I have a remote machine (IP XX.XX.XX.XX) which runs an app written in python/cherrypy which opens a port for http connections on the loopback interface. If I login into the remote machine (using ssh) and then execute
curl http://127.0.0.1:8021 everything works ok. But, when I set up a tunnel from my local machine using
ssh -L 6868:XX.XX.XX.XX:8021 -fN XX.XX.XX.XX and then run
curl http://localhost:6868 or
curl http://127.0.0.1:6868 I get this message
curl: (52) Empty reply from server ssh shows this message in the terminal where I created the tunnel
channel 2: open failed: connect failed: Connection refused For testing, I changed the app to open the port on the real network interface (XX.XX.XX.XX instead of 127.0.0.1) and I used curl from another machine in the same remote network and it worked. Nevertheless, trying to create a tunnel between both remote machines yielded the same results as between a remote server and my local machine.
I've tried to make sure that the problem is not the firewall, so I ran
iptables -A INPUT -d 127.0.0.1/32 -i lo -j ACCEPT which I think is enough, but I'm not sure. Here is the ssh -v output
[____@YYYY ~]$ ssh -vvL 6868:XX.XX.XX.XX:8021 -fN XX.XX.XX.XX OpenSSH_5.4p1, OpenSSL 1.0.0-fips 29 Mar 2010 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to [XX.XX.XX.XX] port 22. debug1: Connection established. debug1: identity file /home/____/.ssh/id_rsa type -1 debug1: identity file /home/____/.ssh/id_rsa-cert type -1 debug1: identity file /home/____/.ssh/id_dsa type -1 debug1: identity file /home/____/.ssh/id_dsa-cert type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.4 debug1: match: OpenSSH_5.4 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.4 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: [email protected],[email protected],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,[email protected] 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,[email protected] debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected],zlib debug2: kex_parse_kexinit: none,[email protected],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,[email protected] 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,[email protected] debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96 debug2: kex_parse_kexinit: none,[email protected] debug2: kex_parse_kexinit: none,[email protected] 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: 117/256 debug2: bits set: 510/1024 debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Host 'XX.XX.XX.XX' is known and matches the RSA host key. debug1: Found key in /home/____/.ssh/known_hosts:5 debug2: bits set: 514/1024 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: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug2: service_accept: ssh-userauth debug1: SSH2_MSG_SERVICE_ACCEPT received debug2: key: /home/____/.ssh/id_rsa ((nil)) debug2: key: /home/____/.ssh/id_dsa ((nil)) debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password,hostbased debug1: Next authentication method: gssapi-with-mic debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_524' not found debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_524' not found debug1: Unspecified GSS failure. Minor code may provide more information debug2: we did not send a packet, disable method debug1: Next authentication method: publickey debug1: Trying private key: /home/____/.ssh/id_rsa debug1: Trying private key: /home/____/.ssh/id_dsa debug2: we did not send a packet, disable method debug1: Next authentication method: password [email protected]'s password: debug2: we sent a password packet, wait for reply debug1: Authentication succeeded (password). debug1: Local connections to LOCALHOST:6868 forwarded to remote address XX.XX.XX.XX:8021 debug1: Local forwarding listening on ::1 port 6868. debug2: fd 4 setting O_NONBLOCK debug1: channel 0: new [port listener] debug1: Local forwarding listening on 127.0.0.1 port 6868. debug2: fd 5 setting O_NONBLOCK debug1: channel 1: new [port listener] debug1: Requesting [email protected] debug1: Entering interactive session. debug1: Connection to port 6868 forwarding to XX.XX.XX.XX port 8021 requested. debug2: fd 6 setting TCP_NODELAY debug2: fd 6 setting O_NONBLOCK debug1: channel 2: new [direct-tcpip] channel 2: open failed: connect failed: Connection refused debug2: channel 2: zombie debug2: channel 2: garbage collecting debug1: channel 2: free: direct-tcpip: listening port 6868 for XX.XX.XX.XX port 8021, connect from 127.0.0.1 port 47048, nchannels 3 
