Mechanism to disable iteration of all IP's reported for the FQDN in Scanner modules

[cdelafuente-r7]

Summary

When a FQDN translates to multiple IP's, which usually happens with load-balanced endpoints, Scanner framework iterates on every IP's by default (run_host is called multiple times with each IP). This is usually fine when we want to run the module against each host. But, in some specific context, this can be an issue. For example, when enumerating username from a public endpoint like Azure, AWS, etc. repeating the operation for every host reported by a specific FQDN is not necessary and should be avoided.

A good example is the Azure AD scanner module, which query the Azure AD SSO autologon endpoint (autologon.microsoftazuread-sso.com). At the moment, it is not possible to implement this using the official Login Scanner template, since run_host would be called multiple times for each IP reported by this FQDN.

Basic example

A possible solution would be to have a special option that instructs the Scanner to only pick one IP from a single FQDN in RHOSTS.

Another option would be to force the use of RHOST when RHOSTS is empty. The Scanner could first check for RHOSTS and, if it is not there, look for RHOST value, knowing that only one IP should be used when a FQDN is provided.

Motivation

This will enable contributors to write Login Scanner modules against SaaS services, which are often behind a load balancer, using the official Scanner template.