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DNS Auflösung bei E-Mail Adressen: DNS Client getauscht, BasicAuthenticationHandler implementiert.

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This commit is contained in:
Andreas Müller
2021-12-21 22:26:58 +01:00
parent e5b9959d8e
commit 7a71bd91d5
5 changed files with 120 additions and 33 deletions
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36
AMWD.Common/Extensions/StringExtensions.cs
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@@ -5,7 +5,8 @@ using System.Net;
using System.Net.Mail;
using System.Text;
using System.Text.RegularExpressions;
using DnsClient;
using DNS.Client;
using DNS.Protocol;
namespace System
{
@@ -148,10 +149,10 @@ namespace System
/// You can enhance the check by requesting the MX record of the domain.
/// </remarks>
/// <param name="email">The email address as string to validate.</param>
/// <param name="checkRecordExists">A value indicating whether to resolve a MX record.</param>
/// <param name="checkRecordExists">A value indicating whether to resolve a MX record (Google DNS is used).</param>
/// <returns><c>true</c> when the email address is valid, other wise <c>false</c>.</returns>
public static bool IsValidEmailAddress(this string email, bool checkRecordExists = false)
=> email.IsValidEmailAddress(checkRecordExists ? new LookupClient() : null);
=> email.IsValidEmailAddress(checkRecordExists ? new[] { new IPEndPoint(IPAddress.Parse("8.8.8.8"), 53) } : null);
/// <summary>
/// Checks whether the given <see cref="string"/> is a valid <see cref="MailAddress"/>.
@@ -163,19 +164,36 @@ namespace System
/// <param name="nameservers">A list of <see cref="IPEndPoint"/>s of nameservers.</param>
/// <returns><c>true</c> when the email address is valid, other wise <c>false</c>.</returns>
public static bool IsValidEmailAddress(this string email, IEnumerable<IPEndPoint> nameservers)
=> email.IsValidEmailAddress(new LookupClient(nameservers.ToArray()));
private static bool IsValidEmailAddress(this string email, LookupClient lookupClient)
{
try
{
var mailAddress = new MailAddress(email);
bool isValid = mailAddress.Address == email;
if (isValid && lookupClient != null)
if (isValid && nameservers != null)
{
var result = lookupClient.Query(mailAddress.Host, QueryType.MX);
isValid &= result.Answers.MxRecords().Any();
bool exists = false;
foreach (var nameserver in nameservers)
{
var clientRequest = new ClientRequest(nameserver) { RecursionDesired = true };
clientRequest.Questions.Add(new Question(Domain.FromString(mailAddress.Host), RecordType.MX));
var response = clientRequest.Resolve()
.ConfigureAwait(false)
.GetAwaiter()
.GetResult();
if (response.ResponseCode != ResponseCode.NoError)
continue;
exists = response.AnswerRecords
.Where(r => r.Type == RecordType.MX)
.Any();
break;
}
isValid &= exists;
}
return isValid;