Authentication of REST-Query Requests

Authentication requirements for the License Service requests vary for desktop products and web products:

REST-Query requests for the License Service that require authentication must include the following items:

Following is the series of tasks required to authenticate requests to AWS. It is assumed you have already created an AWS account and received an Access Key ID and Secret Access Key. For more information about these items, see Your AWS Account and Your AWS Identifiers.

You perform the first three tasks.

Process for Authentication: Tasks You Perform

	You construct a request to AWS.
	You calculate a keyed-hash message authentication code (HMAC-SHA1) signature using your Secret Access Key (for information about HMAC, go to http://www.faqs.org/rfcs/rfc2104.html)
	You include the signature and your Access Key ID in the request, and then send the request to AWS.

AWS performs the next three tasks.

Process for Authentication: Tasks AWS Performs

	AWS uses the Access Key ID to look up your Secret Access Key.
	AWS generates a signature from the request data and the Secret Access Key using the same algorithm you used to calculate the signature you sent in the request.
	If the signature generated by AWS matches the one you sent in the request, the request is considered authentic. If the comparison fails, the request is discarded, and AWS returns an error response.

The request must include an HMAC-SHA1 signature. The signature is used as the value for the Signature parameter in the request URL being constructed. The string you use to compute the HMAC signature is constructed using the method described in the following procedure.

	Important
	Do not URL encode the concatenated string before computing the signature. URL encode the computed signature and other query parameters as specified in RFC1738, section 2.2. In addition, make sure to encode the + character although it is not required by RFC1738. This is required because the + character is interpreted as a blank space by Sun Java classes that perform URL decoding.

The following Java code snippet constructs the string.

/*
* Assumes parameters are in a java.util.Map named paramMap
* where the key is the parameter name.
*/
Set<String> sortedKeys = new TreeSet<String>(String.CASE_INSENSITIVE_ORDER);
sortedKeys.addAll(paramMap.keySet());

// Don't include Signature in the string to sign.
sortedKeys.remove(“Signature”);

StringBuilder stringBuilder = new StringBuilder();
for(String key : sortedKeys) {
    stringBuilder.append(key);
    stringBuilder.append(paramMap.get(key));
    }

System.out.println("String to sign : " + stringBuilder.toString());

The time stamp (or expiration time) you use in the request must be a dateTime object (for more information, go to http://www.w3.org/TR/xmlschema-2/#dateTime). Although it is not required, we recommend you provide the time stamp in the Coordinated Universal Time (Greenwich Mean Time) time zone. For example: 2007-01-31T23:59:59.183Z.

If you specify a time stamp (instead of an expiration time), the request automatically expires 15 minutes after the time stamp (in other words, AWS does not process a request if the request time stamp is more than 15 minutes earlier than the current time on AWS servers). Make sure your server's time is set correctly.

	Important
	If you are using .NET you must not send overly specific time stamps, due to different interpretations of how extra time precision should be dropped. To avoid overly specific time stamps, manually construct dateTime objects with no more than millisecond precision.

HMAC-SHA1 request signatures must be base64 encoded. The following sample code shows how to perform base64 encoding.

package amazon.webservices.common;
/**
* 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);
}
}

The following Java code sample shows how to calculate an HMAC request signature.

package amazon.webservices.common;

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;
}
}