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HashGenerator.cs
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HashGenerator.cs
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#region License
// Jdenticon-net
// https://github.com/dmester/jdenticon-net
// Copyright © Daniel Mester Pirttijärvi 2016
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#endregion
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Text;
#if HAVE_HASH_ALGORITHMS
using System.Security.Cryptography;
#else
using Jdenticon.HashAlgorithms;
#endif
#nullable enable
namespace Jdenticon
{
/// <summary>
/// Helper class for generating hashes for any values.
/// </summary>
public static class HashGenerator
{
/// <summary>
/// Compute a hash for the string representation of a specified value.
/// </summary>
/// <param name="value">Value that will be converted to a string and then hashed. Null
/// values are supported and handled as empty strings.</param>
/// <param name="hashAlgorithmName">The name of the hash algorithm to be used for hashing.</param>
/// <exception cref="System.ArgumentException">The specified <paramref name="hashAlgorithmName"/> is not supported.</exception>
/// <remarks>
/// <para>
/// This method will use <see cref="Object.ToString"/> to generate a string representation of
/// <paramref name="value"/> and then hash the UTF8 representation of the string using
/// the specified algorithm. If <paramref name="value"/> is <c>null</c> an empty byte array
/// is hashed.
/// </para>
/// <note type="security">
/// <para>
/// Avoid using sensitive information as base for an icon, especially in combination with
/// a weak hash algorithm like MD5 and SHA1. Consider using public information instead,
/// like an id or a user name.
/// </para>
/// </note>
/// <para>
/// Hash algorithms available as <paramref name="hashAlgorithmName"/> depends on the platform.
/// The table below lists the possible values and on what platforms they are supported.
/// </para>
/// <list type="table">
/// <title>Supported hash algorithms per platform.</title>
/// <listheader>
/// <term>Hash algorithm</term>
/// <term>.NET Standard 1.0</term>
/// <term>.NET Standard 1.3</term>
/// <term>.NET Framework</term>
/// </listheader>
/// <item>
/// <term>MD5</term>
/// <term>Yes</term>
/// <term>Yes</term>
/// <term>Yes</term>
/// </item>
/// <item>
/// <term>SHA1</term>
/// <term>Yes</term>
/// <term>Yes</term>
/// <term>Yes</term>
/// </item>
/// <item>
/// <term>SHA256</term>
/// <term>-</term>
/// <term>Yes</term>
/// <term>Yes</term>
/// </item>
/// <item>
/// <term>SHA384</term>
/// <term>-</term>
/// <term>Yes</term>
/// <term>Yes</term>
/// </item>
/// <item>
/// <term>SHA512</term>
/// <term>-</term>
/// <term>Yes</term>
/// <term>Yes</term>
/// </item>
/// </list>
/// </remarks>
public static byte[] ComputeHash(object? value, string hashAlgorithmName)
{
string stringData;
var formattable = value as IFormattable;
if (formattable != null)
{
stringData = formattable.ToString(null, CultureInfo.InvariantCulture);
}
else if (value != null)
{
stringData = value.ToString();
}
else
{
stringData = "";
}
var dataToHash = Encoding.UTF8.GetBytes(stringData);
return ComputeHash(dataToHash, hashAlgorithmName);
}
private static byte[] ComputeHash(byte[] value, string hashAlgorithmName)
{
#if HAVE_HASH_ALGORITHMS
using (var hashAlgorithm = CreateHashAlgorithm(hashAlgorithmName))
{
return hashAlgorithm.ComputeHash(value);
}
#else
switch (hashAlgorithmName)
{
case "SHA1": return SHA1.ComputeHash(value);
case "MD5": return MD5.ComputeHash(value);
default: throw new ArgumentException($"Unknown hash algorithm '{hashAlgorithmName}'.", nameof(hashAlgorithmName));
}
#endif
}
#if HAVE_HASH_ALGORITHMS
private static HashAlgorithm CreateHashAlgorithm(string name)
{
#if HAVE_CRYPTO_CONFIG
var obj = CryptoConfig.CreateFromName(name);
var hashAlgorithm = obj as HashAlgorithm;
if (hashAlgorithm != null)
{
return hashAlgorithm;
}
var disposable = obj as IDisposable;
if (disposable != null)
{
disposable.Dispose();
}
#else
switch (name)
{
case "SHA1": return SHA1.Create();
case "MD5": return MD5.Create();
case "SHA256": return SHA256.Create();
case "SHA384": return SHA384.Create();
case "SHA512": return SHA512.Create();
}
#endif
throw new ArgumentException($"Unknown hash algorithm '{name}'.", nameof(name));
}
#endif
}
}