Frameshifter

Frameshifter is a grammar-based HTTP/2 fuzzer with mutation ability. This tool was developed for a research paper (titled "FRAMESHIFTER : Security Implications of HTTP/2-to-HTTP/1 Conversion Anomalies") published at USENIX Security 2022.

Getting Started (using docker)

If you run the commands shown below in the given order, you will have a running container where the Frameshifter is installed and a file (i.e., /tmp/output) which contains a couple of mutated HTTP/2 inputs created by the tool. Please, note that the fourth and fifth commands are supposed to be run in the opened container shell.

git clone https://github.com/bahruzjabiyev/frameshifter && cd frameshifter (cloning the repo)
docker build -t tool/frameshifter . (building the tool image)
docker run -ti tool/frameshifter bash (running a container)
source scapyenv/bin/activate (switching to the virtual environment where the libraries are installed)
seq 1 5 > /tmp/seeds; python3 /src/main.py -i -t -c /conf/simple_conf -f /tmp/seeds -o /tmp/output; jq '.' /tmp/output

About

A user-specified configuration file (see an example here) tells Frameshifter how to generate and mutate HTTP/2 inputs and where to deliver them. To generate inputs, Frameshifter uses an input grammar (see config.grammar here). Once the input is generated, a number (which is decided by the configuration) of mutations are applied. Mutations can be two types: content and sequence. The configuration decides (see config.symbol_mutation_types) what type of mutation can be applied on what input component. Both content and sequence mutations have their mutators defined in the configuration (see config.string_mutators and config.tree_mutators). Mutators which add or replace, uses a pool to pick the new element to add or to replace with (see config.char_pool and config.char_pool). Finally, the configuration also lists the target addresses.

Example

Let's remember how we ran the tool and created /tmp/output.

seq 1 5 > /tmp/seeds; python3 /src/main.py -i -t -c /conf/simple_conf -f /tmp/seeds -o /tmp/output; jq '.' /tmp/output

First, /tmp/seeds file is created containing numbers from 1 to 5. This file is fed as an input to the tool with the -f option and the tool uses each of these numbers as a seed to create and mutate an input. The -t option put the tool in the testing mode and instructs the tool not to deliver the inputs. Finally, the -o option specifies where to save the inputs for us to look at. Let's start from the seed number 1 (i.e., jq '.["seeds"]["1"]' /tmp/output).

As shown below, three pieces of information is retained for each seed: 1) the generated input, 2) the mutations applied and 3) responses returned by the targets. In this example, we have a WINDOW_UPDATE frame inserted after the HEADERS frame and two character modifications of the :method header (i.e., POST becomes ]ST). To see all the supported frame types, please take a look at here.

Testing

To run the tests, take the steps 1-4 given in the Getting Started section (see above). Then run the command below:

cd /src/tests; python3 test_main.py

Limitations

The naming of symbols in the grammar needs to follow some rules which are listed below. To be safe from the naming issues, it is recommended to follow the examples of here which is extensive enough.

Symbols representing the frames should have a name starting with <frame-type>-frame (e.g., headers-frame).
The names of symbols which represent individual frame fields should end with specific words (e.g., flags, stream_id).
The names of symbols which represent header names and values should end with header-name and header-value respectively.

License

Frameshifter is licensed under MIT license.