Walmart Header Signature snippet. Allows to generate the WM_SEC.AUTH_SIGNATURE header to authenticate in Walmart API services.

WalmartHeaderSignature.java

import org.apache.commons.codec.binary.Base64;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.spec.PKCS8EncodedKeySpec;

public class WalmartHeaderSignature {
  private static String consumerId = "CONSUMER_ID"; // Trimmed for security reason
  private static String baseUrl = "URL";

  /*You need to convert your .pem private key  to PK8 format using this command: openssl pkcs8 -topk8 -nocrypt -in key.pem -outform PEM
  * you need to paste the text between -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY-----*/
  private static String privateEncodedStr = "XXXX";

  public static void main(String[] args) {
    String httpMethod = "POST";
    String privateKeyVersion = "1";
    String timestamp = String.valueOf(System.currentTimeMillis());
    String stringToSign = consumerId + "\n" + timestamp + "\n" + privateKeyVersion + "\n";

    String signedString = WalmartHeaderSignature.signData(stringToSign, privateEncodedStr);
    System.out.println("timestamp: "+timestamp+ " Signed String: " + signedString);
  }
  public static String signData(String stringToBeSigned, String encodedPrivateKey) {
    String signatureString = null;
    try {
      byte[] encodedKeyBytes = Base64.decodeBase64(encodedPrivateKey);
      PKCS8EncodedKeySpec privSpec = new PKCS8EncodedKeySpec(encodedKeyBytes);
      KeyFactory kf = KeyFactory.getInstance("RSA");
      PrivateKey myPrivateKey = kf.generatePrivate(privSpec);
      Signature signature = Signature.getInstance("SHA256withRSA");
      signature.initSign(myPrivateKey);
      byte[] data = stringToBeSigned.getBytes("UTF-8");
      signature.update(data);
      byte[] signedBytes = signature.sign();
      signatureString = Base64.encodeBase64String(signedBytes);
    } catch (Exception e) {
      e.printStackTrace();
    }
    return signatureString;
  }
}