Merged PR 668400: [vs17.14] Recreate temp on linux using CreateTempSubdirectory on every build

Recreate temp on linux using CreateTempSubdirectory on every build

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#### AI description  (iteration 1)
#### PR Classification
Security bug fix that improves the creation of the temporary folder on Linux to prevent potential malicious folder hijacking.

#### PR Summary
This PR replaces the custom logic for creating and validating the MSBuild temporary folder on Linux with the built-in Directory.CreateTempSubdirectory method, ensuring a fresh and securely generated temp directory on every build.
- `src/Shared/TempFileUtilities.cs`: Updated the Linux branch in the CreateFolderUnderTemp method to use Directory.CreateTempSubdirectory instead of manually handling mkdir/chmod and username concatenation.
- `src/Shared/TempFileUtilities.cs`: Removed the custom permission logic and the unused `userRWX` constant, simplifying the directory creation for non-Linux platforms.
<!-- GitOpsUserAgent=GitOps.Apps.Server.pullrequestcopilot -->

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#### AI description  (iteration 2)
#### PR Classification
This pull request is a security bug fix addressing a vulnerability in how MSBuild creates its temporary folder on Linux.

#### PR Summary
The PR improves the security of temp folder creation by replacing custom mkdir/chmod logic with the built-in `Directory.CreateTempSubdirectory` on Linux, ensuring a uniquely created directory for each build. Additionally, it removes redundant permission code in `TempFileUtilities.cs` and bumps the version in `eng/Versions.props` from 17.14.27 to 17.14.28.
- `src/Shared/TempFileUtilities.cs`: Replaces manual Linux temp folder creation with `Directory.CreateTempSubdirectory` and eliminates outdated permission checks.
- `eng/Versions.props`: Updates the version prefix to signal the new release.

Related work items: #2541147

Author: JanProvaznik

eng/Versions.props

@@ -2,13 +2,13 @@
 <!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the MIT license. See License.txt in the project root for full license information. -->
 <Project>
   <PropertyGroup>
-    <VersionPrefix>17.14.27</VersionPrefix>
+    <VersionPrefix>17.14.28</VersionPrefix>
     <DotNetFinalVersionKind>release</DotNetFinalVersionKind>
     <PackageValidationBaselineVersion>17.13.9</PackageValidationBaselineVersion>
     <AssemblyVersion>15.1.0.0</AssemblyVersion>
     <PreReleaseVersionLabel>servicing</PreReleaseVersionLabel>
 
-    <!-- differentiate experimental insertions to avoid package id conflicts, 
+    <!-- differentiate experimental insertions to avoid package id conflicts,
     it has to be alphabetically after "preview" to avoid downgrade errors in VS -->
     <PreReleaseVersionLabel Condition="'$(IsExperimental)' == 'true'">test</PreReleaseVersionLabel>
 

src/Shared/TempFileUtilities.cs

@@ -18,7 +18,6 @@ internal static partial class FileUtilities
     {
         // For the current user, these correspond to read, write, and execute permissions.
         // Lower order bits correspond to the same for "group" or "other" users.
-        private const int userRWX = 0x100 | 0x80 | 0x40;
         private static string tempFileDirectory = null;
         private const string msbuildTempFolderPrefix = "MSBuildTemp";
 
@@ -38,40 +37,21 @@ internal static void ClearTempFileDirectory()
         // For all native calls, directly check their return values to prevent bad actors from getting in between checking if a directory exists and returning it.
         private static string CreateFolderUnderTemp()
         {
-            // On windows Username with Unicode chars can give issues, so we dont append username to the temp folder name.
-            string msbuildTempFolder = NativeMethodsShared.IsWindows ?
-                msbuildTempFolderPrefix :
-                msbuildTempFolderPrefix + Environment.UserName;
+            string path = null;
 
-            string basePath = Path.Combine(Path.GetTempPath(), msbuildTempFolder);
-
-            if (NativeMethodsShared.IsLinux && NativeMethodsShared.mkdir(basePath, userRWX) != 0)
+            if (NativeMethodsShared.IsLinux)
             {
-                if (NativeMethodsShared.chmod(basePath, userRWX) == 0)
-                {
-                    // Current user owns this file; we can read and write to it. It is reasonable here to assume it was created properly by MSBuild and can be used
-                    // for temporary files.
-                }
-                else
-                {
-                    // Another user created a folder pretending to be us! Find a folder we can actually use.
-                    int extraBits = 0;
-                    string pathToCheck = basePath + extraBits;
-                    while (NativeMethodsShared.mkdir(pathToCheck, userRWX) != 0 && NativeMethodsShared.chmod(pathToCheck, userRWX) != 0)
-                    {
-                        extraBits++;
-                        pathToCheck = basePath + extraBits;
-                    }
-
-                    basePath = pathToCheck;
-                }
+#if NET // always true, Linux implies NET
+                path = Directory.CreateTempSubdirectory(msbuildTempFolderPrefix).FullName;
+#endif
             }
             else
             {
-                Directory.CreateDirectory(basePath);
+                path = Path.Combine(Path.GetTempPath(), msbuildTempFolderPrefix);
+                Directory.CreateDirectory(path);
             }
 
-            return FileUtilities.EnsureTrailingSlash(basePath);
+            return FileUtilities.EnsureTrailingSlash(path);
         }
 
         /// <summary>