SSH under chroot, kernel with enabled grsecurity. (opentty problem ?)

[Marcin Grinberg]

Hello,

I'm trying to fix this problem for a while (month probably). I'm not
able to find an solution via google. If someone could help me out I
would appreciate.

Screenplay:

I'm starting server under chroot with /proc and /dev/pts mounted.
Everything is fine, clients can connect to the server.
After a while (approx 24h) "something" is happening and server rejects
connections.

output(-vvv enabled):
OpenSSH_5.2p1, OpenSSL 0.9.8l 5 Nov 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: ssh_connect: needpriv 0
debug1: Connecting to ***.***.***.*** port 22.
debug1: Connection established.
debug1: identity file /home/user/.ssh/identity type -1
debug1: identity file /home/user/.ssh/id_rsa type -1
debug1: identity file /home/user/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.2
debug1: match: OpenSSH_5.2 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.2
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit:
diffie-hellman-group-exchange-sha256,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-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-***@lysator.liu.se
debug2: kex_parse_kexinit:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-***@lysator.liu.se
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,umac-***@openssh.com,hmac-ripemd160,hmac-***@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,umac-***@openssh.com,hmac-ripemd160,hmac-***@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,***@openssh.com,zlib
debug2: kex_parse_kexinit: none,***@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-group-exchange-sha256,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-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-***@lysator.liu.se
debug2: kex_parse_kexinit:
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-***@lysator.liu.se
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,umac-***@openssh.com,hmac-ripemd160,hmac-***@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit:
hmac-md5,hmac-sha1,umac-***@openssh.com,hmac-ripemd160,hmac-***@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,***@openssh.com
debug2: kex_parse_kexinit: none,***@openssh.com
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug2: dh_gen_key: priv key bits set: 137/256
debug2: bits set: 495/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: check_host_in_hostfile: filename /home/user/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 2
debug1: Host '***.***.***.***' is known and matches the RSA host key.
debug1: Found key in /home/user/.ssh/known_hosts:2
debug2: bits set: 526/1024
debug1: ssh_rsa_verify: signature correct
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: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/user/.ssh/identity ((nil))
debug2: key: /home/user/.ssh/id_rsa ((nil))
debug2: key: /home/user/.ssh/id_dsa ((nil))
debug1: Authentications that can continue:
publickey,password,keyboard-interactive
debug3: start over, passed a different list
publickey,password,keyboard-interactive
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: /home/user/.ssh/identity
debug3: no such identity: /home/user/.ssh/identity
debug1: Trying private key: /home/user/.ssh/id_rsa
debug3: no such identity: /home/user/.ssh/id_rsa
debug1: Trying private key: /home/user/.ssh/id_dsa
debug3: no such identity: /home/user/.ssh/id_dsa
debug2: we did not send a packet, disable method
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug2: we sent a keyboard-interactive packet, wait for reply
debug1: Authentications that can continue:
publickey,password,keyboard-interactive
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred:
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
user@***.***.***.***'s password:
debug3: packet_send2: adding 48 (len 61 padlen 19 extra_pad 64)
debug2: we sent a password packet, wait for reply
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Requesting no-more-***@openssh.com
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug2: channel 0: request shell confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i0/0 o0/0 fd 4/5 cfd -1)

debug3: channel 0: close_fds r 4 w 5 e 6 c -1
Connection to ***.***.***.*** closed by remote host.
Connection to ***.***.***.*** closed.
Transferred: sent 1712, received 1864 bytes, in 0.0 seconds
Bytes per second: sent 69715.3, received 75904.9
debug1: Exit status -1


On the server in logs I have:
Mar 29 06:59:25 localhost sshd_ch[15900]: Accepted password for user
from ***.***.***.*** port 58520 ssh2
Mar 29 06:59:25 localhost sshd_ch[15900]: fatal: openpty returns
device for which ttyname fails.
Mar 29 06:59:25 localhost sshd_ch[15900]: syslogin_perform_logout:
logout() returned an error
Mar 29 06:59:25 localhost sshd_ch[15900]: error: chown  0 0 failed: No
such file or directory
Mar 29 06:59:25 localhost sshd_ch[15900]: error: chmod  0666 failed:
No such file or directory
Mar 29 06:59:35 localhost sshd_ch[15905]: Accepted password for user
from ***.***.***.*** port 58521 ssh2
Mar 29 06:59:35 localhost sshd_ch[15905]: fatal: openpty returns
device for which ttyname fails.
Mar 29 06:59:35 localhost sshd_ch[15905]: syslogin_perform_logout:
logout() returned an error
Mar 29 06:59:35 localhost sshd_ch[15905]: error: chown  0 0 failed: No
such file or directory
Mar 29 06:59:35 localhost sshd_ch[15905]: error: chmod  0666 failed:
No such file or directory

I really would like to run this server correctly...
Let me know if any further information is needed.

Thanks in advance.
Marcin Grinberg

[Jan Pechanec]

Post by Marcin Grinberg
Hello,
I'm trying to fix this problem for a while (month probably). I'm not
able to find an solution via google. If someone could help me out I
would appreciate.

Marcin, I don't think this is a problem in OpenSSH. It just
tries to get a new PTY and it fails. What's more, it works for some
time, the problem seems to be in the system itself.

you can keep an open connection to the system. When the new
connection fails, you can try to debug on the remote side why a new PTY
cannot be allocated.

J.

Post by Marcin Grinberg
I'm starting server under chroot with /proc and /dev/pts mounted.
Everything is fine, clients can connect to the server.
After a while (approx 24h) "something" is happening and server rejects
connections.
OpenSSH_5.2p1, OpenSSL 0.9.8l 5 Nov 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: ssh_connect: needpriv 0
debug1: Connecting to ***.***.***.*** port 22.
debug1: Connection established.
debug1: identity file /home/user/.ssh/identity type -1
debug1: identity file /home/user/.ssh/id_rsa type -1
debug1: identity file /home/user/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.2
debug1: match: OpenSSH_5.2 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.2
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
diffie-hellman-group-exchange-sha256,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: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
diffie-hellman-group-exchange-sha256,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: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug2: dh_gen_key: priv key bits set: 137/256
debug2: bits set: 495/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: check_host_in_hostfile: filename /home/user/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 2
debug1: Host '***.***.***.***' is known and matches the RSA host key.
debug1: Found key in /home/user/.ssh/known_hosts:2
debug2: bits set: 526/1024
debug1: ssh_rsa_verify: signature correct
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: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/user/.ssh/identity ((nil))
debug2: key: /home/user/.ssh/id_rsa ((nil))
debug2: key: /home/user/.ssh/id_dsa ((nil))
publickey,password,keyboard-interactive
debug3: start over, passed a different list
publickey,password,keyboard-interactive
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: /home/user/.ssh/identity
debug3: no such identity: /home/user/.ssh/identity
debug1: Trying private key: /home/user/.ssh/id_rsa
debug3: no such identity: /home/user/.ssh/id_rsa
debug1: Trying private key: /home/user/.ssh/id_dsa
debug3: no such identity: /home/user/.ssh/id_dsa
debug2: we did not send a packet, disable method
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug2: we sent a keyboard-interactive packet, wait for reply
publickey,password,keyboard-interactive
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
debug3: packet_send2: adding 48 (len 61 padlen 19 extra_pad 64)
debug2: we sent a password packet, wait for reply
debug1: Authentication succeeded (password).
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug2: channel 0: request shell confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug1: channel 0: free: client-session, nchannels 1
  #0 client-session (t4 r0 i0/0 o0/0 fd 4/5 cfd -1)
debug3: channel 0: close_fds r 4 w 5 e 6 c -1
Connection to ***.***.***.*** closed by remote host.
Connection to ***.***.***.*** closed.
Transferred: sent 1712, received 1864 bytes, in 0.0 seconds
Bytes per second: sent 69715.3, received 75904.9
debug1: Exit status -1
Mar 29 06:59:25 localhost sshd_ch[15900]: Accepted password for user
from ***.***.***.*** port 58520 ssh2
Mar 29 06:59:25 localhost sshd_ch[15900]: fatal: openpty returns
device for which ttyname fails.
logout() returned an error
Mar 29 06:59:25 localhost sshd_ch[15900]: error: chown  0 0 failed: No
such file or directory
No such file or directory
Mar 29 06:59:35 localhost sshd_ch[15905]: Accepted password for user
from ***.***.***.*** port 58521 ssh2
Mar 29 06:59:35 localhost sshd_ch[15905]: fatal: openpty returns
device for which ttyname fails.
logout() returned an error
Mar 29 06:59:35 localhost sshd_ch[15905]: error: chown  0 0 failed: No
such file or directory
No such file or directory
I really would like to run this server correctly...
Let me know if any further information is needed.
Thanks in advance.
Marcin Grinberg