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WasmA: A Static Analysis Framework for WebAssembly

WasmA is a framework to create static analyses for WebAssembly binaries. Additionally, WasmA provides several standard analyses.

Provided Standrad Analyses

  • CallGraph: Generates a call graph for a given binary and saves it as a dot file.
  • ControlFlowGraph: Generates a control-flow graph for a given binary and saves it as a dot file.
  • DataFlowGraph: Generates a data-flow graph for a given binary and saves it as a dot file.
  • Data: Reads the data section of a binary and saves it as a csv file.
  • Disassembly: Outputs a disassembly of a binary's function that can be specified by its function index.
  • Exports: Outputs the exports of a given binary.
  • Imports: Outputs the imports of a given binary.
  • InstructionCount: Counts the occurrence of instructions and saves the results as txt file.
  • OverapproximationBrTable: Determines the overapproximation for br_table instructions and saves the results as csv file.
  • OverapproximationCallIndirect: Determines the overapproximation for call_indirect instructions and saves the results as csv file.
  • SectionDetails: Saves the details of a binary's sections to a txt file.
  • SectionList: Saves a list of a binary's sections to a txt file.

Installing WasmA

There are two options to use the WasmA framework. The first one is to use the framework as a local installation and the second one is to use WasmA inside a docker container.

Local Installation

The local installation has the following dependencies:

Installation

  1. Install dependencies

  2. Clone this repository

  3. Change into the wasma directory of the cloned repository

  4. Execute the following command to build the standard analyses:

    make build

Running WasmA as Docker Container

Dependencies:

Installation

  1. Install dependencies

  2. Clone this repository

  3. Change into the wasma directory of the cloned repository

  4. Execute the following command to build the docker image and container:

    ./docker-build.sh

The build script creates four directories:

  • $HOME/wasma: Working directory.
  • $HOME/wasma/data: This directory can be used to provide data that should be analyzed.
  • $HOME/wasma/bin: This directory is intended as import and export directory for the docker container. New created analyses can be exported to the local host using the script docker-save-app.sh. The analysis applications are exported to this directory $HOME/wasma/bin. The script docker-load-app.sh allows to load an existing analysis application into the docker container.
  • $HOME/wasma/analyses: This directory can be used to export and import source code for analyses by using the scripts docker-save-analysis.sh and docker-load-analysis.sh.

Using WasmA

Local

Provided Standard Analyses

After the local installation the standard analyses in the directory /bin can be used immediately. A list of all provided standard analyses can be found here. A description of the standard analyses' parameters can be found here.

Creating a New Analysis

A new analysis can be created by using the two go packages wasma and wasmp. For an easy start use the following template for your analysis:

package main

import (
    "fmt"
    "log"
    "path/filepath"
    "strings"
    "wasma/pkg/wasma"
    "wasma/pkg/wasma/graphs"
    "wasma/pkg/wasmp/modules"
)

type NEWANALYSIS struct{}

func (nEWANALYSIS *NEWANALYSIS) Analyze(module *modules.Module, args map[string]string) {
    // add code
}

func (nEWANALYSIS *NEWANALYSIS) Name() string {
    return "NEWANALYSIS"
}

func main() {
    analysis := wasma.NewWasmA()
    analysis.Start(&NEWANALYSIS{})
}

The first step for a new analysis is to define a new empty struct. This struct has to implement the two functions Analyze and Name. The function Analyze includes the analysis code and the function Name returns the name of the analysis.

Every analysis needs a main function. In this main function the wasma framework has to be instantiated by:

analysis := wasma.NewWasmA()

The analysis is started by passing an instance of the previously defined struct to the Start function:

analysis.Start(&NEWANALYSIS{})

The new analysis then can be compiled to an executable application with:

go build -o <output file> <source file>

Docker

To start and use the docker container enter the following commands:

docker start wasma
docker exec -it wasma sh

Using standard analyses

To list all provided standard analyses enter:

list.sh

Create your own analysis application

To create a new analysis enter:

create.sh <ANALYSIS NAME>

Parameter of a WasmA Analysis

Every analysis that has been created using WasmA has the following parameters:

  • -file: Specifies a binary file that should be analyzed.
  • -files: Specifies a txt file with a list of binary files that should be analyzed.
  • -out: Specifies an output directory for the analysis results.
  • -fi: Specifies the function index to select a specific function for an analysis.
  • -log: Specifies the location for the log file.
  • -ic: Flag to specify if indirect calls should be considered.
  • -con: Path to config file.
  • -cdfg: Compute the complete DFG if the parameter is true.