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Add DNS-based domain/DC auto-discovery

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mikisoq
2026-07-29 01:56:08 -01:00
parent e6c67ec2b1
commit b953b3f84a
5 changed files with 335 additions and 1 deletions
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ADBulkTool.csproj
+1
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@@ -13,5 +13,6 @@
<PackageReference Include="Avalonia.Fonts.Inter" Version="12.0.5" />
<PackageReference Include="CsvHelper" Version="33.1.0" />
<PackageReference Include="Novell.Directory.Ldap.NETStandard" Version="4.0.0" />
<PackageReference Include="DnsClient" Version="1.8.0" />
</ItemGroup>
</Project>
MainWindow.axaml
+4 -1
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@@ -18,7 +18,10 @@
<Grid ColumnDefinitions="*,90,130,210" RowDefinitions="Auto,Auto,Auto,Auto" ColumnSpacing="10" RowSpacing="8">
<StackPanel Grid.Row="0" Grid.Column="0">
<TextBlock Text="Domain controller / LDAP host" />
<TextBox x:Name="LdapHostBox" PlaceholderText="dc01.contoso.local" />
<Grid ColumnDefinitions="*,Auto" ColumnSpacing="6">
<TextBox x:Name="LdapHostBox" PlaceholderText="dc01.contoso.local" />
<Button Grid.Column="1" x:Name="DiscoverButton" Content="Discover" Click="Discover_Click" />
</Grid>
</StackPanel>
<StackPanel Grid.Row="0" Grid.Column="1">
MainWindow.axaml.cs
+68
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@@ -29,6 +29,74 @@ public partial class MainWindow : Window
RefreshConnectionHelp();
RefreshActionHelp();
_ = AutoDiscoverAsync();
}
private async void Discover_Click(object? sender, RoutedEventArgs e)
{
DiscoverButton.IsEnabled = false;
SetStatus("Discovering domain and domain controller from DNS...");
try
{
var result = await DomainDiscovery.DiscoverAsync(TimeSpan.FromSeconds(10));
if (result.LdapHost is not null)
{
LdapHostBox.Text = result.LdapHost;
}
if (result.SearchBaseDn is not null)
{
SearchBaseBox.Text = result.SearchBaseDn;
}
if (result.Domain is not null)
{
var domainUpper = result.Domain.ToUpperInvariant();
var domainParts = result.Domain.Split('.');
var netbios = domainParts.Length > 0 ? domainParts[0].ToUpperInvariant() : domainUpper;
var userPlaceholder = $@"{netbios}\adminuser or adminuser@{result.Domain}";
BindUserBox.PlaceholderText = userPlaceholder;
}
SetStatus(result.Message ?? "Discovery did not return a result.");
}
catch (Exception ex)
{
SetStatus($"Discovery failed: {ex.Message}");
}
finally
{
DiscoverButton.IsEnabled = true;
}
}
private async Task AutoDiscoverAsync()
{
try
{
var result = await DomainDiscovery.DiscoverAsync(TimeSpan.FromSeconds(5));
if (result.LdapHost is not null && string.IsNullOrWhiteSpace(LdapHostBox.Text))
{
LdapHostBox.Text = result.LdapHost;
}
if (result.SearchBaseDn is not null && string.IsNullOrWhiteSpace(SearchBaseBox.Text))
{
SearchBaseBox.Text = result.SearchBaseDn;
}
if (result.LdapHost is not null || result.SearchBaseDn is not null)
{
SetStatus("Auto-discovered AD domain from DNS. Adjust if needed, then enter credentials.");
}
}
catch
{
}
}
private async void LoadCsv_Click(object? sender, RoutedEventArgs e)
Models/DiscoveryResult.cs
+9
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@@ -0,0 +1,9 @@
namespace ADBulkTool.Models;
public sealed record DiscoveryResult(
string? Domain,
string? DnsServer,
string? LdapHost,
int? LdapPort,
string? SearchBaseDn,
string? Message);
Services/DomainDiscovery.cs
+253
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@@ -0,0 +1,253 @@
using System.Net;
using ADBulkTool.Models;
using DnsClient;
namespace ADBulkTool.Services;
public static class DomainDiscovery
{
public static async Task<DiscoveryResult> DiscoverAsync(TimeSpan timeout)
{
var steps = new List<string>();
try
{
var domain = await GetSystemDomainAsync(timeout);
if (string.IsNullOrWhiteSpace(domain))
{
return new DiscoveryResult(null, null, null, null, null,
"Could not detect a DNS domain from this machine. Check that you are on a domain-joined network and that /etc/resolv.conf has a search or domain entry.");
}
steps.Add($"Detected domain: {domain}");
var searchBase = DomainToSearchBase(domain);
steps.Add($"Derived search base: {searchBase}");
var dnsServers = GetDnsServers();
var dnsServer = dnsServers.FirstOrDefault();
steps.Add(dnsServer is not null
? $"DNS server from /etc/resolv.conf: {dnsServer}"
: "No DNS server found in /etc/resolv.conf, using system default.");
var ldapHost = await FindDomainControllerViaSrvAsync(domain, dnsServer, timeout);
if (ldapHost is not null)
{
steps.Add($"Found DC via SRV record: {ldapHost}");
return new DiscoveryResult(domain, dnsServer, ldapHost, 636, searchBase,
string.Join(" | ", steps));
}
ldapHost = await FindDomainControllerViaLdapSrvAsync(domain, dnsServer, timeout);
if (ldapHost is not null)
{
steps.Add($"Found DC via generic LDAP SRV: {ldapHost}");
return new DiscoveryResult(domain, dnsServer, ldapHost, 636, searchBase,
string.Join(" | ", steps));
}
var guessedHost = $"dc01.{domain}";
steps.Add($"SRV lookup failed. Guessed DC: {guessedHost}");
return new DiscoveryResult(domain, dnsServer, guessedHost, 636, searchBase,
string.Join(" | ", steps));
}
catch (Exception ex)
{
return new DiscoveryResult(null, null, null, null, null,
$"Discovery failed: {ex.Message}");
}
}
public static List<string> GetDnsServers()
{
var servers = new List<string>();
try
{
var lines = File.ReadAllLines("/etc/resolv.conf");
foreach (var line in lines)
{
var trimmed = line.Trim();
if (trimmed.StartsWith("nameserver ", StringComparison.OrdinalIgnoreCase))
{
var parts = trimmed.Split(' ', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
if (parts.Length >= 2 && IPAddress.TryParse(parts[1], out _))
{
servers.Add(parts[1]);
}
}
}
}
catch
{
}
return servers;
}
public static string? DomainToSearchBase(string? domain)
{
if (string.IsNullOrWhiteSpace(domain))
{
return null;
}
var parts = domain.Split('.', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
if (parts.Length == 0)
{
return null;
}
return string.Join(",", parts.Select(p => $"DC={p}"));
}
private static async Task<string?> GetSystemDomainAsync(TimeSpan timeout)
{
try
{
using var cts = new CancellationTokenSource(timeout);
var resolvDomain = await Task.Run(() => GetDomainFromResolvConf(), cts.Token);
if (!string.IsNullOrWhiteSpace(resolvDomain))
{
return resolvDomain;
}
var hostDomain = await Task.Run(() => GetDomainFromHostname(), cts.Token);
if (!string.IsNullOrWhiteSpace(hostDomain))
{
return hostDomain;
}
var ipDomain = await Task.Run(() =>
{
try { return System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().DomainName; }
catch { return string.Empty; }
}, cts.Token);
if (!string.IsNullOrWhiteSpace(ipDomain) && !string.Equals(ipDomain, "localdomain", StringComparison.OrdinalIgnoreCase))
{
return ipDomain.TrimEnd('.');
}
return null;
}
catch
{
return null;
}
}
private static string? GetDomainFromResolvConf()
{
try
{
var lines = File.ReadAllLines("/etc/resolv.conf");
foreach (var line in lines)
{
var trimmed = line.Trim();
if (trimmed.StartsWith("domain ", StringComparison.OrdinalIgnoreCase))
{
var parts = trimmed.Split(' ', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
if (parts.Length >= 2 && !string.IsNullOrWhiteSpace(parts[1]))
{
return parts[1].TrimEnd('.');
}
}
if (trimmed.StartsWith("search ", StringComparison.OrdinalIgnoreCase))
{
var parts = trimmed.Split(' ', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
if (parts.Length >= 2 && !string.IsNullOrWhiteSpace(parts[1]))
{
return parts[1].TrimEnd('.');
}
}
}
}
catch
{
}
return null;
}
private static string? GetDomainFromHostname()
{
try
{
var hostname = Dns.GetHostEntry("localhost").HostName;
var dotIndex = hostname.IndexOf('.');
if (dotIndex > 0 && dotIndex < hostname.Length - 1)
{
var domain = hostname[(dotIndex + 1)..].TrimEnd('.');
return string.IsNullOrWhiteSpace(domain) ? null : domain;
}
}
catch
{
}
try
{
var fullHostname = System.Net.NetworkInformation.IPGlobalProperties.GetIPGlobalProperties().HostName;
var dotIndex = fullHostname.IndexOf('.');
if (dotIndex > 0 && dotIndex < fullHostname.Length - 1)
{
var domain = fullHostname[(dotIndex + 1)..].TrimEnd('.');
return string.IsNullOrWhiteSpace(domain) ? null : domain;
}
}
catch
{
}
return null;
}
private static async Task<string?> FindDomainControllerViaSrvAsync(string domain, string? dnsServer, TimeSpan timeout)
{
try
{
var srvQuery = $"_ldap._tcp.dc._msdcs.{domain}";
var lookup = CreateLookup(dnsServer);
using var cts = new CancellationTokenSource(timeout);
var result = await lookup.QueryAsync(srvQuery, QueryType.SRV, QueryClass.IN, cts.Token);
var record = result.Answers.SrvRecords().FirstOrDefault();
return record?.DomainName.Value.TrimEnd('.');
}
catch
{
return null;
}
}
private static async Task<string?> FindDomainControllerViaLdapSrvAsync(string domain, string? dnsServer, TimeSpan timeout)
{
try
{
var srvQuery = $"_ldap._tcp.{domain}";
var lookup = CreateLookup(dnsServer);
using var cts = new CancellationTokenSource(timeout);
var result = await lookup.QueryAsync(srvQuery, QueryType.SRV, QueryClass.IN, cts.Token);
var record = result.Answers.SrvRecords().FirstOrDefault();
return record?.DomainName.Value.TrimEnd('.');
}
catch
{
return null;
}
}
private static LookupClient CreateLookup(string? dnsServer)
{
if (dnsServer is not null && IPAddress.TryParse(dnsServer, out var ip))
{
return new LookupClient(new LookupClientOptions(ip) { UseCache = false, Timeout = TimeSpan.FromSeconds(5) });
}
return new LookupClient(new LookupClientOptions { UseCache = false, Timeout = TimeSpan.FromSeconds(5) });
}
}