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dockersslhttpsopenssl

"x509: certificate is not valid for any names" despite openssl shows correct

I'm following the docker book to configure Docker Engine API with SSL, here's the whole process:

# CA
echo 01 | sudo tee ca.srl
sudo openssl genrsa -des3 -out ca-key.pem
sudo openssl req -new -x509 -days 365 -key ca-key.pem -out ca.pem -subj "/CN=localhost"

# Server key
sudo openssl genrsa -des3 -out server-key.pem
sudo openssl req -new -key server-key.pem -out server.csr -subj "/CN=localhost"

# Server cert
echo subjectAltName = IP:x.x.x.x,IP:127.0.0.1 > extfile.cnf
sudo openssl x509 -req -days 365 -in server.csr -CA ca.pem -CAkey ca-key.pem -out server-cert.pem -extfile extfile.cnf

sudo openssl rsa -in server-key.pem -out server-key.pem
udo chmod 0600 /etc/docker/server-key.pem /etc/docker/server-cert.pem /etc/docker/ca-key.pem /etc/docker/ca.pem

# Client key
sudo openssl genrsa -des3 -out client-key.pem
sudo openssl req -new -key client-key.pem -out client.csr -subj "/CN=localhost"

# Client cert
echo extendedKeyUsage = clientAuth > extfile.cnf
sudo openssl x509 -req -days 365 -in client.csr -CA ca.pem -CAkey ca-key.pem -out client-cert.pem -extfile extfile.cnf
sudo openssl rsa -in client-key.pem -out client-key.pem

# Running docker engine
dockerd --tlsverify --tlscacert=ca.pem --tlscert=server-cert.pem --tlskey=server-key.pem 
-H=0.0.0.0:2376

# Client
docker -H localhost:2376 --tlsverify --tlscacert=ca.pem --tlscert=client-cert.pem --tlskey=client-key.pem info

# Output
Client:
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc., v0.7.1-docker)

Server:
ERROR: error during connect: Get "https://localhost:2376/v1.24/info": x509: certificate is not valid for any names, but wanted to match localhost
errors pretty printing info

And the cert definitely looks correct from OpenSSL

$ openssl x509 -noout -subject -in client-cert.pem
subject=CN = localhost

I tried both using localhost as well as using a VPS with a domain name, both no luck.

Solution

  • Thanks for @dave_thompson_085

    To fix the problem I need to add the DNS name to the SAN as well, so

    echo subjectAltName = DNS:xxx,IP:x.x.x.x,IP:127.0.0.1 > extfile.cnf

    Will fix the issue