Question regarding Host keys.

Thu Sep 8 07:47:36 AEST 2016

Thanks for the reply, the client is using 7.2 and the server is on 6.6
version.  And, here are the debug files attached.

Thanks,
Mahoda

With Change:
=========================================================================================
OpenSSH_7.2p2, OpenSSL 1.0.2h  3 May 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "192.168.1.1" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.1.1 [192.168.1.1] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/identity type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/identity-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_ecdsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-AtiSSH_2.0
debug1: Remote protocol version 2.0, remote software version
OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8
debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8 pat OpenSSH_6.6.1* compat
0x04000000
debug2: fd 3 setting O_NONBLOCK
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256 at libssh.org
,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: ecdsa-sha2-nistp256-cert-v01 at openssh.com,
ecdsa-sha2-nistp384-cert-v01 at openssh.com,
ecdsa-sha2-nistp521-cert-v01 at openssh.com,ssh-ed25519-cert-v01 at openssh.com,
ssh-rsa-cert-v01 at openssh.com
,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa,ssh-dss
debug2: ciphers ctos: chacha20-poly1305 at openssh.com
,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm at openssh.com,
aes256-gcm at openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: chacha20-poly1305 at openssh.com
,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm at openssh.com,
aes256-gcm at openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-sha1-etm at openssh.com,umac-64 at openssh.com,umac-128 at openssh.com
,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-sha1-etm at openssh.com,umac-64 at openssh.com,umac-128 at openssh.com
,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib at openssh.com,zlib
debug2: compression stoc: none,zlib at openssh.com,zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256 at libssh.org
,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
aes128-gcm at openssh.com,aes256-gcm at openssh.com,chacha20-poly1305 at openssh.com
,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,
rijndael-cbc at lysator.liu.se
debug2: ciphers stoc:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
aes128-gcm at openssh.com,aes256-gcm at openssh.com,chacha20-poly1305 at openssh.com
,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,
rijndael-cbc at lysator.liu.se
debug2: MACs ctos: hmac-md5-etm at openssh.com,hmac-sha1-etm at openssh.com,
umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-ripemd160-etm at openssh.com,hmac-sha1-96-etm at openssh.com,
hmac-md5-96-etm at openssh.com,hmac-md5,hmac-sha1,umac-64 at openssh.com,
umac-128 at openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
hmac-ripemd160 at openssh.com,hmac-sha1-96,hmac-md5-96
debug2: MACs stoc: hmac-md5-etm at openssh.com,hmac-sha1-etm at openssh.com,
umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-ripemd160-etm at openssh.com,hmac-sha1-96-etm at openssh.com,
hmac-md5-96-etm at openssh.com,hmac-md5,hmac-sha1,umac-64 at openssh.com,
umac-128 at openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
hmac-ripemd160 at openssh.com,hmac-sha1-96,hmac-md5-96
debug2: compression ctos: none,zlib at openssh.com
debug2: compression stoc: none,zlib at openssh.com
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256 at libssh.org
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305 at openssh.com MAC:
<implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305 at openssh.com MAC:
<implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256
SHA256:IwZ3AJCkBnQypTalkkezSSXShPg/+1eEDgHS65R8dN0
debug3: hostkeys_foreach: reading file "/flash/.home/root/.ssh/known_hosts"
debug3: hostkeys_foreach: reading file "/flash/.configs/ssh/ssh_known_hosts"
debug3: record_hostkey: found key type RSA in file
/flash/.configs/ssh/ssh_known_hosts:2
debug3: load_hostkeys: loaded 1 keys from 192.168.1.1
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the ECDSA key sent by the remote host is
SHA256:IwZ3AJCkBnQypTalkkezSSXShPg/+1eEDgHS65R8dN0.
Please contact your system administrator.
ECDSA host key for 192.168.1.1 has changed and you have requested strict
checking.
Host key verification failed.
=============================================================================================================================================

Without change:
=============================================================================================================================================
OpenSSH_7.2p2, OpenSSL 1.0.2h  3 May 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "192.168.1.1" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.1.1 [192.168.1.1] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/identity type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/identity-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /flash/.home/root/.ssh/id_ecdsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-AtiSSH_2.0
debug1: Remote protocol version 2.0, remote software version
OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8
debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2.8 pat OpenSSH_6.6.1* compat
0x04000000
debug2: fd 3 setting O_NONBLOCK
debug3: hostkeys_foreach: reading file "/flash/.home/root/.ssh/known_hosts"
debug3: hostkeys_foreach: reading file "/flash/.configs/ssh/ssh_known_hosts"
debug3: record_hostkey: found key type RSA in file
/flash/.configs/ssh/ssh_known_hosts:2
debug3: load_hostkeys: loaded 1 keys from 192.168.1.1
debug3: order_hostkeyalgs: prefer hostkeyalgs: ssh-rsa-cert-v01 at openssh.com
,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256 at libssh.org
,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: ssh-rsa-cert-v01 at openssh.com
,rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256-cert-v01 at openssh.com,
ecdsa-sha2-nistp384-cert-v01 at openssh.com,
ecdsa-sha2-nistp521-cert-v01 at openssh.com,ssh-ed25519-cert-v01 at openssh.com
,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519
debug2: ciphers ctos: chacha20-poly1305 at openssh.com
,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm at openssh.com,
aes256-gcm at openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: chacha20-poly1305 at openssh.com
,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm at openssh.com,
aes256-gcm at openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-sha1-etm at openssh.com,umac-64 at openssh.com,umac-128 at openssh.com
,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-sha1-etm at openssh.com,umac-64 at openssh.com,umac-128 at openssh.com
,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,zlib at openssh.com,zlib
debug2: compression stoc: none,zlib at openssh.com,zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256 at libssh.org
,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
aes128-gcm at openssh.com,aes256-gcm at openssh.com,chacha20-poly1305 at openssh.com
,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,
rijndael-cbc at lysator.liu.se
debug2: ciphers stoc:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,
aes128-gcm at openssh.com,aes256-gcm at openssh.com,chacha20-poly1305 at openssh.com
,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,
rijndael-cbc at lysator.liu.se
debug2: MACs ctos: hmac-md5-etm at openssh.com,hmac-sha1-etm at openssh.com,
umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-ripemd160-etm at openssh.com,hmac-sha1-96-etm at openssh.com,
hmac-md5-96-etm at openssh.com,hmac-md5,hmac-sha1,umac-64 at openssh.com,
umac-128 at openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
hmac-ripemd160 at openssh.com,hmac-sha1-96,hmac-md5-96
debug2: MACs stoc: hmac-md5-etm at openssh.com,hmac-sha1-etm at openssh.com,
umac-64-etm at openssh.com,umac-128-etm at openssh.com,
hmac-sha2-256-etm at openssh.com,hmac-sha2-512-etm at openssh.com,
hmac-ripemd160-etm at openssh.com,hmac-sha1-96-etm at openssh.com,
hmac-md5-96-etm at openssh.com,hmac-md5,hmac-sha1,umac-64 at openssh.com,
umac-128 at openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,
hmac-ripemd160 at openssh.com,hmac-sha1-96,hmac-md5-96
debug2: compression ctos: none,zlib at openssh.com
debug2: compression stoc: none,zlib at openssh.com
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256 at libssh.org
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: chacha20-poly1305 at openssh.com MAC:
<implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305 at openssh.com MAC:
<implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ssh-rsa
SHA256:UWb75G/DzMWOCH4KNR4As0lYcpI1POgD7TEX9iXYSLA
debug3: hostkeys_foreach: reading file "/flash/.home/root/.ssh/known_hosts"
debug3: hostkeys_foreach: reading file "/flash/.configs/ssh/ssh_known_hosts"
debug3: record_hostkey: found key type RSA in file
/flash/.configs/ssh/ssh_known_hosts:2
debug3: load_hostkeys: loaded 1 keys from 192.168.1.1
debug1: Host '192.168.1.1' is known and matches the RSA host key.
debug1: Found key in /flash/.configs/ssh/ssh_known_hosts:2
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /flash/.home/root/.ssh/identity ((nil))
debug2: key: /flash/.home/root/.ssh/id_rsa ((nil))
debug2: key: /flash/.home/root/.ssh/id_dsa ((nil))
debug2: key: /flash/.home/root/.ssh/id_ecdsa ((nil))
debug3: send packet: type 5
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /flash/.home/root/.ssh/identity
debug3: no such identity: /flash/.home/root/.ssh/identity: No such file or
directory
debug1: Trying private key: /flash/.home/root/.ssh/id_rsa
debug3: no such identity: /flash/.home/root/.ssh/id_rsa: No such file or
directory
debug1: Trying private key: /flash/.home/root/.ssh/id_dsa
debug3: no such identity: /flash/.home/root/.ssh/id_dsa: No such file or
directory
debug1: Trying private key: /flash/.home/root/.ssh/id_ecdsa
debug3: no such identity: /flash/.home/root/.ssh/id_ecdsa: No such file or
directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
===========================================================================================================================================

On 7 September 2016 at 16:53, Darren Tucker <dtucker at zip.com.au> wrote:

> On Wed, Sep 7, 2016 at 1:59 PM, Mahoda Ratnayaka <mahodardev at gmail.com>
> wrote:
> > I'm having a problem when I add "HostKeyAlgorithms +ssh-dss" to the
> > ssh_config file the host key will always negotiate to a wrong one. In my
> > case it will negotiate to "ecdsa-sha2-nistp256". The client was already
> > configured with the servers rsa public key, before the change I added to
> > the ssh_config file I could see from the debug that server and client
> will
> > negotiate to use ssh-rsa as expected. After change unfortunately the
> client
> > and server will negotiate to use ecdsa-sha2-nistp256, then later will
> > complain "REMOTE HOST IDENTIFICATION HAS CHANGED" and fail. I got around
> > this by adding the ecdsa public key to the know hosts.
>
> What version of OpenSSH is this?  Can you post debug output (ssh -vvv)
> with and without the +ssh-dss option?
>
> --
> Darren Tucker (dtucker at zip.com.au)
> GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860  37F4 9357 ECEF 11EA A6FA (new)
>     Good judgement comes with experience. Unfortunately, the experience
> usually comes from bad judgement.
>