com.github.kpavlov.jreactive8583.netty.pipeline.IsoMessageLoggingHandler.kt Maven / Gradle / Ivy

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ISO8583 protocol client and server Netty connectors.
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package com.github.kpavlov.jreactive8583.netty.pipeline

import com.solab.iso8583.IsoMessage
import com.solab.iso8583.IsoValue
import io.netty.channel.ChannelHandler.Sharable
import io.netty.channel.ChannelHandlerContext
import io.netty.handler.logging.LogLevel
import io.netty.handler.logging.LoggingHandler
import java.io.IOException
import java.io.InputStream
import java.lang.Integer.parseInt

/**
 * ChannelHandler responsible for logging messages.
 *
 * According to PCI DSS, sensitive cardholder data, like PAN and track data,
 * should not be exposed. When running in secure mode,
 * sensitive cardholder data will be printed masked.
 */
@Sharable
public open class IsoMessageLoggingHandler(
    level: LogLevel,
    private val printSensitiveData: Boolean,
    private val printFieldDescriptions: Boolean,
    private val maskedFields: IntArray = DEFAULT_MASKED_FIELDS,
) : LoggingHandler(level) {
    public companion object {
        private const val MASK_CHAR = '*'
        private val MASKED_VALUE = "***".toCharArray()

        @JvmField
        public val DEFAULT_MASKED_FIELDS: IntArray =
            intArrayOf(
                34, // PAN extended
                35, // track 2
                36, // track 3
                45, // track 1
            )

        private val FIELD_NAMES = arrayOfNulls(256)
        private const val FIELD_PROPERTIES = "iso8583fields.properties"

        private fun loadProperties() {
            try {
                propertiesStream.use { stream ->
                    val properties = java.util.Properties()
                    properties.load(stream)
                    properties.forEach { key: Any, value: Any? ->
                        val field = parseInt(key.toString())
                        FIELD_NAMES[field - 1] =
                            value as String
                    }
                }
            } catch (e: IOException) {
                throw IllegalStateException("Unable to load ISO8583 field descriptions", e)
            } catch (e: NumberFormatException) {
                throw IllegalStateException("Unable to load ISO8583 field descriptions", e)
            }
        }

        private val propertiesStream: InputStream
            get() {
                var stream =
                    Thread
                        .currentThread()
                        .contextClassLoader
                        .getResourceAsStream("/$FIELD_PROPERTIES")
                if (stream == null) {
                    stream =
                        IsoMessageLoggingHandler::class.java.getResourceAsStream(
                            "/com/github/kpavlov/jreactive8583/$FIELD_PROPERTIES",
                        )
                }
                return stream!!
            }

        init {
            loadProperties()
        }
    }

    public override fun format(
        ctx: ChannelHandlerContext,
        eventName: String,
        arg: Any,
    ): String =
        if (arg is IsoMessage) {
            super.format(ctx, eventName, formatIsoMessage(arg))
        } else {
            super.format(ctx, eventName, arg)
        }

    protected fun formatIsoMessage(m: IsoMessage): String {
        val sb = StringBuilder()
        if (printSensitiveData) {
            sb.append("Message: ").append(m.debugString()).append("\n")
        }
        sb.append("MTI: 0x").append("%04x".format(m.type))
        @Suppress("MagicNumber")
        for (i in 2..127) {
            if (m.hasField(i)) {
                val field = m.getField(i)
                sb.append("\n  ").append(i).append(": [")
                if (printFieldDescriptions) {
                    sb.append(FIELD_NAMES[i - 1]).append(':')
                }
                val formattedValue: CharArray
                formattedValue = getFormattedValue(field, i)
                sb
                    .append(field.type)
                    .append('(')
                    .append(field.length)
                    .append(")] = '")
                    .append(formattedValue)
                    .append('\'')
            }
        }
        return sb.toString()
    }

    protected fun getFormattedValue(
        field: IsoValue,
        i: Int,
    ): CharArray =
        if (printSensitiveData) {
            field.toString().toCharArray()
        } else {
            when {
                i == 2 -> maskPAN(field.toString())
                maskedFields.contains(i) -> MASKED_VALUE
                else -> field.toString().toCharArray()
            }
        }

    protected fun maskPAN(fullPan: String): CharArray {
        val maskedPan = fullPan.toCharArray()
        @Suppress("MagicNumber")
        for (i in 6 until maskedPan.size - 4) {
            maskedPan[i] = MASK_CHAR
        }
        return maskedPan
    }
}