“docker pull” certificate signed by unknown authority

Question

I was trying to pull a docker image from a docker registry but hit the following issue:

$ docker pull <docker registry>/<image name>/<tag> 
Error response from daemon: Get <docker registry>/v1/_ping: x509: certificate signed by unknown authority

I tried with "curl" and get a similar error message:

 curl performs SSL certificate verification by default, using a "bundle"
 of Certificate Authority (CA) public keys (CA certs). If the default
 bundle file isn't adequate, you can specify an alternate file
 using the --cacert option.

So I downloaded the CA certificate and imported to the server (RedHat Linux 7) with the following commands:

cp root_cert.cer /etc/pki/ca-trust/source/anchors/
update-ca-trust

After the root cert is imported, I can see curl is working fine as it won't complain the cert error, however if I use docker pull I still have the same issue. Is docker using different ca-cert location than curl? How do I fix the issue with docker pull in this situation?

Answer 1

You may need to restart the docker service to get it to detect the change in OS certificates.

Docker does have an additional location you can use to trust individual registry server CA. You can place the CA cert inside /etc/docker/certs.d/<docker registry>/ca.crt. Include the port number if you specify that in the image tag, e.g in Linux.

/etc/docker/certs.d/my-registry.example.com:5000/ca.crt

or in Windows 10:

C:\ProgramData\docker\certs.d\ca.crt

Answer 2

• first create a file - /etc/docker/daemon.json

• than run the following to add certs

    openssl s_client -showcerts -connect [registry_address]:[registry_port] < /dev/null | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > /etc/docker/certs.d/[registry_address]/ca.crt
  

works without restart

OR

import the cert to system like

• save the cert to the file , like the command above (the port is crucial, no need for the protocol)

   openssl s_client -showcerts -connect [registry_address]:[registry_port] < /dev/null | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > ca.crt
  

• copy it to /usr/local/share/ca-certificates/

   sudo cp ca.crt /usr/local/share/ca-certificates/
  

• run update-ca-certificates

   sudo update-ca-certificates
  

• restart docker !

Answer 3

Here is a quick solution:

• Edit or create the file /etc/docker/daemon.json and add insecure-registries :

example for docker.squadwars.org:

{
    "insecure-registries" : ["docker.squadwars.org:443"]
}

• Restart docker daemon

systemctl restart docker

• Create a directory with the same name of the host .

example for docker.squadwars.org:

mkdir -p /etc/docker/certs.d/docker.squadwars.org

• Get the certificate and save it to the created directory.

ex +’/BEGIN CERTIFICATE/,/END CERTIFICATE/p’ <(echo | openssl s_client -showcerts -connect docker.squadwars.org:443) -scq > /etc/docker/certs.d/docker.squadwars.org/docker_registry.crt

Answer 4

For the MacOS Docker Desktop user:

Go to your repository's URL in a browser. You may have to accept all security prompts.

Click on the padlock 🔓on the address bar, then click on "Certificate" (on Chrome) or "Show Certificate" (on Safari).

Click and hold down on the big paper icon of the certificate and drag it to a folder of your preference, or the desktop.

Open your terminal (make sure to replace the last argument with the location of your file):

security add-trusted-cert -d -r trustRoot -k ~/Library/Keychains/login.keychain-db ~/<<<somefolder>>>/<<<yourserver.cer>>>

Restart your docker engine.

Answer 5

For my case, the error was on "docker login" command.

The solution I found for my ubuntu:

I downloaded the crt file via firefox (lock icon in the url adress bar) and save it : ~/mydomain:1234.crt

After that :

cp ~/mydomain:1234.crt /usr/local/share/ca-certificates/
update-ca-certificates
service docker restart

Answer 6

For anyone who is using CentOS 7, this is what worked for me:

• Obtain necessary certificate (e.g. from your company)
• Copy the certificate to ca-trust location:

sudo cp -p abc.crt /etc/pki/ca-trust/source

• Update the certificate:

sudo update-ca-trust extract

• Reload daemon and restart docker:

sudo systemctl daemon-reload
sudo systemctl restart docker

Answer 7

For me I ended up doing this to get it to work:

sudo cp -p abc.crt /etc/pki/ca-trust/source/anchors
sudo update-ca-trust
sudo update-ca-trust extract
sudo systemctl daemon-reload
sudo systemctl restart docker

Answer 8

By default docker keeps a local Certificate store, in Centos:/etc/sysconfig/docker. In Organizations, the servers usually comes preinstalled with it's own Root Cert. So if you use cert issued by the organization, docker will not be able to find the organization's Root Cert. when it refers to its local store. So either you can remove the reference to its local store in /etc/sysconfig/docker or you can delete it's local Certificate store (Centos:/etc/docker/certs.d). Restarting docker service after you make the change will resolve this issue.

Answer 9

In my case I had the same problem inside a KIND container. Curl didn't work there.

curl https://google.com
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.haxx.se/docs/sslcerts.html

curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.
    

and the update-ca-certificate command didn't work for me. I had to append the CA certificate to the /etc/ssl/certs/ca-certificates.crt file:

cat /ca_cert.pem >>  /etc/ssl/certs/ca-certificates.crt

And then curl worked properly.