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Re: Static Code Analysis - Nuts and Bolts
From: "Debasis Mohanty" <debasis.mohanty.listmails () gmail com>
Date: Wed, 27 Jun 2007 23:23:05 +0530
What program(s) do you use in static code analysis? It doesn't matter if you are a hardcore grep+editor researcher or if you use complex frameworks: Tell me (and also the rest of the list) about it.
Secure code review is one of the most mis-guided field where many security folks talks only about grep'ing for threat patterns. Offcourse I do not rule out it as a starting point but there are lot more to it. I have my own approach to secure code review: A simpler and easy to go approach is - a) Build up a Taxonomy of security coding errors specific to various platforms The taxonomy of coding errors defined by Gary McGraw (cigital.com) in famous book "Software Security - Building Security In" is good starting point to base line with. There are several such taxonomies of coding errors floating around but most of them seems to be flawed in some or the other way. I found McGraw's classification for errors (i.e. security flaws) to be useful and can be made a part of both manual and automatic code review. A nice write up on various such taxonomies can be found here - http://securesoftware.blogspot.com/2005/12/threat-vulnerabilities-classification.html Moving further you can refer CWE (http://cwe.mitre.org/data/dictionary.html) which presently seems to be superset of all common software weaknesses. b) Create a set of secure coding anti-patterns specific to various platforms Secure coding anti-patterns are commonly used poor solutions to common security problems. This comes handy in getting more accurate results when you run the anti-pattern cheat sheet through the code. For Example: * Use of an unbounded copy char buf[1024]; strcpy(buf, s); * Use of a bounded copy with incorrect calculations char buf[1024]; strncpy(buf, s, 1025); Both the above piece of code snippet is vulnerable. One more example is - not always a check for NULL value will take care of a NP (Null Pointer) dereference bug. i.e. there are many weak ways of preventing NP errors which doesn't warrant a *hard to break* protection. check out https://www.blackhat.com/presentations/win-usa-03/bh-win-03-schoenfeld.pdf http://developers.sun.com/learning/javaoneonline/j1sessn.jsp?sessn=TS-2594&yr=2007&track=5 google for secure coding antipatterns to find more references. c) Grep for anti-patterns or secure coding mistakes Use you favorite editor here and grep for all security anti-patterns. I am a great fan of SciTE which supports almost all languages. get it here http://scintilla.sourceforge.net/ Though this is an important phase during code review but definitely not an ultimate phase to find security holes. The important phase is what comes next i.e. Manual Data Flow (DF) and Control Flow (CF) analysis. d) Manual Data Flow (DF) and Control Flow (CF) analysis DF analysis - http://en.wikipedia.org/wiki/Data_flow_analysis CF analysis - http://en.wikipedia.org/wiki/Control_flow_graph Performing both DF and CF analysis manually takes lot of time but is definitely most important part of code review. It helps identifying accurate threats from security standpoint. This phase requires a master code security ninja's hand to ensure actual issues are captured. For example: Not always you see request.getparameter (" ") in java can be flagged for a potential XSS vector. In other words it is necessary to check - whether the data can be directly or indirectly be tampered by an malicious user at any given point of time to cause a successfull XSS attack - check whether the data is sanitised for malicious inputs before it is directly written to user page. - check whether the data is encoded before written back to user page similarly there are lot of such factors based on which a code reviewer will be able to decide whether the finding is actually a threat or not. Few code review optimization tricks - - know languages like python or ruby so that you can write some scripts to automate step "c" and "d". - Every time you find unique anti-patterns do update your anti-pattern cheat sheet - For easiness decompose a big application into various modules for code review. - Prioritize the security anti-patterns based on your own skills to identify them faster and accurately. For example, I am fast at finding XSS anti-patterns compared to NP exceptions. So I'll push NP anti-patterns towards the end. - If at any point of time, a particular issue is taking more time to investigate then tag it for future review and move on to next. Thats all I have for now.... hope it helps. -d On 6/22/07, Paul Sebastian Ziegler <psz () observed de> wrote:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi list, due to personal interest I'd like to ask on your opinion regarding best practices for static code analysis. I guess most of us are accustomed to this method. After all - if you want to find a vulnerability that basically means that either luck, fuzzing or statical analysis will have something to do in the process. Now statical analysis of many languages can be quite fun. Take PHP and Python for example. You can mostly read the code like a book and mark down interesting passages to further analyze later on. Grep and a good editor are about all we need. However other languages often tend to become really nasty. Let's say we want to analyze a 2MB C-source split up into several thousand files. "cat * | grep strcpy" will most probably return about a hundred results. I just did a lot of static analysis lately and sometimes it took me more than half an hour to trace back _one_ of the strcpy()-calls and check if the copied bits could be controlled in some way. Of course not every dangerous call takes this long to check (also I might be a little slow), however I think that you all know what I'm talking about here. So after not having slept for about a week I started to search for tools to ease working on my projects. (Yes, I did drop my plans of auditing 2MB C-sources using only vim and grep...) Now this is where I'd like to open up an exchange on best practices and tool-combinations. What program(s) do you use in static code analysis? It doesn't matter if you are a hardcore grep+editor researcher or if you use complex frameworks: Tell me (and also the rest of the list) about it. I took a quick look at flawfinder and rats. However they do nothing that grep couldn't accomplish as well. For browsing the code and finding references to functions or declarations of variables I am currently using redhat's source-navigator. It is by no means perfect and has been unmaintained for a while - however it is still a great help. That is just my two cents. Any remarks/hints/ideas/concepts/nuts would be greatly appreciated by me as well as a lot of other people interested in the matter. (At least I hope so.) So please share your knowledge. Many Greetings Paul -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGe/BlaHrXRd80sY8RCgUSAJ9Y9+LCr4hZ1vs6gOrZHa6O9Wv91wCgypM9 1fxdotQfIdgcpXJg9RAP0xs= =ni/j -----END PGP SIGNATURE----- _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
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Current thread:
- Static Code Analysis - Nuts and Bolts Paul Sebastian Ziegler (Jun 22)
- Re: Static Code Analysis - Nuts and Bolts Debasis Mohanty (Jun 27)
- Re: Static Code Analysis - Nuts and Bolts Dave Hull (Jun 27)
- Re: Static Code Analysis - Nuts and Bolts Debasis Mohanty (Jun 27)