NTRadPing is a very bad client to test real authentication.
While it says it has an Access-Accept packet it isn't doing any proper
checking of the packet. All Access-Accept packets are signed by the
server using the shared secret. A good client will check that signature.
A packet with a bad signature is rejected by a proper client even though
the server sent an Access-Accept.
Your test and discussion are pointless because the client NTRadPing is
not telling you that the packet is invalid. It's just displaying the
packet's contents.
PAP is the only authentication method where you would get an
Access-Reject with a bad secret.
[EMAIL PROTECTED] wrote:
Hi Phil,
I checked the issue with MSCHAP v1 and v2 as well. Even there the
authentication passes for an incorrect secret key
Thanks
-----Original Message-----
From:
[EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]
dius.org] On Behalf Of Phil Mayers
Sent: Tuesday, March 18, 2008 7:24 PM
To: FreeRadius users mailing list
Subject: Re: incorrect shared secret entry authenticates successfully
forfreerradius
[EMAIL PROTECTED] wrote:
Hi,
I am using the following configuration:
O/S: rhel4_u5_i386
Freeradius 1.1.7
Client to test: NTRadPing 1.5
Steps undertaken:
--------------------
- Installed a fresh system with rhel4_u5_i386
- Build and compile freeradius 1.1.7 on it.
- Update the clients.conf file to add the client entries for the
machine
that uses NTRadPing 1.5 (IP of the client machine and the shared
secret)
- Start the radiusd daemon in debug mode (radiusd -X)
- Now generate a simple PAP authentication request using NTRadPing.
(Port is 1812, also provide the shared secret correctly). The
authentication passes successfully as it should. Now give a junk
secret
key in the NTRadPing utility. The access is rejected.
- However when the same cases are tried for CHAP we can see the
difference. In the first case the authentication is successful;
however
when we give a junk shared secret the authentication should ideally
have
been rejected. However the authentication passes successfully.
NOTE: I tried the same for MSCHAPv1 and MSCHAPv2 authentication using
VPN client. There I can see clearly that the access is not granted to
the VPN client. However when we look at the radius logs it can be seen
that the Authentication requests responds with a Successful message.
Any help or info in this regards would be highly appreciated.
Only certain radius AVPs are encrypted with the shared secret:
fgrep encrypt /usr/share/freeradius/dictionary*
User-Password is one, so PAP fails if the shared secret is wrong. The
CHAP attributes are not, so the request succeeds. The MS-CHAP-MPPE-Keys
or MS-MPPE-Send-Key/MS-MPPE-Recv-Key reply attributes are encrypted, so
MS-CHAP will fail.
Many recent radius clients support the Message-Authenticator attribute,
which is a signature over the entire packets AVPs encrypted with the
shared secret. This will cause incorrect shared secrets to reject an
entire packet. See section 3.2 of RFC3579.
If your NAS supply Message-Authenticator, you could refuse packets
without one:
DEFAULT Message-Authenticator !* ANY, Auth-Type := Reject
-
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