graphql-engine/server/src-lib/Hasura/RQL/DDL/Permission.hs

module Hasura.RQL.DDL.Permission
    ( CreatePerm
    , runCreatePerm
    , PermDef(..)

    , InsPerm(..)
    , InsPermDef
    , buildInsPermInfo

    , SelPerm(..)
    , SelPermDef
    , buildSelPermInfo

    , UpdPerm(..)
    , UpdPermDef
    , buildUpdPermInfo

    , DelPerm(..)
    , DelPermDef
    , buildDelPermInfo

    , IsPerm(..)

    , DropPerm
    , runDropPerm
    , dropPermissionInMetadata

    , SetPermComment(..)
    , runSetPermComment
    ) where

import           Hasura.Prelude

import qualified Data.HashMap.Strict                as HM
import qualified Data.HashMap.Strict.InsOrd         as OMap
import qualified Data.HashSet                       as HS

import           Control.Lens                       ((.~), (^?))
import           Data.Aeson
import           Data.Kind                          (Type)
import           Data.Text.Extended

import qualified Hasura.SQL.AnyBackend              as AB

import           Hasura.Base.Error
import           Hasura.EncJSON
import           Hasura.RQL.DDL.Permission.Internal
import           Hasura.RQL.DML.Internal            hiding (askPermInfo)
import           Hasura.RQL.Types
import           Hasura.SQL.Types
import           Hasura.Session

{- Note [Backend only permissions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As of writing this note, Hasura permission system is meant to be used by the
frontend. After introducing "Actions", the webhook handlers now can make GraphQL
mutations to the server with some backend logic. These mutations shouldn't be
exposed to frontend for any user since they'll bypass the business logic.

For example:-

We've a table named "user" and it has a "email" column. We need to validate the
email address. So we define an action "create_user" and it expects the same inputs
as "insert_user" mutation (generated by Hasura). Now, a role has permission for both
actions and insert operation on the table. If the insert permission is not marked
as "backend_only: true" then it visible to the frontend client along with "creat_user".

Backend only permissions adds an additional privilege to Hasura generated operations.
Those are accessable only if the request is made with `x-hasura-admin-secret`
(if authorization is configured), `x-hasura-use-backend-only-permissions`
(value must be set to "true"), `x-hasura-role` to identify the role and other
required session variables.

backend_only   `x-hasura-admin-secret`   `x-hasura-use-backend-only-permissions`  Result
------------    ---------------------     -------------------------------------   ------
FALSE           ANY                       ANY                                    Mutation is always visible
TRUE            FALSE                     ANY                                    Mutation is always hidden
TRUE            TRUE (OR NOT-SET)         FALSE                                  Mutation is hidden
TRUE            TRUE (OR NOT-SET)         TRUE                                   Mutation is shown
-}

procSetObj
  :: forall b m
   . (QErrM m, BackendMetadata b)
  => SourceName
  -> TableName b
  -> FieldInfoMap (FieldInfo b)
  -> Maybe (ColumnValues b Value)
  -> m (PreSetColsPartial b, [Text], [SchemaDependency])
procSetObj source tn fieldInfoMap mObj = do
  (setColTups, deps) <- withPathK "set" $
    fmap unzip $ forM (HM.toList setObj) $ \(pgCol, val) -> do
      ty <- askColumnType fieldInfoMap pgCol $
        "column " <> pgCol <<> " not found in table " <>> tn
      sqlExp <- parseCollectableType (CollectableTypeScalar ty) val
      let dep = mkColDep @b (getDepReason sqlExp) source tn pgCol
      return ((pgCol, sqlExp), dep)
  return (HM.fromList setColTups, depHeaders, deps)
  where
    setObj = fromMaybe mempty mObj
    depHeaders = getDepHeadersFromVal $ Object $ mapKeys toTxt setObj

    getDepReason = bool DRSessionVariable DROnType . isStaticValue

class IsPerm a where
  type PermInfo a = (r :: BackendType -> Type) | r -> a

  permAccessor
    :: (ToJSON (a b), BackendMetadata b)
    => PermAccessor b (PermInfo a b)

  buildPermInfo
    :: (ToJSON (a b), BackendMetadata b, QErrM m, TableCoreInfoRM b m)
    => SourceName
    -> TableName b
    -> FieldInfoMap (FieldInfo b)
    -> PermDef (a b)
    -> m (WithDeps (PermInfo a b))

  getPermAcc1
    :: (ToJSON (a b), BackendMetadata b)
    => PermDef (a b)
    -> PermAccessor b (PermInfo a b)
  getPermAcc1 _ = permAccessor

  getPermAcc2
    :: (ToJSON (a b), BackendMetadata b)
    => DropPerm a b
    -> PermAccessor b (PermInfo a b)
  getPermAcc2 _ = permAccessor

  addPermToMetadata
    :: (ToJSON (a b), BackendMetadata b)
    => PermDef (a b)
    -> TableMetadata b
    -> TableMetadata b

doesPermissionExistInMetadata
  :: TableMetadata b
  -> RoleName
  -> PermType
  -> Bool
doesPermissionExistInMetadata tableMetadata roleName = \case
  -- TODO: lot of repetition below, any way to simplify this?
  PTInsert -> isJust $ tableMetadata ^? tmInsertPermissions.ix roleName
  PTSelect -> isJust $ tableMetadata ^? tmSelectPermissions.ix roleName
  PTUpdate -> isJust $ tableMetadata ^? tmUpdatePermissions.ix roleName
  PTDelete -> isJust $ tableMetadata ^? tmDeletePermissions.ix roleName

runCreatePerm
  :: forall m b a
   . (ToJSON (a b), IsPerm a, UserInfoM m, CacheRWM m, MonadError QErr m, MetadataM m, BackendMetadata b)
  => CreatePerm a b -> m EncJSON
runCreatePerm (CreatePerm (WithTable source tableName permissionDefn)) = do
  tableMetadata <- askTableMetadata @b source tableName
  let permAcc = getPermAcc1 permissionDefn
      permissionType = permAccToType permAcc
      ptText = permTypeToCode permissionType
      role = _pdRole permissionDefn
      metadataObject = MOSourceObjId source
                         $ AB.mkAnyBackend
                         $ SMOTableObj @b tableName
                         $ MTOPerm role permissionType

    -- NOTE: we check if a permission exists for a `(table, role)` entity in the metadata
  -- and not in the `RolePermInfoMap b` because there may exist a permission for the `role`
  -- which is an inherited one, so we check it in the metadata directly

  -- The metadata will not contain the permissions for the admin role,
  -- because the graphql-engine automatically creates the role and it's
  -- assumed that the admin role is an implicit role of the graphql-engine.
  when (doesPermissionExistInMetadata tableMetadata role permissionType || role == adminRoleName) $ throw400 AlreadyExists $
    ptText <> " permission already defined on table " <> tableName <<> " with role " <>> role
  buildSchemaCacheFor metadataObject
    $ MetadataModifier
    $ tableMetadataSetter @b source tableName %~ addPermToMetadata permissionDefn
  pure successMsg

runDropPerm
  :: forall b a m
   . (ToJSON (a b), IsPerm a, UserInfoM m, CacheRWM m, MonadError QErr m, MetadataM m, BackendMetadata b)
  => DropPerm a b
  -> m EncJSON
runDropPerm dp@(DropPerm source table role) = do
  tableMetadata <- askTableMetadata @b source table
  let permType = permAccToType $ getPermAcc2 dp
  unless (doesPermissionExistInMetadata tableMetadata role permType) $ do
    let errMsg = mconcat
                 [ permTypeToCode permType <> " permission on " <>> table
                 , " for role " <>> role
                 , " does not exist"
                 ]
    throw400 PermissionDenied errMsg
  withNewInconsistentObjsCheck
    $ buildSchemaCache
    $ MetadataModifier
    $ tableMetadataSetter @b source table %~ dropPermissionInMetadata role permType
  return successMsg

dropPermissionInMetadata
  :: RoleName -> PermType -> TableMetadata b -> TableMetadata b
dropPermissionInMetadata rn = \case
  PTInsert -> tmInsertPermissions %~ OMap.delete rn
  PTSelect -> tmSelectPermissions %~ OMap.delete rn
  PTDelete -> tmDeletePermissions %~ OMap.delete rn
  PTUpdate -> tmUpdatePermissions %~ OMap.delete rn


buildInsPermInfo
  :: forall b m
   . (QErrM m, TableCoreInfoRM b m, BackendMetadata b)
  => SourceName
  -> TableName b
  -> FieldInfoMap (FieldInfo b)
  -> PermDef (InsPerm b)
  -> m (WithDeps (InsPermInfo b))
buildInsPermInfo source tn fieldInfoMap (PermDef _rn (InsPerm checkCond set mCols mBackendOnly) _) =
  withPathK "permission" $ do
    (be, beDeps) <- withPathK "check" $ procBoolExp source tn fieldInfoMap checkCond
    (setColsSQL, setHdrs, setColDeps) <- procSetObj source tn fieldInfoMap set
    void $ withPathK "columns" $ indexedForM insCols $ \col ->
           askColumnType fieldInfoMap col ""
    let fltrHeaders = getDependentHeaders checkCond
        reqHdrs = fltrHeaders `union` setHdrs
        insColDeps = map (mkColDep @b DRUntyped source tn) insCols
        deps = mkParentDep @b source tn : beDeps ++ setColDeps ++ insColDeps
        insColsWithoutPresets = insCols \\ HM.keys setColsSQL
    return (InsPermInfo (HS.fromList insColsWithoutPresets) be setColsSQL backendOnly reqHdrs, deps)
  where
    backendOnly = Just True == mBackendOnly
    allCols = map pgiColumn $ getCols fieldInfoMap
    insCols = maybe allCols (convColSpec fieldInfoMap) mCols

instance IsPerm InsPerm where
  type PermInfo InsPerm = InsPermInfo
  permAccessor = PAInsert
  buildPermInfo = buildInsPermInfo

  addPermToMetadata permDef =
    tmInsertPermissions %~ OMap.insert (_pdRole permDef) permDef


buildSelPermInfo
  :: forall b m
   . (QErrM m, TableCoreInfoRM b m, BackendMetadata b)
  => SourceName
  -> TableName b
  -> FieldInfoMap (FieldInfo b)
  -> SelPerm b
  -> m (WithDeps (SelPermInfo b))
buildSelPermInfo source tn fieldInfoMap sp = withPathK "permission" $ do
  let pgCols     = convColSpec fieldInfoMap $ spColumns sp

  (boolExp, boolExpDeps) <- withPathK "filter" $
    procBoolExp source tn fieldInfoMap  $ spFilter sp

  -- check if the columns exist
  void $ withPathK "columns" $ indexedForM pgCols $ \pgCol ->
    askColumnType fieldInfoMap pgCol autoInferredErr

  -- validate computed fields
  scalarComputedFields <-
    withPathK "computed_fields" $ indexedForM computedFields $ \fieldName -> do
      computedFieldInfo <- askComputedFieldInfo fieldInfoMap fieldName
      case _cfiReturnType computedFieldInfo of
        CFRScalar _               -> pure fieldName
        CFRSetofTable returnTable -> throw400 NotSupported $
          "select permissions on computed field " <> fieldName
          <<> " are auto-derived from the permissions on its returning table "
          <> returnTable <<> " and cannot be specified manually"

  let deps = mkParentDep @b source tn : boolExpDeps ++ map (mkColDep @b DRUntyped source tn) pgCols
             ++ map (mkComputedFieldDep @b DRUntyped source tn) scalarComputedFields
      depHeaders = getDependentHeaders $ spFilter sp
      mLimit = spLimit sp

  withPathK "limit" $ mapM_ onlyPositiveInt mLimit

  let pgColsWithFilter = HM.fromList $ map (, Nothing) pgCols
      scalarComputedFieldsWithFilter = HS.toMap (HS.fromList scalarComputedFields) $> Nothing

  let selPermInfo =
        SelPermInfo pgColsWithFilter scalarComputedFieldsWithFilter boolExp mLimit allowAgg depHeaders

  return ( selPermInfo, deps )
  where
    allowAgg = spAllowAggregations sp
    computedFields = spComputedFields sp
    autoInferredErr = "permissions for relationships are automatically inferred"

instance IsPerm SelPerm where
  type PermInfo SelPerm = SelPermInfo
  permAccessor = PASelect
  buildPermInfo source tn fieldInfoMap (PermDef _ a _) =
    buildSelPermInfo source tn fieldInfoMap a

  addPermToMetadata permDef =
    tmSelectPermissions %~ OMap.insert (_pdRole permDef) permDef


buildUpdPermInfo
  :: forall b m
   . (QErrM m, TableCoreInfoRM b m, BackendMetadata b)
  => SourceName
  -> TableName b
  -> FieldInfoMap (FieldInfo b)
  -> UpdPerm b
  -> m (WithDeps (UpdPermInfo b))
buildUpdPermInfo source tn fieldInfoMap (UpdPerm colSpec set fltr check) = do
  (be, beDeps) <- withPathK "filter" $
    procBoolExp source tn fieldInfoMap fltr

  checkExpr <- traverse (withPathK "check" . procBoolExp source tn fieldInfoMap) check

  (setColsSQL, setHeaders, setColDeps) <- procSetObj source tn fieldInfoMap set

  -- check if the columns exist
  void $ withPathK "columns" $ indexedForM updCols $ \updCol ->
       askColumnType fieldInfoMap updCol relInUpdErr

  let updColDeps = map (mkColDep @b DRUntyped source tn) updCols
      deps = mkParentDep @b source tn : beDeps ++ maybe [] snd checkExpr ++ updColDeps ++ setColDeps
      depHeaders = getDependentHeaders fltr
      reqHeaders = depHeaders `union` setHeaders
      updColsWithoutPreSets = updCols \\ HM.keys setColsSQL

  return (UpdPermInfo (HS.fromList updColsWithoutPreSets) tn be (fst <$> checkExpr) setColsSQL reqHeaders, deps)

  where
    updCols     = convColSpec fieldInfoMap colSpec
    relInUpdErr = "relationships can't be used in update"

instance IsPerm UpdPerm where
  type PermInfo UpdPerm = UpdPermInfo
  permAccessor = PAUpdate
  buildPermInfo source tn fieldInfoMap (PermDef _ a _) =
    buildUpdPermInfo source tn fieldInfoMap a

  addPermToMetadata permDef =
    tmUpdatePermissions %~ OMap.insert (_pdRole permDef) permDef


buildDelPermInfo
  :: forall b m
   . (QErrM m, TableCoreInfoRM b m, BackendMetadata b)
  => SourceName
  -> TableName b
  -> FieldInfoMap (FieldInfo b)
  -> DelPerm b
  -> m (WithDeps (DelPermInfo b))
buildDelPermInfo source tn fieldInfoMap (DelPerm fltr) = do
  (be, beDeps) <- withPathK "filter" $
    procBoolExp source tn fieldInfoMap  fltr
  let deps = mkParentDep @b source tn : beDeps
      depHeaders = getDependentHeaders fltr
  return (DelPermInfo tn be depHeaders, deps)

instance IsPerm DelPerm where
  type PermInfo DelPerm = DelPermInfo
  permAccessor = PADelete
  buildPermInfo source tn fieldInfoMap (PermDef _ a _) =
    buildDelPermInfo source tn fieldInfoMap a

  addPermToMetadata permDef =
    tmDeletePermissions %~ OMap.insert (_pdRole permDef) permDef


data SetPermComment b
  = SetPermComment
  { apSource     :: !SourceName
  , apTable      :: !(TableName b)
  , apRole       :: !RoleName
  , apPermission :: !PermType
  , apComment    :: !(Maybe Text)
  }

instance (Backend b) => FromJSON (SetPermComment b) where
  parseJSON = withObject "set permission comment" $ \o ->
    SetPermComment
      <$> o .:? "source" .!= defaultSource
      <*> o .: "table"
      <*> o .: "role"
      <*> o .: "permission"
      <*> o .:? "comment"

runSetPermComment
  :: forall b m
   . (QErrM m, CacheRWM m, MetadataM m, BackendMetadata b)
  => SetPermComment b
  -> m EncJSON
runSetPermComment (SetPermComment source table roleName permType comment) =  do
  tableInfo <- askTabInfo @b source table

  -- assert permission exists and return appropriate permission modifier
  permModifier <- case permType of
    PTInsert -> do
      assertPermDefined roleName PAInsert tableInfo
      pure $ tmInsertPermissions.ix roleName.pdComment .~ comment
    PTSelect -> do
      assertPermDefined roleName PASelect tableInfo
      pure $ tmSelectPermissions.ix roleName.pdComment .~ comment
    PTUpdate -> do
      assertPermDefined roleName PAUpdate tableInfo
      pure $ tmUpdatePermissions.ix roleName.pdComment .~ comment
    PTDelete -> do
      assertPermDefined roleName PADelete tableInfo
      pure $ tmDeletePermissions.ix roleName.pdComment .~ comment

  let metadataObject = MOSourceObjId source
                         $ AB.mkAnyBackend
                         $ SMOTableObj @b table
                         $ MTOPerm roleName permType
  buildSchemaCacheFor metadataObject
    $ MetadataModifier
    $ tableMetadataSetter @b source table %~ permModifier
  pure successMsg