使用Java将外部PKCS1字节数组和证书添加到CMS容器

Question

我们有创建PKCS1 v2.1数字签名的客户端应用程序(Applets和Silverlight)。数字签名被创建为PKCS1，因为原始内容没有下载到客户端，只有内容的散列被发送到客户端以节省带宽。

我们正在尝试根据这篇文章中的信息创建一个 PKCS7/CMS 容器服务器端：

1. 读取证书并加载为X509证书类型
2. 将PKCS1签名读取为Bas64并加载为字节数组
3. 实例化新的ASN1Object标识符并设置PKCS1 OID（1.2.840.113549.1.1）
4. 使用asn1对象和Signare byte[]作为参数创建新的CMSTyedData CMSProcessableByteArray
5. 创建新的CMSSignedDynamator并添加证书
6. 使用CMSTyedData类型创建新的CMSSignedData作为分离签名

但是，当进入第5步和第6步时，事情会中断，因为BC CMSSignedDynamator和CMSSignedData类不支持在没有私钥的情况下添加签名者：

CMS创建:

    // Add BC to environment
    Security.addProvider(new BouncyCastleProvider());

    // Read certificate and convert to X509Certificate
    CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
    Path certPath = Paths.get("C:\\MyCertificate.cer");
    byte[] certData = Files.readAllBytes(certPath);
    InputStream in = new ByteArrayInputStream(certData);
    X509Certificate cert = (X509Certificate)certFactory.generateCertificate(in);

    // Add signer certificates to List and add them to store
    List<X509Certificate> certList = new ArrayList<X509Certificate>();
    certList.add(cert);
    Store certs = new JcaCertStore(certList);

    // Get signature in Base64, decode and convert to byte array
    // Signature signature = Signature.getInstance("SHA1WithRSA", "BC");
    String signatureBase64 = "gjTbsD0vSOi6nMlRVbpTLRQ5j+g2h8iEH1DgQx93PDBuwzWT47urKxMAS+75dAhQrkreLt9TGZaDN85e5xEpIF12mK1G+AgCNc370I1bjxOvUU67IVxHkZ+IX8kzSiD2uNuQtk3IrwUqyL30TIo+LDAXmY1AQVZwXAaOYG4bXxI=";
    BASE64Decoder decoder = new BASE64Decoder();
    byte[] signatureByte = decoder.decodeBuffer(signatureBase64);

    // Instantiate new ANS1ObjectIdentifier to identify PKCS1 signature
    ASN1ObjectIdentifier asn1OidPkcs1 = new ASN1ObjectIdentifier("1.2.840.113549.1.1");

    // Table generator
    /*AttributeTable attrT = new AttributeTable();
    SimpleAttributeTableGenerator sAttrTGen = new SimpleAttributeTableGenerator();*/

    // Instantiate new CMSProcessable object
    CMSTypedData msg = new CMSProcessableByteArray(asn1OidPkcs1, signatureByte);

    // Instantiate new CMSSignedDataGenerator object
    CMSSignedDataGenerator gen = new CMSSignedDataGenerator();

    // ContentSigner sha1Signer = new JcaContentSignerBuilder("SHA1withRSA").setProvider("BC").s
    gen.addCertificates(certs);
    CMSSignedData sigData = gen.generate(msg, false);


    // BASE64Encoder encoder = new BASE64Encoder();
    new File("C:\\MyCMS.p7s");
    FileOutputStream fileOuputStream = new FileOutputStream("C:\\Users\\gregwerner\\Documents\\Archivos\\miFirma.p7s"); 
    fileOuputStream.write(sigData.getEncoded());
    fileOuputStream.flush();
    fileOuputStream.close();

}

关于如何完成CMS容器有什么想法吗？也许可以使用AttributeTable为时间戳等添加多个OID，但这似乎也不起作用。

Answer 1

我看了这个参考项目后找到了答案https://code.google.com/p/j4ops/.尽管本指南专门处理使用iText的PDF，这些PDF使用加密操作中的BC，但它也是一个很大的帮助：http://itextpdf.com/book/digitalsignatures20130304.pdf.技巧是通过实现使用sign（byte[]toEncrypt）方法的Signer接口，将签名操作委托给外部提供者（PKCS11、PKCS12等）。这样，就可以设置提供者，然后调用sign方法，并将如何签名的实现细节留给提供者本身。

Bouncy Castle 使用 CMSSignedDataGenerator 类和 SignerInf 内部类分别构建 CMS 容器和签名者信息。因此，诀窍是构建一个不需要私钥的 SignerInf 对象，因为 sign（） 操作应该委托给提供者。私钥甚至可能不可用，尤其是在使用智能卡时。此外，在对哈希进行签名和构建 CMS 容器时，需要考虑需要添加为签名属性和/或未签名属性的信息。因此，这些是解决问题的基本步骤：

// Build the items to encrypt, objects for method parameters would be obtained previously.
byte[] toEncrypt = externalSignerInfoGenerator.getCmsBytesToSign(hash, 
            signingTime, 
            PKCSObjectIdentifiers.data, 
            x509Cert, 
            timeStampToken, 
            ocsp);
// The externalSignerInfoGenerator.getCmsBytesToSign is a method from a re implemention of the 
// SignerInf inner class from CMSSignedDataGenerator and is used to get a byte array from an 
// org.bouncycastle.asn1.ASN1EncodableVector. To build the vector one should add attributes to
// their corresponding OID's using the org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers interface,
// for example:
ASN1EncodableVector signedAttrVector = buildSignedAttributes (hash, signingTime, contentType,
x509Cert, ocspResp);
// This would call the buildSignedAttributes method to build the signed attributes vector
ASN1EncodableVector signedAttrVector = new ASN1EncodableVector();
// Add CMS attributes
signedAttrVector.add (new Attribute(CMSAttributes.contentType, new DERSet (contentType)));
signedAttrVector.add (new Attribute (CMSAttributes.signingTime, new DERSet(new Time (signingTime))));
signedAttrVector.add(new Attribute(CMSAttributes.messageDigest, new DERSet(new DEROctetString(hash))));
// Not all attributes are considered in BC's CMSAttributes interface, therefore one would have to add 
// an additional step:
signedAttrVector.add(buildOcspResponseAttribute(ocspResp));
// This method would call buildOcspResponseAttribute to add the object as a PKCSObjectIdentifier
protected Attribute buildOcspResponseAttribute (byte[] ocspResp) throws IOException, CMSException {
    return new Attribute (PKCSObjectIdentifiers.id_aa_ets_revocationRefs, 
    new DERSet(DERUtil.readDERObject(ocspResp)));
}  

// Call sign method from provider, such as PKCS11, PKCS12, etc.
byte [] signature = getSignProvider().sign(toEncrypt);
// Now build standard org.bouncycastle.cms.SignerInfoGenerator with hash, signed data 
// and certificate to add to CMS, create attached or detached signature
// create signed envelope
CMSSignedData envdata = externalCMSSignedDataGenerator.generate(false);                
byte[] enveloped = envdata.getEncoded();