Azure AD App Registration settings for UIPath - azure-active-directory

Question

we are using UIPath within our company for RPA. We tried setting up UIpath to send mail on behalf of other users. We followed this guide: https://docs.uipath.com/marketplace/docs/microsoft-office-365-setup
There are 2 odd things to this setup:
We HAVE to make the App Registration a "Public Client" in Azure. To my knowledge, normally this applies to frontend web applications where the app secret cannot be kept hidden. This is a backend process, so I think there is no reason of having to use a public client. Am I right in this statement? What are the downsides of having a public client? Anyone possessing the client_id can impersonate this app registration? (can act as this app registration and ask users for credentials and get a token on behalf of this app?)
I added some api permissions to the App Registration like mail.read, mail.send, etc. It stated that no "Admin consent required", but it didnt work. After I pressed the "admin consent" button it said that it granted those permissions and the configuration seemed to work. What does this ADMIN CONSENT button do? If I add permissions to an App Registration, do I always have to press admin consent?
Some extra clarification about the public credentials:
-I register an application called App-X, which is set to public.
-Normally, without a public client, when I request a token, I need both the client_id and the client_secret. By using the client_secret, microsoft knows that I am indeed really the application App-X who is requesting this token on behalf of the user.
-Without using client_secret, anyone who knows the client_id, can request consent from a user and say "I am App-X and I am asking for permissions", while in fact they are not App-X (just some random someone who finds the client_id). After the user consented, because "he knows App-X and he trusts it", then the malicious user/app can also request a token from microsoft because he only needs a client_id.

Answer 1

1.This is a backend process, so I think there is no reason of having to
use a public client. Am I right in this statement? What are the
downsides of having a public client? Anyone possessing the client_id
can impersonate this app registration? (can act as this app
registration and ask users for credentials and get a token on behalf
of this app?)
It depends on your application type. "Public client" is usually used to configure mobile and desktop client applications. Since UIPath is a mobile application that monitors the RPA environment, for your application registration, you need to choose to use "Public Client" registration.
If you don’t want your application to be used by users of other organizations, you don’t need to register the application as a multi-tenant application when you register your application. If your application needs to be used by multiple organizations, you need to register the application as Multi-tenant application. In this case, in theory, all tenants can use this application. However, you can verify which tenant the logged-in user comes from when logging in, and you can prevent tenants that you do not want to log in from logging in. Please see:here.
2.What does this ADMIN CONSENT button do? If I add permissions to an App Registration, do I always have to press admin consent?
Each application registers permissions it requires. Some permissions can be granted by users, some other only by the administrator.
Let's suppose you have only permissions that can be consented by users. The first time they use the application, they'll be prompted (each user) to consent those permissions to the application. If in the same scenario you click on grant admin consent, it is the equivalent of accepting it for all users on the tenant.
Now let's suppose the application registers permissions that require admin consent, you have no choice but to click that button if you want the application to work and be able to request tokens.
For those permissions that require the administrator’s consent, you You can go to Azure portal>App registrations>API permissions>Admin consent required to view .