package net.deterlab.abac;

import java.io.*;
import java.math.*;

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

import javax.security.auth.x500.*;

import org.bouncycastle.asn1.*;
import org.bouncycastle.asn1.x509.*;
import org.bouncycastle.x509.*;
import org.bouncycastle.x509.util.*;
import org.bouncycastle.openssl.*;

/**
 * An ABAC credential, with or without an underlying certificate that
 * represents it.  These are edges in proof garphs and can be constructed from
 * their constituent Roles.
 * @author <a href="http://abac.deterlab.net">ISI ABAC team</a>
 * @version 1.4
 */
public class X509Credential extends Credential implements Comparable {
    /** The ASN1 OID for an IETF attribute. */
    protected static String attrOID = "1.3.6.1.5.5.7.10.4";
    /** The ASN1 OID for AuthorityKeyIdentifier. */
    protected static String authKeyOID = "2.5.29.35";
    /** The certificate representing this credential */
    protected X509V2AttributeCertificate ac;

    /** Make sure BouncyCastle is loaded */
    static { Context.loadBouncyCastle(); } 

    /**
     * Create an empty Credential.
     */
    public X509Credential() {
	super();
	ac = null;
    }
    /**
     * Create a credential from a head and tail role.  This credential has no
     * underlying certificate, and cannot be exported or used in real proofs.
     * make_cert can create a certificate for a credential initialized this
     * way.
     * @param head the Role at the head of the credential
     * @param tail the Role at the tail of the credential
     */
    public X509Credential(Role head, Role tail) {
	super(head, tail);
	ac = null; 
    }

    /**
     * Do the credential extraction from an input stream.  This parses the
     * certificate from the input stream and saves it. The contents must be
     * validated and parsed later.
     * @param stream the InputStream to read the certificate from.
     * @throws IOException if the stream is unparsable
     */
    protected void read_certificate(InputStream stream) 
	    throws IOException {
	try { 
	    ac = new X509V2AttributeCertificate(stream);
	}
	catch (Exception e) {
	    throw new IOException(e.getMessage(), e);
	}
    }

    /**
     * Initialize a credential from parsed certificate.  Validiate it against
     * the given identities and parse out the roles.  Note that catching
     * java.security.GeneralSecurityException catches most of the exceptions
     * this throws.
     * @param ids a Collection of Identities to use in validating the cert
     * @throws CertInvalidException if the stream is unparsable
     * @throws MissingIssuerException if none of the Identities can validate the
     *				    certificate
     * @throws BadSignatureException if the signature check fails
     */
    protected void init(Collection<Identity> ids) 
	    throws ABACException {
	for (Identity i: ids) {
	    try {
		ac.verify(i.getCertificate().getPublicKey(), "BC");
		id = i;
		break;
	    }
	    catch (GeneralSecurityException e) { }
	}
	if (id == null) throw new MissingIssuerException("Unknown identity");

	m_expiration = ac.getNotAfter();
        load_roles();

	if (!id.getKeyID().equals(m_head.principal()))
	    throw new MissingIssuerException("Unknown identity");
    }

    /**
     * Parse a credential from an InputStream and initialize the role from it.
     * Combine read_credential(stream) and init(ids).  Note that catching
     * java.security.GeneralSecurityException catches most of the exceptions
     * this throws.
     * @param stream the InputStream to read the certificate from.
     * @param ids a Collection of Identities to use in validating the cert
     * @throws CertInvalidException if the stream is unparsable
     * @throws MissingIssuerException if none of the Identities can validate the
     *				    certificate
     * @throws BadSignatureException if the signature check fails
     */
    protected void init(InputStream stream, Collection<Identity> ids) 
	    throws ABACException {
	try {
	    read_certificate(stream);
	}
	catch (IOException e) {
	    throw new CertInvalidException(e.getMessage(), e);
	}
	if (ac == null) throw new CertInvalidException("Unknown Format");
	init(ids);
    }

    /**
     * Create a credential from an attribute cert in a file. Throws an
     * exception if the cert file can't be opened or if there's a format
     * problem with the cert.  Note that catching
     * java.security.GeneralSecurityException catches most of the exceptions
     * this throws.
     * @param filename a String containing the filename to read
     * @param ids a Collection of Identities to use in validating the cert
     * @throws CertInvalidException if the stream is unparsable
     * @throws MissingIssuerException if none of the Identities can validate the
     *				    certificate
     * @throws BadSignatureException if the signature check fails
     */
    X509Credential(String filename, Collection<Identity> ids) 
	throws ABACException { 
	try {
	    init(new FileInputStream(filename), ids); 
	}
	catch (FileNotFoundException e) {
	    throw new CertInvalidException("Bad filename", e);
	}
    }

    /**
     * Create a credential from an attribute cert in a file. Throws an
     * exception if the cert file can't be opened or if there's a format
     * problem with the cert.  Note that catching
     * java.security.GeneralSecurityException catches most of the exceptions
     * this throws.
     * @param file the File to read
     * @param ids a Collection of Identities to use in validating the cert
     * @throws CertInvalidException if the stream is unparsable
     * @throws MissingIssuerException if none of the Identities can validate the
     *				    certificate
     * @throws BadSignatureException if the signature check fails
     */
    X509Credential(File file, Collection<Identity> ids) 
	    throws ABACException {
	try {
	    init(new FileInputStream(file), ids);
	}
	catch (FileNotFoundException e) {
	    throw new CertInvalidException("Bad filename", e);
	}
    }

    /**
     * Create a credential from an InputStream.  Throws an exception if the
     * stream can't be parsed or if there's a format problem with the cert.
     * Note that catching java.security.GeneralSecurityException catches most
     * of the exceptions this throws.
     * @param s the InputStream to read
     * @param ids a Collection of Identities to use in validating the cert
     * @throws CertInvalidException if the stream is unparsable
     * @throws MissingIssuerException if none of the Identities can validate the
     *				    certificate
     * @throws BadSignatureException if the signature check fails
     */
    X509Credential(InputStream s, Collection<Identity> ids) 
	    throws ABACException { init(s, ids); }

    /**
     * Create a credential from an X509V2AttributeCertificate object.  Throws
     * an exception if the certificate doesn't parse into an ABAC credential,
     * or cannot be validated.  Note that catching
     * java.security.GeneralSecurityException catches most of the exceptions
     * this throws.
     * @param c the X509V2AttributeCertificate to create from
     * @param ids a Collection of Identities to use in validating the cert
     * @throws CertInvalidException if the stream is unparsable
     * @throws MissingIssuerException if none of the Identities can validate the
     *				    certificate
     * @throws BadSignatureException if the signature check fails
     */
    X509Credential(X509V2AttributeCertificate c, 
	    Collection<Identity> ids) 
	    throws ABACException {
	ac = c;
	init(ids);
    }


    /**
     * Create a certificate from this credential issued by the given identity
     * valid for the given time.
     * @param i the Identity that will issue the certificate
     * @param validity a long holding the number of seconds that the credential
     * is valid for.
     * @throws ABACException if xml creation fails
     * @throws MissingIssuerException if the issuer is bad
     * @throws BadSignatureException if the signature creation fails
     */
    public void make_cert(Identity i, long validity) 
	    throws ABACException {
	PrivateKey key = i.getKeyPair().getPrivate();
	SubjectPublicKeyInfo pki = Context.extractSubjectPublicKeyInfo(
		i.getKeyPair().getPublic());
	X509V2AttributeCertificateGenerator gen = 
	    new X509V2AttributeCertificateGenerator();

	try {
	    gen.setIssuer(new AttributeCertificateIssuer(
			new X500Principal("CN="+m_head.principal())));
	    gen.setHolder(new AttributeCertificateHolder(
			new X500Principal("CN="+m_head.principal())));
	    m_expiration = new Date(System.currentTimeMillis() 
		    + (1000L * validity));
	    gen.setNotAfter(m_expiration);
	    gen.setNotBefore(new Date(System.currentTimeMillis()));
	    gen.setSerialNumber(BigInteger.valueOf(System.currentTimeMillis()));
	    gen.addAttribute(new X509Attribute(attrOID, 
			new DERSequence(
			    new DERSequence(
				new DERUTF8String(toString())))));
	    gen.setSignatureAlgorithm("SHA256WithRSAEncryption");

	    // Creddy expects an authority key identifier.
	    gen.addExtension(authKeyOID, false, 
		    new AuthorityKeyIdentifier(pki));
	    ac = (X509V2AttributeCertificate) gen.generate(key, "BC");
	}
	catch (Exception e) {
	    throw new ABACException("Cannot encode cert", e);
	}
	// Create the cert.
	id = i;
    }

    /**
     * Create a certificate from this credential issued by the given identity
     * valid for the default validity.
     * @param i the Identity that will issue the certificate
     * @throws ABACException if xml creation fails
     * @throws MissingIssuerException if the issuer is bad
     * @throws BadSignatureException if the signature creation fails
     */
    public void make_cert(Identity i) throws ABACException {
	make_cert(i, defaultValidity);
    }

    /**
     * Load the roles off the attribute cert. 
     * @throws CertInvalidException if the certificate is badly formatted
     */
    private void load_roles() throws CertInvalidException {
        String roles = null;
        try {
            X509Attribute attr = ac.getAttributes()[0];

            DERSequence    t1     = (DERSequence)attr.getValues()[0];
            DERSequence    t2  = (DERSequence)t1.getObjectAt(0);
            DERUTF8String  t3    = (DERUTF8String)t2.getObjectAt(0);

            roles = t3.getString();
        }
        catch (Exception e) {
            throw new CertInvalidException("Badly formatted certificate");
        }

        String[] parts = roles.split("\\s*<--?\\s*");
        if (parts.length != 2)
            throw new CertInvalidException("Invalid attribute: " + roles);

        m_head = new Role(parts[0]);
        m_tail = new Role(parts[1]);
    }

    /**
     * Output the DER formatted attribute certificate associated with this
     * Credential to the OutputStream.
     * @param s the OutputStream on which to write
     * @throws IOException if there is an error writing.
     */
    public void write(OutputStream s) throws IOException {
	if (ac != null ) 
	    s.write(ac.getEncoded());
	s.flush();
    }

    /**
     * Output the DER formatted attribute certificate associated with this
     * Credential to the filename given.
     * @param fn a String containing the output filename
     * @throws IOException if there is an error writing.
     */
    public void write(String fn) throws IOException, FileNotFoundException {
	write(new FileOutputStream(fn));
    }

    /**
     * Return true if this Credential has a certificate associated.  A jabac
     * extension.
     * @return true if this Credential has a certificate associated.
     */
    public boolean hasCertificate() { return ac != null; }

    /**
     * Return a CredentialFactorySpecialization for X509Credentials.  Used by
     * the CredentialFactory to parse and generate these kind of credentials.
     * It is basically a wrapper around constuctor calls.
     * @return a CredentialParser for this kind of credential.
     */
    static public CredentialFactorySpecialization 
	    getCredentialFactorySpecialization() {
	return new CredentialFactorySpecialization() {
	    public Credential[] parseCredential(InputStream is, 
		    Collection<Identity> ids) throws ABACException {
		return new Credential[] { new X509Credential(is, ids) }; 
	    }
	    public Credential generateCredential(Role head, Role tail) {
		return new X509Credential(head, tail);
	    }
	};
    }


}