Proxying with radsec/TLS, Access-Reject leads to "spoofed proxy reply"

[Susan Barnes]

On 23.12.15 17:09, Alan DeKok wrote:
> On Dec 23, 2015, at 10:23 AM, Susan Barnes <barnes at rrz.uni-koeln.de> wrote:
>> I am playing with radsec. I have set up a proxy-connection between our staging server and an additional testserver to act as homeserver.
>>
>> Both servers are v3.0.10.
>>
>> What I have managed so far is:
>> The staging-server can contact the homeserver and establish a TLS-secured connection.
>>
>> The staging server sends a request to the homeserver and the homeserver will process it.
>>
>> The homeserver replies.
>>
>> If the homeserver rejects the Request, the staging-server will not accept the reply, but discards it with
>> "Ignoring spoofed proxy reply. Signature is invalid"
>>
>> If the homeserver sends an Access-Accept, the staging-server will accept the reply.
>
>    That's weird.  The code path is pretty much the same for both packets.
>
>> I have tried the proxy setup without radsec/TLS. In that case both Accept and Reject work.
>
>    OK.  I'll have to take a look at it.  Probably next week.
>
>> I have poked around with gdb on the staging server a bit.
>> Within rad_verify() at the point of calc_replydigest() we get to the point of
>> "Received %s packet from home server %s port %d with invalid Response Authenticator! (Shared secret is incorrect.)",
>> (did not appear anywhere in the Debug Output).
>>
>>
>> Does anyone have an idea what the problem could be?
>
>    Not really.. the code paths for accept / reject are pretty much identical.  Apparently not identical enough, though.
>
>    Either the home server is calculating the authenticator wrong, or the proxy is calculating it wrong.  Knowing which one would help.
>
>    I'd suggest using gdb to look at rad_verify() on the proxy, and rad_sign() on the home server.  Ensure that the "secret" variable is set to "radsec" on both ends.
>
>    Alan DeKok.
>

I have set breakpoints at the suggested places and as far as I can see 
the secret is "radsec" in all cases:

Homeserver:
Accept:
(gdb) print packet->code
$10 = 2
(gdb) print secret
$11 = 0x1b03e50 "radsec"

Reject:
(gdb) print  packet->code
$12 = 3
(gdb) print secret
$13 = 0x1b03e50 "radsec"


Staging(Client)-server:
Accept:
(gdb) print packet->code
$5 = 2
(gdb) print secret
$6 = 0x1955dc0 "radsec"

Reject:
(gdb) print packet->code
$2 = 3
(gdb) print secret
$3 = 0x1955dc0 "radsec"


Regards
Susan

-- 
S.Barnes
Cologne University IT/Networking Dept.