fix: Blockscout and Etherscan lookups are off until the user turns them on (closes #668)

Out of the box the wallet sent the user's addresses to Blockscout for history
and token lookups, and each recipient to Etherscan for its label. Two settings,
"Use Blockscout" and "Check recipients on Etherscan", now gate those requests
where they are made. Both are off in a new profile and offered unticked on
Welcome and in Settings. While one is off, the screens that relied on it say so
in a plain line naming the setting; after either changes in Settings, Back
draws the screen it lands on again. ENS lookups ask only the RPC endpoint, so a
name resolved off-chain does not resolve. README and the user guide say what is
contacted by default and what each setting adds.

Model: opus-5-5

README.md

@@ -2097,7 +2097,7 @@ view would leave a wallet one click from deletion.
   and raw data are read from that network's Blockscout, the one Settings has for
   it, and its etherscan links open that network's explorer. They are read only
   while "Use Blockscout" is on. The screen can still be shown with it off, when
-  the popup reopens onto it after the user turned the setting off; then
+  the user opens Settings from it, turns the setting off and presses Back; then
   Blockscout is not asked, and a line in their place says "No block, decoded
   details, network details or raw data are shown, because "Use Blockscout" is
   off in Settings."
@@ -2752,9 +2752,12 @@ Contacted by default:
   them the balance of every tracked token at every address (`balanceOf`),
   estimate gas (`eth_estimateGas`), fetch nonces (`eth_getTransactionCount`),
   broadcast transactions (`eth_sendRawTransaction`), and check transaction
-  receipts. The default endpoint is a public RPC (configurable by the user to
+  receipts. ENS lookups, of a name typed into Send and of the names shown for
-  any endpoint they prefer, including a local node). By default the extension
+  the user's addresses, are made through it alone, so a name whose resolver says
-  talks to `https://ethereum-rpc.publicnode.com`.
+  it is resolved off-chain does not resolve. The default endpoint is a public
+  RPC (configurable by the user to any endpoint they prefer, including a local
+  node). By default the extension talks to
+  `https://ethereum-rpc.publicnode.com`.
     - **Data sent**: Ethereum addresses, transaction data, contract call
       parameters. The RPC endpoint can see all on-chain queries and submitted
       transactions.

src/shared/balances.js

@@ -38,9 +38,18 @@ const { resolveTokenDecimals } = require("./approvalAmount");
 // ethers knows chains this wallet does not, so an id that is not one of ours
 // is a caller bug and must not resolve to a working provider for some other
 // chain.
+//
+// `disableCcipRead` keeps every ENS lookup on the RPC endpoint. Left on, as
+// ethers has it, a resolver that says a name is resolved off-chain makes ethers
+// fetch the web address the resolver gives, straight from the browser, with the
+// name being looked up; for the reverse lookup of the user's addresses that is
+// the user's own name (https://git.eeqj.de/sneak/AutistMask/issues/668). Such a
+// name does not resolve.
 function getProvider(rpcUrl, networkId) {
     const net = Network.from(requireNetworkId(networkId).id);
-    return new JsonRpcProvider(rpcUrl, net, { staticNetwork: net });
+    const provider = new JsonRpcProvider(rpcUrl, net, { staticNetwork: net });
+    provider.disableCcipRead = true;
+    return provider;
 }
 
 function requireNetworkId(networkId) {

tests/ensOffchainLookup.test.js

@@ -0,0 +1,111 @@
+// ENS lookups ask nothing but the RPC endpoint. A resolver can answer that a
+// name is resolved off-chain, naming a web address to fetch the answer from;
+// ethers fetches it unless the provider has `disableCcipRead` set, and that
+// request would carry the name to a server other than the RPC endpoint
+// (https://git.eeqj.de/sneak/AutistMask/issues/668). With it set, such a name
+// does not resolve.
+//
+// The provider getProvider() builds runs against a fake JSON-RPC node,
+// answered through ethers' own request hook, which also records the address of
+// every request ethers makes, the off-chain fetch included.
+
+const { FetchRequest, Interface } = require("ethers");
+const { getProvider } = require("../src/shared/balances");
+
+const RPC_URL = "https://rpc.example.invalid";
+const RESOLVER = "0x5555555555555555555555555555555555555555";
+const USER = "0x1111111111111111111111111111111111111111";
+const NAME = "offchain.eth";
+
+// The ENS registry's resolver(), and the resolver's functions ethers calls: the
+// registry names RESOLVER for every name, the resolver says it resolves names
+// through resolve(), gives NAME as the reverse record of any address, and
+// answers resolve() with the OffchainLookup error that says the name is
+// resolved off-chain.
+const ens = new Interface([
+    "function resolver(bytes32) view returns (address)",
+    "function supportsInterface(bytes4) view returns (bool)",
+    "function name(bytes32) view returns (string)",
+    "function resolve(bytes, bytes) view returns (bytes)",
+    "error OffchainLookup(address sender, string[] urls, bytes callData, bytes4 callbackFunction, bytes extraData)",
+]);
+
+let asked;
+
+// One JSON-RPC answer. Anything but a call to one of the functions above is
+// refused.
+function reply(req) {
+    const envelope = { jsonrpc: "2.0", id: req.id };
+    const call =
+        req.method === "eth_call" ? ens.parseTransaction(req.params[0]) : null;
+    if (call === null) {
+        return {
+            ...envelope,
+            error: { code: -32601, message: "method not found" },
+        };
+    }
+    if (call.name === "resolve") {
+        const offchain = ens.encodeErrorResult("OffchainLookup", [
+            RESOLVER,
+            ["https://gateway.example.invalid/{sender}/{data}.json"],
+            "0x1234",
+            "0x12345678",
+            "0x",
+        ]);
+        return {
+            ...envelope,
+            error: { code: 3, message: "execution reverted", data: offchain },
+        };
+    }
+    const answers = {
+        resolver: [RESOLVER],
+        supportsInterface: [true],
+        name: [NAME],
+    };
+    return {
+        ...envelope,
+        result: ens.encodeFunctionResult(call.name, answers[call.name]),
+    };
+}
+
+beforeEach(() => {
+    asked = [];
+    FetchRequest.registerGetUrl(async (req) => {
+        asked.push(req.url);
+        // Any other address is the off-chain fetch, answered as not found.
+        if (req.url !== RPC_URL) {
+            return {
+                statusCode: 404,
+                statusMessage: "Not Found",
+                headers: {},
+                body: null,
+            };
+        }
+        const body = JSON.parse(Buffer.from(req.body).toString("utf8"));
+        const answer = Array.isArray(body) ? body.map(reply) : reply(body);
+        return {
+            statusCode: 200,
+            statusMessage: "OK",
+            headers: { "content-type": "application/json" },
+            body: Buffer.from(JSON.stringify(answer)),
+        };
+    });
+});
+
+afterEach(() => {
+    FetchRequest.registerGetUrl(FetchRequest.createGetUrlFunc());
+});
+
+test("a name typed into Send that is resolved off-chain does not resolve, and only the RPC endpoint is asked", async () => {
+    const provider = getProvider(RPC_URL, "mainnet");
+    const [outcome] = await Promise.allSettled([provider.resolveName(NAME)]);
+    expect(asked.filter((url) => url !== RPC_URL)).toEqual([]);
+    expect(outcome).toEqual({ status: "fulfilled", value: null });
+});
+
+test("the reverse lookup of a user's address whose name is resolved off-chain finds no name, and only the RPC endpoint is asked", async () => {
+    const provider = getProvider(RPC_URL, "mainnet");
+    const [outcome] = await Promise.allSettled([provider.lookupAddress(USER)]);
+    expect(asked.filter((url) => url !== RPC_URL)).toEqual([]);
+    expect(outcome).toEqual({ status: "fulfilled", value: null });
+});