Kotlin and AWS SDK v2 port of aws-request-signing-apache-interceptor

AwsRequestSigningInterceptor.kt

/**
 * An [HttpRequestInterceptor] that signs requests using any AWS [Aws4Signer] and [AwsCredentialsProvider].
 *
 * NOTE: Ported to kotlin and v2 SDK from https://github.com/awslabs/aws-request-signing-apache-interceptor/
 */
class AwsRequestSigningInterceptor(
        private val region: Region,
        private val service: String,
        private val signer: Aws4Signer,
        private val awsCredentialsProvider: AwsCredentialsProvider
) : HttpRequestInterceptor {

    override fun process(request: HttpRequest, context: HttpContext) {
        val uriBuilder = URIBuilder(request.requestLine.uri)

        // Copy Apache HttpRequest to an SDK request
        val sdkRequest = createSignableRequest(context, request, uriBuilder)

        // Sign it
        val credentials = awsCredentialsProvider.resolveCredentials()
        val signerParams = Aws4SignerParams.builder()
                .signingRegion(region)
                .signingName(service)
                .awsCredentials(credentials)
                .doubleUrlEncode(true)
                .build()
        val response = signer.sign(sdkRequest, signerParams)

        // Now copy everything back
        request.setHeaders(mapToHeaderList(response.headers()).toTypedArray())
        if (request is HttpEntityEnclosingRequest) {
            if (request.entity != null) {
                val basicHttpEntity = BasicHttpEntity()
                basicHttpEntity.content = response.contentStreamProvider().get().newStream()
                request.entity = basicHttpEntity
            }
        }
    }

    private fun createSignableRequest(context: HttpContext, request: HttpRequest, uriBuilder: URIBuilder): SdkHttpFullRequest {
        val sdkHttpFullRequest = SdkHttpFullRequest.builder()

        (context.getAttribute(HTTP_TARGET_HOST) as? HttpHost)?.let {
            sdkHttpFullRequest.uri(URI.create(it.toURI()))
        }

        val httpMethod = HttpMethodName.fromValue(request.requestLine.method)
        sdkHttpFullRequest.method(SdkHttpMethod.fromValue(httpMethod.name))
        sdkHttpFullRequest.encodedPath(uriBuilder.build().rawPath)

        sdkHttpFullRequest.contentStreamProvider { ByteArrayInputStream(ByteArray(0)) }
        (request as? HttpEntityEnclosingRequest)?.let {
            it.entity?.content?.let { sdkHttpFullRequest.contentStreamProvider { it } }
        }

        uriBuilder.queryParams.forEach { sdkHttpFullRequest.appendRawQueryParameter(it.name, it.value) }
        request.allHeaders.filter { !skipHeader(it) }.forEach { sdkHttpFullRequest.appendHeader(it.name, it.value) }
        return sdkHttpFullRequest.build()
    }

    private fun mapToHeaderList(mapHeaders: MutableMap<String, MutableList<String>>): List<Header?> =
            mapHeaders.map { BasicHeader(it.key, it.value.joinToString(",")) }

    private fun skipHeader(header: Header): Boolean =
            (("content-length".equals(header.name, ignoreCase = true) && "0" == header.value) // Strip Content-Length: 0
                    || "host".equals(header.name, ignoreCase = true)) // Host comes from endpoint
}

Hello there,

Thank you so much because this helped us write our own adapter for v2. I just had one question since I am not familiar with Kotlin:

it.entity?.content?.let { sdkHttpFullRequest.contentStreamProvider { it } }

how is the conversion done here. Is it implicit?

Hi there,

This snippet is using Kotlin’s shorthand syntax for creating inline implementations of @FunctionalInterface interfaces using lambda syntax (see https://kotlinlang.org/docs/reference/java-interop.html#sam-conversions)

Here, the contentStreamProvider builder method takes in a ContentStreamProvider interface. This interface is marked as @FunctionalInterface. “{ it }” is defining a ContentStreamProvider whose newStream implementation (https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/http/ContentStreamProvider.html#newStream) returns “it”, which in this is input stream provided by the HttpEntity (HttpEntityEnclosingRequest.getEntity().getContent())

I see thank you very much for your valuable input

Thank you so much, it's really a pity that Amazon doesn't care about keeping their code/documentation up to date...
One remark: I think you can remove line 47 and instead use SdkHttpMethod.fromValue(request.requestLine.method) directly. This removes every to AWS-SDK-V1.

Thank you so much, it's really a pity that Amazon doesn't care about keeping their code/documentation up to date... One remark: I think you can remove line 47 and instead use SdkHttpMethod.fromValue(request.requestLine.method) directly. This removes every to AWS-SDK-V1.

Also found that issue, it can be removed