自签名应用 itext 5.5.11 以来，文档已被更改或损坏

Question

基本上我收到错误文档已被更改或损坏，因为应用了签名，我按照 itext 网站的示例并适应了我的情况。

准备待签名文档，添加追加模式，因为可以一份已经签署的文件
调用网络服务对哈希进行签名
向准备好的文档添加了签名哈希

我运行没有想法，希望能得到一些帮助这是我的代码片段：

    public static final String src = "DynamicClient\sample.pdf";
    public static final String temp= "DynamicClient\sampleTEMP.pdf";
    public static final String dest= "DynamicClient\sampleFINAL.pdf";

    public static void emptySignatureSVC(String src, String dest, String fieldname, Certificate[] chain) throws IOException, DocumentException, GeneralSecurityException {
            PdfReader reader = new PdfReader(src);
            reader.setAppendable(true);
            FileOutputStream os = new FileOutputStream(dest);
            PdfStamper stamper = PdfStamper.createSignature(reader, os, '[=10=]',null,true);
            PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
            appearance.setVisibleSignature(new Rectangle(0, 0, 0, 0), 1, fieldname);
            appearance.setCertificate(chain[0]);
            ExternalSignatureContainer external = new ExternalBlankSignatureContainer(PdfName.ADOBE_PPKLITE, PdfName.ETSI_CADES_DETACHED);
            MakeSignature.signExternalContainer(appearance, external, 8192);
            reader.close();
            
        }

    public static void createSignatureSVC(String src, String dest, String fieldname, byte[] sign, Certificate[] chain) throws IOException, DocumentException, GeneralSecurityException {
            
            PdfReader reader = new PdfReader(src);
            FileOutputStream os = new FileOutputStream(dest);
            ExternalSignatureContainer external = new MyExternalSignatureContainer(sign, chain);
            MakeSignature.signDeferred(reader, fieldname, os, external);
        }


    public static void main(String[] args) throws Exception {

                Certificate[] chain = signWS.getChain();//External WS to get chain
                emptySignatureSVC(src, temp, "signature", chain);               
                InputStream is = new FileInputStream(new File(temp));
                PdfPKCS7 sgn = new PdfPKCS7(null, chain, "SHA256", null, digest, false);
                byte[] hash = DigestAlgorithms.digest(is, digest.getMessageDigest("SHA256"));
                byte[] sh = sgn.getAuthenticatedAttributeBytes(hash, null, null, CryptoStandard.CADES);
                
                byte[] extSignature = signWS(sh);//External WS to sign
                sgn.setExternalDigest(extSignature, null, "RSA");
    
                createSignatureSVC(temp, dest, "signature", sgn.getEncodedPKCS7(hash,null, null, null, CryptoStandard.CADES), chain);
}

文件如下： original one Signed one

编辑： 忘记添加我使用的容器：

class MyExternalSignatureContainer implements ExternalSignatureContainer {
    protected byte[] sig;
    protected Certificate[] chain;
    public MyExternalSignatureContainer(byte[] sig,Certificate[] chain) {
        this.sig = sig;
        this.chain=chain;
    }
    public byte[] sign(InputStream is)throws GeneralSecurityException  {
        
        return sig;
        
    }

    @Override
    public void modifySigningDictionary(PdfDictionary signDic) {
        // TODO Auto-generated method stub
        
    }
}

Answer 1

试试这个

public static final String src = "DynamicClient\sample.pdf";
public static final String temp= "DynamicClient\sampleTEMP.pdf";
public static final String dest= "DynamicClient\sampleFINAL.pdf";

public byte[] emptySignatureSVC(String src, String dest, String fieldname, Certificate[] chain) throws IOException, DocumentException, GeneralSecurityException {
    PdfReader reader = new PdfReader(src);
    reader.setAppendable(true);
    FileOutputStream os = new FileOutputStream(dest);
    PdfStamper stamper = PdfStamper.createSignature(reader, os, '[=10=]',null,true);
    PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
    appearance.setVisibleSignature(new Rectangle(0, 0, 0, 0), 1, fieldname);
    appearance.setCertificate(chain[0]);
    ExternalSignatureContainer external = new ExternalBlankSignatureContainer(PdfName.ADOBE_PPKLITE, PdfName.ETSI_CADES_DETACHED);
    MakeSignature.signExternalContainer(appearance, external, 8192);
    InputStream inp = appearance.getRangeStream();  
    
    BouncyCastleDigest digest = new BouncyCastleDigest();
    
    reader.close();
    byte[] hash = DigestAlgorithms.digest(inp, digest.getMessageDigest("SHA256"));
     
    return hash;
}

public byte[] signed_hash(byte[] hash, PrivateKey pk, Certificate[] chain) throws GeneralSecurityException {
    PrivateKeySignature signature = new PrivateKeySignature(pk, "SHA256", "SunPKCS11-eToken");
    BouncyCastleDigest digest = new BouncyCastleDigest();
    Calendar cal = Calendar.getInstance();
    String hashAlgorithm = signature.getHashAlgorithm();
    System.out.println(hashAlgorithm);
    PdfPKCS7 sgn = new PdfPKCS7(null, chain, "SHA256", null, digest, false);

    byte[] sh = sgn.getAuthenticatedAttributeBytes(hash, cal, null, null, CryptoStandard.CMS);
    byte[] extSignature = signature.sign(sh);

    System.out.println(signature.getEncryptionAlgorithm());
    sgn.setExternalDigest(extSignature, null, signature.getEncryptionAlgorithm());
    return sgn.getEncodedPKCS7(hash, cal, null, null, null, CryptoStandard.CMS);
}

public static void createSignatureSVC(String src, String dest, String fieldname, byte[] sign, Certificate[] chain) throws IOException, DocumentException, GeneralSecurityException {
    PdfReader reader = new PdfReader(src);
    FileOutputStream os = new FileOutputStream(dest);
    ExternalSignatureContainer external = new MyExternalSignatureContainer(sign, chain);
    MakeSignature.signDeferred(reader, fieldname, os, external);
}

public static void main(String[] args) throws IOException, GeneralSecurityException, DocumentException {
    byte[] hh = emptySignatureSVC(src, temp, "sig1", chain);
    byte[] hh_sign = (app.signed_hash(hh,  pk,  chain));
    createSignatureSVC(temp, dest, "sig1",hh_sign,  chain);
}

Answer 2

您的代码中有两个问题：

你散列了错误的数据并且
您签名不正确。

散列错误数据

您正在像这样散列整个准备好的 PDF：

InputStream is = new FileInputStream(new File(temp));
PdfPKCS7 sgn = new PdfPKCS7(null, chain, "SHA256", null, digest, false);
byte[] hash = DigestAlgorithms.digest(is, digest.getMessageDigest("SHA256"));

这是不正确的。

签名的 PDF 基本上具有以下结构（阅读 here 了解更多详情）：

（顺便说一句，草图不是 100% 正确的，因为签名值周围的尖括号分隔符“<”和“>”也不能被散列。）

您在 temp 准备的 PDF 具有相同的结构，只是“签名值”还不是实际的签名值，而是 8192 十六进制编码零字节的占位符（8192 因为这是您的数字放弃了 MakeSignature.signExternalContainer).

不过，正如您在草图中看到的那样，签名值（或在您的情况下为占位符）不得经过哈希处理以进行签名。

您可以根据@LkbhaiLr 在.

中提出的MakeSignature.signExternalContainer 之后使用PdfSignatureAppearance.getRangeStream 返回的数据计算散列

或者，您可以使用（而不是 ExternalBlankSignatureContainer）自定义 ExternalSignatureContainer 实现，它在其 sign 方法中简单地散列其 InputStream 参数并提供该散列。

我更喜欢后一种方法，但前一种方法也被广泛使用。

签名不正确

您像这样检索裸签名值：

byte[] sh = sgn.getAuthenticatedAttributeBytes(hash, null, null, CryptoStandard.CADES);
byte[] extSignature = signWS(sh);//External WS to sign

即您将属性结构按原样转发给您的签名服务，并期望它为其创建适当的签名值。

检查您的 signed example file，但是，很明显签名服务没有达到您的期望：不是使用 SHA256withRSA signing，它只是 用 RSA 和 PKCS#1 填充加密。因此，它希望您为自己完成一半的签名，即使用 SHA256 进行散列并构建 DigestInfo 结构。

因此，在调用 signWS 之前，您必须对 sgn.getAuthenticatedAttributeBytes 返回的属性结构进行哈希处理，然后将生成的哈希值包装在 DigestInfo 对象中。

当您在别处计算哈希值时，这对您来说应该不是问题。为了将散列包装在 DigestInfo RFC 8017 section 9.2 note 1 中，提供了一个快捷方式：

For the nine hash functions mentioned in Appendix B.1, the DER encoding T of the DigestInfo value is equal to the following:
...
SHA-256: (0x)30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20 || H.
...

即您只需要在哈希前面加上字节序列 30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20.

自签名应用 itext 5.5.11 以来，文档已被更改或损坏

Document has been altered or corruped since the Signature was applied itext 5.5.11

java

pdf

itext

digital-signature

散列错误数据

签名不正确