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// SPDX-FileCopyrightText: 2006 Istituto Nazionale di Fisica Nucleare
//
// SPDX-License-Identifier: Apache-2.0
package org.italiangrid.voms.util;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
/**
* A utility class for computing fingerprints of X.509 certificates.
* <p>
* This class provides methods to generate a cryptographic fingerprint (hash) of an X.509
* certificate using a specified digest algorithm.
* </p>
*
* <p>
* The default digest algorithm used is SHA-1.
* </p>
*
*/
public class FingerprintHelper {
/** The default message digest algorithm used for computing fingerprints. */
public static final String DEFAULT_DIGEST_ALGORITHM = "SHA-1";
/**
* Converts a byte array to a hexadecimal string representation.
*
* @param bytes the byte array to convert
* @return a string containing the hexadecimal representation of the byte array
*/
private static String hexify(byte[] bytes) {
char[] hexDigits =
{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
StringBuffer buf = new StringBuffer(bytes.length * 2);
for (int i = 0; i < bytes.length; ++i) {
buf.append(hexDigits[(bytes[i] & 0xf0) >> 4]);
buf.append(hexDigits[bytes[i] & 0x0f]);
}
return buf.toString();
}
/**
* Computes the fingerprint of an X.509 certificate using the default digest algorithm.
*
* @param cert the X.509 certificate for which to compute the fingerprint
* @return the fingerprint of the certificate as a hexadecimal string
* @throws NoSuchAlgorithmException if the specified digest algorithm is not available
* @throws CertificateEncodingException if encoding the certificate fails
*/
public static String getFingerprint(X509Certificate cert)
throws NoSuchAlgorithmException, CertificateEncodingException {
MessageDigest md = MessageDigest.getInstance(DEFAULT_DIGEST_ALGORITHM);
byte[] der = cert.getEncoded();
md.update(der);
byte[] digest = md.digest();
return hexify(digest);
}
}
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