Soma: Your one-stop CTF problem management tool

• What is Soma?
  • For problem solvers
  • For problem setters
  • Dependency
• Current Status
  • Roadmap
• How to Use
  • Installation
  • Command overview
  • Adding repositories
  • Building problem images
  • Running problems
  • Fetching problem attachments
  • Stopping problems
  • Removing problem images
  • Removing repositories
  • Updating repositories
  • Notes on repository and problem names
    • Problem query
    • Name rules
• How to Add Soma Support to Your Repository
  • soma.toml syntax
    • The root section
      • The name field
      • The work_dir field (optional)
    • The [binary] section
      • The os field
      • The cmd field
      • File entries
        • The path field
        • The target_path field (optional)
        • The public field (optional)
    • Other subconfigurations
  • soma-list.toml syntax
    • The problems field
• Development
  • Prerequisites
  • Testing, Building, and Running
• License
  • Contribution

What is Soma?

Soma is a cross-platform CTF problem container manager.

• Soma helps problem authors to easily create and distribute reproducible CTF problem environment.
• Soma helps CTF players to easily download and run CTF problems on their local machine after contests.

For problem solvers

Downloading and running a problem is as easy as running three commands.

$ soma add https://github.com/PLUS-POSTECH/simple-bof.git
$ soma build simple-bof
$ soma run simple-bof 31337

CTF problems often contain public files. You can also fetch them easily with soma.

# this will copy public files to the current working directory
$ soma fetch simple-bof

For problem setters

Add soma.toml that describes your problem in your project's root directory. The config file below shows an example of it.

name = "simple-bof"

[binary]
os = "ubuntu:16.04"
cmd = "./simple-bof"

[[binary.executable]]
path = "build/simple-bof"
public = true

[[binary.readonly]]
path = "flag"

That's all! Soma gets enough information to run your binary from these 12 lines of configuration.

Soma will use reasonable default value for the other things not specified such as default working directory, file permissions, fork daemon, and standard stream buffering. Of course they can be manually configured if needed :)

If your project contains more than one problems, you can put soma-list.toml that lists each problem directory.

problems = [
    # these subdirectories contain soma.toml files
    "problem1",
    "sub-dir/problem2"
]

Dependency

Soma requires Docker to be installed on the system.

Current Status

Soma is in its alpha stage. Currently, it supports running a binary file under a socat fork server.

We hope to add more scenarios to it, notably a web problem setup which uses PHP with MySQL and a Python-based setup.

Issues related to 0.1.0 release are marked with 0.1.0 milestone.

Roadmap

• Better documentation of features. (priority: high)
• Support multiple containers for a single problem. (priority: low)
• Support cloud deployment such as AWS, GCP, Azure as well as local deployment. (priority: low)

How to Use

Installation

Use cargo install soma-ctf if you have Rust toolchain on your system. This command will download the latest released version from crates.io and build the executable file.

$ cargo install soma-ctf

Or, download the precompiled binary from the release page.

If you want to try the cutting-edge master branch, you can also build your own binary from the source. In detail, clone this git repository and run cargo install.

$ git clone https://github.com/PLUS-POSTECH/soma.git
$ cd soma
$ cargo install

Command overview

	Add / Create	Remove
Repository	add	remove
Image	build	clean
Container	run	stop

Additionally, update

Adding repositories

Soma repository has soma.toml or soma-list.toml in its top level directory and can contain one or more problems. To use Soma, start by adding problem repositories. We will use soma-bata-list as an example throughout this document.

You can add a repository with add subcommand:

$ soma add https://github.com/PLUS-POSTECH/soma-bata-list.git

add subcommand takes a repository source as an argument, which is https://github.com/PLUS-POSTECH/soma-bata-list.git in the command above. Soma supports the following repository sources:

• Git repository (only HTTPS without authentication is supported for now)

  e.g., https://github.com/PLUS-POSTECH/soma-bata-list.git

• Local file system directory

  e.g., /home/linux-user/soma-repo

By default, Soma will parse the name of the repository from the repository source string. For example, https://github.com/PLUS-POSTECH/soma-bata-list.git will return soma-bata-list and /home/linux-user/soma-repo will return soma-repo as a default repository name. If you want to use another name, you can use --name [NAME] flag. This flag will make Soma register the repository under the given name.

Also, note that there are a few requirements for repository names. See "Name rules" section for more details.

Building problem images

Soma uses Docker to manage problem images and containers. An image is a snapshot of a problem environment, and a container is an instance of an image. In order to run a problem, you should build the problem image first.

Soma will automatically generate Dockerfile from the problem manifest when you execute the build command. You can build a problem image by executing the following command:

$ soma build r0pbaby
# or
$ soma build soma-bata-list.r0pbaby

As you can see, there are two different ways to select a problem. See "Problem query" section for more details.

Running problems

When the problem image is ready, you can run the problem container! The problem container can be started with the following command:

$ soma run r0pbaby 13337
# or
$ soma run soma-bata-list.r0pbaby 13337

Here, 13337 indicates the port number which binds to the problem container. This port number will expose the problem to the host network. In this example, r0pbaby is accessible through your.host.address:13337. Try nc localhost 13337 on your machine to start solving the problem.

run command requires a port number for now, but we are planning to support automatic port binding in the future (see #64).

Fetching problem attachments

CTF problems often provide a few attachments (usually problem binaries). There is a dedicated subcommand to fetch these files to your current working directory:

$ soma fetch r0pbaby
# or
$ soma fetch soma-bata-list.r0pbaby

Stopping problems

After finish solving a problem, stop and remove the problem container by invoking:

$ soma stop r0pbaby
# or
$ soma stop soma-bata-list.r0pbaby

Removing problem images

You may want to remove existing problem images for several reasons (e.g., free disk space, remove repository). You can clean up existing images by:

$ soma clean r0pbaby
# or
$ soma clean soma-bata-list.r0pbaby

Before trying to remove the image, check if any associated container exists. Soma will reject the command if there is a running container from the image.

Removing repositories

If you want to remove a registered repository, use the following command:

$ soma remove soma-bata-list

There should be no problem image or container associated to the repository when you use this command. Use clean and stop command to remove them if necessary. Auto pruning for your convenience will be implemented in the future (see #115).

Updating repositories

You can update and sync repositories with update command:

$ soma update soma-bata-list

Note that problem containers that are already running are untouched by this command. You might want to stop, build, and run the problem again after updating a repository.

Notes on repository and problem names

Problem query

There are two ways to identify a problem. You can specify only the name of a problem (e.g., r0pbaby) or the full name of a problem containing what repository it is in (e.g., soma-bata-list.r0pbaby).

If the problem name is unique (i.e., the problem name is used only in a single repository), you can use the former method. Otherwise, you must use the latter or Soma will give you an error message that the problem name is found among multiple repositories.

Name rules

All repository and problem names should follow the docker name component rules with no . (i.e., ^[a-z0-9]+((?:_|__|[-]*)[a-z0-9]+)*$, see Docker regexp definitions for more details). This measure is to prevent Soma from behaving bad when malicious input is provided. We chose docker name component rules as repository and problem names are substrings of Docker image name. And 'no .' rule is added because Soma utilizes . as a name separator.

How to Add Soma Support to Your Repository

In order to support Soma, a repository should have soma.toml or soma-list.toml in its top level directory. soma-list.toml lists each subdirectory that contains a soma.toml file, and soma.toml is the name of Soma problem manifest file.

If your repository contains only one problem in its top level directory, soma.toml can be used directly without soma-list.toml.

soma.toml syntax

Each problem in a repository needs a manifest file, soma.toml, in its directory. The problem manifest file contains necessary information for Soma to manage problems. We will discuss the syntax of soma.toml section by section with this example.

name = "simple-bof"
work_dir = "/home/simple-bof"

[binary]
os = "ubuntu:16.04"
cmd = "./simple-bof"

[[binary.executable]]
path = "build/simple-bof"
public = true

[[binary.readonly]]
path = "flag"
target_path = "/you_cannot_guess_this_very_secret_flag_name"

The root section

Manifest root contains two metadata for the problem.

name = "simple-bof"
work_dir = "/home/simple-bof"

The name field

The name field of the root section defines the name of the problem. Soma will recognize this field (not the directory name) as the problem name.

The work_dir field (optional)

The work_dir field of the root section contains the path of the working directory inside the problem image. Default value for this field is the home directory of the user whose name is same with the name of the problem (for the example above, "/home/simple-bof").

The [binary] section

The [binary] section contains information required to use binary subconfiguration. Binary subconfiguration supports a scenario which runs an executable and pipes standard input and output through a TCP connection with a fork daemon; this is one of the most common setups in CTF competitions.

[binary]
os = "ubuntu:16.04"
cmd = "./simple-bof"

[[binary.executable]]
path = "build/simple-bof"
public = true

[[binary.readonly]]
path = "flag"
target_path = "/you_cannot_guess_this_very_secret_flag_name"

The os field

The os field indicates what OS flavor is used by the problem. This field is currently redirected into the parent image name of Dockerfile. However, it will only allow pre-selected choices in the future.

The cmd field

The cmd field defines how to run the problem binary. The specified binary will be executed through socat daemon.

File entries

[[binary.executable]], [[binary.readonly]] sections contain file entries of the subconfiguration.

[[binary.readwrite]], [[binary.with-permissions]], and [[binary.fetchonly]] are reserved for a future implementation (see #50 and #84).

The path field

The path field contains a relative path to the file from the problem directory. Supporting external sources such as URL is planned in the future (see #114).

The target_path field (optional)

The target_path field specifies where the file should be copied inside the problem image. This field defaults to work_dir in the root section.

The public field (optional)

File entries with public field set to true will be copied to the current working directory when users invoke fetch subcommand. This field has a default value of false.

Other subconfigurations

Other subconfigurations for common CTF setups such as apache-php7, python-uwsgi, or mysql are planned to be supported in a future release (see #50). Subconfiguration syntax is designed to support multi-configuration problem in the future, which will be handled similarly to Docker compose.

soma-list.toml syntax

The problems field

soma-list.toml contains a single field problems which is an array of relative paths to each problem directory.

problems = [
    # these subdirectories contain soma.toml files
    "simple-bof",
    "hard/complicated-bof"
]

Development

Prerequisites

• Install Rust stable toolchain.
• Install openssl (Required by openssl-sys crate).
• Install clippy and rustfmt.
  • rustup component add clippy rustfmt
• Copy files in hooks directory to .git/hooks.

Testing, Building, and Running

Soma is written with Rust and utilizes Cargo as a building and testing system.

You can test, build, and run with the following command.

$ cargo test
$ cargo build
$ cargo run

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT) at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be dual licensed as above, without any additional terms or conditions.