ACME

Configuration Example

Below is an example of a basic configuration for ACME in Traefik.

File (YAML)

entryPoints:
  web:
    address: ":80"

  websecure:
    address: ":443"

certificatesResolvers:
  myresolver:
    acme:
      email: [email protected]
      storage: acme.json
      httpChallenge:
        # used during the challenge
        entryPoint: web

File (TOML)

[entryPoints]
  [entryPoints.web]
    address = ":80"

  [entryPoints.websecure]
    address = ":443"

[certificatesResolvers.myresolver.acme]
  email = "[email protected]"
  storage = "acme.json"
  [certificatesResolvers.myresolver.acme.httpChallenge]
    # used during the challenge
    entryPoint = "web"

CLI

--entryPoints.web.address=:80
--entryPoints.websecure.address=:443
# ...
--certificatesresolvers.myresolver.acme.email=your-email@example.com
--certificatesresolvers.myresolver.acme.storage=acme.json
# used during the challenge
--certificatesresolvers.myresolver.acme.httpchallenge.entrypoint=web

Helm Chart Values

# Traefik entryPoints configuration for HTTP and HTTPS.
entryPoints:
  web:
    address: ":80"
  websecure:
    address: ":443"

certificatesResolvers:
  myresolver:
    acme:
      email: "[email protected]"
      storage: "/data/acme.json"       # Path to store the certificate information.
      httpChallenge:
        # Entry point to use during the ACME HTTP-01 challenge.
        entryPoint: "web"

Configuration Options

ACME certificate resolvers have the following configuration options:

Field	Description	Default	Required
acme.email	Email address used for registration.	""	Yes
acme.caServer	CA server to use.	https://acme-v02.api.letsencrypt.org/directory	No
acme.preferredChain	Preferred chain to use. If the CA offers multiple certificate chains, prefer the chain with an issuer matching this Subject Common Name. If no match, the default offered chain will be used.	""	No
acme.keyType	KeyType to use.	"RSA4096"	No
acme.eab	Enable external account binding.	""	No
acme.eab.kid	Key identifier from External CA.		No
acme.eab.hmacEncoded	HMAC key from External CA, should be in Base64 URL Encoding without padding format.	""	No
acme.certificatesDuration	The certificates' duration in hours, exclusively used to determine renewal dates.	2160	No
acme.dnsChallenge	Enable DNS-01 challenge. More information here.	-	No
acme.dnsChallenge.provider	DNS provider to use.		No
acme.dnsChallenge.delayBeforeCheck	By default, the provider will verify the TXT DNS challenge record before letting ACME verify. If delayBeforeCheck is greater than zero, this check is delayed for the configured duration in seconds. Useful if internal networks block external DNS queries.		No
acme.dnsChallenge.resolvers	DNS servers to resolve the FQDN authority.		No
acme.dnsChallenge.disablePropagationCheck	Disable the DNS propagation checks before notifying ACME that the DNS challenge is ready.		No
acme.httpChallenge	Enable HTTP-01 challenge. More information here.		No
acme.httpChallenge.entryPoint	EntryPoint to use for the HTTP-01 challenges. Must be reachable by Let's Encrypt through port 80	""	Yes
acme.tlsChallenge	Enable TLS-ALPN-01 challenge. Traefik must be reachable by Let's Encrypt through port 443. More information here.	-	No
acme.storage	File path used for certificates storage.	"acme.json"	Yes

Automatic Certificate Renewal

Traefik automatically tracks the expiry date of certificates it generates. Certificates that are no longer used may still be renewed, as Traefik does not currently check if the certificate is being used before renewing.

By default, Traefik manages 90-day certificates and starts renewing them 30 days before their expiry. When using a certificate resolver that issues certificates with custom durations, the certificatesDuration option can be used to configure the certificates' duration.

Note

Certificates that are no longer used may still be renewed, as Traefik does not currently check if the certificate is being used before renewing.

The Different ACME Challenges

dnsChallenge

The DNS-01 challenge to generate and renew ACME certificates by provisioning a DNS record.

Traefik relies internally on Lego for ACME. You can find the list of all the supported DNS providers in their documentation with instructions about which environment variables need to be setup.

Note

CNAME are supported and even encouraged.

If needed, CNAME support can be turned off with the following environment variable:

LEGO_DISABLE_CNAME_SUPPORT=true

Multiple DNS challenge

Multiple DNS challenge provider are not supported with Traefik, but you can use CNAME to handle that. For example, if you have example.org (account foo) and example.com (account bar) you can create a CNAME on example.org called _acme-challenge.example.org pointing to challenge.example.com. This way, you can obtain certificates for example.com with the foo account.

delayBeforeCheck

By default, the provider verifies the TXT record before letting ACME verify. You can delay this operation by specifying a delay (in seconds) with delayBeforeCheck (value must be greater than zero). This option is useful when internal networks block external DNS queries.

tlsChallenge

Use the TLS-ALPN-01 challenge to generate and renew ACME certificates by provisioning a TLS certificate.

As described on the Let's Encrypt community forum, when using the TLS-ALPN-01 challenge, Traefik must be reachable by Let's Encrypt through port 443.

Configuring the tlsChallenge

File (YAML)

certificatesResolvers:
  myresolver:
    acme:
      # ...
      tlsChallenge: {}

File (TOML)

[certificatesResolvers.myresolver.acme]
  # ...
  [certificatesResolvers.myresolver.acme.tlsChallenge]

CLI

# ...
--certificatesresolvers.myresolver.acme.tlschallenge=true

httpChallenge

Use the HTTP-01 challenge to generate and renew ACME certificates by provisioning an HTTP resource under a well-known URI.

As described on the Let's Encrypt community forum, when using the HTTP-01 challenge, certificatesresolvers.myresolver.acme.httpchallenge.entrypoint must be reachable by Let's Encrypt through port 80.

Using an EntryPoint Called web for the httpChallenge

File (YAML)

entryPoints:
  web:
    address: ":80"

  websecure:
    address: ":443"

certificatesResolvers:
  myresolver:
    acme:
      # ...
      httpChallenge:
        entryPoint: web

File (TOML)

[entryPoints]
  [entryPoints.web]
    address = ":80"

  [entryPoints.websecure]
    address = ":443"

[certificatesResolvers.myresolver.acme]
  # ...
  [certificatesResolvers.myresolver.acme.httpChallenge]
    entryPoint = "web"

CLI

--entryPoints.web.address=:80
--entryPoints.websecure.address=:443
# ...
--certificatesresolvers.myresolver.acme.httpchallenge.entrypoint=web

Redirection is fully compatible with the HTTP-01 challenge.

Domain Definition

A certificate resolver requests certificates for a set of domain names inferred from routers, according to the following:

• If the IngressRoute has a tls.domains option set, then the certificate resolver derives this router domain name from the main option of tls.domains.

• Otherwise, the certificate resolver derives the domain name from any Host() or HostSNI() matchers in the IngressRoute's rule.

You can set SANs (alternative domains) for each main domain. Every domain must have A/AAAA records pointing to Traefik. Each domain & SAN will lead to a certificate request.

ACME v2 supports wildcard certificates. As described in Let's Encrypt's post wildcard certificates can only be generated through a DNS-01 challenge. It is not possible to request a double wildcard certificate for a domain (for example *.*.local.com).

Most likely the root domain should receive a certificate too, so it needs to be specified as SAN and 2 DNS-01 challenges are invoked. In such a case the generated DNS TXT record for both domains is the same. Even though this behavior is DNS RFC compliant, it can lead to problems as all DNS providers keep DNS records cached for a given time (TTL) and this TTL can be greater than the challenge timeout making the DNS-01 challenge fail.

The Traefik ACME client library lego supports some but not all DNS providers to work around this issue. The supported provider table indicates if they allow generating certificates for a wildcard domain and its root domain.

Wildcard Domains

ACME V2 supports wildcard certificates. As described in Let's Encrypt's post wildcard certificates can only be generated through a DNS-01 challenge.

External Account Binding

• kid: Key identifier from External CA
• hmacEncoded: HMAC key from External CA, should be in Base64 URL Encoding without padding format

File (YAML)

certificatesResolvers:
  myresolver:
    acme:
      # ...
      eab:
        kid: abc-keyID-xyz
        hmacEncoded: abc-hmac-xyz

File (TOML)

[certificatesResolvers.myresolver.acme]
  # ...
  [certificatesResolvers.myresolver.acme.eab]
    kid = "abc-keyID-xyz"
    hmacEncoded = "abc-hmac-xyz"

CLI

# ...
--certificatesresolvers.myresolver.acme.eab.kid=abc-keyID-xyz
--certificatesresolvers.myresolver.acme.eab.hmacencoded=abc-hmac-xyz

Using LetsEncrypt with Kubernetes

When using LetsEncrypt with kubernetes, there are some known caveats with both the Ingress and CRD providers.

Note

If you intend to run multiple instances of Traefik with LetsEncrypt, please ensure you read the sections on those provider pages.

LetsEncrypt Support with the Ingress Provider

By design, Traefik is a stateless application, meaning that it only derives its configuration from the environment it runs in, without additional configuration. For this reason, users can run multiple instances of Traefik at the same time to achieve HA, as is a common pattern in the kubernetes ecosystem.

When using a single instance of Traefik Proxy with Let's Encrypt, you should encounter no issues. However, this could be a single point of failure. Unfortunately, it is not possible to run multiple instances of Traefik 2.0 with Let's Encrypt enabled, because there is no way to ensure that the correct instance of Traefik receives the challenge request, and subsequent responses. Early versions (v1.x) of Traefik used a KV store to attempt to achieve this, but due to sub-optimal performance that feature was dropped in 2.0.

If you need Let's Encrypt with high availability in a Kubernetes environment, we recommend using Traefik Enterprise which includes distributed Let's Encrypt as a supported feature.

If you want to keep using Traefik Proxy, LetsEncrypt HA can be achieved by using a Certificate Controller such as Cert-Manager. When using Cert-Manager to manage certificates, it creates secrets in your namespaces that can be referenced as TLS secrets in your ingress objects .

Fallback

If Let's Encrypt is not reachable, the following certificates will apply:

1. Previously generated ACME certificates (before downtime)
2. Expired ACME certificates
3. Provided certificates

Important

For new (sub)domains which need Let's Encrypt authentication, the default Traefik certificate will be used until Traefik is restarted.

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