Which UI do you use?

Custom UI

Pre built UI

Passwordless login via allow list

We need to start by maintaining an allow list of emails. You can either store this list in your own database, or then use the metadata feature provided by SuperTokens to store this. This may seem like a strange use case of the user metadata recipe we provide, but it works.

You want to implement the following functions on your backend:

NodeJS

Important

For other backend frameworks, you can follow our guide on how to spin up a separate server configured with the SuperTokens backend SDK to authenticate requests and issue session tokens.

GoLang

import UserMetadata from "supertokens-node/recipe/usermetadata"

async function addEmailToAllowlist(email: string) {
    let existingData = await UserMetadata.getUserMetadata("emailAllowList");
    let allowList: string[] = existingData.metadata.allowList || [];
    allowList = [...allowList, email];
    await UserMetadata.updateUserMetadata("emailAllowList", {
        allowList
    });
}

async function isEmailAllowed(email: string) {
    let existingData = await UserMetadata.getUserMetadata("emailAllowList");
    let allowList: string[] = existingData.metadata.allowList || [];
    return allowList.includes(email);
}

async function addPhoneNumberToAllowlist(phoneNumber: string) {
    let existingData = await UserMetadata.getUserMetadata("phoneNumberAllowList");
    let allowList: string[] = existingData.metadata.allowList || [];
    allowList = [...allowList, phoneNumber];
    await UserMetadata.updateUserMetadata("phoneNumberAllowList", {
        allowList
    });
}

async function isPhoneNumberAllowed(phoneNumber: string) {
    let existingData = await UserMetadata.getUserMetadata("phoneNumberAllowList");
    let allowList: string[] = existingData.metadata.allowList || [];
    return allowList.includes(phoneNumber);
}

Python

import "github.com/supertokens/supertokens-golang/recipe/usermetadata"

func addEmailToAllowlist(email string) error {
    existingData, err := usermetadata.GetUserMetadata("emailAllowList")
    if err != nil {
        return err
    }
    allowList := []string{}
    allowListFromMetadata, ok := existingData["allowList"].([]string)
    if ok {
        allowList = allowListFromMetadata
    }
    allowList = append(allowList, email)
    _, err = usermetadata.UpdateUserMetadata("emailAllowList", map[string]interface{}{
        "allowList": allowList,
    })
    return err
}

func isEmailAllowed(email string) (bool, error) {
    existingData, err := usermetadata.GetUserMetadata("emailAllowList")
    if err != nil {
        return false, err
    }
    allowList := []string{}
    allowListFromMetadata, ok := existingData["allowList"].([]string)
    if ok {
        allowList = allowListFromMetadata
    }
    for _, allowedEmail := range allowList {
        if allowedEmail == email {
            return true, nil
        }
    }
    return false, nil
}

func addPhoneNumberToAllowlist(phoneNumber string) error {
    existingData, err := usermetadata.GetUserMetadata("phoneNumberAllowList")
    if err != nil {
        return err
    }
    allowList := []string{}
    allowListFromMetadata, ok := existingData["allowList"].([]string)
    if ok {
        allowList = allowListFromMetadata
    }
    allowList = append(allowList, phoneNumber)
    _, err = usermetadata.UpdateUserMetadata("phoneNumberAllowList", map[string]interface{}{
        "allowList": allowList,
    })
    return err
}

func isPhoneNumberAllowed(phoneNumber string) (bool, error) {
    existingData, err := usermetadata.GetUserMetadata("phoneNumberAllowList")
    if err != nil {
        return false, err
    }
    allowList := []string{}
    allowListFromMetadata, ok := existingData["allowList"].([]string)
    if ok {
        allowList = allowListFromMetadata
    }
    for _, allowedPhoneNumber := range allowList {
        if allowedPhoneNumber == phoneNumber {
            return true, nil
        }
    }
    return false, nil
}

Other Frameworks

from supertokens_python.recipe.usermetadata.asyncio import get_user_metadata, update_user_metadata
from typing import List

async def add_email_to_allow_list(email: str):
    metadataResult = await get_user_metadata("emailAllowList")
    allow_list: List[str] = metadataResult.metadata["allowList"] if "allowList" in metadataResult.metadata else []
    allow_list.append(email)
    await update_user_metadata("emailAllowList", {
        "allowList": allow_list
    })

async def is_email_allowed(email: str):
    metadataResult = await get_user_metadata("emailAllowList")
    allow_list: List[str] = metadataResult.metadata["allowList"] if "allowList" in metadataResult.metadata else []
    return email in allow_list

async def add_phone_number_to_allow_list(phone_number: str):
    metadataResult = await get_user_metadata("phoneNumberAllowList")
    allow_list: List[str] = metadataResult.metadata["allowList"] if "allowList" in metadataResult.metadata else []
    allow_list.append(phone_number)
    await update_user_metadata("phoneNumberAllowList", {
        "allowList": allow_list
    })

async def is_phone_number_allowed(phone_number: str):
    metadataResult = await get_user_metadata("phoneNumberAllowList")
    allow_list: List[str] = metadataResult.metadata["allowList"] if "allowList" in metadataResult.metadata else []
    return phone_number in allow_list

important

Remember to initialise the user metadata recipe on the backend recipeList during supertokens.init.

Multi Tenancy

For a multi tenant setup, you can even store an allow list per tenant. This would allow you to limit sign ups for different emails / phone numbers for different tenants. If you are doing this, then you would also need to pass in the tenantID to the functions above, which you can obtain from the input to the api overrides shown below.

After that, we override the createCodePOST API to check if the input email / phone number is allowed durign sign up. If not allowed, we send back a user friendly message to the frontend.

NodeJS

Important

For other backend frameworks, you can follow our guide on how to spin up a separate server configured with the SuperTokens backend SDK to authenticate requests and issue session tokens.

GoLang

import Passwordless from "supertokens-node/recipe/passwordless";

Passwordless.init({
    override: {
        apis: (originalImplementation) => {
            return {
                ...originalImplementation,
                createCodePOST: async function (input) {
                    if ("email" in input) {
                        let existingUser = await Passwordless.getUserByEmail({
                            email: input.email,
                            tenantId: input.tenantId
                        });
                        if (existingUser === undefined) {
                            // this is sign up attempt
                            if (!(await isEmailAllowed(input.email))) {
                                return {
                                    status: "GENERAL_ERROR",
                                    message: "Sign up disabled. Please contact the admin."
                                }
                            }
                        }
                    } else {
                        let existingUser = await Passwordless.getUserByPhoneNumber({
                            phoneNumber: input.phoneNumber,
                            tenantId: input.tenantId
                        });
                        if (existingUser === undefined) {
                            // this is sign up attempt
                            if (!(await isPhoneNumberAllowed(input.phoneNumber))) {
                                return {
                                    status: "GENERAL_ERROR",
                                    message: "Sign up disabled. Please contact the admin."
                                }
                            }
                        }
                    }
                    return await originalImplementation.createCodePOST!(input);
                }
            }
        }
    }
})

Python

import (
    "github.com/supertokens/supertokens-golang/recipe/passwordless"
    "github.com/supertokens/supertokens-golang/recipe/passwordless/plessmodels"
    "github.com/supertokens/supertokens-golang/supertokens"
)

func isEmailAllowed(email string) (bool, error) {
    // ... from previous code snippet
    return false, nil
}

func isPhoneNumberAllowed(phoneNumber string) (bool, error) {
    // ... from previous code snippet
    return false, nil
}

func main() {
    passwordless.Init(plessmodels.TypeInput{
        Override: &plessmodels.OverrideStruct{
            APIs: func(originalImplementation plessmodels.APIInterface) plessmodels.APIInterface {
                originalCreateCodePOST := *originalImplementation.CreateCodePOST

                (*originalImplementation.CreateCodePOST) = func(email, phoneNumber *string, options plessmodels.APIOptions, userContext supertokens.UserContext) (plessmodels.CreateCodePOSTResponse, error) {

                    if email != nil {
                        existingUser, err := passwordless.GetUserByEmail(*email)
                        if err != nil {
                            return plessmodels.CreateCodePOSTResponse{}, err
                        }
                        if existingUser == nil {
                            // sign up attempt
                            emailAllowed, err := isEmailAllowed(*email)
                            if err != nil {
                                return plessmodels.CreateCodePOSTResponse{}, err
                            }
                            if !emailAllowed {
                                return plessmodels.CreateCodePOSTResponse{
                                    GeneralError: &supertokens.GeneralErrorResponse{
                                        Message: "Sign ups are disabled. Please contact the admin.",
                                    },
                                }, nil
                            }
                        }
                    } else {
                        existingUser, err := passwordless.GetUserByPhoneNumber(*phoneNumber)
                        if err != nil {
                            return plessmodels.CreateCodePOSTResponse{}, err
                        }
                        if existingUser == nil {
                            // sign up attempt
                            phoneNumberAllowed, err := isPhoneNumberAllowed(*phoneNumber)
                            if err != nil {
                                return plessmodels.CreateCodePOSTResponse{}, err
                            }
                            if !phoneNumberAllowed {
                                return plessmodels.CreateCodePOSTResponse{
                                    GeneralError: &supertokens.GeneralErrorResponse{
                                        Message: "Sign ups are disabled. Please contact the admin.",
                                    },
                                }, nil
                            }
                        }
                    }
                    return originalCreateCodePOST(email, phoneNumber, options, userContext)
                }

                return originalImplementation
            },
        },
    })
}

Other Frameworks

from supertokens_python import init, InputAppInfo
from supertokens_python.types import GeneralErrorResponse
from supertokens_python.recipe import passwordless
from supertokens_python.recipe.passwordless.asyncio import get_user_by_email, get_user_by_phone_number
from supertokens_python.recipe.passwordless.interfaces import APIInterface, CreateCodePostOkResult, APIOptions
from typing import Union, Dict, Any


async def is_email_allowed(email: str):
    # from previous code snippet..
    return False


async def is_phone_number_allowed(phone_number: str):
    # from previous code snippet..
    return False


def override_passwordless_apis(original_implementation: APIInterface):
    original_create_code_post = original_implementation.create_code_post

    async def create_code_post(email: Union[str, None], phone_number: Union[str, None], api_options: APIOptions, user_context: Dict[str, Any],
                               ) -> Union[CreateCodePostOkResult, GeneralErrorResponse]:
        if (email is not None):
            existing_user = await get_user_by_email(email)
            if existing_user is None:
                # sign up attempt
                if (not (await is_email_allowed(email))):
                    return GeneralErrorResponse("Sign ups disabled. Please contact admin.")
        else:
            assert phone_number is not None
            existing_user = await get_user_by_phone_number(phone_number)
            if existing_user is None:
                # sign up attempt
                if (not (await is_phone_number_allowed(phone_number))):
                    return GeneralErrorResponse("Sign ups disabled. Please contact admin.")

        return await original_create_code_post(email, phone_number, api_options, user_context)

    original_implementation.create_code_post = create_code_post
    return original_implementation

init(
    app_info=InputAppInfo(
        api_domain="...", app_name="...", website_domain="..."),
    framework='...',  
    recipe_list=[
        passwordless.init(
   flow_type="USER_INPUT_CODE",
            override=passwordless.InputOverrideConfig(
                apis=override_passwordless_apis,
            ),
        )
    ]
)

createCodePOST is called when the user enters their email or phone number to login. We override it to check:

• If there exists a user with the input email or phone number, it means they are signing in and so we allow the operation.
• Otherwise, we check if the input email / phone number is allowed by calling our isEmailAllowed / isPhoneNumberAllowed function (which we implemented above). If not allowed, we return a message to the frontend.

We can add emails / phone numbers to the allow list by calling the addEmailToAllowlist / addPhoneNumberToAllowlist function we implemented above.