MFA Verification Hook

You can add additional checks to the Supabase MFA implementation with hooks. For example, you can:

• Limit the number of verification attempts performed over a period of time.
• Sign out users who have too many invalid verification attempts.
• Count, rate limit, or ban sign-ins.

Inputs

Supabase Auth will send a payload containing these fields to your hook:

Field

Type

Description

factor_id

string

Unique identifier for the MFA factor being verified

factor_type

string

totp or phone

user_id

string

Unique identifier for the user

valid

boolean

Whether the verification attempt was valid. For TOTP, this means that the six digit code was correct (true) or incorrect (false).

1{2  "factor_id": "6eab6a69-7766-48bf-95d8-bd8f606894db",3  "user_id": "3919cb6e-4215-4478-a960-6d3454326cec",4  "valid": true5}

Outputs

Return this if your hook processed the input without errors.

Field

Type

Description

decision

string

The decision on whether to allow authentication to move forward. Use reject to deny the verification attempt and log the user out of all active sessions. Use continue to use the default Supabase Auth behavior.

message

string

The message to show the user if the decision was reject.

1{2  "decision": "reject",3  "message": "You have exceeded maximum number of MFA attempts."4}

Your company requires that a user can input an incorrect MFA Verification code no more than once every 2 seconds.

Create a table to record the last time a user had an incorrect MFA verification attempt for a factor.

1create table public.mfa_failed_verification_attempts (2  user_id uuid not null,3  factor_id uuid not null,4  last_failed_at timestamp not null default now(),5  primary key (user_id, factor_id)6);

Create a hook to read and write information to this table. For example:

1create function public.hook_mfa_verification_attempt(event jsonb)2  returns jsonb3  language plpgsql4as $$5  declare6    last_failed_at timestamp;7  begin8    if event->'valid' is true then9      -- code is valid, accept it10      return jsonb_build_object('decision', 'continue');11    end if;1213    select last_failed_at into last_failed_at14      from public.mfa_failed_verification_attempts15      where16        user_id = event->'user_id'17          and18        factor_id = event->'factor_id';1920    if last_failed_at is not null and now() - last_failed_at < interval '2 seconds' then21      -- last attempt was done too quickly22      return jsonb_build_object(23        'error', jsonb_build_object(24          'http_code', 429,25          'message',   'Please wait a moment before trying again.'26        )27      );28    end if;2930    -- record this failed attempt31    insert into public.mfa_failed_verification_attempts32      (33        user_id,34        factor_id,35        last_refreshed_at36      )37      values38      (39        event->'user_id',40        event->'factor_id',41        now()42      )43      on conflict do update44        set last_refreshed_at = now();4546    -- finally let Supabase Auth do the default behavior for a failed attempt47    return jsonb_build_object('decision', 'continue');48  end;49$$;5051-- Assign appropriate permissions and revoke access52grant all53  on table public.mfa_failed_verification_attempts54  to supabase_auth_admin;5556revoke all57  on table public.mfa_failed_verification_attempts58  from authenticated, anon, public;