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I have many servers for which I have properly generated keys, set permissions and was able to ssh/scp without password. However there is one machine which is a little bit different and I think that I have found the difference.

The difference is that on machine for which I coulnd not connect without password is that ssh is accepting keys:

debug1: Server accepts key: pkalg ssh-rsa blen 279

and all other my machines are accepting:

debug1: Server accepts key: pkalg rsa-sha2-512 blen 279

While creating ssh keys I always set argument "-t rsa" and I'm not sure which kind of key is generated. Can you help me to create ssh-rsa key instaed of rsa-sha2-512? And last one thing - I cannot modify /etc/ssh/sshd_config to change something.

Full dump of ssh log are below: One to which I can connect:

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 HOSTNAME [IP] port 22.
debug1: Connection established.
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.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_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to HOSTNAME:22 as 'SOMEUSER'
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:###HASH###
debug1: Host 'HOSTNAME' is known and matches the ECDSA host key.
debug1: Found key in /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/known_hosts:2
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Next authentication method: publickey
debug1: Offering RSA public key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug1: Authentication succeeded (publickey).
Authenticated to HOSTNAME ([IP]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8

Second one to which I cannot connect:

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 HOSTNAME [IP] port 22.
debug1: Connection established.
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.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 Sun_SSH_1.1.8
debug1: no match: Sun_SSH_1.1.8
debug1: Authenticating to HOSTNAME:22 as 'USERNAME'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: diffie-hellman-group-exchange-sha256
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha2-256 compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha2-256 compression: none
debug1: kex: diffie-hellman-group-exchange-sha256 need=32 dh_need=32
debug1: kex: diffie-hellman-group-exchange-sha256 need=32 dh_need=32
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<8192<8192) sent
debug1: got SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: got SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Server host key: ssh-rsa SHA256:###HASH###
debug1: Host 'HOSTNAME' is known and matches the RSA host key.
debug1: Found key in /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/known_hosts:13
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: gssapi-keyex,gssapi-with-mic,publickey,password,keyboard-interactive
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Next authentication method: publickey
debug1: Offering RSA public key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug1: Authentications that can continue: gssapi-keyex,gssapi-with-mic,publickey,password,keyboard-interactive
debug1: Trying private key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa
debug1: Trying private key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa
debug1: Trying private key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519
debug1: Next authentication method: keyboard-interactive
Password:

Command which I'm using in order to generate key:

ssh-keygen -b 2048 -t rsa -E sha256 -f filename

I have also tried to:

  • Create key with different parameters:

    -t rsa1; -t ecdsa; -b 1024; -b 2048;

  • 1
    What is the full command line you are using to generate your keys? Please edit the question to include this information. – DavidPostill Jan 4 at 16:50
  • @DavidPostill done. – J. Doe Jan 4 at 17:25
  • Why are the servers configured differently? One accepts keyboard-interactive and the other one does. You should make the necessary changes to sshd_config. Would be helpful if you provided the relevant information from sshd_config – Ramhound Jan 4 at 18:32

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