SNIP_CLASSIC_SECOC_SECTION_7_4_2_Authentication_during_triggered_transmission

7.4.2 Authentication during triggered transmission For transmission of an Authentic I-PDU using bus interfaces that allow triggered transmission (e.g. FrIf), the upper layer is configured in such a way that it calls the PduR module like it normally does for a direct transmission. Thus, the upper layer module immediately provides access to the Authentic I-PDU by providing the required buffer information through PduR_<Up>Transmit. The PduR forwards this transmission request to the SecOC module by calling SecOC_IfTransmit. Before the SecOC can provide data to the lower layer through the triggered transmission interface at least one previous call of SecOC_IfTransmit is required. If SecOC_TriggerTransmit is called and no data can be provided E_NOT_OK is returned. Note: Authentication for triggered transmission is only supported, if the upper layer initiates the transmission by explicitly calling PduR_<Up>Transmit in before. Triggered transmission in mode AlwaysTransmit shall not be used. In turn, the SecOC module allocates sufficient buffer capacities to store the Authentic I-PDU, the Secured I-PDU and all intermediate data of the authentication process. The SecOC module copies the Authentic I-PDU into its own buffer and returns (see SWS_SecOC_00057, SWS_SecOC_00058, SWS_SecOC_00059). The actual creation of the Secured I-PDU is processed during the subsequent call of the scheduled main function. This includes calculating the Authentication Information according to SWS_SecOC_00031 and adding the Authentication Information (i.e. the Authenticator and the possibly truncated Freshness Value) consecutively to the buffer location directly behind the Authentic I-PDU. Thereafter, SecOC module triggers the transmission of the Secured I-PDU to the destination lower layer module by calling PduR_SecOCTransmit at the PduR. [SWS_SecOC_00065]⌈ For transmission of Authentic I-PDUs using bus interfaces that allow triggered transmission (e.g. FrIf), the SecOC module shall calculate the Authenticator in the scheduled main function according to the overall approach specified in SWS_SecOC_00031. ⌋(SRS_SecOC_00010, SRS_SecOC_00012, SRS_SecOC_00013) [SWS_SecOC_00066]⌈ For transmission of Authentic I-PDUs using bus interfaces that allow triggered transmission (e.g. FrIf), the SecOC module shall create the Secured I-PDU in the scheduled main function. ⌋(SRS_SecOC_00010, SRS_SecOC_00012, SRS_SecOC_00013) In the following, the SecOC module serves as a data provider for the subsequent transmission request from the lower layer module. Thus, the SecOC module holds the complete Secured I-PDU and acts as the upper layer module. The upper layer module does not expect any further call back that request the copying of the Authentic I-PDU to the lower layer module. [SWS_SecOC_00067]⌈ For transmission of Authentic I-PDUs using bus interfaces that allow triggered transmission (e.g. FrIf), the SecOC module shall indicate the transmission request for the complete Secured I-PDU by triggering PduR_SecOCTransmit at the PduR. The PduR is responsible to further process the request and to notify the respective lower layer module. ⌋(SRS_SecOC_00010, SRS_SecOC_00012, SRS_SecOC_00013) The destination lower layer module calls PduR_<Lo>TriggerTransmit when it is ready to transmit the Secured I-PDU. PduR forwards this request to the SecOC module and the SecOC module copies the complete Secured I-PDU to the lower layer. Afterwards it returns. Note: The SecOc module must not forward the trigger transmit call to the upper layer but takes itself the role of the upper layer and copies the complete Secured I-PDU to the lower layer. [SWS_SecOC_00068]⌈ When SecOC_TriggerTransmit is called by the PduR module, the SecOC module shall copy the Secured I-PDU to the lower layer destination module. ⌋(SRS_SecOC_00010, SRS_SecOC_00012, SRS_SecOC_00013) [SWS_SecOC_00150]⌈ When SecOC_TriggerTransmit is called by the PduR module and the SecOC module is not able to provide a Secured I-PDU to the lower layer (no Secured I-PDU available), the SecOC module shall return the call with E_NOT_OK. ⌋(SRS_SecOC_00010, SRS_SecOC_00012, SRS_SecOC_00013) Finally, when the lower layer confirms the processing of the Secured I-PDU via PduR_<Lo>TxConfirmation (the result can be positive, if the PDU was successfully sent or negative if a transmission was not possible), the confirmation is forwarded to the SecOC module by calling SecOC_TxConfirmation. In turn, the SecOC module passes the result of the transmission process of the Authentic I-PDU at the PduR module so that the PduR module could forward the result via <Up>_TxConfirmation to the upper layer module which was the source of the original I-PDU (see SWS_SecOC_00063). During triggered transmission, the update rates of the upper layer modules and the lower layer modules might be different. Thus, the lower layer module might request a new transmission of a Secured I-PDU while the upper layer has not updated the Authentic I-PDU. In this case, the SecOC module supports the repeated transmission of the Authentic I-PDU by means of an updated Secure I-PDU. Thus, it has to preserve the Authentic I-PDU until the Secured I-PDU has been sent and its transmission has been confirmed by a means of SecOC_TxConfirmation. In this case, the SecOC module treats the existing Authentic I-PDU as new and re- authenticates it during the subsequent call to the SecOC_MainFunctionTx. [SWS_SecOC_00069]⌈ For transmission of Authentic I-PDUs using bus interfaces that allow triggered transmission (e.g. FrIf) and the transmission of the Secured I-PDU was confirmed by SecOC_TxConfirmation (successfully sent), the SecOC module shall free the buffer that contain Authentication Information and preserve the buffer that contain the Authentic I-PDU. If the parameter SecOCReAuthenticateAfterTriggerTransmit is set to true, the Authentic I-PDU shall be treated as if it has been set by the upper layer and thus shall undergo a new authentication procedure with the subsequent call of the SecOC_MainFunctionTx. Otherwise no reauthentication of the Authentic I-PDU is required. ⌋(SRS_SecOC_00010, SRS_SecOC_00012, SRS_SecOC_00013)