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Copy pathDnsString.cs
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219 lines (190 loc) · 7.52 KB
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using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
namespace DnsClient
{
/// <summary>
/// The <see cref="DnsString"/> type is used to normalize and validate domain names and labels.
/// </summary>
public class DnsString
{
/// <summary>
/// The ACE prefix indicates that the domain name label contains not normally supported characters and that the label has been encoded.
/// </summary>
public const string ACEPrefix = "xn--";
/// <summary>
/// The maximum length in bytes for one label.
/// </summary>
public const int LabelMaxLength = 63;
/// <summary>
/// The maximum supported total length in bytes for a domain name. The calculation of the actual
/// bytes this <see cref="DnsString"/> consumes includes all bytes used for to encode it as octet string.
/// </summary>
public const int QueryMaxLength = 255;
/// <summary>
/// The root label ".".
/// </summary>
public static readonly DnsString RootLabel = new DnsString(".", ".");
internal static readonly IdnMapping IDN = new IdnMapping();
private const char Dot = '.';
private const string DotStr = ".";
/// <summary>
/// Gets the original value.
/// </summary>
public string Original { get; }
/// <summary>
/// Gets the validated and eventually modified value.
/// </summary>
public string Value { get; }
internal DnsString(string original, string value)
{
Original = original;
Value = value;
}
/// <summary>
/// Performs an implicit conversion from <see cref="DnsString"/> to <see cref="System.String"/>.
/// </summary>
/// <param name="name">The name.</param>
/// <returns>
/// The result of the conversion.
/// </returns>
public static implicit operator string(DnsString name) => name?.Value;
/// <inheritdoc />
public override string ToString()
{
return Value;
}
/// <inheritdoc />
public override int GetHashCode()
{
return Value.GetHashCode();
}
/// <inheritdoc />
public override bool Equals(object obj)
{
if (obj == null)
{
return false;
}
return obj.ToString().Equals(Value);
}
// removed as this is actually the wrong label representation (also, doesn't work if there are escaped \. in the value
/////// <summary>
/////// Returns labels representation of the <see cref="Value"/>.
/////// </summary>
////public IReadOnlyList<string> Labels
////{
//// get
//// {
//// return Value.Split('.').Reverse().Select(p => p + DotStr).ToArray();
//// }
////}
/// <summary>
/// Parses the given <paramref name="query"/> and validates all labels.
/// </summary>
/// <remarks>
/// An empty string will be interpreted as root label.
/// </remarks>
/// <param name="query">A domain name.</param>
/// <returns>The <see cref="DnsString"/> representing the given <paramref name="query"/>.</returns>
/// <exception cref="ArgumentNullException">If <paramref name="query"/> is null.</exception>
public static DnsString Parse(string query)
{
if (query == null)
{
throw new ArgumentNullException(nameof(query));
}
int charCount = 0;
int labelCharCount = 0;
int labelsCount = 0;
if (query.Length > 1 && query[0] == Dot)
{
throw new ArgumentException($"'{query}' is not a legal name, found leading root label.", nameof(query));
}
if (query.Length == 0 || (query.Length == 1 && query.Equals(DotStr)))
{
return RootLabel;
}
for (int index = 0; index < query.Length; index++)
{
var c = query[index];
if (c == Dot)
{
if (labelCharCount > LabelMaxLength)
{
throw new ArgumentException($"Label '{labelsCount + 1}' is longer than {LabelMaxLength} bytes.", nameof(query));
}
labelsCount++;
labelCharCount = 0;
}
else
{
labelCharCount++;
charCount++;
if (!(c == '-' || c == '_' ||
c >= 'a' && c <= 'z' ||
c >= 'A' && c <= 'Z' ||
c >= '0' && c <= '9'))
{
try
{
var result = IDN.GetAscii(query);
if (result[result.Length - 1] != Dot)
{
result += Dot;
}
return new DnsString(query, result);
}
catch (Exception ex)
{
throw new ArgumentException($"'{query}' is not a valid hostname.", nameof(query), ex);
}
}
}
}
// check rest
if (labelCharCount > 0)
{
labelsCount++;
// check again label max length
if (labelCharCount > LabelMaxLength)
{
throw new ArgumentException($"Label '{labelsCount}' is longer than {LabelMaxLength} bytes.", nameof(query));
}
}
// octets length bit per label + 2(start +end)
if (charCount + labelsCount + 1 > QueryMaxLength)
{
throw new ArgumentException($"Octet length of '{query}' exceeds maximum of {QueryMaxLength} bytes.", nameof(query));
}
if (query[query.Length - 1] != Dot)
{
return new DnsString(query, query + Dot);
}
return new DnsString(query, query);
}
/// <summary>
/// Transforms names with the <see cref="ACEPrefix"/> to the Unicode variant and adds a trailing '.' at the end if not present.
/// The original value will be kept in this instance in case it is needed.
/// </summary>
/// <remarks>
/// The method does not parse the domain name unless it contains a <see cref="ACEPrefix"/>.
/// </remarks>
/// <param name="query">The value to check.</param>
/// <returns>The <see cref="DnsString"/> representation.</returns>
public static DnsString FromResponseQueryString(string query)
{
if (query.Length == 0 || query[query.Length - 1] != Dot)
{
query += DotStr;
}
if (query.Contains(ACEPrefix))
{
var unicode = IDN.GetUnicode(query);
return new DnsString(unicode, query);
}
return new DnsString(query, query);
}
}
}