O365 Tenant ID

Enumerate tenant ID from domain name

curl https://login.microsoftonline.com/[domain]/.well-known/openid-configuration

Tenant ID to domain name

Get part of tenant domain name - doesn't recover full domain

https://login.microsoftonline.com/[tenantID]/oauth2/devicecode?client_id=x

Determine if a machine is joined to AzureAd

HKLM:/SYSTEM/CurrentControlSet/Control/CloudDomainJoin/JoinInfo/{Guid}

Underneath the key, the following keys can be found: – TenantId – UserEmail

Determine if a user is joined to an AzureAd Domain

HKCU:/SOFTWARE/Microsoft/Windows NT/CurrentVersion/WorkplaceJoin/AADNGC/{Guid}

Underneath the key, the following keys can be found: – TenantDomain – UserId