Homework Assignment #4 — Defect Detection

In this assignment you will use two different static analysis tools to automatically detect potential defects.

The first static analysis tool is GrammaTech's CodeSonar, which focuses on security issues, as well as memory, resource and concurrency defects. CodeSonar is a commercial tool used in activities such as DO-178B avionics certification; we have obtained an academic license for its use in this class.

The second static analysis tool is Facebook's Infer, which focuses on memory errors, leaks, race conditions, and API issues. Infer is open source.

Installing, Compiling, Running and Analyzing Legacy Code

It is your responsibility to download, compile, run and analyze the subject program and associated tools (or use the precompiled one). Getting the code and tools to work in some manner is part of the assignment. You can post on the forum for help and compare notes bemoaning various architectures (e.g., windows vs. mac vs. linux, etc.). Ultimately, however, it is your responsibility to read the documentation for these programs and tools and use some elbow grease to make them work.

The lighttpd webserver

We will make use of the lighttpd webserver (pronounced "lighty"), version 1.4.17, as our primary subject program for this homework. A local mirror copy of lighttpd-1.4.17.tar.gz is available, but you can also get it from the original website. It is about 55,000 lines of code in about 90 files. While somewhat small for this class, some analysis tool licenses have LOC limits or scalability issues, so it was chosen as an indicative compromise.

While not as large or popular as apache, at various points lighttpd has been used by YouTube, xkcd and Wikimedia. Much like apache, old verisons of it have a number of known security vulnerabilities.

The Common Vulnerabilities and Exposures system is one approach for tracking security vulnerabilities. A CVE is basically a formal description, prepared by security experts, of a software bug that has security implications.

There are ten CVEs associated with lighttpd 1.4.17. For example, CVE-2014-2324 has the description "Multiple directory traversal vulnerabilities in (1) mod_evhost and (2) mod_simple_vhost in lighttpd before 1.4.35 allow remote attackers to read arbitrary files via a .. (dot dot) in the host name, related to request_check_hostname." You can dig into the information listed in, or linked from, a CVE (or just look at subsequent versions of the program where the bug is fixed!) to track down details. Continuing the above example, mod_evhost refers to source file mod_evhost.c, mod_simple_vhost refers to file mod_simple_vhost.c, and request_check_hostname is in file request.c. You will need such information when evaluating the whether or not the tools find these security bugs.

Facebook's Infer

The Infer tool is a static analyzer — it detects bugs in programs without running them. The primary website is fbinfer.com.

Unfortunately, some versions of Infer can be obnoxious to build and install, despite their handy installation guide. Also, many users report that Infer does not run on Windows Subsystem for Linux (WSL) or similar setups; a headless Virtual Box configuration (instructions) is recommended.

As a conveience only (see above about "your responsibility"), a pre-compiled, runs-for-me-but-no-promises-for-you (Ubuntu 16.04.2 LTS GNU/Linux 4.4.0-34-generic x86_64) version of Infer is available locally here (warning: 265 MB). The main binary can be found at infer-linux64-v0.13.0/infer/bin/infer. You can use either the pre-compiled one or compile it yourself for full credit.

infer on lighttpd Details

$ cd lighttpd-1.4.17 
$ sh configure
$ /path/to/infer/bin/infer run -- make 

make[1]: Leaving directory '/home/weimer/src/lighttpd-1.4.17'
Found 88 source files to analyze in /home/weimer/src/lighttpd-1.4.17/infer-out
Starting analysis...

legend:
  "F" analyzing a file
  "." analyzing a procedure

FFFFFFFFFF.....F...FF....F..FF.F..F....................................................................................FF.................................................F...........F..................F..................F...........................................................................F....................................................................F........................................................F.......F.................F...............F.......FF.............F...................F.............F.........F...F.................F...................................F............FF.F.....F.......................F.....FF..............F..F........FF..........FF.............FF.......FF.F....F......F......FFF..............F.........F...F......F...........F.......FF..........F.F...........F...F..F.......F..F...F........................F..F.........F....F........F.....F..F..........F............F....F...................F................................................................................................................................................

Found 308 issues

src/joblist.c:19: error: NULL_DEREFERENCE
  pointer `srv->joblist->ptr` last assigned on line 16 could be null and is dereferenced at line 19, column 2.
  17.           }
  18.
  19. >         srv->joblist->ptr[srv->joblist->used++] = con;
  20.
  21.           return 0;

	...

Summary of the reports

      NULL_DEREFERENCE: 145
            DEAD_STORE: 94
           MEMORY_LEAK: 65
         RESOURCE_LEAK: 3
  QUANDARY_TAINT_ERROR: 1

infer on jfreechart Details

$ cd jfreechart-1.5.0-1.4.17 
$ /path/to/infer/bin/infer run -- mvn compile
Capturing in maven mode...
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building JFreeChart 1.5.0

	...

Found 640 source files to analyze in /home/weimer/src/jfreechart-1.5.0/infer-out
Starting analysis...

	...

Found 69 issues

src/main/java/org/jfree/data/xml/DatasetReader.java:73: error: RESOURCE_LEAK
  resource of type `java.io.FileInputStream` acquired to `in` by call to `FileInputStream(...)` at line 72 is not released after line 73.
  71.           throws IOException {
  72.           InputStream in = new FileInputStream(file);
  73. >         return readPieDatasetFromXML(in);
  74.       }

...

Summary of the reports

  THREAD_SAFETY_VIOLATION: 43
         NULL_DEREFERENCE: 22
            RESOURCE_LEAK: 4

While times will vary, some students have reported that running Infer on jfreechart can take five hours.

GrammaTech's CodeSonar

GrammaTech's CodeSonar static analyzer is a commercial (not open source) tool for finding defects in program source code or binaries.

GrammaTech has generously provided an academic license so that students in this class can make use of their tool on a limited basis. This license includes a lines-of-code limit, so we have pre-run the analysis and made the results available for everyone to share (running it is very similar to Infer, see below). Analyzing additional code or trying to subvert this license runs the risk of ruining our relationship with that company and thus preventing me from giving future students this experience in subsequent semesters — doing so is thus a significant academic integrity violation.

CodeSonar's output is designed to be shared among an organization's developers. As a result, the analysis is carried out once and then the reports are made available to everyone via a web interface. In this model the team might work together to triage and prioritize the defect reports, assigning some to one developer and some to another. We have already run CodeSonar for you; all students share the analysis results.

Running CodeSonar is as simple as running Infer — basically, instead of running make one runs codesonar make. The actual commands are listed below, but you do not run them (we have already run them for you):

$ cd lighttpd-1.4.17 
$ sh configure 
$ # DO NOT: codesonar analyze lighttpd-1.4.17 host:port make   

Similarly, a Java project would be analyzed by (do not run this):

$ cd jfreechart-1.5.0/
$ mvn compile
$ # DO NOT: codesonar analyze jfreechart-1.5.0 host:port cs-java-scan src/main/java/     

GrammaTech's CodeSonar — Report Locations

FAQ: Secure Connection Problem

If you receive a warning message like this:

Use one of these solutions to resolve it:

1. Carefully retype the URL so that it says http instead of https — remove the "s"!
2. Use Chrome instead of another browser like Firefox.

The CodeSonar reports can be found at this location — but you must connect with a VPN or be on campus!. If you are registered with the course (e.g., via Wolverine Access), click "Forgot Password", enter your UM username, and click the Send Email button. Login information will be emailed to your @umich.edu address.

For example, your instructor would enter weimerw (note: no @ or numbers typed in this form field) to have an email with a set-your-password login code sent to weimerw@umich.edu.

(The license agreement places certain restrictions on who can use or see the service.)

Additional Subject Programs

We also make available the CodeSonar analyses of "fan favorites" such as:

• cpython-2.7.5 — Python interpreter
• curl-7.55.0 — data transfer tool
• fastjson-1.2.60 — JSON parser/generator for Java
• jsoup-1.11.2 — Java HTML parser
• libpng-1.6.34 — portable network graphics library

Note that the report requires you to choose an additional program (such as one of the four listed above) and analyze it.

FAQ and Troubleshooting

In this section we detail previous student issues and resolutions:

1. Question: When I run infer.exe run -- make or infer run -- mvn compile I get errors like InferModules__SqliteUtils.Error or Maven command failed.

   Answer: The most common issue is that Infer does not always run well on Windows Subsystem for Linux (WSL) or similar shortcuts to get a Linux- or Ubuntu-like interface on another OS. We strongly recommend a headless Virtual Box setup (instructions).

2. Question: When I try to run Infer, I get cannot execute binary file: Exec format error..

   Answer: One student reports: "Finally got it. Turns out I was using a 32 bit processor (i386) so even when I set up my vm as 64 bit, it couldn’t run any x86-64 binaries. Fixed it by installing a 64 bit vdi. https://appuals.com/fix-cannot-execute-binary-file-exec-format-error-ubuntu/

3. Question: I see Maven command failed: *** mvn compile -P infer-capture when I try to run Infer.

   Answer: Some students have seen success with:

   sudo apt-get install cobertura maven
   sudo apt-get install openjdk-8-jdk
   

   Others reported that "I ended up having to setup an Ubuntu 16.04 VM in VirtualBox".

4. Question: I see zero active warnings when I look at CodeSonar.

   Answer: When more than five users are logged in anonymously, CodeSonar allows you to navigate but not to view any warnings (this is likely a security feature). You can resolve this issue by logging on using the directions above (which involves having CodeSonar mail you a password). You should see 2,082 warnings for cpython, for example.

Written Report

You must write a detailed PDF report reflecting on your experiences with these static analysis defect detection tools. In particular, all of the following are required:

• [Framing] Choose either "large software development organization" (e.g., the SQL Server group at Microsoft) or "small software development organization" (e.g., a dozen-person mobile app tech startup) — indicate your choice. You have been asked by your supervisor to evaluate these two tools and prepare a recommendation: which one, if any, should our organization use?
• [Setup] In a few sentences, describe your setup experiences with each applicable tool. This might include dependencies, installing it, runtime, etc.
  [1 point for description]
• [Usability] In a few sentences, compare and contrast your usability experiences with each tool. This might include locating the reports, navigating the report or documentation website, etc.
  [1 point for infer, 1 point for codesonar, 1 point for contrast, 1 point for other details]
• [Overall] Compare and contrast the quality and details of the reports generated by Infer and CodeSonar. At a high level, what did each tool do well? How might each tool be improved? Comment on defect report categorizations (e.g., Reliability, NULL_DEREFERENCE, Security, etc.). Did you observe any "duplicate" defect reports (i.e., the same underlying issue was reported in terms of multiple different symptoms) within the same tool? How much overlap did you observe between the issues reported by the two tools? What are the costs (in general) associated with each tool?
  [4 points for infer, 4 points for codesonar, 1 point for categories, 1 point for duplicates, 1 point for overlap, 2 points for costs]
• [CVE] Choose two of the CVEs associated with lighttpd. For each tool, describe whether or not that tool reported the issue associated with the CVE (or would otherwise have pointed you to it). You should choose one CVE such that at least one tool points out the CVE in some manner (if you find one); then, separately, you should choose one CVE such that at least one tool misses the CVE in some manner (if you find one). Overall, how effective are these tools at finding security defects?
  [2 point for each cve/tool pairing, 1 point for conclusion]
• [lighttpd] Compare and contrast the defect reports produced by the tools for the lighttpd program. Which did you find more useful? Consider false positives, false negatives, and issues that you would consider to have high priority or severity. Include (copy-and-paste, screenshot, etc.) part of one report you found particularly noteworthy (good, bad, complex: your choice) and explain it.
  [3 point for compare/contrast, 1 point for inlined report and analysis, 2 point for other insights]
• [jfreechart] Compare and contrast the defect reports produced by the tools for the jfreechart program. (6 points, as above.)
• [additional] Choose an additional subject program. Compare and contrast the defect reports produced by the tools for that program. (6 points, as above.)
• [Conclusion] Conclude your report with an overall recommendation for your supervisor. Identify three important metrics or evaluation criteria and make your recommendation based on them.
  [1 point for clear statement of recommendation, 1 point for clear definition of criteria, 4 points for logical support]

The grading staff will select a small number of excerpts from particularly high-quality or instructive reports and share them with the class. If your report is selected you will receive extra credit.

Submission

Submit a single PDF report via Gradescope. You must include your name and UM email id (as well as your partner's name and email id, if applicable).

There is no explicit format (e.g., for headings or citations) required. For example, you may either use an essay structure or a point-by-point list of question answers.