diff --git a/common/file_fetcher.cc b/common/file_fetcher.cc
new file mode 100644
index 0000000..77dadd1
--- /dev/null
+++ b/common/file_fetcher.cc
@@ -0,0 +1,187 @@
+//
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#include "update_engine/common/file_fetcher.h"
+
+#include <algorithm>
+#include <string>
+
+#include <base/bind.h>
+#include <base/format_macros.h>
+#include <base/location.h>
+#include <base/logging.h>
+#include <base/strings/string_util.h>
+#include <base/strings/stringprintf.h>
+#include <brillo/streams/file_stream.h>
+
+#include "update_engine/common/certificate_checker.h"
+#include "update_engine/common/hardware_interface.h"
+#include "update_engine/common/platform_constants.h"
+
+using std::string;
+
+namespace {
+
+size_t kReadBufferSize = 16 * 1024;
+
+}  // namespace
+
+namespace chromeos_update_engine {
+
+// static
+bool FileFetcher::SupportedUrl(const string& url) {
+  // Note that we require the file path to start with a "/".
+  return base::StartsWith(
+      url, "file:///", base::CompareCase::INSENSITIVE_ASCII);
+}
+
+FileFetcher::~FileFetcher() {
+  LOG_IF(ERROR, transfer_in_progress_)
+      << "Destroying the fetcher while a transfer is in progress.";
+  CleanUp();
+}
+
+// Begins the transfer, which must not have already been started.
+void FileFetcher::BeginTransfer(const string& url) {
+  CHECK(!transfer_in_progress_);
+
+  if (!SupportedUrl(url)) {
+    LOG(ERROR) << "Unsupported file URL: " << url;
+    // No HTTP error code when the URL is not supported.
+    http_response_code_ = 0;
+    CleanUp();
+    if (delegate_)
+      delegate_->TransferComplete(this, false);
+    return;
+  }
+
+  string file_path = url.substr(strlen("file://"));
+  stream_ =
+      brillo::FileStream::Open(base::FilePath(file_path),
+                               brillo::Stream::AccessMode::READ,
+                               brillo::FileStream::Disposition::OPEN_EXISTING,
+                               nullptr);
+
+  if (!stream_) {
+    LOG(ERROR) << "Couldn't open " << file_path;
+    http_response_code_ = kHttpResponseNotFound;
+    CleanUp();
+    if (delegate_)
+      delegate_->TransferComplete(this, false);
+    return;
+  }
+  http_response_code_ = kHttpResponseOk;
+
+  if (offset_)
+    stream_->SetPosition(offset_, nullptr);
+  bytes_copied_ = 0;
+  transfer_in_progress_ = true;
+  ScheduleRead();
+}
+
+void FileFetcher::TerminateTransfer() {
+  CleanUp();
+  if (delegate_) {
+    // Note that after the callback returns this object may be destroyed.
+    delegate_->TransferTerminated(this);
+  }
+}
+
+void FileFetcher::ScheduleRead() {
+  if (transfer_paused_ || ongoing_read_ || !transfer_in_progress_)
+    return;
+
+  buffer_.resize(kReadBufferSize);
+  size_t bytes_to_read = buffer_.size();
+  if (data_length_ >= 0) {
+    bytes_to_read = std::min(static_cast<uint64_t>(bytes_to_read),
+                             data_length_ - bytes_copied_);
+  }
+
+  if (!bytes_to_read) {
+    OnReadDoneCallback(0);
+    return;
+  }
+
+  ongoing_read_ = stream_->ReadAsync(
+      buffer_.data(),
+      bytes_to_read,
+      base::Bind(&FileFetcher::OnReadDoneCallback, base::Unretained(this)),
+      base::Bind(&FileFetcher::OnReadErrorCallback, base::Unretained(this)),
+      nullptr);
+
+  if (!ongoing_read_) {
+    LOG(ERROR) << "Unable to schedule an asynchronous read from the stream.";
+    CleanUp();
+    if (delegate_)
+      delegate_->TransferComplete(this, false);
+  }
+}
+
+void FileFetcher::OnReadDoneCallback(size_t bytes_read) {
+  ongoing_read_ = false;
+  if (bytes_read == 0) {
+    CleanUp();
+    if (delegate_)
+      delegate_->TransferComplete(this, true);
+  } else {
+    bytes_copied_ += bytes_read;
+    if (delegate_)
+      delegate_->ReceivedBytes(this, buffer_.data(), bytes_read);
+    ScheduleRead();
+  }
+}
+
+void FileFetcher::OnReadErrorCallback(const brillo::Error* error) {
+  LOG(ERROR) << "Asynchronous read failed: " << error->GetMessage();
+  CleanUp();
+  if (delegate_)
+    delegate_->TransferComplete(this, false);
+}
+
+void FileFetcher::Pause() {
+  if (transfer_paused_) {
+    LOG(ERROR) << "Fetcher already paused.";
+    return;
+  }
+  transfer_paused_ = true;
+}
+
+void FileFetcher::Unpause() {
+  if (!transfer_paused_) {
+    LOG(ERROR) << "Resume attempted when fetcher not paused.";
+    return;
+  }
+  transfer_paused_ = false;
+  ScheduleRead();
+}
+
+void FileFetcher::CleanUp() {
+  if (stream_) {
+    stream_->CancelPendingAsyncOperations();
+    stream_->CloseBlocking(nullptr);
+    stream_.reset();
+  }
+  // Destroying the |stream_| releases the callback, so we don't have any
+  // ongoing read at this point.
+  ongoing_read_ = false;
+  buffer_ = brillo::Blob();
+
+  transfer_in_progress_ = false;
+  transfer_paused_ = false;
+}
+
+}  // namespace chromeos_update_engine