fix(installer): stop granting Users read access to the data folder

package/WindowsManaged.UnitTests/DataFolderTests.cs

@@ -441,6 +441,32 @@ public void OnlySystemAdministratorsAndTheServiceAccountCanChangeTheData(string
         Assert.Equal(expected, writers);
     }
 
+    [Theory]
+    // oracle: mutant an entry that lets Users or another account read the data folder or what it passes on
+    [InlineData("the data folder")]
+    // oracle: mutant an entry that lets Users or another account read the users database
+    [InlineData("the users database")]
+    public void OnlySystemAdministratorsAndTheServiceAccountCanReadTheData(string template)
+    {
+        SecurityIdentifier service = new("S-1-5-80-1-2-3-4-5");
+        RawSecurityDescriptor descriptor = new(Templates[template](service));
+        // Reading a file's content, including through a generic right.
+        const int reading = 0x1 | 0x10000000 | unchecked((int)0x80000000);
+
+        string[] readers = descriptor.DiscretionaryAcl
+            .Cast<CommonAce>()
+            .Where(ace => ace.AceQualifier == AceQualifier.AccessAllowed && (ace.AccessMask & reading) != 0)
+            .Select(ace => ace.SecurityIdentifier.Value)
+            .Distinct()
+            .OrderBy(sid => sid, StringComparer.Ordinal)
+            .ToArray();
+        string[] expected = new[] { "S-1-5-18", "S-1-5-32-544", service.Value }
+            .OrderBy(sid => sid, StringComparer.Ordinal)
+            .ToArray();
+
+        Assert.Equal(expected, readers);
+    }
+
     // A service account that is LOCAL SERVICE gets its rights through the service account's entries.
     // oracle: mutant an entry of its own for LOCAL SERVICE, such as read access
     [Theory]

package/WindowsManaged/Resources/Includes.cs

@@ -34,15 +34,14 @@ internal static class Includes
             /// Local System (SY)	Full Access (FA)
             /// Service account	Read, Execute, Write, Delete Subfolders and Files on the folder; also Delete on everything below it
             /// Administrators (BA)	Full Access (FA)
-            /// Users (BU)	Read, Execute
-        /// Only SYSTEM, administrators and the service account can change what the Gateway stores there, so no other
-        /// account gets more than read access.
+        /// Only SYSTEM, administrators and the service account can read or change what the Gateway stores there, because
+        /// it holds session recordings and private keys.
         /// LOCAL SERVICE, which earlier installers gave write access, has no entry, and the installer doesn't accept it as
         /// the service account.
         /// The service account gets no Delete on the folder itself, so that only SYSTEM and administrators can rename or
         /// replace it, while an inherit-only entry gives it Delete on the files and subfolders it manages below.
         /// </remarks>
-        private const string PROGRAM_DATA_SDDL_TEMPLATE = "O:SYG:SYD:PAI(A;OICI;FA;;;SY)(A;OICI;0x1201ff;;;{0})(A;OICIIO;0x1301ff;;;{0})(A;OICI;FA;;;BA)(A;OICI;0x1200a9;;;BU)";
+        private const string PROGRAM_DATA_SDDL_TEMPLATE = "O:SYG:SYD:PAI(A;OICI;FA;;;SY)(A;OICI;0x1201ff;;;{0})(A;OICIIO;0x1301ff;;;{0})(A;OICI;FA;;;BA)";
 
         /// <summary>
         /// SDDL template for the desired %programdata%\devolutions\gateway\users.txt owner and ACL. `{0}` is the SID of the service account.