Java CertPath example: read CertPath from file

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07/27/2010: Posts:
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May 24, 2011 09:15:14 Last update: May 24, 2011 09:15:14

Java built-in X.509 certificate factory reads CertPath objects encoded in PkiPath or PKCS7 formats. The META-INF/<key_alias>.RSA file generated by Java jarsigner is in PKCS7 format.

Example code:

import java.util.*;
import java.io.*;
import java.security.cert.*;

public class ReadCertPath {
    public static void main(String[] args) throws Exception {
	ReadCertPath r = new ReadCertPath();
	r.readCertPath(new File("CertPathInPKCS7.pem"));
    }

    public void readCertPath(File f) throws Exception {
	CertificateFactory cf = CertificateFactory.getInstance("X.509");
	InputStream in = new FileInputStream(f);
	CertPath certPath = cf.generateCertPath(in, "PKCS7");
	in.close();

	List<?extends Certificate> certs = certPath.getCertificates();
	for (Certificate cert: certs) {
	    System.out.println("Cert:\n===================\n" + cert.toString() + "\n");
	}
    }
}

PKCS7 files can also be generated by openssl from certificate file(s):

openssl crl2pkcs7 -nocrl -certfile Certs.pem -out certs.pk7 -outform der

Convert PKCS7 from DER to PEM:

openssl pkcs7 -in certs.pk7 -inform DER -out certs.pem -outform PEM

Sample PKCS7 file:

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Java CertPath example: read CertPath from file