fix: a page with an opaque origin is refused, not treated as a site (closes #527)

A page with an opaque origin, such as one its server sandboxes with a
Content-Security-Policy, is reported to the background with the origin
"null". The background took that as a site, so every such page on every
website was one site: a connection remembered for one covered them all,
and the phishing check never matched. A request whose origin is "null" is
now refused with 4100, like one with no origin, before any method runs,
and is not credited to the site its URL names. tests/rpcOrigin.test.js
sends one, and README's SiteApproval says so.

Model: opus-5-5

README.md

@@ -2080,9 +2080,12 @@ view would leave a wallet one click from deletion.
   `wallet_requestPermissions` and is on neither the allowed nor the denied list.
   A site is its full origin, `scheme://host[:port]`, on both lists and for a
   connection allowed without "Remember": a choice for `https://dapp.example`
-  says nothing about `http://dapp.example` or another port of that host. The
-  background script prefers the toolbar popup (`action.openPopup()`) and falls
-  back to a separate popup window (`src/background/index.js`,
+  says nothing about `http://dapp.example` or another port of that host. A page
+  with an opaque origin, such as one its server sandboxes with a
+  Content-Security-Policy, is reported with the origin `null`, which is no site:
+  every request from it is refused with EIP-1193 code `4100` and opens no
+  prompt. The background script prefers the toolbar popup (`action.openPopup()`)
+  and falls back to a separate popup window (`src/background/index.js`,
   `requestApproval()`). Only one exists per site at a time: a further connection
   request from a site whose prompt is still unanswered is refused with EIP-1193
   code `-32002` and opens no new prompt. If that prompt was in a toolbar popup

src/background/index.js

@@ -1428,6 +1428,11 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
         // the origin of sender.url is used: the frame that sent the message,
         // not the tab's page, which may be another site embedding that
         // frame. With neither, the request is refused.
+        //
+        // A page with an opaque origin, such as one its server sandboxes with
+        // a Content-Security-Policy, is reported with the origin "null". That
+        // is no site, so the request is refused too, and not credited to the
+        // site its URL names.
         let trustedOrigin = sender.origin;
         if (!trustedOrigin && sender.url) {
             try {
@@ -1436,7 +1441,7 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 // an unparseable URL leaves the origin unknown
             }
         }
-        if (!trustedOrigin) {
+        if (!trustedOrigin || trustedOrigin === "null") {
             sendResponse({
                 error: {
                     code: 4100,

tests/rpcOrigin.test.js

@@ -8,8 +8,14 @@
 // and a request the browser said nothing about was credited to whatever the
 // page wrote (https://git.eeqj.de/sneak/AutistMask/issues/407).
 //
-// Every sender here lacks sender.origin, as on old Firefox. The connection
-// check on eth_accounts is what shows which site a request was credited to.
+// A page with an opaque origin, such as one its server sandboxes with a
+// Content-Security-Policy, is reported with the origin "null". That names no
+// site, so its request is refused
+// (https://git.eeqj.de/sneak/AutistMask/issues/527).
+//
+// Every other sender here lacks sender.origin, as on old Firefox. The
+// connection check on eth_accounts is what shows which site a request was
+// credited to.
 
 const { makeStorageStub } = require("./support/storageStub");
 
@@ -144,3 +150,23 @@ describe("a request the browser does not say the sender of", () => {
         });
     });
 });
+
+describe("a request from a page with an opaque origin", () => {
+    test("is refused, whatever the page's URL says", async () => {
+        const accounts = loadBackground();
+
+        const result = await accounts({
+            origin: "null",
+            url: CONNECTED_ORIGIN + "/sandboxed.html",
+            tab: { url: CONNECTED_ORIGIN + "/sandboxed.html" },
+        });
+
+        expect(result).toEqual({
+            error: {
+                code: 4100,
+                message:
+                    "The wallet could not tell which site sent this request.",
+            },
+        });
+    });
+});