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alexandratran merged 2 commits into from
Aug 17, 2023
Merged

Improve snaps permissions doc #886

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Improve snaps permissions doc
alexandratran Aug 16, 2023
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address reviewer feedback
alexandratran Aug 17, 2023
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39 changes: 30 additions & 9 deletions snaps/reference/permissions.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,23 @@ sidebar_position: 4
You can [request the following permissions](../how-to/request-permissions.md) in your snap manifest
file.

## endowment:cronjob
## RPC API permissions

You must request permission to use any
[restricted JSON-RPC API methods](rpc-api.md#restricted-methods).

For example, to request to use [`snap_dialog`](rpc-api.md#snap_dialog), add the following to the
manifest file:

```json
"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
Expand Down Expand Up @@ -51,7 +67,7 @@ Specify this permission in the manifest file as follows:
}
```

## endowment:ethereum-provider
### 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.
Expand All @@ -65,7 +81,7 @@ Specify this permission in the manifest file as follows:
},
```

## endowment:long-running
### endowment:long-running

A snap that is computationally heavy and can't finish execution within the
[snap lifecycle requirements](../concepts/lifecycle.md) must request the `endowment:long-running` permission.
Expand All @@ -79,7 +95,7 @@ Specify this permission in the manifest file as follows:
},
```

## endowment:network-access
### 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.
Expand All @@ -98,11 +114,16 @@ Specify this permission in the manifest file as follows:
},
```

### Same-origin policy and CORS
#### Same-origin policy and CORS

`fetch()` requests in a snap are bound by browsers' [same-origin policy](https://developer.mozilla.org/en-US/docs/Web/Security/Same-origin_policy#cross-origin_network_access). 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`](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) CORS header with the value `*` or `null` in the response.
`fetch()` requests in a snap are bound by the browser's [same-origin policy](https://developer.mozilla.org/en-US/docs/Web/Security/Same-origin_policy#cross-origin_network_access).
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`](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) CORS header
with the value `*` or `null` in the response.

## endowment:rpc
### 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
Expand All @@ -125,7 +146,7 @@ Specify this permission in the manifest file as follows:
}
```

## endowment:transaction-insight
### 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
Expand All @@ -146,7 +167,7 @@ Specify this permission in the manifest file as follows:
},
```

## endowment:webassembly
### 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.
Expand Down