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3.3.5.2 Received Challenge-Response Packet

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If the currentState variable is set to EAP_CHAP_CHALLENGE_SENT, then:

  • Obtain the Username and PeerChallenge from the embedded MSCHAPv2 Challenge-Response packet.

  • Obtain the user (specified by Username) Password using an implementation-specific mechanism.

  • Validate the embedded MSCHAPv2 Challenge-Response packet, as specified in [RFC2759] section 4.

  • If the validation is successful, then:

    • Prepare a Success-Request packet which embeds the resulting MSCHAPv2 Success packet, and send it to the peer.

    • Set currentState to EAP_CHAP_SUCCESS_REQUEST_SENT.

  • If the validation fails due to an expired password and AllowPasswordChange is true, then:

    • Prepare a Failure-Request packet that embeds the MSCHAPv2 Failure packet with the R bit set to zero and the corresponding validation error, and send it to the peer.

    • Obtain the AuthenticatorChallenge from the Failure-Request packet.

    • Set currentState to EAP_CHAP_CHANGE_PASSWORD_SENT.

  • If the validation fails due to an expired password and AllowPasswordChange is false, then:

    • Prepare an EAP Failure packet and send it to the peer.

    • Set currentState to EAP_CHAP_FAILED.

  • If the validation fails due to authentication failure ([RFC2759] section 6) and the RetryCount datum is nonzero, then:

    • Prepare a Failure-Request packet which embeds the MSCHAPv2 Failure packet with R bit set to one and the corresponding validation error, and send it to the peer.

    • Decrement the RetryCount datum by one.

    • Obtain the AuthenticatorChallenge from the Failure-Request packet.

    • Leave currentState set at EAP_CHAP_CHALLENGE_SENT.

  • If the validation fails because on an authentication failure ([RFC2759] section 6) and the RetryCount datum is zero, then:<6>

    • Prepare a Failure-Request packet which embeds the MSCHAPv2 Failure packet with the R bit set to zero and the corresponding validation error, and send it to the peer.

    • Set currentState to EAP_CHAP_FAILURE_REQUEST_SENT.

If the currentState variable is not set to EAP_CHAP_CHALLENGE_SENT, the packet is ignored.