fix(bridge-ui): fix USDT approvals

packages/bridge-ui/src/components/Bridge/SharedBridgeComponents/Actions.svelte

@@ -2,6 +2,7 @@
   import { onMount } from 'svelte';
   import { t } from 'svelte-i18n';
 
+  import { Alert } from '$components/Alert';
   import {
     allApproved,
     computingBalance,
@@ -10,6 +11,7 @@
     errorComputingBalance,
     insufficientAllowance,
     insufficientBalance,
+    needsApprovalReset,
     recipientAddress,
     selectedToken,
     tokenBalance,
@@ -24,9 +26,11 @@
 
   export let approve: () => Promise<void>;
   export let bridge: () => Promise<void>;
+  export let resetApproval: () => Promise<void>;
 
   export let approving = false;
   export let bridging = false;
+  export let resetting = false;
 
   export let disabled = false;
 
@@ -47,6 +51,12 @@
     bridge();
   }
 
+  const onResetApproveClick = async () => {
+    resetting = true;
+    await resetApproval();
+    resetting = false;
+  };
+
   onMount(async () => {
     if ($selectedToken) {
       $allApproved = false;
@@ -85,6 +95,11 @@
 
   $: validApprovalStatus = $allApproved;
 
+  // USDT specific, L1 address of USDT contract
+  $: resetRequired =
+    $selectedToken?.addresses[$connectedSourceChain.id] === '0xdAC17F958D2ee523a2206206994597C13D831ec7' &&
+    $needsApprovalReset;
+
   $: commonConditions =
     validApprovalStatus &&
     !bridging &&
@@ -106,6 +121,8 @@
 
   $: ethConditionsSatisfied = commonConditions && $enteredAmount && $enteredAmount > 0;
 
+  $: disableReset = !resetRequired || resetting;
+
   $: disableBridge = isERC20
     ? !erc20ConditionsSatisfied
     : isERC721
@@ -119,24 +136,42 @@
 
 <div class="f-col w-full gap-4">
   {#if $selectedToken && !isETH}
-    <ActionButton
-      priority="primary"
-      disabled={disableApprove}
-      loading={approving || $validatingAmount || checking}
-      on:click={onApproveClick}>
-      {#if approving}
-        <span class="body-bold">{$t('bridge.button.approving')}</span>
-      {:else if $allApproved}
-        <div class="f-items-center">
-          <Icon type="check" />
-          <span class="body-bold">{$t('bridge.button.approved')}</span>
-        </div>
-      {:else if checking}
-        <span class="body-bold">{$t('bridge.button.validating')}</span>
-      {:else}
-        <span class="body-bold">{$t('bridge.button.approve')}</span>
-      {/if}
-    </ActionButton>
+    {#if resetRequired}
+      <Alert type="info">{$t('bridge.usdt_approval.info')}</Alert>
+      <ActionButton priority="primary" disabled={disableReset} loading={resetting} on:click={onResetApproveClick}>
+        {#if resetting}
+          <span class="body-bold">{$t('bridge.button.resetting')}</span>
+        {:else if $allApproved}
+          <div class="f-items-center">
+            <Icon type="check" />
+            <span class="body-bold">{$t('bridge.button.reset')}</span>
+          </div>
+        {:else if checking}
+          <span class="body-bold">{$t('bridge.button.validating')}</span>
+        {:else}
+          <span class="body-bold">{$t('bridge.button.reset_approval')}</span>
+        {/if}
+      </ActionButton>
+    {:else}
+      <ActionButton
+        priority="primary"
+        disabled={disableApprove}
+        loading={approving || $validatingAmount || checking}
+        on:click={onApproveClick}>
+        {#if approving}
+          <span class="body-bold">{$t('bridge.button.approving')}</span>
+        {:else if $allApproved}
+          <div class="f-items-center">
+            <Icon type="check" />
+            <span class="body-bold">{$t('bridge.button.approved')}</span>
+          </div>
+        {:else if checking}
+          <span class="body-bold">{$t('bridge.button.validating')}</span>
+        {:else}
+          <span class="body-bold">{$t('bridge.button.approve')}</span>
+        {/if}
+      </ActionButton>
+    {/if}
   {/if}
   <ActionButton priority="primary" disabled={disableBridge} loading={bridging} on:click={onBridgeClick}>
     {#if bridging}

packages/bridge-ui/src/components/Bridge/SharedBridgeComponents/ConfirmationStep/ConfirmationStep.svelte

@@ -48,6 +48,7 @@
   let bridging: boolean;
   let approving: boolean;
   let checking: boolean;
+  let resetting: boolean;
 
   let icon: IconType;
 
@@ -173,6 +174,25 @@
     }
   };
 
+  async function resetApproval() {
+    if (!$selectedToken || !$connectedSourceChain || !$destNetwork?.id) return;
+    try {
+      let tokenAddress = $selectedToken.addresses[$connectedSourceChain.id];
+      const type: TokenType = $selectedToken.type;
+
+      const spenderAddress = routingContractsMap[$connectedSourceChain.id][$destNetwork?.id].erc20VaultAddress;
+      const walletClient = await getConnectedWallet($connectedSourceChain.id);
+
+      const args: ApproveArgs = { tokenAddress, spenderAddress, wallet: walletClient, amount: 0n };
+      approveTxHash = await (bridges[type] as ERC20Bridge).approve(args, true);
+
+      if (approveTxHash) await handleApproveTxHash(approveTxHash);
+    } catch (err) {
+      console.error(err);
+      handleBridgeError(err as Error);
+    }
+  }
+
   async function approve() {
     isBridgePaused().then((paused) => {
       if (paused) throw new BridgePausedError('Bridge is paused');
@@ -301,7 +321,7 @@
   {#if bridgingStatus === BridgingStatus.PENDING}
     <section id="actions" class="f-col w-full">
       <div class="h-sep mb-[30px]" />
-      <Actions {approve} {bridge} bind:bridging bind:approving bind:checking />
+      <Actions {approve} {bridge} bind:bridging bind:approving bind:checking bind:resetting {resetApproval} />
     </section>
   {/if}
 </div>

packages/bridge-ui/src/components/Bridge/state.ts

@@ -49,6 +49,7 @@ export const insufficientBalance = writable<boolean>(false);
 export const insufficientAllowance = writable<boolean>(false);
 
 export const allApproved = writable(<boolean>false);
+export const needsApprovalReset = writable<boolean>(false);
 
 // Derived state
 export const bridgeService = derived(selectedToken, (token) => (token ? bridges[token.type] : null));

packages/bridge-ui/src/i18n/en.json

@@ -53,6 +53,9 @@
       "bridging": "Bridging",
       "fetch": "Fetch NFT data",
       "import": "Import",
+      "reset": "Reset",
+      "reset_approval": "Reset Approval",
+      "resetting": "Resetting",
       "validating": "Validating..."
     },
     "description": {
@@ -205,6 +208,9 @@
         "recipient": "Recipient",
         "review": "Review"
       }
+    },
+    "usdt_approval": {
+      "info": "You have previously approved a lower amount of USDT. To adjust the approval, you must first reset the previous amount to 0. This requirement is unique to USDT."
     }
   },
   "chain_selector": {

packages/bridge-ui/src/libs/bridge/ERC20Bridge.ts

@@ -111,7 +111,7 @@ export class ERC20Bridge extends Bridge {
     return estimatedGas;
   }
 
-  async requireAllowance({ amount, tokenAddress, ownerAddress, spenderAddress }: RequireAllowanceArgs) {
+  async getAllowance({ amount, tokenAddress, ownerAddress, spenderAddress }: RequireAllowanceArgs) {
     isBridgePaused().then((paused) => {
       if (paused) throw new BridgePausedError('Bridge is paused');
     });
@@ -125,33 +125,65 @@ export class ERC20Bridge extends Bridge {
       chainId: (await getConnectedWallet()).chain.id,
     });
 
+    return allowance;
+  }
+  async requireAllowance({ amount, tokenAddress, ownerAddress, spenderAddress }: RequireAllowanceArgs, reset = false) {
+    const allowance = await this.getAllowance({ amount, tokenAddress, ownerAddress, spenderAddress });
+
+    if (reset) {
+      return true;
+    }
     const requiresAllowance = allowance < amount;
 
     log('Allowance is', allowance, 'requires allowance?', requiresAllowance);
 
     return requiresAllowance;
   }
 
-  async approve(args: ApproveArgs) {
+  async approve(args: ApproveArgs, reset = false) {
     const { amount, tokenAddress, spenderAddress, wallet } = args;
     if (!wallet || !wallet.account) throw new Error('No wallet found');
-    const requireAllowance = await this.requireAllowance({
-      amount,
-      tokenAddress,
-      ownerAddress: wallet.account.address,
-      spenderAddress,
-    });
+    const requireAllowance = await this.requireAllowance(
+      {
+        amount,
+        tokenAddress,
+        ownerAddress: wallet.account.address,
+        spenderAddress,
+      },
+      reset,
+    );
 
     if (!requireAllowance) {
       throw new NoAllowanceRequiredError(`no allowance required for the amount ${amount}`);
     }
 
     try {
       log(`Calling approve for spender "${spenderAddress}" for token "${tokenAddress}" with amount`, amount);
+      // USDT does not play nice with the default ERC20 ABI, this works for both
+      const approvalABI = [
+        {
+          constant: false,
+          inputs: [
+            {
+              name: '_spender',
+              type: 'address',
+            },
+            {
+              name: '_value',
+              type: 'uint256',
+            },
+          ],
+          name: 'approve',
+          outputs: [],
+          payable: false,
+          stateMutability: 'nonpayable',
+          type: 'function',
+        },
+      ];
 
       const { request } = await simulateContract(config, {
         address: tokenAddress,
-        abi: erc20Abi,
+        abi: approvalABI,
         functionName: 'approve',
         args: [spenderAddress, amount],
       });

packages/bridge-ui/src/libs/token/getTokenApprovalStatus.ts

@@ -6,6 +6,7 @@ import {
   destNetwork,
   enteredAmount,
   insufficientAllowance,
+  needsApprovalReset,
   selectedToken,
 } from '$components/Bridge/state';
 import { bridges, ContractType, type RequireApprovalArgs } from '$libs/bridge';
@@ -27,6 +28,7 @@ export enum ApprovalStatus {
   ETH_NO_APPROVAL_REQUIRED,
   APPROVAL_REQUIRED,
   NO_APPROVAL_REQUIRED,
+  RESET_REQUIRED,
 }
 
 export const getTokenApprovalStatus = async (token: Maybe<Token | NFT>): Promise<ApprovalStatus> => {
@@ -57,6 +59,7 @@ export const getTokenApprovalStatus = async (token: Maybe<Token | NFT>): Promise
   }
   if (token.type === TokenType.ERC20) {
     log('checking approval status for ERC20');
+    needsApprovalReset.set(false);
 
     const tokenVaultAddress = routingContractsMap[currentChainId][destinationChainId].erc20VaultAddress;
     const bridge = bridges[TokenType.ERC20] as ERC20Bridge;
@@ -72,6 +75,19 @@ export const getTokenApprovalStatus = async (token: Maybe<Token | NFT>): Promise
       insufficientAllowance.set(requireAllowance);
       allApproved.set(!requireAllowance);
       if (requireAllowance) {
+        // specific check for USDT
+        if (get(selectedToken)?.symbol === 'tUSDT') {
+          const allowance = await bridge.getAllowance({
+            amount: get(enteredAmount),
+            tokenAddress,
+            ownerAddress,
+            spenderAddress: tokenVaultAddress,
+          });
+          if (allowance > 0n) {
+            needsApprovalReset.set(true);
+            return ApprovalStatus.RESET_REQUIRED;
+          }
+        }
         return ApprovalStatus.APPROVAL_REQUIRED;
       }
       return ApprovalStatus.NO_APPROVAL_REQUIRED;