electron/patches/common/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/content/renderer/dom_storage/dom_storage_cached_area.cc b/content/renderer/dom_storage/dom_storage_cached_area.cc
index 13bcf8e3f2882999e073d0c7ac6d8f1627f0bfa2..6d330cd1de358b477df4c1fed4d814c206a3643d 100644
--- a/content/renderer/dom_storage/dom_storage_cached_area.cc
+++ b/content/renderer/dom_storage/dom_storage_cached_area.cc
@@ -54,11 +54,13 @@ bool DOMStorageCachedArea::SetItem(int connection_id,
                                    const base::string16& key,
                                    const base::string16& value,
                                    const GURL& page_url) {
+#if 0
   // A quick check to reject obviously overbudget items to avoid
   // the priming the cache.
   if ((key.length() + value.length()) * sizeof(base::char16) >
       kPerStorageAreaQuota)
     return false;
+#endif
 
   PrimeIfNeeded(connection_id);
   base::NullableString16 old_value;
diff --git a/content/renderer/dom_storage/local_storage_cached_area.cc b/content/renderer/dom_storage/local_storage_cached_area.cc
index 1b406b322f6de52d808b021015c656f60700645e..8bc713a723569e9d28212d68a0b2a22cd2bcc6c0 100644
--- a/content/renderer/dom_storage/local_storage_cached_area.cc
+++ b/content/renderer/dom_storage/local_storage_cached_area.cc
@@ -142,11 +142,13 @@ bool LocalStorageCachedArea::SetItem(const base::string16& key,
                                      const base::string16& value,
                                      const GURL& page_url,
                                      const std::string& storage_area_id) {
+#if 0
   // A quick check to reject obviously overbudget items to avoid priming the
   // cache.
   if ((key.length() + value.length()) * sizeof(base::char16) >
       kPerStorageAreaQuota)
     return false;
+#endif
 
   EnsureLoaded();
   bool result = false;
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 21ce9fe01d3a125055fe3c3f29cc89ecf014944f..3ecdfe1011113ddaecbad1766cd8044366a9e47f 100644
--- a/third_party/blink/renderer/modules/storage/cached_storage_area.cc
+++ b/third_party/blink/renderer/modules/storage/cached_storage_area.cc
@@ -102,11 +102,13 @@ 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 62ab01c2864baa2ef1945031faf42cbeefbfc72b..e7edaff1778c66812ab9f7058e89f84bfba94339 100644
--- a/third_party/blink/renderer/modules/storage/storage_area_map.cc
+++ b/third_party/blink/renderer/modules/storage/storage_area_map.cc
@@ -104,10 +104,12 @@ bool StorageAreaMap::SetItemInternal(const String& key,
   size_t new_item_size = QuotaForString(key) + QuotaForString(value);
   size_t new_quota_used = quota_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 (check_quota && new_item_size > old_item_size && new_quota_used > quota_)
     return false;
+#endif
 
   keys_values_.Set(key, value);
   ResetKeyIterator();