = renewable: False
            .0.. .... = unused9: False
            ..0. .... = unused10: False
            ...0 .... = opt-hardware-auth: False
            .... ..0. = request-anonymous: False
            .... ...1 = canonicalize: True
            0... .... = constrained-delegation: False
            ..0. .... = disable-transited-check: False
            ...0 .... = renewable-ok: False
            .... 0... = enc-tkt-in-skey: False
            .... ..0. = renew: False
            .... ...0 = validate: False
        cname
            name-type: kRB5-NT-PRINCIPAL (1)
            cname-string: 1 item
                CNameString: lamb
        realm: ACME.COM
        sname
            name-type: kRB5-NT-PRINCIPAL (1)
            sname-string: 2 items
                SNameString: HTTP
                SNameString: app-srv.acme.com
        from: 2017-05-09 04:42:12 (UTC)
        till: 2017-05-09 12:42:12 (UTC)
        nonce: 589063260
        etype: 3 items
            ENCTYPE: eTYPE-ARCFOUR-HMAC-MD5 (23)
            ENCTYPE: eTYPE-AES256-CTS-HMAC-SHA1-96 (18)
            ENCTYPE: eTYPE-AES128-CTS-HMAC-SHA1-96 (17)


Thanks

Chris



From:	Christopher Lamb/Switzerland/IBM@IBMCH
To:	kerby@directory.apache.org
Date:	08/05/2017 18:43
Subject:	Re: Using Kerby kerb-client as an alternative for GSS-API for
            Kerberos Single Sign On.



Hi Kai

With the following code I can successfully retrieve a TGT from my existing
credential cache and use it to request a service ticket!.

Unfortunately the Service Ticket Request is currently failing with "KDC
cannot accommodate requested option".


private TgtTicket retrieveCachedTicket(File ccacheFile) throws KrbException
{

Ticket ticket = null;
PrincipalName clientPrincipal = null;
EncAsRepPart encKdcRepPart = null;

if (ccacheFile.exists() && ccacheFile.canRead()) {
CredentialCache cCache = new CredentialCache();
try {
cCache.load(ccacheFile);

List<Credential> credentials = cCache.getCredentials();

for (Credential cred : credentials) {
//we only want a tgt
if (cred.getServerName().toString().startsWith("krbtgt")) {
ticket = cred.getTicket();
clientPrincipal = cred.getClientName();

encKdcRepPart = new EncAsRepPart();
encKdcRepPart.setAuthTime(cred.getAuthTime());
encKdcRepPart.setCaddr(cred.getClientAddresses());
encKdcRepPart.setEndTime(cred.getEndTime());
encKdcRepPart.setFlags(cred.getTicketFlags());
encKdcRepPart.setKey(cred.getKey());
//encKdcRepPart.setKeyExpiration(); //no method to get from cred
//encKdcRepPart.setLastReq(); //no method to get from cred
//encKdcRepPart.setNonce(); //no method to get from cred
encKdcRepPart.setRenewTill(cred.getRenewTill());
encKdcRepPart.setSname(cred.getServerName());
encKdcRepPart.setSrealm(cred.getServerName().getRealm());
encKdcRepPart.setStartTime(cred.getStartTime());
}
}

} catch (IOException e) {
throw new KrbException("Failed to load credentials", e);
}
} else {
throw new IllegalArgumentException("Invalid ccache file, "
+ "does not exist, or is not readable: " + ccacheFile.getAbsolutePath());
}
return new TgtTicket(ticket, encKdcRepPart, clientPrincipal);
}


private void getKerbyServiceTicket() {
try {
File confFileDir = new File("/home/lamb/OTMS/kerberosTesting/");
KrbClient krbClient = new KrbClient(confFileDir);

krbClient.setKdcHost("kdc.acme.com");
krbClient.setAllowUdp(true);
krbClient.setAllowTcp(true);
krbClient.setKdcUdpPort(88);
krbClient.setKdcTcpPort(88);
krbClient.init();

File credsCache = new File("/tmp/krb5cc_9337");

TgtTicket tgtTicket = retrieveCachedTicket(credsCache);

KOptions requestOptions = new KOptions();
requestOptions.add(KrbKdcOption.PROXIABLE);
requestOptions.add(KrbKdcOption.FORWARDABLE);
requestOptions.add(KrbKdcOption.RENEWABLE_OK);
requestOptions.add(KrbOption.USE_TGT, tgtTicket);
requestOptions.add(KrbOption.SERVER_PRINCIPAL,
"HTTP/app-srv.acme.com@ACME.COM");

SgtTicket sgtTicket = krbClient.requestSgt(requestOptions);


} catch (KrbException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

Below are extracts from the KDC logs for a failed request from my
kerb-client code above, and 2 successful requests from GSS-API


Rejected request from Java kerby kerb-client
94117:May 08 17:16:26 kdc.acme.com krb5kdc[2177](info): TGS_REQ (3 etypes
{23 18 17}) 9.164.27.87: TGT NOT PROXIABLE: authtime 0, lamb@ACME.COM for
HTTP/app-srv.acme.com@ACME.COM, KDC can't fulfill requested option

Successful request from Java GSS-API
77320:May 07 08:51:56 kdc.acme.com krb5kdc[2177](info): TGS_REQ (4 etypes
{18 17 16 23}) 9.83.236.240: ISSUE: authtime 1494139147, etypes {rep=18
tkt=18 ses=18}, lamb@ACME.COM for HTTP/app-srv.acme.com@ACME.COM

Successful request from Python GSS-API
94221:May 08 17:24:18 kdc.acme.com krb5kdc[2177](info): TGS_REQ (8 etypes
{18 17 20 19 16 23 25 26}) 9.164.27.87: ISSUE: authtime 1494256163, etypes
{rep=18 tkt=18 ses=18}, lamb@ACME.COM for HTTP/app-srv.acme.com@ACME.COM


Cheers

Chris




"Zheng, Kai" ---08/05/2017 14:32:29---Got your point. Please read
credential cache utility codes and see if any API doing so. Sent from iP

From: "Zheng, Kai" <kai.zheng@intel.com>
To: "kerby@directory.apache.org" <kerby@directory.apache.org>
Date: 08/05/2017 14:32
Subject: Re: Using Kerby kerb-client as an alternative for GSS-API for
Kerberos Single Sign On.



Got your point. Please read credential cache utility codes and see if any
API doing so.

Sent from iPhone

在 2017年5月8日,下午8:13,Christopher Lamb <christopher.lamb@ch.ibm.com<
mailto:christopher.lamb@ch.ibm.com>> 写道:


Hi Kai

Browsing further through the kerby code, I think I need the opposite of
KrbClientBase.storeTicket(): for instance a " Public TgtTicket
retrieveCachedTicket(File ccacheFile)"

Let me see if I can knock something together based on storeTicket()....

Cheers

Chris

[Inactive hide details for "Zheng, Kai" ---08/05/2017 13:09:19---If I
remember correctly, it first generates a cache with a TGT,]"Zheng, Kai"
---08/05/2017 13:09:19---If I remember correctly, it first generates a
cache with a TGT, then do the login test with the tick

From: "Zheng, Kai" <kai.zheng@intel.com<mailto:kai.zheng@intel.com>>
To: "kerby@directory.apache.org<mailto:kerby@directory.apache.org>"
<kerby@directory.apache.org<mailto:kerby@directory.apache.org>>
Date: 08/05/2017 13:09
Subject: RE: Using Kerby kerb-client as an alternative for GSS-API for
Kerberos Single Sign On.

________________________________



If I remember correctly, it first generates a cache with a TGT, then do the
login test with the ticket cache. In your case, you would need to know
where is the cache file and point it to Kerby client, as the test did.

Regards,
Kai

From: Christopher Lamb [mailto:christopher.lamb@ch.ibm.com]
Sent: Monday, May 08, 2017 7:05 PM
To: kerby@directory.apache.org<mailto:kerby@directory.apache.org>
Subject: RE: Using Kerby kerb-client as an alternative for GSS-API for
Kerberos Single Sign On.


Hi Kai

Thanks, example code is always best.

TicketCacheLoginTest looks like part of the answer, especially the
storeTicket() function. However (unless I have completely misread the
test-case), the TGT is not retrieved from the cache, it is only stored
there.

In my Single-Sign-On case, the user already has a TGT, which was obtained
on log in to the workstation (or by kinit), prior to starting my java
client. I am assuming it should be possible for kerby to use the existing
TGT.

Cheers

Chris

[Inactive hide details for "Zheng, Kai" ---08/05/2017 12:45:22---Hi Chris,
Both dev list should be OK as Kerby folks are also in]"Zheng, Kai"
---08/05/2017 12:45:22---Hi Chris, Both dev list should be OK as Kerby
folks are also in the parent one.

From: "Zheng, Kai" <kai.zheng@intel.com<mailto:kai.zheng@intel.com><
mailto:kai.zheng@intel.com>>
To: "kerby@directory.apache.org<mailto:kerby@directory.apache.org><
mailto:kerby@directory.apache.org>" <kerby@directory.apache.org<
mailto:kerby@directory.apache.org><mailto:kerby@directory.apache.org>>
Date: 08/05/2017 12:45
Subject: RE: Using Kerby kerb-client as an alternative for GSS-API for
Kerberos Single Sign On.

________________________________



Hi Chris,

Both dev list should be OK as Kerby folks are also in the parent one.

I haven't read your details fully (will do it later), but would make sure
if you have already checked out the test of TicketCacheLoginTest in the
kerby code base. In one word, Kerby client surely can consume and use a
credential cache generated by other tools like MIT kinit. If you see any
issue, please report it.

Regards,
Kai

-----Original Message-----
From: Christopher Lamb [mailto:christopher.lamb@ch.ibm.com]
Sent: Monday, May 08, 2017 5:09 PM
To: kerby@directory.apache.org<mailto:kerby@directory.apache.org><
mailto:kerby@directory.apache.org>
Subject: Using Kerby kerb-client as an alternative for GSS-API for Kerberos
Single Sign On.


Hi all

I hope this is the appropriate mailing list for this type of question. Or
would it be better on the Directory Developers’ list?

I am considering using Kerby kerb-client as an alternative to Java GSS-API
for a Java client application in a Kerberos single sign on environment.

In my proof of concept setup I am using FreeIPA clients and servers.  When
the user logs on to his workstation he is authenticated by the FreeIPA KDC,
and  gets a TGT which is cached in the default credentials cache. When he
wishes to access services from the application server (which is a Service
Principal), the TGT in the credentials cache is used to get a Service
Ticket, which should also be cached in the credentials cache for future
use.

With a throwaway Python GSS-API client this worked perfectly. "klist" shows
both the TGT and the SGT in the credentials cache. But trying to do the
same thing with Java GSS-API I ran into problems. While the Client is able
to retrieve a Service Ticket, and thus login to the Service Principal, the
SGT is not cached. Thus every request to the Service Principal requires KDC
interaction. Not good.

In my search for alternatives, I came across Kerby kerb-client, and am
experimenting with it, but so far without success despite much debugging
and scanning of Kerby code.

Here is the question: Can the Kerby kerb-client be configured to access an
existing Kerberos credential cache (as opposed to a KeyTab), and to use the
TGT ticket within, and to cache new service tickets? In this case the
existing credentials cache is from

So far I have found no config to do so. Searching through the Kerby code I
find references to things like  ‘credCache’, ‘KRB5_CACHE’, ‘ARMOR_CACHE’.
However in AbstractInternalKrbClient.requestTGT() I can’t find any USE_xxx
options that seem appropriate for using a credentials cache.

Have I missed something obvious? If so, which options should I be
configuring?

Thanks

Chris










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