1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
/*
* Copyright (c) Contributors, http://opensimulator.org/
* See CONTRIBUTORS.TXT for a full list of copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the OpenSim Project nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
using System;
using System.Security.Cryptography;
using System.Text;
namespace OpenSim.Framework
{
/// <summary>
/// NEEDS AUDIT.
/// </summary>
/// <remarks>
/// Suggested implementation
/// <para>Store two digests for each foreign host. A local copy of the local hash using the local challenge (when issued), and a local copy of the remote hash using the remote challenge.</para>
/// <para>When sending data to the foreign host - run 'Sign' on the data and affix the returned byte[] to the message.</para>
/// <para>When receiving data from the foreign host - run 'Authenticate' against the data and the attached byte[].</para>
/// <para>Both hosts should be performing these operations for this to be effective.</para>
/// </remarks>
internal class RemoteDigest
{
private byte[] currentHash;
private byte[] secret;
private SHA512Managed SHA512;
/// <summary>
/// Initialises a new RemoteDigest authentication mechanism
/// </summary>
/// <remarks>Needs an audit by a cryptographic professional - was not "roll your own"'d by choice but rather a serious lack of decent authentication mechanisms in .NET remoting</remarks>
/// <param name="sharedSecret">The shared secret between systems (for inter-sim, this is provided in encrypted form during connection, for grid this is input manually in setup)</param>
/// <param name="salt">Binary salt - some common value - to be decided what</param>
/// <param name="challenge">The challenge key provided by the third party</param>
public RemoteDigest(string sharedSecret, byte[] salt, string challenge)
{
SHA512 = new SHA512Managed();
Rfc2898DeriveBytes RFC2898 = new Rfc2898DeriveBytes(sharedSecret, salt);
secret = RFC2898.GetBytes(512);
ASCIIEncoding ASCII = new ASCIIEncoding();
currentHash = SHA512.ComputeHash(AppendArrays(secret, ASCII.GetBytes(challenge)));
}
/// <summary>
/// Authenticates a piece of incoming data against the local digest. Upon successful authentication, digest string is incremented.
/// </summary>
/// <param name="data">The incoming data</param>
/// <param name="digest">The remote digest</param>
/// <returns></returns>
public bool Authenticate(byte[] data, byte[] digest)
{
byte[] newHash = SHA512.ComputeHash(AppendArrays(AppendArrays(currentHash, secret), data));
if (digest == newHash)
{
currentHash = newHash;
return true;
}
else
{
throw new Exception("Hash comparison failed. Key resync required.");
}
}
/// <summary>
/// Signs a new bit of data with the current hash. Returns a byte array which should be affixed to the message.
/// Signing a piece of data will automatically increment the hash - if you sign data and do not send it, the
/// hashes will get out of sync and throw an exception when validation is attempted.
/// </summary>
/// <param name="data">The outgoing data</param>
/// <returns>The local digest</returns>
public byte[] Sign(byte[] data)
{
currentHash = SHA512.ComputeHash(AppendArrays(AppendArrays(currentHash, secret), data));
return currentHash;
}
/// <summary>
/// Generates a new challenge string to be issued to a foreign host. Challenges are 1024-bit (effective strength of less than 512-bits) messages generated using the Crytographic Random Number Generator.
/// </summary>
/// <returns>A 128-character hexadecimal string containing the challenge.</returns>
public static string GenerateChallenge()
{
RNGCryptoServiceProvider RNG = new RNGCryptoServiceProvider();
byte[] bytes = new byte[64];
RNG.GetBytes(bytes);
StringBuilder sb = new StringBuilder(bytes.Length*2);
foreach (byte b in bytes)
{
sb.AppendFormat("{0:x2}", b);
}
return sb.ToString();
}
/// <summary>
/// Helper function, merges two byte arrays
/// </summary>
/// <remarks>Sourced from MSDN Forum</remarks>
/// <param name="a">A</param>
/// <param name="b">B</param>
/// <returns>C</returns>
private byte[] AppendArrays(byte[] a, byte[] b)
{
byte[] c = new byte[a.Length + b.Length];
Buffer.BlockCopy(a, 0, c, 0, a.Length);
Buffer.BlockCopy(b, 0, c, a.Length, b.Length);
return c;
}
}
}
|
