SSH from inside container docker to gcp instance in subnetwork - docker

Question

I already add public key to authorized keys to target instance. But I still cannot ssh from inside container to the instance. I'm doing this because I use jenkins in container. But I can ssh from outside container to target instance using public key from host instance. Key from container and host instance is different.
[jenkins#4f5159051056 /]$ ssh jenkins#10.64.0.5 -v
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug1: Connecting to 10.64.0.5 [10.64.0.5] port 22.
debug1: Connection established.
debug1: identity file /var/jenkins_home/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /var/jenkins_home/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /var/jenkins_home/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /var/jenkins_home/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /var/jenkins_home/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /var/jenkins_home/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /var/jenkins_home/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /var/jenkins_home/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4p1 Debian-10+deb9u3
debug1: match: OpenSSH_7.4p1 Debian-10+deb9u3 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 10.64.0.5:22 as 'jenkins'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305#openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305#openssh.com MAC: <implicit> compression: none
debug1: kex: curve25519-sha256 need=64 dh_need=64
debug1: kex: curve25519-sha256 need=64 dh_need=64
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:2QOdKiyn5cehOBPIfQFaEo8WvZz6BJYq4fc7gNIIJ1g
The authenticity of host '10.64.0.5 (10.64.0.5)' can't be established.
ECDSA key fingerprint is SHA256:2QOdKiyn5cehOBPIfQFaEo8WvZz6BJYq4fc7gNIIJ1g.
ECDSA key fingerprint is MD5:13:03:df:e8:e5:4b:f7:4a:9b:65:82:c3:9d:80:11:f4.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '10.64.0.5' (ECDSA) to the list of known hosts.
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /var/jenkins_home/.ssh/id_rsa
debug1: Authentications that can continue: publickey
debug1: Trying private key: /var/jenkins_home/.ssh/id_dsa
debug1: Trying private key: /var/jenkins_home/.ssh/id_ecdsa
debug1: Trying private key: /var/jenkins_home/.ssh/id_ed25519
debug1: No more authentication methods to try.
Permission denied (publickey).

Answer 1

Did you check the following
Setting proper permissions:
chmod 700 /var/jenkins_home/.ssh
chmod 644 /var/jenkins_home/.ssh/authorized_keys
Owner should be Jenkins in your case
chown -R jenkins:jenkins /var/jenkins_home/*
Also you are checking on the client side using ssh -v, you need to check on the server side why the server is not accepting the key Permission denied (publickey).Try checking in the below location
sudo vi /var/log/secure
EDITED
If faced with the below issue
localhost sshd[36601]: User jenkins from xxx.xxx.xxx.xxx not allowed because not listed in AllowUsers
and with this
localhost sshd[36601]: input_userauth_request: invalid
user myuser [preauth]
add the user jenkins to the below file
vim /etc/ssh/sshd_config
and restart service
systemctl restart sshd.service
It should workk now :)