How to use Appsync Http Resolver with AWS services which expected post but without an request body?

How to use Appsync Http Resolver with AWS services which expected post but without an request body?

I try to make a request to this endpoint: https://docs.aws.amazon.com/codeartifact/latest/APIReference/API_ListPackages.html

Appsync Setup

Http datasource endpoint: https://codeartifact.eu-central-1.amazonaws.com/

I use following http resolver:

function request(ctx) {
  return {
    method: "POST",
    params: {
      query: {
        "domain": "<redacted>",
        "domain-owner": "<redacted>",
        "repository": "<redacted>"
      },
    },
    resourcePath: "/v1/packages",
  };
}

function response(ctx) {
  return [ctx.result.body];
}

export {
  request,
  response
};

Then I get following error message:

The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.

JS script

So I tried to create a js script to send such a request:

When I set applyChecksum to false, the request works.

When I set the applyChecksum to true, the request fails with the same error message above.

import {SignatureV4} from "@smithy/signature-v4";
import {Sha256} from "@aws-crypto/sha256-js";
import {defaultProvider} from "@aws-sdk/credential-provider-node";

const signatureV4 = new SignatureV4({
  service: "codeartifact",
  applyChecksum: false,                //if set to true, the reuqest fails
  region: "eu-central-1",
  credentials: defaultProvider(),
  sha256: Sha256
});


const url = new URL("https://codeartifact.eu-central-1.amazonaws.com/v1/packages")

const signedRequest = await signatureV4.sign({
  method: "POST",
  protocol: url.protocol,
  hostname: url.hostname,
  path: url.pathname,
  headers: {
    host: url.host
  },
  query: {
    'domain': "<redacted>",
    'domain-owner': "<redacted>",
    'repository': "<redacted>",
  }
});

edit:

cdk

this.graphqlApi = new GraphqlApi(this, 'AppSyncApi', {
...
})

const codeArtifactHttpDataSource = this.graphqlApi.addHttpDataSource('CodeArtifactHttpDataSource', `https://codeartifact.eu-central-1.amazonaws.com/`, {
  authorizationConfig: {
    signingRegion: 'eu-central-1',
    signingServiceName: 'codeartifact',
  },
});

codeArtifactHttpDataSource.grantPrincipal.addToPrincipalPolicy(new PolicyStatement({
  actions: ['codeartifact:DescribePackageVersion',
    'codeartifact:DescribeRepository',
    'codeartifact:GetPackageVersionReadme',
    'codeartifact:GetRepositoryEndpoint',
    'codeartifact:ListPackages',
    'codeartifact:ListPackageVersions',
    'codeartifact:ListPackageVersionAssets',
    'codeartifact:ListPackageVersionDependencies',
    'codeartifact:ReadFromRepository',
    'codeartifact:GetAuthorizationToken'],
  resources: ['*'],
}));

const appsyncFunction = new AppsyncFunction(this, 'AppsyncFunction', {
  api: this.graphqlApi ,
  dataSource: codeArtifactHttpDataSource,
  name: 'js_function',
  code: Code.fromAsset(path.join(__dirname, '<path-to-js>')),
  runtime: FunctionRuntime.JS_1_0_0,
});

new Resolver(this, 'Resolver', {
  api: this.graphqlApi,
  pipelineConfig: [appsyncFunction],
  typeName: 'Query',
  fieldName: '<fieldname>',
  runtime: FunctionRuntime.JS_1_0_0,
  code: Code.fromInline(`
    // The before step
    export function request(ctx) {
      return {}
    }
    // The after step
    export function response(ctx) {
      return ctx.prev.result
    }`)
});