fix: typed data with a missing field or a bool that is not true or false is refused (closes #552)

ethers signs a bool field by whether its value is truthy, so the string
"false" was shown as false and signed as true, and a bool field left out
was shown as nothing and signed as false. The sign screen now refuses
typed data whose message leaves out a declared field, at any level of
nesting, or holds a bool that is not true or false: the error line names
the field and Sign is disabled. The background refuses a signature for it
too. Presence is an own-key test, so a field named like a built-in
property such as constructor is not found by accident. signedPrimaryType()
moves to the shared module so the background reads the message as the
same type.

Model: opus-5-5

src/background/index.js

@@ -22,6 +22,8 @@ const { debugFetch, log } = require("../shared/log");
 const {
     verifySignedTx,
     verifySignature,
+    signedPrimaryType,
+    typedDataMessageRefusal,
     typedDataChainRefusal,
     failureIsRetryable,
     describeTxFailure,
@@ -1815,18 +1817,27 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                     signature,
                     approval.approvedFrom,
                 );
-                // The sign screen refuses typed data whose domain names
-                // another chain. A signature for it that arrives anyway is
-                // refused here, against the network active now.
+                // The sign screen refuses typed data whose message ethers
+                // would sign differently from how it is shown, or whose
+                // domain names another chain. A signature for it that arrives
+                // anyway is refused here, against the network active now.
                 const sp = approval.signParams;
                 if (
                     sp.method === "eth_signTypedData_v4" ||
                     sp.method === "eth_signTypedData"
                 ) {
-                    const refusal = typedDataChainRefusal(
-                        JSON.parse(sp.typedData).domain,
-                        networkById(s.networkId),
-                    );
+                    const data = JSON.parse(sp.typedData);
+                    const refusal =
+                        typedDataMessageRefusal(
+                            data.types,
+                            signedPrimaryType(data.types),
+                            data.message,
+                            "",
+                        ) ||
+                        typedDataChainRefusal(
+                            data.domain,
+                            networkById(s.networkId),
+                        );
                     if (refusal) throw new ApprovalMismatchError(refusal);
                 }
                 settleApproval(msg.id, { signature }, { holdsClaim: true });