Detecting Security Vulnerabilities  in Web Applications Using Dynamic Analysis with Penetration Testing Andrew Petukhov [e...
Contents <ul><li>Input validation vulnerabilities. Detection techniques </li></ul><ul><li>Drawbacks of the Taint Propagati...
Input Validation Vulnerabilities Common approaches: Taint propagation <ul><li>Implemented in static analyzers and runtime ...
Input Validation Vulnerabilities Common approaches: Syntactic checking <ul><li>Implemented in static analyzers and runtime...
Approaches-Do-Not-Work example <ul><li>Web application module A: </li></ul><ul><ul><li>Receive user data via HTTP request;...
Drawbacks of the Taint Propagation approach <ul><li>Untyped data taintedness; </li></ul><ul><li>Inability to handle saniti...
Possible solutions <ul><li>Introduce classes for data taintedness (xss, shell, sql, etc.). Solves drawback  № 1. </li></ul...
Implementation considerations <ul><li>Implement as Static analyzer: </li></ul><ul><ul><li>Pro: Completeness </li></ul></ul...
Security and Development Life Cycle <ul><li>Design: Threat Modeling, Safe Technologies </li></ul><ul><li>Implementation: S...
Decision: Dynamic analysis with Pentesting Our Motivation <ul><li>We want the tool to: </li></ul><ul><ul><li>Aid in web ap...
Implementation architecture <ul><li>Pentest module based on OWASP WebScarab </li></ul><ul><li>Fuzz vectors – OWASP Fuzzing...
Conclusions <ul><li>We have defined several drawbacks of the existing input validation vulnerabilities detection approache...
Future work <ul><li>Perform extensive evaluation </li></ul><ul><ul><li>Currently, we have tested our approach on the four ...
Thank You!  Any question?
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Detecting Security Vulnerabilities in Web Applications Using Dynamic Analysis with Penetration Testing

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This talk was given at OWASP AppSec Europe 2008.
Full paper can be downloaded from here:
http://www.owasp.org/images/3/3e/OWASP-AppSecEU08-Petukhov.pdf

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Detecting Security Vulnerabilities in Web Applications Using Dynamic Analysis with Penetration Testing

  1. 1. Detecting Security Vulnerabilities in Web Applications Using Dynamic Analysis with Penetration Testing Andrew Petukhov [email_address] Department of Computer Science Moscow State University
  2. 2. Contents <ul><li>Input validation vulnerabilities. Detection techniques </li></ul><ul><li>Drawbacks of the Taint Propagation approach </li></ul><ul><li>Solving drawbacks of the Taint Propagation approach </li></ul><ul><li>Implementing integrated Dynamic Analysis with Penetration Testing approach </li></ul><ul><li>Conclusions and Future work </li></ul>
  3. 3. Input Validation Vulnerabilities Common approaches: Taint propagation <ul><li>Implemented in static analyzers and runtime protection systems </li></ul><ul><li>Vulnerability Model: </li></ul><ul><ul><li>All data received via HTTP-requests is untrustworthy; </li></ul></ul><ul><ul><li>All local data is trustworthy; </li></ul></ul><ul><ul><li>Untrustworthy data can be made trustworthy by special kinds of processing; </li></ul></ul><ul><ul><li>Untrustworthy data should not be used in sensitive operations: HTTP response construction, database queries, systems calls, eval statements, etc. </li></ul></ul>
  4. 4. Input Validation Vulnerabilities Common approaches: Syntactic checking <ul><li>Implemented in static analyzers and runtime protection systems </li></ul><ul><li>Vulnerability Model: </li></ul><ul><ul><li>Queries to external services (DBMS, OS interpreter, LDAP, etc.) usually have fixed syntactic structure; </li></ul></ul><ul><ul><li>Input validation vulnerabilities render possible injection attacks, which alter the syntactic structure of queries; </li></ul></ul><ul><ul><li>The syntactic structure of such queries should not depend on the user input. </li></ul></ul>
  5. 5. Approaches-Do-Not-Work example <ul><li>Web application module A: </li></ul><ul><ul><li>Receive user data via HTTP request; </li></ul></ul><ul><ul><li>Encode HTML special characters, escape SQL special characters; </li></ul></ul><ul><ul><li>Store data in database table (ex. table A, column a). </li></ul></ul><ul><li>Web application module B: </li></ul><ul><ul><li>Retrieve data from column ‘a’ of table A; </li></ul></ul><ul><ul><ul><li>The data is returned unescaped and therefore SQL-tainted! </li></ul></ul></ul><ul><ul><li>Use this data in another database query. </li></ul></ul><ul><ul><ul><li>Here comes input validation vulnerability that allows second order SQL injection attack! </li></ul></ul></ul>
  6. 6. Drawbacks of the Taint Propagation approach <ul><li>Untyped data taintedness; </li></ul><ul><li>Inability to handle sanitization performed by conditional branching: </li></ul><ul><li>Trust to sanitization routines; </li></ul><ul><li>Intra-module scope of view. </li></ul>
  7. 7. Possible solutions <ul><li>Introduce classes for data taintedness (xss, shell, sql, etc.). Solves drawback № 1. </li></ul><ul><li>Use Taint Propagation with Syntactic checking. Solves drawback №2 . </li></ul><ul><li>Use penetration testing for input generation for dynamic analysis or string analysis in static to validate sanitization routines. Solves drawback № 3. </li></ul><ul><li>Interconnect Data Flow Graphs built for separate modules using information about database interactions. Solves drawback №4 . </li></ul>
  8. 8. Implementation considerations <ul><li>Implement as Static analyzer: </li></ul><ul><ul><li>Pro: Completeness </li></ul></ul><ul><ul><ul><li>Reason: if sound analysis says there are no vulnerabilities, it’s truth </li></ul></ul></ul><ul><ul><li>Contra: False positives </li></ul></ul><ul><ul><ul><li>Reason: dynamic nature of scripting languages, undecidability of static analysis </li></ul></ul></ul><ul><li>Implement as Dynamic analyzer with Penetration tester: </li></ul><ul><ul><li>Pro: Precise reporting </li></ul></ul><ul><ul><ul><li>Reason: every single variable value could be observed </li></ul></ul></ul><ul><ul><li>Contra: Incompleteness </li></ul></ul><ul><ul><ul><li>Reason: depends on the coverage of the test cases </li></ul></ul></ul>
  9. 9. Security and Development Life Cycle <ul><li>Design: Threat Modeling, Safe Technologies </li></ul><ul><li>Implementation: Safe Coding </li></ul><ul><li>Testing: Penetration Testing, Dynamic and Static analysis </li></ul><ul><li>Operation: Web Application Firewalls, Runtime Protection, Sandboxing </li></ul><ul><li>Assessment: Code Review, Static Analysis, Penetration Testing </li></ul>
  10. 10. Decision: Dynamic analysis with Pentesting Our Motivation <ul><li>We want the tool to: </li></ul><ul><ul><li>Aid in web application testing (or Assessment); </li></ul></ul><ul><ul><li>Produce accurate results (no useless investigation); </li></ul></ul><ul><ul><li>Utilize test cases used during the testing phase (in theory, these test cases are specially developed by testing staff to achieve good coverage); </li></ul></ul><ul><ul><li>Require minimal configuration. </li></ul></ul><ul><li>We do not require the tool to: </li></ul><ul><ul><li>Satisfy high performance requirements (this is not protection system, it’s not vital); </li></ul></ul><ul><ul><li>Address coverage issues (operate only with the supplied test cases). </li></ul></ul>
  11. 11. Implementation architecture <ul><li>Pentest module based on OWASP WebScarab </li></ul><ul><li>Fuzz vectors – OWASP Fuzzing Codebase </li></ul><ul><li>Dynamic analysis – instrumented Python 2.4.4 </li></ul>
  12. 12. Conclusions <ul><li>We have defined several drawbacks of the existing input validation vulnerabilities detection approaches; </li></ul><ul><li>We have pointed out possible solutions to each of the stated drawbacks; </li></ul><ul><li>We have extended the formal Tainted Mode model to incorporate inter-module data flows; </li></ul><ul><li>We have developed an automated tool that detects input validation vulnerabilities using dynamic analysis and penetration testing. </li></ul>
  13. 13. Future work <ul><li>Perform extensive evaluation </li></ul><ul><ul><li>Currently, we have tested our approach on the four vulnerable web applications, successfully detecting already known vulnerabilities; </li></ul></ul><ul><ul><li>Evaluate our approach against more web applications; </li></ul></ul><ul><ul><li>Assess each web application with penetration testing tool, dynamic analysis tool and integrated tool, then compare the results; </li></ul></ul><ul><ul><li>Assess TCO of the developed tool. </li></ul></ul><ul><li>Address the initial phase: automated preparation of the input test cases, integration with code coverage analysis tool. </li></ul>
  14. 14. Thank You! Any question?

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