1 /* 2 * Copyright (c) 2006-2011 Christian Plattner. All rights reserved. 3 * Please refer to the LICENSE.txt for licensing details. 4 */ 5 package ch.ethz.ssh2.crypto; 6 7 import java.io.IOException; 8 9 import java.math.BigInteger; 10 11 /** 12 * SimpleDERReader. 13 * 14 * @author Christian Plattner 15 * @version 2.50, 03/15/10 16 */ 17 public class SimpleDERReader 18 { 19 byte[] buffer; 20 int pos; 21 int count; 22 23 public SimpleDERReader(byte[] b) 24 { 25 resetInput(b); 26 } 27 28 public SimpleDERReader(byte[] b, int off, int len) 29 { 30 resetInput(b, off, len); 31 } 32 33 public void resetInput(byte[] b) 34 { 35 resetInput(b, 0, b.length); 36 } 37 38 public void resetInput(byte[] b, int off, int len) 39 { 40 buffer = b; 41 pos = off; 42 count = len; 43 } 44 45 private byte readByte() throws IOException 46 { 47 if (count <= 0) 48 throw new IOException("DER byte array: out of data"); 49 count--; 50 return buffer[pos++]; 51 } 52 53 private byte[] readBytes(int len) throws IOException 54 { 55 if (len > count) 56 throw new IOException("DER byte array: out of data"); 57 58 byte[] b = new byte[len]; 59 60 System.arraycopy(buffer, pos, b, 0, len); 61 62 pos += len; 63 count -= len; 64 65 return b; 66 } 67 68 public int available() 69 { 70 return count; 71 } 72 73 private int readLength() throws IOException 74 { 75 int len = readByte() & 0xff; 76 77 if ((len & 0x80) == 0) 78 return len; 79 80 int remain = len & 0x7F; 81 82 if (remain == 0) 83 return -1; 84 85 len = 0; 86 87 while (remain > 0) 88 { 89 len = len << 8; 90 len = len | (readByte() & 0xff); 91 remain--; 92 } 93 94 return len; 95 } 96 97 public int ignoreNextObject() throws IOException 98 { 99 int type = readByte() & 0xff; 100 101 int len = readLength(); 102 103 if ((len < 0) || len > available()) 104 throw new IOException("Illegal len in DER object (" + len + ")"); 105 106 readBytes(len); 107 108 return type; 109 } 110 111 public BigInteger readInt() throws IOException 112 { 113 int type = readByte() & 0xff; 114 115 if (type != 0x02) 116 throw new IOException("Expected DER Integer, but found type " + type); 117 118 int len = readLength(); 119 120 if ((len < 0) || len > available()) 121 throw new IOException("Illegal len in DER object (" + len + ")"); 122 123 byte[] b = readBytes(len); 124 125 return new BigInteger(b); 126 } 127 128 public byte[] readSequenceAsByteArray() throws IOException 129 { 130 int type = readByte() & 0xff; 131 132 if (type != 0x30) 133 throw new IOException("Expected DER Sequence, but found type " + type); 134 135 int len = readLength(); 136 137 if ((len < 0) || len > available()) 138 throw new IOException("Illegal len in DER object (" + len + ")"); 139 140 return readBytes(len); 141 } 142 143 public byte[] readOctetString() throws IOException 144 { 145 int type = readByte() & 0xff; 146 147 if (type != 0x04) 148 throw new IOException("Expected DER Octetstring, but found type " + type); 149 150 int len = readLength(); 151 152 if ((len < 0) || len > available()) 153 throw new IOException("Illegal len in DER object (" + len + ")"); 154 155 return readBytes(len); 156 } 157 158 } 159
