(My) CSSLP Notes – Secure Software Implementation

Note: This notes were strongly inspired by the following books: CSSLP Certification All in one and Official (ISC)2 Guide to the CSSLP CBK, Second Edition

Common Software Vulnerabilities and Controls

Some well-known and useful examples of vulnerability databases and CSSLP-logotracking systems:
  • National Vulnerability Database (NVD) -U.S. government repository of vulnerabilities and vulnerability management data.
  • US Computer Emergency Response Team (CERT) Vulnerability Notes Database – The CERT vulnerability analysis project aims at reducing security risks due to software vulnerabilities in both developed and deployed software.
  • Open Source Vulnerability Database – An independent and open source database that is created by and for the security community.
  • OWASP Top 10 – The OWASP Top 10 List, in addition to considering
    the most common application security issues from a weaknesses or
    vulnerabilities perspective, views application security issues from an
    organizational risks.
  • Common Weakness Enumeration (CWE) – Provides a common language for describing architectural, design or coding software security weaknesses.
  • Common Vulnerabilities and Exposures (CVE) – A dictionary of publicly known information security vulnerabilities and exposures. It is free for use and international in scope.

The most common software security vulnerabilities and risks

  • buffer overflow – is the condition that occurs when data that is being copied into the buffer (contiguous allocated storage space in memory) is more than what the buffer can handle.
    • stack overflow – buffer has been overflowed in the stack space.
      the data flows from one buffer space into another, causing the return address instruction pointer to be overwritten.
    • heap overflow – a heap overflows does not necessarily overflow but corrupts the heap memory space (buffer), overwriting variables and function pointers on the heap.
  • injection flows – occur when the user supplied data is not validated before being processed by an interpreter.
    • SQL injection
    • OS Command injection
    • LDAP injection
    • XML injection – software does not properly filter or quote special characters or reserved words that are used in XML, allowing an attacker to modify the syntax, contents or commands before execution.

  • cross-site scripting – A web application is said to be susceptible to XSS vulnerability when the user supplied input is sent back to the browser client without being properly validated and its content escaped.
    • Non-persistent (Reflected) – the user supplied input script that is injected (also referred to as payload) is not stored but merely included in the response from the web server, either in the results of a search or an error message.
    • Persistent (Stored) – the injected script is permanently stored on the target servers, either in a database, a message forum, a visitor log or an input field. Each time the victims visit the page that has the injected code stored in it or served to it from the web server, the payload script executes in the user’s browse

    • DOM based – the payload is executed in the victim’sbrowser as a result of DOM environment modifications on the client side. The HTTP response (or the web page) itself is not modified, but weaknesses in the client side allows the code contained in the web page client to be modified, so that the payload can be executed.

  • insecure direct object references – an unauthorized user or process can invoke the internal functionality of the software by manipulating parameters and other object values that directly reference this functionality.
  • security misconfiguration -Some of the common examples of security misconfigurations:
    • Missing software and operating system patches.
    • Lack of perimeter and host defensive controls such as firewalls,
      filters.
    • Installation of software with default accounts and settings.
    • Installation of the administrative console with default configuration settings.
  • social engineering
    • Phishing
    • Pharming – scamming practice in which malicious code is installed on a system or server which misdirects users to fraudulent web sites without the user’s knowledge or consent.
    • Vishing – made up of two words, “voice” and “phishing” and is the criminal fraudulent activity in which an attacker steals sensitive information using deceptive social engineering techniques on VoIP networks.
    • SMSishing

Defensive Coding Practices

  • input validation – use blacklist or whitelist technique.
  • canonicalization (C14N) -process of converting data that has more than one possible representation to conform to a standard canonical form.
  • sanitization -process of converting something that is considered dangerous into its innocuous form. Both inputs and outputs can be sanitized.
    • stripping – removing harmful characters from user supplied input.
    • substitution – replacing user supplied input with safer alternatives.
    • literalization – using properties that render the user supplied input to be treated as a literal form.
  • error handling – error messages must be non-verbose and explicitly specified in the software. Redirect errors and exceptions to a custom and default error handling location.
  • cryptographic agility – ability to manage the specifics of the cryptographic functions that are embedded in code without recompiling, typically through a configuration file.
  • tokenization – process of replacing sensitive data with unique
    identification symbols that still retain the needed information about the data, without compromising its security.
  • anti-tampering – techniques assure integrity assurance and protection against unauthorized and malicious alterations of the software code and/or the data.
    • obfuscation.
    • code-signing.

Secure Software Processes

In addition to writing secure code, there are certain processes that must be conducted during the implementation phase that can assure the security of the software:
  • versioning
  • code analysis
    • static
    • dynamic
  • code/peer review

5 (software) security books that every (software) developer should read

I must admit that the title is a little bit catchy; a better title would have been “5 software security books that every developer should be aware of“. Depending on your interest you might want to read entirely these books or you could just know that they exists. There must be tons of software security books on the market but this is my short list of books about software security that I think that each developer that is interested in software security should be aware of.

Hacking – the art of exploitation This book explains the basics of different hacking techniques, especially the non-web hacking techniques: how to find vulnerabilities (and defend against)  like buffer overflow or stack-based buffer overflow , how to write shellcodes, some basic concepts on cryptography and attacks linked to the cryptography like the man-in-the-middle attack of an SSL connection. The author tried to make the text easy for non-technical peoples but some programming experience is required (ideally C/C++) in order to get the best of this book. You can see my full review of the book here.

Iron-Clad Java: Building secure web applications This book presents the hacking techniques and the countermeasures for the web applications; you can see this books as complementary of the previous one; the first one contains the non-web hacking techniques, this one contains (only) web hacking techniques; XSS, CSRF, how to protect data at rest, SQL injection and other types of injections attacks. In order to get the most of the book some Java knowledge is required. You can see my full review of the book here.

Software Security-Building security in  This books explains how to introduce the security into the SDLC; how to introduce abuse cases and security requirements in the requirements phase, how to introduce risk analysis (also known as Threat Modeling) in the design phase and software qualification phase. I really think that each software developer should at least read the first chapter of the book where the authors explains why the old way of securing application (seeing the software applications as “black boxes” than can be protected using firewalls and IDS/IPS) it cannot work anymore in the today software landscape. You can see my full review of the book here: Part 1, Part 2 and Part 3.

The Tangled Web: A Guide to Securing Modern Web Applications This is another technical book about security on which you will not see a single line of code (the Software Security-Building security in is another one) but it highly instructive especially if you are a web developer. The book presents all the “bricks” of the today Internet: HTTP, WWW, HTML, Cookies, Scripting languages, how these bricks are implemented in different browsers and especially how the browsers are implementing the security mechanism against rogue applications. You can see my full review of the book here.

Threat modeling – designing for security Threat modeling techniques (also known as Architectural Risk Analysis) were around for some time but what it has changed in the last years is the accessibility of these technique for the software developers.  This book is one of the reasons for which the threat modeling is accessible to the developers. The book is very dense but it  suppose that you have no knowledge about the subject. If you are interested in the threat modeling topic you can check this ticket: threat modeling for mere mortals.

(My) BruCON 2016 notes (2)

Here are my quick notes from the BruCON 2016 conference. All the slides can be found here.

What Does the Perfect Door or Padlock Look Like?bruCon

The talk was about how (some) doors and padlocks can be easily opened. The presentation was full of videos and explanatory schemes. For the doors the following parts can be attacked:

  • hinge removal – to fix, use jam pins
  • the latch
  • the inside handle
  • key boxes
  • edge baps – request to exit sensors
  • the bottom gap
  • the door frame

Anti-Forensics AF

The presentation contained the following topics:

  • memory anti-forencics
    • the goal is to inhibit the acquisition and analysis
    • for windows, removing PE header from disk (once the executable is loaded in memory).
    • for windows, zero the header from disk (once the executable is loaded in memory).
    • for linux, remove the EMF header
    • for linux, zero the header (memeset)
  • android anti-forestics
    • use encryption to protect.
    • power down the device.
    • leverage device sensors; foe ex: if the phone is moving, then shut down the device
  • fun with sd cards
    • demo of the SDTool tool that modifies the SD card firmware to write/or not the card or in memory.

Esoteric Web application vulnerabilities

The sql injection vulnerability is dead due to the massive use of the ORM frameworks, the same for the XSS injections due to the mvc, templates and default HTML So, as a hacker you must find new vulnerabilities; here are 5 (esoteric) vulnerabilities:

  1. aggressive input decoding; nosql injection using ruby on rails and MongoDB
  2. call me to verify my identity; try to hack the phone activation procedure for a 2 FA functionality.
  3. password reset implementation feature; try to hack the password reset feature for a 2 FA
  4. hack around the usage of the Paypal IPN protoco
  5. just missed that one; it happen even to the best of us.

Scraping Leaky browsers for Fun and Password

The idea is to retrieve passwords stored by the browsers (in RAM) by scrapping the RAM content. Do to this a plug-in to Volatility framework was created (the plug-in will be available soon on GitHub).

The best browser is Chrome with 67% chances to expose the passwords; the worst browser is Firefox with 81% changes to expose the passwords.

Vendors response to this findings; Microsoft created a CVE and the path will be pushed in October/November, Google and Mozilla are denying that’s a real issue.

 

Book review: Iron-Clad Java Building Secure Web Applications

This a review of the Iron-Clad Java: Building Secure Web Applications book.

(My) Conclusion

I will start with the conclusion because it’s maybe the most important part of this review.

For me this is a must read book if you want to write more robust (web and non web) applications in Java, it covers a very large panel of topics from the basics of securing a web application using HTTP/S response headers to handling the encryption of sensitive informations in the right way.

Chapter 1: Web Application Security BasicsironCladJavaBook

This chapter is an introduction to the security of web application and it can be split in 2 different types of items.

The first type of items is what I would call “low-hanging fruits” or how you could improve the security  of your application with a very small effort:

  • The use of HTTP/S POST request method is advised over the use of HTTP/S GET. In the case of POST the parameters are embedded in the request body, so the parameters are not stored and visible in the browser history and if used over HTTPS are opaques to a possible attacker.
  • The use of the HTTP/S response headers:
    • Cache-Control – directive that instructs the browser how should cache the data.
    • Strict-Transport-Security – response header that force the browser to alway use the HTTPS protocol. This it can protect against protocol downgrade attacks and cookie hijacking.
    • X-Frame-Options – response header that can be used to indicate whether or not a browser should be allowed to render a page in a <frame>, <iframe> or <object> . Sites can use this to avoid clickjacking attacks, by ensuring that their content is not embedded into other sites.
    • X-XSS-Protection – response header that can help stop some XSS atacks (this is implemented and recognized only by Microsoft IE products).

 The second types of items are more complex topics like the input validation and security controls. For this items the authors just scratch the surface because all of this items will be treated in more details in the future chapters of the book.

Chapter 2: Authentication and Session Management

This chapter is about how a secure authentication feature should work; under the authentication topic is included the login process, session management, password storage and the identity federation.

The first part is presenting the general workflow of login and session management (see next picture) and for every step of the workflow  some dos and don’t are described.

login and session management workflow

login and session management workflow

The second part of the chapter is about common attacks on the authentication and for each kind of attack a solution to mitigated is also presented. This part of the chapter is strongly inspired from the OWASP Session Management Cheat Sheet which is rather normal because one of the authors (Jim Manico) is the project manager of the OWASP Cheat Sheet Series.

If you want to have a quick view of this chapter you can take a look to the presentation Authentication and Session Management done by Jim.

Even if you are not implementing an authentication framework for you application, you could still find good advices that can be applied to other web applications; like the use of the use of the secured and http-only attributes for cookies and the increase of the session ID length.

Chapter 3: Access Control

The chapter is about the advantages and pitfalls of implementing an authorization framework and can be split in three parts.

The first part describes the goal of an authorization framework and defines some core terms:

  • subject : the service making the request
  • subject attributes : the attributes that defines the service making the request.
  • group : basic organizational structure
  • role : a functional abstraction that uniquely describe system collaborators with similar or unique duties.
  • object : data being operating on.
  • object attributes : the attributes that defines the type of object being operating on.
  • access control rules : decision that need to be made to determine if a subject is allowed to access an object.
  • policy enforcement point : the place in code where the access control check is made.
  • policy decision point : the engine that takes the subject, subject attributes, object, object attributes and evaluates them to make an access control decision.
  • policy administration point : administrative entry in the access control system.

The second part of the chapter describes some access control (positive) patterns and anti-patterns.

Some of the (positive) access control patterns: have a centralized policy enforcement point  and policy decision point (not spread through the entire code),  all the authorization decisions should be taken on server-side only (never trust the client), the changes in the access control rules should be done dynamically (should not be necessary to recompile or restart/redeploy the application).

For the anti-patterns, some of then are just opposite of the (positive) patterns : hard-coded policy (opposite of “changes in the access control rules should be done dynamically”), adding the access control manually to every endpoint (opposite of have a centralized policy enforcement point  and policy decision point)

Others anti-patterns are around the idea of never trusting the client: do not use request data to make access control policy decisions and fail open (the control access framework should cope with wrong or missing parameters coming from the client).

The third part of the chapter is about different approaches (actually two) to implement an access control framework. The most used approach is RBAC (Role Based Access Control) and is implemented by some well knows Java access control frameworks like Apache Shiro and Spring Security. The most important limitation of RBAC is the difficulty of implementing data-specific/contextual access control. The use of ABAC (Attribute Based Access Control) paradigm can solve the data-specific/contextual access control but there are no mature frameworks on the market implementing this.

Chapter 4: Cross-Site Scripting Defense

This chapter is about the most common vulnerability found across the web and have two parts; the presentation of different types of cross-site scripting (XSS) and the way to defend against it.

XSS is a type of attack that consists in including untrusted data into the victim (web) browser. There are three types of XSS:

  • reflected XSS (non persistent) – the attacker tampers the HTTP request to submit malicious JavaScript code. Reflected attacks are delivered to victims via e-mail messages, or on some other web site. When a user clicks on a malicious link, submitting a specially crafted form the injected code travels to the vulnerable web site, which reflects the attack back to the user’s browser. The browser then executes the code because it came from a “trusted” server.
  • stored XSS (persistent XSS) – the malicious script is stored on the server hosting the vulnerable web application (usually in the database) and it is served later to other users of the web application when the users are loading the vulnerable page. In this case the victim does not require to take any attacker-initiated action.
  • DOM-based XSS – the attack payload is executed as a result of modifying the DOM “environment” in the victim’s browser.

For the defense techniques the big picture is that the input validation and output encoding should fix (almost) all the problems but very often various factors needs to be considered when deciding the defense technique.

Some projects are presented for the input validation (OWASP Java Encoder Project) and output encoding (OWASP HTML Sanitizer, OWSP AntiSamy).

Chapter 5: Cross-Site Request Forgery Defense and Clickjacking

Chapter 6: Protecting Sensitive Data

This chapter is articulated around three topics; how to protect (sensitive) data in transit, how to protect (sensitive) data at rest and the generation of secure random numbers.

How to protect the data in transit

The standard way to protect data in transit is by use of cryptographic protocol Transport Layer Security (TLS). In the case of web applications all the low level details are handled by the web server/application server and by the client browser but if you need a secure communications channel programmatically you can use the Java Secure Sockets Extension (JSSE). The authors recommendations for the cipher suites is to use the JSSE defaults.

Another topic treated by the authors is about the certificate and key management in Java. The notions of trustore and keystore are very well explained and examples about how to use the keytool tool are provided. Last but not least examples about how to manipulate the trustores and keystores programmatically are also provided.

How to protect data at rest

The goal is how to securely store the data but in a reversible way, so the data must be wrapped in protection when is stored and the protection must be unwrapped later when it is used.

For this kind of scenarios, the authors are focusing on Keyczar which is a (open source) framework created by Google Security Team having as goal to make it easier and safer the use cryptography for the developers. The developers should not be able to inadvertently expose key material, use weak key lengths or deprecated algorithms, or improperly use cryptographic modes.

Examples are provided about how to use Keyczar for encryption (symmetric and asymmetric) and for signing purposes.

 Generation of secure random numbers

Last topic of the chapter is about the Java support for the generation of secure random numbers like the optimal way of using the java.security.SecureRandom (knowing that the implementation depends on the underlying platform) and the new cryptographic features of Java8 (enhance of the revocation certificate checking, TLS Server name indication extension).

Chapter 7: SQL Injection and other injection attacks

This chapter is dedicated to the injections attacks; the sql injection being treated in more details that the other types of injection.

SQL injection

The sql injection mechanism and the usual defenses are very well explained. What is interesting is that the authors are proposing solutions to limit the impact of SQL injections when the “classical” solution of query parametrization cannot be applied (in the case of legacy applications for example): the use of input validation, the use of database permissions and the verification of the number of results.

Other types of injections

XML injection, JSON-Based injection and command injection are very briefly presented and the main takeaways are the following ones:

  • use a safe parser (like JSON.parse) when parsing untrusted JSON
  • when received untrusted XML, an XML schema should be applied to ensure proper XML structure.
  • when XML query language (XPath) is intermixed with untrusted data, query parametrization or encoding is necessary.

Chapter 8: Safe File Upload and File I/O

The chapter speaks about how to safety treat files coming from external sources and to protect against attacks like file path injection, null byte injection, quota overloaded Dos.

The main takeaways are the following ones: validate the filenames (reject filenames containing dangerous characters like “/” or “\”), setting a per-user upload quota, save the file to a non-accessible directory, create a filename reference map to link the actual file name to a machine generated name and use this generated file name.

Chapter 9: Logging, Error Handling and Intrusion Detection

Logging

What should be be logged: what happened, who did it, when it happened, what data have been modified, and what should not be logged: sensitive information like sessions IDs, personal informations.

Some logging frameworks for security are presented like OWASP ESAPI Logging and Logback. If you are interested in more details about the security logging you can check OWASP Logging Cheat Sheet.

Error Handling

On the error handling the main idea is to not leak to the external world stacktraces that could give valuable information about your application/infrastructure to an attacker. It is possible to prevent this by registering to the application level static pages for each type of error code or by exception type.

Intrusion Detection

The last part of the chapter is about techniques to help monitor end detect  and defend against different types of attacks. Besides the “craft yourself” solutions, the authors also re presenting the OWASP AppSensor application.

Chapter 10: Secure Software Development Lifecycle

The last chapter is about the SSDLC (Secure Software Development Life Cycle) and how the security could be included in each steps of development cycle. For me this chapter is not the best one but if you are interested about this topic I highly recommend the Software Security: Building Security in book (you can read my own review of the book here, here and here).