How to Reverse SSH from Shell Script - linux

Question

Good afternoon,
I am trying to establish a reverse SSH connection using a shell script.
Below is my calling command, from client to host, and back to client: (important data is replaced with xxxxxx)
ssh -o StrictHostKeyChecking=no -o ConnectTimeout=15 -R 19999:localhost:22 admin#xx.xxx.xx.xx -v "sshpass -p xxxxxxx ssh -f -N -q -L 0.0.0.0:81:localhost:80 root#localhost -p 19999"
Show Below are the Output from SSH and from Netstat commands
The connection does show up on Netstat unfortunately, it shows up as TIME_WAIT instead of ESTABLISHED and I cannot access port 80 on client from another machine (by accessing port 81 on host)
Is this the correct way to establish Reverse SSH connection without having to type anything on the host?
If I run the two commands manually
ssh -o StrictHostKeyChecking=no -o ConnectTimeout=15 -R 19999:localhost:22 dmin#xx.xxx.xx.xx -v
and
sshpass -p xxxxxxx ssh -f -N -q -L 0.0.0.0:81:localhost:80 root#localhost -p 19999
Everything work, Once it's connected to the host, I do not have any problems, however I cannot do it this way from a script file.
EDIT: I tried different combinations of using -f -N and -q on the client and the host portion of the commands, but I haven't had any successful results. The best I've gotten was to display the client's firmware welcome message
Netstat output after the command was executed:
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 xxx.xxxxxxxxx.myvzw.com:xxxx xxxx.us-west-1.compute.xxxxx.com:ssh TIME_WAIT
tcp 0 0 localhost:49553 localhost:ssh TIME_WAIT
udp 0 0 xxx.xxxxxxxxx.myvzw.com:xxxx xxxxxxx:ntp ESTABLISHED
Active UNIX domain sockets (w/o servers)
Debug Output from top SSH command
OpenSSH_6.6, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to xx.xxx.xxx.xx [xx.xxx.xxx.xx] port 22.
debug1: fd 3 clearing O_NONBLOCK
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.0p1 Debian-4
debug1: match: OpenSSH_6.0p1 Debian-4 pat OpenSSH* compat 0x04000000
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ECDSA xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx
debug1: Host 'xx:xxx:xxx:xx' is known and matches the ECDSA host key.
debug1: Found key in /root/.ssh/known_hosts:5
debug1: ssh_ecdsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /root/.ssh/id_rsa
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
Authenticated to xx:xxx:xxx:xx ([xx:xxx:xxx:xx]:22).
debug1: Remote connections from LOCALHOST:19999 forwarded to local address localhost:22
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions#openssh.com
debug1: Entering interactive session.
debug1: remote forward success for: listen 19999, connect localhost:22
debug1: All remote forwarding requests processed
debug1: Sending command: sleep 5; sshpass -p xxxxxxx ssh -f -N -q -L 0.0.0.0:1195:localhost:1194 root#localhost -p 19999
debug1: client_input_channel_open: ctype forwarded-tcpip rchan 3 win 2097152 max 32768
debug1: client_request_forwarded_tcpip: listen localhost port 19999, originator ::1 port 38767
debug1: connect_next: host localhost ([127.0.0.1]:22) in progress, fd=7
debug1: channel 1: new [::1]
debug1: confirm forwarded-tcpip
debug1: channel 1: connected to localhost port 22
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype eow#openssh.com reply 0
debug1: channel 0: free: client-session, nchannels 2
debug1: channel 1: free: ::1, nchannels 1
Transferred: sent 4768, received 4176 bytes, in 10.4 seconds
Bytes per second: sent 459.7, received 402.6
debug1: Exit status 0
Thank you,

Answer 1

I seem to have been able to establish a reverse connection by applying some "sleep" commands
Below is my command
ssh -o StrictHostKeyChecking=no -o ConnectTimeout=15 -f -R 19999:localhost:22 admin#XX.XXX.XXX.XX -v "sleep 5; sshpass -p XXXXXX ssh -L 0.0.0.0:81:localhost:81 root#localhost -p 19999 -v \"sleep 120\" sleep 120"
So basically I am putting the ssh process to sleep before finishing the second connection and placing the second connection to sleep right afterwards.
Interestingly enough, the connection doesn't cease after 120 seconds, it stays up. If someone would be kind enough to explain why this works, or if there is a better method, please reply
Thanks