IE Pinning - Documentation

What is IE Pinning?

IE Pinning, or Internet Explorer Pinning, refers to the now-obsolete technique of configuring Internet Explorer (IE) to exclusively use a specific, pre-approved certificate for authentication within a given context. This involved “pinning” the expected certificate’s public key to the application. Subsequent connections would only be accepted if the presented certificate matched the pinned key. This provided an extra layer of security against man-in-the-middle (MITM) attacks where a malicious actor intercepts communication and presents a forged certificate. Note that this refers to the application level pinning, not the browser’s built-in certificate pinning features.

Why Use IE Pinning?

IE Pinning was primarily employed to enhance the security of applications relying on HTTPS connections, especially those handling sensitive data. By limiting the accepted certificates to a single, trusted key, the risk of accepting fraudulent certificates during a MITM attack was significantly reduced. This was particularly crucial in environments with high security requirements or where the risk of such attacks was deemed elevated.

Benefits and Drawbacks

Benefits:

Enhanced Security: Provides a strong defense against MITM attacks using fraudulent certificates.
Improved Trust: Increased confidence that communication is with the intended server.

Drawbacks:

Certificate Management Overhead: Managing and updating pinned certificates requires careful planning and coordination. Re-pinning after certificate renewal or revocation is crucial and complex. A misconfiguration can render the application unusable.
Lack of Flexibility: Pinning restricts flexibility. It becomes difficult to handle unexpected certificate changes (e.g., emergency certificate updates).
Deprecation: IE and its pinning functionality are outdated and no longer supported. Modern browsers offer more robust and flexible security mechanisms.
Limited Browser Support: This technique is specifically tied to the now-obsolete Internet Explorer and won’t work with modern browsers.

Alternatives to IE Pinning

Given the deprecation of IE and its pinning mechanism, modern alternatives should be used. These include:

Public Key Pinning (HPKP): A more robust and standardized approach that uses HTTP headers to specify the expected public keys. Though technically deprecated now, it was a significant improvement over IE pinning.
Certificate Authority (CA) Validation with Strict Validation Policies: Ensure that the application strictly validates certificates against trusted CAs, utilizing the latest revocation checking mechanisms.
Modern Browser Security Features: Leverage advanced features in current browsers such as HSTS (HTTP Strict Transport Security) and certificate transparency logs. These methods are preferred for current web application development.
Application-Level Certificate Verification with Modern Cryptographic Libraries: Instead of relying on browser pinning, implement robust certificate verification directly within the application using up-to-date cryptography libraries, offering granular control and better maintainability.

Implementing IE Pinning in Javascript

Note: IE and its associated pinning mechanisms are deprecated and no longer supported. The information below is provided for archival purposes only and should not be used for new development. Modern security practices should be employed instead.

Understanding the `ms-enable-pinned-sites` meta tag

The <meta name="ms-enable-pinned-sites" content="true"> tag within the <head> section of an HTML page informed Internet Explorer that the site supported pinning. It was a prerequisite for using the pinning mechanism. However, this alone didn’t implement the pinning; it only signaled that the site was capable of being pinned. The actual pinning logic relied on other methods, typically involving the msApplication-config XML file and potentially some Javascript.

Using the `msApplication-config` XML file

The msApplication-config XML file provided a configuration for Internet Explorer’s interaction with the website. This file, ideally located at the root of the website, could specify which certificates should be pinned to the site. However, the exact method of specifying the certificates within the XML file was not standardized, and relied on proprietary extensions. Implementation details varied based on the specific application and its deployment method. This method primarily targeted the application itself, not the browser’s settings.

Javascript code for Pinning

Javascript’s role in IE Pinning was minimal for pinning itself. It wouldn’t directly pin certificates. Instead, Javascript might have been used for:

Checking for Pinned Certificates: After a successful connection, Javascript could have verified that the certificate presented matched the expected pinned certificate. This verification usually involved parsing certificate details and comparing them against the pinned certificate data (fetched from the msApplication-config file or a similar source).
Handling Pinning Errors: Javascript was essential to handle scenarios where the certificate didn’t match the pinned certificate (e.g., displaying an error message to the user).

Illustrative (and outdated) Javascript snippet (This code is not functional in modern browsers):

// This is a highly simplified and illustrative example only.  Actual implementation varied greatly.
function checkPinnedCertificate(certificateData) {
  // In a real implementation, this would fetch and compare against the pinned certificate data.
  const pinnedCertificate = { subject: "example.com", ... }; // Placeholder
  if (certificateData.subject === pinnedCertificate.subject) {
    // Certificate matches, proceed.
    return true;
  } else {
    // Certificate mismatch, handle the error.
    alert("Certificate mismatch!");
    return false;
  }
}

Handling Pinning Events

Pinning events themselves weren’t directly exposed through a standardized Javascript API. Instead, the developer would have had to handle potential errors, such as certificate mismatches, using Javascript error handling techniques, often in conjunction with HTTP status codes returned by the server.

Troubleshooting Common Issues

Common problems with IE Pinning (now largely irrelevant due to IE’s obsolescence):

Certificate Mismatch: The most frequent issue was a mismatch between the presented certificate and the pinned certificate. This typically occurred when certificates were updated or if there was a problem with the certificate chain.
Configuration Errors: Incorrect configuration of the msApplication-config file or improper implementation of the pinning logic would render pinning ineffective.
Deployment Issues: Problems during deployment could have led to the application failing to correctly read or use the pinned certificate information.

Again, it’s crucial to reiterate that IE and its pinning mechanism are deprecated. Modern security practices and standards should be employed instead for secure web application development. The above information serves only as historical context.

Advanced Techniques

Note: IE and its pinning functionality are deprecated and no longer supported. The information below is for archival purposes only and should not be used for new development. Modern security and development practices should be followed.

Customizing the Pinned Site Tile

When a site was pinned to the IE taskbar, it displayed a tile representing the site. Customizing this tile involved using specific metadata within the website’s code, typically within the HTML <head> section or a related configuration file. While the exact methods were not standardized across all versions of IE, it often involved manipulating meta tags or using specialized XML files (similar to the msApplication-config file discussed previously) to specify the tile’s icon and name. The specific tags and attributes used were not consistently documented and varied based on IE version.

Handling Different Screen Sizes and Resolutions

Pinning itself didn’t directly address screen sizes. The appearance of the pinned tile would adapt to the available space on the taskbar, similar to other pinned applications. However, the website content displayed after the user clicked the tile would need to be responsive to handle different screen sizes and resolutions, a common practice for web development using CSS media queries and flexible layouts. This aspect is unrelated to the pinning mechanism itself.

Integration with other Javascript Frameworks

IE Pinning, as a browser-centric security feature, had minimal interaction with Javascript frameworks. The core pinning logic was not framework-dependent. However, Javascript frameworks could have been used to perform tasks related to:

Checking for Pinned Status: Using Javascript, a site could check if it was pinned using browser detection (and IE-specific methods) to tailor the user interface accordingly. This is a browser feature detection issue and not related to pinning itself.
Handling Pinning Errors: Javascript frameworks could simplify the display of error messages in the event of certificate mismatch or other pinning problems.
Asynchronous Operations: Frameworks might have been used to improve the user experience by asynchronously handling the certificate verification process.

Note that these were ancillary uses; the actual pinning process didn’t integrate directly with the framework.

Testing and Debugging Pinning Functionality

Testing and debugging IE Pinning involved a combination of:

Checking the msApplication-config File: Verifying the correctness of the XML file, including the certificates specified and other configuration parameters.
Network Monitoring Tools: Using tools like Fiddler or similar network sniffers to inspect the SSL/TLS handshake to see if the correct certificate was being presented and accepted. The developer would have needed to inspect the certificate details to ensure they matched the pinned certificate.
Javascript Debugging: Using a browser’s developer tools to debug any custom Javascript code associated with handling pinning errors or certificate verification.
Testing Across Different IE Versions: Since IE’s behavior could vary, testing the pinning functionality across multiple IE versions was crucial.

Again, it must be emphasized that these techniques are relevant only for the now-obsolete IE pinning and should not be used for current web development. Modern security and development approaches provide superior alternatives and should be adopted.

Security Considerations

Note: IE and its pinning mechanism are deprecated and no longer supported. The information below is for archival purposes only and should not be used for new development. Modern security practices should be employed.

Protecting Against Malicious Pinning

Malicious actors could potentially attempt to exploit IE Pinning in several ways:

Compromising the msApplication-config File: If a malicious actor gains access to a website’s server and modifies the msApplication-config file to include a fraudulent certificate, they could perform a MITM attack, even with pinning enabled.
Man-in-the-Middle Attacks (MITM) Before Pinning: An attacker could intercept the initial connection before the pinning process is established and present a fraudulent certificate. The pinning would then be based on the compromised certificate.
Exploiting Vulnerabilities in the Pinning Implementation: Bugs in the custom code used to verify the pinned certificate could be exploited to bypass pinning.

Strong server-side security measures and secure coding practices were essential to mitigate these risks. Regular security audits were crucial to identify and patch vulnerabilities.

Ensuring User Privacy

While IE Pinning enhanced security, it could indirectly impact user privacy if not implemented carefully. The pinning process itself didn’t directly collect user data. However, the application using pinning might collect user data during its operation. Any data collection must comply with relevant privacy regulations and user consent should be obtained whenever appropriate. The security mechanisms employed should not be used to compromise user privacy.

Best Practices for Secure Pinning Implementation

Given that IE Pinning is obsolete, these best practices are largely historical. However, the underlying principles remain relevant in the context of modern security practices:

Secure Certificate Management: Use strong key generation and storage practices for pinned certificates.
Regular Certificate Updates: Update pinned certificates regularly, ideally using automated processes, to address vulnerabilities or certificate expiration.
Secure Coding Practices: Employ secure coding techniques to prevent vulnerabilities in custom code used for certificate verification.
Robust Error Handling: Implement robust error handling to gracefully manage certificate mismatches and other potential issues without revealing sensitive information.
Regular Security Audits: Regularly audit the system for vulnerabilities and weaknesses, both in the server-side code and the client-side code related to pinning.
Centralized Certificate Management: A centralized system for managing pinned certificates can improve organization and reduce the chance of error.
Minimize reliance: Rely on other robust and supported security mechanisms instead of solely relying on outdated pinning solutions.

Because IE Pinning is deprecated, these practices should be considered in the context of modern security mechanisms like HSTS, certificate transparency, and robust application-level certificate validation with current cryptographic libraries. These provide more robust and supported methods for securing web applications.

Deployment and Maintenance

Deploying the Pinned Site

Deploying a site that utilized IE Pinning involved several steps:

Configuration: Setting up the server with the correct SSL/TLS certificates and ensuring the certificates were properly configured for the application.
msApplication-config Deployment: Deploying the msApplication-config XML file to the root of the website, containing the necessary pinning information.
Website Deployment: Deploying the website’s HTML, Javascript, and other files.
Testing: Thoroughly testing the site to ensure the pinning worked correctly across different IE versions.

The deployment process needed to be carefully managed to avoid errors and ensure the correct certificates were used. Any mistakes could render the site inaccessible to users.

Updating the Pinned Site

Updating a pinned site presented significant challenges. Changes to the pinned certificate required careful planning and coordination to avoid disruption. The process typically involved:

Certificate Renewal/Update: Generating and obtaining a new certificate, if necessary.
Updating msApplication-config: Modifying the msApplication-config file to reflect the new certificate’s public key.
Deployment: Deploying the updated msApplication-config file and other website files.
User Communication: Clearly communicating to users the timing of the update and any potential downtime.
Monitoring: Carefully monitoring the site after the update to ensure everything functions as expected.

The update process required meticulous attention to detail. A failure to properly update the pinned certificate could render the site inaccessible to users.

Monitoring Pinned Site Performance

Monitoring the performance of a pinned site involved standard web performance monitoring tools, but with a particular focus on the security aspects related to pinning:

Certificate Validation Errors: Tracking any certificate validation errors to promptly identify and address issues.
User Feedback: Gathering user feedback to identify problems or difficulties accessing the site (potentially indicative of pinning problems).
Server Logs: Examining server logs for errors or unusual activity related to SSL/TLS handshakes or certificate validation.

Continuous monitoring was crucial to identify and resolve problems before they impacted a significant number of users.

Managing User Feedback

User feedback was particularly important when dealing with a pinned site. Problems with pinning could lead to users being unable to access the site, resulting in frustrated users. A system for collecting and responding to user feedback was essential:

Feedback Channels: Providing multiple channels for users to report problems (e.g., email, support tickets, feedback forms).
Prompt Responses: Responding promptly to user reports to address issues quickly.
User Education: If necessary, educating users about the purpose of pinning and how to resolve common issues.

Effective communication and timely responses to user feedback were crucial for maintaining user satisfaction and the reputation of the site.

Again, it is crucial to remember that IE and its pinning mechanisms are obsolete. Modern security and web development best practices must be implemented for any new projects. The information above is solely for historical reference.

Appendix

Glossary of Terms

IE Pinning: A now-obsolete technique in Internet Explorer to restrict authentication to a specific, pre-approved certificate.
Certificate Pinning: The general practice of associating a specific certificate (or its public key) with an application or website to prevent man-in-the-middle attacks.
msApplication-config: An XML file (now obsolete) used in Internet Explorer to configure various aspects of a website, including potentially pinning information.
ms-enable-pinned-sites: A meta tag (now obsolete) that indicated to Internet Explorer that a site supported pinning.
Man-in-the-Middle (MITM) Attack: An attack where a malicious actor intercepts communication between two parties.
SSL/TLS Handshake: The process of establishing a secure connection between a client and a server using SSL or TLS.
Certificate Authority (CA): An entity that issues and manages digital certificates.

Useful Resources

(Note: Many resources related to IE Pinning are outdated and may not be reliable. Refer to modern security documentation instead.) There were no widely available standardized resources for IE Pinning. Information was often scattered across various blog posts, forums, and less formal documentation.

Example Code Snippets

(Note: The following examples are highly simplified and illustrative only and will not function in modern browsers. They are for historical context only.)

Illustrative (and non-functional) Javascript snippet (for checking a certificate, not for actual pinning):

// This is a highly simplified and illustrative example only.  Actual implementation varied greatly.
function checkPinnedCertificate(certificateData) {
  // In a real implementation, this would fetch and compare against the pinned certificate data.
  const pinnedCertificate = { subject: "example.com", ... }; // Placeholder
  if (certificateData.subject === pinnedCertificate.subject) {
    // Certificate matches, proceed.
    return true;
  } else {
    // Certificate mismatch, handle the error.
    alert("Certificate mismatch!");
    return false;
  }
}

Illustrative (and non-functional) msApplication-config snippet:

<!-- This is a highly simplified and illustrative example only. Actual implementation varied greatly. -->
<?xml version="1.0" encoding="UTF-8"?>
<Application xmlns="http://schemas.microsoft.com/SMI/2005/Devices">
  <Certificates>
    <!--  In a real implementation, certificate details would be specified here.  The format was not standardized.-->
  </Certificates>
</Application>

Frequently Asked Questions (FAQs)

(Note: Many FAQs related to IE Pinning are now irrelevant due to IE’s obsolescence.)

Q: How do I pin a certificate to my website using IE Pinning? A: (Obsolete) This involved using the msApplication-config XML file and potentially custom Javascript, but the exact implementation details varied greatly and depended on the specific application and context. This method is no longer supported. Use modern, supported security techniques instead.
Q: What happens if the pinned certificate expires? A: (Obsolete) The website would likely become inaccessible to users unless the pinned certificate was updated in a timely fashion. Modern solutions use more robust mechanisms for certificate renewal.
Q: What are the alternatives to IE Pinning? A: Modern alternatives include HPKP (although deprecated), HSTS, certificate transparency logs, and robust application-level certificate verification using current cryptographic libraries.

It is highly recommended to use modern security practices and avoid relying on the obsolete IE Pinning mechanism.