Treat all file: URIs as having a unique origin.

This prevents cross-file access from files loaded into the browser from
the local file system, further restricting the origin policy of file:
URIs.

Added a pref to control this behavior for local file access if required
for certain applications, since this change might break using the
browser to run applications on the local file system that require
access to local files.

2 files changed, 35 insertions, 24 deletions

diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 38c3ced91..b31ae8e33 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -1331,6 +1331,9 @@ pref("image.animation_mode",                "normal");
 // Same-origin policy for file URIs, "false" is traditional
 pref("security.fileuri.strict_origin_policy", true);
 
+// Treat all file URIs as having a unique origin.
+pref("security.fileuri.unique_origin", true);
+
 // If this pref is true, prefs in the logging.config branch will be cleared on
 // startup. This is done so that setting a log-file and log-modules at runtime
 // doesn't persist across restarts leading to huge logfile and low disk space.
diff --git a/netwerk/base/nsNetUtil.cpp b/netwerk/base/nsNetUtil.cpp
index 653a9003e..2974e26b0 100644
--- a/netwerk/base/nsNetUtil.cpp
+++ b/netwerk/base/nsNetUtil.cpp
@@ -10,6 +10,7 @@
 #include "mozilla/LoadContext.h"
 #include "mozilla/LoadInfo.h"
 #include "mozilla/BasePrincipal.h"
+#include "mozilla/Preferences.h"
 #include "mozilla/Telemetry.h"
 #include "nsNetUtil.h"
 #include "nsNetUtilInlines.h"
@@ -1821,33 +1822,40 @@ NS_RelaxStrictFileOriginPolicy(nsIURI *aTargetURI,
     return false;
   }
 
-  //
-  // If the file to be loaded is in a subdirectory of the source
-  // (or same-dir if source is not a directory) then it will
-  // inherit its source principal and be scriptable by that source.
-  //
-  bool sourceIsDir;
-  bool allowed = false;
-  nsresult rv = sourceFile->IsDirectory(&sourceIsDir);
-  if (NS_SUCCEEDED(rv) && sourceIsDir) {
-    rv = sourceFile->Contains(targetFile, &allowed);
-  } else {
-    nsCOMPtr<nsIFile> sourceParent;
-    rv = sourceFile->GetParent(getter_AddRefs(sourceParent));
-    if (NS_SUCCEEDED(rv) && sourceParent) {
-      rv = sourceParent->Equals(targetFile, &allowed);
-      if (NS_FAILED(rv) || !allowed) {
-        rv = sourceParent->Contains(targetFile, &allowed);
-      } else {
-        MOZ_ASSERT(aAllowDirectoryTarget,
-                   "sourceFile->Parent == targetFile, but targetFile "
-                   "should've been disallowed if it is a directory");
+  bool uniqueOrigin = true;
+  uniqueOrigin = Preferences::GetBool("security.fileuri.unique_origin");
+  
+  // If treating all files as unique origins, we can skip this because
+  // it should always be refused.
+  if (!uniqueOrigin) {
+    //
+    // If the file to be loaded is in a subdirectory of the source
+    // (or same-dir if source is not a directory) then it will
+    // inherit its source principal and be scriptable by that source.
+    //
+    bool sourceIsDir;
+    bool allowed = false;
+    nsresult rv = sourceFile->IsDirectory(&sourceIsDir);
+    if (NS_SUCCEEDED(rv) && sourceIsDir) {
+      rv = sourceFile->Contains(targetFile, &allowed);
+    } else {
+      nsCOMPtr<nsIFile> sourceParent;
+      rv = sourceFile->GetParent(getter_AddRefs(sourceParent));
+      if (NS_SUCCEEDED(rv) && sourceParent) {
+        rv = sourceParent->Equals(targetFile, &allowed);
+        if (NS_FAILED(rv) || !allowed) {
+          rv = sourceParent->Contains(targetFile, &allowed);
+        } else {
+          MOZ_ASSERT(aAllowDirectoryTarget,
+                     "sourceFile->Parent == targetFile, but targetFile "
+                     "should've been disallowed if it is a directory");
+        }
       }
     }
-  }
 
-  if (NS_SUCCEEDED(rv) && allowed) {
-    return true;
+    if (NS_SUCCEEDED(rv) && allowed) {
+      return true;
+    }
   }
 
   return false;