从文件摘要创建 pkcs7 签名

Question

目前我有一个客户端-服务器应用程序，给定一个 PDF 文件，对其进行签名（使用服务器证书），将签名附加到原始文件并将 returns 输出返回给客户端（所有这是通过 PDFBox 实现的）。
我有一个签名处理程序，这是我的外部签名支持（其中内容是 PDF 文件）

    public byte[] sign(InputStream content) throws IOException {
    try {
        System.out.println("Generating CMS signed data");
        CMSSignedDataGenerator generator = new CMSSignedDataGenerator();
        ContentSigner sha1Signer = new JcaContentSignerBuilder("Sha1WithRSA").build(privateKey);
        generator.addSignerInfoGenerator(
                new JcaSignerInfoGeneratorBuilder(new JcaDigestCalculatorProviderBuilder().build())
                        .build(sha1Signer, new X509CertificateHolder(certificate.getEncoded())));
        CMSTypedData cmsData = new CMSProcessableByteArray(IOUtils.toByteArray(content));
        CMSSignedData signedData = generator.generate(cmsData, false);

        return signedData.getEncoded();
    } catch (GeneralSecurityException e) {
        throw new IOException(e);
    } catch (CMSException e) {
        throw new IOException(e);
    } catch (OperatorCreationException e) {
        throw new IOException(e);
    }
}

它工作正常，但我在想 - 如果 PDF 文件太大而无法上传怎么办？例如：100mb...这将需要很长时间！鉴于此，我想弄清楚，如果不是签署 PDF 文件，是否可以只签署该文件的哈希值（ex SHA1），而不是客户端最后将它们放在一起？

更新：

我一直在想办法，现在我的签名方法是：

    @Override
public byte[] sign(InputStream content) throws IOException {
    // testSHA1WithRSAAndAttributeTable
    try {
        MessageDigest md = MessageDigest.getInstance("SHA1", "BC");
        List<Certificate> certList = new ArrayList<Certificate>();
        CMSTypedData msg = new CMSProcessableByteArray(IOUtils.toByteArray(content));

        certList.add(certificate);

        Store certs = new JcaCertStore(certList);

        CMSSignedDataGenerator gen = new CMSSignedDataGenerator();

        Attribute attr = new Attribute(CMSAttributes.messageDigest,
                new DERSet(new DEROctetString(md.digest(IOUtils.toByteArray(content)))));

        ASN1EncodableVector v = new ASN1EncodableVector();

        v.add(attr);

        SignerInfoGeneratorBuilder builder = new SignerInfoGeneratorBuilder(new BcDigestCalculatorProvider())
                .setSignedAttributeGenerator(new DefaultSignedAttributeTableGenerator(new AttributeTable(v)));

        AlgorithmIdentifier sha1withRSA = new DefaultSignatureAlgorithmIdentifierFinder().find("SHA1withRSA");

        CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
        InputStream in = new ByteArrayInputStream(certificate.getEncoded());
        X509Certificate cert = (X509Certificate) certFactory.generateCertificate(in);

        gen.addSignerInfoGenerator(builder.build(
                new BcRSAContentSignerBuilder(sha1withRSA,
                        new DefaultDigestAlgorithmIdentifierFinder().find(sha1withRSA))
                                .build(PrivateKeyFactory.createKey(privateKey.getEncoded())),
                new JcaX509CertificateHolder(cert)));

        gen.addCertificates(certs);

        CMSSignedData s = gen.generate(new CMSAbsentContent(), false);
        return new CMSSignedData(msg, s.getEncoded()).getEncoded();

    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        throw new IOException(e);
    }

}

我正在使用 pdfbox 将签名与 PDF 合并

            ExternalSigningSupport externalSigning = document.saveIncrementalForExternalSigning(output);
        byte[] cmsSignature = sign(externalSigning.getContent());
        externalSigning.setSignature(cmsSignature);

问题是 Adobe 说签名无效，因为 "document has been altered or corrupted since it was signed"。有人可以帮忙吗？

Answer 1

OP 在他的更新中几乎是正确的，只有两个错误：

他尝试读取InputStream参数内容两次：

CMSTypedData msg = new CMSProcessableByteArray(IOUtils.toByteArray(content));
[...]
Attribute attr = new Attribute(CMSAttributes.messageDigest,
        new DERSet(new DEROctetString(md.digest(IOUtils.toByteArray(content)))));

因此，在第二次尝试返回空值 byte[] 之前，所有数据都已从流中读取。因此消息摘要属性包含错误的哈希值。

他以一种复杂的方式创建了最终的 CMS 容器：

return new CMSSignedData(msg, s.getEncoded()).getEncoded();

将后者减少到实际需要的，事实证明不再需要CMSTypedData msg了。因此，前者被隐式解析。

在 re-arranging 摘要计算到方法顶部之后，另外切换到 SHA256（因为 SHA1 在许多情况下已被弃用，我更喜欢使用不同的哈希算法）并允许证书 chain 而不是单个 certificate，该方法如下所示：

// Digest generation step
MessageDigest md = MessageDigest.getInstance("SHA256", "BC");
byte[] digest = md.digest(IOUtils.toByteArray(content));

// Separate signature container creation step
List<Certificate> certList = Arrays.asList(chain);
JcaCertStore certs = new JcaCertStore(certList);

CMSSignedDataGenerator gen = new CMSSignedDataGenerator();

Attribute attr = new Attribute(CMSAttributes.messageDigest,
        new DERSet(new DEROctetString(digest)));

ASN1EncodableVector v = new ASN1EncodableVector();

v.add(attr);

SignerInfoGeneratorBuilder builder = new SignerInfoGeneratorBuilder(new BcDigestCalculatorProvider())
        .setSignedAttributeGenerator(new DefaultSignedAttributeTableGenerator(new AttributeTable(v)));

AlgorithmIdentifier sha256withRSA = new DefaultSignatureAlgorithmIdentifierFinder().find("SHA256withRSA");

CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
InputStream in = new ByteArrayInputStream(chain[0].getEncoded());
X509Certificate cert = (X509Certificate) certFactory.generateCertificate(in);

gen.addSignerInfoGenerator(builder.build(
        new BcRSAContentSignerBuilder(sha256withRSA,
                new DefaultDigestAlgorithmIdentifierFinder().find(sha256withRSA))
                        .build(PrivateKeyFactory.createKey(pk.getEncoded())),
        new JcaX509CertificateHolder(cert)));

gen.addCertificates(certs);

CMSSignedData s = gen.generate(new CMSAbsentContent(), false);
return s.getEncoded();

(CreateSignature方法signWithSeparatedHashing)

在相当小的签名代码框架中使用

void sign(PDDocument document, OutputStream output, SignatureInterface signatureInterface) throws IOException
{
    PDSignature signature = new PDSignature();
    signature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);
    signature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);
    signature.setName("Example User");
    signature.setLocation("Los Angeles, CA");
    signature.setReason("Testing");
    signature.setSignDate(Calendar.getInstance());
    document.addSignature(signature);
    ExternalSigningSupport externalSigning =
            document.saveIncrementalForExternalSigning(output);
    byte[] cmsSignature = signatureInterface.sign(externalSigning.getContent());
    externalSigning.setSignature(cmsSignature);
}

(CreateSignature方法sign)

像这样

try (   InputStream resource = getClass().getResourceAsStream("test.pdf");
        OutputStream result = new FileOutputStream(new File(RESULT_FOLDER, "testSignedWithSeparatedHashing.pdf"));
        PDDocument pdDocument = PDDocument.load(resource)   )
{
    sign(pdDocument, result, data -> signWithSeparatedHashing(data));
}

(CreateSignature测试方法testSignWithSeparatedHashing)

生成正确签名的 PDF，至少与所讨论的证书和私钥适用于手头的任务一样正确。

一句话：

OP 使用了 IOUtils.toByteArray(content))（我在上面的代码中也是如此）。但考虑到 OP 的开始评论

what if the PDF file is too big to be uploaded? ex: 100mb

这样做并不是一个好主意，因为它会将一个大文件一次加载到内存中，只是为了散列。如果真的想考虑一个应用程序的资源足迹，应该一次读取几 KB 的流并使用 MessageDigest.update 连续消化数据，最后只使用 MessageDigest.digest 来获得结果哈希值。

从文件摘要创建 pkcs7 签名

Create pkcs7 signature from file digest

java

pdfbox

pkcs#7