weird issues with DH Group1 key exchange

[Greg Swallow]

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Hi,

We recently upgraded to OpenSSH 4.2p1 with the chroot patch supplied on
sourceforge.  Since then, we've noticed odd problems with random client
failures.  Today I wrote little scripts to keep restarting sshd with the
- -ddd flag and finally captured what's going on, I believe.

First, openssh is compiled as so:

OpenSSH_4.2p1, OpenSSL 0.9.8a

configured by ./configure, generated by GNU Autoconf 2.59,
  with options \"'--prefix=/usr/local' '--with-audit=bsm'
'--with-md5-passwords' '--with-kerberos5=/opt/krb5'
'--with-ssl-dir=/usr/local' '--with-zlib'\"

Then we have Net::SSH and Eclipse failing on us randomly (although with
alarming frequency).  Net::SSH version 1.23; Eclipse I have no idea.

What happens on the client side is:

bart: Reading configuration data /web/etc/noaccess/.ssh/config
bart: Reading configuration data /etc/ssh_config
bart: Connecting to eliza.ai.org, port 22.
bart: Remote protocol version 2.0, remote software version
OpenSSH_4.2-chrootsshbart: Net::SSH::Perl Version 1.23, protocol version
2.0.
bart: No compat match: OpenSSH_4.2-chrootssh.
bart: Connection established.
bart: Sent key-exchange init (KEXINIT), wait response.
bart: Algorithms, c->s: 3des-cbc hmac-sha1 none
bart: Algorithms, s->c: 3des-cbc hmac-sha1 none
bart: Entering Diffie-Hellman Group 1 key exchange.
bart: Sent DH public key, waiting for reply.
Connection closed by remote host. at
/usr1/local/lib/perl5/site_perl/5.6.1/Net/SSH/Perl/Kex/DH1.pm line 38

What happens on the server side is:

debug2: load_server_config: filename /usr/local/etc/sshd_config.private
debug2: load_server_config: done config len = 439
debug2: parse_server_config: config /usr/local/etc/sshd_config.private
len 439
debug1: sshd version OpenSSH_4.2-chrootsshp1
debug3: Not a RSA1 key file /usr/local/etc/ssh_host_key.
debug1: read PEM private key done: type RSA
debug1: private host key: #0 type 1 RSA
debug3: Not a RSA1 key file /usr/local/etc/ssh_host_rsa_key.
debug1: read PEM private key done: type RSA
debug1: private host key: #1 type 1 RSA
debug3: Not a RSA1 key file /usr/local/etc/ssh_host_dsa_key.
debug1: read PEM private key done: type DSA
debug1: private host key: #2 type 2 DSA
Disabling protocol version 1. Could not load host key
debug1: rexec_argv[0]='/usr/local/sbin/sshd'
debug1: rexec_argv[1]='-f'
debug1: rexec_argv[2]='/usr/local/etc/sshd_config.private'
debug1: rexec_argv[3]='-ddd'
debug2: fd 4 setting O_NONBLOCK
debug1: Bind to port 22 on 10.8.54.105.
Server listening on 10.8.54.105 port 22.
debug1: fd 5 clearing O_NONBLOCK
debug1: Server will not fork when running in debugging mode.
debug3: send_rexec_state: entering fd = 10 config len 439
debug3: ssh_msg_send: type 0
debug3: send_rexec_state: done
debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 10
debug1: inetd sockets after dupping: 4, 4
Connection from 10.8.6.80 port 57334
debug1: Client protocol version 2.0; client software version 1.23
debug1: no match: 1.23
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_4.2-chrootssh
debug2: fd 4 setting O_NONBLOCK
debug3: privsep user:group 22:22
debug1: permanently_set_uid: 22/22
debug1: list_hostkey_types: ssh-rsa,ssh-rsa,ssh-dss
debug1: SSH2_MSG_KEXINIT sent
debug2: Network child is on pid 20240
debug3: preauth child monitor started
debug3: mm_request_receive entering
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit:
diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,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 at lysator.liu.se,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 at lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160 at openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160 at openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib at openssh.com,zlib
debug2: kex_parse_kexinit: none,zlib at openssh.com,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-group1-sha1
debug2: kex_parse_kexinit: ssh-dss,ssh-rsa
debug2: kex_parse_kexinit: 3des-cbc,blowfish-cbc,arcfour
debug2: kex_parse_kexinit: 3des-cbc,blowfish-cbc,arcfour
debug2: kex_parse_kexinit: hmac-sha1,hmac-md5
debug2: kex_parse_kexinit: hmac-sha1,hmac-md5
debug2: kex_parse_kexinit: none
debug2: kex_parse_kexinit: none
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-sha1
debug1: kex: client->server 3des-cbc hmac-sha1 none
debug2: mac_init: found hmac-sha1
debug1: kex: server->client 3des-cbc hmac-sha1 none
debug1: do_cleanup

Sometimes the server continues, but sometimes it just hangs up on me
here.  When it works, it continues:

debug2: dh_gen_key: priv key bits set: 178/384
debug2: bits set: 505/1024
debug1: expecting SSH2_MSG_KEXDH_INIT
debug2: bits set: 505/1024
debug3: mm_key_sign entering
debug3: mm_request_send entering: type 4
debug3: monitor_read: checking request 4
debug3: mm_answer_sign
debug3: mm_answer_sign: signature 103580(55)
debug3: mm_request_send entering: type 5
debug2: monitor_read: 4 used once, disabling now
debug3: mm_request_receive entering
debug3: mm_key_sign: waiting for MONITOR_ANS_SIGN
debug3: mm_request_receive_expect entering: type 5
debug3: mm_request_receive entering
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: KEX done
...

Help would be greatly appreciated.

- --
Greg Swallow
System Administrator, CCNA, CCSA
http://www.IN.gov
10 West Market St, Suite 600
Indianapolis, IN 46204
T. 317.233.2908
F. 317.233.2011
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