Securing Sharepoint Lists With Client-Side Rendering

Why Client-Side Rendering Improves Security

Using client-side rendering (CSR) to display SharePoint list data can enhance security in several key ways:

• Limits server access to full data set. With CSR, the entire list data set does not need to be sent to the client. The server can filter the data set before sending it to the browser for rendering. This limits exposure of sensitive data.
• Reduces attack surface area. Fetching less data from the server minimizes the footprint for injection attacks. CSR enables row-level security, reducing the amount of data exposed.
• Enables row-level security. CSR allows showing or hiding specific rows in a list based on user permissions. This provides greater control over data visibility.

Limiting Access to Full Data Set

By default, SharePoint list views retrieve all list data and send it to the client for filtering and display. However, fetching the entire data set exposes more information than necessary. CSR allows SharePoint to filter the data on the server before sending it across the wire.

For example, an HR list may contain sensitive salary information that only managers should see. With CSR, SharePoint can query the user permissions and only return salary data for manager profiles. The rendered list view will only display salary data for authorized personnel.

Reducing Surface Area for Injection Attacks

Sending less data to the client also shrinks the potential attack surface area. JavaScript injection relies on inserting malicious code into the data sent to the browser. If CSR limits the data set exposed, there is less footprint for an injection attack to compromise.

For example, by filtering out unnecessary columns in a list, any injection attack would have less data to manipulate. The rendered list view is only displaying a subset of non-sensitive information to that user.

Enabling Row-Level Security on Lists

A key advantage of CSR is the ability to apply security filters at the individual row level within a list. Instead of all-or-nothing access to the full data set, permissions can be defined for specific rows.

For example, managers may have access to employee records in an HR system for their direct reports but not company-wide. With CSR, SharePoint can check group membership on each list row and only return the employee records the manager has rights to view.

Implementing Client-Side Rendering

There are several configuration steps required to enable CSR for SharePoint lists:

• Configuring list views for CSR
• Returning filtered data sets from the server
• Example: Filtering columns with React

Configuring List Views for CSR

The first implementation step is to define CSR-enabled list views. Within List Settings, create a new view and check the “Client-side rendering” option. This view will now retrieve data through the SharePoint REST API instead of the full page request.

You can also specify row limiting and sorting options in the view. Consider performance implications when configuring filtered list views.

Returning Filtered Data Sets

With a client-side rendering list view created, the next step is using REST to return a filtered data set optimized for that view. Create custom endpoints to query list data with filters and row limits applied on the server.

For example, an endpoint like /_api/list/GetByDepartment?department=sales could return the targeted rows. Access permissions can also be checked before returning data.

Example: Filtering Columns with React

Once the SharePoint API endpoints are returning filtered data sets, those can be consumed by client-side code. Using React is a common approach to render CSR list views.

The React component makes an API call to retrieve the filtered data set. It then loops through those list rows and only displays the appropriate columns using JavaScript mapping.

Sensitive data stays protected on the server while the rendered view is customized for the user’s access level.

Row-Level Security Techniques

A major advantage of client-side rendering is the ability to apply security at the row level within SharePoint lists. Some techniques include:

• Using user profiles to filter row data
• Hiding columns based on permissions
• Examples: Checking group membership with JS

Using Profiles to Filter Row Data

SharePoint’s user profiles system contains useful context like department, location, and job role. CSR code can tap into user profiles to filter row data dynamically.

For example, as a user navigates a knowledge base, row data could hide solution notes not applicable to that user’s department. Similar filtering could apply regionally or limit data based on seniority.

Hiding Columns Based on Permissions

Instead of entirely hiding rows of data, column-level security can also be implemented with CSR. Certain columns containing sensitive information may only be visible to users with sufficient permissions.

For example, employee salary and performance data could return with the row but not render those specific columns for unauthorized viewers. So managers still see employee records, just with certain fields hidden.

Examples: Checking Group Membership with JS

JavaScript in CSR components can check user group membership to alter visible data. For example:


SP.Web.currentUser.groups.get().then(groups => {

if (groups.includes('Managers')) {
// show salary column
}

})


This allows the component to see if the current user is in the Managers group and conditionally display salary data.

Additional Considerations

When implementing CSR, teams should factor in elements like performance, debugging, and authentication:

• Caching and performance
• Debugging client-side code
• Integrating with authentication

Caching and Performance

The volume of filtered data and frequency of API calls can impact performance. Caching and request throttling should be implemented to optimize response times.

Consider caching filtered data sets that do not change often. Authentication tokens can also be cached client-side to reduce login requests.

Debugging Client-Side Code

Browser developer tools are critical for debugging CSR components like React. Debugging locally vs. on SharePoint can yield different results.

Use console logging to output the filtered data sets returned. Verify user context information like profiles and permissions in client-side code.

Integrating with Authentication

SharePoint’s authentication should be extended to CSR endpoints to check permissions. Client-side calls may need to pass the user’s security context and tokens to the API.

Understand how CSR interfaces with identity providers like SAML or OAuth. Block API access if user cannot be verified.

Summary

Client-side rendering is a powerful way to improve SharePoint list security:

• Limits exposed data through filtered data sets
• Enables dynamic row-level security policies
• Reduces attack surface area for injection risks

When implementing CSR, optimize performance and auth integrations. Client-side rendering represents the future for secure, customizable SharePoint interfaces.