使用公钥验证签名 [英] Verifying a signature with a public key

问题描述

我有一个外部服务，在一些已定义的事件后给我回电话，并用私钥签署他的请求。

I have an external service which call me back after some defined event, and sign his request with its private key.

我已经存储了看起来像的公钥：

I have stored the public key which look like :

-----BEGIN PUBLIC KEY-----
........................................
-----END PUBLIC KEY-----

所以我的工作是检查请求的内容是否未通过验证签名进行更改。

So my work is to check if request's content has not been alterned by verifying signature.

这是我的算法：

// 1 - reading public key :
Scanner scanner = new Scanner( new File( keyPath ) );


//            encodedPublicKey.toString( );
StringBuilder sb = new StringBuilder( );
while ( scanner.hasNextLine( ) )
{
    sb.append( scanner.nextLine( ) );
    sb.append( '\n' );
}

byte[] encodedPublicKey = sb.toString( ).getBytes( "utf-8" );

// 2 - loading public key in a relevant object :
X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec( publicKeyBytes );

KeyFactory keyFactory = KeyFactory.getInstance( "DSA" );

PublicKey publicKey = keyFactory.generatePublic( publicKeySpec );

// 3 - verifying content with signature and content :
Signature sig = Signature.getInstance( "SHA1withDSA" );
sig.initVerify( publicKey );
sig.update( message.getBytes( ) );
ret = sig.verify( sign.getBytes( ) );

但是现在我的算法停止在PublicKey publicKey = keyFactory.generatePublic（publicKeySpec）步骤此消息：

But for now my algorithm is stoped at "PublicKey publicKey = keyFactory.generatePublic( publicKeySpec )" step by this message :

java.security.spec.InvalidKeySpecException: Inappropriate key specification: invalid key format

那么如何以java api接受的方式加载我的密钥？

So how can I load my key in a way that is accepted by java api ?

推荐答案

实际上我找到了解决方案。

Actually I've found the solution.

问题是以正确的方式加载公钥文件。

The problem was to load in the public key file in the right way.

I'va将bouncycastle库添加到我的依赖项中：

I'va added bouncycastle library to my dependencies :

<dependency>
  <groupId>org.bouncycastle</groupId>
  <artifactId>bcprov-jdk15on</artifactId>
  <version>1.47</version>
</dependency>

它提供了允许读取和加载非认证公钥的PemReader。

It provides PemReader which allows to read and load non certificated public keys.

这是我的实用程序类：

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.X509EncodedKeySpec;

import org.bouncycastle.util.io.pem.PemReader;
import org.castor.util.Base64Decoder;

import fr.paris.lutece.portal.service.util.AppLogService;


/**
 * Classe d'aide à l'interfacage avec le service paybox.
 *
 * Toutes les informations parameterables sont sous la forme paybox.*
 */
public final class PayboxUtil
{

    /** The Constant CHARSET. */
    private static final String CHARSET = "utf-8";

    /** The Constant ENCRYPTION_ALGORITHM. */
    private static final String ENCRYPTION_ALGORITHM = "RSA";

    /** The Constant HASH_ENCRIPTION_ALGORITHM. */
    private static final String HASH_ENCRYPTION_ALGORITHM = "SHA1withRSA";

    /**
     * constructeur privé pour classe statique.
     */
    private PayboxUtil(  )
    {
    }

    /**
     * Controle si une signature est bien celle du message à l'aide de la clé
     * publique de l'emmeteur?.
     *
     * @param message le message
     * @param sign la signature
     * @param keyPath le chemin vers la clé publique.
     * @return true si la signature est bien celle du message avec la clé privé
     *         attendue.
     */
    public static boolean checkSign( String message, String sign, String keyPath )
    {
        boolean ret = false;

        try
        {
            ret = PayboxUtil.verify( message, sign, PayboxUtil.getKey( keyPath ) );
        }
        catch ( final FileNotFoundException e )
        {
            AppLogService.error( e );
        }
        catch ( final IOException e )
        {
            AppLogService.error( e );
        }
        catch ( final NoSuchAlgorithmException e )
        {
            AppLogService.error( e );
        }
        catch ( final InvalidKeySpecException e )
        {
            AppLogService.error( e );
        }
        catch ( final InvalidKeyException e )
        {
            AppLogService.error( e );
        }
        catch ( final SignatureException e )
        {
            AppLogService.error( e );
        }

        return ret;
    }


    /**
     * Récupère la clé publique à partir du chemin passé en paramètre.
     *
     * @param keyPath le chemin vers la clé.
     * @return la clé publique
     * @throws NoSuchAlgorithmException the no such algorithm exception
     * @throws IOException Signals that an I/O exception has occurred.
     * @throws InvalidKeySpecException the invalid key spec exception
     */
    private static PublicKey getKey( String keyPath )
        throws NoSuchAlgorithmException, IOException, InvalidKeySpecException
    {
        final KeyFactory keyFactory = KeyFactory.getInstance( PayboxUtil.ENCRYPTION_ALGORITHM );
        final PemReader reader = new PemReader( new FileReader( keyPath ) );
        final byte[] pubKey = reader.readPemObject(  ).getContent(  );
        final X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec( pubKey );

        return keyFactory.generatePublic( publicKeySpec );
    }

    /**
     * effectue la vérification du message en fonction de la signature et de la
     * clé.
     *
     * @param message le message
     * @param sign la signature
     * @param publicKey la clé publique.
     * @return true, if successful
     * @throws NoSuchAlgorithmException the no such algorithm exception
     * @throws InvalidKeyException the invalid key exception
     * @throws SignatureException the signature exception
     * @throws UnsupportedEncodingException the unsupported encoding exception
     */
    private static boolean verify( String message, String sign, PublicKey publicKey )
        throws NoSuchAlgorithmException, InvalidKeyException, SignatureException, UnsupportedEncodingException
    {
        final Signature sig = Signature.getInstance( PayboxUtil.HASH_ENCRYPTION_ALGORITHM );
        sig.initVerify( publicKey );
        sig.update( message.getBytes( PayboxUtil.CHARSET ) );

        final byte[] bytes = Base64Decoder.decode( URLDecoder.decode( sign, PayboxUtil.CHARSET ) );

        return sig.verify( bytes );
    }
}

您只需传递已签名的内容，签名和密钥checkSign方法的路径，它完成所有工作。

You just have to pass signed content, signature and key path to checkSign method and it does all the work.

这篇关于使用公钥验证签名的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！