[adontz]

What people often don't realize is that in a big business system a user may have no permission to raw data of some table, but may have permission to report which includes aggregated data of the same table, so report permissions cannot be deducted from base CRUD permissions.

If such SIAAS

    - Checks that query is SELECT query (can be tricky with CTE, requires proper SQL parser)
    - Allows editing said query by superuser only
    - Can be parametrized, including implicit $current_user_id$ parameter
    - Has it's own permissions and users can run the query if they have permissions

It's safe enough. I've seen and applied such "Edit raw SQL in HTML form" many times. It's super flexible, especially combined with some CSV-to-HTML, CSV-to-PDF, or CSV-to-XLS rendering engine.

[indigo945]

> - Checks that query is SELECT query (can be tricky with CTE, requires proper SQL parser)

Not only is this difficult parsing-wise, there's also no reason to assume that a select query is read-only even when no CTE or subqueries are involved. Function calls in the select clause can also write data.

> - Has it's own permissions and users can run the query if they have permissions

This is the important one. If the role the query runs as doesn't have write permissions on any table, then the user can't write data, period.

Note that this is often not as easy to implement as it seems. For example, in PostgreSQL, neither set role nor set session authorization actually prevent the user from doing malicious things, because the user can just reset role or reset session authorization in the query. For PostgreSQL to properly respect a role's permissions, the SIAAS needs to actually connect to the database as that role.

Common GUC-based row level security approaches are also incompatible with this idea.

[kogus]

I'm not sure what database platform they used, but in SQL Server, functions cannot have side-effects.

https://learn.microsoft.com/en-us/sql/relational-databases/u...

[Tostino]

Hell, your user can have no write access at all, but the function or procedure can be using SECURITY DEFINER and the code inside it will run with the permissions of the function owner rather than the calling user allowing writes to happen.

Trusting a select to be read only is naive.

[leprechaun1066]

Most applications backed kdb+ do just this. It comes with its own parser and you can query tables using something like an ast.

For example the user might ask for data with the constraint

  where TradingDesk=`Eq, AvgPx>500.0

which kdb+ parses into

  ((=;`TradingDesk;(),`Eq);(>;`AvgPx;500.0))

As a dev on the system I can then have a function which takes in this constraint and a list of clients that I want to restrict the result to. That list of clients could come from another function related to the entitlements of the user who made the request:

  applyClientRestriction:{[constraint;clients] constraint,enlist(in;`Client;enlist clients)}

Which results in an extension of the constraint like this for two clients A and B:

  q)applyClientRestriction[((=;`TradingDesk;(),`Eq);(>;`AvgPx;500.0));`ClientA`ClientB]
  ((=;`TradingDesk;enlist`Eq);(>;`AvgPx;500.0);(in;`Client;enlist`ClientA`ClientB))

Then that gets passed to the function which executes the query on the table (kdb+ supports querying tables in a functional manner as well as with a structured query language) and the result has the restrictions applied.

It's really nice because, once parsed, it's list processing like in a lisp and not string processing which is a pain.

[ako]

So you build a view on top of the tables, allows users access to the aggregating views, but not to the underlying tables?