OWASP ASVS – V13 – API and Web Service Verification Requirements

Control Objective

Ensure that a verified application that uses trusted service layer APIs (commonly using JSON or XML or GraphQL) has:

Adequate authentication, session management and authorization of all web services.
Input validation of all parameters that transit from a lower to higher trust level.
Effective security controls for all API types, including cloud and Serverless API

Please read this chapter in combination with all other chapters at this same level; we no longer duplicate authentication or API session management concerns.

V13.1 Generic Web Service Security Verification Requirements

#	Description	L1	L2	L3	CWE
13.1.1	Verify that all application components use the same encodings and parsers to avoid parsing attacks that exploit different URI or file parsing behavior that could be used in SSRF and RFI attacks.	✓	✓	✓	116
13.1.2	Verify that access to administration and management functions is limited to authorized administrators.	✓	✓	✓	419
13.1.3	Verify API URLs do not expose sensitive information, such as the API key, session tokens etc.	✓	✓	✓	598
13.1.4	Verify that authorization decisions are made at both the URI, enforced by programmatic or declarative security at the controller or router, and at the resource level, enforced by model-based permissions.		✓	✓	285
13.1.5	Verify that requests containing unexpected or missing content types are rejected with appropriate headers (HTTP response status 406 Unacceptable or 415 Unsupported Media Type).		✓	✓	434

V13.2 RESTful Web Service Verification Requirements

JSON schema validation is in a draft stage of standardization (see references). When considering using JSON schema validation, which is best practice for RESTful web services, consider using these additional data validation strategies in combination with JSON schema validation:

Parsing validation of the JSON object, such as if there are missing or extra elements.
Validation of the JSON object values using standard input validation methods, such as data type, data format, length, etc.
and formal JSON schema validation.

Once the JSON schema validation standard is formalized, ASVS will update its advice in this area. Carefully monitor any JSON schema validation libraries in use, as they will need to be updated regularly until the standard is formalized and bugs are ironed out of reference implementations.

#	Description	L1	L2	L3	CWE
13.2.1	Verify that enabled RESTful HTTP methods are a valid choice for the user or action, such as preventing normal users using DELETE or PUT on protected API or resources.	✓	✓	✓	650
13.2.2	Verify that JSON schema validation is in place and verified before accepting input.	✓	✓	✓	20
13.2.3	Verify that RESTful web services that utilize cookies are protected from Cross-Site Request Forgery via the use of at least one or more of the following: double submit cookie pattern, CSRF nonces, or Origin request header checks.	✓	✓	✓	352
13.2.4	Verify that REST services have anti-automation controls to protect against excessive calls, especially if the API is unauthenticated.		✓	✓	770
13.2.5	Verify that REST services explicitly check the incoming Content-Type to be the expected one, such as application/xml or application/json.		✓	✓	436
13.2.6	Verify that the message headers and payload are trustworthy and not modified in transit. Requiring strong encryption for transport (TLS only) may be sufficient in many cases as it provides both confidentiality and integrity protection. Per-message digital signatures can provide additional assurance on top of the transport protections for high-security applications but bring with them additional complexity and risks to weigh against the benefits.		✓	✓	345

V13.3 SOAP Web Service Verification Requirements

#	Description	L1	L2	L3	CWE
13.3.1	Verify that XSD schema validation takes place to ensure a properly formed XML document, followed by validation of each input field before any processing of that data takes place.	✓	✓	✓	20
13.3.2	Verify that the message payload is signed using WS-Security to ensure reliable transport between client and service.		✓	✓	345

Note: Due to issues with XXE attacks against DTDs, DTD validation should not be used, and framework DTD evaluation disabled as per the requirements set out in V14 Configuration.

V13.4 GraphQL and other Web Service Data Layer Security Requirements

#	Description	L1	L2	L3	CWE
13.4.1	Verify that a query allow list or a combination of depth limiting and amount limiting is used to prevent GraphQL or data layer expression Denial of Service (DoS) as a result of expensive, nested queries. For more advanced scenarios, query cost analysis should be used.		✓	✓	770
13.4.2	Verify that GraphQL or other data layer authorization logic should be implemented at the business logic layer instead of the GraphQL layer.		✓	✓	285

References

For more information, see also:

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.

Updated on September 25, 2022

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