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I have two different proprietary software, one is radius module for billing, second is phone station pbx.

When client doing a call, pbx sends radius auth packet to the billing. And billing answering.

I have problem with radius response. PBX say me:

Auth bad CRC in response

I dont know is it true or not.

I record tcpdump of request-response and want to calculate right crc.

But what mean CRC? Is it that

Authenticator: fd4f8e9f12f7b72c29b1cae61713bddf

or something else in packet?

Please point me to right algorithm for this task.

UPD: I found ResponseAuth = MD5(Code+ID+Length+RequestAuth+Attributes+Secret) where + denotes concatenation.

on this page http://www.hjp.at/doc/rfc/rfc2865.txt.

And here i upload my dump https://gist.github.com/5203725

Korjavin Ivan
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  • You could look at the code for the Perl module `Net::RADIUS::Packet`, especially into the `password()` and `set_password()` subs. Also, `auth_req_verify` would probably the correct function for you to look at: http://cpansearch.perl.org/src/LUISMUNOZ/Net-Radius-2.103/Radius/Packet.pm – Alexander Janssen Mar 20 '13 at 10:38
  • I found Digest::MD5::md5(substr($packet, 0, 4) . $prauth . substr($packet, 20) . $secret) , thank you. Will try just now – Korjavin Ivan Mar 20 '13 at 10:46
  • You could also see if `wireshark` will check and report the validity of the checksum in the response packet. – Flup Mar 20 '13 at 11:17
  • @Flup My mireshark dont show me validity. – Korjavin Ivan Mar 20 '13 at 11:55

1 Answers1

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Checksum errors in RADIUS responses usually point to the shared secret being different at the sender and receiver. If you get these errors for every packet received by the PBX, double-check that the shared secret is the same at both ends.

Flup
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