如何解决自应用签名以来文档已被更改或损坏 itext 5.5.11 散列错误数据签名不正确
基本上我得到错误自从应用签名以来文档已被更改或损坏,我按照itext网站的示例并适应了我的情况。
- 准备要签名的文档,添加append模式,因为它可以 已签署的文件
- 调用网络服务对哈希进行签名
- 为准备好的文档添加了签名哈希
我的想法用完了,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,'\0',null,true);
PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
appearance.setVisibleSignature(new Rectangle(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,byte[] sign,GeneralSecurityException {
PdfReader reader = new PdfReader(src);
FileOutputStream os = new FileOutputStream(dest);
ExternalSignatureContainer external = new MyExternalSignatureContainer(sign,chain);
MakeSignature.signDeferred(reader,fieldname,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",digest,false);
byte[] hash = DigestAlgorithms.digest(is,digest.getMessageDigest("SHA256"));
byte[] sh = sgn.getAuthenticatedAttributeBytes(hash,CryptoStandard.CADES);
byte[] extSignature = signWS(sh);//External WS to sign
sgn.setExternalDigest(extSignature,"RSA");
createSignatureSVC(temp,dest,sgn.getEncodedPKCS7(hash,CryptoStandard.CADES),chain);
}
这里是文件: 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
}
}
解决方法
您的代码中有两个问题:
- 您散列了错误的数据,并且
- 您的签名有误。
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 本质上具有以下结构(阅读 here 了解更多详细信息):
(顺便说一下,草图不是 100% 正确的,因为签名值周围的尖括号分隔符 '' 也不能散列。)
您在 temp
处准备的 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 个十六进制编码的零字节的占位符(8192 因为这是您提供的数字) MakeSignature.signExternalContainer
).
不过,正如您在草图中看到的,签名值(或在您的情况下,占位符)不得为签名而散列。
您可以使用@LkbhaiLr 在his answer 中提出的PdfSignatureAppearance.getRangeStream
之后的MakeSignature.signExternalContainer
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,该实现在其 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
您可以像这样检索裸签名值:
byte[] sh = sgn.getAuthenticatedAttributeBytes(hash,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,该签名服务不符合您的期望:它不是使用 SHA256withRSA 签名,而是加密 使用 RSA 和 PKCS#1 填充。因此,它希望您为您完成一半的签名工作,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散列,然后将生成的散列值包装在 DigestInfo
对象中。
当您在其他地方计算哈希值时,这对您来说应该不是问题。将散列包装在 DigestInfo
RFC 8017 section 9.2 note 1 中提供了一个捷径:
对于附录 B.1 中提到的九个哈希函数,DigestInfo
值的 DER 编码 T 等于:
...
SHA-256: (0x)30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20 || H.
...
即你只需要用字节序列 30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20
为你的哈希做前缀。
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,'\0',true);
PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
appearance.setVisibleSignature(new Rectangle(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,"SunPKCS11-eToken");
BouncyCastleDigest digest = new BouncyCastleDigest();
Calendar cal = Calendar.getInstance();
String hashAlgorithm = signature.getHashAlgorithm();
System.out.println(hashAlgorithm);
PdfPKCS7 sgn = new PdfPKCS7(null,false);
byte[] sh = sgn.getAuthenticatedAttributeBytes(hash,cal,CryptoStandard.CMS);
byte[] extSignature = signature.sign(sh);
System.out.println(signature.getEncryptionAlgorithm());
sgn.setExternalDigest(extSignature,signature.getEncryptionAlgorithm());
return sgn.getEncodedPKCS7(hash,CryptoStandard.CMS);
}
public static void createSignatureSVC(String src,byte[] sign,GeneralSecurityException {
PdfReader reader = new PdfReader(src);
FileOutputStream os = new FileOutputStream(dest);
ExternalSignatureContainer external = new MyExternalSignatureContainer(sign,chain);
MakeSignature.signDeferred(reader,fieldname,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,hh_sign,chain);
}
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