Crowdsec Bouncer Traefik plugin

New! This plugin now supports AppSec feature including virtual patching and capabilities support for your legacy ModSecurity rules.

This plugin aims to implement a Crowdsec Bouncer in a Traefik plugin.

CrowdSec is an open-source and collaborative IPS (Intrusion Prevention System) and a security suite. We leverage local behavior analysis and crowd power to build the largest CTI network in the world.

The purpose is to enable Traefik to authorize or block requests from IPs based on their reputation and behavior.

The Crowdsec utility will provide the community blocklist which contains highly reported and validated IPs banned from the Crowdsec network.

When used with Crowdsec it will leverage the local API which will analyze Traefik logs and take decisions on the requests made by users/bots. Malicious actors will be banned based on patterns used against your website.

Appsec feature is supported from plugin version 1.2.0 and Crowdsec 1.6.0.

The AppSec Component offers:

Low-effort virtual patching capabilities.
Support for your legacy ModSecurity rules.
Combining classic WAF benefits with advanced CrowdSec features for otherwise difficult advanced behavior detection. More information on appsec in the Crowdsec Documentation.

Remediation offered by Crowdsec and supported by the plugin can be either ban or captcha.
For the ban remediation the user will be blocked in Traefik (HTTP 403).
For the captcha remediation, the user will be redirected to a page to complete a captcha challenge.

On successfull completion, he will be cleaned for a specified period of time before a new resolution challenge is expected if Crowdsec still has a decision to verify the user behavior. See the example captcha for more informations and configuration intructions.
The following captcha providers are supported now:

There are 5 operating modes (CrowdsecMode) for this plugin:

Mode	Description
none	If the client IP is on ban list, it will get a http code 403 response. Otherwise, request will continue as usual. All request call the Crowdsec LAPI
live	If the client IP is on ban list, it will get a http code 403 response. Otherwise, request will continue as usual. The bouncer can leverage use of a local cache in order to reduce the number of requests made to the Crowdsec LAPI. It will keep in cache the status for each IP that makes queries.
stream	Stream Streaming mode allows you to keep in the local cache only the Banned IPs, every requests that does not hit the cache is authorized. Every minute, the cache is updated with news from the Crowdsec LAPI.
alone	Standalone mode, similar to the streaming mode but the blacklisted IPs are fetched on the CAPI. Every 2 hours, the cache is updated with news from the Crowdsec CAPI. It does not include any locally banned IP, but can work without a crowdsec service.
appsec	Disable Crowdsec IP checking but apply Crowdsec Appsec checking. This mode is intended to be used when Crowdsec IP checking is applied at the Firewall Level.

The streaming mode is recommended for performance, decisions are updated every 60 sec by default and that's the only communication between Traefik and Crowdsec. Every request that happens hits the cache for quick decisions.

The cache can be local to Traefik in memory or using a separate Redis instance.

Below are Mermaid diagrams detailling how each mode work:

Mode none workflow

A Ban decision exists in CrowdsecLAPI

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

No decision in CrowdsecLAPI

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

Mode live workflow

A Ban decision exists in CrowdsecLAPI but not in cache

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: Nothing, all good!
    create participant CrowdsecLAPI
    TraefikPlugin-->>CrowdsecLAPI: Does the User IP has a crowdsec decision ?
    Destroy CrowdsecLAPI
    CrowdsecLAPI-->>TraefikPlugin: Yes a ban Decision
    TraefikPlugin-->>PluginCache: Store the information for this IP for DefaultDecisionSeconds
    Destroy PluginCache
    PluginCache-->>TraefikPlugin: Done
    TraefikPlugin->>User: No, HTTP 403

No decision in cache

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: Nothing, all good!
    create participant CrowdsecLAPI
    TraefikPlugin-->>CrowdsecLAPI: Does the User IP has a crowdsec decision ?
    Destroy CrowdsecLAPI
    CrowdsecLAPI-->>TraefikPlugin: Nothing, all good!
    TraefikPlugin-->>PluginCache: Store the information for this IP for DefaultDecisionSeconds
    Destroy PluginCache
    PluginCache-->>TraefikPlugin: Done
    TraefikPlugin->>Webserver: Forwarding this HTTP Request from User
    Webserver->>User: HTTP Response

Mode stream workflow

Cache Synchronization every UpdateIntervalSeconds

sequenceDiagram
    participant TraefikPlugin
    participant CrowdsecLAPI
    TraefikPlugin->>CrowdsecLAPI: What are the current decisions
    Destroy CrowdsecLAPI
    CrowdsecLAPI->>TraefikPlugin: Here is the list
    create participant PluginCache
    TraefikPlugin-->>PluginCache: Store this list
    Destroy PluginCache
    PluginCache-->>TraefikPlugin: Done

A Ban decision exists in cache

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
    Destroy TraefikPlugin
    TraefikPlugin->>User: No, HTTP 403

No decision in cache

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

Mode alone Workflow

Cache Synchronization every 2 hours to the Crowdsec Central API

sequenceDiagram
    participant TraefikPlugin
    participant CrowdsecCAPI
    TraefikPlugin->>CrowdsecCAPI: What are the current decisions from CAPI
    Destroy CrowdsecCAPI
    CrowdsecCAPI->>TraefikPlugin: Here is the list
    create participant PluginCache
    TraefikPlugin-->>PluginCache: Store this list
    Destroy PluginCache
    PluginCache-->>TraefikPlugin: Done

A Ban decision exists in cache

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
    Destroy TraefikPlugin
    TraefikPlugin->>User: No, HTTP 403

No decision in cache

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

Mode appsec workflow

The request is detected as malicious

sequenceDiagram
    participant User
    participant TraefikPlugin
    User->>TraefikPlugin: Can I access that webpage
    create participant CrowdsecAppSec
    TraefikPlugin-->>CrowdsecAppSec: Is this request malicious ?
    Destroy CrowdsecAppSec
    CrowdsecAppSec-->>TraefikPlugin: Yes I think so
    Destroy TraefikPlugin
    TraefikPlugin->>User: No, HTTP 403

The request is not detected as malicious

sequenceDiagram
    participant User
    participant TraefikPlugin
    User->>TraefikPlugin: Can I access that webpage
    create participant CrowdsecAppSec
    TraefikPlugin-->>CrowdsecAppSec: Is this request malicious ?
    Destroy CrowdsecAppSec
    CrowdsecAppSec-->>TraefikPlugin: No I don't think so
    Destroy TraefikPlugin
    TraefikPlugin->>Webserver: Forwarding this HTTP Request from User
    Webserver->>User: HTTP Response

Captcha decision workflow

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

Usage

To get started, use the docker-compose.yml file.

You can run it with:

make run

Note

/!\ Cache is shared by all services This means if an IP is banned, all services which are protected by an instance of the plugin will deny requests from that IP Only one instance of the plugin is possible.

Variables

Enabled
- bool
- default: false
- Enable the plugin
LogLevel
- string
- default: INFO, expected values are: INFO, DEBUG, ERROR, log are written to stdout / stderr
CrowdsecMode
- string
- default: live, expected values are: none, live, stream, alone, appsec
CrowdsecAppsecEnabled
- bool
- default: false
- Enable Crowdsec Appsec Server (WAF).
CrowdsecAppsecHost
- string
- default: "crowdsec:7422"
- Crowdsec Appsec Server available on which host and port. The scheme will be handled by the CrowdsecLapiScheme var.
CrowdsecAppsecFailureBlock
- bool
- default: true
- Block request when Crowdsec Appsec Server have a status 500.
CrowdsecAppsecUnreachableBlock
- bool
- default: true
- Block request when Crowdsec Appsec Server is unreachable.
CrowdsecLapiScheme
- string
- default: http, expected values are: http, https
CrowdsecLapiHost
- string
- default: "crowdsec:8080"
- Crowdsec LAPI available on which host and port.
CrowdsecLapiKey
- string
- default: ""
- Crowdsec LAPI key for the bouncer.
CrowdsecLapiTlsInsecureVerify
- bool
- default: false
- Disable verification of certificate presented by Crowdsec LAPI
CrowdsecLapiTlsCertificateAuthority
- string
- default: ""
- PEM-encoded Certificate Authority of the Crowdsec LAPI
CrowdsecLapiTlsCertificateBouncer
- string
- default: ""
- PEM-encoded client Certificate of the Bouncer
CrowdsecLapiTlsCertificateBouncerKey
- string
- default: ""
- PEM-encoded client private key of the Bouncer
ClientTrustedIPs
- string
- default: []
- List of client IPs to trust, they will bypass any check from the bouncer or cache (useful for LAN or VPN IP)
RemediationHeadersCustomName
- string
- default: ""
- Name of the header you want in response when request are cancelled (possible value of the header ban or captcha)
ForwardedHeadersCustomName
- string
- default: "X-Forwarded-For"
- Name of the header where the real IP of the client should be retrieved
ForwardedHeadersTrustedIPs
- []string
- default: []
- List of IPs of trusted Proxies that are in front of traefik (ex: Cloudflare)
RedisCacheEnabled
- bool
- default: false
- enable Redis cache instead of in-memory cache
RedisCacheHost
- string
- default: "redis:6379"
- hostname and port for the Redis service
RedisCachePassword
- string
- default: ""
- Password for the Redis service
RedisCacheDatabase
- string
- default: ""
- Database selection for the Redis service
HTTPTimeoutSeconds
- int64
- default: 10
- Default timeout in seconds for contacting Crowdsec LAPI
UpdateIntervalSeconds
- int64
- default: 60
- Used only in stream mode, the interval between requests to fetch blacklisted IPs from LAPI
UpdateMaxFailure
- int64
- default: 0
- Used only in stream and alone mode, the maximum number of time we can not reach Crowdsec before blocking traffic (set -1 to never block)
DefaultDecisionSeconds
- int64
- default: 60
- Used only in live mode, maximum decision duration
CrowdsecCapiMachineId
- string
- Used only in alone mode, login for Crowdsec CAPI
CrowdsecCapiPassword
- string
- Used only in alone mode, password for Crowdsec CAPI
CrowdsecCapiScenarios
- []string
- Used only in alone mode, scenarios for Crowdsec CAPI
CaptchaProvider
- string
- Provider to validate the captcha, expected values are: hcaptcha, recaptcha, turnstile
CaptchaSiteKey
- string
- Site key for the captcha provider
CaptchaSecretKey
- string
- Site secret key for the captcha provider
CaptchaGracePeriodSeconds
- int64
- default: 1800 (= 30 minutes)
- Period after validation of a captcha before a new validation is required if Crowdsec decision is still valid
CaptchaHTMLFilePath
- string
- default: /captcha.html
- Path where the captcha template is stored
BanHTMLFilePath
- string
- default: ""
- Path where the ban html file is stored (default empty ""=disabled)

Configuration

For each plugin, the Traefik static configuration must define the module name (as is usual for Go packages).

The following declaration (given here in YAML) defines a plugin:

Note that you don't need to copy all thoses settings but only the ones you want to use.
See the examples for advanced usage.

# Static configuration

experimental:
  plugins:
    bouncer:
      moduleName: github.com/maxlerebourg/crowdsec-bouncer-traefik-plugin
      version: vX.Y.Z # To update

# Dynamic configuration

http:
  routers:
    my-router:
      rule: host(`whoami.localhost`)
      service: service-foo
      entryPoints:
        - web
      middlewares:
        - crowdsec

  services:
    service-foo:
      loadBalancer:
        servers:
          - url: http://127.0.0.1:5000
  
  middlewares:
    crowdsec:
      plugin:
        bouncer:
          enabled: false
          logLevel: DEBUG
          updateIntervalSeconds: 60
          updateMaxFailure: 0
          defaultDecisionSeconds: 60
          httpTimeoutSeconds: 10
          crowdsecMode: live
          crowdsecAppsecEnabled: false
          crowdsecAppsecHost: crowdsec:7422
          crowdsecAppsecFailureBlock: true
          crowdsecAppsecUnreachableBlock: true
          crowdsecLapiKey: privateKey-foo
          crowdsecLapiKeyFile: /etc/traefik/cs-privateKey-foo
          crowdsecLapiHost: crowdsec:8080
          crowdsecLapiScheme: http
          crowdsecLapiTLSInsecureVerify: false
          crowdsecCapiMachineId: login
          crowdsecCapiPassword: password
          crowdsecCapiScenarios:
            - crowdsecurity/http-path-traversal-probing
            - crowdsecurity/http-xss-probing
            - crowdsecurity/http-generic-bf
          forwardedHeadersTrustedIPs: 
            - 10.0.10.23/32
            - 10.0.20.0/24
          clientTrustedIPs: 
            - 192.168.1.0/24
          forwardedHeadersCustomName: X-Custom-Header
          remediationHeadersCustomName: cs-remediation
          redisCacheEnabled: false
          redisCacheHost: "redis:6379"
          redisCachePassword: password
          redisCacheDatabase: "5"
          crowdsecLapiTLSCertificateAuthority: |-
            -----BEGIN CERTIFICATE-----
            MIIEBzCCAu+gAwIBAgICEAAwDQYJKoZIhvcNAQELBQAwgZQxCzAJBgNVBAYTAlVT
            ...
            Q0veeNzBQXg1f/JxfeA39IDIX1kiCf71tGlT
            -----END CERTIFICATE-----
          crowdsecLapiTLSCertificateAuthorityFile: /etc/traefik/crowdsec-certs/ca.pem
          crowdsecLapiTLSCertificateBouncer: |-
            -----BEGIN CERTIFICATE-----
            MIIEHjCCAwagAwIBAgIUOBTs1eqkaAUcPplztUr2xRapvNAwDQYJKoZIhvcNAQEL
            ...
            RaXAnYYUVRblS1jmePemh388hFxbmrpG2pITx8B5FMULqHoj11o2Rl0gSV6tHIHz
            N2U=
            -----END CERTIFICATE-----
          crowdsecLapiTLSCertificateBouncerFile: /etc/traefik/crowdsec-certs/bouncer.pem
          crowdsecLapiTLSCertificateBouncerKey: |-
            -----BEGIN RSA PRIVATE KEY-----
            MIIEogIBAAKCAQEAtYQnbJqifH+ZymePylDxGGLIuxzcAUU4/ajNj+qRAdI/Ux3d
            ...
            ic5cDRo6/VD3CS3MYzyBcibaGaV34nr0G/pI+KEqkYChzk/PZRA=
            -----END RSA PRIVATE KEY-----
          crowdsecLapiTLSCertificateBouncerKeyFile: /etc/traefik/crowdsec-certs/bouncer-key.pem
          captchaProvider: hcaptcha
          captchaSiteKey: FIXME
          captchaSecretKey: FIXME
          captchaGracePeriodSeconds: 1800
          captchaHTMLFilePath: /captcha.html
          banHTMLFilePath: /ban.html

Fill variable with value of file

CrowdsecLapiTlsCertificateBouncerKey, CrowdsecLapiTlsCertificateBouncer, CrowdsecLapiTlsCertificateAuthority, CrowdsecCapiMachineId, CrowdsecCapiPassword, CrowdsecLapiKey, CaptchaSiteKey and CaptchaSecretKey can be provided with the content as raw or through a file path that Traefik can read.
The file variable will be used as preference if both content and file are provided for the same variable.

Format is:

Content: VariableName: XXX
File : VariableNameFile: /path

Authenticate with LAPI

You can authenticate to the LAPI either with LAPIKEY or by using client certificates.
Please see below for more details on each option.

Generate LAPI KEY

You can generate a crowdsec API key for the LAPI.
You can follow the documentation here: docs.crowdsec.net/docs/user_guides/lapi_mgmt

docker compose -f docker-compose-local.yml up -d crowdsec
docker exec crowdsec cscli bouncers add crowdsecBouncer

This LAPI key must be set where is noted FIXME-LAPI-KEY in the docker-compose.yml

...
whoami:
  labels:
    - "traefik.http.middlewares.crowdsec.plugin.bouncer.crowdseclapikey=FIXME-LAPI-KEY"
    - "traefik.http.middlewares.crowdsec.plugin.bouncer.crowdseclapischeme=http"
    - "traefik.http.middlewares.crowdsec.plugin.bouncer.crowdseclapihost=crowdsec:8080"
...
crowdsec:
  environment:
    BOUNCER_KEY_TRAEFIK: FIXME-LAPI-KEY
...

Note:

Crowdsec does not require a specific format for la LAPI-key, you may use something like FIXME-LAPI-KEY but that is not recommanded for obvious reasons

You can then run all the containers:

docker compose up -d

Use certificates to authenticate with CrowdSec

You can follow the example in examples/tls-auth to view how to authenticate with client certificates with the LAPI.
In that case, communications with the LAPI must go through HTTPS.

A script is available to generate certificates in examples/tls-auth/gencerts.sh and must be in the same directory as the inputs for the PKI creation.

Use HTTPS to communicate with the LAPI

To communicate with the LAPI in HTTPS you need to either accept any certificates by setting the crowdsecLapiTLSInsecureVerify to true or add the CA used by the server certificate of Crowdsec using crowdsecLapiTLSCertificateAuthority or crowdsecLapiTLSCertificateAuthorityFile. Set the crowdsecLapiScheme to https.

Crowdsec must be listening in HTTPS for this to work. Please see the tls-auth example or the official documentation: docs.crowdsec.net/docs/local_api/tls_auth/

Manually add an IP to the blocklist (for testing purposes)

docker compose up -d crowdsec
docker exec crowdsec cscli decisions add --ip 10.0.0.10 -d 10m # this will be effective 10min
docker exec crowdsec cscli decisions remove --ip 10.0.0.10
docker exec crowdsec cscli decisions add --ip 10.0.0.10 -d 10m -t captcha # this will return a captcha challenge  
docker exec crowdsec cscli decisions remove --ip 10.0.0.10 -t captcha

Examples

1. Behind another proxy service (ex: clouflare) examples/behind-proxy/README.md

2. With Redis as an external shared cache examples/redis-cache/README.md

3. Using Trusted IP (ex: LAN OR VPN) that won't get filtered by crowdsec examples/trusted-ips/README.md

4. Using Crowdsec and Traefik installed as binary in a single VM examples/binary-vm/README.md

5. Using https communication and tls authentication with Crowdsec examples/tls-auth/README.md

6. Using Crowdsec and Traefik in Kubernetes examples/kubernetes/README.md

7. Using Traefik in standalone mode without Crowdsec examples/standalone-mode/README.md

8. Using Traefik with AppSec feature enabled examples/appsec-enabled/README.md

9. Using Traefik with Captcha remediation feature enabled examples/captcha/README.md

10. Using Traefik with Custom Ban HTML Page examples/custom-ban-page/README.md

Local Mode

Traefik also offers a developer mode that can be used for temporary testing of plugins not hosted on GitHub. To use a plugin in local mode, the Traefik static configuration must define the module name (as is usual for Go packages) and a path to a Go workspace, which can be the local GOPATH or any directory.

The plugins must be placed in the ./plugins-local directory, which should be in the working directory of the process running the Traefik binary. The source code of the plugin should be organized as follows:

./plugins-local/
    └── src
        └── github.com
            └── maxlerebourg
                └── crowdsec-bouncer-traefik-plugin
                    ├── bouncer.go
                    ├── bouncer_test.go
                    ├── go.mod
                    ├── LICENSE
                    ├── Makefile
                    ├── readme.md
                    └── vendor/*

For local development, a docker-compose.local.yml is provided which reproduces the directory layout needed by Traefik.
This works once you have generated and filled your LAPI-KEY (crowdsecLapiKey), if not read above for informations.

docker compose -f docker-compose.local.yml up -d

Equivalent to

make run_local

About

mathieuHa and I have been using Traefik since 2020 at Primadviz. We come from a web development and security engineer background and wanted to add the power of a very promising technology (Crowdsec) to the edge router we love.

We initially ran into this project: github.com/fbonalair/traefik-crowdsec-bouncer It was using traefik and forward auth middleware to verify every request.
They had to go through a webserver which then contacts another webservice (the crowdsec LAPI) to make a decision based on the source IP.
We initially proposed some improvements by implementing a streaming mode and a local cache.
With the Traefik hackathon we decided to implement our solution directly as a Traefik plugin which could be found by everyone on plugins.traefik.io and be more performant.