​

Accessing Reown Paymaster

1. Log in to your Cloud Account here.
2. Click on your Project, then select the “Paymaster” Tab.

​

Creating a Policy

Click on “Add Policy” and follow the steps within the policy creation screen.

​

1. Select a Plan

​

Free Plan

If you select the free plan, you will have unlimited access to sponsoring on testnets. Currently, only Sepolia is supported.

​

Pay-As-You-Go

With the Pay-as-you-go plan, you will be asked to enter credit card information. You will not be billed immediately.

Instead you will be charged based on usage, with Paymaster Credits. This is calculated using a simple formula:

• amount of gas sponsored + fee

​

2. Add Policy Basic Info

1. Write a descriptive name for your policy
2. Add a start date for your policy. The current date and time are selected by default. However, you can set a future date and time to align your policy’s start with a campaign or similar event.
3. Optionally, add an end date, and your policy will automatically lapse on that date.

​

3. Select Chains

All supported chains are enabled by default, but you can deselect any chain to sponsor transactions only on specific chains.

​

Currently Supported Mainnet Chains

• Ethereum
• Polygon
• Avalanche
• Mantle
• Celo
• Optimism
• Base
• Zora
• Gnosis
• Metis

​

Currently Supported Testnet Chains

• Sepolia

​

4. Add Policy Logic

Policy logic can be updated in one of two ways:

1. No-code policy builder
2. JSON editor

There are distinct advantages to this:

1. You can maintain an auditable history of your policies by storing the JSON files for each policy.
2. You can auto-generate policies for your campaigns, as it’s a straightforward JSON schema.
3. Policies are highly flexible, allowing you to chain conditional checks to target specific smart contracts, particular methods within a contract, expected gas limits, and more.

Once created, the policy will become active immediately if the start date has already passed, making it ready for use.

​

Using the no code builder

All that is required is to

1. Input the contract address
2. Paste the ABI
3. Select the methods you wish to sponsor via the drop down
4. IMPORTANT: If you would like to sponsor the deployment of smart accounts on your app, tick the Sponsor Smart Account Deployment checkbox.

​

Sponsoring transactions

Based on EIP 5792 and ERC 7677, utilizing a paymaster is as simple as providing the paymaster RPC URL.

The Paymaster screen includes an RPC URL selector for chain-specific URLs. All URLs follow the same format, varying only by chain ID, so you can generate the URL in your Dapp based on the active chain.

​

Policy Selection

By default, all policies will be validated in succession until one returns true.

There is the option of passing policyId in the optional to the RPC. This can be sent by the dapp via the the context field per ERC 7677. However - please note that different paymasters may accept policyId with a different key or format. For Reown’s Paymaster, that key is policyId.

curl --location <YOUR_PAYMASTER_URL> \
--header 'Content-Type: application/json' \
--data '{"method":"pm_getPaymasterData","params":[{
      "sender": "0xb56e8f33dc5d32be80c32b8eb97081fa272488bb",
      "nonce": "0x3b",
      "initCode": "0x",
      "callData": "0xc32b8eb97081fa272488bb058bb8eb970870f0728eb97081fa272488bb058bb8eb970870f072445675",
      "callGasLimit": "0x0",
      "verificationGasLimit": "0x0",
      "preVerificationGas": "0x0",
      "maxFeePerGas": "0x0",
      "maxPriorityFeePerGas": "0x0"
    }, "0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789", "0x24B44",
    {
      "policyId": "298191-ff1719-5a9c-abb4-40911aa123"
    }],"jsonrpc":"2.0", "id": 1}'

​

JSON Schema: A Practical Example Walkthrough

​

Basics

The schema itself is a simple object representation of the following

Is some key from a user operation equivalent to (or some other comparison) some value?

This is defined in params as such:

{
  "key": "some_key",
  "op": "equals",
  "value": "some_value"
}

​

Chaining Conditionals

The flexibility here lies in the ability to chain different conditionals together. For example, you can check if the User Op targets a specific smart contract and a particular function within that contract’s ABI. Since these fields are encoded within a UserOp’s callData, two different methods are needed to access this information:

1. callDataMethodEquals: Verifies that the callData targets a specific function
2. callDataToEquals: Verifies that the callData targets a specific contract

Essentially, we want to combine the following two conditions:

{
  "key": "callData",
  "op": "callDataToEquals",
  "value": "0xa123cd918..."
}

{
  "key": "callData",
  "op": "callDataMethodEquals",
  "value": "methodFoo"
}

To do this, we need to zoom out and see how to set the params:

{
  // Rest of policy..

  "params": {
    "key": "callData",
    "op": "callDataToEquals",
    "value": "0xa123cd918..."
  },
  "ands": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodFoo"
      }
    }
  ]
}

The new field we introduced here is ands. The way the schema is designed, Each params object, can be accompanied with an ands OR an ors field which is an array of more params that will require that they either all pass as true, or only one of them is true, respectively.

A params object can not have both an ors and an ands simultaneously. However, its “children” (the params in an ands or ors) can have different conditionals than their parent.

For example, to make it so that the above policy also passes for methodBar and methodBaz, it can be amended as follows:

{
  // Rest of policy..

  "params": {
    "key": "callData",
    "op": "callDataToEquals",
    "value": "0xa123cd918..."
  },
  "ands": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodFoo"
      }
      "ors": [
        {
          "params": {
            "key": "callData",
            "op": "callDataMethodEquals",
            "value": "methodBar"
          }
        },
        {
          "params": {
            "key": "callData",
            "op": "callDataMethodEquals",
            "value": "methodBaz"
          }
        },
      ]
    }
  ]
}

This essentially is a schema translation of

The UserOp should target smart contract 0xa123.. and either use the methods methodFoo or methodBar or methodBaz.

Note that at the top it used ands and then used ors for the children. This is fully legal within the schema.

However, the following is incorrect :

{
  // Rest of policy..

  "params": {
    "key": "callData",
    "op": "callDataToEquals",
    "value": "0xa123cd918..."
  },
  "ands": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodFoo"
      }
    }
  ],
  "ors": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodBar"
      }
    },
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodBaz"
      }
    },
  ]
}

In this case, the ors will be completely ignored. If both ors and ands are present, then the ands will take precedence.

​

ABI Parsing

For the policy to actually know how to read the callData it needs to know the smart contract’s ABI.

For this we introduce 2 new fields. policyStaticProps and metadata. Both are essentially free range key-value dictionaries used to store information within the policy to be accessed later. The key thing to note is that values within policyStaticProps can be accessed from within metadata. This becomes invaluable with policies that have multiple conditionals like the one above.

  "policyStaticProps": {
    "contract1": {
      "abi": [...Contract ABI goes here]
    }
  }
  "params": {
    "key": "callData",
    "op": "callDataMethodEquals",
    "value": "methodBaz"
  },
  {
    "metadata": {
      "contractAbi": "<contract1.abi>"
    }
  }

Essentially here, contractAbi is a variable that callDataMethodEquals requires. To supplement its value, we use <contract1.abi>. What <contract1.abi> means is essentially policyStaticProps.contract1.abi. The <> indicate that this value is coming from policyStaticProps.

Note that the values within policyStaticProps can be named anything. The only constraint is that contractAbi is named the same within the metadata as that is what callDataMethodEquals will look for.

Extrapolating this to our running example above, the complete policy becomes:

{
  "policyType": "useroperation_payload_control", /* currently the only one supported */
  "policyStaticProps": {
    "contract1": {
      "abi": [...Contract ABI goes here]
    }
  }

  "params": {
    "key": "callData",
    "op": "callDataToEquals",
    "value": "0xa123cd918..."
  },
  "ands": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodFoo"
      },
      "metadata": {
        "contractAbi": "<contract1.abi>"
      }
    }
  ],
  "ors": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodBar"
      },
      "metadata": {
        "contractAbi": "<contract1.abi>"
      }
    },
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodBaz"
      },
      "metadata": {
        "contractAbi": "<contract1.abi>"
      }
    },
  ]
}

​

Housekeeping

The final bit to making a valid policy is adding metadata to the root of your policy, to keep basic metadata like what chains to support, the startTime and endTime.

{
  "metadata": {
    "chainIds": [
      1,        // Etheruem
      137,      // Polygon
      11155111  // Sepolia (Testnet)
    ],
    "startTime": "2024-10-23T15:50:00.000Z",
    "endTime": null
  }
}

Adding this to the above gives us a complete and working policy.

​

Complete Example Policy

The following is the culmination of all the above steps to create a complete policy.

In English, what this policy is saying is

The policy starts on the 23^rd of October 2024, does not expire and will support Ethereum, Polygon and Testnet. For a UserOp to pass this policy, it needs to be targeting smart contract 0xa123cd918... and it has to be using One of the following methods from the contract: methodFoo or methodBar or methodBaz.

{
  "policyType": "useroperation_payload_control", /* currently the only one supported */
  "policyStaticProps": {
    "contract1": {
      "abi": [...Contract ABI goes here]
    }
  },
  {
    "metadata": {
      "chainIds": [
        1,        // Etheruem
        137,      // Polygon
        11155111  // Sepolia (Testnet)
      ],
      "startTime": "2024-10-23T15:50:00.000Z",
      "endTime": null
    }
  },
  "params": {
    "key": "callData",
    "op": "callDataToEquals",
    "value": "0xa123cd918..."
  },
  "ands": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodFoo"
      },
      "metadata": {
        "contractAbi": "<contract1.abi>"
      }
    }
  ],
  "ors": [
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodBar"
      },
      "metadata": {
        "contractAbi": "<contract1.abi>"
      }
    },
    {
      "params": {
        "key": "callData",
        "op": "callDataMethodEquals",
        "value": "methodBaz"
      },
      "metadata": {
        "contractAbi": "<contract1.abi>"
      }
    },
  ]
}

​

JSON Schema: Definitions

​

policyType

The type of policy, currently only useroperation_payload_control is available.

​

policyStaticProps

Key value pair used as data storage for the policy

​

params

Where the core logic of a policy lives

​

key

The key within the UserOp to target, currently only EntryPoint v.07 is supported, so the available fields are:

1. sender
2. nonce
3. callData
4. callGasLimit
5. verificationGasLimit
6. maxFeePerGas
7. maxPriorityFeePerGas

​

op

The operation to apply within the params. Currently available:

1. equals: Exact 1:1 match with value
2. lessThanOrEquals: Is the numeric value less than or equals value
3. callDataMethodEquals: Within callData, is the method equal to a value
   • requires contractAbi defined in metadata
4. callDataToEquals: Within callData, is the to equal to a value

​

value

The value to be compared to. Can be a string, number or boolean.

​

ands

Array consisting of policies (with policyType and policyStaticProps omitted)

​

ors

Array consisting of policies (with policyType and policyStaticProps omitted)

​

metadata

Key value pair used as data storage for a single params

Special fields within metadata. At the root of a policy, there needs to be a metadata object defined. It has to contain the following:

​

startTime

ISO datetime stamp of when to start policy

​

endTime

ISO datetime stamp of when to end policy

​

chains

Array of chain IDs to support. number[]