X.509 证书的 Java 1.7 主题哈希 OpenSSL 1.0+ 兼容

我已经为此苦苦挣扎了几天。我正在开发一个在嵌入式 Linux 环境中运行的 Java 1.7 应用程序。 OpenSSL 不可用，我无法控制设备上操作系统映像中的内容。我需要计算自签名 X.509 证书的主题哈希，生成与 OpenSSL 1.0+ 相同的结果。这个现有的答案让我开始：

新的主题散列 openssl 算法有所不同 https://stackoverflow.com/questions/19237167/the-new-subject-hash-openssl-algorithm-differs

我的测试应用程序的代码如下所示。我的计算适用于主题名称仅包含 CN 值的证书，但不适用于指定了任何其他主题组件（OU、O、L、ST 或 C）的证书。对于这些证书，整个主题的哈希值（减去介绍序列）不匹配。根据上面的答案，我提取了每个组件（使用 getObjectAt( ) 方法）并单独对每个组件进行哈希处理（没有乐趣），颠倒它们的顺序并对它们全部进行哈希处理（没有乐趣），以及其他一些变体主题。我一直在努力避免下载 OpenSSL 源代码并运行它，这样我就可以检查中间结果并看看哪里出了问题，这会是我担心的更耗时的工作。也许做过这件事的人可以提供一些指导。

private static void getSubjectHash( X509Certificate x509Cert )
{
    try {
        // get the subject principal
        X500Principal x500Princ = x509Cert.getSubjectX500Principal( );

        // create a new principal using canonical name (order, spacing, etc.) and get it in ANS1 DER format
        byte[] newPrincEnc = new X500Principal( x500Princ.getName( X500Principal.CANONICAL ) ).getEncoded( );

        // read it in as an ASN1 Sequence to avoid custom parsing
        ASN1InputStream aIn = new ASN1InputStream( newPrincEnc );
        ASN1Sequence seq = (ASN1Sequence) aIn.readObject( );

        List<byte[]> terms = new ArrayList<>( );
        int finalLen = 0;
        int i = 0;

        // hash the encodables for each term individually and accumulate them in a list
        for ( ASN1Encodable asn1Set : seq.toArray( ) ) {
            byte[] term = ( (ASN1Set) asn1Set ).getEncoded( );
            terms.add( term );
            finalLen += term.length;

            // digest the term
            byte[] hashBytes = truncatedHash( getDigest( term ), 4 );
            printByteArray( String.format( "hash of object at %d:", i++ ), hashBytes );

            System.out.println( "" );
        }


        // hash all terms together in order of appearance
        int j = 0;
        byte[] finalEncForw = new byte[finalLen];
        for ( byte[] term : terms )
            for ( byte b : term )
                finalEncForw[j++] = b;

        // digest and truncate
        byte[] hashBytes = truncatedHash( getDigest( finalEncForw ), 4 );

        printByteArray( "hash of all terms in forward order", hashBytes );
        System.out.println( "" );


        // hash all terms together in reverse order
        j = 0;
        byte[] finalEncRev = new byte[finalLen];
        for ( int k = terms.size( ) - 1; k >= 0; --k )
            for ( byte b : terms.get( k ) )
                finalEncRev[j++] = b;

        // digest and truncate
        hashBytes = truncatedHash( getDigest( finalEncRev ), 4 );

        printByteArray( "hash of all terms in reverse order", hashBytes );
    }
    catch ( Exception ex ) {
        throw new RuntimeException( "uh-oh" );
    }
}

private static byte[] getDigest( byte[] toHash )
{
    MessageDigest md;

    try {
        md = MessageDigest.getInstance( "SHA1" );
    }
    catch ( NoSuchAlgorithmException nsa ) {
        throw new RuntimeException( "no such algorithm" );
    }

    return md.digest( toHash );
}

private static byte[] truncatedHash( byte[] hash, int truncatedLength )
{
    if ( truncatedLength < 1 || hash.length < 1 )
        return new byte[0];

    byte[] result = new byte[truncatedLength];

    for ( int i = 0; i < truncatedLength; ++i )
        result[truncatedLength - 1 - i] = hash[i];

    return result;
}

private static void printByteArray( String name, byte[] bytes )
{
    System.out.println( name + " length=" + String.valueOf( bytes.length ) );
    for ( byte b: bytes ) {
        System.out.print( String.format( "%02X ", Byte.toUnsignedInt( b ) ) );
    }

    System.out.println( );
}

好的，现在是管道胶带。这似乎适用于我可测试的所有证书。这是 getSubjectHash 方法的重写版本：

private static void getSubjectHash( X509Certificate x509Cert )
{
    try {
        // get the subject principal
        X500Principal x500Princ = x509Cert.getSubjectX500Principal( );

        // create a new principal using canonical name (order, spacing, etc.) and get it in ANS1 DER format
        byte[] newPrincEnc = new X500Principal( x500Princ.getName( X500Principal.CANONICAL ) ).getEncoded( );

        // read it in as an ASN1 Sequence to avoid custom parsing
        ASN1InputStream aIn = new ASN1InputStream( newPrincEnc );
        ASN1Sequence seq = (ASN1Sequence) aIn.readObject( );

        List<byte[]> terms = new ArrayList<>( );
        int finalLen = 0;
        int i = 0;

        // hash the encodables for each term individually and accumulate them in a list
        for ( ASN1Encodable asn1Set : seq.toArray( ) ) {
            byte[] term = ( (ASN1Set) asn1Set ).getEncoded( );
            term[9] = 0x0c; // change tag from 0x13 (printable string) to 0x0c
            terms.add( term );
            finalLen += term.length;

            // digest the term
            byte[] hashBytes = truncatedHash( getDigest( term ), 4 );
            printByteArray( String.format( "hash of object at %d:", i++ ), hashBytes );

            System.out.println( "" );
        }


        // hash all terms together in order of appearance
        int j = 0;
        byte[] finalEncForw = new byte[finalLen];
        for ( byte[] term : terms )
            for ( byte b : term )
                finalEncForw[j++] = b;

        // digest and truncate
        byte[] hashBytes = truncatedHash( getDigest( finalEncForw ), 4 );

        printByteArray( "hash of all terms in forward order", hashBytes );
        System.out.println( "" );

    }
    catch ( Exception ex ) {
        throw new RuntimeException( "uh-oh" );
    }
}