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Copy pathKerberosUsernameProvider.cs
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112 lines (98 loc) · 4 KB
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using System;
using System.Diagnostics;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
namespace Npgsql;
/// <summary>
/// Launches MIT Kerberos klist and parses out the default principal from it.
/// Caches the result.
/// </summary>
static class KerberosUsernameProvider
{
static volatile bool _performedDetection;
static string? _principalWithRealm;
static string? _principalWithoutRealm;
internal static ValueTask<string?> GetUsername(bool async, bool includeRealm, ILogger connectionLogger, CancellationToken cancellationToken)
{
if (_performedDetection)
return new(includeRealm ? _principalWithRealm : _principalWithoutRealm);
var klistPath = FindInPath("klist");
if (klistPath == null)
{
connectionLogger.LogDebug("klist not found in PATH, skipping Kerberos username detection");
return new((string?)null);
}
var processStartInfo = new ProcessStartInfo
{
FileName = klistPath,
RedirectStandardOutput = true,
RedirectStandardError = true,
UseShellExecute = false
};
var process = Process.Start(processStartInfo);
if (process is null)
{
connectionLogger.LogDebug("klist process could not be started");
return new((string?)null);
}
return GetUsernameAsyncInternal();
async ValueTask<string?> GetUsernameAsyncInternal()
{
if (async)
await process.WaitForExitAsync(cancellationToken).ConfigureAwait(false);
else
// ReSharper disable once MethodHasAsyncOverloadWithCancellation
process.WaitForExit();
if (process.ExitCode != 0)
{
connectionLogger.LogDebug($"klist exited with code {process.ExitCode}: {process.StandardError.ReadToEnd()}");
return null;
}
var line = default(string);
for (var i = 0; i < 2; i++)
// ReSharper disable once MethodHasAsyncOverload
if ((line = async ? await process.StandardOutput.ReadLineAsync(cancellationToken).ConfigureAwait(false) : process.StandardOutput.ReadLine()) == null)
{
connectionLogger.LogDebug("Unexpected output from klist, aborting Kerberos username detection");
return null;
}
return ParseKListOutput(line!, includeRealm, connectionLogger);
}
}
static string? ParseKListOutput(string line, bool includeRealm, ILogger connectionLogger)
{
var colonIndex = line.IndexOf(':');
var colonLastIndex = line.LastIndexOf(':');
if (colonIndex == -1 || colonIndex != colonLastIndex)
{
connectionLogger.LogDebug("Unexpected output from klist, aborting Kerberos username detection");
return null;
}
var secondPart = line.AsSpan(1 + line.IndexOf(':'));
var principalWithRealm = secondPart.Trim();
var atIndex = principalWithRealm.IndexOf('@');
var atLastIndex = principalWithRealm.LastIndexOf('@');
if (atIndex == -1 || atIndex != atLastIndex)
{
connectionLogger.LogDebug(
$"Badly-formed default principal {principalWithRealm.ToString()} from klist, aborting Kerberos username detection");
return null;
}
_principalWithRealm = principalWithRealm.ToString();
_principalWithoutRealm = principalWithRealm.Slice(0, atIndex).ToString();
_performedDetection = true;
return includeRealm ? _principalWithRealm : _principalWithoutRealm;
}
static string? FindInPath(string name)
{
foreach (var p in Environment.GetEnvironmentVariable("PATH")?.Split(Path.PathSeparator) ?? [])
{
var path = Path.Combine(p, name);
if (File.Exists(path))
return path;
}
return null;
}
}