Missing begin marker error with public key ssh login

Question

I have two Redhat 7.3 machines. I want password-less ssh access to the machine2 from machine1. Here is what I have done. On machine1, I sudo (sudo su -) as a root and generated the rsa public and private keys using ssh-keygen command with all default settings. These are present in /root/.ssh/ directory with names id_rsa, id_rsa.pub The permissions for .ssh are as follows

drwx------  2 root root   54 Jan 17 05:08 .
drwxr-x---. 7 root root 4.0K Jan 17 04:08 ..
-rw-------  1 root root 1.7K Jan 17 06:18 id_rsa
-rw-r--r--  1 root root  414 Jan 17 06:18 id_rsa.pub
-rw-r--r--  1 root root 4.0K Jan 17 07:37 known_hosts

I copied the contents of id_rsa.pub to machine2 into the file authorized_keys in /root/.ssh created by myself as a root. permissions of .ssh directory on machine2 are as follows

drwxr-xr-x  2 root root   28 Jan 17 06:32 .
dr-xr-x---. 6 root root 4.0K Jan 17 03:28 ..
-rw-r--r--  1 root root  414 Jan 17 06:32 authorized_keys

Now I tried to ssh (with verbose) from machine1 to machine2 using the following command. But it still asks for the password to connect. I am expecting the connection should be established without asking for password.

I tried changing the permissions of .ssh and authorized_keys to 700 and 600 on machine2 as suggested by SSH asks for password, even with public key installed But the problem persists.

I have given the debug output of ssh command. It works as expected till the server accepts the public key. After that I notice debug1: key_parse_private2: missing begin marker might be causing this issue. Can any one suggest me a way out of this problem?

[root@machine1 ~]# ssh -v machine2
OpenSSH_6.6.1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug1: Connecting to machine2 [x.x.x.x] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/id_rsa type 1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1
debug1: match: OpenSSH_6.6.1 pat OpenSSH_6.6.1* compat 0x04000000
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr [email protected] none
debug1: kex: client->server aes128-ctr [email protected] none
debug1: kex: [email protected] need=16 dh_need=16
debug1: kex: [email protected] need=16 dh_need=16
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: RSA X:X:X:X:....
debug1: Host 'machine2' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:1
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
========================================================
| The system is to be used only by authorized users.   |
|                                                      |
| By continuing to use the system, the user represents |
|         that he/she is an authorized user.           |
|                                                      |
| Use of the system constitutes consent to monitoring  |
|                   and review.                        |
|                                                      |
|  I have received, read and understand the Company's  |
|   Acceptable Use Policy and agree to abide by the    |
|       policy and its terms and conditions.           |
|                                                      |
========================================================
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /root/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type RSA
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /root/.ssh/id_dsa
debug1: Trying private key: /root/.ssh/id_ecdsa
debug1: Trying private key: /root/.ssh/id_ed25519
debug1: Next authentication method: password
root@machine2's password: 

Solution

"Missing begin marker" is not really a problem, you get that message with successful passwordless public key logins.

You have a banner, so you probably have done some hardening. Make sure the following options are available to your user. You can add them at the end of your sshd_config file after a "Match User" line:

Match User root,user1
RSAAuthentication yes
PubkeyAuthentication yes
PermitRootLogin yes
PermitEmptyPasswords yes

PermitRootLogin is only required since you use root. I am not sure if PermitEmptyPasswords is required but it works for me.

Another (small) thing, don't sudo su -, do sudo -i.

Comments

[Romeo Ninov]

Try to change permission on machine2, directory /root/.ssh to be 700

[Ravi Chandra]

@Romeo Ninov, I have already tried that and mentioned in this post too... It did not solve the problem.

[Romeo Ninov]

Can you provide few lines from begin of id_rsa and the content of authorized_keys and id_rsa.pub. And check for empty lines in authorized_keys

[Ravi Chandra]

id_rsa: -----BEGIN RSA PRIVATE KEY----- MKIEpAIBdAKCAQEjtVQ5Zh1inry2g8XYzmUk5Dcg9n9++jRY+enwh+9qWJVx‌​7UGX YR6H0SJT7dFCe7ZGJGwgJrxRLrcOh3ujOJ3+tSS1iBoHBUpfucExsDD8JRE8‌​DduA id_rsa.pub: ssh-rsa AXBAB3NzaC1yf2EAAAADAQABAAXBAQ

[Ravi Chandra]

There is no empty line authorized_keys and the id_rsa.pub and authorized_keys are the same