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SSH connection asks for password connecting to Docker container

I've already looked for similar questions and tried changing several things in my configuration but couldn't come up with a solution.

I'm trying to connecting via SSH to a Docker container, here's the Dockerfile:

FROM ubuntu

RUN apt-get update && \
 apt-get install -y openssh-server

RUN useradd remote_user && \
    echo "remote_user:test1234" | chpasswd && \
    mkdir /home/remote_user/.ssh -p && \
    chmod 700 /home/remote_user/.ssh && \
    mkdir -p -m0755 /var/run/sshd


COPY id_rsa.pub /home/remote_user/.ssh/authorized_keys

RUN chown remote_user:remote_user   -R /home/remote_user && \
    chmod 600 /home/remote_user/.ssh/authorized_keys

RUN apt-get install -y php php-mbstring php-xml php-bcmath php-fpm && \
    apt-get install -y composer && apt-get install -y vim
    
RUN apt-get install -y nginx

CMD /usr/sbin/sshd -D

Once I try to connect to the container as "remote_user" with ssh -Tv [email protected] (where "staging.local" is the container IP) I get this message:

...
...
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,[email protected],ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected]>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering public key: /home/xxx/.ssh/id_rsa RSA SHA256:5QNPe89pdQp+tgE61N9YPaIJEs8QR9DxaChmStfvzBU agent
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: xxx@xxx RSA SHA256:C+VWlGUd4mVywHnh8JWtjL0gmO8cuqUEs4YYCbQGvaE agent
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /home/xxx/.ssh/id_dsa
debug1: Trying private key: /home/xxx/.ssh/id_ecdsa
debug1: Trying private key: /home/xxx/.ssh/id_ecdsa_sk
debug1: Trying private key: /home/xxx/.ssh/id_ed25519
debug1: Trying private key: /home/xxx/.ssh/id_ed25519_sk
debug1: Trying private key: /home/xxx/.ssh/id_xmss
debug1: Next authentication method: password
[email protected]'s password:

As you can see it can't connect and is asking for the password.

If I ls -ll .ssh folder files in my host machine I have this:

-rw------- 1 xxx xxx 2610 Jan  3 12:08 id_rsa
-rw-r--r-- 1 xxx xxx  577 Jan  3 12:08 id_rsa.pub
-rw-r--r-- 1 xxx xxx  222 Jan  3 12:25 known_hosts

If I docker exec into the container as root user and see permissions of /home/remote_user/.ssh I have:

  • home folder permissions: drwxr-xr-x 1 root root 4096 Jan 3 11:22 home

  • remote_user folder permissions: drwxr-xr-x 1 remote_user remote_user 4096 Jan 3 11:22 remote_user

  • .ssh folder permissions: drwx------ 1 remote_user remote_user 4096 Jan 3 11:22 .ssh

  • authorized_keys file permissions: -rw------- 1 remote_user remote_user 577 Jan 3 11:08 authorized_keys

Solution

  • It should work if you forward the port :

    docker run -p 222:22 your-image

    then :

    ssh -p 222 remote_user@localhost