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java – 从文件摘要创建pkcs7签名

2019-09-30 17:02:30 作者：互联网

目前我有一个客户端 – 服务器应用程序,给定一个PDF文件,签名(使用服务器证书),将签名附加到原始文件并将输出返回给客户端(所有这一切都通过PDFBox实现).

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 ……这需要永远！
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(前SHA1),而不是客户端最终将它们全部放在一起？

更新：

我一直试图解决这个问题,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PDF签名与PDF合并

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

问题是Adobe表示签名无效,因为“文档自签名后已被更改或损坏”.
有人可以帮忙吗？

解决方法:

在他的更新中,OP几乎是正确的,只有两个错误：

>他尝试两次读取InputStream参数内容：

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

因此,在第二次尝试之前已经从流中读取了所有数据,因此返回空字节[].因此,消息摘要属性包含错误的哈希值.
>他以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,结果证明不再需要CMSTypedData消息.因此,前者被隐含地解决了.

在将摘要计算重新安排到方法的顶部并且另外切换到SHA256之后(因为在许多上下文中不推荐使用SHA1,我更喜欢使用不同的哈希算法)并且允许使用证书链而不是单个证书,看起来像这样：

// 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)

用于相当小的签名代码框架

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方法标志)

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)

导致正确签名的PDF,至少正如所讨论的证书和私钥适用于手头的任务.

一句话：

OP使用了IOUtils.toByteArray(内容))(我在上面的代码中也是如此).但考虑到OP的首发言论

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

这样做并不是一个好主意,因为它只会立即将大文件加载到内存中进行散列.如果一个人真的想要考虑一个应用程序的资源占用空间,那么应该一次读取几KB的流并使用MessageDigest.update连续地消化数据,并且仅在末尾使用MessageDigest.digest来获取结果散列值.

标签：java,pdfbox,pkcs7
来源： https://codeday.me/bug/20190930/1836245.html