io.github.binaryfoo.decoders.SignedDynamicApplicationDataDecoder.kt Maven / Gradle / Ivy

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Some decoders for the data used in EMV credit card transactions.

There is a newer version: 0.1.8

package io.github.binaryfoo.decoders

import io.github.binaryfoo.DecodedData
import io.github.binaryfoo.EmvTags
import io.github.binaryfoo.decoders.annotator.SignedDataDecoder
import io.github.binaryfoo.findAllForValue
import io.github.binaryfoo.findForTag
import io.github.binaryfoo.tlv.ISOUtil
import kotlin.collections.listOf

/**
 * Dynamic data auth means CA (scheme) -> Issuer -> ICC -> data
 *
 * Covers both DDA (the first step up from SDA) and CDA (combined with Generate AC)
 *
 * EMV 4.3 Book2, Table 18: Dynamic Application Data to be Signed
 */
class SignedDynamicApplicationDataDecoder : SignedDataDecoder {
    override fun decodeSignedData(session: DecodeSession, decoded: List) {
        val iccPublicKeyCertificate = session.iccPublicKeyCertificate
        val signedData = session.signedDynamicAppData ?: decoded.findForTag(EmvTags.SIGNED_DYNAMIC_APPLICATION_DATA)?.fullDecodedData
        if (signedData != null && iccPublicKeyCertificate != null) {
            for (decodedSignedData in decoded.findAllForValue(signedData)) {
                val signedDynamicData = decodedSignedData.tlv!!
                recoverSignedData(signedDynamicData, decodedSignedData, iccPublicKeyCertificate, ::decodeSignedDynamicData)
            }
        }
    }

}

fun decodeSignedDynamicData(recovered: ByteArray, startIndexInBytes: Int): List {
    val dynamicDataLength = Integer.parseInt(ISOUtil.hexString(recovered, 3, 1), 16)
    val iccDynamicNumberLength = Integer.parseInt(ISOUtil.hexString(recovered, 4, 1), 16)
    val cryptogramInformationData = ISOUtil.hexString(recovered, 5 + iccDynamicNumberLength, 1)
    return listOf(
        DecodedData.byteRange("Header", recovered, 0, 1, startIndexInBytes),
        DecodedData.byteRange("Format", recovered, 1, 1, startIndexInBytes),
        DecodedData.byteRange("Hash algorithm", recovered, 2, 1, startIndexInBytes),
        DecodedData.byteRange("Dynamic data length", dynamicDataLength.toString(), 3, 1, startIndexInBytes),
        DecodedData.byteRange("ICC dynamic number length", iccDynamicNumberLength.toString(), 4, 1, startIndexInBytes),
        DecodedData.byteRange("ICC dynamic number", recovered, 5, iccDynamicNumberLength, startIndexInBytes),
        *if (cryptogramInformationData != "BB") {
            arrayOf(
                DecodedData.byteRange("Cryptogram information data", cryptogramInformationData, 5 + iccDynamicNumberLength, 1, startIndexInBytes),
                DecodedData.byteRange("Cryptogram", recovered, 5 + iccDynamicNumberLength + 1, 8, startIndexInBytes),
                DecodedData.byteRange("Transaction data hash code", recovered, 5 + iccDynamicNumberLength + 1 + 8, 20, startIndexInBytes)
            )
        } else {
            arrayOf()
        },
        DecodedData.byteRange("Hash", recovered, recovered.size - 21, 20, startIndexInBytes),
        DecodedData.byteRange("Trailer", recovered, recovered.size - 1, 1, startIndexInBytes)
    )
}