MozillaSecurity / Dharma

Generation-based, context-free grammar fuzzer.

Table of Contents

• Run
  • pip
  • pipenv
  • package
  • Docker
• Examples
• Development
• Dharma Grammar Cheatsheet
• API Documentation
• Dharma in the Public

Run

All roads lead to Rome but Python 3.x is the prefered vehicle.

pip

pip install dharma
dharma --help

pipenv

pipenv install --dev
pipenv run dharma --help

package

python -m dharma --help

Docker

docker build -t dharma .
docker run --rm -it dharma -grammars dharma/grammars/canvas2d.dg

Examples

Generate a single test-case and print it to stdout. Multiple grammars can be appended to the -grammars argument.

dharma -grammars dharma/grammars/canvas2d.dg

Generating multiple test-cases and save the result to disk.

dharma -grammars dharma/grammars/canvas2d.dg -storage . -count 5

Generate test-cases and serve them in a template via WebSocket. Launch dharma/grammars/var/index.html in the browser after Dharma launched.

dharma -grammars dharma/grammars/canvas2d.dg -server -template dharma/grammars/var/templates/html5/default.html

Benchmark the generator.

time dharma -grammars dharma/grammars/canvas2d.dg -count 10000 > /dev/null

Development

PyLint

In case you run PyLint 1.9.2 and Python 3.7 you need to upgrade PyLint.

pip3 install pylint astroid --pre -U

Dharma Grammar Cheatsheet

Comments

%%% comment

Controls

%const% name := value

Sections

%section% := value
%section% := variable
%section% := variance

Extension Methods

Refer to extensions.py in dharma/core/ and to the xref_registry in the DharmaMachine class to add further extensions.

%range%(0-9)
%range%(0.0-9.0)
%range%(a-z)
%range%(!-~)
%range%(0x100-0x200)

%repeat%(+variable+)
%repeat%(+variable+, ", ")

%uri%(path)
%uri%(lookup_key)

%block%(path)

%choice%(foo, "bar", 1)

Assigning Values

digit :=
    %range%(0-9)

sign :=
    +
    -

value :=
    +sign+%repeat%(+digit+)

Using Values

+value+

Assigning Variables

variable :=
    @[email protected] = new Foo();

Using Variables

value :=
    !variable!.bar();

Referencing values from common.dg

value :=
    attribute=+common:number+

Calling JavaScript library methods

foo :=
    Random.pick([0,1]);

API Documentation

• https://mozillasecurity.github.io/dharma

Dharma in the Public

Dharma mentionings in the news.

• https://webassembly-security.com/fuzzing-wasm-javascript-dharma-chrome-v8/
• https://www.zerodayinitiative.com/blog/2019/1/31/implementing-fuzz-logics-with-dharma
• http://blog.ret2.io/2018/06/13/pwn2own-2018-vulnerability-discovery/
• https://blog.mozilla.org/security/2015/06/29/dharma/
• https://www.redpacketsecurity.com/dharma-generation-based-context-free-grammar-fuzzing-tool/