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duplicati/Duplicati/Library/Common/IO/Util.cs
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219 lines
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C#

// Copyright (C) 2026, The Duplicati Team
// https://duplicati.com, hello@duplicati.com
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
using System.Collections.Generic;
using System.IO;
using Duplicati.Library.Logging;
#nullable enable
namespace Duplicati.Library.Common.IO
{
public static class Util
{
/// <summary>
/// The log tag for messages
/// </summary>
private static readonly string LOGTAG = Log.LogTagFromType(typeof(Util));
/// <summary>
/// A cached instance of the directory separator as a string
/// </summary>
public static readonly string DirectorySeparatorString = Path.DirectorySeparatorChar.ToString();
/// <summary>
/// A cached instance of the alternate directory separator as a string
/// </summary>
public static readonly string AltDirectorySeparatorString = Path.AltDirectorySeparatorChar.ToString();
/// <summary>
/// Filename of a marker file that can be put inside the data folder to prevent Duplicati from fixing lax permissions
/// </summary>
public const string InsecurePermissionsMarkerFile = "insecure-permissions.txt";
/// <summary>
/// Appends the appropriate directory separator to paths, depending on OS.
/// Does not append the separator if the path already ends with it.
/// </summary>
/// <param name="path">The path to append to</param>
/// <returns>The path with the directory separator appended</returns>
public static string AppendDirSeparator(string path)
{
return AppendDirSeparator(path, DirectorySeparatorString);
}
/// <summary>
/// Appends the specified directory separator to paths.
/// Does not append the separator if the path already ends with it.
/// </summary>
/// <param name="path">The path to append to</param>
/// <param name="separator">The directory separator to use</param>
/// <returns>The path with the directory separator appended</returns>
public static string AppendDirSeparator(string path, string separator)
{
return !path.EndsWith(separator, StringComparison.Ordinal) ? path + separator : path;
}
/// <summary>
/// Guesses the directory separator from the path
/// </summary>
/// <param name="path">The path to guess the separator from</param>
/// <returns>The guessed directory separator</returns>
public static string GuessDirSeparator(string? path)
{
return string.IsNullOrWhiteSpace(path) || path.StartsWith("/", StringComparison.Ordinal) ? "/" : "\\";
}
/// <summary>
/// Checks if the path is inside the Windows folder
/// </summary>
/// <param name="path">The path to check</param>
/// <returns><c>true</c> if the path is inside the Windows folder, <c>false</c> otherwise</returns>
public static bool IsPathUnderWindowsFolder(string path)
{
if (!OperatingSystem.IsWindows())
return false;
return path.StartsWith(AppendDirSeparator(Environment.GetFolderPath(Environment.SpecialFolder.Windows)), StringComparison.OrdinalIgnoreCase);
}
/// <summary>
/// Verify that the given path is within the target destination.
/// </summary>
/// <param name="path">The path to verify.</param>
/// <param name="targetDestination">The target destination to verify against.</param>
/// <returns><c>true</c> if the path is inside the target destination, <c>false</c> otherwise.</returns>
public static bool IsPathInsideTarget(string path, string targetDestination)
{
if (string.IsNullOrWhiteSpace(path))
throw new ArgumentNullException(nameof(path));
if (string.IsNullOrWhiteSpace(targetDestination))
throw new ArgumentNullException(nameof(targetDestination));
var fullPath = Path.GetFullPath(path);
var fullTarget = Path.GetFullPath(targetDestination);
// Resolve the target destination once
var realTarget = GetFinalPath(fullTarget);
// Resolve the path of the file/folder we are about to create
var realPath = GetFinalPath(fullPath);
// Normalize both paths to ensure consistent comparison
// This handles cases where paths differ only by trailing separators
var normalizedTarget = realTarget.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
var normalizedPath = realPath.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
// If the paths are equal after normalization, it's valid
if (string.Equals(normalizedPath, normalizedTarget, StringComparison.OrdinalIgnoreCase))
return true;
var relative = Path.GetRelativePath(realTarget, realPath);
if (relative.StartsWith("..") || Path.IsPathRooted(relative))
return false;
return true;
}
/// <summary>
/// Checks if the path is a Windows drive root (e.g., "C:\" or "D:\").
/// </summary>
/// <param name="path">The path to check.</param>
/// <returns><c>true</c> if the path is a drive root, <c>false</c> otherwise.</returns>
private static bool IsDriveRoot(string path)
{
if (!OperatingSystem.IsWindows())
return false;
// GetPathRoot returns "C:\" for "C:\" or "C:\Users"
var root = Path.GetPathRoot(path);
if (string.IsNullOrEmpty(root))
return false;
// Check if the input is exactly the root
return string.Equals(path.TrimEnd('\\'), root.TrimEnd('\\'), StringComparison.OrdinalIgnoreCase)
&& root.EndsWith(Path.DirectorySeparatorChar);
}
/// <summary>
/// Get the final resolved path, accounting for symlinks in existing segments.
/// </summary>
/// <param name="path">The path to resolve.</param>
/// <returns>The fully resolved path, with all symlinks resolved.</returns>
private static string GetFinalPath(string path)
{
if (string.IsNullOrEmpty(path)) return path;
// 1. Separate the Alternate Data Stream suffix if it exists
var basePath = SystemIO.IO_OS.GetAlternateDataStreamParent(path);
var streamSuffix = path.Substring(basePath.Length);
var current = Path.GetFullPath(basePath);
var ghostSegments = new Stack<string>();
// 2. Walk up the tree until we find a segment that exists on disk
while (!Path.Exists(current))
{
var parent = Path.GetDirectoryName(current);
// If we've reached the root and nothing exists (rare/impossible for absolute paths),
// we have to stop and return the original path.
if (string.IsNullOrEmpty(parent) || parent == current)
return path;
// Store the part that doesn't exist so we can put it back later
ghostSegments.Push(Path.GetFileName(current));
current = parent;
}
// 3. Resolve symlinks for the part of the path that actually exists
// Skip symlink resolution for Windows drive roots (e.g., "C:\") as
// ResolveLinkTarget can throw DirectoryNotFoundException on some systems
var resolvedPath = current;
if (!IsDriveRoot(current))
{
FileSystemInfo info = Directory.Exists(current)
? new DirectoryInfo(current)
: new FileInfo(current);
try
{
resolvedPath = info.ResolveLinkTarget(returnFinalTarget: true)?.FullName ?? info.FullName;
}
catch (Exception ex)
{
Log.WriteWarningMessage(LOGTAG, "ResolveLinkTargetFailed", ex, "Failed to resolve link target for {0}, assuming it is not a link", current);
}
}
// 4. Re-attach the non-existent segments to the resolved base path
while (ghostSegments.Count > 0)
resolvedPath = Path.Combine(resolvedPath, ghostSegments.Pop());
// 5. Re-attach the alternate data stream suffix at the very end
return resolvedPath + streamSuffix;
}
}
}