How to generate Signature in AWS from Java

Question

When I invoke API endpoints from REST client, I got error by concerning with Signature.

Request:

Host: https://xxx.execute-ap

Answer 1

From the code example above it looks like you are not creating a canonical request and including it in the string that gets signed as per http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html

Instead of implementing this yourself have you looked at using a third-party library.

aws-v4-signer-java is a lightweight, zero-dependency library that makes it easy to generate AWS V4 signatures.

String contentSha256 = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
HttpRequest request = new HttpRequest("GET", new URI("https://examplebucket.s3.amazonaws.com?max-keys=2&prefix=J"));
String signature = Signer.builder()
        .awsCredentials(new AwsCredentials(ACCESS_KEY, SECRET_KEY))
        .header("Host", "examplebucket.s3.amazonaws.com")
        .header("x-amz-date", "20130524T000000Z")
        .header("x-amz-content-sha256", contentSha256)
        .buildS3(request, contentSha256)
        .getSignature();

Disclaimer: I'm the libraries author.