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Application Security Architecture and Threat Modelling

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95% of attacks are against “Web Servers and Web Applications”
Security Architecture and SDLC
3 Tier – Web App Architecture
Would you trust the code?
Traditional SDLC
Secure SDLC
SAST vs. DAST

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Application Security Architecture and Threat Modelling

  1. 1. Security Architecture and Threat Modelling Nilanjan De Devesh Bhatt
  2. 2. 95% of attacks are against “Web Servers and Web Applications”
  3. 3. Average 35 No of vulnerabilities in a website 52%of data breaches happen through Web Applications of Application has atleast one vulnerability 41 High 3 3 5 9 Mediu m Low The Scorecard 90% of hacking incidents are not reported 99% 82% of web applications have at least 1 High/Critical Vulnerability Business Logic Flaws are the most neglected vulnerabilities Source: IViZ blog
  4. 4. Security Architecture and SDLC
  5. 5. USER AGENTS User Agent / Client. Browser, BOT, Program Sends Requests like GET, POST, HEAD, PUT, DELETE WEB SERVERS ● Web Server listens for requests ● Has interpreters to understand PHP/ASP.net ● Talks to the database ● Has TCP ports in listening mode Database Server MySQL, MSSQL, Oracle 3 Tier – Web App Architecture
  6. 6. Web App Architecture – Data View Web Client Data Store Web Server Trusted Code Running on server Web Service Un-trusted Input hitting the server from the client, data stores, web services.
  7. 7. Would you trust the code? Operating System and Shell Web Server + Interpreter (PHP/ASP.net) Trusted Code
  8. 8. Traditional SDLC It’s too late!! We won’t meet our security standards.. Production Deadline Development + QA Pen Testing 189 Vulnerabilities Security is taken care of only at the end of the SDLC
  9. 9. Secure SDLC Production Deadline Development + QA + Security Pen Testing 12 Vulnerabilities Security is implemented during the SW development. • We can achieve application security • We save development time  $$
  10. 10. Enabling S-SDLC Source Repository Build Management System Static Analysis Tool Team City Jenkins Hudson Bamboo TFS SVN GIT Etc. Developers Team Leaders / Security team Production
  11. 11. Cost to find/fix a defect during integration/system test is 15-90 times higher than at design/coding Time & Cost Code Inspection Integration Testing System TestingStatic analysis tools find defects and design flaws “in phase” Unit Testing Design Coding QA Production Scan sources with checkmarx Scan binaries SAST vs. DAST
  12. 12. SAST vs. DAST  Dynamic Application Security Testing (DAST) - Can be performed only at the end of dev. - More layers covered - Not compete coverage (it is random). - Results not shown in the code  Static Application Security Testing (SAST) - Can be performed from the beginning of the SDLC - Covers only the application code - Covers all the application code - Results are shown inside the code - Has more false positive results 12
  13. 13. SAST vs. DAST  So what is better, DAST or SAST?  For good security both SAST and DAST are necessary and complete each other.  If you have SAST you will get better quality results from the DAST service 13
  14. 14. SAST Scanning  SAST vendors scan binaries - Need compilation environment - Need compliable code..  have to wait  SAST vendors scanning pure source code - Uses the virtual compiler technology - No need for compilation environment - Can scan from day one - Scan takes longer System is more flexible  can customize the system for less FP results. 14
  15. 15. Threat Modelling
  16. 16. Threat Modelling
  17. 17. Common Types of Attack Connection Fails Organizational Attacks Restricted Data Accidental Breaches in Security Automated Attacks Hackers Viruses, Trojan Horses, and Worms Denial of Service (DoS) DoS
  18. 18. Types of Threats Spoofed packets, etc. Buffer overflows, illicit paths, etc. SQL injection, XSS, input tampering, etc. Network Host Application Threats against the network Threats against the host Threats against the application
  19. 19. Threats Against the Network Threat Examples Information gathering Port scanning Using trace routing to detect network topologies Using broadcast requests to enumerate subnet hosts Eavesdropping Using packet sniffers to steal passwords Denial of service (DoS) SYN floods ICMP echo request floods Malformed packets Spoofing Packets with spoofed source addresses http://msdn.microsoft.com/library/en-us/dnnetsec/html/THCMCh15.asp? frame=true#c15618429_004
  20. 20. Threats Against the Host Threat Examples Arbitrary code execution Buffer overflows in ISAPI DLLs (e.g., MS01-033) Directory traversal attacks (MS00-078) File disclosure Malformed HTR requests (MS01-031) Virtualized UNC share vulnerability (MS00-019) Denial of service (DoS) Malformed SMTP requests (MS02-012) Malformed WebDAV requests (MS01-016) Malformed URLs (MS01-012) Brute-force file uploads Unauthorized access Resources with insufficiently restrictive ACLs Spoofing with stolen login credentials Exploitation of open ports and protocols Using NetBIOS and SMB to enumerate hosts Connecting remotely to SQL Server
  21. 21. Threats Against the Application Threat Examples SQL injection Including a DROP TABLE command in text typed into an input field Cross-site scripting Using malicious client-side script to steal cookies Hidden-field tampering Maliciously changing the value of a hidden field Eavesdropping Using a packet sniffer to steal passwords and cookies from traffic on unencrypted connections Session hijacking Using a stolen session ID cookie to access someone else's session state Identity spoofing Using a stolen forms authentication cookie to pose as another user Information disclosure Allowing client to see a stack trace when an unhandled exception occurs
  22. 22. Threat Modeling  Structured approach to identifying, quantifying, and addressing threats  Essential part of development process
  23. 23. The Threat Modeling Process Identify assets Document architecture Decompose application Identify threats Document threats Rate threats 1 2 3 4 5 6
  24. 24. Identifying Assets  What is it that you want to protect?  Private data (e.g., customer list)  Proprietary data (e.g., intellectual property)  Potentially injurious data (e.g., credit card numbers, decryption keys)  These also count as "assets"  Integrity of back-end databases  Integrity of the Web pages (no defacement)  Integrity of other machines on the network  Availability of the application
  25. 25. Documenting Architecture  Define what the app does and how it's used  Users view pages with catalog items  Users perform searches for catalog items  Users add items to shopping carts  Users check out  Diagram the application  Show subsystems  Show data flow  List assets
  26. 26. Example Bob Alice Bill Asset #4 Asset #1 Asset #2 Asset #3 Asset #5 Asset #6 IIS ASP.NET Web Server Login State Main Database Server Firewall
  27. 27. Decomposing the App  Refine the architecture diagram  Show authentication mechanisms  Show authorization mechanisms  Show technologies (e.g., DPAPI)  Diagram trust boundaries  Identify entry points  Begin to think like an attacker  Where are my vulnerabilities?  What am I going to do about them?
  28. 28. Example Bob Alice Bill IIS ASP.NET Web Server Database Server Trust Forms Authentication URL Authorization DPAPI Windows Authentication Firewall Login State Main
  29. 29. Identifying Threats  Method #1: Threat lists  Start with laundry list of possible threats  Identify the threats that apply to your app  Method #2: STRIDE  Categorized list of threat types  Identify threats by type/category  Optionally draw threat trees  Root nodes represent attacker's goals  Trees help identify threat conditions
  30. 30. STRIDE S T R I D Tampering Repudiation Information disclosure Denial of service Can an attacker gain access using a false identity? Can an attacker modify data as it flows through the application? If an attacker denies doing something, can we prove he did it? Can an attacker gain access to private or potentially injurious data? Can an attacker crash or reduce the availability of the system? E Elevation of privilege Can an attacker assume the identity of a privileged user? Spoofing
  31. 31. Documenting Threats Theft of Auth Cookies by Eavesdropping on Connection Threat target Connections between browsers and Web server Risk Attack techniques Attacker uses sniffer to monitor traffic Countermeasures Use SSL/TLS to encrypt traffic  Document threats using a template Theft of Auth Cookies via Cross-Site Scripting Threat target Vulnerable application code Risk Attack techniques Attacker sends e-mail with malicious link to users Countermeasures Validate input; HTML-encode output
  32. 32. Rating Threats  Simple model  DREAD model  Greater granularization of threat potential  Rates (prioritizes) each threat on scale of 1-15  Developed and widely used by Microsoft Risk = Probability * Damage Potential 1-10 Scale 1 = Least probable 10 = Most probable 1-10 Scale 1 = Least damage 10 = Most damage
  33. 33. DREAD D R E A D Reproducibility Exploitability Affected users Discoverability What are the consequences of a successful exploit? Would an exploit work every time or only under certain circumstances? How skilled must an attacker be to exploit the vulnerability? How many users would be affected by a successful exploit? How likely is it that an attacker will know the vulnerability exists? Damage potential
  34. 34. Example Threat D R E A D Sum Auth cookie theft (eavesdropping) 3 2 3 2 3 13 Auth cookie theft (XSS) 3 2 2 2 3 12 Potential for damage is high (spoofed identities, etc.) Cookie can be stolen any time, but is only useful until expired Anybody can run a packet sniffer; XSS attacks require moderate skill All users could be affected, but in reality most won't click malicious links Easy to discover: just type a <script> block into a field Prioritized Risks
  35. 35.  Produce software that’s secure by design  Improve designs the same way we’ve improved code  Because attackers think differently  Creator blindness/new perspective Why Threat Model
  36. 36. Diagram Elements - Examples •People •Other systems •Microsoft.com •etc… •Function call •Network traffic •Etc.… •DLLs •EXEs •Components •Services •Web Services •Assemblies •etc… •Database •File •Registry •Shared Memory •Queue/Stack •etc.… External entity Process Data Flow Data Store Trust Boundary •Process boundary •File system
  37. 37.  Add trust boundaries that intersect data flows  Points/surfaces where an attacker can interject  Machine boundaries, privilege boundaries, integrity boundaries are examples of trust boundaries  Threads in a native process are often inside a trust boundary, because they share the same rights and access  Processes talking across a network always have a trust boundary Diagrams: Trust Boundaries
  38. 38.  Context Diagram  Very high-level; entire component / product / system  Level 1 Diagram  High level; single feature / scenario  Level 2 Diagram  Low level; detailed sub-components of features  Level 3 Diagram  More detailed  Rare to need more layers, except in huge projects or when you’re drawing more trust boundaries Diagram layers
  39. 39. Castle Service Local User Castle Config Feedback Join/Leave Castle Remote Castle A Real Context Diagram
  40. 40. Castle Service Explorer (or rundll32) SSDP SSDP Remote Castle Service Registry LSA SAM Local User Shacct Get acct info Feedback Manage Castle Join, leave, Set users props Set acct info Read Castle info Set psswd Set acct info Feedback Get machine password Cache Castle info Query users props Query other Castle info Publish this Castle info Manage Castle Get acct info Get version info Set version info 1 2 3 4 5 6 7 8 9 10 A Real DFD
  41. 41. Understanding the threats Threat Property Definition Example Spoofing Authentication Impersonating something or someone else. Pretending to be any of billg, xbox.com or a system update Tampering Integrity Modifying data or code Modifying a game config file on disk, or a packet as it traverses the network Repudiation Non-repudiation Claiming to have not performed an action “I didn’t cheat!” Information Disclosure Confidentiality Exposing information to someone not authorized to see it Reading key material from an app Denial of Service Availability Deny or degrade service to users Crashing the web site, sending a packet and absorbing seconds of CPU time, or routing packets into a black hole Elevation of Privilege Authorization Gain capabilities without proper authorization Allowing a remote internet user to run commands is the classic example, but running kernel code from lower trust levels is also EoP
  42. 42. Different threats affect each type of element Process Data Store S T R I D E               Element ? Dataflow External Entity
  43. 43. Castle Service Explorer (or rundll32) SSDP SSDP Remote Castle Service Registry LSA SAM Local User Shacct Get acct info Feedback Manage Castle Join, leave, Set users props Set acct info Read Castle info Set psswd Set acct info Feedback Get machine password Cache Castle info Query users props Query other Castle info Publish this Castle info Manage Castle Get acct info Get version info Set version info 1 2 3 4 5 6 7 8 9 10 A Real Level-0 DFD (Castle) TID TID TID TID STRIDE STRIDE Etc…
  44. 44.  Address each threat  Four ways to address threats:  Redesign to eliminate  Apply standard mitigations  Invent new mitigations  Riskier  Accept vulnerability in design  Address each threat! Mitigate
  45. 45.  Validate the whole TM  Does diagram match final code?  Are threats enumerated?  Minimum: STRIDE per element that touches a trust boundary  Has Test reviewed the model?  Created appropriate test plans  Tester approach often finds issues with TM, or details  Is each threat mitigated?  Are mitigations done right Validating Threat Models
  46. 46. End exercise
  47. 47.  Uncover Security Design Flaws Using the STRIDE Approach http://msdn.microsoft.com/msdnmag/issues/06/11/ThreatModeling/default.asp x  http://msdn.microsoft.com/en-us/magazine/cc700352.aspx  http://msdn.microsoft.com/en-us/magazine/2009.01.securitybriefs.aspx  http://msdn.microsoft.com/en-us/security/cc448120.aspx References
  48. 48. Something to think about Password analysis from the rockyou.com data revealed  The most common password was; 123456  30% passwords were less than 6 characters  60% passwords were a limited set of alphanumeric (A-Z, a-z, 0-9) characters  23,000 passwords were set to; rockyou
  49. 49. Thank You!!

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