Re: cant connect, ssh hangs after SSH2_MSG_KEX_DH_GEX_GROUP

Paul Dean wrote:
Looks like the sshd is not getting the ssh key request from the client
properly.

I would check you ssh_config file and ~/.ssh/config and make sure you
haven't put something in that breaks the client.

If that fails try apt-get --reinstall install ssh to reinstall on your
client boxen.

On the client, there is no ~/.ssh/config. There is only known_hosts and
random_seed.

I have booted a live Linux (Knoppix) on the client, that should ensure
that the client is not broken. In addition to that I have also compiled
a fresh openssh on the client with the same problems.

This is the /etc/ssh/ssh_config on the client

mw@client:~> cat /etc/ssh/ssh_config
# Host *
ForwardAgent yes
ForwardX11 yes
HostbasedAuthentication yes
RhostsRSAAuthentication yes
RSAAuthentication yes
EnableSSHKeysign yes
#PreferredAuthentications hostbased
TISAuthentication no
PasswordAuthentication yes
#FallBackToRsh no
#UseRsh no
BatchMode no
StrictHostKeyChecking ask
#IdentityFile ~/.ssh/identity
Port 22
Cipher 3des
EscapeChar none

On Thu, 08 Feb 2007 13:55:46 +0100
mw-u2@xxxxxx wrote:

Hi,

starting a while ago I can no longer ssh into my box anymore. I have
tried anything I can think of and have no clue anymore. Needless to
say that I realy need ssh to access my work from remote places.

Problem:
When I ssh -vvv to my server the connection hangs after
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP

System:
I'm using Debian with openssh-server (1:4.3p2-8)
sshd: OpenSSH_4.3p2 Debian-8, OpenSSL 0.9.8c 05 Sep 2006
uname -a: Linux server 2.6.18-3-686 #1 SMP Mon Dec 4 16:41:14 UTC
2006 i686 GNU/Linux

What I tried:
I have recompiled a recent openssh from source on the client with now
success. (I have no root access on the client and they use an older
version of ssh)

I have booted grml (grml.org, a live linux cd) on my server and tried
to connect to the sshd running from cd in order have a fresh sshd on
my server.

I have purged and reinstalled openssh-server to get a fresh
configuration.

I _can_ connect with putty on a windows client.

I hope you can help me, and thank you for your consideration.

=== Client Log ===

mw@client:~> ssh -vvv mw@server
OpenSSH_3.8.1p1 Debian-8.sarge.6, OpenSSL 0.9.7e 25 Oct 2004
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: ssh_connect: needpriv 0
debug1: Connecting to server [x.x.x.x] port 22.
debug1: Connection established.
debug1: read PEM private key done: type DSA
debug1: read PEM private key done: type RSA
debug1: identity file /home/mw/.ssh/identity type -1
debug1: identity file /home/mw/.ssh/id_rsa type -1
debug1: identity file /home/mw/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version
OpenSSH_4.3p2 Debian-8 debug1: match: OpenSSH_4.3p2 Debian-8 pat
OpenSSH* debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_3.8.1p1 Debian-8.sarge.6
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit:
diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1 debug2:
kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit:
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@xxxxxxxxxxxxxx,aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit:
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@xxxxxxxxxxxxxx,aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@xxxxxxxxxxx,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@xxxxxxxxxxx,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib debug2: kex_parse_kexinit:
none,zlib debug2: kex_parse_kexinit: debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0 debug2:
kex_parse_kexinit: reserved 0 debug2: kex_parse_kexinit:
diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss debug2: kex_parse_kexinit:
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@xxxxxxxxxxxxxx,aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit:
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc@xxxxxxxxxxxxxx,aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@xxxxxxxxxxx,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160@xxxxxxxxxxx,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@xxxxxxxxxxx debug2:
kex_parse_kexinit: none,zlib@xxxxxxxxxxx debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: debug2: kex_parse_kexinit:
first_kex_follows 0 debug2: kex_parse_kexinit: reserved 0 debug2:
mac_init: found hmac-md5 debug1: kex: server->client aes128-cbc
hmac-md5 none debug2: mac_init: found hmac-md5 debug1: kex:
client->server aes128-cbc hmac-md5 none debug1:
SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting
SSH2_MSG_KEX_DH_GEX_GROUP -- and it hangs here and stays forever

=== Server Log ===

server:~# /usr/sbin/sshd -D -d -d -d -e
debug2: load_server_config: filename /etc/ssh/sshd_config
debug2: load_server_config: done config len = 638
debug2: parse_server_config: config /etc/ssh/sshd_config len 638
debug1: sshd version OpenSSH_4.3p2 Debian-8
debug3: Not a RSA1 key file /etc/ssh/ssh_host_rsa_key.
debug1: read PEM private key done: type RSA
debug1: private host key: #0 type 1 RSA
debug3: Not a RSA1 key file /etc/ssh/ssh_host_dsa_key.
debug1: read PEM private key done: type DSA
debug1: private host key: #1 type 2 DSA
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-D'
debug1: rexec_argv[2]='-d'
debug1: rexec_argv[3]='-d'
debug1: rexec_argv[4]='-d'
debug1: rexec_argv[5]='-e'
debug2: fd 3 setting O_NONBLOCK
debug1: Bind to port 22 on ::.
Server listening on :: port 22.
debug2: fd 4 setting O_NONBLOCK
debug1: Bind to port 22 on 0.0.0.0.

debug3: fd 4 is not O_NONBLOCK
debug1: Server will not fork when running in debugging mode.
debug3: send_rexec_state: entering fd = 7 config len 638
debug3: ssh_msg_send: type 0
debug3: send_rexec_state: done
debug1: rexec start in 4 out 4 newsock 4 pipe -1 sock 7
debug3: recv_rexec_state: entering fd = 5
debug3: ssh_msg_recv entering
debug3: recv_rexec_state: done
debug2: parse_server_config: config rexec len 638
debug1: sshd version OpenSSH_4.3p2 Debian-8
debug3: Not a RSA1 key file /etc/ssh/ssh_host_rsa_key.
debug1: read PEM private key done: type RSA
debug1: private host key: #0 type 1 RSA
debug3: Not a RSA1 key file /etc/ssh/ssh_host_dsa_key.
debug1: read PEM private key done: type DSA
debug1: private host key: #1 type 2 DSA
debug1: inetd sockets after dupping: 3, 3
debug3: Normalising mapped IPv4 in IPv6 address
Connection from 139.18.9.23 port 4381
debug1: Client protocol version 2.0; client software version
OpenSSH_3.8.1p1 Debian-8.sarge.6 debug1: match: OpenSSH_3.8.1p1
Debian-8.sarge.6 pat OpenSSH_3.* debug1: Enabling compatibility mode
for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_4.3p2
Debian-8 debug2: fd 3 setting O_NONBLOCK
debug3: privsep user:group 103:65534
debug1: permanently_set_uid: 103/65534
debug1: list_hostkey_types: ssh-rsa,ssh-dss
debug1: SSH2_MSG_KEXINIT sent
debug2: Network child is on pid 4713
debug3: preauth child monitor started
debug3: mm_request_receive entering