diff --git a/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj b/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj
index f9ba39c9c9b664..f6f39c8cd98532 100644
--- a/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj
+++ b/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj
@@ -57,7 +57,6 @@
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs" Link="Common\Interop\Unix\System.Native\Interop.Errors.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.DeviceFiles.cs" Link="Common\Interop\Unix\System.Native\Interop.DeviceFiles.cs" />
-    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.FChMod.cs" Link="Common\Interop\Unix\System.Native\Interop.FChMod.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetEUid.cs" Link="Common\Interop\Unix\System.Native\Interop.GetEUid.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetPwUid.cs" Link="Common\Interop\Unix\System.Native\Interop.GetPwUid.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetGroupName.cs" Link="Common\Interop\Unix\System.Native\Interop.GetGroupName.cs" />
diff --git a/src/libraries/System.IO.Compression.ZipFile/src/System.IO.Compression.ZipFile.csproj b/src/libraries/System.IO.Compression.ZipFile/src/System.IO.Compression.ZipFile.csproj
index f00f15bf5a4451..3287498e587c16 100644
--- a/src/libraries/System.IO.Compression.ZipFile/src/System.IO.Compression.ZipFile.csproj
+++ b/src/libraries/System.IO.Compression.ZipFile/src/System.IO.Compression.ZipFile.csproj
@@ -31,8 +31,6 @@
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs"
              Link="Common\Interop\Unix\System.Native\Interop.Errors.cs" />
-    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.FChMod.cs"
-             Link="Common\Interop\Unix\System.Native\Interop.FChMod.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Stat.cs"
              Link="Common\Interop\Unix\System.Native\Interop.Stat.cs" />
     <Compile Include="$(CommonPath)System\IO\Archiving.Utils.Unix.cs"
diff --git a/src/libraries/System.IO.Compression.ZipFile/src/System/IO/Compression/ZipFileExtensions.ZipArchiveEntry.Extract.Unix.cs b/src/libraries/System.IO.Compression.ZipFile/src/System/IO/Compression/ZipFileExtensions.ZipArchiveEntry.Extract.Unix.cs
index 1b2d2b365a80c3..adcf474853aa9a 100644
--- a/src/libraries/System.IO.Compression.ZipFile/src/System/IO/Compression/ZipFileExtensions.ZipArchiveEntry.Extract.Unix.cs
+++ b/src/libraries/System.IO.Compression.ZipFile/src/System/IO/Compression/ZipFileExtensions.ZipArchiveEntry.Extract.Unix.cs
@@ -1,12 +1,16 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics;
+
 namespace System.IO.Compression
 {
     public static partial class ZipFileExtensions
     {
         static partial void ExtractExternalAttributes(FileStream fs, ZipArchiveEntry entry)
         {
+            Debug.Assert(!OperatingSystem.IsWindows());
+
             // Only extract USR, GRP, and OTH file permissions, and ignore
             // S_ISUID, S_ISGID, and S_ISVTX bits. This matches unzip's default behavior.
             // It is off by default because of this comment:
@@ -22,9 +26,7 @@ static partial void ExtractExternalAttributes(FileStream fs, ZipArchiveEntry ent
             // include the permissions, or was made on Windows.
             if (permissions != 0)
             {
-#pragma warning disable CA1416 // Validate platform compatibility
                 File.SetUnixFileMode(fs.SafeFileHandle, (UnixFileMode)permissions);
-#pragma warning restore CA1416
             }
         }
     }
diff --git a/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj b/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj
index 1e6345d68b7de1..7035c42d23e123 100644
--- a/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj
+++ b/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj
@@ -39,7 +39,6 @@
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
     <Compile Include="ZipFile.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Interop\Unix\Interop.Libraries.cs" />
-    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.ChMod.cs" Link="Interop\Unix\System.Native\Interop.ChMod.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Stat.cs" Link="Interop\Unix\System.Native\Interop.Stat.cs" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/libraries/System.IO.Compression.ZipFile/tests/ZipFile.Unix.cs b/src/libraries/System.IO.Compression.ZipFile/tests/ZipFile.Unix.cs
index 91b6b4baf5e321..2bca01e0c5c00f 100644
--- a/src/libraries/System.IO.Compression.ZipFile/tests/ZipFile.Unix.cs
+++ b/src/libraries/System.IO.Compression.ZipFile/tests/ZipFile.Unix.cs
@@ -100,7 +100,7 @@ private static string[] CreateFiles(string folderPath, string[] testPermissions)
                 string filename = Path.Combine(folderPath, $"{permissions}.txt");
                 File.WriteAllText(filename, "contents");
 
-                Assert.Equal(0, Interop.Sys.ChMod(filename, Convert.ToInt32(permissions, 8)));
+                File.SetUnixFileMode(filename, (UnixFileMode)Convert.ToInt32(permissions, 8));
 
                 // In some environments, the file mode may be modified by the OS.
                 // See the Rationale section of https://linux.die.net/man/3/chmod.
diff --git a/src/libraries/System.Security.Cryptography.X509Certificates/tests/System.Security.Cryptography.X509Certificates.Tests.csproj b/src/libraries/System.Security.Cryptography.X509Certificates/tests/System.Security.Cryptography.X509Certificates.Tests.csproj
index 611f9b39fbaf64..547a33c182cae6 100644
--- a/src/libraries/System.Security.Cryptography.X509Certificates/tests/System.Security.Cryptography.X509Certificates.Tests.csproj
+++ b/src/libraries/System.Security.Cryptography.X509Certificates/tests/System.Security.Cryptography.X509Certificates.Tests.csproj
@@ -91,8 +91,6 @@
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser' and '$(UseAndroidCrypto)' != 'true' and '$(UseAppleCrypto)' != 'true'">
     <Compile Include="X509FilesystemTests.Unix.cs" />
     <Compile Include="X509StoreTests.Unix.cs" />
-    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.ChMod.cs"
-             Link="Common\Interop\Unix\System.Native\Interop.ChMod.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs"
diff --git a/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj b/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj
index fc436e1c006749..7a65b213dc6f98 100644
--- a/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj
+++ b/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj
@@ -593,8 +593,6 @@
   <ItemGroup Condition="'$(UseOpenSsl)' == 'true'">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs"
              Link="Common\Interop\Unix\Interop.Errors.cs" />
-    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.FChMod.cs"
-             Link="Common\Interop\Unix\System.Native\Interop.FChMod.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetEUid.cs"
              Link="Common\Interop\Unix\System.Native\Interop.GetEUid.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetPwUid.cs"