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1: /* DSSSignatureX509Codec.java -- X.509 encoder/decoder for DSS signatures 2: Copyright (C) 2006 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.java.security.sig.dss; 40: 41: import gnu.java.security.Registry; 42: import gnu.java.security.der.DER; 43: import gnu.java.security.der.DERReader; 44: import gnu.java.security.der.DERValue; 45: import gnu.java.security.der.DERWriter; 46: import gnu.java.security.sig.ISignatureCodec; 47: import gnu.java.security.util.DerUtil; 48: 49: import java.io.ByteArrayOutputStream; 50: import java.io.IOException; 51: import java.math.BigInteger; 52: import java.security.InvalidParameterException; 53: import java.util.ArrayList; 54: 55: /** 56: * An implementation of an {@link ISignatureCodec} that knows to encode and 57: * decode DSS signatures into the raw bytes which would constitute a DER-encoded 58: * form of the ASN.1 structure defined in RFC-2459, and RFC-2313 as described in 59: * the next paragraphs. 60: * <p> 61: * Digital signatures when transmitted in an X.509 certificates are encoded 62: * in DER (Distinguished Encoding Rules) as a BIT STRING; i.e. 63: * 64: * <pre> 65: * Certificate ::= SEQUENCE { 66: * tbsCertificate TBSCertificate, 67: * signatureAlgorithm AlgorithmIdentifier, 68: * signature BIT STRING 69: * } 70: * </pre> 71: * <p> 72: * The output of the encoder, and the input of the decoder, of this codec are 73: * then the <i>raw</i> bytes of such a BIT STRING; i.e. not the DER-encoded 74: * form itself. 75: * <p> 76: * RFC-2459 states that, for the Digital Signature Standard (DSS), which 77: * generates two MPIs, commonly called <code>r</code> and <code>s</code>, as the 78: * result of digitally signing a message, these two numbers will be transferred 79: * as the following ASN.1 structure: 80: * 81: * <pre> 82: * Dss-Sig-Value ::= SEQUENCE { 83: * r INTEGER, 84: * s INTEGER 85: * } 86: * </pre> 87: * <p> 88: * Client code that needs to build a DER BIT STRING <b>MUST</b> construct such 89: * an ASN.1 value. The following is an example of how to do this: 90: * <p> 91: * <pre> 92: * ... 93: * import gnu.java.security.der.BitString; 94: * import gnu.java.security.der.DER; 95: * import gnu.java.security.der.DERValue; 96: * ... 97: * DERValue bitString = new DERValue(DER.BIT_STRING, new BitString(sigBytes)); 98: * ... 99: * </pre> 100: */ 101: public class DSSSignatureX509Codec 102: implements ISignatureCodec 103: { 104: // implicit 0-arguments constructor 105: 106: public int getFormatID() 107: { 108: return Registry.X509_ENCODING_ID; 109: } 110: 111: /** 112: * Encodes a DSS Signature output as the <i>signature</i> raw bytes which can 113: * be used to construct an ASN.1 DER-encoded BIT STRING as defined in the 114: * documentation of this class. 115: * 116: * @param signature the output of the DSS signature algorithm; i.e. the value 117: * returned by the invocation of 118: * {@link gnu.java.security.sig.ISignature#sign()} method. In the 119: * case of a DSS signature this is an array of two MPIs called 120: * <code>r</code> and <code>s</code>. 121: * @return the raw bytes of a DSS signature which could be then used as the 122: * contents of a BIT STRING as per rfc-2459. 123: * @throws InvalidParameterException if an exception occurs during the 124: * marshalling process. 125: */ 126: public byte[] encodeSignature(Object signature) 127: { 128: BigInteger[] rs = (BigInteger[]) signature; 129: 130: DERValue derR = new DERValue(DER.INTEGER, rs[0]); 131: DERValue derS = new DERValue(DER.INTEGER, rs[1]); 132: 133: ArrayList dssSigValue = new ArrayList(2); 134: dssSigValue.add(derR); 135: dssSigValue.add(derS); 136: DERValue derDssSigValue = new DERValue(DER.CONSTRUCTED | DER.SEQUENCE, 137: dssSigValue); 138: byte[] result; 139: ByteArrayOutputStream baos = new ByteArrayOutputStream(); 140: try 141: { 142: DERWriter.write(baos, derDssSigValue); 143: result = baos.toByteArray(); 144: } 145: catch (IOException x) 146: { 147: InvalidParameterException y = new InvalidParameterException(); 148: y.initCause(x); 149: throw y; 150: } 151: 152: return result; 153: } 154: 155: /** 156: * Decodes a <i>signature</i> as defined in the documentation of this class. 157: * 158: * @param input the byte array to unmarshall into a valid DSS signature 159: * instance; i.e. an array of two MPIs. MUST NOT be null. 160: * @return an array of two MPIs, <code>r</code> and <code>s</code> in this 161: * order, decoded from the designated <code>input</code>. 162: * @throw InvalidParameterException if an exception occurs during the 163: * unmarshalling process. 164: */ 165: public Object decodeSignature(byte[] input) 166: { 167: if (input == null) 168: throw new InvalidParameterException("Input bytes MUST NOT be null"); 169: 170: BigInteger r, s; 171: DERReader der = new DERReader(input); 172: try 173: { 174: DERValue derDssSigValue = der.read(); 175: DerUtil.checkIsConstructed(derDssSigValue, "Wrong Dss-Sig-Value field"); 176: 177: DERValue val = der.read(); 178: DerUtil.checkIsBigInteger(val, "Wrong R field"); 179: r = (BigInteger) val.getValue(); 180: val = der.read(); 181: DerUtil.checkIsBigInteger(val, "Wrong S field"); 182: s = (BigInteger) val.getValue(); 183: } 184: catch (IOException x) 185: { 186: InvalidParameterException y = new InvalidParameterException(); 187: y.initCause(x); 188: throw y; 189: } 190: 191: return new BigInteger[] { r, s }; 192: } 193: }