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comparison src/com/trilead/ssh2/DHGexParameters.java @ 0:0ce5cc452d02

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initial version
author Carl Byington <carl@five-ten-sg.com>
date Thu, 22 May 2014 10:41:19 -0700
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1
2 package com.trilead.ssh2;
3
4 /**
5 * A <code>DHGexParameters</code> object can be used to specify parameters for
6 * the diffie-hellman group exchange.
7 * <p>
8 * Depending on which constructor is used, either the use of a
9 * <code>SSH_MSG_KEX_DH_GEX_REQUEST</code> or <code>SSH_MSG_KEX_DH_GEX_REQUEST_OLD</code>
10 * can be forced.
11 *
12 * @see Connection#setDHGexParameters(DHGexParameters)
13 * @author Christian Plattner, plattner@trilead.com
14 * @version $Id: DHGexParameters.java,v 1.1 2007/10/15 12:49:56 cplattne Exp $
15 */
16
17 public class DHGexParameters {
18 private final int min_group_len;
19 private final int pref_group_len;
20 private final int max_group_len;
21
22 private static final int MIN_ALLOWED = 1024;
23 private static final int MAX_ALLOWED = 8192;
24
25 /**
26 * Same as calling {@link #DHGexParameters(int, int, int) DHGexParameters(1024, 1024, 4096)}.
27 * This is also the default used by the Connection class.
28 *
29 */
30 public DHGexParameters() {
31 this(1024, 1024, 4096);
32 }
33
34 /**
35 * This constructor can be used to force the sending of a
36 * <code>SSH_MSG_KEX_DH_GEX_REQUEST_OLD</code> request.
37 * Internally, the minimum and maximum group lengths will
38 * be set to zero.
39 *
40 * @param pref_group_len has to be &gt= 1024 and &lt;= 8192
41 */
42 public DHGexParameters(int pref_group_len) {
43 if ((pref_group_len < MIN_ALLOWED) || (pref_group_len > MAX_ALLOWED))
44 throw new IllegalArgumentException("pref_group_len out of range!");
45
46 this.pref_group_len = pref_group_len;
47 this.min_group_len = 0;
48 this.max_group_len = 0;
49 }
50
51 /**
52 * This constructor can be used to force the sending of a
53 * <code>SSH_MSG_KEX_DH_GEX_REQUEST</code> request.
54 * <p>
55 * Note: older OpenSSH servers don't understand this request, in which
56 * case you should use the {@link #DHGexParameters(int)} constructor.
57 * <p>
58 * All values have to be &gt= 1024 and &lt;= 8192. Furthermore,
59 * min_group_len &lt;= pref_group_len &lt;= max_group_len.
60 *
61 * @param min_group_len
62 * @param pref_group_len
63 * @param max_group_len
64 */
65 public DHGexParameters(int min_group_len, int pref_group_len, int max_group_len) {
66 if ((min_group_len < MIN_ALLOWED) || (min_group_len > MAX_ALLOWED))
67 throw new IllegalArgumentException("min_group_len out of range!");
68
69 if ((pref_group_len < MIN_ALLOWED) || (pref_group_len > MAX_ALLOWED))
70 throw new IllegalArgumentException("pref_group_len out of range!");
71
72 if ((max_group_len < MIN_ALLOWED) || (max_group_len > MAX_ALLOWED))
73 throw new IllegalArgumentException("max_group_len out of range!");
74
75 if ((pref_group_len < min_group_len) || (pref_group_len > max_group_len))
76 throw new IllegalArgumentException("pref_group_len is incompatible with min and max!");
77
78 if (max_group_len < min_group_len)
79 throw new IllegalArgumentException("max_group_len must not be smaller than min_group_len!");
80
81 this.min_group_len = min_group_len;
82 this.pref_group_len = pref_group_len;
83 this.max_group_len = max_group_len;
84 }
85
86 /**
87 * Get the maximum group length.
88 *
89 * @return the maximum group length, may be <code>zero</code> if
90 * SSH_MSG_KEX_DH_GEX_REQUEST_OLD should be requested
91 */
92 public int getMax_group_len() {
93 return max_group_len;
94 }
95
96 /**
97 * Get the minimum group length.
98 *
99 * @return minimum group length, may be <code>zero</code> if
100 * SSH_MSG_KEX_DH_GEX_REQUEST_OLD should be requested
101 */
102 public int getMin_group_len() {
103 return min_group_len;
104 }
105
106 /**
107 * Get the preferred group length.
108 *
109 * @return the preferred group length
110 */
111 public int getPref_group_len() {
112 return pref_group_len;
113 }
114 }