OWASP Periodic Table of Vulnerabilities
After 25 years of software engineering since the first Internet worm was written to exploit a buffer overflow vulnerability, web developers are still building insecure software. It is time for a new approach. The vast majority of software bug classes can be eliminated by building protections into perimeter technologies, platform infrastructures, and application frameworks before a developer even writes a single line of custom code. By allowing developers to focus on just a small subset of bug classes, training and standards programs can be more targeted and effective so developers can write secure code much more efficiently.
Vulnerabilities and weaknesses from industry-recognized indexes including OWASP Top 10, WASC TCv2, and CWE-25 are analyzed to determine which of the protection options are ideal for solving the software security problem. Where changes to internet standards and protocols are required, alternatives in perimeter, framework, or custom code solutions are also provided until the internet-scale solutions are in place. If a solution can be completely implemented in perimeter or infrastructure technologies, only that solution is provided. Similarly, if any part of the solution can be provided in standard or custom frameworks, that solution is not recommended to be implemented in custom code. The guiding principle is essentially: "implement security controls as far from custom code as possible." Only if there is no other way to solve a particular security problem is a custom code solution recommended.
Browsers, Standards, and Protocols
The most scalable and effective approach to addressing vulnerability classes is to fix the browsers, standards, and protocols that enable web applications. This approach can sometimes increase security for every application on the internet without changing a single custom application. The amount of industry collaboration required to implement a protocol/standard change can be enormous, but some classes of vulnerabilities simply cannot be addressed without this kind of change (e.g. Clickjacking). A solution at this level is also incredibly powerful: a CSP-based solution to Cross-Site Scripting might allow most application owners to write a simple policy file instead of implementing a costly framework or custom code solution to protect their existing application assets.
Less scalable, but almost as effective, is to address vulnerabilities in perimeter technologies such as application firewalls, load balancers, geocaching services (e.g. Akamai), and proxies. These technologies can shield vulnerable applications without requiring changes to the applications themselves. While most classes of vulnerability depend heavily on the application code and aren't easily solved by a generic perimeter solution, some are generalizable to the point where a perimeter solution could protect any application behind it before an attack even has a chance to do damage. Anti-automation and protocol validation are especially good solutions for perimeter technologies to address.
Generic Application Frameworks
The next most scalable approach requires upgrading popular application frameworks so they are robust against common attack classes. Common web application platforms such as Java Struts/J2EE, Ruby on Rails, and PHP can theoretically prevent developers from introducing most classes of vulnerability in the first place. However, the current state of the framework industry is more driven by features than by security; any conflict between the two is usually decided in favor of adding features and ease of use, as opposed to difficult-to-use security enhancements. Some frameworks even have built-in vulnerabilities out of the box!
Improvements to application frameworks won't immediately help protect existing applications (though they would make any new applications built on the platform much safer). Many applications currently rely on insecure features of their frameworks that would be eliminated or refactored when the framework is secured. Existing applications would need to follow an upgrade path provided by a "secure" branch of existing frameworks before these solutions could take effect. Many applications don't even use popular frameworks at all, and so could never be helped by improvements to common development platforms.
Generic Framework solution guidelines would, however, help application owners prioritize refactoring efforts for their existing applications in order to make their application code more robust against future development mistakes. This is true whether their applications use popular frameworks or not. Implementing a robust solution to a vulnerability class is much more cost-effective in the long run than training every developer to understand every vulnerability and continuously patching new instances of the vulnerability each time they appear. Cross-Site Scripting is a classic example of the "whac-a-mole vulnerability" that recurrently wastes developer time and attention and could be solved more holistically with a framework wrapper.
Custom Application Frameworks
Some solutions are unique to a specific application and can't be defended by a generic framework solution. For example, a generic framework might ship with a Social Security Number (SSN) validator, but a custom framework solution would be needed for a CustomWidgetItem validator. The SSN data type is well-defined and not unique to a specific application or business, but the CustomWidgetItem is unique to that application and has its own validation rules.
Organizations should still customize application frameworks to support their own application-specific APIs and security controls. Developers can leverage these controls during development instead of having to build the controls in during their daily coding efforts. If developers use a CustomWidgetItem object that has already been validated by framework code, it is much more likely that they will use it safely than if they have to remember to do their own validation each time they use the object.
If none of the other solution options are possible for a given vulnerability class, developers will be required to protect against that class in every line of code that they write, which does not scale effectively at all. Some classes of attacks, such as Abuse of Functionality, depend completely on the custom code and cannot be abstracted at all into other solution models.
The set of vulnerabilities which must be eliminated in custom code is only a small fraction of the total vulnerability space. By focusing training and testing efforts on just this set of issues, after addressing all other problems in a more scalable manner, developers have a much better chance of building secure applications in the future.
|Vulnerability||Standards||Infrastructure/Perimeter||Generic Framework||Custom Framework||Custom Code|
|Abuse of Functionality||All features should have defined abuse cases and implemented protections against these abuses.|
|Application Misconfiguration||Ensure proper application settings are deployed in configuration file/s. Varies by platform and technology stack.|
|Brute Force (Generic) / Insufficient Anti-automation||Perimeter technologies including geocaching/proxy services must support automatic and/or manual "panic button" anti-automation, enforcing progressive CAPTCHA for unvalidated requests, triggering on excessive 5XX responses, or direct signal from application.||Provide configurable per-user/session request rate limits.||Provide a common configuration functionality available to any feature.||Any feature sensitive to high transaction rates should expose configurable rate limits per user or globally per feature.|
|Brute Force Login||Provide progressive lockout for failed authentication requests to a single account and detection/alerting for fixed-password variable-username attack detection.|
|Brute Force Session Identifier||Detect and alert on a configurable rate of session ID cache misses.|
|Brute Force Predictable Resource Location/Insecure Indexing||Generic anti-automation response should trigger during spikes in 4XX responses.||Provide a configurable GUID-based obfuscator for sensitive parameter values. Do not expose administrative interfaces on the same path as user interfaces.||Require authentication wherever possible. Create independent interfaces for administrative access and enforce stricter authentication rules.|
|Buffer Overflow||Defend infrastructure from known exploit signatures (e.g. CodeRed) and alert/block parameter anomalies.||Build on a memory-managed code platform or otherwise prohibit direct memory management.|
|Clickjacking||Browser vendors should standardize on CSP directives to support safe framing options for framed sites.||Support configurable options for setting X-Frame-Options header and automatically embedding framebusting code in HTML/Script/CSS for older user agents that do not support XFO.|
|Content Spoofing||Provide a new response status code for "File not found, but show custom 404 content body AND replace the URL displayed in the title bar because the current requested URL will confuse users".||If the framework supports user-supplied content, such content must be clearly marked as such in the display context. Alert when custom 404 is displayed.|
|Cookie Theft/Session Hijacking||Terminate/regenerate session if the session token is transmitted insecurely.||Enforce Secure and HttpOnly flags for all cookies. Alert user and deauthorize oldest session when multiple simultaneous login is detected. Terminate session if User-Agent string or other client fingerprinting changes. Terminate session if user acceses login page.|
|Credential/Session Prediction||Provide a secure random token generator AND use it to generate session IDs.|
|Cross Site Scripting (XSS) - DOM-Based||"Web 2.0" frameworks must expose an API for page creation/modification that does not use document.write/ln or allow dynamic data to be injected into innerHTML or similar DOM element attributes.|
|Cross-Site Request Forgery||Change default browser behavior to look for policy file for cross-domain writes instead of "default allow", transitioning through CSP framework.||Automatically generate and check tokens for all POST requests by default, with configuration-based exclusion list. Disallow state changes via GET requests, enforcing RFC.|
|Denial of Service (Application Based)||See Brute Force (Generic)||Profile resource-dependent transactions and build transaction queues and alerting when queues reach thresholds. Enforce transaction-based rate limits.|
|Denial of Service (Connection Based)||Recognize and dynamically adapt to deliberately slowed connection attempts by dropping slower connections during a detected event. The perimeter should protect itself and the Web server from saturation by slow connections.|
|Directory Indexing||Disable directory listings in the web- or application-server configuration by default.|
|Fingerprinting||Infrastructure should not leak any information which can be used to identify the platform or infrastructure technology. Perimeter technologies should strip all such information from outgoing responses.||URL structure should not reveal the underlying technology.|
|Format String||Alert and/or block on known format string signatures.||Prohibit access to vulnerable APIs and provide safe wrappers of those APIs instead.|
|HTTP Request/Response Smuggling||Tighten RFC standards to describe precise behavior for malformed request/response data. Shame non-conforming implementations into compliance. Increase SSL adoption to prevent proxy tampering.||Enforce strict parity match between requests and responses, discarding extraneous Content-Length headers and canonicalizing requests/responses.|
|HTTP Response Splitting||Automatically URL-encode CRLF characters in dynamic data before writing to HTTP response headers.|
|HTTP Request Splitting||Tighten RFC standards to describe precise behavior for malformed requests. Shame non-conforming implementations into compliance. Increase SSL adoption to prevent proxy poisoning.||Enforce strict canonicalization on all incoming HTTP requests.|
|Implicit Logout||Detect when a user browses away from the site and automatically log the user out of the application.|
|Improper Filesystem Permissions||Ensure that proper file and directory permissions are applied. Enforce stricter default permissions.|
|Improper Input Handling||Provide canonicalization and positive validation APIs for common data types, with configurable rules to reject or sanitize bad data.||Provide canonicalization and positive validation APIs for custom data types, strictly enforcing business rules, with configurable rules to reject or sanitize bad data.||Never use primitives in custom code.|
|Improper Output Handling||Provide context-sensitive encoders for all common data types in all output contexts, ensuring no custom code can write directly to output.||Provide context-sensitive encoders for all custom data types in all output contexts, ensuring no custom code can write directly to output.|
|Insufficient Authentication/Authorization||Provide configuration-based authentication and authorization platform.||Apply least-privilege principle to all transactions, requiring authentication and authorization where applicable.|
|Insufficient Data Protection||Provide a configuration-based suite of encryption utilities for all data security needs including HMAC, symmetric, password hash, and asymmetric encryption requirements.|
|Insufficient Password Recovery||Provide generic credential recovery with configurable "secret question" and multi-factor side-channel authentication functionality (e.g. SMS, email, etc.).|
|Insufficient Process Validation||Require state validation rules to be specified for multi-step flows.||Enforce state validation for asynchronous transactions.|
|Insufficient Session Expiration||Provide and enforce configurable absolute and inactivity-based session timeouts.|
|Insufficient Transport Layer Protection||Fix DNS and browser technologies so that the intent of domain owners can be more strictly followed.||Enforce Strict Transport Security and redirect any HTTP request to HTTPS.|
|Integer Overflow/Underflow||Provide safe wrappers for primitive numeric types.||Never use primitives without strict checking for underflow/overflow conditions.|
|LDAP Injection||Provide safe libraries for LDAP communication which properly encode dynamic data.|
|Mail Command Injection||Provide safe libraries for SMTP and IMAP interaction that properly encode dynamic data.|
|Null Byte Injection||Alert and/or block on known null byte attacks.||Provide safe libraries that automatically encode dynamic data in any context which uses null bytes as control characters.|
|OS Commanding||Build safe wrappers for system calls which prevent dynamic data from changing the intended meaning of the call.|
|Path Traversal||Canonicalize URLs and prevent directory access outside the web root.||Provide safe libraries for accessing the file system which canonicalize path references and enforce proper access control.|
|Race Conditions||Prevent singletons from instantiating class-scope objects. Provide transaction integrity for task queues.|
|Remote File Inclusion||Define a standard for safe inclusion of 3rd-party code and content which enforces namespace separation and mediates namespace/DOM access.||Provide proxy library to sanitize/sandbox third-party code and content for safe inclusion (e.g. Caja).|
|Routing Detour||Provide configuration-based whitelist for WS Routing destinations.|
|Server Misconfiguration||Ensure proper application settings are deployed in configuration file/s. Provide secure default settings.|
|Session Fixation||Do not start sessions with user-provided tokens and rotate session IDs periodically during longer sessions. Reissue new tokens automatically whenever the privilege level of the user changes.|
|SOAP Array Abuse, XML Attribute Blowup, XML Entity Expansion||Perform schema validation of XML structure on incoming requests.|
|SSI Injection||Do not support SSI with dynamic file names.|
|SQL Injection||Provide safe libraries for communicating with SQL servers which enforce parameterized query patterns.||Do not create queries with dynamic data in stored procedures.|
|Weak Authentication Methods||Reject HTTP Basic Auth, NTLM, and Digest Authentication requests.|
|XPath Injection||Provide safe libraries for constructing XPath queries with dynamic data.|
|XML External Entities||Disable External Entities within the XML parser.|
|XML Injection||Provide safe libraries for constructing XML documents which automatically encode dynamic data.|
|XQuery Injection||Provide safe libraries for XQuery construction which parameterize query values.|
Brute Force (Generic) / Insufficient Anti-automation
Root Cause Summary
Applications do not define or detect when request rates are outside the bounds of normal, acceptable use.
Browser / Standards Solution
Perimeter technologies including geocaching/proxy services must support automatic and/or manual "panic button" anti-automation, enforcing progressive CAPTCHA for unvalidated requests, triggering on excessive 5XX responses, or direct signal from application.
Generic Framework Solution
Provide configurable per-user/session request rate limits. For authenticated transactions, limits should be configurable on a per-user or per-session basis. Configuration should allow combining multiple limits of the form "# of requests per time period". For example, an administrator should be combine "10 requests per minute" with "500 requests per day" in order to simultaneously apply policies which prevent users from automatic crawling/screen scraping as well as longer-term slow leeching activities.
Custom Framework Solution
Provide a common configuration functionality available to any feature/function. Configuration settings should allow multiple per-user rate limits as well as global rate limits to prevent denial of service.
Custom Code Solution
Any feature sensitive to high transaction rates should expose configurable rate limits per user or globally per feature.
Discussion / Controversy
Generic framework solution requires too much overhead to track request limits. Request rate limiting should be done in perimeter, not framework. Should combine with Denial of Service (Application-Based)? Custom Code solution is the same as Custom Framework Solution; Custom Code solution should be pushed into framework.
- Sample Infographic - One-pager that highlights the vulnerability classes that developers will still have to worry about at the top, with "solved" vulnerabilities ordered toward the bottom.
- Working View/Summary - Working view summarizes solutions in respective columns for quick reference but doesn't provide details. May link to detailed sections.
- Solution Detail - Detailed view combines references, detailed solution designs, discussion/controversy detail, and other relevant information for each solution recommendation. The detail view does NOT explain what each vulnerability/weakness is - it only references existing vulnerability descriptions from other projects (e.g. OWASP Top 10, WASC TCv2, CWE, etc.). A short summary of root cause(s) is included, but only to the level of depth required to suggest all of the solution design elements that need to be addressed.
- Solution Checklist - Summary of solutions grouped by target (e.g. perimeter or framework) so that maintainers of standards, frameworks, and perimeter technologies can view the solutions required for their areas ONLY. May require templating to generate list automatically, or short summaries in place of detailed descriptions.
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