Subject: Re: (radius) Username/User-Password attributes

From: [email-masked] (Patrice Calhoun)
Date: Wed, 28 Oct 1998 09:38:47 -0800

>> You have 128 bits to play with. Even if all of these bits were in ascii I
>really
>> don't see the issue. 
>
>128 bits is pretty safe.  Also, some vendors do allow hexadecimal strings
>for shared secrets which further increases the entropy.
>
>
>>If a manufacturer's default password is inadequate, change
>> it (I am sure this is an option, as I recall from my experience building
>NASes
>> they have plenty of options).
>
>I do not quite understand this.  This is a typical RADIUS problem where
>the distinction between the shared secret and password is often lost.  
>The issue here is that the password used for Pre-Auth is a known value. 
>This cannot be changed as they are usually hard coded values.  Unless a
>vedor allows them to be configurable, which I dont think anybody does. 

3Com (or USR :) allowed the pre-auth secret to be changed. I think that any
NAS vendor that hard codes secrets and does not allow for configuration should
rethink their strategy. Security is an important issue within ISP networks and
leaving such a security hole is unforgivable (IMHO).

>Given enough number of plaintext/ciphertext combinations through sniffing
>packets, it would be pretty easy to derive the key (shared secret).  Plus
>it is made easier which Access-Requests to look for, since we know the
>username would look like a telephone number.

Again, if the password is configurable, this is a non-issue. In addition,
how would the user sniff packets? By issuing bogus route updates to direct
traffic to him? If the user can do this on an ISP's network then RADIUS'
cryto strength is not even an issue as there are plenty of other ways to 
attack a network once this has been done.

And remember that a RADIUS server receiving packets from an unknown client
MUST NOT respond. 

>Although,  a 128 bit shared secret should make things pretty secure even
>under known plaintext attacks. 
>
>But who said anything about RADIUS being a very secure protocol??

I agree :(

PatC

-
To unsubscribe, email [email-masked]' with
'unsubscribe ietf-radius' in the body of the message.

---

From: William Bulley <[email-masked]>
Date: Wed, 28 Oct 1998 15:39:31 -0500 (EST)

> >But who said anything about RADIUS being a very secure protocol??

But it seems people have forgotten the random contents of the vector
in the header of each Access-Request packet.

Regards,

web...

-- 
William Bulley                     Senior Systems Research Programmer
Merit Network, Inc.                Email: [email-masked]
4251 Plymouth Road, Suite C        Phone: (734) 764-9993
Ann Arbor, Michigan  48105-2785    Fax:   (734) 647-3185

[ Reuters, London, February 29, 1998: Scientists have announced discovering ]
[ a meteorite which will strike the earth in March, 2028.  Millions of UNIX ]
[ coders expressed relief for being spared the UNIX epoch "crisis" of 2038. ]
-
To unsubscribe, email [email-masked]' with
'unsubscribe ietf-radius' in the body of the message.

---

From: Murtaza Chiba <[email-masked]>
Date: Thu, 29 Oct 1998 11:37:06 -0500

>In addition,
> traffic to him? 

That is only one of the possible methods.  Its basically an issue of whom
do you trust.  RADIUS is built on the model that everybody on an internal
network can be trusted.  Hence, everything is in clear text (except for
the passwords) and there is no attempt to secure it using TLS or any such
mechanism.
Although, I agree that a dial-in user may not be able to do much (unless
he can write up agents to capture
RADIUS packets using some bug in well known applications, e.g. Web servers
running CGI scripts or worse java programs without proper security), I am
not sure that you can trust EVERYONE on the internal network either.

>But it seems people have forgotten the random contents >of the vector

Dont forget that that is sent along with the packet, else how would the
server verify the password?

On the other hand RADIUS is a good simple protocol that allows future
protocols to easily adapt on its weaknesses.  

Murtaza
-- 
**************************************************************
Name: Murtaza S. Chiba		Company:Bay Networks
Tel No. : (978)916-4689		Fax: (978)916-4789
Interests: Bicycling, chess and the outdoors
Home Page: http://lynx.neu.edu/m/mchiba
-
To unsubscribe, email [email-masked]' with
'unsubscribe ietf-radius' in the body of the message.