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 graphs and can be constructed from
 * their constituent Roles.
 * @author <a href="http://abac.deterlab.net">ISI ABAC team</a>
 * @version 1.3
 */
public class 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 role at the head */
    protected Role m_head
    /** The role at the tail */;
    protected Role m_tail;
    /** The certificate representing this credential */
    protected X509V2AttributeCertificate ac;
    /** The identity that issued the certificate */
    protected Identity id;

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

    /**
     * Create an empty Credential.
     */
    public Credential() {
	m_head = m_tail = null;
	ac = null;
	id = 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 Credential(Role head, Role tail) {
        m_head = head;
        m_tail = tail;
	ac = null; 
	id = 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 {
	ac = new X509V2AttributeCertificate(stream);
    }

    /**
     * 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 CertificateException if the certificate is badly formatted
     * @throws InvalidKeyException if none of the Identities can validate the
     *				    certificate
     * @throws NoSuchAlgorithmException if the credential uses an unknown
     *				    signature algorithm
     * @throws NoSuchProviderException if the provider of the signature
     *				    algorithm is unavailable
     * @throws SignatureException if the signature check fails
     */
    protected void init(Collection<Identity> ids) 
	    throws CertificateException, InvalidKeyException, 
		NoSuchAlgorithmException, NoSuchProviderException,
		SignatureException {
	for (Identity i: ids) {
	    try {
		ac.verify(i.getCertificate().getPublicKey(), "BC");
		id = i;
		break;
	    }
	    catch (InvalidKeyException e) { }
	}
	if (id == null) throw new InvalidKeyException("Unknown identity");

        load_roles();

	if (!id.getKeyID().equals(m_head.principal()))
	    throw new InvalidKeyException("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 CertificateException if the certificate is badly formatted
     * @throws InvalidKeyException if none of the Identities can validate the
     *				    certificate
     * @throws NoSuchAlgorithmException if the credential uses an unknown
     *				    signature algorithm
     * @throws NoSuchProviderException if the provider of the signature
     *				    algorithm is unavailable
     * @throws SignatureException if the signature check fails
     * @throws IOException if the certificate is unparsable.
     */
    protected void init(InputStream stream, Collection<Identity> ids) 
	    throws CertificateException, InvalidKeyException, 
		NoSuchAlgorithmException, NoSuchProviderException,
		SignatureException, IOException {
	read_certificate(stream);
	if (ac == null) throw new IOException("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 StreamParsingException if the stream is unparsable
     * @throws CertificateException if the certificate is badly formatted
     * @throws InvalidKeyException if none of the Identities can validate the
     *				    certificate
     * @throws NoSuchAlgorithmException if the credential uses an unknown
     *				    signature algorithm
     * @throws NoSuchProviderException if the provider of the signature
     *				    algorithm is unavailable
     * @throws SignatureException if the signature check fails
     * @throws IOException if the certificate is unparsable.
     */
    public Credential(String filename, Collection<Identity> ids) 
	throws Exception { init(new FileInputStream(filename), 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 file the File to read
     * @param ids a Collection of Identities to use in validating the cert
     * @throws StreamParsingException if the stream is unparsable
     * @throws CertificateException if the certificate is badly formatted
     * @throws InvalidKeyException if none of the Identities can validate the
     *				    certificate
     * @throws NoSuchAlgorithmException if the credential uses an unknown
     *				    signature algorithm
     * @throws NoSuchProviderException if the provider of the signature
     *				    algorithm is unavailable
     * @throws SignatureException if the signature check fails
     * @throws IOException if the certificate is unparsable.
     */
    public Credential(File file, Collection<Identity> ids) 
	    throws CertificateException, InvalidKeyException, 
		NoSuchAlgorithmException, NoSuchProviderException,
		SignatureException, StreamParsingException, IOException {
	init(new FileInputStream(file), ids);
    }

    /**
     * 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 StreamParsingException if the stream is unparsable
     * @throws CertificateException if the certificate is badly formatted
     * @throws InvalidKeyException if none of the Identities can validate the
     *				    certificate
     * @throws NoSuchAlgorithmException if the credential uses an unknown
     *				    signature algorithm
     * @throws NoSuchProviderException if the provider of the signature
     *				    algorithm is unavailable
     * @throws SignatureException if the signature check fails
     * @throws IOException if the certificate is unparsable.
     */
    public Credential(InputStream s, Collection<Identity> ids) 
	    throws CertificateException, InvalidKeyException, 
		NoSuchAlgorithmException, NoSuchProviderException,
		SignatureException, StreamParsingException, IOException {
	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 CertificateException if the certificate is badly formatted
     * @throws InvalidKeyException if none of the Identities can validate the
     *				    certificate
     * @throws NoSuchAlgorithmException if the credential uses an unknown
     *				    signature algorithm
     * @throws NoSuchProviderException if the provider of the signature
     *				    algorithm is unavailable
     * @throws SignatureException if the signature check fails
     * @throws IOException if the certificate is unparsable.
     */
    public Credential(X509V2AttributeCertificate c, Collection<Identity> ids) 
	    throws CertificateException, InvalidKeyException, 
		NoSuchAlgorithmException, NoSuchProviderException,
		SignatureException, IOException {
	ac = c;
	init(ids);
    }


    /**
     * Create a certificate from this credential issued by the given identity.
     * Note that catching java.security.GeneralSecurityException catches most
     * of the exceptions this throws.
     * @param i the Identity that will issue the certificate
     * @throws IOException reading or writing problems
     * @throws CertificateEncodingException Problem creating certificate
     * @throws InvalidKeyException if none of the Identities can sign the
     *				    certificate
     * @throws NoSuchAlgorithmException if the credential uses an unknown
     *				    signature algorithm
     * @throws NoSuchProviderException if the provider of the signature
     *				    algorithm is unavailable
     * @throws SignatureException if the signature creation fails
     */
    public void make_cert(Identity i) 
	    throws IOException, CertificateEncodingException,
	       NoSuchProviderException, NoSuchAlgorithmException,
	       SignatureException, InvalidKeyException {
	PrivateKey key = i.getKeyPair().getPrivate();
	SubjectPublicKeyInfo pki = Context.extractSubjectPublicKeyInfo(
		i.getKeyPair().getPublic());
	X509V2AttributeCertificateGenerator gen = 
	    new X509V2AttributeCertificateGenerator();

	gen.setIssuer(new AttributeCertificateIssuer(
		    new X500Principal("CN="+m_head.principal())));
	gen.setHolder(new AttributeCertificateHolder(
		    new X500Principal("CN="+m_head.principal())));
	gen.setNotAfter(new Date(System.currentTimeMillis() 
		    + (3600L * 1000L * 24L * 365L)));
	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));
	// Create the cert.
	ac = (X509V2AttributeCertificate) gen.generate(key, "BC");
	id = i;
    }

    /**
     * Load the roles off the attribute cert. Throws a RuntimeException if
     * there's something wrong with the cert.
     */
    private void load_roles() {
        String roles = null;
        try {
            X509Attribute attr = ac.getAttributes()[0];

            DERSequence    java     = (DERSequence)attr.getValues()[0];
            DERSequence    fucking  = (DERSequence)java.getObjectAt(0);
            DERUTF8String  sucks    = (DERUTF8String)fucking.getObjectAt(0);

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

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

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

    /**
     * Two credentials are the same if their roles are the same.
     * @param o an Object to compare
     * @return true if the Credentials have the Roles 
     */
    public boolean equals(Object o) {
	if ( o instanceof Credential ) {
	    Credential c = (Credential) o;

	    if (m_head == null || m_tail == null ) return false;
	    else return (m_head.equals(c.head()) && m_tail.equals(c.tail()));
	}
	else return false;
    }

    /**
     * Allow credentials to be compared.  They are ordered by their Roles, head
     * then tail.
     * @param o an Object to compare
     * @return -1 if this Credential is before, 0 if they are the same, and 1
     *		    if this Credential is after the given object.
     */
    public int compareTo(Object o) {
	if (o instanceof Credential) {
	    Credential c = (Credential) o;

	    if (head().equals(c.head())) return tail().compareTo(c.tail());
	    else return head().compareTo(c.head());
	}
	else return 1;
    }


    /**
     * Get the head role from the credential.
     * @return the Role in the head
     */
    public Role head() { return m_head; }

    /**
     * Get the tail role from the credential
     * @return the Role in the tail
     */
    public Role tail() { return m_tail; }

    /**
     * Gets the cert associated with this credential (if any).
     * @return the attribute cert associated with this credential (if any).
     */
    public X509V2AttributeCertificate cert() { return ac; }

    /**
     * Turn the credential into string form. The format is head &lt;- tail. For
     * example: A.r1 &lt;- B.r2.r3.  Principal names are key identifiers.
     * @return the string form
     */
    public String toString() {
        return m_head + " <- " + m_tail;
    }

    /**
     * Turn the credential into string form. The format is head &lt;- tail. For
     * example: A.r1 &lt;- B.r2.r3.  Principal names are shortened to menmonics
     * if the Context knows the identity.
     * @param c the Context to translate names in
     * @return the string form
     */
    public String simpleString(Context c) {
	return m_head.simpleString(c) + " <- " + m_tail.simpleString(c);
    }

    /**
     * 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 the Identity that issued the underlying certificate.  A jabac
     * extension.
     * @return the Identity that issued the underlying certificate.
     */
    public Identity issuer() { return id; }
    /**
     * Return the X509Certificate that issued the underlying certificate.
     * @return the X509Certificate that issued the underlying certificate.
     */
    public X509Certificate issuerCert() { return id.getCertificate(); }
    /**
     * Return the X509V2AttributeCertificate that underlys the Credential
     * @return the X509V2AttributeCertificate that underlys the Credential.
     */
    public X509V2AttributeCertificate attributeCert() { return ac; }


}