com.lithic.api.services.async.WebhookServiceAsyncImpl.kt Maven / Gradle / Ivy

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The Lithic Developer API is designed to provide a predictable programmatic interface for accessing your Lithic account through an API and transaction webhooks. Note that your API key is a secret and should be treated as such. Don't share it with anyone, including us. We will never ask you for it.

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// File generated from our OpenAPI spec by Stainless.

package com.lithic.api.services.async

import com.fasterxml.jackson.core.JsonProcessingException
import com.google.common.collect.ListMultimap
import com.lithic.api.core.ClientOptions
import com.lithic.api.core.JsonValue
import com.lithic.api.core.getRequiredHeader
import com.lithic.api.core.http.HttpResponse.Handler
import com.lithic.api.errors.LithicError
import com.lithic.api.errors.LithicException
import com.lithic.api.services.errorHandler
import java.security.MessageDigest
import java.time.Duration
import java.time.Instant
import java.util.Base64
import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec

class WebhookServiceAsyncImpl
constructor(
    private val clientOptions: ClientOptions,
) : WebhookServiceAsync {

    private val errorHandler: Handler = errorHandler(clientOptions.jsonMapper)

    override suspend fun unwrap(
        payload: String,
        headers: ListMultimap,
        secret: String?
    ): JsonValue {
        verifySignature(payload, headers, secret)
        return try {
            clientOptions.jsonMapper.readValue(payload, JsonValue::class.java)
        } catch (e: JsonProcessingException) {
            throw LithicException("Invalid event payload", e)
        }
    }

    override suspend fun verifySignature(
        payload: String,
        headers: ListMultimap,
        secret: String?
    ) {
        val webhookSecret =
            secret
                ?: clientOptions.webhookSecret
                ?: throw LithicException(
                    "The webhook secret must either be set using the env var, LITHIC_WEBHOOK_SECRET, on the client class, or passed to this method"
                )

        val whsecret =
            try {
                Base64.getDecoder().decode(webhookSecret.removePrefix("whsec_"))
            } catch (e: RuntimeException) {
                throw LithicException("Invalid webhook secret")
            }

        val msgId = headers.getRequiredHeader("webhook-id")
        val msgSignature = headers.getRequiredHeader("webhook-signature")
        val msgTimestamp = headers.getRequiredHeader("webhook-timestamp")

        val timestamp =
            try {
                Instant.ofEpochSecond(msgTimestamp.toLong())
            } catch (e: RuntimeException) {
                throw LithicException("Invalid signature headers", e)
            }
        val now = Instant.now(clientOptions.clock)

        if (timestamp.isBefore(now.minus(Duration.ofMinutes(5)))) {
            throw LithicException("Webhook timestamp too old")
        }
        if (timestamp.isAfter(now.plus(Duration.ofMinutes(5)))) {
            throw LithicException("Webhook timestamp too new")
        }

        val mac = Mac.getInstance("HmacSHA256")
        mac.init(SecretKeySpec(whsecret, "HmacSHA256"))
        val expectedSignature =
            mac.doFinal("$msgId.${timestamp.epochSecond}.$payload".toByteArray())

        msgSignature.splitToSequence(" ").forEach {
            val parts = it.split(",")
            if (parts.size != 2) {
                return@forEach
            }

            if (parts[0] != "v1") {
                return@forEach
            }

            if (MessageDigest.isEqual(Base64.getDecoder().decode(parts[1]), expectedSignature)) {
                return
            }
        }

        throw LithicException("None of the given webhook signatures match the expected signature")
    }
}