Invalid packet exception ssh'ing as root when "Please login as the ubuntu user rather than root user"

[aledsage]

I have an ubuntu VM that I'm trying to use with the following code:

   public static void main(String[] args) throws IOException {
      String privateKey = "<snip>";
      net.schmizz.sshj.SSHClient ssh = new net.schmizz.sshj.SSHClient();
      ssh.addHostKeyVerifier(new PromiscuousVerifier());
      ssh.connect("54.247.147.118", 22);

      OpenSSHKeyFile key = new OpenSSHKeyFile();
      key.init(privateKey, null);
      ssh.authPublickey("root", key);

      SFTPClient sftpClient = ssh.newSFTPClient();
   }

It gives me the error:

Exception in thread "main" java.lang.IllegalStateException: Invalid packet: indicated length 1349281121 too large
    at net.schmizz.sshj.sftp.PacketReader.readPacket(PacketReader.java:70)
    at net.schmizz.sshj.sftp.SFTPEngine.init(SFTPEngine.java:77)
    at net.schmizz.sshj.SSHClient.newSFTPClient(SSHClient.java:623)
    at org.jclouds.sshj.Main.main(Main.java:42)

---

Trying to ssh or scp to the machine at the command line with:

ssh -i my_id_rsa root@54.247.147.118

gives:

Please login as the ubuntu user rather than root user.
Connection to 54.247.147.118 closed.

It works when I ssh in as:

ssh -i my_id_rsa ubuntu@54.247.147.118

---

Is there some different behaviour of the ssh protocol in this situation?

[aledsage]

To get a suitable VM to reproduce, the jclouds code in [1] gives the error, as discussed in [2] and [3].

[1] https://gist.github.com/2489273
[2] https://groups.google.com/group/jclouds-dev/browse_thread/thread/c17d71019c7fc932/a3a990bb7c271efd?lnk=gst&q=sshj+hangs#a3a990bb7c271efd
[3] https://groups.google.com/group/jclouds/browse_thread/thread/ee6ba315102bb919

[shikhar]

Thanks for the report @aledsage , it's odd that there is different behaviour with the openssh client & with sshj. I will try to reproduce what's going on.

[shikhar]

Could you post what you get with

sftp -i my_id_rsa root@54.247.147.118

(sftp command instead of ssh)

[shikhar]

So I tried this out, even openssh sftp client bails out...

$ sftp -i sshjaws.pem root@xxxx.compute-1.amazonaws.com
Received message too long 1349281121

So it's not an sshj issue

[aledsage]

Confirmed I get the same with sftp -oIdentityFile=my_id_rsa root@54.247.147.118, gives:

Connecting to 54.247.147.118...
Received message too long 1349281121

[aledsage]

For the benefit of anyone searching for more information on this....

This link explains what's going on in openssh sftp: http://www.snailbook.com/faq/sftp-corruption.auto.html

The problem here is similar to if the underlying ssh command causes stdout (e.g. due to system or per-user shell startup files on the server). The text pollutes the protocol stream between scp2/sftp and sftp-server. The first four bytes of the text gets interpreted as a 32-bit packet length.

[shikhar]

That's a good explanation, thanks @aledsage

[stringaro-leo]

@aledsage '...(like fortune, echo "Hi there!", etc.)....' you saved me, thx