134 lines
6.2 KiB
C#
134 lines
6.2 KiB
C#
/*
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* Copyright (c) Contributors, http://opensimulator.org/
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* See CONTRIBUTORS.TXT for a full list of copyright holders.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the OpenSim Project nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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using System;
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using System.Security.Cryptography;
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using System.Text;
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namespace OpenSim.Framework
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{
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/// <summary>
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/// NEEDS AUDIT.
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/// </summary>
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/// <remarks>
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/// Suggested implementation
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/// <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>
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/// <para>When sending data to the foreign host - run 'Sign' on the data and affix the returned byte[] to the message.</para>
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/// <para>When recieving data from the foreign host - run 'Authenticate' against the data and the attached byte[].</para>
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/// <para>Both hosts should be performing these operations for this to be effective.</para>
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/// </remarks>
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internal class RemoteDigest
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{
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private byte[] currentHash;
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private byte[] secret;
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private SHA512Managed SHA512;
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/// <summary>
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/// Initialises a new RemoteDigest authentication mechanism
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/// </summary>
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/// <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>
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/// <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>
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/// <param name="salt">Binary salt - some common value - to be decided what</param>
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/// <param name="challenge">The challenge key provided by the third party</param>
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public RemoteDigest(string sharedSecret, byte[] salt, string challenge)
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{
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SHA512 = new SHA512Managed();
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Rfc2898DeriveBytes RFC2898 = new Rfc2898DeriveBytes(sharedSecret, salt);
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secret = RFC2898.GetBytes(512);
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ASCIIEncoding ASCII = new ASCIIEncoding();
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currentHash = SHA512.ComputeHash(AppendArrays(secret, ASCII.GetBytes(challenge)));
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}
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/// <summary>
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/// Authenticates a piece of incoming data against the local digest. Upon successful authentication, digest string is incremented.
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/// </summary>
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/// <param name="data">The incoming data</param>
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/// <param name="digest">The remote digest</param>
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/// <returns></returns>
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public bool Authenticate(byte[] data, byte[] digest)
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{
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byte[] newHash = SHA512.ComputeHash(AppendArrays(AppendArrays(currentHash, secret), data));
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if (digest == newHash)
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{
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currentHash = newHash;
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return true;
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}
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else
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{
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throw new Exception("Hash comparison failed. Key resync required.");
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}
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}
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/// <summary>
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/// Signs a new bit of data with the current hash. Returns a byte array which should be affixed to the message.
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/// Signing a piece of data will automatically increment the hash - if you sign data and do not send it, the
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/// hashes will get out of sync and throw an exception when validation is attempted.
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/// </summary>
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/// <param name="data">The outgoing data</param>
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/// <returns>The local digest</returns>
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public byte[] Sign(byte[] data)
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{
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currentHash = SHA512.ComputeHash(AppendArrays(AppendArrays(currentHash, secret), data));
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return currentHash;
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}
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/// <summary>
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/// 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.
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/// </summary>
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/// <returns>A 128-character hexadecimal string containing the challenge.</returns>
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public static string GenerateChallenge()
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{
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RNGCryptoServiceProvider RNG = new RNGCryptoServiceProvider();
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byte[] bytes = new byte[64];
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RNG.GetBytes(bytes);
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StringBuilder sb = new StringBuilder(bytes.Length*2);
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foreach (byte b in bytes)
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{
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sb.AppendFormat("{0:x2}", b);
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}
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return sb.ToString();
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}
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/// <summary>
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/// Helper function, merges two byte arrays
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/// </summary>
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/// <remarks>Sourced from MSDN Forum</remarks>
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/// <param name="a">A</param>
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/// <param name="b">B</param>
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/// <returns>C</returns>
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private byte[] AppendArrays(byte[] a, byte[] b)
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{
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byte[] c = new byte[a.Length + b.Length];
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Buffer.BlockCopy(a, 0, c, 0, a.Length);
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Buffer.BlockCopy(b, 0, c, a.Length, b.Length);
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return c;
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}
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}
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} |