79 lines
3.2 KiB
C#
79 lines
3.2 KiB
C#
using System;
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using System.Collections;
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using System.Linq;
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using System.Net.Sockets;
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namespace Content.Server.IP
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{
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public static class IPAddressExt
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{
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// Taken from https://stackoverflow.com/a/56461160/4678631
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public static bool IsInSubnet(this System.Net.IPAddress address, string subnetMask)
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{
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var slashIdx = subnetMask.IndexOf("/", StringComparison.Ordinal);
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if (slashIdx == -1)
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{
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// We only handle netmasks in format "IP/PrefixLength".
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throw new NotSupportedException("Only SubNetMasks with a given prefix length are supported.");
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}
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// First parse the address of the netmask before the prefix length.
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var maskAddress = System.Net.IPAddress.Parse(subnetMask.Substring(0, slashIdx));
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if (maskAddress.AddressFamily != address.AddressFamily)
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{
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// We got something like an IPV4-Address for an IPv6-Mask. This is not valid.
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return false;
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}
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// Now find out how long the prefix is.
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int maskLength = int.Parse(subnetMask.Substring(slashIdx + 1));
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if (maskAddress.AddressFamily == AddressFamily.InterNetwork)
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{
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// Convert the mask address to an unsigned integer.
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var maskAddressBits = BitConverter.ToUInt32(maskAddress.GetAddressBytes().Reverse().ToArray(), 0);
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// And convert the IpAddress to an unsigned integer.
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var ipAddressBits = BitConverter.ToUInt32(address.GetAddressBytes().Reverse().ToArray(), 0);
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// Get the mask/network address as unsigned integer.
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uint mask = uint.MaxValue << (32 - maskLength);
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// https://stackoverflow.com/a/1499284/3085985
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// Bitwise AND mask and MaskAddress, this should be the same as mask and IpAddress
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// as the end of the mask is 0000 which leads to both addresses to end with 0000
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// and to start with the prefix.
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return (maskAddressBits & mask) == (ipAddressBits & mask);
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}
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if (maskAddress.AddressFamily == AddressFamily.InterNetworkV6)
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{
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// Convert the mask address to a BitArray.
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var maskAddressBits = new BitArray(maskAddress.GetAddressBytes());
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// And convert the IpAddress to a BitArray.
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var ipAddressBits = new BitArray(address.GetAddressBytes());
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if (maskAddressBits.Length != ipAddressBits.Length)
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{
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throw new ArgumentException("Length of IP Address and Subnet Mask do not match.");
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}
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// Compare the prefix bits.
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for (int maskIndex = 0; maskIndex < maskLength; maskIndex++)
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{
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if (ipAddressBits[maskIndex] != maskAddressBits[maskIndex])
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{
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return false;
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}
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}
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return true;
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}
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throw new NotSupportedException("Only InterNetworkV6 or InterNetwork address families are supported.");
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}
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}
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}
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