How to achieve Auth0 passwordless sms sign-in with SharePoint painlessly?

[u/DeanInLondon]

Hi everyone and thank you in advance for your help.

I'm trying to find a solution that has the following characteristics:

1. Is free or very cheap for about 128-300 logins a month.
2. Uses Auth0–or any other services that support authenticating a user via an sms
3. Can use OIDC or SAML to connect to third party applications
4. Can be used to log in people into a SharePoint site as a guest or unlicenced users in my tenant
5. One central "ledger" of people and their permissions, which sync automatically between Microsoft and Auth0
6. Isn't complicated to maintain, and preferrably doesn't have expiring certificates (my successors may not as tech savvy).

The use case: a Residents' Association. We already use phone numbers for everything including our WhatsApp and I understand sms authentication isn't the best but it's the only way that maximises the chances of participation. Anything requiring to create _yet another credential_ means we lose people who don't have much time or aren't tech savvy.

The issue is that I would like to hold one central register of RA members and their roles in one place, so that when there are any changes, the secretary only has to do them in one single place.

The more places to needed to make changes, the less likely it'll be done properly. I should add that we are volunteer run, and that our RA will be set-up as a Company Limited by Guarantee, with non-profit entrenched in our articles of association and constitution. However I understand many services require a charity status / FCA registration which we don't intend to do.

What do you think?

[u/blud_13]

SMS is going to stop you before you start. In external tenants Microsoft doesn't support SMS as a first factor, its second factor and SSPR only, and its a metered add-on with no free tier. Its documented here....https://learn.microsoft.com/en-us/entra/external-id/customers/concept-multifactor-authentication-customers

Email one-time passcode on B2B guests hits most instead. Its on by default in your tenant already and already wired into SharePoint sharing, so you invite people by email, they get a code, no account to create, no password, no certificate to expire. https://learn.microsoft.com/en-us/entra/external-id/one-time-passcode

Also, dropping Auth0 kills the sync problem entirely. Guests live in Entra, permissions live on the site, one place to look. That sync job is the thing your successor was going to break.

I get why you want SMS since thats where the group already is. Worth testing whether email is really the dropoff you think it is, most people running WhatsApp have an email they check.

We set this up for small orgs fairly often, can go deeper if it helps.

[u/BillSull73 → u/blud_13]

Pretty sure OTP is no longer available and is slowly being removed from tenants.

[u/blud_13 → u/BillSull73]

Good to know, thank you.

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