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Snaps permissions

Your Snap can request the following permissions.

RPC API permissions​

You must request permission to use any restricted JSON-RPC API methods.

For example, to request to use snap_dialog, add the following to the manifest file:

"initialPermissions": {
  "snap_dialog": {}
},

Endowments​

endowment:cronjob​

To run periodic actions for the user (cron jobs), a Snap must request the endowment:cronjob permission. This permission allows the Snap to specify cron jobs that trigger the exported onCronjob method.

Specify this permission in the manifest file as follows:

{
  "initialPermissions": {
    "endowment:cronjob": {
      "jobs": [
        {
          "expression": {
            "minute": "*",
            "hour": "*",
            "dayOfMonth": "*",
            "month": "*",
            "dayOfWeek": "*"
          },
          "request": {
            "method": "exampleMethodOne",
            "params": {
              "param1": "foo"
            }
          }
        },
        {
          "expression": "* * * * *",
          "request": {
            "method": "exampleMethodTwo",
            "params": {
              "param1": "bar"
            }
          }
        }
      ]
    }
  }
}

endowment:ethereum-provider​

To communicate with a node using MetaMask, a Snap must request the endowment:ethereum-provider permission. This permission exposes the global API ethereum to the Snap execution environment. This global is an EIP-1193 provider.

Specify this permission in the manifest file as follows:

"initialPermissions": {
  "endowment:ethereum-provider": {}
},
note

The global ethereum API in Snaps has fewer capabilities than window.ethereum for dapps. You can only use it to make read requests from the RPC provider, not to write to the blockchain or initiate transactions. You can also use it to connect to Ethereum accounts with eth_requestAccounts and then use personal_sign with those connected accounts.

endowment:network-access​

To access the internet, a Snap must request the endowment:network-access permission. This permission exposes the global fetch API to the Snaps execution environment.

caution

XMLHttpRequest isn't available in Snaps, and you should replace it with fetch. If your dependencies use XMLHttpRequest, you can patch it away.

Specify this permission in the manifest file as follows:

"initialPermissions": {
  "endowment:network-access": {}
},

Same-origin policy and CORS​

fetch() requests in a Snap are bound by the browser's same-origin policy. Since Snap code is executed in an iframe with the sandbox property, the browser sends an Origin header with the value null with outgoing requests. For the Snap to be able to read the response, the server must send an Access-Control-Allow-Origin CORS header with the value * or null in the response.

endowment:rpc​

To handle arbitrary JSON-RPC requests, a Snap must request the endowment:rpc permission. This permission grants a Snap access to JSON-RPC requests sent to the Snap, using the exported onRpcRequest method.

This permission requires an object with a snaps or dapps property (or both), to signal if the snap can receive JSON-RPC requests from other Snaps, or dapps, respectively. The default for both properties is false.

Specify this permission in the manifest file as follows:

{
  "initialPermissions": {
    "endowment:rpc": {
      "dapps": true,
      "snaps": false
    }
  }
}

endowment:transaction-insight​

To provide transaction insights, a Snap must request the endowment:transaction-insight permission. This permission grants a Snap read-only access to raw transaction payloads, before they're accepted for signing by the user, by exporting the onTransaction method.

This permission requires an object with an allowTransactionOrigin property to signal if the Snap should pass the transactionOrigin property as part of the onTransaction parameters. This property represents the transaction initiator origin. The default is false.

Specify this permission in the manifest file as follows:

"initialPermissions": {
  "endowment:transaction-insight": {
    "allowTransactionOrigin": true
  }
},

endowment:webassembly​

To use WebAssembly, a Snap must request the endowment:webassembly permission. This permission exposes the global WebAssembly API to the Snap execution environment.

Specify this permission in the manifest file as follows:

"initialPermissions": {
  "endowment:webassembly": {}
},

Dynamic permissions​

Dynamic permissions are not requested in the manifest file. Instead, your Snap can acquire dynamic permissions during its lifecycle.

eth_accounts​

A Snap can request permission to call the Ethereum provider's eth_accounts RPC method by calling the provider's eth_requestAccounts RPC method. Calling eth_requestAccounts requires the ethereum-provider endowment.

You can check the presence of the permission by calling wallet_getPermissions. If the permission is present, the result contains a permission with a parentCapability of eth_accounts. It comes with a caveat of restrictReturnedAccounts, an array of all the accounts the user allows for this Snap. The following is an example eth_accounts permission:

{
  "id": "47vm2UUi1pccNAeYKGmwF", // example
  "parentCapability": "eth_accounts",
  "invoker": "npm:SNAP_ID",
  "caveats": [
    {
      "type": "restrictReturnedAccounts",
      "value": [
        "0xc403b37bf1e700cb214ea1be9de066824b420de6" // example connected account #1
      ]
    }
  ],
  "date": 1692616452846
}

The user can revoke this permission by going to the Snap's settings under Snap permissions.