[Samba] Slow Kerberos Authentication

L.P.H. van Belle
Fri, 10 Nov 2017 11:19:15 -0000

No, no idee, but really, upgrade to samba, best option, in my opinion.
If thats not possible, it happens..

A timeout option can be set in krb5.conf
for example :  kdc_timeout = 5000


You have these for krb5.conf to try out also.
the complete list.
des-hmac-sha1
	DES with HMAC/sha1 (weak)

aes256-cts-hmac-sha1-96 aes256-cts AES-256
	CTS mode with 96-bit SHA-1 HMAC

aes128-cts-hmac-sha1-96 aes128-cts AES-128
	CTS mode with 96-bit SHA-1 HMAC

arcfour-hmac rc4-hmac arcfour-hmac-md5
	RC4 with HMAC/MD5

arcfour-hmac-exp rc4-hmac-exp arcfour-hmac-md5-exp
	Exportable RC4 with HMAC/MD5 (weak)

camellia256-cts-cmac camellia256-cts
	Camellia-256 CTS mode with CMAC

camellia128-cts-cmac camellia128-cts
	Camellia-128 CTS mode with CMAC

des
	The DES family: des-cbc-crc, des-cbc-md5, and des-cbc-md4 (weak)

des3
	The triple DES family: des3-cbc-sha1

aes
	The AES family: aes256-cts-hmac-sha1-96 and aes128-cts-hmac-sha1-96

rc4
	The RC4 family: arcfour-hmac

camellia
	The Camellia family: camellia256-cts-cmac and camellia128-cts-cmac


try the lines i send before keep the allow weak encptions.
try these, and add them at the beginning.
arcfour-hmac



Greetz,

Louis






________________________________

	Van: Paul [mailto:bluescreen08 at gmail.com]
	Verzonden: vrijdag 10 november 2017 12:03
	Aan: L.P.H. van Belle
	CC: samba at lists.samba.org
	Onderwerp: Re: [Samba] Slow Kerberos Authentication


	I'll look into it and update if I find anything out :)
	Any idea why it would try enc type 17, then 18, then pause for 30 seconds?

	It feels like a timeout is being hit but I don't understand enough about
samba/Kerberos to figure out what it is.

	On 10 Nov 2017 09:37, "L.P.H. van Belle via samba" <samba at
lists.samba.org> wrote:


		Hai Paul,

		hmm, i think its time.. to upgrade your samba.

		I dont think the other krb5.conf options work, but you might give it a try.
		See man krb5.conf, where i took it from.
		add /change in krb5.conf

		 [kdc]
		tgt-use-strongest-session-key = BOOL
		svc-use-strongest-session-key = BOOL
		preauth-use-strongest-session-key= BOOL
		use-strongest-server-key = BOOL
		encode_as_rep_as_tgs_rep = BOOL

		BOOL = true or false.

		You might set the default windows encryption in krb5.conf as standard, but
imo, that are changes which might give other problems.
		And is not my best advice..

		So best advice is .. upgrade to samba 4, and packages are available.
		https://linux.oracle.com/errata/ELSA-2017-1271.html
<https://linux.oracle.com/errata/ELSA-2017-1271.html>


		Greetz,

		Louis





		Van: Paul [mailto:bluescreen08 at gmail.com]
		Verzonden: vrijdag 10 november 2017 9:57
		Aan: L.P.H. van Belle
		Onderwerp: Re: [Samba] Slow Kerberos Authentication



		Thanks, however that didn't work even after a reboot, still the same
error.

		On 9 Nov 2017 16:05, "L.P.H. van Belle via samba" <samba at
lists.samba.org> wrote:
		Hai,

		You may need to add the the following in krb5.conf

		[libdefaults]
		 allow_weak_crypto = true

		; for Windows 2003
		;    default_tgs_enctypes = rc4-hmac des-cbc-crc des-cbc-md5
		;    default_tkt_enctypes = rc4-hmac des-cbc-crc des-cbc-md5
		;    permitted_enctypes = rc4-hmac des-cbc-crc des-cbc-md5

		; for Windows 2008 with AES
		    default_tgs_enctypes = aes128-cts-hmac-sha1-96 aes256-cts-hmac-sha1-96
rc4-hmac des-cbc-crc des-cbc-md5
		    default_tkt_enctypes = aes128-cts-hmac-sha1-96 aes256-cts-hmac-sha1-96
rc4-hmac des-cbc-crc des-cbc-md5
		    permitted_enctypes = aes128-cts-hmac-sha1-96 aes256-cts-hmac-sha1-96
rc4-hmac des-cbc-crc des-cbc-md5

		Can you try that.

		Greetz,

		Louis



		> -----Oorspronkelijk bericht-----
		> Van: samba [mailto:samba-bounces at lists.samba.org
<mailto:samba-bounces at lists.samba.org> ] Namens Paul
		> via samba
		> Verzonden: donderdag 9 november 2017 16:45
		> Aan: samba at lists.samba.org
		> Onderwerp: [Samba] Slow Kerberos Authentication
		>
		> Hi All,
		>
		> I've a problem with samba 3.6.23 on Oracle Linux 6, Kerberos
		> authentication
		> is working but it takes around 30 seconds on first access. This is an
		> active directory domain with 2008r2 DC's.
		> I've tracked it down to what looks like the incorrect
		> encryption type being
		> used according to the debug output below, as you can see it
		> fails twice
		> with enc type of 17 and 18 but succeeds with 23... Which
		> according to the
		> RFC is rc4-hmac which is all windows DCs talk from what I can
		> find out.
		> How can I get it so the correct encryption is chosen first time?
		>
		> Log excerpt:
		>
		> [2017/11/09 10:18:04.174379,  3] smbd/sesssetup.c:662(reply_spn
		> ego_negotiate)
		>
		>   reply_spnego_negotiate: Got secblob of size 3264
		>
		> [2017/11/09 10:18:04.201392, 10] libads/kerberos_verify.c:435(a
		> ds_secrets_verify_ticket)
		>
		>   libads/kerberos_verify.c:435: enc type [18] failed to
		> decrypt with error
		> Bad encryption type
		>
		> [2017/11/09 10:18:04.214632, 10] libads/kerberos_verify.c:435(a
		> ds_secrets_verify_ticket)
		>
		>   libads/kerberos_verify.c:435: enc type [17] failed to
		> decrypt with error
		> Bad encryption type
		>
		> [2017/11/09 10:18:26.528850, 10] libads/kerberos_verify.c:423(a
		> ds_secrets_verify_ticket)
		>
		>   libads/kerberos_verify.c:423: enc type [23] decrypted message !
		>
		> [2017/11/09 10:18:26.529143, 10] libsmb/clikrb5.c:955(get_krb5_
		> smb_session_key)
		>
		>   Got KRB5 session key of length 16

		> --
		> To unsubscribe from this list go to the following URL and read the
		> instructions:  https://lists.samba.org/mailman/options/samba
<https://lists.samba.org/mailman/options/samba>
		>


		--
		To unsubscribe from this list go to the following URL and read the
		instructions:  https://lists.samba.org/mailman/options/samba
<https://lists.samba.org/mailman/options/samba>




		--
		To unsubscribe from this list go to the following URL and read the
		instructions:  https://lists.samba.org/mailman/options/samba
<https://lists.samba.org/mailman/options/samba>