SFTP connection error with JSch: SSH_MSG_DISCONNECT: 11 Internal server error

java ssh sftp jsch vfs
2Big2BeSmall picture 2Big2BeSmall · Mar 18, 2018 · Viewed 7.2k times · Source

I was trying to retrieve a file from SFTP server - while connecting to this SFTP works with FileZilla - SFTP method.

For JSch I have tried this code using JSch 

JSch jsch = new JSch();
Properties config = new Properties();
config.put("StrictHostKeyChecking", "no");
config.put("PreferredAuthentications", "password");
Session session = jsch.getSession( "super_robot", "192.192.192.com", 6222 );
session.setConfig(config );
session.setPassword( "a1234!X@" );
session.connect( 30000 );

Though I got this error:

Caused by: com.jcraft.jsch.JSchException: SSH_MSG_DISCONNECT: 11 Internal server error. 
    at com.jcraft.jsch.Session.read(Session.java:1004)
    at com.jcraft.jsch.Session.connect(Session.java:323)

With StandardFileSystemManager I'm also having the same error:

SftpFileSystemConfigBuilder.getInstance().setTimeout(opts, connectionTimeout);
SftpFileSystemConfigBuilder.getInstance().setIdentityInfo(opts);

SftpFileSystemConfigBuilder.getInstance().setStrictHostKeyChecking(opts, "no");
StandardFileSystemManager fsManager = new StandardFileSystemManager();
fsManager.init();

Got me this error:

Caused by: org.apache.commons.vfs2.FileSystemException: Could not connect to SFTP server at "digital.crossix.com".
    at org.apache.commons.vfs2.provider.sftp.SftpClientFactory.createConnection(SftpClientFactory.java:147)
    at org.apache.commons.vfs2.provider.sftp.SftpFileProvider.doCreateFileSystem(SftpFileProvider.java:79)
    ... 40 more
Caused by: com.jcraft.jsch.JSchException: SSH_MSG_DISCONNECT: 11 Internal server error. 
    at com.jcraft.jsch.Session.read(Session.java:1004)
    at com.jcraft.jsch.Session.connect(Session.java:323)
    at com.jcraft.jsch.Session.connect(Session.java:183)
    at org.apache.commons.vfs2.provider.sftp.SftpClientFactory.createConnection(SftpClientFactory.java:145)
    ... 41 more

I have tried other solution offered in these links which didn't solve it:

Note that none of these errors is exactly the same as the error I'm facing - they are a bit similar. Didn't found someone that had the exact error I'm facing.

When I was working with FileZilla this is the log I was seeing in console:

Status: Connecting to 192.192.com:6222...
Trace:  CControlSocket::SendNextCommand()
Trace:  CSftpConnectOpData::Send() in state 0
Trace:  Going to execute C:\Program Files\FileZilla FTP Client\fzsftp.exe
Response:   fzSftp started, protocol_version=8
Trace:  CSftpConnectOpData::ParseResponse() in state 0
Trace:  CControlSocket::SendNextCommand()
Trace:  CSftpConnectOpData::Send() in state 3
Command:    open "[email protected]" 6222
Trace:  Connecting to 192.192.194 port 6222
Trace:  We claim version: SSH-2.0-FileZilla_3.30.0
Trace:  Server version: SSH-2.0-NuaneSSH_0.8.1.0
Trace:  Using SSH protocol version 2
Trace:  Doing Diffie-Hellman group exchange
Trace:  Doing Diffie-Hellman key exchange with hash SHA-1
Trace:  Server also has ssh-dss host key, but we don't know it
Trace:  Host key fingerprint is:
Trace:  ssh-rsa 1024 ------------------------------------
Command:    Trust new Hostkey: Once
Trace:  Initialised AES-256 CBC client->server encryption
Trace:  Initialised HMAC-SHA1 client->server MAC algorithm
Trace:  Initialised AES-256 CBC server->client encryption
Trace:  Initialised HMAC-SHA1 server->client MAC algorithm
Trace:  Attempting keyboard-interactive authentication
Trace:  Using keyboard-interactive authentication. inst_len: 0, num_prompts: 1
Command:    Pass: ********
Trace:  Access granted
Trace:  Opening session as main channel
Trace:  Opened main channel
Trace:  Started a shell/command
Status: Connected to 192.192.com
Trace:  CSftpConnectOpData::ParseResponse() in state 3
Trace:  CControlSocket::ResetOperation(0)
Trace:  CSftpConnectOpData::Reset(0) in state 3
Trace:  CFileZillaEnginePrivate::ResetOperation(0)
Status: Retrieving directory listing...
Trace:  CControlSocket::SendNextCommand()
Trace:  CSftpListOpData::Send() in state 0
Trace:  CSftpChangeDirOpData::Send() in state 0
Trace:  CSftpChangeDirOpData::Send() in state 1
Command:    pwd
Response:   Current directory is: "/"
Trace:  CSftpChangeDirOpData::ParseResponse() in state 1
Trace:  CControlSocket::ResetOperation(0)
Trace:  CControlSocket::ParseSubcommandResult(0)
Trace:  CSftpListOpData::SubcommandResult() in state 1
Trace:  CControlSocket::SendNextCommand()
Trace:  CSftpListOpData::Send() in state 2
Trace:  CSftpListOpData::Send() in state 3
Command:    ls
Status: Listing directory /
Trace:  CSftpListOpData::ParseResponse() in state 3
Trace:  CControlSocket::ResetOperation(0)
Status: Directory listing of "/" successful
Trace:  CFileZillaEnginePrivate::ResetOperation(0)

What can I do to solve this error?

Attaching also the log from JSch

INFO: Connection established
INFO: Remote version string: SSH-2.0-NuaneSSH_0.8.1.0
INFO: Local version string: SSH-2.0-JSCH-0.1.54
INFO: CheckCiphers: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,3des-ctr,arcfour,arcfour128,arcfour256
INFO: aes256-ctr is not available.
INFO: aes192-ctr is not available.
INFO: aes256-cbc is not available.
INFO: aes192-cbc is not available.
INFO: CheckKexes: diffie-hellman-group14-sha1,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521
INFO: CheckSignatures: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
INFO: SSH_MSG_KEXINIT sent
INFO: SSH_MSG_KEXINIT received
INFO: kex: server: diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
INFO: kex: server: ssh-rsa,ssh-dss
INFO: kex: server: aes256-cbc,aes192-cbc,aes128-cbc,3des-cbc
INFO: kex: server: aes256-cbc,aes192-cbc,aes128-cbc,3des-cbc
INFO: kex: server: hmac-sha1,hmac-md5
INFO: kex: server: hmac-sha1,hmac-md5

INFO: kex: client: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
INFO: kex: client: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
INFO: kex: client: aes128-ctr,aes128-cbc,3des-ctr,3des-cbc,blowfish-cbc
INFO: kex: client: aes128-ctr,aes128-cbc,3des-ctr,3des-cbc,blowfish-cbc
INFO: kex: client: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha1-96,hmac-md5-96
INFO: kex: client: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha1-96,hmac-md5-96

INFO: kex: server->client aes128-cbc hmac-md5 none
INFO: kex: client->server aes128-cbc hmac-md5 none
INFO: SSH_MSG_KEXDH_INIT sent
INFO: expecting SSH_MSG_KEXDH_REPLY
INFO: Disconnecting from 192.192.com port 6222

Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.CommandLineWrapper.main(CommandLineWrapper.java:65)
Caused by: com.jcraft.jsch.JSchException: SSH_MSG_DISCONNECT: 11 Internal server error. 
    at com.jcraft.jsch.Session.read(Session.java:1004)
    at com.jcraft.jsch.Session.connect(Session.java:323)
    at com.xxxxxxx.yyyy.service.SFTPTest.main(SFTPProviderTest.java:50)
    ... 5 more

Answer

Martin Prikryl picture Martin Prikryl · Mar 19, 2018

Seems like a bug or problem on the server. Check server-side log file.

Though note that FileZilla succeeds to connect with a use of "AES-256 CBC". Your JSch code uses only "AES-128 CBC", because "AES-256 CBC" is not available.

Try installing JCE to enable "AES-256 CBC". See JSch Algorithm negotiation fail.

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