datasette-permissions-sql 0.1a0

Datasette plugin for configuring permission checks using SQL queries

datasette-permissions-sql

Datasette plugin for configuring permission checks using SQL queries

This only works with the next, unreleased version of Datasette

Installation

Install this plugin in the same environment as Datasette.

$ pip install datasette-permissions-sql

Usage

First, read up on how Datasette's authentication and permissions system works.

This plugin lets you define SQL queries that are executed to see if the currently authenticated actor has permission to perform certain actions.

Consider a canned query which authenticated users should only be able to execute if a row in the users table says that they are a member of staff.

That users table in the mydatabase.db database could look like this:

id	username	is_staff
1	cleopaws	0
2	simon	1

Authenticated users have an actor that looks like this:

{
    "id": 2,
    "username": "simon"
}

To configure the canned query to only be executable by staff users, add the following to your metadata.json:

{
    "plugins": {
        "datasette-permissions-sql": [
            {
                "action": "view-query",
                "resource": ["mydatabase", "promote_to_staff"],
                "sql": "SELECT * FROM users WHERE is_staff = 1 AND id = :actor_id"
            }
        ]
    },
    "databases": {
        "mydatabase": {
            "queries": {
                "promote_to_staff": {
                    "sql": "UPDATE users SET is is_staff=1 WHERE id=:id",
                    "write": true
                }
            }
        }
    }
}

The "datasette-permissions-sql" key is a list of SQL matching rules. Each of those rules has the following shape:

{
    "action": "name-of-action",
    "resource": ["resource identifier to run this on"],
    "sql": "SQL query to execute",
    "database": "mydatabas"
}

Both "action" and "resource" are optional. If present, the SQL query will only be executed on permission checks that match the action and, if present, the resource indicators.

"database" is also optional: it specifies the named database that the query should be executed against. If it is not present the first connected database will be used.

The Datasette documentation includes a list of built-in permissions that you might want to use here.

The SQL query

If the SQL query returns any rows the permission will be allowed. If it returns no rows, the plugin hook will return None which means other plugins can have a go at checking permissions.

If the SQL query returns a single value of -1 it well be treated as an explicit "deny permission" response to the permission check.

The SQL query is called with a number of named parameters. You can use any of these as part of the query.

The list of parameters is as follows:

• action - the action, e.g. "view-database"
• resource_1 - the first component of the resource, if one was passed
• resource_2 - the second component of the resource, if available
• actor_* - a parameter for every key on the actor. Usually actor_id is present.

The SQL query can return any of three different types of result:

• No rows at all means "I don't have an opinion about this permission" - which allows the default permission to apply.
• One or more rows means "allow" - unless...
• A single row with a single value of -1 - which means "deny"

Another example table, this time granting explicit access to individual tables. Consider a table called table_access that looks like this:

user_id	database	table	access_level
1	mydb	dogs	1
2	mydb	dogs	1
1	mydb	cats	1
2	mydb	cats	-1

The following SQL query would grant access to the dogs ttable in the mydb.db database to users 1 and 2 - but would forbid access for user 2 to the cats table:

SELECT
    access_level
FROM
    table_access
WHERE
    user_id = :actor_id
    AND "database" = :resource_1
    AND "table" = :resource_2

In a metadata.yaml configuration file that would look like this:

databases:
  mydb:
    allow_sql: {}
plugins:
  datasette-permissions-sql:
  - action: view-table
    sql: |-
      SELECT
        access_level
      FROM
        table_access
      WHERE
        user_id = :actor_id
        AND "database" = :resource_1
        AND "table" = :resource_2

We're using allow_sql: {} here to disable arbitrary SQL queries to prevent users from running select * from cats directly to work around the permissions limits.