Add m-esr52 at 52.6.0

1 files changed, 1273 insertions, 0 deletions

diff --git a/netwerk/base/BackgroundFileSaver.cpp b/netwerk/base/BackgroundFileSaver.cpp
new file mode 100644
index 000000000..e4bc05826
--- /dev/null
+++ b/netwerk/base/BackgroundFileSaver.cpp
@@ -0,0 +1,1273 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "BackgroundFileSaver.h"
+
+#include "ScopedNSSTypes.h"
+#include "mozilla/Casting.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Telemetry.h"
+#include "nsCOMArray.h"
+#include "nsIAsyncInputStream.h"
+#include "nsIFile.h"
+#include "nsIMutableArray.h"
+#include "nsIPipe.h"
+#include "nsIX509Cert.h"
+#include "nsIX509CertDB.h"
+#include "nsIX509CertList.h"
+#include "nsNetUtil.h"
+#include "nsThreadUtils.h"
+#include "pk11pub.h"
+#include "secoidt.h"
+
+#ifdef XP_WIN
+#include <windows.h>
+#include <softpub.h>
+#include <wintrust.h>
+#endif // XP_WIN
+
+namespace mozilla {
+namespace net {
+
+// MOZ_LOG=BackgroundFileSaver:5
+static LazyLogModule prlog("BackgroundFileSaver");
+#define LOG(args) MOZ_LOG(prlog, mozilla::LogLevel::Debug, args)
+#define LOG_ENABLED() MOZ_LOG_TEST(prlog, mozilla::LogLevel::Debug)
+
+////////////////////////////////////////////////////////////////////////////////
+//// Globals
+
+/**
+ * Buffer size for writing to the output file or reading from the input file.
+ */
+#define BUFFERED_IO_SIZE (1024 * 32)
+
+/**
+ * When this upper limit is reached, the original request is suspended.
+ */
+#define REQUEST_SUSPEND_AT (1024 * 1024 * 4)
+
+/**
+ * When this lower limit is reached, the original request is resumed.
+ */
+#define REQUEST_RESUME_AT (1024 * 1024 * 2)
+
+////////////////////////////////////////////////////////////////////////////////
+//// NotifyTargetChangeRunnable
+
+/**
+ * Runnable object used to notify the control thread that file contents will now
+ * be saved to the specified file.
+ */
+class NotifyTargetChangeRunnable final : public Runnable
+{
+public:
+  NotifyTargetChangeRunnable(BackgroundFileSaver *aSaver, nsIFile *aTarget)
+  : mSaver(aSaver)
+  , mTarget(aTarget)
+  {
+  }
+
+  NS_IMETHOD Run() override
+  {
+    return mSaver->NotifyTargetChange(mTarget);
+  }
+
+private:
+  RefPtr<BackgroundFileSaver> mSaver;
+  nsCOMPtr<nsIFile> mTarget;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+//// BackgroundFileSaver
+
+uint32_t BackgroundFileSaver::sThreadCount = 0;
+uint32_t BackgroundFileSaver::sTelemetryMaxThreadCount = 0;
+
+BackgroundFileSaver::BackgroundFileSaver()
+: mControlThread(nullptr)
+, mWorkerThread(nullptr)
+, mPipeOutputStream(nullptr)
+, mPipeInputStream(nullptr)
+, mObserver(nullptr)
+, mLock("BackgroundFileSaver.mLock")
+, mWorkerThreadAttentionRequested(false)
+, mFinishRequested(false)
+, mComplete(false)
+, mStatus(NS_OK)
+, mAppend(false)
+, mInitialTarget(nullptr)
+, mInitialTargetKeepPartial(false)
+, mRenamedTarget(nullptr)
+, mRenamedTargetKeepPartial(false)
+, mAsyncCopyContext(nullptr)
+, mSha256Enabled(false)
+, mSignatureInfoEnabled(false)
+, mActualTarget(nullptr)
+, mActualTargetKeepPartial(false)
+, mDigestContext(nullptr)
+{
+  LOG(("Created BackgroundFileSaver [this = %p]", this));
+}
+
+BackgroundFileSaver::~BackgroundFileSaver()
+{
+  LOG(("Destroying BackgroundFileSaver [this = %p]", this));
+  nsNSSShutDownPreventionLock lock;
+  if (isAlreadyShutDown()) {
+    return;
+  }
+  destructorSafeDestroyNSSReference();
+  shutdown(ShutdownCalledFrom::Object);
+}
+
+void
+BackgroundFileSaver::destructorSafeDestroyNSSReference()
+{
+  mDigestContext = nullptr;
+}
+
+void
+BackgroundFileSaver::virtualDestroyNSSReference()
+{
+  destructorSafeDestroyNSSReference();
+}
+
+// Called on the control thread.
+nsresult
+BackgroundFileSaver::Init()
+{
+  MOZ_ASSERT(NS_IsMainThread(), "This should be called on the main thread");
+
+  nsresult rv;
+
+  rv = NS_NewPipe2(getter_AddRefs(mPipeInputStream),
+                   getter_AddRefs(mPipeOutputStream), true, true, 0,
+                   HasInfiniteBuffer() ? UINT32_MAX : 0);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = NS_GetCurrentThread(getter_AddRefs(mControlThread));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = NS_NewThread(getter_AddRefs(mWorkerThread));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  sThreadCount++;
+  if (sThreadCount > sTelemetryMaxThreadCount) {
+    sTelemetryMaxThreadCount = sThreadCount;
+  }
+
+  return NS_OK;
+}
+
+// Called on the control thread.
+NS_IMETHODIMP
+BackgroundFileSaver::GetObserver(nsIBackgroundFileSaverObserver **aObserver)
+{
+  NS_ENSURE_ARG_POINTER(aObserver);
+  *aObserver = mObserver;
+  NS_IF_ADDREF(*aObserver);
+  return NS_OK;
+}
+
+// Called on the control thread.
+NS_IMETHODIMP
+BackgroundFileSaver::SetObserver(nsIBackgroundFileSaverObserver *aObserver)
+{
+  mObserver = aObserver;
+  return NS_OK;
+}
+
+// Called on the control thread.
+NS_IMETHODIMP
+BackgroundFileSaver::EnableAppend()
+{
+  MOZ_ASSERT(NS_IsMainThread(), "This should be called on the main thread");
+
+  MutexAutoLock lock(mLock);
+  mAppend = true;
+
+  return NS_OK;
+}
+
+// Called on the control thread.
+NS_IMETHODIMP
+BackgroundFileSaver::SetTarget(nsIFile *aTarget, bool aKeepPartial)
+{
+  NS_ENSURE_ARG(aTarget);
+  {
+    MutexAutoLock lock(mLock);
+    if (!mInitialTarget) {
+      aTarget->Clone(getter_AddRefs(mInitialTarget));
+      mInitialTargetKeepPartial = aKeepPartial;
+    } else {
+      aTarget->Clone(getter_AddRefs(mRenamedTarget));
+      mRenamedTargetKeepPartial = aKeepPartial;
+    }
+  }
+
+  // After the worker thread wakes up because attention is requested, it will
+  // rename or create the target file as requested, and start copying data.
+  return GetWorkerThreadAttention(true);
+}
+
+// Called on the control thread.
+NS_IMETHODIMP
+BackgroundFileSaver::Finish(nsresult aStatus)
+{
+  nsresult rv;
+
+  // This will cause the NS_AsyncCopy operation, if it's in progress, to consume
+  // all the data that is still in the pipe, and then finish.
+  rv = mPipeOutputStream->Close();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Ensure that, when we get attention from the worker thread, if no pending
+  // rename operation is waiting, the operation will complete.
+  {
+    MutexAutoLock lock(mLock);
+    mFinishRequested = true;
+    if (NS_SUCCEEDED(mStatus)) {
+      mStatus = aStatus;
+    }
+  }
+
+  // After the worker thread wakes up because attention is requested, it will
+  // process the completion conditions, detect that completion is requested, and
+  // notify the main thread of the completion.  If this function was called with
+  // a success code, we wait for the copy to finish before processing the
+  // completion conditions, otherwise we interrupt the copy immediately.
+  return GetWorkerThreadAttention(NS_FAILED(aStatus));
+}
+
+NS_IMETHODIMP
+BackgroundFileSaver::EnableSha256()
+{
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Can't enable sha256 or initialize NSS off the main thread");
+  // Ensure Personal Security Manager is initialized. This is required for
+  // PK11_* operations to work.
+  nsresult rv;
+  nsCOMPtr<nsISupports> nssDummy = do_GetService("@mozilla.org/psm;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+  mSha256Enabled = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BackgroundFileSaver::GetSha256Hash(nsACString& aHash)
+{
+  MOZ_ASSERT(NS_IsMainThread(), "Can't inspect sha256 off the main thread");
+  // We acquire a lock because mSha256 is written on the worker thread.
+  MutexAutoLock lock(mLock);
+  if (mSha256.IsEmpty()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  aHash = mSha256;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BackgroundFileSaver::EnableSignatureInfo()
+{
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Can't enable signature extraction off the main thread");
+  // Ensure Personal Security Manager is initialized.
+  nsresult rv;
+  nsCOMPtr<nsISupports> nssDummy = do_GetService("@mozilla.org/psm;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+  mSignatureInfoEnabled = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BackgroundFileSaver::GetSignatureInfo(nsIArray** aSignatureInfo)
+{
+  MOZ_ASSERT(NS_IsMainThread(), "Can't inspect signature off the main thread");
+  // We acquire a lock because mSignatureInfo is written on the worker thread.
+  MutexAutoLock lock(mLock);
+  if (!mComplete || !mSignatureInfoEnabled) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  nsCOMPtr<nsIMutableArray> sigArray = do_CreateInstance(NS_ARRAY_CONTRACTID);
+  for (int i = 0; i < mSignatureInfo.Count(); ++i) {
+    sigArray->AppendElement(mSignatureInfo[i], false);
+  }
+  *aSignatureInfo = sigArray;
+  NS_IF_ADDREF(*aSignatureInfo);
+  return NS_OK;
+}
+
+// Called on the control thread.
+nsresult
+BackgroundFileSaver::GetWorkerThreadAttention(bool aShouldInterruptCopy)
+{
+  nsresult rv;
+
+  MutexAutoLock lock(mLock);
+
+  // We only require attention one time.  If this function is called two times
+  // before the worker thread wakes up, and the first has aShouldInterruptCopy
+  // false and the second true, we won't forcibly interrupt the copy from the
+  // control thread.  However, that never happens, because calling Finish with a
+  // success code is the only case that may result in aShouldInterruptCopy being
+  // false.  In that case, we won't call this function again, because consumers
+  // should not invoke other methods on the control thread after calling Finish.
+  // And in any case, Finish already closes one end of the pipe, causing the
+  // copy to finish properly on its own.
+  if (mWorkerThreadAttentionRequested) {
+    return NS_OK;
+  }
+
+  if (!mAsyncCopyContext) {
+    // Copy is not in progress, post an event to handle the change manually.
+    rv = mWorkerThread->Dispatch(NewRunnableMethod(this,
+                                                   &BackgroundFileSaver::ProcessAttention),
+                                 NS_DISPATCH_NORMAL);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else if (aShouldInterruptCopy) {
+    // Interrupt the copy.  The copy will be resumed, if needed, by the
+    // ProcessAttention function, invoked by the AsyncCopyCallback function.
+    NS_CancelAsyncCopy(mAsyncCopyContext, NS_ERROR_ABORT);
+  }
+
+  // Indicate that attention has been requested successfully, there is no need
+  // to post another event until the worker thread processes the current one.
+  mWorkerThreadAttentionRequested = true;
+
+  return NS_OK;
+}
+
+// Called on the worker thread.
+// static
+void
+BackgroundFileSaver::AsyncCopyCallback(void *aClosure, nsresult aStatus)
+{
+  BackgroundFileSaver *self = (BackgroundFileSaver *)aClosure;
+  {
+    MutexAutoLock lock(self->mLock);
+
+    // Now that the copy was interrupted or terminated, any notification from
+    // the control thread requires an event to be posted to the worker thread.
+    self->mAsyncCopyContext = nullptr;
+
+    // When detecting failures, ignore the status code we use to interrupt.
+    if (NS_FAILED(aStatus) && aStatus != NS_ERROR_ABORT &&
+        NS_SUCCEEDED(self->mStatus)) {
+      self->mStatus = aStatus;
+    }
+  }
+
+  (void)self->ProcessAttention();
+
+  // We called NS_ADDREF_THIS when NS_AsyncCopy started, to keep the object
+  // alive even if other references disappeared.  At this point, we've finished
+  // using the object and can safely release our reference.
+  NS_RELEASE(self);
+}
+
+// Called on the worker thread.
+nsresult
+BackgroundFileSaver::ProcessAttention()
+{
+  nsresult rv;
+
+  // This function is called whenever the attention of the worker thread has
+  // been requested.  This may happen in these cases:
+  // * We are about to start the copy for the first time.  In this case, we are
+  //   called from an event posted on the worker thread from the control thread
+  //   by GetWorkerThreadAttention, and mAsyncCopyContext is null.
+  // * We have interrupted the copy for some reason.  In this case, we are
+  //   called by AsyncCopyCallback, and mAsyncCopyContext is null.
+  // * We are currently executing ProcessStateChange, and attention is requested
+  //   by the control thread, for example because SetTarget or Finish have been
+  //   called.  In this case, we are called from from an event posted through
+  //   GetWorkerThreadAttention.  While mAsyncCopyContext was always null when
+  //   the event was posted, at this point mAsyncCopyContext may not be null
+  //   anymore, because ProcessStateChange may have started the copy before the
+  //   event that called this function was processed on the worker thread.
+  // If mAsyncCopyContext is not null, we interrupt the copy and re-enter
+  // through AsyncCopyCallback.  This allows us to check if, for instance, we
+  // should rename the target file.  We will then restart the copy if needed.
+  if (mAsyncCopyContext) {
+    NS_CancelAsyncCopy(mAsyncCopyContext, NS_ERROR_ABORT);
+    return NS_OK;
+  }
+  // Use the current shared state to determine the next operation to execute.
+  rv = ProcessStateChange();
+  if (NS_FAILED(rv)) {
+    // If something failed while processing, terminate the operation now.
+    {
+      MutexAutoLock lock(mLock);
+
+      if (NS_SUCCEEDED(mStatus)) {
+        mStatus = rv;
+      }
+    }
+    // Ensure we notify completion now that the operation failed.
+    CheckCompletion();
+  }
+
+  return NS_OK;
+}
+
+// Called on the worker thread.
+nsresult
+BackgroundFileSaver::ProcessStateChange()
+{
+  nsresult rv;
+
+  // We might have been notified because the operation is complete, verify.
+  if (CheckCompletion()) {
+    return NS_OK;
+  }
+
+  // Get a copy of the current shared state for the worker thread.
+  nsCOMPtr<nsIFile> initialTarget;
+  bool initialTargetKeepPartial;
+  nsCOMPtr<nsIFile> renamedTarget;
+  bool renamedTargetKeepPartial;
+  bool sha256Enabled;
+  bool append;
+  {
+    MutexAutoLock lock(mLock);
+
+    initialTarget = mInitialTarget;
+    initialTargetKeepPartial = mInitialTargetKeepPartial;
+    renamedTarget = mRenamedTarget;
+    renamedTargetKeepPartial = mRenamedTargetKeepPartial;
+    sha256Enabled = mSha256Enabled;
+    append = mAppend;
+
+    // From now on, another attention event needs to be posted if state changes.
+    mWorkerThreadAttentionRequested = false;
+  }
+
+  // The initial target can only be null if it has never been assigned.  In this
+  // case, there is nothing to do since we never created any output file.
+  if (!initialTarget) {
+    return NS_OK;
+  }
+
+  // Determine if we are processing the attention request for the first time.
+  bool isContinuation = !!mActualTarget;
+  if (!isContinuation) {
+    // Assign the target file for the first time.
+    mActualTarget = initialTarget;
+    mActualTargetKeepPartial = initialTargetKeepPartial;
+  }
+
+  // Verify whether we have actually been instructed to use a different file.
+  // This may happen the first time this function is executed, if SetTarget was
+  // called two times before the worker thread processed the attention request.
+  bool equalToCurrent = false;
+  if (renamedTarget) {
+    rv = mActualTarget->Equals(renamedTarget, &equalToCurrent);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (!equalToCurrent)
+    {
+      // If we were asked to rename the file but the initial file did not exist,
+      // we simply create the file in the renamed location.  We avoid this check
+      // if we have already started writing the output file ourselves.
+      bool exists = true;
+      if (!isContinuation) {
+        rv = mActualTarget->Exists(&exists);
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+      if (exists) {
+        // We are moving the previous target file to a different location.
+        nsCOMPtr<nsIFile> renamedTargetParentDir;
+        rv = renamedTarget->GetParent(getter_AddRefs(renamedTargetParentDir));
+        NS_ENSURE_SUCCESS(rv, rv);
+
+        nsAutoString renamedTargetName;
+        rv = renamedTarget->GetLeafName(renamedTargetName);
+        NS_ENSURE_SUCCESS(rv, rv);
+
+        // We must delete any existing target file before moving the current
+        // one.
+        rv = renamedTarget->Exists(&exists);
+        NS_ENSURE_SUCCESS(rv, rv);
+        if (exists) {
+          rv = renamedTarget->Remove(false);
+          NS_ENSURE_SUCCESS(rv, rv);
+        }
+
+        // Move the file.  If this fails, we still reference the original file
+        // in mActualTarget, so that it is deleted if requested.  If this
+        // succeeds, the nsIFile instance referenced by mActualTarget mutates
+        // and starts pointing to the new file, but we'll discard the reference.
+        rv = mActualTarget->MoveTo(renamedTargetParentDir, renamedTargetName);
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+
+      // Now we can update the actual target file name.
+      mActualTarget = renamedTarget;
+      mActualTargetKeepPartial = renamedTargetKeepPartial;
+    }
+  }
+
+  // Notify if the target file name actually changed.
+  if (!equalToCurrent) {
+    // We must clone the nsIFile instance because mActualTarget is not
+    // immutable, it may change if the target is renamed later.
+    nsCOMPtr<nsIFile> actualTargetToNotify;
+    rv = mActualTarget->Clone(getter_AddRefs(actualTargetToNotify));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    RefPtr<NotifyTargetChangeRunnable> event =
+      new NotifyTargetChangeRunnable(this, actualTargetToNotify);
+    NS_ENSURE_TRUE(event, NS_ERROR_FAILURE);
+
+    rv = mControlThread->Dispatch(event, NS_DISPATCH_NORMAL);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (isContinuation) {
+    // The pending rename operation might be the last task before finishing. We
+    // may return here only if we have already created the target file.
+    if (CheckCompletion()) {
+      return NS_OK;
+    }
+
+    // Even if the operation did not complete, the pipe input stream may be
+    // empty and may have been closed already.  We detect this case using the
+    // Available property, because it never returns an error if there is more
+    // data to be consumed.  If the pipe input stream is closed, we just exit
+    // and wait for more calls like SetTarget or Finish to be invoked on the
+    // control thread.  However, we still truncate the file or create the
+    // initial digest context if we are expected to do that.
+    uint64_t available;
+    rv = mPipeInputStream->Available(&available);
+    if (NS_FAILED(rv)) {
+      return NS_OK;
+    }
+  }
+
+  // Create the digest context if requested and NSS hasn't been shut down.
+  if (sha256Enabled && !mDigestContext) {
+    nsNSSShutDownPreventionLock lock;
+    if (!isAlreadyShutDown()) {
+      mDigestContext = UniquePK11Context(
+        PK11_CreateDigestContext(SEC_OID_SHA256));
+      NS_ENSURE_TRUE(mDigestContext, NS_ERROR_OUT_OF_MEMORY);
+    }
+  }
+
+  // When we are requested to append to an existing file, we should read the
+  // existing data and ensure we include it as part of the final hash.
+  if (mDigestContext && append && !isContinuation) {
+    nsCOMPtr<nsIInputStream> inputStream;
+    rv = NS_NewLocalFileInputStream(getter_AddRefs(inputStream),
+                                    mActualTarget,
+                                    PR_RDONLY | nsIFile::OS_READAHEAD);
+    if (rv != NS_ERROR_FILE_NOT_FOUND) {
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      char buffer[BUFFERED_IO_SIZE];
+      while (true) {
+        uint32_t count;
+        rv = inputStream->Read(buffer, BUFFERED_IO_SIZE, &count);
+        NS_ENSURE_SUCCESS(rv, rv);
+
+        if (count == 0) {
+          // We reached the end of the file.
+          break;
+        }
+
+        nsNSSShutDownPreventionLock lock;
+        if (isAlreadyShutDown()) {
+          return NS_ERROR_NOT_AVAILABLE;
+        }
+
+        nsresult rv = MapSECStatus(
+          PK11_DigestOp(mDigestContext.get(),
+                        BitwiseCast<unsigned char*, char*>(buffer),
+                        count));
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+
+      rv = inputStream->Close();
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+
+  // We will append to the initial target file only if it was requested by the
+  // caller, but we'll always append on subsequent accesses to the target file.
+  int32_t creationIoFlags;
+  if (isContinuation) {
+    creationIoFlags = PR_APPEND;
+  } else {
+    creationIoFlags = (append ? PR_APPEND : PR_TRUNCATE) | PR_CREATE_FILE;
+  }
+
+  // Create the target file, or append to it if we already started writing it.
+  // The 0600 permissions are used while the file is being downloaded, and for
+  // interrupted downloads. Those may be located in the system temporary
+  // directory, as well as the target directory, and generally have a ".part"
+  // extension. Those part files should never be group or world-writable even
+  // if the umask allows it.
+  nsCOMPtr<nsIOutputStream> outputStream;
+  rv = NS_NewLocalFileOutputStream(getter_AddRefs(outputStream),
+                                   mActualTarget,
+                                   PR_WRONLY | creationIoFlags, 0600);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  outputStream = NS_BufferOutputStream(outputStream, BUFFERED_IO_SIZE);
+  if (!outputStream) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Wrap the output stream so that it feeds the digest context if needed.
+  if (mDigestContext) {
+    // No need to acquire the NSS lock here, DigestOutputStream must acquire it
+    // in any case before each asynchronous write. Constructing the
+    // DigestOutputStream cannot fail. Passing mDigestContext to
+    // DigestOutputStream is safe, because BackgroundFileSaver always outlives
+    // the outputStream. BackgroundFileSaver is reference-counted before the
+    // call to AsyncCopy, and mDigestContext is never destroyed before
+    // AsyncCopyCallback.
+    outputStream = new DigestOutputStream(outputStream, mDigestContext.get());
+  }
+
+  // Start copying our input to the target file.  No errors can be raised past
+  // this point if the copy starts, since they should be handled by the thread.
+  {
+    MutexAutoLock lock(mLock);
+
+    rv = NS_AsyncCopy(mPipeInputStream, outputStream, mWorkerThread,
+                      NS_ASYNCCOPY_VIA_READSEGMENTS, 4096, AsyncCopyCallback,
+                      this, false, true, getter_AddRefs(mAsyncCopyContext),
+                      GetProgressCallback());
+    if (NS_FAILED(rv)) {
+      NS_WARNING("NS_AsyncCopy failed.");
+      mAsyncCopyContext = nullptr;
+      return rv;
+    }
+  }
+
+  // If the operation succeeded, we must ensure that we keep this object alive
+  // for the entire duration of the copy, since only the raw pointer will be
+  // provided as the argument of the AsyncCopyCallback function.  We can add the
+  // reference now, after NS_AsyncCopy returned, because it always starts
+  // processing asynchronously, and there is no risk that the callback is
+  // invoked before we reach this point.  If the operation failed instead, then
+  // AsyncCopyCallback will never be called.
+  NS_ADDREF_THIS();
+
+  return NS_OK;
+}
+
+// Called on the worker thread.
+bool
+BackgroundFileSaver::CheckCompletion()
+{
+  nsresult rv;
+
+  MOZ_ASSERT(!mAsyncCopyContext,
+             "Should not be copying when checking completion conditions.");
+
+  bool failed = true;
+  {
+    MutexAutoLock lock(mLock);
+
+    if (mComplete) {
+      return true;
+    }
+
+    // If an error occurred, we don't need to do the checks in this code block,
+    // and the operation can be completed immediately with a failure code.
+    if (NS_SUCCEEDED(mStatus)) {
+      failed = false;
+
+      // We did not incur in an error, so we must determine if we can stop now.
+      // If the Finish method has not been called, we can just continue now.
+      if (!mFinishRequested) {
+        return false;
+      }
+
+      // We can only stop when all the operations requested by the control
+      // thread have been processed.  First, we check whether we have processed
+      // the first SetTarget call, if any.  Then, we check whether we have
+      // processed any rename requested by subsequent SetTarget calls.
+      if ((mInitialTarget && !mActualTarget) ||
+          (mRenamedTarget && mRenamedTarget != mActualTarget)) {
+        return false;
+      }
+
+      // If we still have data to write to the output file, allow the copy
+      // operation to resume.  The Available getter may return an error if one
+      // of the pipe's streams has been already closed.
+      uint64_t available;
+      rv = mPipeInputStream->Available(&available);
+      if (NS_SUCCEEDED(rv) && available != 0) {
+        return false;
+      }
+    }
+
+    mComplete = true;
+  }
+
+  // Ensure we notify completion now that the operation finished.
+  // Do a best-effort attempt to remove the file if required.
+  if (failed && mActualTarget && !mActualTargetKeepPartial) {
+    (void)mActualTarget->Remove(false);
+  }
+
+  // Finish computing the hash
+  if (!failed && mDigestContext) {
+    nsNSSShutDownPreventionLock lock;
+    if (!isAlreadyShutDown()) {
+      Digest d;
+      rv = d.End(SEC_OID_SHA256, mDigestContext);
+      if (NS_SUCCEEDED(rv)) {
+        MutexAutoLock lock(mLock);
+        mSha256 =
+          nsDependentCSubstring(BitwiseCast<char*, unsigned char*>(d.get().data),
+                                d.get().len);
+      }
+    }
+  }
+
+  // Compute the signature of the binary. ExtractSignatureInfo doesn't do
+  // anything on non-Windows platforms except return an empty nsIArray.
+  if (!failed && mActualTarget) {
+    nsString filePath;
+    mActualTarget->GetTarget(filePath);
+    nsresult rv = ExtractSignatureInfo(filePath);
+    if (NS_FAILED(rv)) {
+      LOG(("Unable to extract signature information [this = %p].", this));
+    } else {
+      LOG(("Signature extraction success! [this = %p]", this));
+    }
+  }
+
+  // Post an event to notify that the operation completed.
+  if (NS_FAILED(mControlThread->Dispatch(NewRunnableMethod(this,
+                                                           &BackgroundFileSaver::NotifySaveComplete),
+                                         NS_DISPATCH_NORMAL))) {
+    NS_WARNING("Unable to post completion event to the control thread.");
+  }
+
+  return true;
+}
+
+// Called on the control thread.
+nsresult
+BackgroundFileSaver::NotifyTargetChange(nsIFile *aTarget)
+{
+  if (mObserver) {
+    (void)mObserver->OnTargetChange(this, aTarget);
+  }
+
+  return NS_OK;
+}
+
+// Called on the control thread.
+nsresult
+BackgroundFileSaver::NotifySaveComplete()
+{
+  MOZ_ASSERT(NS_IsMainThread(), "This should be called on the main thread");
+
+  nsresult status;
+  {
+    MutexAutoLock lock(mLock);
+    status = mStatus;
+  }
+
+  if (mObserver) {
+    (void)mObserver->OnSaveComplete(this, status);
+  }
+
+  // At this point, the worker thread will not process any more events, and we
+  // can shut it down.  Shutting down a thread may re-enter the event loop on
+  // this thread.  This is not a problem in this case, since this function is
+  // called by a top-level event itself, and we have already invoked the
+  // completion observer callback.  Re-entering the loop can only delay the
+  // final release and destruction of this saver object, since we are keeping a
+  // reference to it through the event object.
+  mWorkerThread->Shutdown();
+
+  sThreadCount--;
+
+  // When there are no more active downloads, we consider the download session
+  // finished. We record the maximum number of concurrent downloads reached
+  // during the session in a telemetry histogram, and we reset the maximum
+  // thread counter for the next download session
+  if (sThreadCount == 0) {
+    Telemetry::Accumulate(Telemetry::BACKGROUNDFILESAVER_THREAD_COUNT,
+                          sTelemetryMaxThreadCount);
+    sTelemetryMaxThreadCount = 0;
+  }
+
+  return NS_OK;
+}
+
+nsresult
+BackgroundFileSaver::ExtractSignatureInfo(const nsAString& filePath)
+{
+  MOZ_ASSERT(!NS_IsMainThread(), "Cannot extract signature on main thread");
+
+  nsNSSShutDownPreventionLock nssLock;
+  if (isAlreadyShutDown()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  {
+    MutexAutoLock lock(mLock);
+    if (!mSignatureInfoEnabled) {
+      return NS_OK;
+    }
+  }
+  nsresult rv;
+  nsCOMPtr<nsIX509CertDB> certDB = do_GetService(NS_X509CERTDB_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+#ifdef XP_WIN
+  // Setup the file to check.
+  WINTRUST_FILE_INFO fileToCheck = {0};
+  fileToCheck.cbStruct = sizeof(WINTRUST_FILE_INFO);
+  fileToCheck.pcwszFilePath = filePath.Data();
+  fileToCheck.hFile = nullptr;
+  fileToCheck.pgKnownSubject = nullptr;
+
+  // We want to check it is signed and trusted.
+  WINTRUST_DATA trustData = {0};
+  trustData.cbStruct = sizeof(trustData);
+  trustData.pPolicyCallbackData = nullptr;
+  trustData.pSIPClientData = nullptr;
+  trustData.dwUIChoice = WTD_UI_NONE;
+  trustData.fdwRevocationChecks = WTD_REVOKE_NONE;
+  trustData.dwUnionChoice = WTD_CHOICE_FILE;
+  trustData.dwStateAction = WTD_STATEACTION_VERIFY;
+  trustData.hWVTStateData = nullptr;
+  trustData.pwszURLReference = nullptr;
+  // Disallow revocation checks over the network
+  trustData.dwProvFlags = WTD_CACHE_ONLY_URL_RETRIEVAL;
+  // no UI
+  trustData.dwUIContext = 0;
+  trustData.pFile = &fileToCheck;
+
+  // The WINTRUST_ACTION_GENERIC_VERIFY_V2 policy verifies that the certificate
+  // chains up to a trusted root CA and has appropriate permissions to sign
+  // code.
+  GUID policyGUID = WINTRUST_ACTION_GENERIC_VERIFY_V2;
+  // Check if the file is signed by something that is trusted. If the file is
+  // not signed, this is a no-op.
+  LONG ret = WinVerifyTrust(nullptr, &policyGUID, &trustData);
+  CRYPT_PROVIDER_DATA* cryptoProviderData = nullptr;
+  // According to the Windows documentation, we should check against 0 instead
+  // of ERROR_SUCCESS, which is an HRESULT.
+  if (ret == 0) {
+    cryptoProviderData = WTHelperProvDataFromStateData(trustData.hWVTStateData);
+  }
+  if (cryptoProviderData) {
+    // Lock because signature information is read on the main thread.
+    MutexAutoLock lock(mLock);
+    LOG(("Downloaded trusted and signed file [this = %p].", this));
+    // A binary may have multiple signers. Each signer may have multiple certs
+    // in the chain.
+    for (DWORD i = 0; i < cryptoProviderData->csSigners; ++i) {
+      const CERT_CHAIN_CONTEXT* certChainContext =
+        cryptoProviderData->pasSigners[i].pChainContext;
+      if (!certChainContext) {
+        break;
+      }
+      for (DWORD j = 0; j < certChainContext->cChain; ++j) {
+        const CERT_SIMPLE_CHAIN* certSimpleChain =
+          certChainContext->rgpChain[j];
+        if (!certSimpleChain) {
+          break;
+        }
+        nsCOMPtr<nsIX509CertList> nssCertList =
+          do_CreateInstance(NS_X509CERTLIST_CONTRACTID);
+        if (!nssCertList) {
+          break;
+        }
+        bool extractionSuccess = true;
+        for (DWORD k = 0; k < certSimpleChain->cElement; ++k) {
+          CERT_CHAIN_ELEMENT* certChainElement = certSimpleChain->rgpElement[k];
+          if (certChainElement->pCertContext->dwCertEncodingType !=
+            X509_ASN_ENCODING) {
+              continue;
+          }
+          nsCOMPtr<nsIX509Cert> nssCert = nullptr;
+          rv = certDB->ConstructX509(
+            reinterpret_cast<char *>(
+              certChainElement->pCertContext->pbCertEncoded),
+            certChainElement->pCertContext->cbCertEncoded,
+            getter_AddRefs(nssCert));
+          if (!nssCert) {
+            extractionSuccess = false;
+            LOG(("Couldn't create NSS cert [this = %p]", this));
+            break;
+          }
+          nssCertList->AddCert(nssCert);
+          nsString subjectName;
+          nssCert->GetSubjectName(subjectName);
+          LOG(("Adding cert %s [this = %p]",
+               NS_ConvertUTF16toUTF8(subjectName).get(), this));
+        }
+        if (extractionSuccess) {
+          mSignatureInfo.AppendObject(nssCertList);
+        }
+      }
+    }
+    // Free the provider data if cryptoProviderData is not null.
+    trustData.dwStateAction = WTD_STATEACTION_CLOSE;
+    WinVerifyTrust(nullptr, &policyGUID, &trustData);
+  } else {
+    LOG(("Downloaded unsigned or untrusted file [this = %p].", this));
+  }
+#endif
+  return NS_OK;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//// BackgroundFileSaverOutputStream
+
+NS_IMPL_ISUPPORTS(BackgroundFileSaverOutputStream,
+                  nsIBackgroundFileSaver,
+                  nsIOutputStream,
+                  nsIAsyncOutputStream,
+                  nsIOutputStreamCallback)
+
+BackgroundFileSaverOutputStream::BackgroundFileSaverOutputStream()
+: BackgroundFileSaver()
+, mAsyncWaitCallback(nullptr)
+{
+}
+
+BackgroundFileSaverOutputStream::~BackgroundFileSaverOutputStream()
+{
+}
+
+bool
+BackgroundFileSaverOutputStream::HasInfiniteBuffer()
+{
+  return false;
+}
+
+nsAsyncCopyProgressFun
+BackgroundFileSaverOutputStream::GetProgressCallback()
+{
+  return nullptr;
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::Close()
+{
+  return mPipeOutputStream->Close();
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::Flush()
+{
+  return mPipeOutputStream->Flush();
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::Write(const char *aBuf, uint32_t aCount,
+                                       uint32_t *_retval)
+{
+  return mPipeOutputStream->Write(aBuf, aCount, _retval);
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::WriteFrom(nsIInputStream *aFromStream,
+                                           uint32_t aCount, uint32_t *_retval)
+{
+  return mPipeOutputStream->WriteFrom(aFromStream, aCount, _retval);
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::WriteSegments(nsReadSegmentFun aReader,
+                                               void *aClosure, uint32_t aCount,
+                                               uint32_t *_retval)
+{
+  return mPipeOutputStream->WriteSegments(aReader, aClosure, aCount, _retval);
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::IsNonBlocking(bool *_retval)
+{
+  return mPipeOutputStream->IsNonBlocking(_retval);
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::CloseWithStatus(nsresult reason)
+{
+  return mPipeOutputStream->CloseWithStatus(reason);
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::AsyncWait(nsIOutputStreamCallback *aCallback,
+                                           uint32_t aFlags,
+                                           uint32_t aRequestedCount,
+                                           nsIEventTarget *aEventTarget)
+{
+  NS_ENSURE_STATE(!mAsyncWaitCallback);
+
+  mAsyncWaitCallback = aCallback;
+
+  return mPipeOutputStream->AsyncWait(this, aFlags, aRequestedCount,
+                                      aEventTarget);
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverOutputStream::OnOutputStreamReady(
+                                 nsIAsyncOutputStream *aStream)
+{
+  NS_ENSURE_STATE(mAsyncWaitCallback);
+
+  nsCOMPtr<nsIOutputStreamCallback> asyncWaitCallback = nullptr;
+  asyncWaitCallback.swap(mAsyncWaitCallback);
+
+  return asyncWaitCallback->OnOutputStreamReady(this);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//// BackgroundFileSaverStreamListener
+
+NS_IMPL_ISUPPORTS(BackgroundFileSaverStreamListener,
+                  nsIBackgroundFileSaver,
+                  nsIRequestObserver,
+                  nsIStreamListener)
+
+BackgroundFileSaverStreamListener::BackgroundFileSaverStreamListener()
+: BackgroundFileSaver()
+, mSuspensionLock("BackgroundFileSaverStreamListener.mSuspensionLock")
+, mReceivedTooMuchData(false)
+, mRequest(nullptr)
+, mRequestSuspended(false)
+{
+}
+
+BackgroundFileSaverStreamListener::~BackgroundFileSaverStreamListener()
+{
+}
+
+bool
+BackgroundFileSaverStreamListener::HasInfiniteBuffer()
+{
+  return true;
+}
+
+nsAsyncCopyProgressFun
+BackgroundFileSaverStreamListener::GetProgressCallback()
+{
+  return AsyncCopyProgressCallback;
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverStreamListener::OnStartRequest(nsIRequest *aRequest,
+                                                  nsISupports *aContext)
+{
+  NS_ENSURE_ARG(aRequest);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverStreamListener::OnStopRequest(nsIRequest *aRequest,
+                                                 nsISupports *aContext,
+                                                 nsresult aStatusCode)
+{
+  // If an error occurred, cancel the operation immediately.  On success, wait
+  // until the caller has determined whether the file should be renamed.
+  if (NS_FAILED(aStatusCode)) {
+    Finish(aStatusCode);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BackgroundFileSaverStreamListener::OnDataAvailable(nsIRequest *aRequest,
+                                                   nsISupports *aContext,
+                                                   nsIInputStream *aInputStream,
+                                                   uint64_t aOffset,
+                                                   uint32_t aCount)
+{
+  nsresult rv;
+
+  NS_ENSURE_ARG(aRequest);
+
+  // Read the requested data.  Since the pipe has an infinite buffer, we don't
+  // expect any write error to occur here.
+  uint32_t writeCount;
+  rv = mPipeOutputStream->WriteFrom(aInputStream, aCount, &writeCount);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // If reading from the input stream fails for any reason, the pipe will return
+  // a success code, but without reading all the data.  Since we should be able
+  // to read the requested data when OnDataAvailable is called, raise an error.
+  if (writeCount < aCount) {
+    NS_WARNING("Reading from the input stream should not have failed.");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  bool stateChanged = false;
+  {
+    MutexAutoLock lock(mSuspensionLock);
+
+    if (!mReceivedTooMuchData) {
+      uint64_t available;
+      nsresult rv = mPipeInputStream->Available(&available);
+      if (NS_SUCCEEDED(rv) && available > REQUEST_SUSPEND_AT) {
+        mReceivedTooMuchData = true;
+        mRequest = aRequest;
+        stateChanged = true;
+      }
+    }
+  }
+
+  if (stateChanged) {
+    NotifySuspendOrResume();
+  }
+
+  return NS_OK;
+}
+
+// Called on the worker thread.
+// static
+void
+BackgroundFileSaverStreamListener::AsyncCopyProgressCallback(void *aClosure,
+                                                             uint32_t aCount)
+{
+  BackgroundFileSaverStreamListener *self =
+    (BackgroundFileSaverStreamListener *)aClosure;
+
+  // Wait if the control thread is in the process of suspending or resuming.
+  MutexAutoLock lock(self->mSuspensionLock);
+
+  // This function is called when some bytes are consumed by NS_AsyncCopy.  Each
+  // time this happens, verify if a suspended request should be resumed, because
+  // we have now consumed enough data.
+  if (self->mReceivedTooMuchData) {
+    uint64_t available;
+    nsresult rv = self->mPipeInputStream->Available(&available);
+    if (NS_FAILED(rv) || available < REQUEST_RESUME_AT) {
+      self->mReceivedTooMuchData = false;
+
+      // Post an event to verify if the request should be resumed.
+      if (NS_FAILED(self->mControlThread->Dispatch(NewRunnableMethod(self,
+                                                                     &BackgroundFileSaverStreamListener::NotifySuspendOrResume),
+                                                   NS_DISPATCH_NORMAL))) {
+        NS_WARNING("Unable to post resume event to the control thread.");
+      }
+    }
+  }
+}
+
+// Called on the control thread.
+nsresult
+BackgroundFileSaverStreamListener::NotifySuspendOrResume()
+{
+  // Prevent the worker thread from changing state while processing.
+  MutexAutoLock lock(mSuspensionLock);
+
+  if (mReceivedTooMuchData) {
+    if (!mRequestSuspended) {
+      // Try to suspend the request.  If this fails, don't try to resume later.
+      if (NS_SUCCEEDED(mRequest->Suspend())) {
+        mRequestSuspended = true;
+      } else {
+        NS_WARNING("Unable to suspend the request.");
+      }
+    }
+  } else {
+    if (mRequestSuspended) {
+      // Resume the request only if we succeeded in suspending it.
+      if (NS_SUCCEEDED(mRequest->Resume())) {
+        mRequestSuspended = false;
+      } else {
+        NS_WARNING("Unable to resume the request.");
+      }
+    }
+  }
+
+  return NS_OK;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//// DigestOutputStream
+NS_IMPL_ISUPPORTS(DigestOutputStream,
+                  nsIOutputStream)
+
+DigestOutputStream::DigestOutputStream(nsIOutputStream* aStream,
+                                       PK11Context* aContext) :
+  mOutputStream(aStream)
+  , mDigestContext(aContext)
+{
+  MOZ_ASSERT(mDigestContext, "Can't have null digest context");
+  MOZ_ASSERT(mOutputStream, "Can't have null output stream");
+}
+
+DigestOutputStream::~DigestOutputStream()
+{
+  nsNSSShutDownPreventionLock locker;
+  if (isAlreadyShutDown()) {
+    return;
+  }
+  shutdown(ShutdownCalledFrom::Object);
+}
+
+NS_IMETHODIMP
+DigestOutputStream::Close()
+{
+  return mOutputStream->Close();
+}
+
+NS_IMETHODIMP
+DigestOutputStream::Flush()
+{
+  return mOutputStream->Flush();
+}
+
+NS_IMETHODIMP
+DigestOutputStream::Write(const char* aBuf, uint32_t aCount, uint32_t* retval)
+{
+  nsNSSShutDownPreventionLock lock;
+  if (isAlreadyShutDown()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsresult rv = MapSECStatus(
+    PK11_DigestOp(mDigestContext,
+                  BitwiseCast<const unsigned char*, const char*>(aBuf),
+                  aCount));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return mOutputStream->Write(aBuf, aCount, retval);
+}
+
+NS_IMETHODIMP
+DigestOutputStream::WriteFrom(nsIInputStream* aFromStream,
+                              uint32_t aCount, uint32_t* retval)
+{
+  // Not supported. We could read the stream to a buf, call DigestOp on the
+  // result, seek back and pass the stream on, but it's not worth it since our
+  // application (NS_AsyncCopy) doesn't invoke this on the sink.
+  MOZ_CRASH("DigestOutputStream::WriteFrom not implemented");
+}
+
+NS_IMETHODIMP
+DigestOutputStream::WriteSegments(nsReadSegmentFun aReader,
+                                  void *aClosure, uint32_t aCount,
+                                  uint32_t *retval)
+{
+  MOZ_CRASH("DigestOutputStream::WriteSegments not implemented");
+}
+
+NS_IMETHODIMP
+DigestOutputStream::IsNonBlocking(bool *retval)
+{
+  return mOutputStream->IsNonBlocking(retval);
+}
+
+#undef LOG_ENABLED
+
+} // namespace net
+} // namespace mozilla