Replacing expired certificates
If any of your TLS certs are approaching expiry and you are not relying on an
external certificate management solution such as cert-manager, you can follow
Manually Rotating Control Plane TLS Credentials
to update them without incurring downtime. However, if any of your certificates
have already expired, your mesh is already in an invalid state and any measures
to avoid downtime are not guaranteed to give good results. Instead, you need to
replace the expired certificates with valid certificates.
Replacing only the issuer certificate
It might be the case that your issuer certificate is expired. If this it true
running linkerd check --proxy will produce output similar to:
linkerd-identity
----------------
√ certificate config is valid
√ trust roots are using supported crypto algorithm
√ trust roots are within their validity period
√ trust roots are valid for at least 60 days
√ issuer cert is using supported crypto algorithm
× issuer cert is within its validity period
issuer certificate is not valid anymore. Expired on 2019-12-19T09:21:08Z
see https://linkerd.io/2/checks/#l5d-identity-issuer-cert-is-time-valid for hints
In this situation, if you have installed Linkerd with a manually supplied trust root and you have its key, you can follow the instructions to rotate your identity issuer certificate to update your expired certificate.
Replacing the root and issuer certificates
If your root certificate is expired or you do not have its key, you need to
replace both your root and issuer certificates at the same time. If your root
has expired linkerd check will indicate that by outputting an error similar
to:
linkerd-identity
----------------
√ certificate config is valid
√ trust roots are using supported crypto algorithm
× trust roots are within their validity period
Invalid roots:
* 272080721524060688352608293567629376512 identity.linkerd.cluster.local not valid anymore. Expired on 2019-12-19T10:05:31Z
see https://linkerd.io/2/checks/#l5d-identity-roots-are-time-valid for hints
You can follow Generating your own mTLS root certificates
to create new root and issuer certificates. Then use the linkerd upgrade
command:
linkerd upgrade \
--identity-issuer-certificate-file=./issuer-new.crt \
--identity-issuer-key-file=./issuer-new.key \
--identity-trust-anchors-file=./ca-new.crt \
--force \
| kubectl apply -f -
Usually upgrade will prevent you from using an issuer certificate that
will not work with the roots your meshed pods are using. At that point we
do not need this check as we are updating both the root and issuer certs at
the same time. Therefore we use the --force flag to ignore this error.
If you run linkerd check --proxy while pods are restarting after the trust
bundle is updated, you will probably see warnings about pods not having the
current trust bundle:
linkerd-identity
----------------
√ certificate config is valid
√ trust roots are using supported crypto algorithm
√ trust roots are within their validity period
√ trust roots are valid for at least 60 days
√ issuer cert is using supported crypto algorithm
√ issuer cert is within its validity period
√ issuer cert is valid for at least 60 days
√ issuer cert is issued by the trust root
linkerd-identity-data-plane
---------------------------
‼ data plane proxies certificate match CA
Some pods do not have the current trust bundle and must be restarted:
* linkerd/linkerd-controller-5b69fd4fcc-7skqb
* linkerd/linkerd-destination-749df5c74-brchg
* linkerd/linkerd-prometheus-74cb4f4b69-kqtss
* linkerd/linkerd-proxy-injector-cbd5545bd-rblq5
* linkerd/linkerd-sp-validator-6ff949649f-gjgfl
* linkerd/linkerd-tap-7b5bb954b6-zl9w6
* linkerd/linkerd-web-84c555f78-v7t44
see https://linkerd.io/2/checks/#l5d-identity-data-plane-proxies-certs-match-ca for hints
These warnings will disappear as restarts complete. Once they do, you can use
kubectl rollout restart to restart your meshed workloads to bring their
configuration up to date. After that is done, linkerd check should run with
no warnings or errors:
linkerd-identity
----------------
√ certificate config is valid
√ trust roots are using supported crypto algorithm
√ trust roots are within their validity period
√ trust roots are valid for at least 60 days
√ issuer cert is using supported crypto algorithm
√ issuer cert is within its validity period
√ issuer cert is valid for at least 60 days
√ issuer cert is issued by the trust root
linkerd-identity-data-plane
---------------------------
√ data plane proxies certificate match CA
