{"id":92114,"date":"2020-08-23T19:41:56","date_gmt":"2020-08-23T17:41:56","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/realizacziya-rolevoj-modeli-dostupa-s-ispolzovaniem-row-level-security-v-postgresql"},"modified":"2020-08-23T19:41:56","modified_gmt":"2020-08-23T17:41:56","slug":"realizacziya-rolevoj-modeli-dostupa-s-ispolzovaniem-row-level-security-v-postgresql","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/administrirovanie\/realizacziya-rolevoj-modeli-dostupa-s-ispolzovaniem-row-level-security-v-postgresql","title":{"rendered":"Implementation of a role-based access model using Row Level Security in PostgreSQL","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Development of the topic A Study on Implementing Row Level Security in PostgreSQL<\/a><\/noindex> and for a detailed response<\/b> to comment.<\/a><\/noindex><\/p>\n

The strategy used implies the concept of 'Business Logic in the Database', which was described in more detail here \u2014 A Study on Implementing Business Logic at the Level of Stored Functions in PostgreSQL<\/a><\/noindex><\/p>\n

The theoretical part is well described in the documentation Postgres Pro<\/a><\/noindex> \u2014 Row Protection Policies<\/a><\/noindex>. Below is a practical implementation of a specific business task \u2014 a role-based data access model.<\/b><\/p>\n

\"Implementation<\/p>\n

The article contains nothing new, no hidden meanings or secret knowledge. It is simply a sketch about the practical implementation of a theoretical idea. If anyone is interested \u2014 read on. If not, don\u2019t waste your time.<\/p><\/blockquote>\n

<\/a><\/noindex><\/p>\n

Task Definition<\/h2>\n

\nIt is necessary to restrict access to view\/insertion\/modification\/deletion of a document according to the user's application role. The role refers to an entry in the table roles<\/b> related by a many-to-many relationship to the table users<\/b>. The details of the table implementation have been omitted due to their triviality. Specific implementation details related to the subject area have also been omitted.<\/p>\n

Implementation<\/h2>\n

<\/p>\n

Creating roles, schemas, and the table<\/h4>\n

<\/p>\n

Creating database objects<\/b><\/p>\n

CREATE ROLE store;\nCREATE SCHEMA store AUTHORIZATION store;\nCREATE TABLE store.docs\n(\n  id integer ,         -- document id\n  man_id integer , -- document manager id\n  stat_id integer ,  -- document status id\n  ...\n  is_del BOOLEAN DEFAULT FALSE \n);\nALTER TABLE store.docs ADD CONSTRAINT doc_pk PRIMARY KEY (id);\nALTER TABLE store.docs OWNER TO store ;\n<\/code><\/pre>\n
<\/p>\n
Creating functions for implementing RLS<\/h4>\n
\nChecking the ability to execute SELECT on the row<\/p>\n
                        check_select<\/b><\/p>\n
CREATE OR REPLACE FUNCTION store.check_select ( current_id store.docs.id%TYPE ) RETURNS boolean AS $$\nDECLARE\n  result boolean ;\n  curr_pid integer ;\n  curr_stat_id integer ;\n  doc_man_id integer ;\nBEGIN \n  -- DBA has access to all documents\n  IF SESSION_USER = 'curr_dba'\n  THEN\n    RETURN TRUE ;\n  END IF ;\n  --------------------------------\n\n  --If the document is marked as 'deleted' - do not show in the selection\n  SELECT\n    is_del\n  INTO\n    result\n  FROM\n    store.docs\n  WHERE\n    id = current_id ;\n IF result = TRUE\n THEN\n   RETURN FALSE ;\n END IF ;\n --------------------------------\n\n --Get the current user id\n SELECT\n   service_function.get_curr_pid ()\n INTO\n   curr_pid ;\n --------------------------------\n\n --Get the document manager id\n SELECT\n   man_id\n INTO\n   doc_man_id\n FROM\n   store.docs\n WHERE\n   id = current_id ;\n --------------------------------\n\n --If the document manager is not the current user or no manager is assigned\n --add the document to the selection\n IF doc_man_id != curr_pid OR doc_man_id IS NULL\n THEN\n   RETURN TRUE  ;\n ELSE\n   --Get the current status of the document\n   SELECT\n     stat_id                                         \n   INTO\n     curr_statid\n   FROM\n     store.docs\n   WHERE\n     id = current_id ;\n    \n   --If the status allows viewing the document - add the document to the selection                     \n   IF curr_statid = 4 OR curr_statid = 9\n   THEN\n     RETURN TRUE ;\n   ELSE\n   --Otherwise - exclude the document from the selection\n     RETURN FALSE ;\n    END IF ;\n  END IF ;\n  --------------------------------\n\n RETURN FALSE ;\nEND\n$$ LANGUAGE plpgsql SECURITY DEFINER;\nALTER FUNCTION store.check_select( store.docs.id%TYPE  ) OWNER TO store ;\nREVOKE EXECUTE ON FUNCTION store.check_select( store.docs.id%TYPE  ) FROM public; \nGRANT EXECUTE ON FUNCTION store.check_select( store.docs.id%TYPE  ) TO service_functions; \n<\/code><\/pre>\n
\nCheck the possibility to perform INSERT on the row<\/p>\n
                        check_insert<\/b><\/p>\n
CREATE OR REPLACE FUNCTION store.check_insert ( current_id store.docs.id%TYPE ) RETURNS boolean AS $$\nDECLARE\n  curr_role_id integer ;\nBEGIN\n  --DBA can add a row in any case\n  IF SESSION_USER = 'curr_dba'\n  THEN\n    RETURN TRUE ;\n  END IF ;\n  --------------------------------\n\n --Get the current user's role id \n SELECT\n   service_functions.current_rid()\n  INTO\n    curr_role_id ;\n --------------------------------\n\n--If the role allows the creation of a new document\n--permit\nIF curr_role_id = 3 OR curr_role_id = 5     \nTHEN\n  RETURN TRUE ;\nEND IF ;\n--------------------------------\nRETURN FALSE  ;\nEND\n$$ LANGUAGE plpgsql SECURITY DEFINER;\nALTER FUNCTION store.check_insert( store.docs.id%TYPE  ) OWNER TO store ;\nREVOKE EXECUTE ON FUNCTION store.check_insert( store.docs.id%TYPE  ) FROM public;\nGRANT EXECUTE ON FUNCTION store.check_insert( store.docs.id%TYPE  ) TO service_functions; \n<\/code><\/pre>\n
\nCheck the possibility to perform DELETE on the row<\/p>\n
                        check_delete<\/b><\/p>\n
CREATE OR REPLACE FUNCTION store.check_delete ( current_id store.docs.id%TYPE )\nRETURNS boolean AS $$\nBEGIN  \n  --Only DBA can delete a row \n  IF SESSION_USER = 'curr_dba'\n  THEN\n    RETURN TRUE ;\n  END IF ;\n  --------------------------------\n\n  RETURN FALSE ;\nEND\n$$ LANGUAGE plpgsql\nSECURITY DEFINER;\nALTER FUNCTION store.check_delete( store.docs.id%TYPE  ) OWNER TO store ;\nREVOKE EXECUTE ON FUNCTION store.check_delete( store.docs.id%TYPE  ) FROM public;<\/code><\/pre>\n
\nCheck the possibility to perform UPDATE on the row.<\/p>\n
                        update_using<\/b><\/p>\n
CREATE OR REPLACE FUNCTION store.update_using ( current_id store.docs.id%TYPE , is_del boolean  )\nRETURNS boolean AS $$\nBEGIN  \n   --Documents with 'deleted' status cannot be edited\n   IF is_del \n   THEN\n     RETURN FALSE ;\n ELSE\n    RETURN TRUE ;\n  END IF ;\n\nEND\n$$ LANGUAGE plpgsql SECURITY DEFINER;\nALTER FUNCTION store.update_using(  store.docs.id%TYPE ,  boolean  ) OWNER TO store ;\nREVOKE EXECUTE ON FUNCTION store.update_using(  store.docs.id%TYPE ,  boolean  ) FROM public;\nGRANT EXECUTE ON FUNCTION store.update_using( store.docs.id%TYPE  ) TO service_functions;<\/code><\/pre>\n
<\/p>\n
                        update_check<\/b><\/p>\n
CREATE OR REPLACE FUNCTION store.update_with_check ( current_id store.docs.id%TYPE , is_del boolean )\nRETURNS boolean AS $$\nDECLARE\n  current_rid integer ;\n  current_statid integer ;\nBEGIN                \n\n  --DBA can view the row \n  IF SESSION_USER = 'curr_dba'\n  THEN\n    RETURN TRUE ;\n  END IF ;\n  --------------------------------\n\n --Get the current user's role id \n SELECT\n   service_functions.current_rid()\n  INTO\n    curr_role_id ;\n --------------------------------                            \n\n --Document deletion - changing the flag \n IF is_deleted\n THEN\n   --If the user's role is ***\n   IF current_role_id = 3        \n   THEN\n      SELECT\n        stat_id                                          \n      INTO\n        curr_statid\n      FROM\n        store.docs\n      WHERE\n        id = current_id ;\n\n      --A document in status *** cannot be deleted \n      IF current_status_id = 11\n      THEN\n         RETURN FALSE ;\n      ELSE\n      --Document can be deleted in other statuses\n        RETURN TRUE ;\n      END IF ;\n\n    --Otherwise, if the user's role is ***\n    ELSIF current_role_id = 5            \n    THEN\n      --All document statuses \n      RETURN TRUE ;\n    ELSE\n      --Other users cannot delete documents\n      RETURN FALSE ;\n    END IF ;\n ELSE      \n   --Document update is allowed\n    RETURN TRUE ;\nEND IF ;\n\nRETURN FALSE ;\nEND\n$$ LANGUAGE plpgsql SECURITY DEFINER;\nALTER FUNCTION store.update_with_check( storg.docs.id%TYPE ,  boolean   ) OWNER TO store ;\nREVOKE EXECUTE ON FUNCTION store.update_with_check( storg.docs.id%TYPE ,  boolean   )  FROM public;\nGRANT EXECUTE ON FUNCTION store.update_with_check( store.docs.id%TYPE  ) TO service_functions;<\/code><\/pre>\n
\nEnabling Row Level Security policy for the table.<\/p>\n
                        ENABLE ROW LEVEL SECURITY<\/b><\/p>\n
ALTER TABLE store.docs ENABLE ROW LEVEL SECURITY ;\n\nCREATE POLICY doc_select ON store.docs FOR SELECT TO service_functions USING ( (SELECT store.check_select(id)) );\nCREATE POLICY doc_insert ON store.docs FOR INSERT TO service_functions WITH CHECK ( (SELECT store.check_insert(id)) );\nCREATE POLICY docs_delete ON store.docs FOR DELETE TO service_functions USING ( (SELECT store.check_delete(id)) );\n\nCREATE POLICY doc_update_using ON store.docs FOR UPDATE TO service_functions USING ( (SELECT store.update_using(id , is_del )) );\nCREATE POLICY doc_update_check ON store.docs FOR UPDATE TO service_functions  WITH CHECK ( (SELECT store.update_with_check(id , is_del )) );<\/code><\/pre>\n
<\/p>\n
Summary<\/h2>\n
\nIt works.<\/p>\n
The proposed strategy allowed the implementation of the role model to be transferred from the business function level to the data storage level. <\/p>\n
Functions can be used as a template for implementing more sophisticated data masking models if business requirements necessitate.
\n
Source: habr.com<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"
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