"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?

Irisation

The answer here didn't resolve my issue , the official docs had the answer for me - docs.docker.com/registry/insecure . For me the certificate paths and update command are different for Red Hat and Ubuntu . – Shier

On my case, I was in a vbox with linux. First attempt got me this error. But in a second attempt the error dissapear – Matriculate

Answer 1

After updating OS certificates, you typically need to restart the docker service to get it to detect that change. This is usually done with:

sudo systemctl restart docker

or for non-systemd environments:

sudo service docker restart

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 for snap based installs:

/var/snap/docker/~current/etc/docker/certs.d/my-registry.example.com:5000/ca.crt

or in Windows 10:

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

If you don't already have the certificate, you can extract it using openssl. Note that this implicitly trusts whatever the registry currently says their certificate is, exposing you to MitM attacks. This can be useful as a TOFU (trust on first use) if you are not in an ephemeral environment:

openssl s_client -showcerts -connect my-registry.example.com:5000 < /dev/null \
  | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'

Revetment

Thanks! service docker restart fixed the issue after my change! The other note is useful as I can trust specific docker registries without affecting other applications. – Irisation

After doing the steps above I got rid of x509: certificate signed by unknown authority but then I got 401 Unauthorized errors. To solve I needed to docker login <docker registry> – Fontanel

We installed Docker in Ubuntu as a snap therefore to restart the service we ran the command service snap.docker.dockerd restart – Rhodonite

Answer 2

• first create an empty json file

  cat << EOF > /etc/docker/daemon.json
  { }
  EOF
  

• 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 !

Ordnance

XXX: Creating empty /etc/docker/daemon.json and restarting docker with systemctl restart docker caused my docker daemon to die. I had to remove created file to be able to run it again. – Ecosphere

In my case I had to also include {"insecure-registries":["<registry_address>:<registry_port>"]} in /etc/docker/daemon.json to make it work. – Dinnage

Thanks It worked like a charm, but I need to do the copy with sudo – Brooklet

Note: if you are using snap then the correct path is: /var/snap/docker/~current/etc/docker/certs.d – Stanwood

instead of empty /etc/docker/daemon.json create a valid empty JSON file /etc/docker/daemon.json. A valid empty json daemon.json file contains only curly brackets with space between brackets!!! --> { } – Ingrown

Note: when putting the cert into /usr/local/share/ca-certificates It must end with crt – Talent

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

Cathleencathlene

Why you need to install cert if you instruct docker to be "insecure"? – Masonite

Do not do this, you open yourself up to man in the middle attacks by allowing insecure registries. – Avery

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 "Connection is secure/Certificate is valid" (on Chrome) or "Show Certificate" (on Safari), and a certificate window popup will appear.

For Chrome users, click on tab "Details" and button "Export" at the bottom to export the certificate file.

For Safari users, 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.

Keim

Also for docker desktop on MacOS you can put a certificate into ~/.docker/certd.d/<REGISTRY_NAME>:<PORT>/. More info - docs.docker.com/desktop/faqs/macfaqs/… – Lacework

Answer 5

For Ubuntu 20:

$ sudo update-ca-certificates --fresh
$ openssl s_client -showcerts -verify 5 -connect registry-1.docker.io:443 < /dev/null 2>/dev/null | openssl x509 -outform PEM | tee ~/docker.crt
$ openssl s_client -showcerts -verify 5 -connect production.cloudflare.docker.com:443 < /dev/null 2>/dev/null | openssl x509 -outform PEM | tee ~/docker-com.crt
$ sudo cp ~/docker-com.crt /usr/local/share/ca-certificates/.
$ sudo cp ~/docker.crt /usr/local/share/ca-certificates/
$ sudo update-ca-certificates
$ sudo service docker restart

Occasionalism

I just add that certificates must have the .crt extension – Gerigerianna

this did it for me! in the example there are 2 docker images, dunno why this was neccesary in the example, but it worked. my problem was that we use a private repoman behind a corporate firewall, there was no simple "go there click export" or stuff – Radiobroadcast

Answer 6

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

Kyrakyriako

is it on the client or the server ? – Stodder

This worked for me too. Ubuntu : 22.04 – Incitement

"update-ca-certificates" and "service docker restart" worked for me. – Noncombatant

Answer 7

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

Moores

Answer 8

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

Juvenilia

Answer 9

Didn't see this mentioned in any of the answers. Here is the official docker documentation for setting up certs for each specific domain. This goes along with the most accepted answer. https://docs.docker.com/engine/security/certificates/

Path for:

• Linux: /etc/docker/certs.d/[domain of relevent cert]/[cert].crt
• Windows: C:/ProgramData/Docker/certs.d/[domain of relevent cert]/[cert].crt

If you are using WSL or WSL2 you will place the cert in the windows location.

A key problem that I encountered was that the extension of the cert is important to docker. I was not able to resolve the issue with a .cer ssl cert but was with .crt.

Cristinecristiona

Answer 10

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.

Deprecative

Answer 11

In Windows you can just follow instruction (much easier than other approaches which I found):

Open Windows Explorer, right-click the certificate, and choose Install certificate.

Then, select the following options:

• Store location: local machine
• Check place all certificates in the following store
• Click Browser, and select Trusted Root Certificate Authorities
• Click Finish

After adding the CA certificate to Windows, restart Docker Desktop
for Windows.

Also it's important to choose correct options!

Here I found this instruction: https://docs.docker.com/registry/insecure/#windows

Sacral

Answer 12

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.

Handshake

where will it be in m1 mac? – Ladawnladd

Answer 13

update ca without restart docker,and use root ca.cert, replace registry.clickpaas.tech with your domain:

sudo yum -y update ca-certificates;
sudo mkdir -p /etc/docker/certs.d/registry.clickpaas.tech/;
sudo cp /etc/ssl/certs/ca-bundle.crt /etc/docker/certs.d/registry.clickpaas.tech/;

Teleost

Answer 14

add --tls-verify=false in command, like podman build --tls-verify=false ...

Violaviolable

Thank you for your interest in contributing to the Stack Overflow community. This question already has quite a few answers—including one that has been extensively validated by the community. Are you certain your approach hasn’t been given previously? If so, it would be useful to explain how your approach is different, under what circumstances your approach might be preferred, and/or why you think the previous answers aren’t sufficient. Can you kindly edit your answer to offer an explanation? – Julenejulep

@JeremyCaney are you sure this comment is helpful? because his answer is helpful – Primogenitor

Answer 15

I'm running Rancher Desktop. I had to "Quit Rancher Desktop" and then restart it. This fixed my issue.

Thinnish