crowdsec-bouncer-traefik-plugin/examples/captcha

Example

Enabling catpcha response from crowdsec

Crowdsec support 3 remediations solutions ban, captcha, and throttle.
This plugins support the ban and captcha remediation.

Traefik configuration

The minimal configuration is defined below.
For now 3 captcha providers are supported:

• hcaptcha
• recaptcha
• turnstile

  labels:
      # Choose captcha provider
      - "traefik.http.middlewares.crowdsec.plugin.bouncer.captchaProvider=hcaptcha"
      # Define captcha site key
      - "traefik.http.middlewares.crowdsec.plugin.bouncer.captchaSiteKey=FIXME"
      # Define captcha secret key
      - "traefik.http.middlewares.crowdsec.plugin.bouncer.captchaSecretKey=FIXME"
      # Define captcha grade period seconds
      - "traefik.http.middlewares.crowdsec.plugin.bouncer.captchaGracePeriodSeconds=1800"
      # Define captcha HTML file path
      - "traefik.http.middlewares.crowdsec.plugin.bouncer.captchaHTMLFilePath=/captcha.html"

The captcha HTML file must be present in the Traefik container (bind mounted or added during a custom build).
It is not directly accessible from Traefik even when importing the plugin, so download it locally to expose it to Traefik.

  ...
  traefik:
    image: "traefik:v2.11.0"
    volumes:
      - './captcha.html:/captcha.html'
  ...

Crowdsec configuration

Crowdsec by default will take the ban action on suspicious activity detected in logs.
To instruct Crowdsec to use captcha remediation, change the /etc/crowdsec/profiles.yaml.

2 modes are supported:

• Always return a captcha decision
• Return a captcha decision the first X times and then a ban decision.

The second mode could be used to prevent repeated malicious activity. More information is available on configuring Crowdsec in the official documentation.

  ...
  crowdsec:
    image: crowdsecurity/crowdsec:v1.6.0
    volumes:
      # For captcha and ban mixed decision
      - './profiles.yaml:/etc/crowdsec/profiles.yaml:ro' 
      # For captcha only remediation
      # - './profiles_captcha_only.yaml:/etc/crowdsec/profiles.yaml:ro'
  ...

Exemple navigation

We can try to query normally the whoami server:

curl http://localhost:8000/foo

We can try to ban ourself

docker exec crowdsec cscli decisions add --ip 10.0.0.20 -d 4h --type captcha

We will see in the browser the captcha validation page:

To play the demo environment run:

make run_captcha

Note, if we are banned with a "ban" decision from crowdsec a captcha will not be asked and you will have to wait for the decision to expire or remove it manually.

docker exec crowdsec cscli decisions add --ip 10.0.0.10 -d 10m --type ban

Captcha Workflow

Context: The user has no decision attached to his IP

sequenceDiagram
    participant User
    participant TraefikPlugin
    User->>TraefikPlugin: Can I access that webpage
    create participant PluginCache
    TraefikPlugin-->>PluginCache: Does the user IP has a crowdsec decision ?
    Destroy PluginCache
    PluginCache-->>TraefikPlugin: Nothing, all good!
    Destroy TraefikPlugin
    TraefikPlugin->>Webserver: Forwarding this HTTP Request from User
    Webserver->>User: HTTP Response

Context: The user has a captcha decision attached to his IP

sequenceDiagram
    participant User
    participant TraefikPlugin
    User->>TraefikPlugin: Can I access that webpage
    create participant PluginCache
    TraefikPlugin-->>PluginCache: Does the User IP has a Crowdsec Decision ?
    PluginCache-->>TraefikPlugin: Yes a Catpcha Decision
    TraefikPlugin->>User: Please complete this captcha
    User->>TraefikPlugin: Fine, done!
    create participant ProviderCaptcha
    TraefikPlugin-->>ProviderCaptcha: Is the validation OK ?
    Destroy ProviderCaptcha    
    ProviderCaptcha-->>TraefikPlugin: Yes
    TraefikPlugin-->>PluginCache: Set the User IP Clean for captchaGracePeriodSeconds
    Destroy PluginCache
    PluginCache-->>TraefikPlugin: Done
    Destroy TraefikPlugin
    TraefikPlugin->>Webserver: Forwarding this HTTP Request from User
    Webserver->>User: HTTP Response

Context: The user has a ban decision attached to his IP

sequenceDiagram
    participant User
    participant TraefikPlugin
    User->>TraefikPlugin: Can I access that webpage
    create participant PluginCache
    TraefikPlugin-->>PluginCache: Does the User IP has a Crowdsec Decision ?
    Destroy PluginCache
    PluginCache-->>TraefikPlugin: Yes a ban Decision
    TraefikPlugin->>User: No, HTTP 403