Independent paymaster mode validation

contracts/common/BiconomyTokenPaymasterErrors.sol

@@ -37,6 +37,11 @@ contract BiconomyTokenPaymasterErrors {
      */
     error TokensAndInfoLengthMismatch();
 
+    /**
+     * @notice Throws when invalid PaymasterMode specified in paymasterAndData
+     */
+    error InvalidPaymasterMode();
+
     /**
      * @notice Throws when oracle returns invalid price
      */
@@ -46,4 +51,14 @@ contract BiconomyTokenPaymasterErrors {
      * @notice Throws when oracle price hasn't been updated for a duration of time the owner is comfortable with
      */
     error OraclePriceExpired();
+
+    /**
+     * @notice Throws when token address to pay with is invalid
+     */
+    error InvalidTokenAddress();
+
+    /**
+     * @notice Throws when user tries to pay with an unsupported token
+     */
+    error TokenNotSupported();
 }

contracts/interfaces/IBiconomyTokenPaymaster.sol

@@ -4,6 +4,11 @@ pragma solidity ^0.8.26;
 import { IOracle } from "./oracles/IOracle.sol";
 
 interface IBiconomyTokenPaymaster {
+    enum PaymasterMode {
+        EXTERNAL,
+        INDEPENDENT
+    }
+
     // Struct for storing information about the token
     struct TokenInfo {
         IOracle oracle;
@@ -30,5 +35,5 @@ interface IBiconomyTokenPaymaster {
 
     function setPriceExpiryDuration(uint256 _newPriceExpiryDuration) external payable;
 
-    function setTokenInfo(address _tokenAddress, IOracle _oracle, uint8 _decimals) external payable;
+    function setTokenInfo(address _tokenAddress, IOracle _oracle) external payable;
 }

contracts/libraries/PaymasterParser.sol

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-3.0
+pragma solidity ^0.8.26;
+
+import { IBiconomyTokenPaymaster } from "../interfaces/IBiconomyTokenPaymaster.sol";
+import "@account-abstraction/contracts/core/UserOperationLib.sol";
+
+// A helper library to parse paymaster and data
+library PaymasterParser {
+    uint256 private constant PAYMASTER_MODE_OFFSET = UserOperationLib.PAYMASTER_DATA_OFFSET; // Start offset of mode in
+        // PND
+
+    function parsePaymasterAndData(bytes calldata paymasterAndData)
+        external
+        pure
+        returns (IBiconomyTokenPaymaster.PaymasterMode mode, bytes memory modeSpecificData)
+    {
+        unchecked {
+            mode = IBiconomyTokenPaymaster.PaymasterMode(
+                uint8(bytes1(paymasterAndData[PAYMASTER_MODE_OFFSET:PAYMASTER_MODE_OFFSET + 8]))
+            );
+            modeSpecificData = paymasterAndData[PAYMASTER_MODE_OFFSET + 8:];
+        }
+    }
+
+    function parseExternalModeSpecificData(bytes calldata modeSpecificData) external pure { }
+
+    function parseIndependentModeSpecificData(bytes calldata modeSpecificData)
+        external
+        pure
+        returns (address tokenAddress)
+    {
+        tokenAddress = address(bytes20(modeSpecificData[:20]));
+    }
+}

contracts/token/BiconomyTokenPaymaster.sol

@@ -4,12 +4,14 @@ pragma solidity ^0.8.26;
 import { ReentrancyGuardTransient } from "@openzeppelin/contracts/utils/ReentrancyGuardTransient.sol";
 import { IEntryPoint } from "@account-abstraction/contracts/interfaces/IEntryPoint.sol";
 import { PackedUserOperation, UserOperationLib } from "@account-abstraction/contracts/core/UserOperationLib.sol";
-import { IERC20, ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { IERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { IERC20Metadata } from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
 import { SafeTransferLib } from "@solady/src/utils/SafeTransferLib.sol";
 import { BasePaymaster } from "../base/BasePaymaster.sol";
 import { BiconomyTokenPaymasterErrors } from "../common/BiconomyTokenPaymasterErrors.sol";
 import { IBiconomyTokenPaymaster } from "../interfaces/IBiconomyTokenPaymaster.sol";
 import { IOracle } from "../interfaces/oracles/IOracle.sol";
+import { PaymasterParser } from "../libraries/PaymasterParser.sol";
 import "@account-abstraction/contracts/core/Helpers.sol";
 
 /**
@@ -18,8 +20,9 @@ import "@account-abstraction/contracts/core/Helpers.sol";
  * @author livingrockrises<chirag@biconomy.io>
  * @notice Token Paymaster for Entry Point v0.7
  * @dev  A paymaster that allows user to pay gas fees in ERC20 tokens. The paymaster uses the precharge and refund model
- * to handle gas remittances. For fair and "always available" operation, it relies on price oracles which
- * implement the IOracle interface to calculate the gas cost of the transaction in a supported token. The owner has full
+ * to handle gas remittances. For fair and "always available" operation, it supports a mode that relies purely on price
+ * oracles (Offchain and TWAP) which
+ * implement the IOracle interface to calculate the token cost of a transaction. The owner has full
  * discretion over the supported tokens, premium and discounts applied (if any), and how to manage the assets
  * received by the paymaster. The properties described above, make the paymaster self-relaint: independent of any
  * offchain service for use.
@@ -31,6 +34,7 @@ contract BiconomyTokenPaymaster is
     IBiconomyTokenPaymaster
 {
     using UserOperationLib for PackedUserOperation;
+    using PaymasterParser for bytes;
 
     // State variables
     address public feeCollector;
@@ -40,9 +44,9 @@ contract BiconomyTokenPaymaster is
     IOracle public nativeOracle; // ETH -> USD price
     mapping(address => TokenInfo) tokenDirectory;
 
-    // Limit for unaccounted gas cost
-    uint256 private constant UNACCOUNTED_GAS_LIMIT = 50_000;
-    uint256 private constant PRICE_DENOMINATOR = 1e6;
+    // PAYMASTER_ID_OFFSET
+    uint256 private constant UNACCOUNTED_GAS_LIMIT = 50_000; // Limit for unaccounted gas cost
+    uint256 private constant PRICE_DENOMINATOR = 1e6; // Denominator used when calculating cost with dynamic adjustment
     uint256 private constant MAX_DYNAMIC_ADJUSTMENT = 2e6; // 100% premium on price (2e6/PRICE_DENOMINATOR)
 
     constructor(
@@ -53,7 +57,6 @@ contract BiconomyTokenPaymaster is
         IOracle _nativeOracle,
         uint256 _priceExpiryDuration,
         address[] memory _tokens, // Array of token addresses
-        uint8[] memory _decimals, // Array of corresponding token decimals
         IOracle[] memory _oracles // Array of corresponding oracle addresses
     )
         BasePaymaster(_owner, _entryPoint)
@@ -62,19 +65,20 @@ contract BiconomyTokenPaymaster is
             revert UnaccountedGasTooHigh();
         } else if (_dynamicAdjustment > MAX_DYNAMIC_ADJUSTMENT || _dynamicAdjustment == 0) {
             revert InvalidDynamicAdjustment();
-        } else if (_tokens.length != _oracles.length || _tokens.length != _decimals.length) {
+        } else if (_tokens.length != _oracles.length) {
             revert TokensAndInfoLengthMismatch();
         }
         assembly ("memory-safe") {
             sstore(feeCollector.slot, address()) // initialize fee collector to this contract
             sstore(unaccountedGas.slot, _unaccountedGas)
             sstore(dynamicAdjustment.slot, _dynamicAdjustment)
+            sstore(priceExpiryDuration.slot, _priceExpiryDuration)
             sstore(nativeOracle.slot, _nativeOracle)
         }
 
         // Populate the tokenToOracle mapping
         for (uint256 i = 0; i < _tokens.length; i++) {
-            tokenDirectory[_tokens[i]] = TokenInfo(_oracles[i], _decimals[i]);
+            tokenDirectory[_tokens[i]] = TokenInfo(_oracles[i], IERC20Metadata(_tokens[i]).decimals());
         }
     }
 
@@ -232,21 +236,12 @@ contract BiconomyTokenPaymaster is
      * @dev Set or update a TokenInfo entry in the tokenDirectory mapping.
      * @param _tokenAddress The new value to be set as the unaccounted gas value
      * @param _oracle The new value to be set as the unaccounted gas value
-     * @param _decimals The new value to be set as the unaccounted gas value
      * @notice only to be called by the owner of the contract.
      */
-    function setTokenInfo(
-        address _tokenAddress,
-        IOracle _oracle,
-        uint8 _decimals
-    )
-        external
-        payable
-        override
-        onlyOwner
-    {
-        tokenDirectory[_tokenAddress] = TokenInfo(_oracle, _decimals);
-        emit UpdatedTokenDirectory(_tokenAddress, _oracle, _decimals);
+    function setTokenInfo(address _tokenAddress, IOracle _oracle) external payable override onlyOwner {
+        uint8 decimals = IERC20Metadata(_tokenAddress).decimals();
+        tokenDirectory[_tokenAddress] = TokenInfo(_oracle, decimals);
+        emit UpdatedTokenDirectory(_tokenAddress, _oracle, decimals);
     }
 
     /**
@@ -264,7 +259,41 @@ contract BiconomyTokenPaymaster is
         internal
         override
         returns (bytes memory context, uint256 validationData)
-    { }
+    {
+        (PaymasterMode mode, bytes memory modeSpecificData) = userOp.paymasterAndData.parsePaymasterAndData();
+
+        if (uint8(mode) > 1) {
+            revert InvalidPaymasterMode();
+        }
+
+        if (mode == PaymasterMode.EXTERNAL) {
+            // Use the price and other params specified in modeSpecificData by the verifyingSigner
+            // Useful for supporting tokens which don't have oracle support
+        } else if (mode == PaymasterMode.INDEPENDENT) {
+            // Use only oracles for the token specified in modeSpecificData
+            if (modeSpecificData.length != 20) {
+                revert InvalidTokenAddress();
+            }
+
+            // Get address for token used to pay
+            address tokenAddress = modeSpecificData.parseIndependentModeSpecificData();
+            uint192 tokenPrice = getPrice(tokenAddress);
+            uint256 tokenAmount;
+
+            {
+                // Calculate token amount to precharge
+                uint256 maxFeePerGas = UserOperationLib.unpackMaxFeePerGas(userOp);
+                tokenAmount = (maxCost + (unaccountedGas) * maxFeePerGas) * dynamicAdjustment * tokenPrice
+                    / (1e18 * PRICE_DENOMINATOR);
+            }
+
+            // Transfer full amount to this address. Unused amount will be refunded in postOP
+            SafeTransferLib.safeTransferFrom(tokenAddress, userOp.sender, address(this), tokenAmount);
+
+            context = abi.encodePacked(tokenAmount, tokenPrice, userOp.sender, userOpHash);
+            validationData = 0;
+        }
+    }
 
     /**
      * @dev Post-operation handler.
@@ -292,14 +321,19 @@ contract BiconomyTokenPaymaster is
     }
 
     /// @notice Fetches the latest token price.
-
     /// @return price The latest token price fetched from the oracles.
-    function getPrice(address tokenAddress) internal view returns (uint192) {
+    function getPrice(address tokenAddress) internal view returns (uint192 price) {
         TokenInfo memory tokenInfo = tokenDirectory[tokenAddress];
+
+        if (address(tokenInfo.oracle) == address(0)) {
+            // If oracle not set, token isn't supported
+            revert TokenNotSupported();
+        }
+
         uint192 tokenPrice = _fetchPrice(tokenInfo.oracle);
         uint192 nativeAssetPrice = _fetchPrice(nativeOracle);
-        uint192 price = nativeAssetPrice * uint192(tokenInfo.decimals) / tokenPrice;
-        return price;
+
+        price = nativeAssetPrice * uint192(tokenInfo.decimals) / tokenPrice;
     }
 
     /// @notice Fetches the latest price from the given oracle.

contracts/token/oracles/TwapOracle.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.8.23;
+pragma solidity ^0.8.26;
 
 import {IOracle} from "../../interfaces/oracles/IOracle.sol";
 import {IERC20Metadata} from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";