fix: Make comparision case sensitive in MultichainRouter (#3310)

As non-EVM accounts may be case sensitive, we cannot use `toLowerCase`
for address comparision. This PR makes the `MultichainRouter` use case
sensitive comparison instead.

---------

Co-authored-by: Maarten Zuidhoorn <maarten@zuidhoorn.com>

Author: FrederikBolding

packages/snaps-controllers/src/multichain/MultichainRouter.test.ts

@@ -268,6 +268,46 @@ describe('MultichainRouter', () => {
         }),
       ).rejects.toThrow('No available account found for request.');
     });
+
+    it(`throws if address resolution returns a lower case address that isn't available`, async () => {
+      const rootMessenger = getRootMultichainRouterMessenger();
+      const messenger = getRestrictedMultichainRouterMessenger(rootMessenger);
+      const withSnapKeyring = getMockWithSnapKeyring({
+        // Simulate the Snap returning an unconnected address
+        resolveAccountAddress: jest.fn().mockResolvedValue({
+          address: `solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp:${MOCK_SOLANA_ACCOUNTS[0].address.toLowerCase()}`,
+        }),
+      });
+
+      /* eslint-disable-next-line no-new */
+      new MultichainRouter({
+        messenger,
+        withSnapKeyring,
+      });
+
+      rootMessenger.registerActionHandler(
+        'AccountsController:listMultichainAccounts',
+        () => MOCK_SOLANA_ACCOUNTS,
+      );
+
+      rootMessenger.registerActionHandler(
+        'PermissionController:getPermissions',
+        () => MOCK_SOLANA_SNAP_PERMISSIONS,
+      );
+
+      await expect(
+        messenger.call('MultichainRouter:handleRequest', {
+          connectedAddresses: SOLANA_CONNECTED_ACCOUNTS,
+          scope: SOLANA_CAIP2,
+          request: {
+            method: 'signAndSendTransaction',
+            params: {
+              message: 'foo',
+            },
+          },
+        }),
+      ).rejects.toThrow('No available account found for request.');
+    });
   });
 
   describe('getSupportedMethods', () => {

packages/snaps-controllers/src/multichain/MultichainRouter.ts

@@ -218,7 +218,7 @@ export class MultichainRouter {
     const selectedAccount = accounts.find(
       (account) =>
         parsedConnectedAddresses.includes(account.address) &&
-        (!address || account.address.toLowerCase() === address.toLowerCase()),
+        (!address || account.address === address),
     );
 
     if (!selectedAccount) {
@@ -268,6 +268,9 @@ export class MultichainRouter {
    * Handle an incoming JSON-RPC request tied to a specific scope by routing
    * to either a procotol Snap or an account Snap.
    *
+   * Note: Addresses are considered case sensitive by the MultichainRouter as
+   * not all non-EVM chains are case insensitive.
+   *
    * @param options - An options bag.
    * @param options.connectedAddresses - Addresses currently connected to the origin.
    * @param options.origin - The origin of the RPC request.