CogniCrypt_SAST: CrySL-to-Static Analysis Compiler
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README.md

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CogniCrypt_SAST

This repository contains CogniCrypt_SAST, the static analysis component for CogniCrypt. The static analysis CogniCrypt_SAST takes rules written in the specification language CrySL as input, and performs a static analysis based on the specification of the rules. CrySL is a domain-specific language (DSL) designed to encode usage specifications for cryptographic libaries (the JCA in particular). More information on CrySL and the static analysis is found in this paper.

Releases

You can checkout a pre-compiled version of CogniCrypt_SAST here.

Download the two files:

  • CryptoAnalysis-1.0.0-jar-with-dependencies.jar
  • JCA-CrySL-rules.zip

Checkout and Build

CogniCrypt_SAST uses maven as build tool. You can compile and build this project via

mvn package -DskipTests=true.

A packaged jar artifact including all dependency is found in CryptoAnalysis/build/CryptoAnalysis-1.0.0-jar-with-dependencies.jar

Usage

CogniCrypt_SAST can be started in headless mode (i.e., detached from Eclipse) via the class crypto.HeadlessCryptoScanner. It requires two arguments:

  • The absolute path to the directory of the CrySL (binary) rule files contained in JCA-CrySL-rules.zip. This CrySL rule set contains specification for the JCA. The source code for the rules is found here.
  • The absolute path of the application to be analyzed (.jar file or the root compilation output folder which contains the .class files in subdirectories)
java -cp CryptoAnalysis/build/CryptoAnalysis-1.0.0-jar-with-dependencies.jar crypto.HeadlessCryptoScanner \
      --rulesDir=<absolute-path-to-crysl-rules> \
      --applicationCp=<absolute-application-path>

For an easy start we prepared a .jar containing classes with crypto misuses. The source code for these misuses is found here. To run CogniCrypt_SAST on these classes, simply execute the following command (on a linux based system).

java -cp CryptoAnalysis/build/CryptoAnalysis-1.0.0-jar-with-dependencies.jar crypto.HeadlessCryptoScanner \
  --rulesDir=$(pwd)/CryptoAnalysis/src/test/resources/ \
  --applicationCp=$(pwd)/CryptoAnalysisTargets/CogniCryptDemoExample/Examples.jar

Note, depending on the analyzed application, the analysis may require a lot of memory and a large stack size. Remember to set the necessary heap size (e.g. -Xmx8g) and stack size (e.g. -Xss60m).

Report and Error Types

In the standard option, CogniCrypt_SAST outputs a report to the console. CogniCrypt_SAST reporst misuses when the code is not compliant with the CrySL rules. For each misuse CogniCrypt_SAST reports the class and the method the misuse is contained in. There are multiple misuse types:

  • ConstraintError: A constraint of a CrySL rule is violated, e.g., a key is generated with the wrong key size.

  • NeverTypeOfError: Reported when a value was found to be of a certain reference type: For example, a character array containing a password should never be converted from a String. (see KeyStore rule here).

  • ForbiddenMethodError: A method that is forbidden (CrySL block FORBIDDEN) to be called under some circumstances was found.

  • ImpreciseValueExtractionError: The static analysis was not able to extract all information required within the CrySL CONSTRAINT block. For example the key size could be supplied as a value listed in a configuration file. The static analysis does not model the file's content and may not constraint on the value.

  • TypestateError: The ORDER block of CrySL is violated, i.e., the expected method sequence call to be made is incorrect. For example, a Signature object expects a call to initSign(key) prior to update(data).

  • RequiredPredicateError: An object A expects an object B to have been used correctly (CrySL blocks REQUIRES and ENSURES). For example a Cipher object requires a SecretKey object to be correctly and securely generated.

  • IncompleteOperationError: The usage of an object may be incomplete: For example a Cipherobject may be initialized but never used for en- or decryption, this may render the code dead. This error heavily depends on the computed call graph (CHA by default)

When the option --reportDir=<folder> is chosen, CogniCrypt_SAST writes the report to the file CogniCrypt-Report.txt and additionally outputs the .jimple files of the classes where misuses where found in. Jimple is an intermediate representation close to the syntax of Java.

Visualization

When the --reportDir options is set, using the flag --visualization outputs visualizations for the data-flows. In the subfolder viz of the reportDir Json files will be generated for each individual analyzed object. Download the folder visualization from the WPDS project, open the index.html in some browser (tested on Chrome) and drop any of the Json files in the lower right corner. This allows you to browse the generated data-flow graphs as shown below:

Visualization

Changing the CrySL Rules

The current version of the tool takes CrySL rules in their binary formats (cryptslbin). When you want to adopt the rules please use the Eclipse plugin CogniCrypt. CogniCrypt ships with a CrySL editor to modify the rules, upon changes to the rules the editor produces the cryptslbin files. We plan to change CogniCrypt_SAST to take CrySL rules in source code format in the future.

CogniCrypt_SAST for Android Applications

CogniCrypt_SAST can also be run on Android Applications, checkout the repository here.

Contact

If you have any questions regarding this project, feel free to contact Johannes Spaeth.