electron/patches/chromium/dom_storage_limits.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jacob Quant <jacobq@gmail.com>
Date: Tue, 6 Nov 2018 15:26:00 -0600
Subject: dom_storage_limits.patch

This patch circumvents the restriction on DOM storage objects,
namely `localStorage` and `sessionStorage`, which chromium otherwise
limits to approximately 10MiB.

That restriction originates from a recommendation
[in the Web Storage API specification](https://html.spec.whatwg.org/multipage/webstorage.html#disk-space-2)
that is motivated by the concern that hostile code could abuse this
feature to exhaust available storage capacity.
However, in the case of  Electron, where the application developers
have control over all of the code being executed,
this safety precaution becomes a hindrance that does not add much value.
For example, if a malicious developer wanted to consume disk space
on a victim's machine they could do so via Node's native file system API.

By disabling this restriction or increasing the quota,
electron application developers can use `localStorage`
as their application's "back end", without being having
to limit the amount of data stored to 10MiB.

There may still be some benefit to keeping this restriction for applications that load remote content.
Although all remote data should be from a trusted source and transferred using
a secure channel, it is nevertheless advisable to include additional layers of protection
to mitigate risks associated with potential compromise of those other technologies.
With that in mind, an acceptable alternative to disabling the limit at compile-time
(as this patch currently does) would be to instead allow it to be disabled at run-time
for a given `BrowserWindow` via a `webPreferences` option,
similar to [`nodeIntegration`](https://electronjs.org/docs/tutorial/security#2-disable-nodejs-integration-for-remote-content).

diff --git a/content/common/dom_storage/dom_storage_map.cc b/content/common/dom_storage/dom_storage_map.cc
index fd088fb170bead6452ded14016f21f0c29659e03..b90b6cf9132d16bc3b2076c3fa313916e2b5ea7d 100644
--- a/content/common/dom_storage/dom_storage_map.cc
+++ b/content/common/dom_storage/dom_storage_map.cc
@@ -185,10 +185,12 @@ bool DOMStorageMap::SetItemInternal(MapType* map_type,
   size_t new_item_size = size_in_storage(key, value);
   size_t new_storage_used = storage_used_ - old_item_size + new_item_size;
 
+#if 0
   // Only check quota if the size is increasing, this allows
   // shrinking changes to pre-existing files that are over budget.
   if (new_item_size > old_item_size && new_storage_used > quota_)
     return false;
+#endif
 
   (*map_type)[key] = value;
   ResetKeyIterator();
diff --git a/content/common/dom_storage/dom_storage_types.h b/content/common/dom_storage/dom_storage_types.h
index e87afe5b8ee07f7038a7cc9c40832b6cd27884da..61c9a0dfff60f79c7b36ff5c7d741c06dca03ada 100644
--- a/content/common/dom_storage/dom_storage_types.h
+++ b/content/common/dom_storage/dom_storage_types.h
@@ -21,6 +21,7 @@ typedef std::map<base::string16, base::NullableString16> DOMStorageValuesMap;
 
 // The quota for each storage area.
 // This value is enforced in renderer processes and the browser process.
+// However, Electron's dom_storage_limits.patch removes the code that checks this limit.
 const size_t kPerStorageAreaQuota = 10 * 1024 * 1024;
 
 // In the browser process we allow some overage to
diff --git a/third_party/blink/renderer/modules/storage/cached_storage_area.cc b/third_party/blink/renderer/modules/storage/cached_storage_area.cc
index 6a3a3718443aebf24fd60e00f8f01ba76575ebfa..fb8250553164ebaf1a5ccae4a1c8e2f660ea6e14 100644
--- a/third_party/blink/renderer/modules/storage/cached_storage_area.cc
+++ b/third_party/blink/renderer/modules/storage/cached_storage_area.cc
@@ -106,11 +106,13 @@ bool CachedStorageArea::SetItem(const String& key,
                                 Source* source) {
   DCHECK(areas_->Contains(source));
 
+#if 0
   // A quick check to reject obviously overbudget items to avoid priming the
   // cache.
   if ((key.length() + value.length()) * 2 >
       mojom::blink::StorageArea::kPerStorageAreaQuota)
     return false;
+#endif
 
   EnsureLoaded();
   String old_value;
diff --git a/third_party/blink/renderer/modules/storage/storage_area_map.cc b/third_party/blink/renderer/modules/storage/storage_area_map.cc
index 0da8a1e891edad60355792c40b7d15e90c1086e8..df71418d598d5bdf41e9a8a4340999d9d277aeef 100644
--- a/third_party/blink/renderer/modules/storage/storage_area_map.cc
+++ b/third_party/blink/renderer/modules/storage/storage_area_map.cc
@@ -113,10 +113,12 @@ bool StorageAreaMap::SetItemInternal(const String& key,
   size_t new_quota_used = quota_used_ - old_item_size + new_item_size;
   size_t new_memory_used = memory_used_ - old_item_memory + new_item_memory;
 
+#if 0
   // Only check quota if the size is increasing, this allows
   // shrinking changes to pre-existing files that are over budget.
   if (check_quota && new_item_size > old_item_size && new_quota_used > quota_)
     return false;
+#endif
 
   keys_values_.Set(key, value);
   ResetKeyIterator();