Converts an AWS secret access key to an Amazon SES SMTP password

gistfile1.txt

import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.bind.DatatypeConverter;

/**
 * @see The following pseudocode shows an algorithm that converts an AWS secret access key to an Amazon SES SMTP password.
 *      https://docs.aws.amazon.com/ses/latest/DeveloperGuide/smtp-credentials.html#smtp-credentials-console
 */
public class SesSmtpCredentialGenerator {

	public String getSmtpPasswordV4(String key){
		// The values of the following variables should always stay the same.
		final String message = "SendRawEmail";
		final String date = "11111111";
		final String service = "ses";
		final String terminal = "aws4_request";
		final String region = "eu-west-1";
		final byte VERSION4 = 0x04; // Version number. Do not modify.
		
		try {
			byte[] kDate = sign(date, ("AWS4" +key).getBytes());
		    byte[] kRegion = sign(region, kDate);
		    byte[] kService = sign(service, kRegion);
		    byte[] kTerminal = sign(terminal, kService);
		    byte[] kMessage = sign(message, kTerminal);
		    
		    // Snippet code-> signatureAndVersion = Concatenate(version, kMessage);
		    byte[] rawSignatureWithVersion = new byte[kMessage.length + 1];
		    byte[] versionArray = {VERSION4};
		    System.arraycopy(versionArray, 0, rawSignatureWithVersion, 0, 1);
		    System.arraycopy(kMessage, 0, rawSignatureWithVersion, 1, kMessage.length);
	
		    // Snippet code-> smtpPassword = Base64(signatureAndVersion);
		    String smtpPassword = DatatypeConverter.printBase64Binary(rawSignatureWithVersion);
		    System.out.println(smtpPassword);
		      
			return smtpPassword;
		} catch (Exception ex) {
			System.out.println("Error generating SMTP password: " + ex.getMessage());
		}
		return null;
	}

	private static byte[] sign(String msg, final byte[] key) throws NoSuchAlgorithmException, InvalidKeyException {
		SecretKeySpec secretKey = new SecretKeySpec(key, "HmacSHA256");
		// Get an HMAC-SHA256 Mac instance and initialize it with the AWS secret access key.
		Mac mac = Mac.getInstance("HmacSHA256");
		mac.init(secretKey);
		return mac.doFinal(msg.getBytes());
	}
}