diff options
Diffstat (limited to 'src/main/java/ch/ethz/ssh2/DHGexParameters.java')
-rw-r--r-- | src/main/java/ch/ethz/ssh2/DHGexParameters.java | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/src/main/java/ch/ethz/ssh2/DHGexParameters.java b/src/main/java/ch/ethz/ssh2/DHGexParameters.java new file mode 100644 index 0000000..8c18c06 --- /dev/null +++ b/src/main/java/ch/ethz/ssh2/DHGexParameters.java @@ -0,0 +1,124 @@ +/* + * Copyright (c) 2006-2011 Christian Plattner. All rights reserved. + * Please refer to the LICENSE.txt for licensing details. + */ +package ch.ethz.ssh2; + +/** + * A <code>DHGexParameters</code> object can be used to specify parameters for + * the diffie-hellman group exchange. + * <p> + * Depending on which constructor is used, either the use of a + * <code>SSH_MSG_KEX_DH_GEX_REQUEST</code> or <code>SSH_MSG_KEX_DH_GEX_REQUEST_OLD</code> + * can be forced. + * + * @see Connection#setDHGexParameters(DHGexParameters) + * @author Christian Plattner + * @version 2.50, 03/15/10 + */ + +public class DHGexParameters +{ + private final int min_group_len; + private final int pref_group_len; + private final int max_group_len; + + private static final int MIN_ALLOWED = 1024; + private static final int MAX_ALLOWED = 8192; + + /** + * Same as calling {@link #DHGexParameters(int, int, int) DHGexParameters(1024, 1024, 4096)}. + * This is also the default used by the Connection class. + * + */ + public DHGexParameters() + { + this(1024, 1024, 4096); + } + + /** + * This constructor can be used to force the sending of a + * <code>SSH_MSG_KEX_DH_GEX_REQUEST_OLD</code> request. + * Internally, the minimum and maximum group lengths will + * be set to zero. + * + * @param pref_group_len has to be >= 1024 and <= 8192 + */ + public DHGexParameters(int pref_group_len) + { + if ((pref_group_len < MIN_ALLOWED) || (pref_group_len > MAX_ALLOWED)) + throw new IllegalArgumentException("pref_group_len out of range!"); + + this.pref_group_len = pref_group_len; + this.min_group_len = 0; + this.max_group_len = 0; + } + + /** + * This constructor can be used to force the sending of a + * <code>SSH_MSG_KEX_DH_GEX_REQUEST</code> request. + * <p> + * Note: older OpenSSH servers don't understand this request, in which + * case you should use the {@link #DHGexParameters(int)} constructor. + * <p> + * All values have to be >= 1024 and <= 8192. Furthermore, + * min_group_len <= pref_group_len <= max_group_len. + * + * @param min_group_len + * @param pref_group_len + * @param max_group_len + */ + public DHGexParameters(int min_group_len, int pref_group_len, int max_group_len) + { + if ((min_group_len < MIN_ALLOWED) || (min_group_len > MAX_ALLOWED)) + throw new IllegalArgumentException("min_group_len out of range!"); + + if ((pref_group_len < MIN_ALLOWED) || (pref_group_len > MAX_ALLOWED)) + throw new IllegalArgumentException("pref_group_len out of range!"); + + if ((max_group_len < MIN_ALLOWED) || (max_group_len > MAX_ALLOWED)) + throw new IllegalArgumentException("max_group_len out of range!"); + + if ((pref_group_len < min_group_len) || (pref_group_len > max_group_len)) + throw new IllegalArgumentException("pref_group_len is incompatible with min and max!"); + + if (max_group_len < min_group_len) + throw new IllegalArgumentException("max_group_len must not be smaller than min_group_len!"); + + this.min_group_len = min_group_len; + this.pref_group_len = pref_group_len; + this.max_group_len = max_group_len; + } + + /** + * Get the maximum group length. + * + * @return the maximum group length, may be <code>zero</code> if + * SSH_MSG_KEX_DH_GEX_REQUEST_OLD should be requested + */ + public int getMax_group_len() + { + return max_group_len; + } + + /** + * Get the minimum group length. + * + * @return minimum group length, may be <code>zero</code> if + * SSH_MSG_KEX_DH_GEX_REQUEST_OLD should be requested + */ + public int getMin_group_len() + { + return min_group_len; + } + + /** + * Get the preferred group length. + * + * @return the preferred group length + */ + public int getPref_group_len() + { + return pref_group_len; + } +} |