TLS

General¶

When a TCP router is configured to handle TLS traffic, include a tls field in its definition. This field tells Traefik that the router should process only TLS connections and ignore non-TLS traffic.

By default, a router with a TLS field will terminate the TLS connections, meaning that it will send decrypted data to the services.

Configuration Example¶

Structured (YAML)

tcp:
  routers:
    my-tls-router:
      rule: "HostSNI(`example.com`)"
      service: "my-tcp-service"
      tls:
        passthrough: true
        options: "my-tls-options"
        domains:
          - main: "example.com"
            sans:
              - "www.example.com"
              - "api.example.com"
        certResolver: "myresolver"

Structured (TOML)

[tcp.routers.my-tls-router]
  rule = "HostSNI(`example.com`)"
  service = "my-tcp-service"

  [tcp.routers.my-tls-router.tls]
    passthrough = true
    options = "my-tls-options"
    certResolver = "myresolver"

    [[tcp.routers.my-tls-router.tls.domains]]
      main = "example.com"
      sans = ["www.example.com", "api.example.com"]

Labels

labels:
  - "traefik.tcp.routers.my-tls-router.tls=true"
  - "traefik.tcp.routers.my-tls-router.rule=HostSNI(`example.com`)"
  - "traefik.tcp.routers.my-tls-router.service=my-tcp-service"
  - "traefik.tcp.routers.my-tls-router.tls.passthrough=true"
  - "traefik.tcp.routers.my-tls-router.tls.options=my-tls-options"
  - "traefik.tcp.routers.my-tls-router.tls.certResolver=myresolver"
  - "traefik.tcp.routers.my-tls-router.tls.domains[0].main=example.com"
  - "traefik.tcp.routers.my-tls-router.tls.domains[0].sans=www.example.com,api.example.com"

Tags

{
  //...
  "Tags": [
    "traefik.tcp.routers.my-tls-router.tls=true"
    "traefik.tcp.routers.my-tls-router.rule=HostSNI(`example.com`)",
    "traefik.tcp.routers.my-tls-router.service=my-tcp-service",
    "traefik.tcp.routers.my-tls-router.tls.passthrough=true",
    "traefik.tcp.routers.my-tls-router.tls.options=my-tls-options",
    "traefik.tcp.routers.my-tls-router.tls.certResolver=myresolver",
    "traefik.tcp.routers.my-tls-router.tls.domains[0].main=example.com",
    "traefik.tcp.routers.my-tls-router.tls.domains[0].sans=www.example.com,api.example.com"
  ]
}

Postgres STARTTLS

Traefik supports the Postgres STARTTLS protocol, which allows TLS routing for Postgres connections.

To do so, Traefik reads the first bytes sent by a Postgres client, identifies if they correspond to the message of a STARTTLS negotiation, and, if so, acknowledges and signals the client that it can start the TLS handshake.

Please note/remember that there are subtleties inherent to STARTTLS in whether the connection ends up being a TLS one or not. These subtleties depend on the sslmode value in the client configuration (and on the server authentication rules). Therefore, it is recommended to use the require value for the sslmode.

Afterwards, the TLS handshake, and routing based on TLS, can proceed as expected.

Postgres STARTTLS with TCP TLS PassThrough routers

As mentioned above, the sslmode configuration parameter does have an impact on whether a STARTTLS session will succeed. In particular in the context of TCP TLS PassThrough, some of the values (such as allow) do not even make sense. Which is why, once more it is recommended to use the require value.

Configuration Options¶

Field	Description	Default	Required
`passthrough`	Defines whether the requests should be forwarded "as is", keeping all data encrypted.	false	No
`options`	enables fine-grained control of the TLS parameters. It refers to a TLS Options and will be applied only if a `HostSNI` rule is defined.	""	No
`certResolver`	The name of the certificate resolver to use for automatic certificate generation via ACME providers (such as Let's Encrypt). See the Certificate Resolver section for more details.	""	No
`domains`	List of domains and Subject Alternative Names (SANs) for explicit certificate domain specification. See the Custom Domains section for more details.	[]	No

Certificate Resolver¶

The tls.certResolver option allows you to specify a certificate resolver for automatic certificate generation via ACME providers (such as Let's Encrypt).

When a certificate resolver is configured for a router, Traefik will automatically obtain and manage TLS certificates for the domains specified in the router's rule (in the HostSNI matcher) or in the tls.domains configuration (with tls.domains taking precedence).

Prerequisites

Certificate resolvers must be defined in the static configuration
The router must have tls enabled
An ACME challenge type must be configured for the certificate resolver

Custom Domains¶

When using ACME certificate resolvers, domains are automatically extracted from router rules, but the tls.domains option allows you to explicitly specify the domains and Subject Alternative Names (SANs) for which certificates should be generated.

This provides fine-grained control over certificate generation and takes precedence over domains automatically extracted from router rules.

Every domain must have A/AAAA records pointing to Traefik.

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