Internal domain enumeration

Identification of a targets internal domain name using public facing web applications that support NTLM SSP authentication, such as Exchange.

NTLM SSP challenge response decoding for internal domain

Knowing the internal domain name of a target can be highly useful for a range of activities including finding similar public domain names, designing phishing lures or keying malware to ensure it only runs in the target environment.

Web applications

Web applications that support NTLM authentication can be leveraged to access this information very easily. Fortunately, a very common web application supports NTLM authentication, Exchange servers.

Two URLs that Exchange servers support for NTLM authentication are shown below. This authentication type is not exclusive to exchange, and this internal domain information disclosure is possible on any applications that support it.

https://[host]/EWS
https://autodiscover.[host]/autodiscover/autodiscover.xml

By initiating an NTLM authentication request with null credentials the server will respond with an NTLM challenge response. This is encoded with a known key and can be decoded enumerate NetBIOS name, DNS, and OS build version information.

In many cases web applications that do not offer NTLM SSO authentication during normal usage will respond with a NTLM challenge response if a GET request is made including the Authorization header with null credential values.

Authorization: NTLM TlRMTVNTUAABAAAAB4IIAAAAAAAAAAAAAAAAAAAAAAA=

This can be automated using the nmap script http-ntlm-info.nse

nmap -p 443 --script http-ntlm-info [host]

Other services

NTLM SSO is supported by a wide array of other services.

The nmap script discussed above (http-ntlm-info.nse) has alternatives for a number of other protocols.

These include SMTP, IMAP, POP3, MS-SQL, TELNET, NNTP, and RDP (eg rdp-ntlm-info.nse). To use all of these scripts:

nmap --script=*-ntlm-info --script-timeout=60s [host]

Tools:

This is included the nmap default script repository.

nmap -p 443 --script http-ntlm-info [host]

PORT    STATE SERVICE
443/tcp open  https
| http-ntlm-info:
|   Target_Name: DOMAIN
|   NetBIOS_Domain_Name:  DOMAIN
|   NetBIOS_Computer_Name: Hostname
|   DNS_Domain_Name: Domain.Parent_Domainl
|   DNS_Computer_Name: Hostname.Domain.Parent_Domain
|   DNS_Tree_Name: Parent_Domain
|_  Product_Version: 10.0.14393

By default the script includes the Authorization header with null credentials in its request to the web server; where the NTLM authentication is not accessable at the root of the web applciation, specify the path using the script argument "http-ntlm-info.root".

Examples for the two Exchange server paths above:

nmap -p 443 --script http-ntlm-info --script-args http-ntlm-info.root=/EWS [host]
nmap -p 443 --script http-ntlm-info --script-args http-ntlm-info.root=/autodiscover/autodiscover.xml autodiscover.[host]

Resources

PreviousO365 Tenant ID NextO365 email enumeration

Last updated 4 years ago

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