How to generate Signature in AWS from Java

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

Request:

Host: https://xxx.execute-api.ap-southeast-1.amazonaws.com/latest/api/name

Authorization: AWS4-HMAC-SHA256 Credential={AWSKEY}/20160314/ap-southeast-1/execute-api/aws4_request,SignedHeaders=host;range;x-amz-date,Signature={signature}

X-Amz-Date: 20160314T102915Z

Response:

{
"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. The Canonical String for this request should have been 'xxx' "
}

From Java code, I followed AWS reference of how to generate Signature.

    String secretKey = "{mysecretkey}";
    String dateStamp = "20160314";
    String regionName = "ap-southeast-1";
    String serviceName = "execute-api";

    byte[] signature = getSignatureKey(secretKey, dateStamp, regionName, serviceName);
    System.out.println("Signature : " + Hex.encodeHexString(signature));

    static byte[] HmacSHA256(String data, byte[] key) throws Exception  {
         String algorithm="HmacSHA256";
         Mac mac = Mac.getInstance(algorithm);
         mac.init(new SecretKeySpec(key, algorithm));
         return mac.doFinal(data.getBytes("UTF8"));
    }

    static byte[] getSignatureKey(String key, String dateStamp, String regionName, String serviceName) throws Exception  {
         byte[] kSecret = ("AWS4" + key).getBytes("UTF8");
         byte[] kDate    = HmacSHA256(dateStamp, kSecret);
         byte[] kRegion  = HmacSHA256(regionName, kDate);
         byte[] kService = HmacSHA256(serviceName, kRegion);
         byte[] kSigning = HmacSHA256("aws4_request", kService);
         return kSigning;
    }

May I know what I was wrong while generating Signature?

Reference how to generate Signature : http://docs.aws.amazon.com/general/latest/gr/signature-v4-examples.html#signature-v4-examples-java

signature amazon-web-services rest java
5 Answers

This is possible using 100% java libraries without additional dependencies, just use the query parameters generated here:

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SignatureException;
import java.util.Formatter;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;

...

private static final String ACCESS_KEY = "...";
private static final String SECRET_KEY = "...";
private static final int expiresTime = 1 * 24 * 60 * 60;
private static final String HMAC_SHA1_ALGORITHM = "HmacSHA1";

public void sign(String protocol, String bucketName, String contentPath) throws Exception {
    Calendar cal = Calendar.getInstance();
    cal.add(Calendar.HOUR_OF_DAY, 24);

    String host = bucketName + ".s3-us-west-2.amazonaws.com";
    long expireTime = cal.getTimeInMillis() / 1000;

    String signString = "GET\n" +
        "\n" +
        "\n" +
        expireTime + "\n" +
        "/" + bucketName + contentPath;

    SecretKeySpec signingKey = new SecretKeySpec(SECRET_KEY.getBytes(), HMAC_SHA1_ALGORITHM);
    Mac mac = Mac.getInstance(HMAC_SHA1_ALGORITHM);
    mac.init(signingKey);
    String signature = URLEncoder.encode(new String(Base64.getEncoder().encode(mac.doFinal(signString.getBytes()))));

    System.out.println(signature);
    String fullPayload = "?AWSAccessKeyId=" + ACCESS_KEY +
        "&Expires=" + expireTime + 
        "&Signature=" + signature;

    System.out.println(protocol + "://" + host + contentPath + fullPayload);
}

...
user_4994890

The signing process is lengthy and error-prone, here are some tips

user_101166770

You may investigate code samples that is shared by AWS web site. I used some of the util classes and a few java class I need. So you don't have to use all classes and other stuff. I left the link below.

AWS Java Samples in doc of Amazon

user_34636460
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