android: Add local certificate store
The class manages certificates stored in files within the app's private data directory.
This commit is contained in:
Tobias Brunner
parent
463a6cd005
commit
275888d255
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/*
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* Copyright (C) 2014 Tobias Brunner
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* Hochschule fuer Technik Rapperswil
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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package org.strongswan.android.security;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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import java.security.cert.Certificate;
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import java.security.cert.CertificateEncodingException;
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import java.security.cert.CertificateException;
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import java.security.cert.CertificateFactory;
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import java.security.cert.X509Certificate;
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import java.util.ArrayList;
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import java.util.Date;
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import java.util.regex.Pattern;
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import org.strongswan.android.logic.StrongSwanApplication;
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import org.strongswan.android.utils.Utils;
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import android.content.Context;
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public class LocalCertificateStore
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{
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private static final String FILE_PREFIX = "certificate-";
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private static final String ALIAS_PREFIX = "local:";
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private static final Pattern ALIAS_PATTERN = Pattern.compile("^" + ALIAS_PREFIX + "[0-9a-f]{40}$");
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/**
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* Add the given certificate to the store
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* @param cert the certificate to add
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* @return true if successful
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*/
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public boolean addCertificate(Certificate cert)
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{
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if (!(cert instanceof X509Certificate))
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{ /* only accept X.509 certificates */
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return false;
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}
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String keyid = getKeyId(cert);
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if (keyid == null)
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{
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return false;
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}
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FileOutputStream out;
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try
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{
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/* we replace any existing file with the same alias */
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out = StrongSwanApplication.getContext().openFileOutput(FILE_PREFIX + keyid, Context.MODE_PRIVATE);
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try
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{
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out.write(cert.getEncoded());
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return true;
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}
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catch (CertificateEncodingException e)
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{
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e.printStackTrace();
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}
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catch (IOException e)
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{
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e.printStackTrace();
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}
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finally
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{
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try
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{
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out.close();
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}
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catch (IOException e)
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{
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e.printStackTrace();
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}
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}
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}
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catch (FileNotFoundException e)
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{
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e.printStackTrace();
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}
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return false;
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}
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/**
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* Delete the certificate with the given alias
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* @param alias a certificate's alias
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*/
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public void deleteCertificate(String alias)
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{
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if (ALIAS_PATTERN.matcher(alias).matches())
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{
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alias = alias.substring(ALIAS_PREFIX.length());
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StrongSwanApplication.getContext().deleteFile(FILE_PREFIX + alias);
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}
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}
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/**
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* Retrieve the certificate with the given alias
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* @param alias a certificate's alias
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* @return certificate object or null
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*/
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public X509Certificate getCertificate(String alias)
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{
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if (!ALIAS_PATTERN.matcher(alias).matches())
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{
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return null;
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}
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alias = alias.substring(ALIAS_PREFIX.length());
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try
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{
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FileInputStream in = StrongSwanApplication.getContext().openFileInput(FILE_PREFIX + alias);
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try
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{
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CertificateFactory factory = CertificateFactory.getInstance("X.509");
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X509Certificate certificate = (X509Certificate)factory.generateCertificate(in);
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return certificate;
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}
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catch (CertificateException e)
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{
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e.printStackTrace();
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}
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finally
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{
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try
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{
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in.close();
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}
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catch (IOException e)
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{
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e.printStackTrace();
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}
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}
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}
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catch (FileNotFoundException e)
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{
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e.printStackTrace();
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}
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return null;
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}
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/**
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* Returns the creation date of the certificate with the given alias
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* @param alias certificate alias
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* @return creation date or null if not found
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*/
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public Date getCreationDate(String alias)
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{
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if (!ALIAS_PATTERN.matcher(alias).matches())
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{
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return null;
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}
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alias = alias.substring(ALIAS_PREFIX.length());
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File file = StrongSwanApplication.getContext().getFileStreamPath(FILE_PREFIX + alias);
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return file.exists() ? new Date(file.lastModified()) : null;
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}
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/**
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* Returns a list of all known certificate aliases
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* @return list of aliases
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*/
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public ArrayList<String> aliases()
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{
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ArrayList<String> list = new ArrayList<String>();
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for (String file : StrongSwanApplication.getContext().fileList())
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{
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if (file.startsWith(FILE_PREFIX))
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{
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list.add(ALIAS_PREFIX + file.substring(FILE_PREFIX.length()));
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}
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}
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return list;
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}
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/**
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* Check if the store contains a certificate with the given alias
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* @param alias certificate alias
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* @return true if the store contains the certificate
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*/
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public boolean containsAlias(String alias)
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{
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return getCreationDate(alias) != null;
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}
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/**
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* Returns a certificate alias based on a SHA-1 hash of the public key.
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*
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* @param cert certificate to get an alias for
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* @return hex encoded alias, or null if failed
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*/
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public String getCertificateAlias(Certificate cert)
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{
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String keyid = getKeyId(cert);
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return keyid != null ? ALIAS_PREFIX + keyid : null;
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}
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/**
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* Calculates the SHA-1 hash of the public key of the given certificate.
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* @param cert certificate to get the key ID from
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* @return hex encoded SHA-1 hash of the public key or null if failed
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*/
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private String getKeyId(Certificate cert)
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{
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MessageDigest md;
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try
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{
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md = java.security.MessageDigest.getInstance("SHA1");
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byte[] hash = md.digest(cert.getPublicKey().getEncoded());
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return Utils.bytesToHex(hash);
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}
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catch (NoSuchAlgorithmException e)
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{
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e.printStackTrace();
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}
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return null;
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}
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}
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