cert-manager-webhook-ovh

OVH Webhook for Cert Manager

OVH Webhook for Cert Manager

This is a webhook solver for OVH DNS. In short, if your domain has its DNS servers hosted with OVH, you can solve DNS challenges using Cert Manager and OVH Webhook for Cert Manager.

Requirements

Preparation

Before you install anything, 2 mains tasks need to be completed.

OVH API Keys

Obtaining API keys from your OVH account (in which your DNS zones are hosted) will allow this webhook to perform the necessary operations to help resolve Let’s Encrypt DNS01 challenges. In response to the DNS01 challenges, Let’s Encrypt will issue a valid TLS certiticate for your applications to use.

  1. Go to api.ovh.com console and log-in using your credentials

  2. Create a new OVH API key for this webhook (This needs to be done once per OVH account)

    • Application name: cert-manager-webhook-ovh (or anything you’d like)
    • Application description: API Keys for Cert Manager Webhook OVH (or anything you’d like)
    • Validity: Unlimited
    • Rights: (pre-populated)
      • GET /domain/zone/*
      • PUT /domain/zone/*
      • POST /domain/zone/*
      • DELETE /domain/zone/*
    • Restrict IPs: Leave blank or restrict as you need.

Take note of the ApplicationKey, ApplicationSecret and ConsumerKey and save them in a secure location.

Helm chart repository

  1. Add a new Helm repository

     helm repo add cert-manager-webhook-ovh-charts https://aureq.github.io/cert-manager-webhook-ovh/

  2. Refresh the repository information

     helm repo update

  3. Search for all available charts in this repository

     helm search repo cert-manager-webhook-ovh-charts --versions

    Or list the latest development/unstable versions

     helm search repo cert-manager-webhook-ovh-charts --versions --devel

Configuration

The configuration is done via values.yaml and for complete details, you should refer to the repository.

For each issuer:

Issuer vs ClusterIssuer

Issuers, and ClusterIssuers, are Kubernetes resources that represent certificate authorities (CAs) that are able to generate signed certificates by honoring certificate signing requests.

An Issuer is a namespaced resource, and it is not possible to issue certificates from an Issuer in a different namespace. This means you will need to create an Issuer in each namespace you wish to obtain Certificates in.

If you want to create a single Issuer that can be consumed in multiple namespaces, you should consider creating a ClusterIssuer resource. This is almost identical to the Issuer resource, however is non-namespaced so it can be used to issue Certificates across all namespaces.

If you are using cert-manager with an ingress controller, using a ClusterIssuer is recommended.

See cert-manager documentation for more details.

Secret vs Secret References

It is usually safe to provide your OVH API keys as part of your values.yaml file or on the command line. However, it may be needed to separate the domain of responsibility between Ops (in charge of deploying the chart) and Security (in charge of obtaining and deploying the OVH API keys).

When providing your OVH API keys directly, this chart stores the provided OVH API keys in a secret (format shown below) and then leverages secret references. The values of applicationKey, applicationSecret and consumerKey are base64 encoded.

If you decide to use secret references, simply indicate which secret name to use, and which key name in the secret holds the correct value.

If you are using a ClusterIssuer, then the secret should be stored in the same namespace as this webhook (usually cert-manager). And when using an Issuer, the secret should be stored in the same namespace as the issuer itself.

Example of a secret generated by this Helm Chart.

apiVersion: v1
kind: Secret
type: Opaque
metadata:
  name: ovh-credentials
  namespace: cert-manager
data:
  applicationKey: YW5BcHBsaWNhdGlvbktleQ==          # anApplicationKey
  applicationSecret: YW5BcHBsaWNhdGlvblNlY3JldA==   # anApplicationSecret
  consumerKey: YUNvbnN1bWVyS2V5                     # aConsumerKey

Proxy support

If your Kubernetes cluster requires a proxy to access the internet, you have the ability to set environment variables to help the webhook. This is done in values.yaml.

# Use this field to add environment variables relevant to this webhook.
# These fields will be passed on to the container when Chart is deployed.
environment:
  # Use these variables to configure the HTTP_PROXY environment variables
  HTTP_PROXY: "http://proxy:8080"
  HTTPS_PROXY: "http://proxy:8080"
  NO_PROXY: "10.0.0.0/8,127.0.0.0/8,172.16.0.0/12,192.168.0.0/16,*.svc,*.cluster.local,*.svc.cluster.local,169.254.169.254,127.0.0.1,localhost,localhost.localdomain"

Split Horizon DNS

Please note, using Split Horizon DNS is unsupported. Use at your own risks.

If you plan to use cert-manager to generate certificates for domains served via split DNS you need to ensure that your DNS server returns correct SOA record for your domain. Otherwise the certificate generation will fail with following error message:

Error presenting challenge: OVH API call failed: GET /domain/zone/com/status - HTTP Error 404: “This service does not exist”

In order to verify the record:

  dig example.com soa

Example correct response:

  ; <<>> DiG 9.18.1-1ubuntu1.3-Ubuntu <<>> example.com soa
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57237
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags:; udp: 65494
  ;; QUESTION SECTION:
  ;example.com.     IN  SOA

  ;; ANSWER SECTION:
  example.com.    86400 IN  SOA dns.ovh.net. tech.ovh.net. 2023020402 86400 3600 3600000 600

  ;; Query time: 52 msec
  ;; SERVER: 127.0.0.53#53(127.0.0.53) (UDP)
  ;; WHEN: Sat Feb 04 15:13:03 CET 2023
  ;; MSG SIZE  rcvd: 88

Example incorrect response, notice the missing answer section:

  ; <<>> DiG 9.18.1-1ubuntu1.3-Ubuntu <<>> ovh.com soa
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57237
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags:; udp: 65494
  ;; QUESTION SECTION:
  ;example.com.         IN  SOA

  ;; Query time: 52 msec
  ;; SERVER: 127.0.0.53#53(127.0.0.53) (UDP)
  ;; WHEN: Sat Feb 04 15:13:03 CET 2023
  ;; MSG SIZE  rcvd: 88

Installation

To install the cert-manager-webhook-ovh chart:

helm upgrade --install --namespace cert-manager -f values.yaml cm-webhook-ovh cert-manager-webhook-ovh-charts/cert-manager-webhook-ovh

To uninstall the chart:

helm uninstall --namespace cert-manager cm-webhook-ovh
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