Home > Articles > Security > Network Security

  • Print
  • + Share This
This chapter is from the book

User Authentication and Access Privilege Management

Effectively managing the VPN users and their access privileges is the core consideration in any remote access VPN design. There are mainly two aspects:

  • A scalable and secure solution to authenticate users
  • Decisions on what access privilege to grant to the users based on various user and security attributes

Many organizations migrate from the existing IPsec-based remote access VPN solutions to SSL VPN, whereas other organizations simply add SSL VPNs to their existing remote access VPN. The good news is that SSL VPNs fit well into the existing authentication infrastructure.

User Authentication

Although this section focuses on user authentication, first step back to have a quick look at the big picture. AAA stands for authentication (which defines who you are), authorization (which defines what you are allowed to do), and accounting (which provides a record of what you did). User authentication is a key step in an SSL VPN solution. Aside from validating users' credentials, user authentication allows an SSL VPN gateway to assign the user to a policy group. The assignment is made by using a user's organization group information, which is derived during the authentication phase, along with other attributes, such as endpoint security posture and time of day. The policy group defines the authorization privileges of the users.

Choice of Authentication Servers

You have a wide variety of identity technologies to choose from for authenticating users. The common choices are passwords, RADIUS, TACACS+, one-time password (OTP) systems, public-key infrastructure (PKI), smart cards, and so on. For remote access VPN authentication, a two-factor OTP system provides the strongest security and manageability combination. It is also common for small- to medium-sized companies to leverage existing user directory infrastructure such as Lightweight Directory Access Protocol (LDAP), Windows NTLM, or Windows XP/2000 Active Directory for VPN user authentication. To use this, you need to apply and enforce strong password policies because the strength of the security relies on those policies.

The design of the AAA system can vary depending on the size of your network and the disparity of access methods. For an SSL VPN device, the choices of authentication servers fall mainly into two categories:

  • A dedicated AAA server running RADIUS: The AAA server is the interface between the SSL VPN appliance and the identity servers, such as corporate LDAP servers or OTP systems. Cisco Secure ACS is an example of this type of AAA server. The SSL VPN appliance communicates with the AAA server using the RADIUS protocol. Often, the AAA server sends a query to the external identity databases for identity authentication, and returns the authentication result to the SSL VPN appliance. The AAA server can speak different protocol languages with various identity databases such as LDAP, SecureID, and Windows Active Directory. An advanced AAA server, such as Cisco Secure ACS, can also retrieve additional user attributes from the external user identity servers, such as the users' roles in the organization or the users' password expiration information. All these user attributes can be used later in the authorization phase to determine the access privilege.
  • An SSL VPN appliance communicating directly with the identity server: In this case, the SSL VPN appliance needs to be able to communicate with various types of identity servers, such as LDAP, OTP systems, or Windows domain controllers. This becomes fairly common because most current SSL VPN vendors support multiple types of authentication servers. This mode is most common to small- to medium-sized companies that do not have disparate access methods, and hence have no need to have a central root AAA system.

When you choose to use this method, pay attention to what additional information the SSL VPN appliance can retrieve from the authentication servers, other than the results of the user authentication. For the later authorization phase, it is often useful for the SSL VPN appliance to also be able to get the users' organizational information. Enabling the SSL VPN appliance with this additional capability requires more integration between the SSL VPN appliance and the authentication server.

AAA Server Scalability and High Availability

The scalability and availability of the AAA server directly affect the availability of your VPN network and the user experience.

For a small- to medium-sized VPN network, it is relatively easy to address this design issue. Because the number of the VPN users is relatively small, the scalability of the AAA server is less of an issue. Also, because small to medium deployment normally does not have dispersed Internet VPN access, the AAA servers normally reside on a local network, and network delay and resiliency are not problematic. You should have a backup or secondary AAA server to provide local high availability. Most SSL VPN appliances support checking a secondary AAA server in case the primary server is not available.

For a medium to large enterprise network, the scalability and resiliency of the AAA systems are important and need to be carefully designed. For a remote access VPN deployment, you probably need to integrate your authentication requirements with the AAA infrastructure that is already in place to support other access methods.

Some good design guidelines for deploying a Cisco Secure Access Control Server (ACS) have been documented in the white paper "Guidelines for Placing ACS in the Network," which can be found at http://www.cisco.com/en/US/products/sw/secursw/ps2086/products_white_paper09186a0080092567.shtml. In this white paper, the general design recommendations documented for scalability, resiliency, and device placement should apply to most AAA server deployments.

The following sections briefly highlight the important factors that need to be considered.

AAA Server Scalability

When you consider AAA server scalability, keep the following points in mind:

  • The maximum number of users supported by the AAA server.
  • The number of authentication requests per second the AAA server can handle.
  • The type of database. For an internal user database on the AAA server itself, check its scalability to find out how many local users can be defined.

AAA Server High Availability and Resiliency

When you consider AAA server high availability (HA) and resiliency, keep the following points in mind:

  • Consider a local secondary AAA server.
  • For dispersed network access and VPN geographic HA design, consider placing a AAA server at each location that has business-critical impact.
  • Incorporate a robust AAA server database synchronization mechanism.

Resource Access Privilege Management

After user authentication, the remote access VPN device should be able to authorize the user with resource access privileges based on the user's attributes. As described earlier, because of the ubiquity of the SSL VPN, its design needs to ensure the integrity of the endpoint. Hence the resource authorization also goes beyond the standard user attributes to include other security attributes. The following is a list of attributes that can be used to determine resource access privilege:

  • Sign-in URL: For an SSL VPN device that offers different sign-in URLs to different groups of users, the sign-in URL can be used to decide the type of resource this group of users is entitled to.
  • User's digital certificate: The organization information in the user's certificates can be used to map users to corresponding roles that allow different resource access.
  • The result of endpoint security assessment: This point is discussed in more detail within the context of the security considerations. In essence, the posture of the endpoint can be used as a dynamic factor to decide users' access privilege to sensitive corporate resources.
  • Time of day.
  • Browser types.
  • User attributes: These are the typical user attributes in the user identity database. For example, the marketing group in the LDAP database can be mapped to an internal marketing group in the SSL VPN.

Some of these attributes, such as endpoint security posture and users' IP addresses, are collected prior to user authentication. Some of the attributes, such as endpoint security posture, should be periodically reevaluated during the user session to dynamically determine the user's access privileges based on the most current situation.

To clarify these concepts, we give an example of how an SSL VPN system can use some of these attributes to perform dynamic access privilege management. In this case study, a salesperson attempts to access corporate resources using an SSL VPN. Depending on the result of the endpoint assessment, the salesperson is granted different levels of resource access.

Scenario 1: Salesperson Accesses the VPN from a Kiosk Computer at a Sales Conference
  • Step 1 The salesperson initiates the VPN request by entering https://vpn.companyxyz.com into the browser.
  • Step 2 Upon receiving the access request, the SSL VPN appliance collects some user attributes and performs the endpoint security checking. The results are as follows:
    • IP address = Outside
    • Client digital certificate = Not present
    • Proper antivirus client installed and enabled = No
  • Step 3 Based on the results in Step 2, the SSL VPN chooses an authentication method for the user and performs user authentication:
    • Authentication method = Strong, OTP
  • Step 4 After successful user authentication, the SSL VPN appliance also retrieves the user's organization information through a separate authorization step:
    • User's organization group = Sales
  • Step 5 Based on the user attributes so far, the SSL VPN appliance maps the user to a VPN group or role:
    • VPN role = sales_insecure
  • Step 6 The sales_insecure role decides the user access privilege:
    • User privilege = Web access only
    • Session timeout = 30 minutes
    • Periodic security checking = Yes
    • Require secure desktop = Yes
    • Note: The secure desktop can be launched much earlier at the preauthentication phase based on the IP address attribute. This way, the user password entered into the client browser can be protected from software such as keystroke loggers.
  • Step 7 The salesperson logs in and starts to access the bookmarked web applications, such as OWA. More granular application-level access control can be applied at this phase.
Scenario 2: The Same Salesperson Accesses the VPN from a Corporate-Owned Laptop at Home
  • Step 1 The salesperson initiates the VPN request by entering https://vpn.companyxyz.com into the browser.
  • Step 2 Upon receiving the access request, the SSL VPN appliance collects some user attributes and performs the endpoint security checking. The results are as follows:
    • IP address = Outside
    • Client digital certificate = Yes
    • Proper antivirus client installed and enabled = Yes
  • Step 3 Based on the results in Step 2, the SSL VPN chooses an authentication method for the user and performs user authentication:
    • Authentication method = Strong, OTP
  • Step 4 After successful user authentication, the SSL VPN appliance also retrieves the user's organization information through a separate authorization step:
    • User's organization group = Sales
  • Step 5 Based on the user attributes so far, the SSL VPN maps the user to a VPN group or role:
    • VPN role = sales_secure
  • Step 6 The sales_secure role decides the user access privilege:
    • User privilege = Tunnel client
    • Session timeout = 12 hours
    • Periodic security checking = Yes
    • Require secure desktop = No
  • Step 7 The salesperson logs in and starts to access the corporate network using the tunnel client mode. Additional granular IP-based access control can be applied at this phase.
  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020