Prepared statements and dynamics role assignment utilizing the native database role and grants mechanism.

[grodger]

Hi @lovasoa , all,

I am really enjoying using SQLPage and was wondering about other mechanisms to control or manage user permissions. The approaches outlined in Section 8 - Authentication work great for authentication but do not leverage the underlying native database engine's role and permissions system.

I am using PostgreSQL and have implemented user authentication. I have extended it to map usernames to one or more predefined roles, which I want to apply dynamically using the SET ROLE function in PostgreSQL on each page.

After extensive experimentation, I found that, as mentioned in the SQLPage documentation, prepared statements are heavily utilized. This binds the role to the prepared statements, and any change in role triggers a database error during the preparation of the prepared statements. This occurs even if a particular statement is:
(a) not invoked by the user, or
(b) invoked, but the permission could be determined at the time of execution rather than during the preparation of the statement.

Is there any way to utilize the native mechanisms of a database (PostgreSQL in this case) to manage roles and access control for specific tables?

Regards,
Grant

[lovasoa]

Hi Grant, and welcome to SQLPage!

Thank you for sharing your experience. Your approach is understandable, but it's not something I would recommend for SQLPage.

I made a more in depth answer that may also serve others with a similar problem.

Why It’s Not a Good Idea

Prepared Statement Limitations

SQLPage, by design, uses prepared statements for performance and security. Prepared statements are parsed and planned once, and their execution is bound to the context in which they were prepared. PostgreSQL enforces role permissions at the preparation stage, not at execution. This means that switching roles dynamically during a session causes permission mismatches because the prepared statements are tied to the initial role.

Connection Pooling Conflicts

SQLPage (and most web frameworks) uses connection pooling for efficiency. When a connection is returned to the pool, it retains the context of the previous user, including any SET ROLE state. The next request might reuse this connection, resulting in a mismatched role context or leaked privileges, leading to potential security vulnerabilities.

Statefulness in Stateless Environments

SQLPage the applications are fundamentally stateless. Relying on SET ROLE introduces session-level statefulness, which contradicts this stateless nature. SQLPage’s architecture expects each query execution to be independent, making session-based role switching brittle and error-prone.

Complexity and Maintainability

Managing permissions at the database level with PostgreSQL roles requires tightly coupling your application logic with database roles. This reduces flexibility when evolving application features and increases maintenance overhead, especially if permissions need to be dynamically adjusted per user or group.

Scalability Concerns

Database roles are not designed to scale with modern web applications where thousands or millions of users might have granular permissions. PostgreSQL’s role system is better suited for database administrators and internal roles rather than application-level user management.

Recommended Approach

Instead of relying on PostgreSQL roles, it’s better to implement application-layer authorization, which is what SQLPage is designed for.

Map Users to Permissions in Application Logic

Maintain a table (e.g., user_permissions) that defines access rules for specific resources. Use SQL queries to enforce these rules dynamically based on the logged-in user.

Row-Level Security (RLS) with Context Variables

If you really want database-enforced rules, consider using PostgreSQL’s Row-Level Security (RLS) features combined with session variables (e.g., SET LOCAL). RLS policies can use application-provided parameters to filter rows without requiring explicit role switching. Note that you should be aware of the connection-reuse issues mentioned above if you go that way.

While PostgreSQL roles and permissions are powerful tools, they are not designed for application-level user management, especially in stateless environments like SQLPage.

Best,
Ophir

[grodger]

Hi @lovasoa ,

Thank-you for you prompt and detailed reply! It is very much appreciated.
You have confirmed the conclusion I was slowly arriving at; to implement application-level user management (I will forgo the RLS as that does not fit my use case). All your points of why the native db approach is not a good idea are noted, and valid.

Please do keep up the great work on SQL Page, it really has been absolutely wonderful to use!

Regards,
Grant