How to load PKCS7 (.p7b) file in java

I have a pkcs7 file, and I want to load it and extract its contents.

I tried these two methods:

byte[] bytes = Files.readAllBytes(Paths.get("myfile.p7b")); FileInputStream fi = new FileInputStream(file); //Creating PKCS7 object PKCS7 pkcs7Signature = new PKCS7(bytes); 

or this

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

but I got IOException: Sequence tag error

So how can I load this .p7b file ?

1 Answer

Finally I did it with BouncyCastle library.

PKCS#7 is a complex format, also called CMS. Sun JCE has no direct support to PKCS#7.

This is the code that I used to extract my content:

// 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(); } 

If you want to verify the signature of this PKCS7 file against X509 certificate, you must add the following code to the while loop:

// ************************************************************* // // ********************* 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 ");