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Kash, Howard M CIV USARMY ARL (US)

2015-Jul-24 13:14 UTC

Cisco vs. 6.9

> Many aging ciphers, hashes, and key exchanges are in the process of being
> retired.  <1kbit Diffie Hellman moduli have been removed as well in 6.9,
I
> believe.
> 
> If the Ciscos rely on <1kbit DH moduli or SHA1/MD5 hash based proposals
to
> work, that could be your problem.
We did not update the moduli file.

> A comparison of the two versions' output from: (ssh -Q kex ; ssh -Q mac
;
ssh> -Q cipher) MAY help narrow it down
Outputs are identical other than 6.7 prints diffie-hellman-group1-sha1
twice.

> but I think you'll need to enable protocol
> debug logging on the server side and see which proposals that the Cisco is
> using that's no longer available in 6.9 (by default).  You may just
need
to> add two or three lines to 6.9's sshd_config file, i.e.,
> KexAlgorithms/MACs/Ciphers.
It doesn't appear to be a kex, mac, or cipher issue as the problem is
occurring after successful password authentication.  Here's the debug output
from initial connection to termination:

Connection from A.B.C.D port 57737 on E.F.G.H port 22
debug1: Client protocol version 2.0; client software version Cisco-1.25
debug1: match: Cisco-1.25 pat Cisco-1.* compat 0x40000000
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.9p1
debug2: fd 3 setting O_NONBLOCK
debug2: Network child is on pid 7677
debug3: preauth child monitor started
debug3: privsep user:group 99:99 [preauth]
debug1: permanently_set_uid: 99/99 [preauth]
debug1: list_hostkey_types: ssh-rsa,ssh-dss [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug1: AUTH STATE IS 0 [preauth]
debug2: kex_parse_kexinit:
diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group-
exchange-sha256,curve25519-sha256 at libssh.org,ecdh-sha2-nistp256,ecdh-sha2-ni
stp384,ecdh-sha2-nistp521 [preauth]
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss [preauth]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc
[preauth]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc
[preauth]
debug2: kex_parse_kexinit: hmac-sha1 [preauth]
debug2: kex_parse_kexinit: hmac-sha1 [preauth]
debug2: kex_parse_kexinit: none,zlib at openssh.com [preauth]
debug2: kex_parse_kexinit: none,zlib at openssh.com [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
debug2: kex_parse_kexinit: reserved 0  [preauth]
debug2: kex_parse_kexinit:
diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellma
n-group1-sha1 [preauth]
debug2: kex_parse_kexinit: ssh-rsa [preauth]
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
[preauth]
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
[preauth]
debug2: kex_parse_kexinit: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
[preauth]
debug2: kex_parse_kexinit: hmac-sha1,hmac-sha1-96,hmac-md5,hmac-md5-96
[preauth]
debug2: kex_parse_kexinit: none [preauth]
debug2: kex_parse_kexinit: none [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit:  [preauth]
debug2: kex_parse_kexinit: first_kex_follows 0  [preauth]
debug2: kex_parse_kexinit: reserved 0  [preauth]
debug1: REQUESTED ENC.NAME is '3des-cbc' [preauth]
debug1: kex: client->server 3des-cbc hmac-sha1 none [preauth]
debug1: REQUESTED ENC.NAME is '3des-cbc' [preauth]
debug1: kex: server->client 3des-cbc hmac-sha1 none [preauth]
debug2: bits set: 974/2048 [preauth]
debug1: expecting SSH2_MSG_KEXDH_INIT [preauth]
debug2: bits set: 1077/2048 [preauth]
debug3: mm_key_sign entering [preauth]
debug3: mm_request_send entering: type 6 [preauth]
debug3: mm_key_sign: waiting for MONITOR_ANS_SIGN [preauth]
debug3: mm_request_receive_expect entering: type 7 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 6
debug3: mm_answer_sign
debug3: mm_answer_sign: hostkey proof signature 0x7fd190fb2a60(271)
debug3: mm_request_send entering: type 7
debug2: monitor_read: 6 used once, disabling now
debug2: set_newkeys: mode 1 [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug2: set_newkeys: mode 0 [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user username service ssh-connection method
none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug3: mm_getpwnamallow entering [preauth]
debug3: mm_request_send entering: type 8 [preauth]
debug3: mm_getpwnamallow: waiting for MONITOR_ANS_PWNAM [preauth]
debug3: mm_request_receive_expect entering: type 9 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 8
debug3: mm_answer_pwnamallow
debug2: parse_server_config: config reprocess config len 1176
[list of tokens removed for brevity]
debug3: auth_shadow_acctexpired: today 16640 sp_expire -1 days left -16641
debug3: account expiration disabled
debug3: mm_answer_pwnamallow: sending MONITOR_ANS_PWNAM: 1
debug3: mm_request_send entering: type 9
debug2: monitor_read: 8 used once, disabling now
debug2: input_userauth_request: setting up authctxt for username [preauth]
debug3: mm_inform_authserv entering [preauth]
debug3: mm_request_send entering: type 4 [preauth]
debug3: mm_auth2_read_banner entering [preauth]
debug3: mm_request_send entering: type 10 [preauth]
debug3: mm_request_receive_expect entering: type 11 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 4
debug3: mm_answer_authserv: service=ssh-connection, styledebug2: monitor_read: 4
used once, disabling now
debug3: mm_request_receive entering
debug3: monitor_read: checking request 10
debug3: mm_request_send entering: type 11
debug2: monitor_read: 10 used once, disabling now
debug1: userauth_send_banner: sent [preauth]
debug2: input_userauth_request: try method none [preauth]
debug3: userauth_finish: failure partial=0 next
methods="gssapi-keyex,gssapi-with-mic,password" [preauth]
debug1: userauth-request for user username service ssh-connection method
password [preauth]
debug1: attempt 1 failures 0 [preauth]
debug2: input_userauth_request: try method password [preauth]
debug3: mm_auth_password entering [preauth]
debug3: mm_request_send entering: type 12 [preauth]
debug3: mm_auth_password: waiting for MONITOR_ANS_AUTHPASSWORD [preauth]
debug3: mm_request_receive_expect entering: type 13 [preauth]
debug3: mm_request_receive entering [preauth]
debug3: mm_request_receive entering
debug3: monitor_read: checking request 12
debug1: temporarily_use_uid: 934/55 (e=0/0)
debug1: restore_uid: 0/0
debug3: mm_answer_authpassword: sending result 1
debug3: mm_request_send entering: type 13
Accepted password for username from A.B.C.D port 57737 ssh2
debug1: monitor_child_preauth: username has been authenticated by privileged
process
debug3: mm_get_keystate: Waiting for new keys
debug3: mm_request_receive_expect entering: type 26
debug3: mm_request_receive entering
debug3: mm_get_keystate: GOT new keys
debug3: mm_auth_password: user authenticated [preauth]
debug3: mm_request_send entering: type 26 [preauth]
debug3: mm_send_keystate: Finished sending state [preauth]
debug1: monitor_read_log: child log fd closed
debug3: mm_share_sync: Share sync
debug3: mm_share_sync: Share sync end
debug1: temporarily_use_uid: 934/55 (e=0/0)
debug1: ssh_gssapi_storecreds: Not a GSSAPI mechanism
debug1: restore_uid: 0/0
User child is on pid 7678
debug1: permanently_set_uid: 934/55
debug3: monitor_apply_keystate: packet_set_state
debug2: set_newkeys: mode 0
debug2: set_newkeys: mode 1
debug1: ssh_packet_set_postauth: called
debug3: ssh_packet_set_state: done
debug3: notify_hostkeys: key 1: ssh-rsa SHA256:XXXXXXXXX
debug3: notify_hostkeys: key 2: ssh-dss SHA256:XXXXXXXXX
debug3: notify_hostkeys: sent 2 hostkeys
debug1: Entering interactive session for SSH2.
debug2: fd 5 setting O_NONBLOCK
debug2: fd 6 setting O_NONBLOCK
debug1: server_init_dispatch_20
debug1: server_input_channel_open: ctype session rchan 3 win 8192 max 4096
debug1: input_session_request
debug1: channel 0: new [server-session]
debug2: session_new: allocate (allocated 0 max 10)
debug3: session_unused: session id 0 unused
debug1: session_new: session 0
debug1: session_open: channel 0
debug1: session_open: session 0: link with channel 0
debug1: server_input_channel_open: confirm session
Connection closed by A.B.C.D
debug1: channel 0: free: server-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 server-session (t10 r3 i0/0 o0/0 fd -1/-1 cc -1)

debug1: session_close: session 0 pid 0
debug3: session_unused: session id 0 unused
debug1: do_cleanup
debug1: krb5_cleanup_proc called
Transferred: sent 3680, received 816 bytes
Closing connection to A.B.C.D port 57737
debug3: mm_request_send entering: type 50
debug3: mm_request_receive entering
debug3: monitor_read: checking request 50
debug3: mm_answer_term: tearing down sessions


Howard
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Kash, Howard M CIV USARMY ARL (US)

2015-Jul-24 20:11 UTC

head link

Cisco vs. 6.9

As another data point, Cisco devices are also unable to scp to a system running
version 6.8.  So the incompatibility was introduced between 6.7 and 6.8.

I've been debugging all day and it seems like 6.8 is skipping or adding an
extra increment to the packet sequence number.  The debug output from 6.7 has:

  MAC #6 ok
  done calc MAC out #7
  MAC #7 ok

but 6.9 skips #7 and goes to 8:

  MAC #6 ok
  done calc MAC out #8

This is when the connection is closed by the Cisco device.


Howard

Kash, Howard M CIV USARMY ARL (US)

2015-Jul-28 15:42 UTC

head link

Cisco vs. 6.9

Turns out the problem is the new protocol extension for sending host keys to
the client after user authentication (section 2.5 of the PROTOCOLS
document).  Commenting out the notify_hostkeys() call in sshd.c fixes the
issues with Cisco scp.  Maybe a new bug compatibility flag in on order to
add to the "Cisco-1.*" client string that was added in 6.9?


Howard
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Kash, Howard M CIV USARMY ARL (US)

2015-Jul-28 16:20 UTC

head link

Cisco vs. 6.9

> Turns out the problem is the new protocol extension for sending host keys
to> the client after user authentication (section 2.5 of the PROTOCOLS
> document).  Commenting out the notify_hostkeys() call in sshd.c fixes the
> issues with Cisco scp.  Maybe a new bug compatibility flag in on order to
> add to the "Cisco-1.*" client string that was added in 6.9?
There's already a flag... just need to add SSH_BUG_HOSTKEYS to
"Cisco-1.*"
in compat.c.


Howard
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