Multi-Factor Authentication
Multi-factor authentication (MFA), sometimes called two-factor authentication (2FA), adds an additional layer of security to your application by verifying their identity through additional verification steps.
It is considered a best practice to use MFA for your applications.
Users with weak passwords or compromised social login accounts are prone to malicious account takeovers. These can be prevented with MFA because they require the user to provide proof of both of these:
- Something they know. Password, or access to a social-login account.
- Something they have. Access to an authenticator app (a.k.a. TOTP), mobile phone or recovery code.
Overview
Supabase Auth implements only Time-based One Time Password(TOTP) multi-factor authentication. This type of multi-factor authentication uses a timed one-time password generated from an authenticator app in the control of users. The MFA API is enabled on all Supabase projects by default.
Applications using MFA require two important flows:
- Enrollment flow. This lets users set up and control MFA in your app.
- Authentication flow. This lets users sign in using any factors after the conventional login step.
Supabase Auth provides:
- Enrollment API - build rich user interfaces for adding and removing factors.
- Challenge and Verify APIs - securely verify that the user has access to a factor.
- List Factors API - build rich user interfaces for signing in with additional factors.
Below is a flow chart illustrating how these APIs work together to enable MFA features in your app.
These sets of APIs let you control the MFA experience that works for you. You can create flows where MFA is optional, mandatory for all, or only specific groups of users.
Once users have enrolled or signed-in with a factor, Supabase Auth adds additional metadata to the user's access token (JWT) that your application can use to allow or deny access.
This information is represented by an Authenticator Assurance Level, a standard measure about the assurance of the user's identity Supabase Auth has for that particular session. There are two levels recognized today:
- Assurance Level 1:
aal1
Means that the user's identity was verified using a conventional login method such as email+password, magic link, one-time password, phone auth or social login. - Assurance Level 2:
aal2
Means that the user's identity was additionally verified using at least one second factor, such as a TOTP code.
This assurance level is encoded in the aal
claim in the JWT associated with the user. By decoding this value you can create custom authorization rules in your frontend, backend, and database that will enforce the MFA policy that works for your application. JWTs without an aal
claim are at the aal1
level.
Adding to your app
Adding MFA to your app involves these four steps:
- Add enrollment flow. You need to provide a UI within your app that your users will be able to set-up MFA in. You can add this right after sign-up, or as part of a separate flow in the settings portion of your app.
- Add unenrollment flow. You need to support a UI through which users can see existing devices and unenroll devices which are no longer relevant.
- Add challenge step to login. If a user has set-up MFA, your app's login flow needs to present a challenge screen to the user asking them to prove they have access to the additional factor.
- Enforce rules for MFA logins. Once your users have a way to enroll and log in with MFA, you need to enforce authorization rules across your app: on the frontend, backend, API servers or Row-Level Security policies.
Add enrollment flow
An enrollment flow provides a UI for users to set up additional authentication factors. Most applications add the enrollment flow in two places within their app:
- Right after login or sign up. This lets users quickly set up MFA immediately after they log in or create an account. We recommend encouraging all users to set up MFA if that makes sense for your application. Many applications offer this as an opt-in step in an effort to reduce onboarding friction.
- From within a settings page. Allows users to set up, disable or modify their MFA settings.
We recommend building one generic flow that you can reuse in both cases with minor modifications.
Enrolling a factor for use with MFA takes three steps:
- Call
supabase.auth.mfa.enroll()
. This method returns a QR code and a secret. Display the QR code to the user and ask them to scan it with their authenticator application. If they are unable to scan the QR code, show the secret in plain text which they can type or paste into their authenticator app. - Calling the
supabase.auth.mfa.challenge()
API. This prepares Supabase Auth to accept a verification code from the user and returns a challenge ID. - Calling the
supabase.auth.mfa.verify()
API. This verifies that the user has indeed added the secret from step (1) into their app and is working correctly. If the verification succeeds, the factor immediately becomes active for the user account. If not, you should repeat steps 2 and 3.
Example: React
Below is an example that creates a new EnrollMFA
component that illustrates the important pieces of the MFA enrollment flow.
- When the component appears on screen, the
supabase.auth.mfa.enroll()
API is called once to start the process of enrolling a new factor for the current user. - This API returns a QR code in the SVG format, which is shown on screen using
a normal
<img>
tag by encoding the SVG as a data URL. - Once the user has scanned the QR code with their authenticator app, they
should enter the verification code within the
verifyCode
input field and click onEnable
. - A challenge is created using the
supabase.auth.mfa.challenge()
API and the code from the user is submitted for verification using thesupabase.auth.mfa.verify()
challenge. onEnabled
is a callback that notifies the other components that enrollment has completed.onCancelled
is a callback that notifies the other components that the user has clicked theCancel
button.
_76/**_76 * EnrollMFA shows a simple enrollment dialog. When shown on screen it calls_76 * the `enroll` API. Each time a user clicks the Enable button it calls the_76 * `challenge` and `verify` APIs to check if the code provided by the user is_76 * valid._76 * When enrollment is successful, it calls `onEnrolled`. When the user clicks_76 * Cancel the `onCancelled` callback is called._76 */_76export function EnrollMFA({_76 onEnrolled,_76 onCancelled,_76}: {_76 onEnrolled: () => void_76 onCancelled: () => void_76}) {_76 const [factorId, setFactorId] = useState('')_76 const [qr, setQR] = useState('') // holds the QR code image SVG_76 const [verifyCode, setVerifyCode] = useState('') // contains the code entered by the user_76 const [error, setError] = useState('') // holds an error message_76_76 const onEnableClicked = () => {_76 setError('')_76 ;(async () => {_76 const challenge = await supabase.auth.mfa.challenge({ factorId })_76 if (challenge.error) {_76 setError(challenge.error.message)_76 throw challenge.error_76 }_76_76 const challengeId = challenge.data.id_76_76 const verify = await supabase.auth.mfa.verify({_76 factorId,_76 challengeId,_76 code: verifyCode,_76 })_76 if (verify.error) {_76 setError(verify.error.message)_76 throw verify.error_76 }_76_76 onEnrolled()_76 })()_76 }_76_76 useEffect(() => {_76 ;(async () => {_76 const { data, error } = await supabase.auth.mfa.enroll({_76 factorType: 'totp',_76 })_76 if (error) {_76 throw error_76 }_76_76 setFactorId(data.id)_76_76 // Supabase Auth returns an SVG QR code which you can convert into a data_76 // URL that you can place in an <img> tag._76 setQR(data.totp.qr_code)_76 })()_76 }, [])_76_76 return (_76 <>_76 {error && <div className="error">{error}</div>}_76 <img src={qr} />_76 <input_76 type="text"_76 value={verifyCode}_76 onChange={(e) => setVerifyCode(e.target.value.trim())}_76 />_76 <input type="button" value="Enable" onClick={onEnableClicked} />_76 <input type="button" value="Cancel" onClick={onCancelled} />_76 </>_76 )_76}
Add unenrollment flow
An unenrollment flow provides a UI for users to manage and unenroll factors linked to their accounts. Most applications do so via a factor management page where users can view and unlink selected factors.
When a user unenrolls a factor, call supabase.auth.mfa.unenroll()
with the ID of the factor. For example, call supabase.auth.mfa.unenroll({factorId: "d30fd651-184e-4748-a928-0a4b9be1d429"})
to unenroll a factor with ID d30fd651-184e-4748-a928-0a4b9be1d429
.
Example: React
Below is an example that creates a new UnenrollMFA
component that illustrates the important pieces of the MFA enrollment flow. Note that users can only unenroll a factor after completing the enrollment flow and obtaining an aal2
JWT claim. Here are some points of note:
- When the component appears on screen, the
supabase.auth.mfa.listFactors()
endpoint fetches all existing factors together with their details. - The existing factors for a user are displayed in a table.
- Once the user has selected a factor to unenroll, they can type in the factorId and click Unenroll which creates a confirmation modal.
Unenrolling a factor will downgrade the assurance level from aal2
to aal1
only after the refresh interval has lapsed. For an immediate downgrade from aal2
to aal1
after enrolling one will need to manually call refreshSession()
_44/**_44 * UnenrollMFA shows a simple table with the list of factors together with a button to unenroll._44 * When a user types in the factorId of the factor that they wish to unenroll and clicks unenroll_44 * the corresponding factor will be unenrolled._44 */_44export function UnenrollMFA() {_44 const [factorId, setFactorId] = useState('')_44 const [factors, setFactors] = useState([])_44 const [error, setError] = useState('') // holds an error message_44_44 useEffect(() => {_44 ;(async () => {_44 const { data, error } = await supabase.auth.mfa.listFactors()_44 if (error) {_44 throw error_44 }_44_44 setFactors(data.totp)_44 })()_44 }, [])_44_44 return (_44 <>_44 {error && <div className="error">{error}</div>}_44 <tbody>_44 <tr>_44 <td>Factor ID</td>_44 <td>Friendly Name</td>_44 <td>Factor Status</td>_44 </tr>_44 {factors.map((factor) => (_44 <tr>_44 <td>{factor.id}</td>_44 <td>{factor.friendly_name}</td>_44 <td>{factor.factor_type}</td>_44 <td>{factor.status}</td>_44 </tr>_44 ))}_44 </tbody>_44 <input type="text" value={verifyCode} onChange={(e) => setFactorId(e.target.value.trim())} />_44 <button onClick={() => supabase.auth.mfa.unenroll({ factorId })}>Unenroll</button>_44 </>_44 )_44}
Add challenge step to login
Once a user has logged in via their first factor (email+password, magic link, one time password, social login etc.) you need to perform a check if any additional factors need to be verified.
This can be done by using the supabase.auth.mfa.getAuthenticatorAssuranceLevel()
API. When the user signs in and is redirected back to your app, you should call this method to extract the user's current and next authenticator assurance level (AAL).
Therefore if you receive a currentLevel
which is aal1
but a nextLevel
of aal2
, the user should be given the option to go through MFA.
Below is a table that explains the combined meaning.
Current Level | Next Level | Meaning |
---|---|---|
aal1 | aal1 | User does not have MFA enrolled. |
aal1 | aal2 | User has an MFA factor enrolled but has not verified it. |
aal2 | aal2 | User has verified their MFA factor. |
aal2 | aal1 | User has disabled their MFA factor. (Stale JWT.) |
Example: React
Adding the challenge step to login depends heavily on the architecture of your app. However, a fairly common way to structure React apps is to have a large component (often named App
) which contains most of the authenticated application logic.
This example will wrap this component with logic that will show an MFA challenge screen if necessary, before showing the full application. This is illustrated in the AppWithMFA
example below.
_33function AppWithMFA() {_33 const [readyToShow, setReadyToShow] = useState(false)_33 const [showMFAScreen, setShowMFAScreen] = useState(false)_33_33 useEffect(() => {_33 ;(async () => {_33 try {_33 const { data, error } = await supabase.auth.mfa.getAuthenticatorAssuranceLevel()_33 if (error) {_33 throw error_33 }_33_33 console.log(data)_33_33 if (data.nextLevel === 'aal2' && data.nextLevel !== data.currentLevel) {_33 setShowMFAScreen(true)_33 }_33 } finally {_33 setReadyToShow(true)_33 }_33 })()_33 }, [])_33_33 if (readyToShow) {_33 if (showMFAScreen) {_33 return <AuthMFA />_33 }_33_33 return <App />_33 }_33_33 return <></>_33}
supabase.auth.mfa.getAuthenticatorAssuranceLevel()
does return a promise. Don't worry, this is a very fast method (microseconds) as it rarely uses the network.readyToShow
only makes sure the AAL check completes before showing any application UI to the user.- If the current level can be upgraded to the next one, the MFA screen is shown.
- Once the challenge is successful, the
App
component is finally rendered on screen.
Below is the component that implements the challenge and verify logic.
_53function AuthMFA() {_53 const [verifyCode, setVerifyCode] = useState('')_53 const [error, setError] = useState('')_53_53 const onSubmitClicked = () => {_53 setError('')_53 ;(async () => {_53 const factors = await supabase.auth.mfa.listFactors()_53 if (factors.error) {_53 throw factors.error_53 }_53_53 const totpFactor = factors.data.totp[0]_53_53 if (!totpFactor) {_53 throw new Error('No TOTP factors found!')_53 }_53_53 const factorId = totpFactor.id_53_53 const challenge = await supabase.auth.mfa.challenge({ factorId })_53 if (challenge.error) {_53 setError(challenge.error.message)_53 throw challenge.error_53 }_53_53 const challengeId = challenge.data.id_53_53 const verify = await supabase.auth.mfa.verify({_53 factorId,_53 challengeId,_53 code: verifyCode,_53 })_53 if (verify.error) {_53 setError(verify.error.message)_53 throw verify.error_53 }_53 })()_53 }_53_53 return (_53 <>_53 <div>Please enter the code from your authenticator app.</div>_53 {error && <div className="error">{error}</div>}_53 <input_53 type="text"_53 value={verifyCode}_53 onChange={(e) => setVerifyCode(e.target.value.trim())}_53 />_53 <input type="button" value="Submit" onClick={onSubmitClicked} />_53 </>_53 )_53}
- You can extract the available MFA factors for the user by calling
supabase.auth.mfa.listFactors()
. Don't worry this method is also very quick and rarely uses the network. - If
listFactors()
returns more than one factor (or of a different type) you should present the user with a choice. For simplicity this is not shown in the example. - Each time the user presses the "Submit" button a new challenge is created for the chosen factor (in this case the first one) and it is immediately verified. Any errors are displayed to the user.
- On successful verification, the client library will refresh the session in
the background automatically and finally call the
onSuccess
callback, which will show the authenticatedApp
component on screen.
Enforce rules for MFA logins
Adding MFA to your app's UI does not in-and-of-itself offer a higher level of security to your users. You also need to enforce the MFA rules in your application's database, APIs, and server-side rendering.
Depending on your application's needs, there are three ways you can choose to enforce MFA.
- Enforce for all users (new and existing). Any user account will have to enroll MFA to continue using your app. The application will not allow access without going through MFA first.
- Enforce for new users only. Only new users will be forced to enroll MFA, while old users will be encouraged to do so. The application will not allow access for new users without going through MFA first.
- Enforce only for users that have opted-in. Users that want MFA can enroll in it and the application will not allow access without going through MFA first.
Database
Your app should sufficiently deny or allow access to tables or rows based on the user's current and possible authenticator levels.
PostgreSQL has two types of policies: permissive and restrictive. This guide uses restrictive policies. Make sure you don't omit the as restrictive
clause.
Enforce for all users (new and existing)
If your app falls under this case, this is a template Row Level Security policy you can apply to all your tables:
_10create policy "Policy name."_10 on table_name_10 as restrictive_10 to authenticated_10 using ((select auth.jwt()->>'aal') = 'aal2');
- Here the policy will not accept any JWTs with an
aal
claim other thanaal2
, which is the highest authenticator assurance level. - Using
as restrictive
ensures this policy will restrict all commands on the table regardless of other policies!
Enforce for new users only
If your app falls under this case, the rules get more complex. User accounts created past a certain timestamp must have a aal2
level to access the database.
_13create policy "Policy name."_13 on table_name_13 as restrictive -- very important!_13 to authenticated_13 using_13 (array[(select auth.jwt()->>'aal')] <@ (_13 select_13 case_13 when created_at >= '2022-12-12T00:00:00Z' then array['aal2']_13 else array['aal1', 'aal2']_13 end as aal_13 from auth.users_13 where (select auth.uid()) = id));
- The policy will accept both
aal1
andaal2
for users with acreated_at
timestamp prior to 12th December 2022 at 00:00 UTC, but will only acceptaal2
for all other timestamps. - The
<@
operator is PostgreSQL's "contained in" operator. - Using
as restrictive
ensures this policy will restrict all commands on the table regardless of other policies!
Enforce only for users that have opted-in
Users that have enrolled MFA on their account are expecting that your application only works for them if they've gone through MFA.
_14create policy "Policy name."_14 on table_name_14 as restrictive -- very important!_14 to authenticated_14 using (_14 array[(select auth.jwt()->>'aal')] <@ (_14 select_14 case_14 when count(id) > 0 then array['aal2']_14 else array['aal1', 'aal2']_14 end as aal_14 from auth.mfa_factors_14 where ((select auth.uid()) = user_id) and status = 'verified'_14 ));
- The policy will only accept only
aal2
when the user has at least one MFA factor verified. - Otherwise, it will accept both
aal1
andaal2
. - The
<@
operator is PostgreSQL's "contained in" operator. - Using
as restrictive
ensures this policy will restrict all commands on the table regardless of other policies!
Server-Side Rendering
When using the Supabase JavaScript library in a server-side rendering context, make sure you always create a new object for each request! This will prevent you from accidentally rendering and serving content belonging to different users.
It is possible to enforce MFA on the Server-Side Rendering level. However, this can be tricky do to well.
You can use the supabase.auth.mfa.getAuthenticatorAssuranceLevel()
and supabase.auth.mfa.listFactors()
APIs to identify the AAL level of the session and any factors that are enabled for a user, similar to how you would use these on the browser.
However, encountering a different AAL level on the server may not actually be a security problem. Consider these likely scenarios:
- User signed-in with a conventional method but closed their tab on the MFA flow.
- User forgot a tab open for a very long time. (This happens more often than you might imagine.)
- User has lost their authenticator device and is confused about the next steps.
We thus recommend you redirect users to a page where they can authenticate using their additional factor, instead of rendering a HTTP 401 Unauthorized or HTTP 403 Forbidden content.
APIs
If your application uses the Supabase Database, Storage or Edge Functions, just using Row Level Security policies will give you sufficient protection. In the event that you have other APIs that you wish to protect, follow these general guidelines:
- Use a good JWT verification and parsing library for your language. This will let you securely parse JWTs and extract their claims.
- Retrieve the
aal
claim from the JWT and compare its value according to your needs. If you've encountered an AAL level that can be increased, ask the user to continue the login process instead of logging them out. - Use the
https://<project-ref>.supabase.co/rest/v1/auth/factors
REST endpoint to identify if the user has enrolled any MFA factors. Onlyverified
factors should be acted upon.
Frequently asked questions
Why is there a challenge and verify API when challenge does not do much?
TOTP is not going to be the only MFA factor Supabase Auth is going to support in the future. By separating out the challenge and verify steps, we're making the library forward compatible with new factors we may add in the future -- such as SMS or WebAuthn. For example, for SMS the challenge
endpoint would actually send out the SMS with the authentication code. For convenience, you may use challengeAndVerify
to create and verify a challenge in a single step.
What's inside the QR code?
The TOTP QR code encodes a URI with the otpauth
scheme. It was initially introduced by Google Authenticator but is now universally accepted by all authenticator apps.
How long is the TOTP code valid for?
In our TOTP implementation, each generated code remains valid for one interval, which spans 30 seconds. To account for minor time discrepancies, we allow for a one-interval clock skew. This ensures that users can successfully authenticate within this timeframe, even if there are slight variations in system clocks.
How do I check when a user went through MFA?
Access tokens issued by Supabase Auth contain an amr
(Authentication Methods Reference) claim. It is an array of objects that indicate what authentication methods the user has used so far.
For example, the following structure describes a user that first signed in with a password-based method, and then went through TOTP MFA 2 minutes and 12 seconds later. The entries are ordered most recent method first!
_12{_12 "amr": [_12 {_12 "method": "totp",_12 "timestamp": 1666086056_12 },_12 {_12 "method": "password",_12 "timestamp": 1666085924_12 }_12 ]_12}
Use the supabase.auth.mfa.getAuthenticatorAssuranceLevel()
method to get easy access to this information in your browser app.
You can use this PostgreSQL snippet in RLS policies, too:
_10jsonb_path_query((select auth.jwt()), '$.amr[0]')
jsonb_path_query(json, path)
is a function that allows access to elements in a JSON object according to a SQL/JSON path.$.amr[0]
is a SQL/JSON path expression that fetches the most recent authentication method in the JWT.
Once you have extracted the most recent entry in the array, you can compare the method
and timestamp
to enforce stricter rules. For instance, you can mandate that access will be only be granted on a table to users who have recently signed in with a password.
Currently recognized authentication methods are:
oauth
- any OAuth based sign in (social login).password
- any password based sign in.otp
- any one-time password based sign in (email code, SMS code, magic link).totp
- a TOTP additional factor.sso/saml
- any Single Sign On (SAML) method.
The following additional claims are available when using PKCE flow:
invite
- any sign in via an invitation.magiclink
- any sign in via magic link. Excludes logins resulting from invocation ofsignUp
.email/signup
- any login resulting from an email signup.email_change
- any login resulting from a change in email.
More authentication methods will be added over time as we increase the number of authentication methods supported by Supabase.