Dictionary<Decimal, xxxx> causes an error #2120
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Error Sample Dictionary<Decimal, String>Reason for the error
Request
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Replies: 2 comments 5 replies
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You can either switch off hash resistance, or implement your own secure hash method for |
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My CustomMessagePackSecurity class and method. using MessagePack;
using System.Collections;
using System.Collections.Generic;
namespace CustomSerialization.MessagePack
{
/// <summary>
/// Custom MessagePackSecurity class
/// </summary>
public class CustomMessagePackSecurity : MessagePackSecurity
{
public static readonly MessagePackSecurity CustomUntrustedData = new CustomMessagePackSecurity(MessagePackSecurity.UntrustedData);
/// <summary>
/// constructor
/// </summary>
/// <param name="copyFrom"></param>
protected CustomMessagePackSecurity(MessagePackSecurity copyFrom) : base(copyFrom)
{
}
/// <summary>
///
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
protected override IEqualityComparer<T> GetHashCollisionResistantEqualityComparer<T>()
{
if (typeof(T) == typeof(decimal))
{
return (IEqualityComparer<T>)DecimalEqualityComparer.Instance;
}
else
{
return base.GetHashCollisionResistantEqualityComparer<T>();
}
}
/// <summary>
/// Decimal Equality Comparer
/// </summary>
private class DecimalEqualityComparer : IEqualityComparer<decimal>, IEqualityComparer
{
internal static readonly DecimalEqualityComparer Instance = new();
public bool Equals(decimal x, decimal y) => EqualityComparer<decimal?>.Default.Equals(x, y);
bool IEqualityComparer.Equals(object? x, object? y) => ((IEqualityComparer)EqualityComparer<decimal>.Default).Equals(x, y);
public int GetHashCode(object obj) => this.GetHashCode((decimal)obj);
public int GetHashCode(decimal value)
{
return value.GetHashCode();
}
}
}
} |
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That isn't a secure (i.e. collision resistant) hash function. That's just using the default, and isn't any better (for this dictionary type anyway) than just turning the secure hash requirement off in the options. But if hash resistance isn't important to you, this is one way to get yourself unblocked, albeit IMO a misleading one that should be very prominently documented so folks understand it isn't secure. |
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Thank you for pointing that out. private class DecimalEqualityComparer : IEqualityComparer<decimal>, IEqualityComparer
{
internal static readonly DecimalEqualityComparer Instance = new();
internal static readonly SipHash SipHashInstance = new();
public bool Equals(decimal x, decimal y) => EqualityComparer<decimal?>.Default.Equals(x, y);
bool IEqualityComparer.Equals(object? x, object? y) => ((IEqualityComparer)EqualityComparer<decimal>.Default).Equals(x, y);
public int GetHashCode(object obj) => this.GetHashCode((decimal)obj);
public int GetHashCode([DisallowNull] decimal obj) => unchecked((int)this.GetSecureHashCode(obj));
private static long SecureHash(ReadOnlySpan<byte> data) => unchecked(SipHashInstance.Compute(data));
public long GetSecureHashCode([DisallowNull] decimal obj)
{
Span<int> bytes = stackalloc int[500];
if (!decimal.TryGetBits(obj, bytes, out int length))
{
throw new NotSupportedException("Decimal too long.");
}
return SecureHash(MemoryMarshal.Cast<int, byte>(bytes[..length]));
}
} |
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Thank you for your answer. |
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Sure. You can either share a link to your implementation as an extension to the library or a PR that adds it to this one, and we can look into incorporating it. |
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Tip: You could find a sample secure decimal hash function here. |
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Thank you for pointing that out.
GetHashCodehas been rewritten to callSipHash.