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1
2 package ch.ethz.ssh2.crypto.cipher;
3
4 import java.io.IOException  ;
5 import java.io.InputStream ;
6
7
13 public class CipherInputStream
14 {
15 BlockCipher currentCipher;
16 InputStream bi;
17 byte[] buffer;
18 byte[] enc;
19 int blockSize;
20 int pos;
21
22
26
27 final int BUFF_SIZE = 2048;
28 byte[] input_buffer = new byte[BUFF_SIZE];
29 int input_buffer_pos = 0;
30 int input_buffer_size = 0;
31
32 public CipherInputStream(BlockCipher tc, InputStream bi)
33 {
34 this.bi = bi;
35 changeCipher(tc);
36 }
37
38 private int fill_buffer() throws IOException
39 {
40 input_buffer_pos = 0;
41 input_buffer_size = bi.read(input_buffer, 0, BUFF_SIZE);
42 return input_buffer_size;
43 }
44
45 private int internal_read(byte[] b, int off, int len) throws IOException
46 {
47 if (input_buffer_size < 0)
48 return -1;
49
50 if (input_buffer_pos >= input_buffer_size)
51 {
52 if (fill_buffer() <= 0)
53 return -1;
54 }
55
56 int avail = input_buffer_size - input_buffer_pos;
57 int thiscopy = (len > avail) ? avail : len;
58
59 System.arraycopy(input_buffer, input_buffer_pos, b, off, thiscopy);
60 input_buffer_pos += thiscopy;
61
62 return thiscopy;
63 }
64
65 public void changeCipher(BlockCipher bc)
66 {
67 this.currentCipher = bc;
68 blockSize = bc.getBlockSize();
69 buffer = new byte[blockSize];
70 enc = new byte[blockSize];
71 pos = blockSize;
72 }
73
74 private void getBlock() throws IOException
75 {
76 int n = 0;
77 while (n < blockSize)
78 {
79 int len = internal_read(enc, n, blockSize - n);
80 if (len < 0)
81 throw new IOException ("Cannot read full block, EOF reached.");
82 n += len;
83 }
84
85 try
86 {
87 currentCipher.transformBlock(enc, 0, buffer, 0);
88 }
89 catch (Exception e)
90 {
91 throw new IOException ("Error while decrypting block.");
92 }
93 pos = 0;
94 }
95
96 public int read(byte[] dst) throws IOException
97 {
98 return read(dst, 0, dst.length);
99 }
100
101 public int read(byte[] dst, int off, int len) throws IOException
102 {
103 int count = 0;
104
105 while (len > 0)
106 {
107 if (pos >= blockSize)
108 getBlock();
109
110 int avail = blockSize - pos;
111 int copy = Math.min(avail, len);
112 System.arraycopy(buffer, pos, dst, off, copy);
113 pos += copy;
114 off += copy;
115 len -= copy;
116 count += copy;
117 }
118 return count;
119 }
120
121 public int read() throws IOException
122 {
123 if (pos >= blockSize)
124 {
125 getBlock();
126 }
127 return buffer[pos++] & 0xff;
128 }
129
130 public int readPlain(byte[] b, int off, int len) throws IOException
131 {
132 if (pos != blockSize)
133 throw new IOException ("Cannot read plain since crypto buffer is not aligned.");
134 int n = 0;
135 while (n < len)
136 {
137 int cnt = internal_read(b, off + n, len - n);
138 if (cnt < 0)
139 throw new IOException ("Cannot fill buffer, EOF reached.");
140 n += cnt;
141 }
142 return n;
143 }
144 }
145 |
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