Re: On shisa and its password disclosure.

[Russ Allbery]

Mats Erik Andersson  writes:

> The execution of "shisa -d --keys u...@ex.org" will print the
> password in clear text, which I find uncomforting. All the more
> so since it is not at all needed in maintaining the keytab file.
> I would have expected a dicotomy like used for shadow passwords,
> where only a string hash is stored, not the plain text string.

It's unusual to actually store the passwords, but Active Directory does so
as well because it allows you to do several other interesting things: add
new enctypes without forcing a password change, and handle authentication
methods other than Kerberos where the authentication server has to know
the password and not just a precomputed key.

There's no real difference in security within a single realm, although it
does mean that one can compromise other authentications for the same user
if they reuse a password.

> Executing "kadmin.local: getprinc user@SOL" will not reveal the clear
> text password, only basic information about the principal.  In my
> admittedly limited experience with MIT/Solaris, there has never appeared
> a means for the administrator to make readable any clear text
> passwords. Is there such a command?

MIT and Heimdal don't store the password, so indeed you can't retrieve
it.  (ktadd in both cases can extract the existing key, however, from
which you can authenticate as that user just as if you had the password.)

Active Directory stores the password, but you have to have a very high
level of access to the LDAP store in order to retrieve it.

-- 
Russ Allbery (r...@stanford.edu) 

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Re: On shisa and its password disclosure.

[Mats Erik Andersson]

söndag den 28 oktober 2012 klockan 10:46 skrev Russ Allbery detta:
> Mats Erik Andersson  writes:
> 
> > I am somewhat disturbed by that fact that the superuser
> > is able to execute
> 
> ># shisa -d --keys
> 
> > thereby gaining access to all passwords for all principals
> > of the running KDC.
> 
> The keys, or the passwords?  Not that it probably makes a lot of
> difference (although only being able to get the keys means that at least
> it's difficult to attack other realms where the user may reuse the
> password).

The execution of "shisa -d --keys u...@ex.org" will print the
password in clear text, which I find uncomforting. All the more
so since it is not at all needed in maintaining the keytab file.
I would have expected a dicotomy like used for shadow passwords,
where only a string hash is stored, not the plain text string.

That "shisa" exposes the salt and encryption key is acceptable
to me, since the latter is needed for the keytab, but printing
the passwords seems very backwards.

> > Contrast this to the situation with MIT Kerberos or Heimdal,
> > where a selected administrator is entrusted with the power to
> > inspect such secrecies, which the superuser is unable to access,
> > unless he was able to snoop the administrator's password.
> 
> The superuser on the KDC can similarly retrieve the keys for any principal
> in the Kerberos KDC with both MIT and Heimdal, using kadmin -l (Heimdal)
> or kadmin.local (MIT).

Executing "kadmin.local: getprinc user@SOL" will not reveal the
clear text password, only basic information about the principal.
In my admittedly limited experience with MIT/Solaris, there has never
appeared a means for the administrator to make readable any clear
text passwords. Is there such a command?

Regards,
  Mats E A

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Re: On shisa and its password disclosure.

[Russ Allbery]

Mats Erik Andersson  writes:

> I am somewhat disturbed by that fact that the superuser
> is able to execute

># shisa -d --keys

> thereby gaining access to all passwords for all principals
> of the running KDC.

The keys, or the passwords?  Not that it probably makes a lot of
difference (although only being able to get the keys means that at least
it's difficult to attack other realms where the user may reuse the
password).

> Contrast this to the situation with MIT Kerberos or Heimdal,
> where a selected administrator is entrusted with the power to
> inspect such secrecies, which the superuser is unable to access,
> unless he was able to snoop the administrator's password.

The superuser on the KDC can similarly retrieve the keys for any principal
in the Kerberos KDC with both MIT and Heimdal, using kadmin -l (Heimdal)
or kadmin.local (MIT).

It's very difficult in a traditional UNIX security model to protect
anything against the superuser, of course.  If all else fails, one can
always just read the disk database files directly.  Improved security
probably requires eliminating the traditional security model via something
like SELinux.

-- 
Russ Allbery (r...@stanford.edu) 

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On shisa and its password disclosure.

[Mats Erik Andersson]

Dear all,

I am somewhat disturbed by that fact that the superuser
is able to execute

   # shisa -d --keys

thereby gaining access to all passwords for all principals
of the running KDC.

Contrast this to the situation with MIT Kerberos or Heimdal,
where a selected administrator is entrusted with the power to
inspect such secrecies, which the superuser is unable to access,
unless he was able to snoop the administrator's password.

Am I lacking some insight, or is there a security issue here?

Best regards,
  Mats Erik Andersson

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