How do I sign a REST request for Amazon API using Java and Eclipse?

Question

Here is my dilemma. I'm familiar with reading Java code, but no good at writing it. I have several examples from Amazon documentation, but I'm doing something wrong. I'm using Eclipse. I have the AWS Java SDK, Apache Commons Codec & Logging, and Base64. I have all the code in the proper classpaths inside my project.

I understand how to form the request (the order of elements, timestamp, etc.), but I don't know how to send this info to the java code to create the signed request. So I'll start with the code I am using from the documentation.

Code for Signature:

import java.security.SignatureException;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

    /**
    * This class defines common routines for generating
    * authentication signatures for AWS requests.
    */
    public class Signature {
        private static final String HMAC_SHA1_ALGORITHM = "HmacSHA1";
    /**
    * Computes RFC 2104-compliant HMAC signature.
    * * @param data
    * The data to be signed.
    * @param key
    * The signing key.
    * @return
    * The Base64-encoded RFC 2104-compliant HMAC signature.
    * @throws
    * java.security.SignatureException when signature generation fails
    */
        public static String calculateRFC2104HMAC(String data, String key)
                throws java.security.SignatureException
        {
            String result;
            try {

                // get an hmac_sha1 key from the raw key bytes
                SecretKeySpec signingKey = new SecretKeySpec(key.getBytes(), HMAC_SHA1_ALGORITHM);

                // get an hmac_sha1 Mac instance and initialize with the signing key
                Mac mac = Mac.getInstance(HMAC_SHA1_ALGORITHM);
                mac.init(signingKey);

                // compute the hmac on input data bytes
                byte[] rawHmac = mac.doFinal(data.getBytes());

                // base64-encode the hmac
                result = Encoding.EncodeBase64(rawHmac);

            } catch (Exception e) {
                throw new SignatureException("Failed to generate HMAC : " + e.getMessage());
            }
            return result;
        }
}

Code for Encoding:

/**
* This class defines common routines for encoding * data in AWS requests.
*/
public class Encoding {
    /**
    * Performs base64-encoding of input bytes.
    *
    * @param rawData * Array of bytes to be encoded.
    * @return * The base64 encoded string representation of rawData.
    */
    public static String EncodeBase64(byte[] rawData) {
        return Base64.encodeBytes(rawData);
    }
}

Code I came up with to sign request:

import java.security.SignatureException;

public class SignatureTest {
    /**
     * @param args
     * @throws SignatureException
     */
    public static void main( String[] args ) throws SignatureException {
        // data is the URL parameters and time stamp to be encoded
        String data = "<data-to-encode>";
        // key is the secret key
        String key = "<my-secret-key>";
        Signature.calculateRFC2104HMAC(data, key);
    }
}

At first, I was getting errors related to classpath, so I added those to my project. Now when I run the code, I get no errors and no response, I just return to a command prompt. I know this is probably a simple solution. I've spent a week trying to figure this out and have had no success finding any answers. Can someone point me in the right direction?

Note: I didn't include the Base64 code here because of the size, but I do have that in my project.

Answer 1

The line in my code:

Signature.calculateRFC2104HMAC(data, key);

is missing a print statement to display the results. Changing it to

System.out.println(Signature.calculateRFC2104HMAC(data, key));

gives me the result I was expecting.