package net.deterlab.abac;

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

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

import javax.security.auth.x500.*;

import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;

import javax.xml.crypto.*;
import javax.xml.crypto.dsig.*;
import javax.xml.crypto.dsig.dom.*;
import javax.xml.crypto.dsig.keyinfo.*;
import javax.xml.crypto.dsig.spec.*;

import org.xml.sax.*;
import org.w3c.dom.*;

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 formatted as an abac-type GENI credential.
 * @author <a href="http://abac.deterlab.net">ISI ABAC team</a>
 * @version 1.4
 */
public class GENIPrivCredential extends GENICredential {
    /**
     * Create an empty Credential.
     */
    public GENIPrivCredential() {
	super();
	doc = 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 GENIPrivCredential(Role head, Role tail, Document d, Identity i,
	    Date e) {
        m_head = head;
        m_tail = tail;
	doc = null; 
	id = null;
	m_expiration = e;
    }
    /**
     * Create a certificate from this credential issued by the given identity
     * valid for the given period; these credentials cannot be turned into
     * certificates, so this will always throw an exception.
     * @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 {
	throw new ABACException("Cannot generate a GENIPrivCredential");
    }


    /**
     * Create a certificate from this credential issued by the given identity;
     * these credentials cannot be turned into certificates, so this will
     * always throw an exception.
     * @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 {
	throw new ABACException("Cannot generate a GENIPrivCredential");
    }

    /**
     * Class that parses a GENI privilege credential into multiple
     * GENIPrivCredential objects.
     */
    static class GENIPrivSpecialization 
	    extends CredentialFactorySpecialization {

	/**
	 * Extract an identity from a field holding a PEM-encoded x.509
	 * certificate (for example, owner_gid).
	 * @param n a Node that has the certificate in its Text Content
	 * @return the Identity
	 */
	protected Identity nodeToIdentity(Node n) {
	    String certStr = null;

	    if ( ( certStr = n.getTextContent()) == null ) return null;
	    try {
		certStr = "-----BEGIN CERTIFICATE-----\n" + 
		    certStr + 
		"\n-----END CERTIFICATE-----";
		return new Identity(new StringReader(certStr));
	    } 
	    catch (Exception e) {
		return null;
	    }
	}

	/**
	 * Parses the credential into multiple Objects based on the permissions
	 * imbued by the credential.
	 * @param d a Document, the parsed credential
	 * @param issuer an Identity that signed the credential
	 * @return an array of GENIPrivCredentials that represent the
	 * credential
	 */
	protected Credential[] make_creds(Document d, Identity issuer) 
		throws ABACException {
	    Node root = null;
	    Node credential = null;
	    Node owner_gid = null;
	    Node target_gid = null;
	    Node privileges = null;
	    Node priv = null;
	    Identity owner = null;
	    Identity target = null;
	    ArrayList<GENIPrivCredential> rv = 
		new ArrayList<GENIPrivCredential>();


	    if ( (root = getChildByName(d, "signed-credential")) == null)
		throw new CertInvalidException("No signed-credential element");
	    if ( (credential = getChildByName(root, "credential")) == null )
		throw new CertInvalidException("No credential element");
	    if ( (owner_gid = getChildByName(credential, "owner_gid")) == null )
		throw new CertInvalidException("No owner_gid element");
	    if ((target_gid = getChildByName(credential,"target_gid")) == null )
		throw new CertInvalidException("No target_gid element");
	    if ((privileges = getChildByName(credential,"privileges")) == null )
		throw new CertInvalidException("No privileges element");

	    Date exp = getTime(d, "expires");

	    if ( exp.before(new Date()))
		throw new CertInvalidException("Certificate Expired " + exp);

	    if ( (owner = nodeToIdentity(owner_gid)) == null) 
		throw new CertInvalidException("Bad owner_gid element");
	    if ( (target = nodeToIdentity(target_gid)) == null) 
		throw new CertInvalidException("Bad target_gid element");

	    for (Node n = privileges.getFirstChild(); n != null; 
		    n = n.getNextSibling()) {
		/* Ignore non-elements and non-privilege elements */
		if (n.getNodeType() != Node.ELEMENT_NODE ||
			!"privilege".equals(n.getNodeName())) continue;
		Node name = null;
		Node can_delegate = null;
		boolean cd = false;
		String cds = null;
		String pname = null;

		if ( (name = getChildByName(n, "name")) == null)
		    throw new CertInvalidException("No privilege name");

		if ((can_delegate = getChildByName(n, "can_delegate")) == null)
		    throw new CertInvalidException("No privilege delegate");

		if ( (pname = name.getTextContent()) == null)
		    throw new CertInvalidException("No privilege name text");
		if ((cds = can_delegate.getTextContent()) == null)
		    throw new CertInvalidException("No delegate text");
		cd = cds.equals("1") || cds.equals("true");

		/* First privilege includes the basic speaks for defintion 
		 * for this owner */
		if ( rv.isEmpty() ) {
		    rv.add(new GENIPrivCredential(
				new Role(issuer.getKeyID() + ".speaks_for_" +
				    owner.getKeyID()),
				new Role(owner.getKeyID()), d, issuer, exp));
		    rv.add(new GENIPrivCredential(
				new Role(issuer.getKeyID() + ".speaks_for_" +
				    owner.getKeyID()),
				new Role(owner.getKeyID() + ".speaks_for_" +
				    owner.getKeyID()), d, issuer, exp));
		}

		/* The privilege itself */
		rv.add(new GENIPrivCredential(
			    new Role(issuer.getKeyID() + "." + pname + "_" +
				target.getKeyID()),
			    new Role(issuer.getKeyID() + ".speaks_for_" +
				owner.getKeyID()), d, issuer, exp));
		if (cd ) {
		    /* The rules for delegation, if necessary */
		    rv.add(new GENIPrivCredential(
				new Role(issuer.getKeyID() + "." + pname + 
				    "_" + target.getKeyID()),
				new Role(issuer.getKeyID() + ".can_delegate_" 
				    + pname + "_" + target.getKeyID() + 
				    "." + pname + "_" + target.getKeyID()), 
				d, issuer, exp));
		    rv.add(new GENIPrivCredential(
				new Role(issuer.getKeyID() + 
				    ".can_delegate_" + pname),
				new Role(owner.getKeyID()), d, issuer, exp));
		}
	    }
	    return rv.toArray(new Credential[rv.size()]);
	}

	/**
	 * Parse the credential into multiple GENIPrivCredentials that encode
	 * its semantics.
	 * @param is an InputStream containing the credentals
	 * @param ids a Collection of Identities to use in validation
	 * @return an array of GENIPrivCredentials that represent the
	 * credential
	 * @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
	 */
	public Credential[] parseCredential(InputStream is, 
		Collection<Identity> ids) throws ABACException {
	    try {
		Document d = read_certificate(is);
		XMLSignatureFactory fac = 
		    XMLSignatureFactory.getInstance("DOM");
		NodeList nl = d.getElementsByTagNameNS(XMLSignature.XMLNS, 
			"Signature");
		DOMValidateContext valContext = null;
		XMLSignature signature = null;
		Identity lid = null;


		if (nl.getLength() == 0) 
		    throw new CertInvalidException(
			    "Cannot find Signature element");

		setIDAttrs(d);
		valContext = new DOMValidateContext(new X509KeySelector(),
			nl.item(0));
		if ( valContext == null )
		    throw new ABACException("No validation context!?");

		signature = fac.unmarshalXMLSignature(valContext);
		if (signature == null) 
		    throw new BadSignatureException(
			    "Cannot unmarshal signature");

		if (!signature.validate(valContext))
		    throw new BadSignatureException("bad signature");

		lid = getIdentity(nl.item(0));

		if ( !ids.contains(lid) ) ids.add(lid);

		return make_creds(d, lid);
	    }
	    catch (ABACException ae) {
		throw ae;
	    }
	    catch (Exception e) {
		throw new BadSignatureException(e.getMessage(), e);
	    }
	}

	/**
	 * One cannot create a GENIPrivCredential to encodes a single arbitrary
	 * head and tail, so this always fails.
	 * @param head a Role to encode
	 * @param tail a Role to encode
	 */
	public Credential generateCredential(Role head, Role tail) {
	    return null;
	}
    };

    /**
     * Return a CredentialCredentialFactorySpecialization for
     * GENIPrivCredentials.  Used by the CredentialFactory to parse these kind
     * of credentials. 
     * @return a CredentialFactorySpecialization for this kind of credential.
     */
    static public CredentialFactorySpecialization 
	    getCredentialFactorySpecialization() {
	return new GENIPrivSpecialization();
    }
}