Using Kontena Vault
Kontena Vault is a secure key-value storage system that can be used to manage secrets for Kontena Stacks and Services in your Kontena Platform. Kontena Vault has built-in integration for managing LetsEncrypt certificates.
In this chapter, we'll discover how to manage secrets with Kontena Vault:
- List Secrets
- Write a Secret
- Read a Secret
- Update Secret
- Remove a Secret
- Using LetsEncrypt Certificates
$ kontena vault ls
Write a Secret to Vault
$ kontena vault write <name> <value>
Read a Secret
$ kontena vault read <name>
Note: Every read command will be added to the Kontena Master audit log
$ kontena vault update <name> <value>
Remove a Secret
$ kontena vault rm <name>
Using Let's Encrpyt Certificates
Kontena Vault integrates natively with Let's Encrypt to provide easy-to-use certificate management for your Kontena Services.
The following chapters describe the flow of getting certificates from Let's Encrypt: register --> authorize domain --> request certificate
Register for Let's Encrpyt
To use Let's Encrypt, you must first register as a user.
$ kontena certificate register <email@example.com>
By default this creates a new private key to be used with LE to identify the client.
Note: If you have already registered with other means and have an existing private key you wish to use you can import it into vault using the specific name
$ kontena vault write LE_PRIVATE_KEY "$(cat priv_key.pem)"
The email is needed for Let's Encrypt to notify when certificates are about to expire.
Note: This registration is needed only once per Kontena Platform.
Authorize the domain
In order to request a Let's Encrypt certificate for any domains, you must first prove that you are in control of each domain. Kontena's certificate management for Let's Encrypt supports different challenge types:
tls-sni-01(since 1.4, but out of service since 2018-01-10)
In order to use the automated challenge methods, HTTP/HTTPS connections to the domain(s) in question must be handled by a Kontena Load Balancer service.
HTTP-01 based verification
http-01 challenge is the most popular choice, and allows for automated certificate renewals.
$ kontena certificate authorize --type http-01 --linked-service ingress-lb/lb api.example.com [done] Waiting for http-01 challenge to be deployed into my-grid/ingress-lb/lb HTTP challenge is deployed, you can now request the actual certificate
Kontena automatically provisions the acme-challenge token/key-authorizations provided by LE to the linked service in the form of
ACME_CHALLENGE_* environment variable secrets.
The linked service is typically a Kontena Load Balancer service which responds to
GET /.well-known/acme-challenge requests using the provisioned tokens.
Later on when requesting the certificate, the Let's Encrypt verification servers will connect to the domain on TCP port 80, and make a HTTP request for the challenge token.
--linked-service must be configured to expose port 80.
TLS-SNI based verification
Note: All TLS-SNI variants have been disabled by Let's Encrypt since 2018-01-10 due to security weaknesses, and it is as of yet unknown if and when it may be re-enabled. See the Kontena Issue for further / more up-to-date information.
tls-sni-01 challenge can also be used for automated certificate renewals.
$ kontena certificate authorize --type tls-sni-01 --linked-service ingress-lb/lb api.example.com [done] Waiting for tls-sni-01 certificate to be deployed into my-grid/ingress-lb/lb TLS-SNI challenge certificate is deployed, you can now request the actual certificate
Kontena automatically provisions the challenge certificate provided by LE to the linked service in the form of
SSL_CERT_acme_challenge_* environment variable secrets.
The linked service is typically a Kontena Load Balancer service which responds to TLS-SNI connections for the
*.acme.invalid challenge certificate subject name.
Later on when requesting the certificate, the Let's Encrypt verification servers will connect to the domain on TCP port 443, and establish a TLS connection for the challenge hostname.
--linked-service must be configured to expose port 443.
DNS based verification
dns-01 challenge records must be deployed manually to the DNS zone, and cannot be used for automated certificate renewals.
$ kontena certificate authorize api.example.com Record name:_acme-challenge Record type:TXT Record content:5m1FCaNvneLduTN4AcPqAbyuQhBQA4ESisAQfEYvXIE
Before requesting the certificate, you must create a DNS TXT record for the domain
_acme-challenge.api.example.com with content specified in the output.
The advantage of the
dns-01 method is that the Let's Encrypt verification servers do not need to be able to connect to the domain, and can thus also be used for internal services not accessible to the internet.
Request the certificate
Once you have created and provisioned the domain authorizations, you can request the actual certificates from Let's Encrypt:
$ kontena certificate request api.example.com [done] Requesting certificate for api.example.com
Kontena automatically stores the certificate and (encrypted) private key into the secure vault in a format where it can be used for SSL termination with the Kontena Load Balancer. Kontena will include the complete certificate chain including any intermediary Let's Encrpyt CA certificates when deploying the requested certificates. This is because the Let's Encrypt CAs are not yet directly trusted by all SSL clients, including some libraries associated with Ruby, Docker, and e.g. wget.
Certificates with multiple domains
Let's Encrypt does not (yet) support wildcard certificates. In many cases it is necessary to serve multiple sites behind one certificate. For this, Let's Encrypt supports a concept called subject alternative names (SAN). To obtain a certificate for multiple DNS names, simply specify multiple domains in the request. The first domain in the list becomes the common name and others are used as alternative names:
$ kontena certificate request example.com www.example.com
Note: For each of the domains in the certificate request, it is necessary to complete the domain authorization first!
Certificate: Data: Version: 3 (0x2) Serial Number: fa:2c:99:7a:4e:76:10:97:fe:b9:7b:28:4a:c3:44:7a:fe:b1 Signature Algorithm: sha256WithRSAEncryption Issuer: CN=Fake LE Intermediate X1 Validity Not Before: Jul 1 06:31:00 2016 GMT Not After : Sep 29 06:31:00 2016 GMT Subject: CN=example.com Subject Public Key Info: ... X509v3 extensions: X509v3 Subject Alternative Name: DNS:www.example.com, DNS:example.com
Starting from Kontena 1.4 version, the Kontena Stack YAML services can include Kontena managed Let's Encrypt
services: my_loadbalancer: image: kontena/lb:latest ports: - 443:443 certificates: - subject: www.example.com type: env name: SSL_CERT_www.example.com
Kontena will inject the certificate from the vault into the
SSL_CERT_* environment variable for the service instance container.
Renewing Let's Encrypt certificates
If you have made the authorizations of all the domain in the certificate using either
tls-sni-01 type authorizations, then Kontena will automatically renew the certificate 7 days prior to it's expiration.
In practice this means that you must do the first request for the certificate manually and after that the management is fully automated.
dns-01 domain authorizations, the renewal process is fully manual as Kontena cannot automate the DNS challenge provisioning.
The expiration and auto-renewal support for each certificate can be checked using
kontena certificate list.
Inspecting certificate details
To get a list of managed certificates, use:
$ kontena certificate list SUBJECT EXPIRATION AUTO_RENEWABLE? ⊛ tls-sni-test.example.io 11 days ago false ⊛ web.126.96.36.199.xip.io 36 days true ⊛ demo.kontena.works 69 days true
To see single certificate details, use:
$ kontena certificate show web.188.8.131.52.xip.io --- id: e2e/web.184.108.40.206.xip.io subject: web.220.127.116.11.xip.io valid_until: '2017-11-22T09:55:00.000+00:00' alt_names:  auto_renewable: true
Exporting a certificate
To export a managed certificate, use:
$ kontena certificate export example.com -----BEGIN CERTIFICATE----- ... -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- ... -----END CERTIFICATE----- -----BEGIN RSA PRIVATE KEY----- ... -----END RSA PRIVATE KEY-----
This outputs the entire certificate bundle by default. Use the
--key options to export the different parts of the certificate separately.