From 1b00fa74bcbabdf4e854a660fd92788496b08143 Mon Sep 17 00:00:00 2001
From: David Montesinos <mdmontesinos@hotmail.com>
Date: Mon, 21 Apr 2025 11:14:24 +0200
Subject: [PATCH] Compute file server etag with MD5 and always include
 ModifiedOn

---
 Oqtane.Server/Pages/Files.cshtml.cs | 10 +++++-----
 Oqtane.Shared/Shared/Utilities.cs   |  8 ++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/Oqtane.Server/Pages/Files.cshtml.cs b/Oqtane.Server/Pages/Files.cshtml.cs
index 97fc2c57..7be27e89 100644
--- a/Oqtane.Server/Pages/Files.cshtml.cs
+++ b/Oqtane.Server/Pages/Files.cshtml.cs
@@ -137,15 +137,15 @@ namespace Oqtane.Pages
             string downloadName = file.Name;
             string filepath = _files.GetFilePath(file);
 
+            var etagInput = $"{file.ModifiedOn.Ticks}:{file.Size}";
+
             if (Request.QueryString.HasValue)
             {
-                etag = Utilities.GenerateSimpleHash(Request.QueryString.Value);
-            }
-            else
-            {
-                etag = Convert.ToString(file.ModifiedOn.Ticks ^ file.Size, 16);
+                etagInput += $":{Request.QueryString.Value}";
             }
 
+            etag = Utilities.GenerateHashMD5(etagInput);
+
             var header = "";
             if (HttpContext.Request.Headers.TryGetValue(HeaderNames.IfNoneMatch, out var ifNoneMatch))
             {
diff --git a/Oqtane.Shared/Shared/Utilities.cs b/Oqtane.Shared/Shared/Utilities.cs
index 826fac70..d38fe490 100644
--- a/Oqtane.Shared/Shared/Utilities.cs
+++ b/Oqtane.Shared/Shared/Utilities.cs
@@ -5,6 +5,7 @@ using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Net;
+using System.Security.Cryptography;
 using System.Text;
 using System.Text.RegularExpressions;
 using File = Oqtane.Models.File;
@@ -619,6 +620,13 @@ namespace Oqtane.Shared
             }
         }
 
+        public static string GenerateHashMD5(string input)
+        {
+            var bytes = Encoding.UTF8.GetBytes(input);
+            var hashBytes = MD5.HashData(bytes);
+            return Convert.ToHexString(hashBytes);
+        }
+
         [Obsolete("ContentUrl(Alias alias, int fileId) is deprecated. Use FileUrl(Alias alias, int fileId) instead.", false)]
         public static string ContentUrl(Alias alias, int fileId)
         {