AzureAD supports the OAuth Resource Owner Password Credential Grant.
The ADAL SDK has recently added support for it (https://www.nuget.org/packages/Microsoft.IdentityModel.Clients.ActiveDirectory/2.8.10804.1442-rc)
Here the link for UserCredentials on ADAL .net library : https://github.com/AzureAD/azure-activedirectory-library-for-dotnet/blob/master/src/ADAL.NET/UserCredential.cs
do we support Authentication via user credentials in the adal4j (adal java) library ??