Control Objective

One of the core components of any web-based application or stateful API is the mechanism by which it controls and maintains the state for a user or device interacting with it. Session management changes a stateless protocol to stateful, which is critical for differentiating different users or devices.

Ensure that a verified application satisfies the following high-level session management requirements:

• Sessions are unique to each individual and cannot be guessed or shared.
• Sessions are invalidated when no longer required and timed out during periods of inactivity.

As previously noted, these requirements have been adapted to be a compliant subset of selected NIST 800-63b controls, focused around common threats and commonly exploited authentication weaknesses. Previous verification requirements have been retired, de-duped, or in most cases adapted to be strongly aligned with the intent of mandatory NIST 800-63b requirements.

Security Verification Requirements

V3.1 Fundamental Session Management Requirements

V3.2 Session Binding Requirements

TLS or another secure transport channel is mandatory for session management. This is covered off in the Communications Security chapter.

V3.3 Session Logout and Timeout Requirements

Session timeouts have been aligned with NIST 800-63, which permits much longer session timeouts than traditionally permitted by security standards. Organizations should review the table below, and if a longer time out is desirable based around the application’s risk, the NIST value should be the upper bounds of session idle timeouts.

L1 in this context is IAL1/AAL1, L2 is IAL2/AAL3, L3 is IAL3/AAL3. For IAL2/AAL2 and IAL3/AAL3, the shorter idle timeout is, the lower bound of idle times for being logged out or re-authenticated to resume the session.

V3.4 Cookie-based Session Management

V3.5 Token-based Session Management

Token-based session management includes JWT, OAuth, SAML, and API keys. Of these, API keys are known to be weak and should not be used in new code.

V3.6 Re-authentication from a Federation or Assertion

This section relates to those writing Relying Party (RP) or Credential Service Provider (CSP) code. If relying on code implementing these features, ensure that these issues are handled correctly.

V3.7 Defenses Against Session Management Exploits

There are a small number of session management attacks, some related to the user experience (UX) of sessions. Previously, based on ISO 27002 requirements, the ASVS has required blocking multiple simultaneous sessions. Blocking simultaneous sessions is no longer appropriate, not only as modern users have many devices or the app is an API without a browser session, but in most of these implementations, the last authenticator wins, which is often the attacker. This section provides leading guidance on deterring, delaying and detecting session management attacks using code.

Description of the half-open Attack

In early 2018, several financial institutions were compromised using what the attackers called “half-open attacks”. This term has stuck in the industry. The attackers struck multiple institutions with different proprietary code bases, and indeed it seems different code bases within the same institutions. The half-open attack is exploiting a design pattern flaw commonly found in many existing authentication, session management and access control systems.

Attackers start a half-open attack by attempting to lock, reset, or recover a credential. A popular session management design pattern re-uses user profile session objects/models between unauthenticated, half-authenticated (password resets, forgot username), and fully authenticated code. This design pattern populates a valid session object or token containing the victim’s profile, including password hashes and roles. If access control checks in controllers or routers does not correctly verify that the user is fully logged in, the attacker will be able to act as the user. Attacks could include changing the user’s password to a known value, update the email address to perform a valid password reset, disable multi-factor authentication or enroll a new MFA device, reveal or change API keys, and so on.

References

For more information, see also:

• OWASP Testing Guide 4.0: Session Management Testing
• OWASP Session Management Cheat Sheet
• Set-Cookie __Host- prefix details

What is the ASVS?

The OWASP Application Security Verification Standard (ASVS) Project provides a basis for testing web application technical security controls and also provides developers with a list of requirements for secure development.

The primary aim of the OWASP Application Security Verification Standard (ASVS) Project is to normalize the range in the coverage and level of rigor available in the market when it comes to performing Web application security verification using a commercially-workable open standard. The standard provides a basis for testing application technical security controls, as well as any technical security controls in the environment, that are relied on to protect against vulnerabilities such as Cross-Site Scripting (XSS) and SQL injection. This standard can be used to establish a level of confidence in the security of Web applications. The requirements were developed with the following objectives in mind:

• Use as a metric – Provide application developers and application owners with a yardstick with which to assess the degree of trust that can be placed in their Web applications,
• Use as guidance – Provide guidance to security control developers as to what to build into security controls in order to satisfy application security requirements, and
• Use during procurement – Provide a basis for specifying application security verification requirements in contracts.

Using the OWASP ASVS

OWASP ASVS has two main goals:

• to help organizations develop and maintain secure applications.
• to allow security service vendors, security tools vendors, and consumers to align their requirements and offerings.

Application Security Verification Levels

The Application Security Verification Standard defines three security verification levels, with each level increasing in depth.

• ASVS Level 1 is for low assurance levels, and is completely penetration testable
• ASVS Level 2 is for applications that contain sensitive data, which requires protection and is the recommended level for most apps
• ASVS Level 3 is for the most critical applications – applications that perform high value transactions, contain sensitive medical data, or any application that requires the highest level of trust.

Each ASVS level contains a list of security requirements. Each of these requirements can also be mapped to security-specific features and capabilities that must be built into software by developers.

Level 1 is the only level that is completely penetration testable using humans. All others require access to documentation, source code, configuration, and the people involved in the development process. However, even if L1 allows “black box” (no documentation and no source) testing to occur, it is not an effective assurance activity and should be actively discouraged. Malicious attackers have a great deal of time, most penetration tests are over within a couple of weeks. Defenders need to build in security controls, protect, find and resolve all weaknesses, and detect and respond to malicious actors in a reasonable time. Malicious actors have essentially infinite time and only require a single porous defense, a single weakness, or missing detection to succeed. Black box testing, often performed at the end of development, quickly, or not at all, is completely unable to cope with that asymmetry.

Over the last 30+ years, black box testing has proven over and over again to miss critical security issues that led directly to ever more massive breaches. We strongly encourage the use of a wide range of security assurance and verification, including replacing penetration tests with source code led (hybrid) penetration tests at Level 1, with full access to developers and documentation throughout the development process. Financial regulators do not tolerate external financial audits with no access to the books, sample transactions, or the people performing the controls. Industry and governments must demand the same standard of transparency in the software engineering field.

We strongly encourage the use of security tools within the development process itself. DAST and SAST tools can be used continuously by the build pipeline to find easy to find security issues that should never be present.

Automated tools and online scans are unable to complete more than half of the ASVS without human assistance. If comprehensive test automation for each build is required, then a combination of custom unit and integration tests, along with build initiated online scans are used. Business logic flaws and access control testing is only possible using human assistance. These should be turned into unit and integration tests.

How to use this standard

One of the best ways to use the Application Security Verification Standard is to use it as a blueprint to create a Secure Coding Checklist specific to your application, platform or organization. Tailoring the ASVS to your use cases will increase the focus on the security requirements that are most important to your projects and environments.

Level 1 – First steps, automated, or whole of portfolio view

An application achieves ASVS Level 1 if it adequately defends against application security vulnerabilities that are easy to discover, and included in the OWASP Top 10 and other similar checklists.

Level 1 is the bare minimum that all applications should strive for. It is also useful as a first step in a multi-phase effort or when applications do not store or handle sensitive data and therefore do not need the more rigorous controls of Level 2 or 3. Level 1 controls can be checked either automatically by tools or simply manually without access to source code. We consider Level 1 the minimum required for all applications.

Threats to the application will most likely be from attackers who are using simple and low effort techniques to identify easy-to-find and easy-to-exploit vulnerabilities. This is in contrast to a determined attacker who will spend focused energy to specifically target the application. If data processed by your application has high value, you would rarely want to stop at a Level 1 review.

Level 2 – Most applications

An application achieves ASVS Level 2 (or Standard) if it adequately defends against most of the risks associated with software today.

Level 2 ensures that security controls are in place, effective, and used within the application. Level 2 is typically appropriate for applications that handle significant business-to-business transactions, including those that process healthcare information, implement business-critical or sensitive functions, or process other sensitive assets, or industries where integrity is a critical facet to protect their business, such as the game industry to thwart cheaters and game hacks.

Threats to Level 2 applications will typically be skilled and motivated attackers focusing on specific targets using tools and techniques that are highly practiced and effective at discovering and exploiting weaknesses within applications.

Level 3 – High value, high assurance, or high safety

ASVS Level 3 is the highest level of verification within the ASVS. This level is typically reserved for applications that require significant levels of security verification, such as those that may be found within areas of military, health and safety, critical infrastructure, etc.

Organizations may require ASVS Level 3 for applications that perform critical functions, where failure could significantly impact the organization’s operations, and even its survivability. Example guidance on the application of ASVS Level 3 is provided below. An application achieves ASVS Level 3 (or Advanced) if it adequately defends against advanced application security vulnerabilities and also demonstrates principles of good security design.

An application at ASVS Level 3 requires more in depth analysis of architecture, coding, and testing than all the other levels. A secure application is modularized in a meaningful way (to facilitate resiliency, scalability, and most of all, layers of security), and each module (separated by network connection and/or physical instance) takes care of its own security responsibilities (defense in depth), that need to be properly documented. Responsibilities include controls for ensuring confidentiality (e.g. encryption), integrity (e.g. transactions, input validation), availability (e.g. handling load gracefully), authentication (including between systems), non-repudiation, authorization, and auditing (logging).

Source: https://owasp.org/www-project-application-security-verification-standard/

Note: The OWASP ASVS, related copyright and trademarks belong to its owner OWASP. This guide is for educational purposes only and will be expanded beyond the original version provided by OWASP.