diff --git a/stratosphere/ams_mitm/source/fs_mitm/fs_file_storage.cpp b/stratosphere/ams_mitm/source/fs_mitm/fs_file_storage.cpp
new file mode 100644
index 000000000..f4e154f7d
--- /dev/null
+++ b/stratosphere/ams_mitm/source/fs_mitm/fs_file_storage.cpp
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2018-2019 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <cstring>
+#include <switch.h>
+#include <stratosphere.hpp>
+
+#include "../utils.hpp"
+#include "fs_file_storage.hpp"
+
+Result FileStorage::UpdateSize() {
+    if (this->size == InvalidSize) {
+        return this->file->GetSize(&this->size);
+    }
+    return ResultSuccess;
+}
+
+Result FileStorage::Read(void *buffer, size_t size, u64 offset) {
+    Result rc;
+    u64 read_size;
+
+    if (size == 0) {
+        return ResultSuccess;
+    }
+    if (buffer == nullptr) {
+        return ResultFsNullptrArgument;
+    }
+    if (R_FAILED((rc = this->UpdateSize()))) {
+        return rc;
+    }
+    if (!IStorage::IsRangeValid(offset, size, this->size)) {
+        return ResultFsOutOfRange;
+    }
+
+    return this->file->Read(&read_size, offset, buffer, size);
+}
+
+Result FileStorage::Write(void *buffer, size_t size, u64 offset) {
+    Result rc;
+
+    if (size == 0) {
+        return ResultSuccess;
+    }
+    if (buffer == nullptr) {
+        return ResultFsNullptrArgument;
+    }
+    if (R_FAILED((rc = this->UpdateSize()))) {
+        return rc;
+    }
+    if (!IStorage::IsRangeValid(offset, size, this->size)) {
+        return ResultFsOutOfRange;
+    }
+
+    return this->file->Write(offset, buffer, size);
+}
+
+Result FileStorage::Flush() {
+    return this->file->Flush();
+}
+
+Result FileStorage::GetSize(u64 *out_size) {
+    Result rc = this->UpdateSize();
+    if (R_FAILED(rc)) {
+        return rc;
+    }
+    *out_size = this->size;
+    return ResultSuccess;
+}
+
+Result FileStorage::SetSize(u64 size) {
+    this->size = InvalidSize;
+    return this->file->SetSize(size);
+}
+
+Result FileStorage::OperateRange(u32 operation_type, u64 offset, u64 size, FsRangeInfo *out_range_info) {
+    Result rc;
+
+    switch (operation_type) {
+        case 2: /* TODO: OperationType_Invalidate */
+        case 3: /* TODO: OperationType_Query */
+            if (size == 0) {
+                if (operation_type == 3) {
+                    if (out_range_info == nullptr) {
+                        return ResultFsNullptrArgument;
+                    }
+                    /* N checks for size == sizeof(*out_range_info) here, but that's because their wrapper api is bad. */
+                    std::memset(out_range_info, 0, sizeof(*out_range_info));
+                }
+                return ResultSuccess;
+            }
+            if (R_FAILED((rc = this->UpdateSize()))) {
+                return rc;
+            }
+            /* N checks for positivity + signed overflow on offset/size here, but we're using unsigned types... */
+            return this->file->OperateRange(operation_type, offset, size, out_range_info);
+        default:
+            return ResultFsUnsupportedOperation;
+    }
+}
\ No newline at end of file
diff --git a/stratosphere/ams_mitm/source/fs_mitm/fs_file_storage.hpp b/stratosphere/ams_mitm/source/fs_mitm/fs_file_storage.hpp
new file mode 100644
index 000000000..6b21383e4
--- /dev/null
+++ b/stratosphere/ams_mitm/source/fs_mitm/fs_file_storage.hpp
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2018-2019 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+ 
+#pragma once
+#include <switch.h>
+#include <stratosphere.hpp>
+#include "fs_shim.h"
+
+#include "../debug.hpp"
+#include "fs_istorage.hpp"
+#include "fs_ifile.hpp"
+
+class FileStorage : public IStorage {
+    public:
+        static constexpr u64 InvalidSize = UINT64_MAX;
+    private:
+        std::shared_ptr<IFile> base_file;
+        IFile *file;
+        u64 size;
+    public:
+        FileStorage(IFile *f) : base_file(f) {
+            this->file = this->base_file.get();
+            this->size = InvalidSize;
+        };
+        FileStorage(std::shared_ptr<IFile> f) : base_file(f) {
+            this->file = this->base_file.get();
+            this->size = InvalidSize;
+        };
+        virtual ~FileStorage() {
+            /* ... */
+        };
+    protected:
+        Result UpdateSize();
+    public:
+        virtual Result Read(void *buffer, size_t size, u64 offset) override;
+        virtual Result Write(void *buffer, size_t size, u64 offset) override;
+        virtual Result Flush() override;
+        virtual Result GetSize(u64 *out_size) override;
+        virtual Result SetSize(u64 size) override;
+        virtual Result OperateRange(u32 operation_type, u64 offset, u64 size, FsRangeInfo *out_range_info) override;
+};