mirror of git://gcc.gnu.org/git/gcc.git
373 lines
14 KiB
Java
373 lines
14 KiB
Java
/* EMSA_PSS.java --
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Copyright (C) 2001, 2002, 2003, 2006, 2010 Free Software Foundation, Inc.
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This file is a part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at
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your option) any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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USA
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.java.security.sig.rsa;
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import gnu.java.security.Configuration;
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import gnu.java.security.hash.HashFactory;
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import gnu.java.security.hash.IMessageDigest;
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import gnu.java.security.util.Util;
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import java.util.Arrays;
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import java.util.logging.Logger;
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/**
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* An implementation of the EMSA-PSS encoding/decoding scheme.
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* <p>
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* EMSA-PSS coincides with EMSA4 in IEEE P1363a D5 except that EMSA-PSS acts on
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* octet strings and not on bit strings. In particular, the bit lengths of the
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* hash and the salt must be multiples of 8 in EMSA-PSS. Moreover, EMSA4 outputs
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* an integer of a desired bit length rather than an octet string.
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* <p>
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* EMSA-PSS is parameterized by the choice of hash function Hash and mask
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* generation function MGF. In this submission, MGF is based on a Hash
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* definition that coincides with the corresponding definitions in IEEE Std
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* 1363-2000, PKCS #1 v2.0, and the draft ANSI X9.44. In PKCS #1 v2.0 and the
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* draft ANSI X9.44, the recommended hash function is SHA-1, while IEEE Std
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* 1363-2000 recommends SHA-1 and RIPEMD-160.
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* <p>
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* References:
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* <ol>
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* <li><a
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* href="http://www.cosic.esat.kuleuven.ac.be/nessie/workshop/submissions/rsa-pss.zip">
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* RSA-PSS Signature Scheme with Appendix, part B.</a><br>
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* Primitive specification and supporting documentation.<br>
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* Jakob Jonsson and Burt Kaliski.</li>
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* </ol>
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*/
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public class EMSA_PSS
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implements Cloneable
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{
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private static final Logger log = Configuration.DEBUG ?
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Logger.getLogger(EMSA_PSS.class.getName()) : null;
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/** The underlying hash function to use with this instance. */
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private IMessageDigest hash;
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/** The output size of the hash function in octets. */
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private int hLen;
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/**
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* Trivial private constructor to enforce use through Factory method.
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*
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* @param hash the message digest instance to use with this scheme instance.
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*/
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private EMSA_PSS(IMessageDigest hash)
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{
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super();
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this.hash = hash;
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hLen = hash.hashSize();
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}
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/**
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* Returns an instance of this object given a designated name of a hash
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* function.
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*
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* @param mdName the canonical name of a hash function.
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* @return an instance of this object configured for use with the designated
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* options.
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*/
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public static EMSA_PSS getInstance(String mdName)
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{
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IMessageDigest hash = HashFactory.getInstance(mdName);
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return new EMSA_PSS(hash);
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}
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public Object clone()
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{
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return getInstance(hash.name());
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}
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/**
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* The encoding operation EMSA-PSS-Encode computes the hash of a message
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* <code>M</code> using a hash function and maps the result to an encoded
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* message <code>EM</code> of a specified length using a mask generation
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* function.
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*
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* @param mHash the byte sequence resulting from applying the message digest
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* algorithm Hash to the message <i>M</i>.
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* @param emBits the maximal bit length of the integer OS2IP(EM), at least
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* <code>8.hLen + 8.sLen + 9</code>.
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* @param salt the salt to use when encoding the output.
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* @return the encoded message <code>EM</code>, an octet string of length
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* <code>emLen = CEILING(emBits / 8)</code>.
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* @exception IllegalArgumentException if an exception occurs.
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*/
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public byte[] encode(byte[] mHash, int emBits, byte[] salt)
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{
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int sLen = salt.length;
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// 1. If the length of M is greater than the input limitation for the hash
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// function (2**61 - 1 octets for SHA-1) then output "message too long"
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// and stop.
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// 2. Let mHash = Hash(M), an octet string of length hLen.
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if (hLen != mHash.length)
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throw new IllegalArgumentException("wrong hash");
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// 3. If emBits < 8.hLen + 8.sLen + 9, output 'encoding error' and stop.
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if (emBits < (8 * hLen + 8 * sLen + 9))
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throw new IllegalArgumentException("encoding error");
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int emLen = (emBits + 7) / 8;
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// 4. Generate a random octet string salt of length sLen; if sLen = 0,
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// then salt is the empty string.
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// ...passed as argument to accomodate JCE
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// 5. Let M0 = 00 00 00 00 00 00 00 00 || mHash || salt;
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// M0 is an octet string of length 8 + hLen + sLen with eight initial zero
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// octets.
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// 6. Let H = Hash(M0), an octet string of length hLen.
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byte[] H;
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int i;
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synchronized (hash)
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{
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for (i = 0; i < 8; i++)
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hash.update((byte) 0x00);
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hash.update(mHash, 0, hLen);
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hash.update(salt, 0, sLen);
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H = hash.digest();
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}
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// 7. Generate an octet string PS consisting of emLen - sLen - hLen - 2
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// zero octets. The length of PS may be 0.
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// 8. Let DB = PS || 01 || salt.
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byte[] DB = new byte[emLen - sLen - hLen - 2 + 1 + sLen];
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DB[emLen - sLen - hLen - 2] = 0x01;
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System.arraycopy(salt, 0, DB, emLen - sLen - hLen - 1, sLen);
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// 9. Let dbMask = MGF(H, emLen - hLen - 1).
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byte[] dbMask = MGF(H, emLen - hLen - 1);
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if (Configuration.DEBUG)
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{
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log.fine("dbMask (encode): " + Util.toString(dbMask));
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log.fine("DB (encode): " + Util.toString(DB));
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}
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// 10. Let maskedDB = DB XOR dbMask.
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for (i = 0; i < DB.length; i++)
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DB[i] = (byte)(DB[i] ^ dbMask[i]);
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// 11. Set the leftmost 8emLen - emBits bits of the leftmost octet in
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// maskedDB to zero.
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DB[0] &= (0xFF >>> (8 * emLen - emBits));
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// 12. Let EM = maskedDB || H || bc, where bc is the single octet with
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// hexadecimal value 0xBC.
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byte[] result = new byte[emLen];
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System.arraycopy(DB, 0, result, 0, emLen - hLen - 1);
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System.arraycopy(H, 0, result, emLen - hLen - 1, hLen);
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result[emLen - 1] = (byte) 0xBC;
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// 13. Output EM.
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return result;
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}
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/**
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* The decoding operation EMSA-PSS-Decode recovers the message hash from an
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* encoded message <code>EM</code> and compares it to the hash of
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* <code>M</code>.
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*
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* @param mHash the byte sequence resulting from applying the message digest
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* algorithm Hash to the message <i>M</i>.
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* @param EM the <i>encoded message</i>, an octet string of length
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* <code>emLen = CEILING(emBits/8).
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* @param emBits the maximal bit length of the integer OS2IP(EM), at least
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* <code>8.hLen + 8.sLen + 9</code>.
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* @param sLen the length, in octets, of the expected salt.
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* @return <code>true</code> if the result of the verification was
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* <i>consistent</i> with the expected reseult; and <code>false</code> if the
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* result was <i>inconsistent</i>.
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* @exception IllegalArgumentException if an exception occurs.
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*/
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public boolean decode(byte[] mHash, byte[] EM, int emBits, int sLen)
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{
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if (Configuration.DEBUG)
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{
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log.fine("mHash: " + Util.toString(mHash));
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log.fine("EM: " + Util.toString(EM));
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log.fine("emBits: " + String.valueOf(emBits));
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log.fine("sLen: " + String.valueOf(sLen));
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}
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if (sLen < 0)
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throw new IllegalArgumentException("sLen");
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// 1. If the length of M is greater than the input limitation for the hash
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// function (2**61 ? 1 octets for SHA-1) then output 'inconsistent' and
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// stop.
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// 2. Let mHash = Hash(M), an octet string of length hLen.
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if (hLen != mHash.length)
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{
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if (Configuration.DEBUG)
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log.fine("hLen != mHash.length; hLen: " + String.valueOf(hLen));
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throw new IllegalArgumentException("wrong hash");
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}
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// 3. If emBits < 8.hLen + 8.sLen + 9, output 'decoding error' and stop.
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if (emBits < (8 * hLen + 8 * sLen + 9))
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{
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if (Configuration.DEBUG)
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log.fine("emBits < (8hLen + 8sLen + 9); sLen: "
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+ String.valueOf(sLen));
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throw new IllegalArgumentException("decoding error");
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}
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int emLen = (emBits + 7) / 8;
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// 4. If the rightmost octet of EM does not have hexadecimal value bc,
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// output 'inconsistent' and stop.
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if ((EM[EM.length - 1] & 0xFF) != 0xBC)
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{
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if (Configuration.DEBUG)
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log.fine("EM does not end with 0xBC");
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return false;
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}
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// 5. Let maskedDB be the leftmost emLen ? hLen ? 1 octets of EM, and let
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// H be the next hLen octets.
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// 6. If the leftmost 8.emLen ? emBits bits of the leftmost octet in
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// maskedDB are not all equal to zero, output 'inconsistent' and stop.
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if ((EM[0] & (0xFF << (8 - (8 * emLen - emBits)))) != 0)
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{
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if (Configuration.DEBUG)
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log.fine("Leftmost 8emLen - emBits bits of EM are not 0s");
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return false;
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}
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byte[] DB = new byte[emLen - hLen - 1];
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byte[] H = new byte[hLen];
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System.arraycopy(EM, 0, DB, 0, emLen - hLen - 1);
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System.arraycopy(EM, emLen - hLen - 1, H, 0, hLen);
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// 7. Let dbMask = MGF(H, emLen ? hLen ? 1).
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byte[] dbMask = MGF(H, emLen - hLen - 1);
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// 8. Let DB = maskedDB XOR dbMask.
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int i;
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for (i = 0; i < DB.length; i++)
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DB[i] = (byte)(DB[i] ^ dbMask[i]);
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// 9. Set the leftmost 8.emLen ? emBits bits of DB to zero.
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DB[0] &= (0xFF >>> (8 * emLen - emBits));
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if (Configuration.DEBUG)
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{
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log.fine("dbMask (decode): " + Util.toString(dbMask));
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log.fine("DB (decode): " + Util.toString(DB));
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}
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// 10. If the emLen -hLen -sLen -2 leftmost octets of DB are not zero or
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// if the octet at position emLen -hLen -sLen -1 is not equal to 0x01,
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// output 'inconsistent' and stop.
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// IMPORTANT (rsn): this is an error in the specs, the index of the 0x01
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// byte should be emLen -hLen -sLen -2 and not -1! authors have been advised
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for (i = 0; i < (emLen - hLen - sLen - 2); i++)
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{
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if (DB[i] != 0)
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{
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if (Configuration.DEBUG)
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log.fine("DB[" + String.valueOf(i) + "] != 0x00");
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return false;
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}
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}
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if (DB[i] != 0x01)
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{ // i == emLen -hLen -sLen -2
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if (Configuration.DEBUG)
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log.fine("DB's byte at position (emLen -hLen -sLen -2); i.e. "
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+ String.valueOf(i) + " is not 0x01");
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return false;
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}
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// 11. Let salt be the last sLen octets of DB.
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byte[] salt = new byte[sLen];
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System.arraycopy(DB, DB.length - sLen, salt, 0, sLen);
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// 12. Let M0 = 00 00 00 00 00 00 00 00 || mHash || salt;
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// M0 is an octet string of length 8 + hLen + sLen with eight initial
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// zero octets.
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// 13. Let H0 = Hash(M0), an octet string of length hLen.
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byte[] H0;
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synchronized (hash)
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{
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for (i = 0; i < 8; i++)
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hash.update((byte) 0x00);
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hash.update(mHash, 0, hLen);
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hash.update(salt, 0, sLen);
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H0 = hash.digest();
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}
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// 14. If H = H0, output 'consistent.' Otherwise, output 'inconsistent.'
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return Arrays.equals(H, H0);
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}
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/**
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* A mask generation function takes an octet string of variable length and a
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* desired output length as input, and outputs an octet string of the desired
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* length. There may be restrictions on the length of the input and output
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* octet strings, but such bounds are generally very large. Mask generation
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* functions are deterministic; the octet string output is completely
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* determined by the input octet string. The output of a mask generation
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* function should be pseudorandom, that is, it should be infeasible to
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* predict, given one part of the output but not the input, another part of
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* the output. The provable security of RSA-PSS relies on the random nature of
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* the output of the mask generation function, which in turn relies on the
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* random nature of the underlying hash function.
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*
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* @param Z a seed.
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* @param l the desired output length in octets.
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* @return the mask.
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* @exception IllegalArgumentException if the desired output length is too
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* long.
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*/
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private byte[] MGF(byte[] Z, int l)
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{
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// 1. If l > (2**32).hLen, output 'mask too long' and stop.
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if (l < 1 || (l & 0xFFFFFFFFL) > ((hLen & 0xFFFFFFFFL) << 32L))
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throw new IllegalArgumentException("mask too long");
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// 2. Let T be the empty octet string.
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byte[] result = new byte[l];
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// 3. For i = 0 to CEILING(l/hLen) ? 1, do
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int limit = ((l + hLen - 1) / hLen) - 1;
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IMessageDigest hashZ = null;
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hashZ = (IMessageDigest) hash.clone();
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hashZ.digest();
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hashZ.update(Z, 0, Z.length);
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IMessageDigest hashZC = null;
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byte[] t;
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int sofar = 0;
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int length;
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for (int i = 0; i < limit; i++)
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{
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// 3.1 Convert i to an octet string C of length 4 with the primitive
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// I2OSP: C = I2OSP(i, 4).
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// 3.2 Concatenate the hash of the seed Z and C to the octet string T:
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// T = T || Hash(Z || C)
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hashZC = (IMessageDigest) hashZ.clone();
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hashZC.update((byte)(i >>> 24));
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hashZC.update((byte)(i >>> 16));
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hashZC.update((byte)(i >>> 8));
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hashZC.update((byte) i);
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t = hashZC.digest();
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length = l - sofar;
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length = (length > hLen ? hLen : length);
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System.arraycopy(t, 0, result, sofar, length);
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sofar += length;
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}
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// 4. Output the leading l octets of T as the octet string mask.
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return result;
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}
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}
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