Dropbear ssh tunneling segfault

[Hayk Beglaryan]

Hello,

I'm an android developer and we are trying to make a ssh tunneling between Android device and Linux Host. I'm using dropbear for this solution.

Here is my steps:
 
1) I'm connecting to my host via dbclient with 0 port

    dbclient -i "$RSA_KEY" -f -N -R 0:localhost:22 "$HOST" -y &> /sdcard/out

2) Then I'm running dropbear 

    dropbear -E -R

3) And now I'm able to connect to device via ssh from my host using public key and port in /sdcard/out 

    ssh -i ssh_rsa_key root at localhost -p 50216

Here is it, and it's works perfectly.
For my solution I need to make tunneling automatically. 

I have created bash script under /system/bin/ (build android image with script in it). Added corresponding service in init.rc to run my script automatically. 

     service myScript /system/bin/myScript
          class core
          user root
          group root
          disabled

The script actually runs by system every 5 sec. but when I'm trying to connect to device I receive following error message:

    "Aiee, segfault! You should probably report this as a bug to the developer"

The strangest thing is that when I'm running my script manually it works fine but when system runs the **same** script I receive upper described error message.

"dmesg", "logcat", even "ssh ... -vvv" don't give any error message.

I think problem is in "dropbear" itself, because when system runs "dbclient" and then I run "dropbear -E -R" manually , tunneling works correctly. 

This is my output of "ssh ... -v"


      OpenSSH_7.6p1, LibreSSL 2.6.2
      debug1: Reading configuration data /etc/ssh/ssh_config
      debug1: /etc/ssh/ssh_config line 48: Applying options for *
      debug1: Connecting to localhost port 50643.
      debug1: Connection established.
      debug1: key_load_public: No such file or directory
      debug1: identity file ssh_rsa_key_to_box type -1
      debug1: key_load_public: No such file or directory
      debug1: identity file ssh_rsa_key_to_box-cert type -1
      debug1: Local version string SSH-2.0-OpenSSH_7.6
      debug1: Remote protocol version 2.0, remote software version dropbear_2017.75
      debug1: no match: dropbear_2017.75
      debug1: Authenticating to localhost:50643 as 'root'
      debug1: SSH2_MSG_KEXINIT sent
      debug1: SSH2_MSG_KEXINIT received
      debug1: kex: algorithm: curve25519-sha256 at libssh.org
      debug1: kex: host key algorithm: ssh-rsa
      debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha2-256 compression: none
      debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha2-256 compression: none
      debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
      debug1: Server host key: ssh-rsa SHA256:M1PmvueMNfm4q47UlzVWZMdB6YzxyYBy4I5hden9ctU
      debug1: Host '[localhost]:50643' is known and matches the RSA host key.
      debug1: Found key in /Users/haykbeglaryan/.ssh/known_hosts:23
      debug1: rekey after 4294967296 blocks
      debug1: SSH2_MSG_NEWKEYS sent
      debug1: expecting SSH2_MSG_NEWKEYS
      debug1: SSH2_MSG_NEWKEYS received
      debug1: rekey after 4294967296 blocks
      debug1: SSH2_MSG_SERVICE_ACCEPT received
      debug1: Authentications that can continue: publickey
      debug1: Next authentication method: publickey
      debug1: Trying private key: ssh_rsa_key_to_box
      debug1: Authentication succeeded (publickey).
      Authenticated to localhost ([::1]:50643).
      debug1: channel 0: new [client-session]
      debug1: Entering interactive session.
      debug1: pledge: network
      debug1: Sending environment.
      debug1: Sending env LC_CTYPE = UTF-8
      debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
      Aiee, segfault! You should probably report this as a bug to the developer
      debug1: channel 0: free: client-session, nchannels 1
      debug1: fd 1 clearing O_NONBLOCK
      Connection to localhost closed.
      Transferred: sent 2640, received 1816 bytes, in 0.0 seconds
      Bytes per second: sent 312354.4, received 214861.9
      debug1: Exit status 1


Best regards:
— 
Hayk Beglaryan, Software developer
Mobile: +374 (41) 550 309