From 8098b926f8e893a610397238e1b80cb4ef3f4668 Mon Sep 17 00:00:00 2001
From: Fedor <fedor@mail.ru>
Date: Sun, 7 Feb 2021 17:32:58 +0200
Subject: [PATCH] Check for triggering principal URI in FTP subresource check.

---
 dom/security/nsContentSecurityManager.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/dom/security/nsContentSecurityManager.cpp b/dom/security/nsContentSecurityManager.cpp
index 298dc810e..d33f962ec 100644
--- a/dom/security/nsContentSecurityManager.cpp
+++ b/dom/security/nsContentSecurityManager.cpp
@@ -149,8 +149,16 @@ nsContentSecurityManager::CheckFTPSubresourceLoad(nsIChannel* aChannel)
   nsIPrincipal* triggeringPrincipal = loadInfo->TriggeringPrincipal();
   nsCOMPtr<nsIURI> tURI;
   triggeringPrincipal->GetURI(getter_AddRefs(tURI));
+  if (!tURI) {
+    // We don't have a triggering principal URI, meaning this isn't actually
+    // a subresource, but rather a top-level document, i.e. something we can
+    // display in-browser and might be saving as-is. Allow the load.
+    return NS_OK;
+  }
   bool isTrigFtpURI = (NS_SUCCEEDED(tURI->SchemeIs("ftp", &isTrigFtpURI)) && isTrigFtpURI);
   if (isTrigFtpURI) {
+    // The document loading this resource is also on FTP, satisfying the SOP.
+    // Allow the load.
     return NS_OK;
   }