package gnu.crypto.sig.rsa;
// ----------------------------------------------------------------------------
// $Id: RSAPSSSignature.java,v 1.8 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module. An independent module is a module which is
// not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so. If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
import gnu.crypto.Registry;
import gnu.crypto.hash.HashFactory;
import gnu.crypto.hash.IMessageDigest;
import gnu.crypto.sig.BaseSignature;
import gnu.crypto.util.Util;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
/**
* <p>The RSA-PSS signature scheme is a public-key encryption scheme combining
* the RSA algorithm with the Probabilistic Signature Scheme (PSS) encoding
* method.</p>
*
* <p>The inventors of RSA are Ronald L. Rivest, Adi Shamir, and Leonard Adleman,
* while the inventors of the PSS encoding method are Mihir Bellare and Phillip
* Rogaway. During efforts to adopt RSA-PSS into the P1363a standards effort,
* certain adaptations to the original version of RSA-PSS were made by Mihir
* Bellare and Phillip Rogaway and also by Burt Kaliski (the editor of IEEE
* P1363a) to facilitate implementation and integration into existing protocols.</p>
*
* <p>References:</pr>
* <ol>
* <li><a href="http://www.cosic.esat.kuleuven.ac.be/nessie/workshop/submissions/rsa-pss.zip">
* RSA-PSS Signature Scheme with Appendix, part B.</a><br>
* Primitive specification and supporting documentation.<br>
* Jakob Jonsson and Burt Kaliski.</li>
* </ol>
*
* @version $Revision: 1.8 $
*/
public class RSAPSSSignature extends BaseSignature {
// Debugging methods and variables
// -------------------------------------------------------------------------
private static final String NAME = "rsa-pss";
private static final boolean DEBUG = false;
private static final int debuglevel = 1;
private static final PrintWriter err = new PrintWriter(System.out, true);
private static void debug(String s) {
err.println(">>> "+NAME+": "+s);
}
// Constants and variables
// -------------------------------------------------------------------------
/** The underlying EMSA-PSS instance for this object. */
private EMSA_PSS pss;
/** The desired length in octets of the EMSA-PSS salt. */
private int sLen;
// Constructor(s)
// -------------------------------------------------------------------------
/**
* Default 0-arguments constructor. Uses SHA-1 as the default hash and a
* 0-octet <i>salt</i>.
*/
public RSAPSSSignature() {
this(Registry.SHA160_HASH, 0);
}
/**
* <p>Constructs an instance of this object using the designated message
* digest algorithm as its underlying hash function, and having 0-octet
* <i>salt</i>.</p>
*
* @param mdName the canonical name of the underlying hash function.
*/
public RSAPSSSignature(String mdName) {
this(mdName, 0);
}
/**
* <p>Constructs an instance of this object using the designated message
* digest algorithm as its underlying hash function.</p>
*
* @param mdName the canonical name of the underlying hash function.
* @param sLen the desired length in octets of the salt to use for encoding /
* decoding signatures.
*/
public RSAPSSSignature(String mdName, int sLen) {
super(Registry.RSA_PSS_SIG, HashFactory.getInstance(mdName));
pss = EMSA_PSS.getInstance(mdName);
this.sLen = sLen;
}
/** Private constructor for cloning purposes. */
private RSAPSSSignature(RSAPSSSignature that) {
this(that.md.name(), that.sLen);
this.publicKey = that.publicKey;
this.privateKey = that.privateKey;
this.md = (IMessageDigest) that.md.clone();
this.pss = (EMSA_PSS) that.pss.clone();
}
// Class methods
// -------------------------------------------------------------------------
// Instance methods
// -------------------------------------------------------------------------
// Implementation of abstract methods in superclass ------------------------
public Object clone() {
return new RSAPSSSignature(this);
}
protected void setupForVerification(PublicKey k)
throws IllegalArgumentException {
if (!(k instanceof RSAPublicKey)) {
throw new IllegalArgumentException();
}
publicKey = (RSAPublicKey) k;
}
protected void setupForSigning(PrivateKey k)
throws IllegalArgumentException {
if (!(k instanceof RSAPrivateKey)) {
throw new IllegalArgumentException();
}
privateKey = (RSAPrivateKey) k;
}
protected Object generateSignature() throws IllegalStateException {
// 1. Apply the EMSA-PSS encoding operation to the message M to produce an
// encoded message EM of length CEILING((modBits ? 1)/8) octets such
// that the bit length of the integer OS2IP(EM) is at most modBits ? 1:
// EM = EMSA-PSS-Encode(M,modBits ? 1).
// Note that the octet length of EM will be one less than k if
// modBits ? 1 is divisible by 8. If the encoding operation outputs
// 'message too long' or 'encoding error,' then output 'message too
// long' or 'encoding error' and stop.
int modBits = ((RSAPrivateKey) privateKey).getModulus().bitLength();
byte[] salt = new byte[sLen];
this.nextRandomBytes(salt);
byte[] EM = pss.encode(md.digest(), modBits - 1, salt);
if (DEBUG && debuglevel > 8) {
debug("EM (sign): "+Util.toString(EM));
}
// 2. Convert the encoded message EM to an integer message representative
// m (see Section 1.2.2): m = OS2IP(EM).
BigInteger m = new BigInteger(1, EM);
// 3. Apply the RSASP signature primitive to the public key K and the
// message representative m to produce an integer signature
// representative s: s = RSASP(K,m).
BigInteger s = RSA.sign(privateKey, m);
// 4. Convert the signature representative s to a signature S of length k
// octets (see Section 1.2.1): S = I2OSP(s, k).
// 5. Output the signature S.
int k = (modBits + 7) / 8;
// return encodeSignature(s, k);
return RSA.I2OSP(s, k);
}
protected boolean verifySignature(Object sig) throws IllegalStateException {
if (publicKey == null) {
throw new IllegalStateException();
}
// byte[] S = decodeSignature(sig);
byte[] S = (byte[]) sig;
// 1. If the length of the signature S is not k octets, output 'signature
// invalid' and stop.
int modBits = ((RSAPublicKey) publicKey).getModulus().bitLength();
int k = (modBits + 7) / 8;
if (S.length != k) {
return false;
}
// 2. Convert the signature S to an integer signature representative s:
// s = OS2IP(S).
BigInteger s = new BigInteger(1, S);
// 3. Apply the RSAVP verification primitive to the public key (n, e) and
// the signature representative s to produce an integer message
// representative m: m = RSAVP((n, e), s).
// If RSAVP outputs 'signature representative out of range,' then
// output 'signature invalid' and stop.
BigInteger m = null;
try {
m = RSA.verify(publicKey, s);
} catch (IllegalArgumentException x) {
return false;
}
// 4. Convert the message representative m to an encoded message EM of
// length emLen = CEILING((modBits - 1)/8) octets, where modBits is
// equal to the bit length of the modulus: EM = I2OSP(m, emLen).
// Note that emLen will be one less than k if modBits - 1 is divisible
// by 8. If I2OSP outputs 'integer too large,' then output 'signature
// invalid' and stop.
int emBits = modBits - 1;
int emLen = (emBits + 7) / 8;
byte[] EM = m.toByteArray();
if (DEBUG && debuglevel > 8) {
debug("EM (verify): "+Util.toString(EM));
}
if (EM.length > emLen) {
return false;
} else if (EM.length < emLen) {
byte[] newEM = new byte[emLen];
System.arraycopy(EM, 0, newEM, emLen - EM.length, EM.length);
EM = newEM;
}
// 5. Apply the EMSA-PSS decoding operation to the message M and the
// encoded message EM: Result = EMSA-PSS-Decode(M, EM, emBits). If
// Result = 'consistent,' output 'signature verified.' Otherwise,
// output 'signature invalid.'
byte[] mHash = md.digest();
boolean result = false;
try {
result = pss.decode(mHash, EM, emBits, sLen);
} catch (IllegalArgumentException x) {
result = false;
}
return result;
}
// Other instance methods --------------------------------------------------
/**
* Converts the <i>signature representative</i> <code>s</code> to a signature
* <code>S</code> of length <code>k</code> octets; i.e.
* <code>S = I2OSP(s, k)</code>, where <code>k = CEILING(modBits/8)</code>.
*
* @param s the <i>signature representative</i>.
* @param k the length of the output.
* @return the signature as an octet sequence.
* @exception IllegalArgumentException if the length in octets of meaningful
* bytes of <code>s</code> is greater than <code>k</code>, implying that
* <code>s</code> is not less than the RSA <i>modulus</i>.
*/
// private Object encodeSignature(BigInteger s, int k) {
// if (DEBUG && debuglevel > 8) {
// debug("s.bitLength(): "+String.valueOf(s.bitLength()));
// debug("k: "+String.valueOf(k));
// }
// byte[] result = s.toByteArray();
// if (DEBUG && debuglevel > 8) {
// debug("s: "+Util.toString(result));
// debug("s (bytes): "+String.valueOf(result.length));
// }
// if (result.length < k) {
// byte[] newResult = new byte[k];
// System.arraycopy(result, 0, newResult, k-result.length, result.length);
// result = newResult;
// } else if (result.length > k) { // leftmost extra bytes should all be 0
// int limit = result.length - k;
// for (int i = 0; i < limit; i++) {
// if (result[i] != 0x00) {
// throw new IllegalArgumentException("integer too large");
// }
// }
// byte[] newResult = new byte[k];
// System.arraycopy(result, limit, newResult, 0, k);
// result = newResult;
// }
// return result;
// }
/**
* Returns the output of a previously generated signature object as an octet
* sequence.<p>
*
* @return the octet sequence <code>S</code>.
*/
// private byte[] decodeSignature(Object signature) {
// return (byte[]) signature;
// }
}