graphql-engine/server/src-lib/Data/HashMap/Strict/Extended.hs
Karthikeyan Chinnakonda 92026b769f [Preview] Inherited roles for postgres read queries
fixes #3868

docker image - `hasura/graphql-engine:inherited-roles-preview-48b73a2de`

Note:

To be able to use the inherited roles feature, the graphql-engine should be started with the env variable `HASURA_GRAPHQL_EXPERIMENTAL_FEATURES` set to `inherited_roles`.

Introduction
------------

This PR implements the idea of multiple roles as presented in this [paper](https://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/FGALanguageICDE07.pdf). The multiple roles feature in this PR can be used via inherited roles. An inherited role is a role which can be created by combining multiple singular roles. For example, if there are two roles `author` and `editor` configured in the graphql-engine, then we can create a inherited role with the name of `combined_author_editor` role which will combine the select permissions of the `author` and `editor` roles and then make GraphQL queries using the `combined_author_editor`.

How are select permissions of different roles are combined?
------------------------------------------------------------

A select permission includes 5 things:

1. Columns accessible to the role
2. Row selection filter
3. Limit
4. Allow aggregation
5. Scalar computed fields accessible to the role

 Suppose there are two roles, `role1` gives access to the `address` column with row filter `P1` and `role2` gives access to both the `address` and the `phone` column with row filter `P2` and we create a new role `combined_roles` which combines `role1` and `role2`.

Let's say the following GraphQL query is queried with the `combined_roles` role.

```graphql
query {
   employees {
     address
     phone
   }
}
```

This will translate to the following SQL query:

```sql

 select
    (case when (P1 or P2) then address else null end) as address,
    (case when P2 then phone else null end) as phone
 from employee
 where (P1 or P2)
```

The other parameters of the select permission will be combined in the following manner:

1. Limit - Minimum of the limits will be the limit of the inherited role
2. Allow aggregations - If any of the role allows aggregation, then the inherited role will allow aggregation
3. Scalar computed fields - same as table column fields, as in the above example

APIs for inherited roles:
----------------------

1. `add_inherited_role`

`add_inherited_role` is the [metadata API](https://hasura.io/docs/1.0/graphql/core/api-reference/index.html#schema-metadata-api) to create a new inherited role. It accepts two arguments

`role_name`: the name of the inherited role to be added (String)
`role_set`: list of roles that need to be combined (Array of Strings)

Example:

```json
{
  "type": "add_inherited_role",
  "args": {
      "role_name":"combined_user",
      "role_set":[
          "user",
          "user1"
      ]
  }
}
```

After adding the inherited role, the inherited role can be used like single roles like earlier

Note:

An inherited role can only be created with non-inherited/singular roles.

2. `drop_inherited_role`

The `drop_inherited_role` API accepts the name of the inherited role and drops it from the metadata. It accepts a single argument:

`role_name`: name of the inherited role to be dropped

Example:

```json

{
  "type": "drop_inherited_role",
  "args": {
      "role_name":"combined_user"
  }
}
```

Metadata
---------

The derived roles metadata will be included under the `experimental_features` key while exporting the metadata.

```json
{
  "experimental_features": {
    "derived_roles": [
      {
        "role_name": "manager_is_employee_too",
        "role_set": [
          "employee",
          "manager"
        ]
      }
    ]
  }
}
```

Scope
------

Only postgres queries and subscriptions are supported in this PR.

Important points:
-----------------

1. All columns exposed to an inherited role will be marked as `nullable`, this is done so that cell value nullification can be done.

TODOs
-------

- [ ] Tests
   - [ ] Test a GraphQL query running with a inherited role without enabling inherited roles in experimental features
   - [] Tests for aggregate queries, limit, computed fields, functions, subscriptions (?)
   - [ ] Introspection test with a inherited role (nullability changes in a inherited role)
- [ ] Docs
- [ ] Changelog

Co-authored-by: Vamshi Surabhi <6562944+0x777@users.noreply.github.com>
GitOrigin-RevId: 3b8ee1e11f5ceca80fe294f8c074d42fbccfec63
2021-03-08 11:15:10 +00:00

81 lines
3.3 KiB
Haskell

module Data.HashMap.Strict.Extended
( module M
, catMaybes
, fromListOn
, unionsAll
, groupOn
, groupOnNE
, differenceOn
, lpadZip
, mapKeys
, unionsWith
) where
import Prelude
import qualified Data.Align as A
import qualified Data.Foldable as F
import Data.Function
import Data.HashMap.Strict as M
import Data.Hashable
import Data.List.NonEmpty (NonEmpty (..))
import Data.These
catMaybes :: HashMap k (Maybe v) -> HashMap k v
catMaybes = M.mapMaybe id
fromListOn :: (Eq k, Hashable k) => (v -> k) -> [v] -> HashMap k v
fromListOn f = fromList . Prelude.map (\v -> (f v, v))
-- | Like 'M.unions', but keeping all elements in the result.
unionsAll :: (Eq k, Hashable k, Foldable t) => t (HashMap k v) -> HashMap k (NonEmpty v)
unionsAll = F.foldl' (\a b -> unionWith (<>) a (fmap (:|[]) b)) M.empty
-- | Given a 'Foldable' sequence of values and a function that extracts a key from each value,
-- returns a 'HashMap' that maps each key to a list of all values in the sequence for which the
-- given function produced it.
--
-- >>> groupOn (take 1) ["foo", "bar", "baz"]
-- fromList [("f", ["foo"]), ("b", ["bar", "baz"])]
groupOn :: (Eq k, Hashable k, Foldable t) => (v -> k) -> t v -> HashMap k [v]
groupOn f = fmap F.toList . groupOnNE f
groupOnNE :: (Eq k, Hashable k, Foldable t) => (v -> k) -> t v -> HashMap k (NonEmpty v)
groupOnNE f = Prelude.foldr (\v -> M.alter (Just . (v:|) . maybe [] F.toList) (f v)) M.empty
differenceOn :: (Eq k, Hashable k, Foldable t) => (v -> k) -> t v -> t v -> HashMap k v
differenceOn f = M.difference `on` (fromListOn f . F.toList)
-- | Analogous to 'A.lpadZip', but on 'HashMap's instead of lists.
lpadZip :: (Eq k, Hashable k) => HashMap k a -> HashMap k b -> HashMap k (Maybe a, b)
lpadZip left = catMaybes . flip A.alignWith left \case
This _ -> Nothing
That b -> Just (Nothing, b)
These a b -> Just (Just a, b)
-- | @'mapKeys' f s@ is the map obtained by applying @f@ to each key of @s@.
--
-- The size of the result may be smaller if @f@ maps two or more distinct
-- keys to the same new key. In this case the value at the greatest of the
-- original keys is retained.
--
-- > mapKeys (+ 1) (fromList [(5,"a"), (3,"b")]) == fromList [(4, "b"), (6, "a")]
-- > mapKeys (\ _ -> 1) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 1 "c"
-- > mapKeys (\ _ -> 3) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 3 "c"
--
-- copied from https://hackage.haskell.org/package/containers-0.6.4.1/docs/src/Data.Map.Internal.html#mapKeys
mapKeys :: (Ord k2, Hashable k2) => (k1 -> k2) -> HashMap k1 a -> HashMap k2 a
mapKeys f = fromList . foldrWithKey (\k x xs -> (f k, x) : xs) []
-- | The union of a list of maps, with a combining operation:
-- (@'unionsWith' f == 'Prelude.foldl' ('unionWith' f) 'empty'@).
--
-- > unionsWith (++) [(fromList [(5, "a"), (3, "b")]), (fromList [(5, "A"), (7, "C")]), (fromList [(5, "A3"), (3, "B3")])]
-- > == fromList [(3, "bB3"), (5, "aAA3"), (7, "C")]
--
-- copied from https://hackage.haskell.org/package/containers-0.6.4.1/docs/src/Data.Map.Internal.html#unionsWith
unionsWith :: (Foldable f, Hashable k, Ord k) => (a -> a -> a) -> f (HashMap k a) -> HashMap k a
unionsWith f ts
= F.foldl' (unionWith f) empty ts