|
1 package ch.ethz.ssh2.crypto;
2
3 import java.io.IOException  ;
4
5 import java.math.BigInteger ;
6
7
13 public class SimpleDERReader
14 {
15 byte[] buffer;
16 int pos;
17 int count;
18
19 public SimpleDERReader(byte[] b)
20 {
21 resetInput(b);
22 }
23
24 public SimpleDERReader(byte[] b, int off, int len)
25 {
26 resetInput(b, off, len);
27 }
28
29 public void resetInput(byte[] b)
30 {
31 resetInput(b, 0, b.length);
32 }
33
34 public void resetInput(byte[] b, int off, int len)
35 {
36 buffer = b;
37 pos = off;
38 count = len;
39 }
40
41 private byte readByte() throws IOException
42 {
43 if (count <= 0)
44 throw new IOException ("DER byte array: out of data");
45 count--;
46 return buffer[pos++];
47 }
48
49 private byte[] readBytes(int len) throws IOException
50 {
51 if (len > count)
52 throw new IOException ("DER byte array: out of data");
53
54 byte[] b = new byte[len];
55
56 System.arraycopy(buffer, pos, b, 0, len);
57
58 pos += len;
59 count -= len;
60
61 return b;
62 }
63
64 public int available()
65 {
66 return count;
67 }
68
69 private int readLength() throws IOException
70 {
71 int len = readByte() & 0xff;
72
73 if ((len & 0x80) == 0)
74 return len;
75
76 int remain = len & 0x7F;
77
78 if (remain == 0)
79 return -1;
80
81 len = 0;
82
83 while (remain > 0)
84 {
85 len = len << 8;
86 len = len | (readByte() & 0xff);
87 remain--;
88 }
89
90 return len;
91 }
92
93 public int ignoreNextObject() throws IOException
94 {
95 int type = readByte() & 0xff;
96
97 int len = readLength();
98
99 if ((len < 0) || len > available())
100 throw new IOException ("Illegal len in DER object (" + len + ")");
101
102 readBytes(len);
103
104 return type;
105 }
106
107 public BigInteger readInt() throws IOException
108 {
109 int type = readByte() & 0xff;
110
111 if (type != 0x02)
112 throw new IOException ("Expected DER Integer, but found type " + type);
113
114 int len = readLength();
115
116 if ((len < 0) || len > available())
117 throw new IOException ("Illegal len in DER object (" + len + ")");
118
119 byte[] b = readBytes(len);
120
121 BigInteger bi = new BigInteger (b);
122
123 return bi;
124 }
125
126 public byte[] readSequenceAsByteArray() throws IOException
127 {
128 int type = readByte() & 0xff;
129
130 if (type != 0x30)
131 throw new IOException ("Expected DER Sequence, but found type " + type);
132
133 int len = readLength();
134
135 if ((len < 0) || len > available())
136 throw new IOException ("Illegal len in DER object (" + len + ")");
137
138 byte[] b = readBytes(len);
139
140 return b;
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 byte[] b = readBytes(len);
156
157 return b;
158 }
159
160 }
161 |
Popular Tags |
Java API By Example, From Geeks To Geeks.