[2397] in Kerberos-V5-bugs
pending/154: krb4 interface too lax in security
daemon@ATHENA.MIT.EDU (John Gardiner Myers)
Mon Nov 4 21:07:08 1996
Resent-From: gnats@rt-11.MIT.EDU (GNATS Management)
Resent-To: gnats-admin@rt-11.MIT.EDU
Resent-Reply-To: krb5-bugs@MIT.EDU, John Gardiner Myers <jgm@CMU.EDU>
Date: Mon, 4 Nov 1996 21:05:24 -0500 (EST)
From: John Gardiner Myers <jgm@CMU.EDU>
To: krb5-bugs@MIT.EDU
>Number: 154
>Category: pending
>Synopsis: krb4 interface too lax in security
>Confidential: yes
>Severity: serious
>Priority: medium
>Responsible: gnats-admin
>State: open
>Class: sw-bug
>Submitter-Id: unknown
>Arrival-Date: Mon Nov 04 21:07:01 EST 1996
>Last-Modified:
>Originator:
>Organization:
>Release:
>Environment:
>Description:
>How-To-Repeat:
>Fix:
>Audit-Trail:
>Unformatted:
I have my realm set up with all principals having the REQUIRES_PREAUTH
bit set. I need to be able to support v4 services, using a v4 tgt
obtained from krb524d. I do not want to support the v4 initial ticket
request protocol, since that can be used by attackers to perform
offline dictionary attacks on the keys in the database.
The "v4 key compatibilty" check is far too lax, causing known
plaintext encrypted with non-v4 salted keys to be exposed through the
v4 compatibility layer. This patch tightens up that check.
For bonus points, the code should be modified to return a correct
error code (KDC_NULL_KEY) to the caller. But I don't know how to get
that error propagated up from the kerb_get_principal interface.
(In my opinion, REQUIRES_PREAUTH should disable the v4 initital ticket
protocol, but my previous suggestion to that effect hasn't been
accepted by MIT.)
*** kerberos_v4.c 1996/11/02 20:54:26 1.1.1.1
--- kerberos_v4.c 1996/11/05 01:49:08
***************
*** 401,407 ****
krb5_dbe_find_enctype(kdc_context,
&entries,
ENCTYPE_DES_CBC_CRC,
! -1,
-1,
&pkey))
{
--- 401,407 ----
krb5_dbe_find_enctype(kdc_context,
&entries,
ENCTYPE_DES_CBC_CRC,
! KRB5_KDB_SALTTYPE_AFS3,
-1,
&pkey))
{
--
_.John Gardiner Myers Internet: jgm+@CMU.EDU
LoseNet: ...!seismo!ihnp4!wiscvm.wisc.edu!give!up
