Home > Articles > Programming > Windows Programming

This chapter is from the book

This chapter is from the book

Networked Computing with the .NET Framework

Chapter 1, "Common Security Problems on the Internet," discussed several problems surrounding networked computing:

  • Insecure default configurations

  • Buffer overflows

  • Canonicalization errors

  • Information leaks

  • Denial-of-service vulnerabilities

As we saw in Chapter 2, the .NET Framework has many interesting features for developers, administrators, and users. Those features can help solve some of these security problems. The following sections will look at how these problems are addressed.

Insecure Default Configurations

There are numerous settings that you can tweak in the .NET Framework to affect execution behavior. Among these are some key settings that help prevent security problems from arising in .NET applications. Those settings include the following:

  • Default security policy (covered in detail in Chapter 8)—The .NET Framework has a set of security policies that dictate what different applications are trusted to do. For instance, code downloaded from the local intranet is not allowed to directly read or write to arbitrary locations in the file system. However, it is allowed to use a File Open dialog that allows users to pick specific files an application can read.

  • The default security policy was carefully constructed to ensure that code originating from places other than the user's computer is constrained to a safe subset of functionality. Simply installing the .NET Framework on a machine should not open up the possibility of untrusted managed code performing arbitrary actions.

  • ASP.NET user account (covered in detail in Chapter 13, "Introduction to ASP.NET Security")—Unlike current IIS installations, the ASP.NET worker process is not run under the SYSTEM account by default. Instead, it is run under an account with limited privileges. This is a good defense-in-depth practice that will help mitigate accidental misconfigurations of servers or bugs that may be found in the ASP.NET code in the future.

  • The ASP.NET process can be configured to use the SYSTEM account if necessary. However, basic ASP.NET pages shouldn't need special privileges, so an account with limited privileges is fine.

Buffer Overflows

Fortunately, buffer overflows are much less of a problem when dealing with a managed application. String and array copying have tight bounds checking in the .NET Framework class libraries. This alone should help decrease the number of serious security holes in applications.

Note that managed applications do not completely eliminate buffer overflows. This is primarily because all managed applications run unmanaged code at some level. The .NET Framework core unmanaged code has been closely inspected for buffer overflows, so few should remain there. However, if a managed application uses the interoperability functionality to access classic COM objects or platform APIs, the unmanaged code will execute. Thus, if a managed application uses unmanaged components or API calls, buffer overflows are still possible. In these cases, careful code reviews are necessary to mitigate the risk of buffer overflows.

Using "unsafe" C# functionality or manually constructed IL can lead to unverifiable managed applications. Unverifiable applications can also have buffer overflow problems because their behavior has considerably fewer execution guarantees. However, nearly all managed code you write should be verifiable, so managed buffer overflows should be very rare.

Canonicalization Errors

Canonicalization errors are probably as easy to create in managed code as they are in unmanaged code. This is because they cannot be broadly fixed in applications by changing underlying .NET Framework behavior. They are bugs specific to each application. For instance, if some application is supposed to parse a string for specific commands to execute, the key to correctness is proper parsing logic. Bad logic will cause problems in managed and unmanaged applications.

There are some tools from the .NET Framework class library that can help prevent canonicalization errors. The System.Text.RegularExpressions namespace has classes to deal with regular expressions, which are very helpful when dealing with arbitrary strings. The System.Uri class provides a mechanism to canonicalize URIs. The System.IO.Path class can provide an absolute file path for any given relative file path.

Information Leaks

This is another area where the .NET Framework cannot solve an entire class of problems. Software deals with information from different sources, and determining what information can be safely shared is a complicated process. Some data, such as passwords and credit card numbers, is usually understood to be sensitive information that should not be freely handed out. Other information, such as machine names, usernames, and network topology data, isn't as widely known to be data that should be protected.

Some managed code has explicit checks to ensure that information isn't leaked. For instance, file paths (which can include usernames), private class information in assemblies, and network topology information from DNS queries are all protected by the .NET Framework when directly accessed using the .NET Framework class library. However, this information can all be accidentally handed out by a poorly written .NET component. Thus, it is really up to application writers to ensure that their applications don't cause these sorts of problems.

Denial-of-Service Vulnerabilities

Version 1 of the .NET Framework doesn't focus on fixing denial-of-service issues. Thus, it should be expected that untrusted managed code can cause .NET Framework hosts to stop responding. If you intend to use the .NET Framework in semitrusted environments such as Web-hosted applications, you will have to take care to accommodate faulty or malicious code. For example, a managed code host might want to only allow user applications to execute for a short amount of time before they are automatically killed.

Note that denial-of-service attacks should not be able to cause arbitrary code execution or information leaks. Instead, the effects should be temporary until the offending code is stopped or the host is restarted.

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