Securing your API
The data APIs are designed to work with Postgres Row Level Security (RLS). If you use Supabase Auth, you can restrict data based on the logged-in user.
To control access to your data, you can use Policies.
Enabling row level security
Any table you create in the public
schema will be accessible via the Supabase Data API.
To restrict access, enable Row Level Security (RLS) on all tables, views, and functions in the public
schema. You can then write RLS policies to grant users access to specific database rows or functions based on their authentication token.
Always enable Row Level Security on tables, views, and functions in the public
schema to protect your data.
Any table created through the Supabase Dashboard will have RLS enabled by default. If you created the tables via the SQL editor or via another way, enable RLS like so:
- Go to the Authentication > Policies page in the Dashboard.
- Select Enable RLS to enable Row Level Security.
With RLS enabled, you can create Policies that allow or disallow users to access and update data. We provide a detailed guide for creating Row Level Security Policies in our Authorization documentation.
Any table without RLS enabled in the public
schema will be accessible to the public, using the anon
role. Always make sure that RLS is enabled or that you've got other security measures in place to avoid unauthorized access to your project's data!
Disable the API or restrict to custom schema
If you don't use the Data API, or if you don't want to expose the public
schema, you can either disable it entirely or change the automatically exposed schema to one of your choice. See Hardening the Data API for instructions.
Enforce additional rules on each request
Using Row Level Security policies may not always be adequate or sufficient to protect APIs.
Here are some common situations where additional protections are necessary:
- Enforcing per-IP or per-user rate limits.
- Checking custom or additional API keys before allowing further access.
- Rejecting requests after exceeding a quota or requiring payment.
- Disallowing direct access to certain tables, views or functions in the
public
schema.
You can build these cases in your application by creating a Postgres function that will read information from the request and perform additional checks, such as counting the number of requests received or checking that an API key is already registered in your database before serving the response.
Define a function like so:
And register it to run on every Data API request using:
This configures the public.check_request
function to run on every Data API request. To have the changes take effect, you should run:
Inside the function you can perform any additional checks on the request headers or JWT and raise an exception to prevent the request from completing. For example, this exception raises a HTTP 402 Payment Required response with a hint
and additional X-Powered-By
header:
When raised within the public.check_request
function, the resulting HTTP response will look like:
Use the JSON operator functions to build rich and dynamic responses from exceptions.
If you use a custom HTTP status code like 419, you can supply the status_text
key in the detail
clause of the exception to describe the HTTP status.
If you're using PostgREST version 11 or lower (find out your PostgREST version) a different and less powerful syntax needs to be used.
Accessing request information
Like with RLS policies, you can access information about the request by using the current_setting()
Postgres function. Here are some examples on how this works:
current_setting() | Example | Description |
---|---|---|
request.method | GET , HEAD , POST , PUT , PATCH , DELETE | Request's method |
request.path | table | Table's path |
request.path | view | View's path |
request.path | rpc/function | Functions's path |
request.headers | { "User-Agent": "...", ... } | JSON object of the request's headers |
request.cookies | { "cookieA": "...", "cookieB": "..." } | JSON object of the request's cookies |
request.jwt | { "sub": "a7194ea3-...", ... } | JSON object of the JWT payload |
To access the IP address of the client look up the X-Forwarded-For header in the request.headers
setting. For example:
Read more about PostgREST's pre-request function.
Examples
You can only rate-limit POST
, PUT
, PATCH
and DELETE
requests. This is because GET
and HEAD
requests run in read-only mode, and will be served by Read Replicas which do not support writing to the database.
Outline:
- A new row is added to a
private.rate_limits
table each time a modifying action is done to the database containing the IP address and the timestamp of the action. - If there are over 100 requests from the same IP address in the last 5 minutes, the request is rejected with a HTTP 420 code.
Create the table:
The private
schema is used as it cannot be accessed over the API!
Create the public.check_request
function:
Finally, configure the public.check_request()
function to run on every Data API request:
To clear old entries in the private.rate_limits
table, set up a pg_cron job to clean them up.