NTLM authentication

  • Release version: Yokohama
  • Updated January 30, 2025
  • 2 minutes to read
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    Summary of NTLM authentication

    NTLM authentication is a proprietary Microsoft protocol supported by basic web servers like HttpClient. It is more secure than Digest authentication after updates to Windows NT 4. NTLM requires specific credential handling and differs from basic and digest authentication in key ways, particularly in how it authenticates connections rather than individual requests.

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    Key Features

    • NTLM uses NTCredentials instead of standard username-password credentials, with the username provided without a domain prefix.
    • The realm for NTLM is the domain name of the server being connected to, which can be problematic if the server has multiple domains. Using a null realm during testing is recommended.
    • Authentication occurs per connection, requiring connections to remain open during authentication. This necessitates HTTP keep-alives and limits NTLM use with proxy servers or HTTP 1.0 connections.

    Configuration for ServiceNow Customers

    To enable NTLM authentication for proxy servers in ServiceNow, set the following system properties in the sysproperties table:

    • glide.http.proxyntusername: Username for proxy NTLM authentication
    • glide.http.proxyntpassword: Password for proxy NTLM authentication
    • glide.http.proxynthost: Hostname of the proxy server
    • glide.http.proxyntdomain: Domain for the proxy server

    These properties enable ServiceNow instances to authenticate through NTLM-enabled proxy servers securely and effectively.

    NTLM is the most complex of the authentication protocols supported by a basic web server.

    NTLM is the most complex of the authentication protocols supported by a basic web server such as HttpClient. It is a proprietary protocol designed by Microsoft with no publicly available specification. Early versions of NTLM were less secure than Digest authentication due to faults in the design. However, these were fixed in a service pack for Windows NT 4 and the protocol is now considered more secure than Digest authentication.

    NTLM authentication requires that an instance of NTCredentials be available for the domain name of the server or the default credentials. Since NTLM does not use the notion of realms, HttpClient uses the domain name of the server as the name of the realm. Also, the username provided to the NTCredentials should not be prefixed with the domain:
    • Correct: adrian
    • Incorrect: DOMAIN\adrian
    There are some significant differences in the way NTLM works compared with basic and digest authentication. These differences are generally handled by HttpClient. However, having an understanding of these differences can help you avoid problems when using NTLM authentication.
    • NTLM authentication works almost exactly the same as any other form of authentication in terms of the HttpClient API. The only difference is that you need to supply NTCredentials instead of UsernamePasswordCredentials (NTCredentials actually extends UsernamePasswordCredentials so you can use NTCredentials right throughout your application, if needed).
    • The realm for NTLM authentication is the domain name of the computer being connected. This can be troublesome because servers often have multiple domain names. Only the domain name that HttpClient connects to, as specified by the HostConfiguration, is used to look up the credentials. While initially testing NTLM authentication, it is best to pass the realm in as null, which is used as the default.
    • NTLM authenticates a connection and not a request. So you need to authenticate every time a new connection is made and keeping the connection open during authentication is vital. For this reason, NTLM cannot be used to authenticate with both a proxy server and the web server, nor can NTLM be used with HTTP 1.0 connections or web servers that do not support HTTP keep-alives.
    Note:
    Set these properties from the System Properties [sys_properties] table.
    Table 1. NTLM authentication
    Property Description Examples
    glide.http.proxy_ntusername Specify the username used to authenticate the proxy server with NTLM authentication.
    • Type: string
    • Default value: none
    		 username
    glide.http.proxy_ntpassword Specify the password used to authenticate the proxy server with NTLM authentication.
    • Type: string
    • Default value: none
    		 password
    glide.http.proxy_nthost Specify the hostname used to authenticate the proxy server with NTLM authentication.
    • Type: string
    • Default value: none
    		 nthost
    glide.http.proxy_ntdomain Specify the domain used to authenticate the proxy server with NTLM authentication.
    • Type: string
    • Default value: none
    		 DOMAIN