如何在 Java 中加載 PKCS7 (.p7b) 文件

Question

我有一個pkcs7文件，我想加載它並提取其內容。

我試過這兩種方法：

byte[] bytes = Files.readAllBytes(Paths.get("myfile.p7b"));
FileInputStream fi = new FileInputStream(file);

//Creating PKCS7 object
PKCS7 pkcs7Signature = new PKCS7(bytes);

或這個

FileInputStream fis = new FileInputStream(new File("myfile.p7b"));
PKCS7 pkcs7Signature = new PKCS7(fis);

但我得到了IOException: Sequence tag error

那么如何加載這個 .p7b 文件呢？

Answer 1

最后我用 BouncyCastle 庫做到了。

PKCS#7 是一種復雜的格式，也稱為 CMS。 Sun JCE 不直接支持 PKCS#7。

這是我用來提取我的內容的代碼：

// Loading the file first
   File f = new File("myFile.p7b");
   byte[] buffer = new byte[(int) f.length()];
   DataInputStream in = new DataInputStream(new FileInputStream(f));
   in.readFully(buffer);
   in.close();

   //Corresponding class of signed_data is CMSSignedData
   CMSSignedData signature = new CMSSignedData(buffer);
   Store cs = signature.getCertificates();
   SignerInformationStore signers = signature.getSignerInfos();
   Collection c = signers.getSigners();
   Iterator it = c.iterator();

   //the following array will contain the content of xml document
   byte[] data = null;

   while (it.hasNext()) {
        SignerInformation signer = (SignerInformation) it.next();
        Collection certCollection = cs.getMatches(signer.getSID());
        Iterator certIt = certCollection.iterator();
        X509CertificateHolder cert = (X509CertificateHolder) certIt.next();

        CMSProcessable sc = signature.getSignedContent();
        data = (byte[]) sc.getContent();
    }

如果要根據 X509 證書驗證此 PKCS7 文件的簽名，則必須將以下代碼添加到 while 循環中：

// ************************************************************* //
// ********************* Verify signature ********************** //
//get CA public key
// Create a X509 certificat
CertificateFactory certificatefactory = CertificateFactory.getInstance("X.509");

// Open the certificate file
FileInputStream fileinputstream = new FileInputStream("myCA.cert");

//get CA public key
PublicKey pk = certificatefactory.generateCertificate(fileinputstream).getPublicKey();

X509Certificate myCA = new JcaX509CertificateConverter().setProvider("BC").getCertificate(cert);

myCA.verify(pk);
System.out.println("Verfication done successfully ");