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1
2 package ch.ethz.ssh2.signature;
3
4 import java.io.IOException  ;
5 import java.math.BigInteger ;
6
7 import ch.ethz.ssh2.crypto.SimpleDERReader;
8 import ch.ethz.ssh2.crypto.digest.SHA1;
9 import ch.ethz.ssh2.log.Logger;
10 import ch.ethz.ssh2.packets.TypesReader;
11 import ch.ethz.ssh2.packets.TypesWriter;
12
13
19 public class RSASHA1Verify
20 {
21 private static final Logger log = Logger.getLogger(RSASHA1Verify.class);
22
23 public static RSAPublicKey decodeSSHRSAPublicKey(byte[] key) throws IOException
24 {
25 TypesReader tr = new TypesReader(key);
26
27 String key_format = tr.readString();
28
29 if (key_format.equals("ssh-rsa") == false)
30 throw new IllegalArgumentException ("This is not a ssh-rsa public key");
31
32 BigInteger e = tr.readMPINT();
33 BigInteger n = tr.readMPINT();
34
35 if (tr.remain() != 0)
36 throw new IOException ("Padding in RSA public key!");
37
38 return new RSAPublicKey(e, n);
39 }
40
41 public static byte[] encodeSSHRSAPublicKey(RSAPublicKey pk) throws IOException
42 {
43 TypesWriter tw = new TypesWriter();
44
45 tw.writeString("ssh-rsa");
46 tw.writeMPInt(pk.getE());
47 tw.writeMPInt(pk.getN());
48
49 return tw.getBytes();
50 }
51
52 public static RSASignature decodeSSHRSASignature(byte[] sig) throws IOException
53 {
54 TypesReader tr = new TypesReader(sig);
55
56 String sig_format = tr.readString();
57
58 if (sig_format.equals("ssh-rsa") == false)
59 throw new IOException ("Peer sent wrong signature format");
60
61
65
66 byte[] s = tr.readByteString();
67
68 if (s.length == 0)
69 throw new IOException ("Error in RSA signature, S is empty.");
70
71 if (log.isEnabled())
72 {
73 log.log(80, "Decoding ssh-rsa signature string (length: " + s.length + ")");
74 }
75
76 if (tr.remain() != 0)
77 throw new IOException ("Padding in RSA signature!");
78
79 return new RSASignature(new BigInteger (1, s));
80 }
81
82 public static byte[] encodeSSHRSASignature(RSASignature sig) throws IOException
83 {
84 TypesWriter tw = new TypesWriter();
85
86 tw.writeString("ssh-rsa");
87
88
92
93 byte[] s = sig.getS().toByteArray();
94
95
96
97 if ((s.length > 1) && (s[0] == 0x00))
98 tw.writeString(s, 1, s.length - 1);
99 else
100 tw.writeString(s, 0, s.length);
101
102 return tw.getBytes();
103 }
104
105 public static RSASignature generateSignature(byte[] message, RSAPrivateKey pk) throws IOException
106 {
107 SHA1 md = new SHA1();
108 md.update(message);
109 byte[] sha_message = new byte[md.getDigestLength()];
110 md.digest(sha_message);
111
112 byte[] der_header = new byte[] { 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00,
113 0x04, 0x14 };
114
115 int rsa_block_len = (pk.getN().bitLength() + 7) / 8;
116
117 int num_pad = rsa_block_len - (2 + der_header.length + sha_message.length) - 1;
118
119 if (num_pad < 8)
120 throw new IOException ("Cannot sign with RSA, message too long");
121
122 byte[] sig = new byte[der_header.length + sha_message.length + 2 + num_pad];
123
124 sig[0] = 0x01;
125
126 for (int i = 0; i < num_pad; i++)
127 {
128 sig[i + 1] = (byte) 0xff;
129 }
130
131 sig[num_pad + 1] = 0x00;
132
133 System.arraycopy(der_header, 0, sig, 2 + num_pad, der_header.length);
134 System.arraycopy(sha_message, 0, sig, 2 + num_pad + der_header.length, sha_message.length);
135
136 BigInteger m = new BigInteger (1, sig);
137
138 BigInteger s = m.modPow(pk.getD(), pk.getN());
139
140 return new RSASignature(s);
141 }
142
143 public static boolean verifySignature(byte[] message, RSASignature ds, RSAPublicKey dpk) throws IOException
144 {
145 SHA1 md = new SHA1();
146 md.update(message);
147 byte[] sha_message = new byte[md.getDigestLength()];
148 md.digest(sha_message);
149
150 BigInteger n = dpk.getN();
151 BigInteger e = dpk.getE();
152 BigInteger s = ds.getS();
153
154 if (n.compareTo(s) <= 0)
155 {
156 log.log(20, "ssh-rsa signature: n.compareTo(s) <= 0");
157 return false;
158 }
159
160 int rsa_block_len = (n.bitLength() + 7) / 8;
161
162
163
164 if (rsa_block_len < 1)
165 {
166 log.log(20, "ssh-rsa signature: rsa_block_len < 1");
167 return false;
168 }
169
170 byte[] v = s.modPow(e, n).toByteArray();
171
172 int startpos = 0;
173
174 if ((v.length > 0) && (v[0] == 0x00))
175 startpos++;
176
177 if ((v.length - startpos) != (rsa_block_len - 1))
178 {
179 log.log(20, "ssh-rsa signature: (v.length - startpos) != (rsa_block_len - 1)");
180 return false;
181 }
182
183 if (v[startpos] != 0x01)
184 {
185 log.log(20, "ssh-rsa signature: v[startpos] != 0x01");
186 return false;
187 }
188
189 int pos = startpos + 1;
190
191 while (true)
192 {
193 if (pos >= v.length)
194 {
195 log.log(20, "ssh-rsa signature: pos >= v.length");
196 return false;
197 }
198 if (v[pos] == 0x00)
199 break;
200 if (v[pos] != (byte) 0xff)
201 {
202 log.log(20, "ssh-rsa signature: v[pos] != (byte) 0xff");
203 return false;
204 }
205 pos++;
206 }
207
208 int num_pad = pos - (startpos + 1);
209
210 if (num_pad < 8)
211 {
212 log.log(20, "ssh-rsa signature: num_pad < 8");
213 return false;
214 }
215
216 pos++;
217
218 if (pos >= v.length)
219 {
220 log.log(20, "ssh-rsa signature: pos >= v.length");
221 return false;
222 }
223
224 SimpleDERReader dr = new SimpleDERReader(v, pos, v.length - pos);
225
226 byte[] seq = dr.readSequenceAsByteArray();
227
228 if (dr.available() != 0)
229 {
230 log.log(20, "ssh-rsa signature: dr.available() != 0");
231 return false;
232 }
233
234 dr.resetInput(seq);
235
236
237
238 byte digestAlgorithm[] = dr.readSequenceAsByteArray();
239
240
241
242 if ((digestAlgorithm.length < 8) || (digestAlgorithm.length > 9))
243 {
244 log.log(20, "ssh-rsa signature: (digestAlgorithm.length < 8) || (digestAlgorithm.length > 9)");
245 return false;
246 }
247
248 byte[] digestAlgorithm_sha1 = new byte[] { 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00 };
249
250 for (int i = 0; i < digestAlgorithm.length; i++)
251 {
252 if (digestAlgorithm[i] != digestAlgorithm_sha1[i])
253 {
254 log.log(20, "ssh-rsa signature: digestAlgorithm[i] != digestAlgorithm_sha1[i]");
255 return false;
256 }
257 }
258
259 byte[] digest = dr.readOctetString();
260
261 if (dr.available() != 0)
262 {
263 log.log(20, "ssh-rsa signature: dr.available() != 0 (II)");
264 return false;
265 }
266
267 if (digest.length != sha_message.length)
268 {
269 log.log(20, "ssh-rsa signature: digest.length != sha_message.length");
270 return false;
271 }
272
273 for (int i = 0; i < sha_message.length; i++)
274 {
275 if (sha_message[i] != digest[i])
276 {
277 log.log(20, "ssh-rsa signature: sha_message[i] != digest[i]");
278 return false;
279 }
280 }
281
282 return true;
283 }
284 }
285 |
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