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I have a customized Debian (built with debootstrap)

Linux debian 4.9.0-4-686 #1 SMP Debian 4.9.51-1 (2017-09-28) i686 GNU/Linux

with read-only file system

Here is the tunnel config (it works perfectly on a classical installation)

Host *
#   ForwardAgent no
#   ForwardX11 no
#   ForwardX11Trusted yes
#   RhostsRSAAuthentication no
#   RSAAuthentication yes
   PasswordAuthentication yes
#   HostbasedAuthentication no
#   GSSAPIAuthentication no
#   GSSAPIDelegateCredentials no
#   GSSAPIKeyExchange no
#   GSSAPITrustDNS no
#   BatchMode no
   CheckHostIP yes
#   AddressFamily any
#   ConnectTimeout 0
#   StrictHostKeyChecking ask
#   IdentityFile ~/.ssh/identity
#   IdentityFile ~/.ssh/id_rsa
#   IdentityFile ~/.ssh/id_dsa
#   IdentityFile ~/.ssh/id_ecdsa
#   IdentityFile ~/.ssh/id_ed25519
#   Port 22
   Protocol 2
#   Cipher 3des
   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
#   MACs hmac-md5,hmac-sha1,[email protected],hmac-ripemd160
#   EscapeChar ~
   Tunnel yes
#   TunnelDevice any:any
#   PermitLocalCommand no
#   VisualHostKey no
#   ProxyCommand ssh -q -W %h:%p gateway.example.com
#   RekeyLimit 1G 1h
    SendEnv LANG LC_*
    HashKnownHosts yes

I mount the tunnel:

ssh -ND 1080 -vvv -p 443 user@server 

the output looks fine:

OpenSSH_7.4p1 Debian-10+deb9u1, OpenSSL 1.0.2l  25 May 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "xxxx" port 443
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to xxxxx [xxxx] port 443.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: SELinux support disabled
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
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_7.4p1 Debian-10+deb9u1
debug1: Remote protocol version 2.0, remote software version dropbear_2012.55
debug1: no match: dropbear_2012.55
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to xxxxxxx:443 as 'xxxxxxx'
debug3: put_host_port: [xxxxxxxx]:443
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
debug2: ciphers stoc: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: diffie-hellman-group1-sha1,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,ssh-dss
debug2: ciphers ctos: aes128-ctr,3des-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes256-cbc,twofish256-cbc,twofish-cbc,twofish128-cbc
debug2: ciphers stoc: aes128-ctr,3des-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes256-cbc,twofish256-cbc,twofish-cbc,twofish128-cbc
debug2: MACs ctos: hmac-sha1-96,hmac-sha1,hmac-md5
debug2: MACs stoc: hmac-sha1-96,hmac-sha1,hmac-md5
debug2: compression ctos: zlib,[email protected],none
debug2: compression stoc: zlib,[email protected],none
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: diffie-hellman-group14-sha1
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha1 compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha1 compression: none
debug1: sending SSH2_MSG_KEXDH_INIT
debug2: bits set: 1024/2048
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEXDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ssh-rsa SHA256:k5AHnNs87cyG5my8AcjKp6KY1tWUeGIH2b3ZWALCsnU
debug3: put_host_port: [xxx.xxx.xx.xx]:443
debug3: put_host_port: [xxxxxxxxxxx]:443
debug1: checking without port identifier
The authenticity of host '[xxxxxx]:443 ([xxx.xxx.xx.xx]:443)' can't be established.
RSA key fingerprint is SHA256:k5AHnNs87cyG5my8AcjKp6KY1tWUeGIH2b3ZWALCsnU.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[xxxxxx]:443,[xxxxxx]:443' (RSA) to the list of known hosts.
debug2: bits set: 999/2048
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 4294967296 blocks
debug2: key: /root/.ssh/id_rsa ((nil))
debug2: key: /root/.ssh/id_dsa ((nil))
debug2: key: /root/.ssh/id_ecdsa ((nil))
debug2: key: /root/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 53
debug3: input_userauth_banner
+++++++++xxxxxxxxx+++++++++
* No Reupload and Repost Your Account   
* No DDOS
* No Hacking
* No Torrent
* No Fraud
* No Spam etc.
You are allowed a maximum of 3 Bitvise for using SSH account!!
Don't forget to support us!! xxxxxxxx
+++++++++XXXXXXXXXX+++++++++
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
debug3: preferred gssapi-keyex,gssapi-with-mic,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: /root/.ssh/id_rsa
debug3: no such identity: /root/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /root/.ssh/id_dsa
debug3: no such identity: /root/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /root/.ssh/id_ecdsa
debug3: no such identity: /root/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /root/.ssh/id_ed25519
debug3: no such identity: /root/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
xxxxxxxxx password: 
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (password).
Authenticated to xxxxx ([xxxxx]:443).
debug1: Local connections to LOCALHOST:1080 forwarded to remote address socks:0
debug3: channel_setup_fwd_listener_tcpip: type 2 wildcard 0 addr NULL
debug1: Local forwarding listening on 127.0.0.1 port 1080.
debug2: fd 4 setting O_NONBLOCK
debug3: fd 4 is O_NONBLOCK
debug1: channel 0: new [port listener]
debug3: sock_set_v6only: set socket 5 IPV6_V6ONLY
debug1: Local forwarding listening on ::1 port 1080.
bind: Cannot assign requested address
debug1: Requesting tun unit 2147483647 in mode 1
debug1: sys_tun_open: tunnel mode 1 fd 5
debug2: fd 5 setting O_NONBLOCK
debug3: fd 5 is O_NONBLOCK
debug1: channel 1: new [tun]
debug3: send packet: type 90
debug2: fd 3 setting TCP_NODELAY
debug3: ssh_packet_set_tos: set IP_TOS 0x10
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 92
channel 1: open failed: unknown channel type: 
debug2: channel 1: zombie
debug2: channel 1: garbage collecting
debug1: channel 1: free: tun, nchannels 2
debug3: channel 1: status: The following connections are open:

# lsof -i :1080
COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
ssh     3937 root    4u  IPv4  60066      0t0  TCP localhost:socks (LISTEN)

#netstat -ltpe 
tcp        0      0 127.0.0.1:1080          0.0.0.0:*               LISTEN      3937/ssh            
tcp        0      0 192.168.1.29:40112      xxx.xxx.xx.xx:443       ESTABLISHED 3937/ssh 

then I configured firefox-esr (the new name for iceweasel in Debian) to use the newly created proxy: Manual proxy configuration http proxy,ssl proxy,ftp proxy = cleared 'use this proxy for all protocols' = cleared. socks host 127.0.0.1 port 1080 No proxy for localhost, 127.0.0.1

Then when doing http request nothing happens (the browser just hangs). I try tor (configured with Socks5Proxy 127.0.0.1:1080), it does the same thing the ssh tunnel does not say anything (no output in verbose mode)

tcpdump -i wlp2s0 port 1080

-> no traffic at all then I try:

nc 127.0.0.1 1080

-> nothing happens

last test, but I am not sure it is relevant: I kill the tunnel and do:

nc -l -p 1080 

netstat says:

Proto Recv-Q Send-Q Local Address           Foreign Address         State       User       Inode      PID/Program name    
tcp        0      0 0.0.0.0:socks           0.0.0.0:*               LISTEN      root       65776      3985/nc  



nc 127.0.0.1 1080 

-> nothing happens

iptables is empty:

# iptables -L 
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination  

conclusion: it looks like the issue is not due to ssh or the Browser, but maybe the socket (?).

I am stuck from there.

Thanks for your help folks! I do need this to be working!

1 Answer 1

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I think it has to do with your read-only settings somehow preventing your lo interface to be up. This test matches the symptoms:

root@stretch-amd64:~# ip link set lo down
root@stretch-amd64:~# tcpdump -n -i lo
tcpdump: lo: That device is not up
root@stretch-amd64:~# nc -l -p 1080

You just looked at the wrong interface. lo is used for localhost (and would also be used for any local connection whatever the ip).

on a second terminal:

root@stretch-amd64:~# nc -w 5 -v -n 127.0.0.1 1080
nc: connect to 127.0.0.1 port 1080 (tcp) timed out: Operation now in progress

first terminal again:

ip link set lo up
nc -l -p 1080

2nd terminal again:

root@stretch-amd64:~# nc -w 5 -v -n 127.0.0.1 1080
Connection to 127.0.0.1 1080 port [tcp/*] succeeded!

Verify that /etc/network/interfaces got this entry or add it:

auto lo
iface lo inet loopback

If it's there, I can only think that ifup didn't work because of the read-only system. Have a script that can run ip link set lo up anywhere at boot.

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  • The tunnel was not working because lo iface was down. Thank you.
    – achille
    Commented Oct 19, 2017 at 8:09

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