harden: lost-password confirmation refuses empty input and ignores invisible characters (closes #336)

A wallet named only with spaces compared equal to an empty field, so
typing nothing would have deleted it, and a zero-width space in a name
made the name impossible to type back.

An empty typed confirmation is now refused whatever the name is. The
characters src/shared/symbolSpoof.js already defines as painting nothing
are removed from both sides before comparing. A name that shows nothing
at all is shown on the delete screens as "Wallet N", so it can still be
typed back.

Model: opus-5-5

src/popup/views/deleteWallet.js

@@ -12,6 +12,7 @@ const {
     removeWalletFromState,
     broadcastActiveChanged,
 } = require("../../shared/walletDelete");
+const { INVISIBLE_CHARACTERS } = require("../../shared/symbolSpoof");
 
 let deleteWalletIndex = null;
 let lostPasswordIndex = null;
@@ -20,21 +21,31 @@ let ctx = null;
 // The name shown for a wallet, and on the lost-password screen the string
 // the user has to type back. One function so the two cannot disagree: a
 // confirmation that asks for a name other than the one on screen is
-// unusable.
+// unusable. A name that shows nothing at all (only spaces, or only
+// zero-width characters) is replaced by "Wallet N" for the same reason:
+// there would be nothing on screen to type back.
 function displayName(walletIdx) {
     const wallet = state.wallets[walletIdx];
-    return (wallet && wallet.name) || "Wallet " + (walletIdx + 1);
+    const name = wallet && wallet.name;
+    if (name && confirmKey(name)) return name;
+    return "Wallet " + (walletIdx + 1);
 }
 
 // What the typed confirmation and the wallet name are compared as. HTML
 // collapses runs of whitespace when it renders the name, so a wallet named
 // "My  Wallet" with two spaces DISPLAYS as "My Wallet": the user cannot
 // see the second space and cannot type a string that matches the stored
-// name. Comparing collapsed on both sides is what keeps the confirmation
-// satisfiable, on the one screen whose whole purpose is unwedging a user
-// who is already stuck. Case and surrounding space go the same way.
+// name. Characters that paint nothing, such as a zero-width space, are
+// invisible the same way and are removed first. Comparing this form on
+// both sides is what keeps the confirmation satisfiable, on the one screen
+// whose whole purpose is unwedging a user who is already stuck. Case and
+// surrounding space go the same way.
 function confirmKey(name) {
-    return name.trim().replace(/\s+/g, " ").toLowerCase();
+    return name
+        .replace(INVISIBLE_CHARACTERS, "")
+        .trim()
+        .replace(/\s+/g, " ")
+        .toLowerCase();
 }
 
 // Drop the password from the DOM and the wallet selection from the
@@ -174,14 +185,16 @@ function init(_ctx) {
             return;
         }
 
-        // Case, surrounding spaces and repeated inner spaces are not part
-        // of the confirmation; see confirmKey(). This asks whether the
-        // user knows which wallet they are on; it is not a secret, and
-        // refusing "wallet 2" for "Wallet 2" would only teach the user to
-        // distrust the control.
-        const typed = $("delete-wallet-lost-name-input").value;
+        // Case, surrounding spaces, repeated inner spaces and invisible
+        // characters are not part of the confirmation; see confirmKey().
+        // This asks whether the user knows which wallet they are on; it is
+        // not a secret, and refusing "wallet 2" for "Wallet 2" would only
+        // teach the user to distrust the control. An empty field is
+        // refused whatever the wallet is called, so no stored name can
+        // ever be confirmed by typing nothing.
+        const typed = confirmKey($("delete-wallet-lost-name-input").value);
         const expected = displayName(lostPasswordIndex);
-        if (confirmKey(typed) !== confirmKey(expected)) {
+        if (typed === "" || typed !== confirmKey(expected)) {
             $("delete-wallet-lost-flash").textContent =
                 "That is not the name of this wallet. Type " +
                 expected +