improvement(#1043): do not allow swapping to bad addresses

src/hooks/useENSAddress.ts

 import { namehash } from 'ethers/lib/utils'
 import { useMemo } from 'react'
 import { useSingleCallResult } from '../state/multicall/hooks'
+import isZero from '../utils/isZero'
 import { useENSRegistrarContract, useENSResolverContract } from './useContract'
 import useDebounce from './useDebounce'
 
@@ -19,7 +20,11 @@ export default function useENSAddress(ensName?: string | null): { loading: boole
   }, [debouncedName])
   const registrarContract = useENSRegistrarContract(false)
   const resolverAddress = useSingleCallResult(registrarContract, 'resolver', ensNodeArgument)
-  const resolverContract = useENSResolverContract(resolverAddress.result?.[0], false)
+  const resolverAddressResult = resolverAddress.result?.[0]
+  const resolverContract = useENSResolverContract(
+    resolverAddressResult && !isZero(resolverAddressResult) ? resolverAddressResult : undefined,
+    false
+  )
   const addr = useSingleCallResult(resolverContract, 'addr', ensNodeArgument)
 
   const changed = debouncedName !== ensName

src/state/swap/hooks.ts

@@ -88,6 +88,24 @@ export function tryParseAmount(value?: string, currency?: Currency): CurrencyAmo
   return
 }
 
+const BAD_RECIPIENT_ADDRESSES: string[] = [
+  '0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f', // v2 factory
+  '0xf164fC0Ec4E93095b804a4795bBe1e041497b92a', // v2 router 01
+  '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D' // v2 router 02
+]
+
+/**
+ * Returns true if any of the pairs or tokens in a trade have the given checksummed address
+ * @param trade to check for the given address
+ * @param checksummedAddress address to check in the pairs and tokens
+ */
+function involvesAddress(trade: Trade, checksummedAddress: string): boolean {
+  return (
+    trade.route.path.some(token => token.address === checksummedAddress) ||
+    trade.route.pairs.some(pair => pair.liquidityToken.address === checksummedAddress)
+  )
+}
+
 // from the current swap inputs, compute the best trade and return it.
 export function useDerivedSwapInfo(): {
   currencies: { [field in Field]?: Currency }
@@ -153,8 +171,17 @@ export function useDerivedSwapInfo(): {
     inputError = inputError ?? 'Select a token'
   }
 
-  if (!to) {
+  const formattedTo = isAddress(to)
+  if (!to || !formattedTo) {
     inputError = inputError ?? 'Enter a recipient'
+  } else {
+    if (
+      BAD_RECIPIENT_ADDRESSES.indexOf(formattedTo) !== -1 ||
+      (bestTradeExactIn && involvesAddress(bestTradeExactIn, formattedTo)) ||
+      (bestTradeExactOut && involvesAddress(bestTradeExactOut, formattedTo))
+    ) {
+      inputError = inputError ?? 'Invalid recipient'
+    }
   }
 
   const [allowedSlippage] = useUserSlippageTolerance()