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问题:
I have this simple Java program that uses Jsch to connect to an SFTP server.
The connection fails with an "Auth fail" exception on Java 1.4.2, but it connects flawlessly on Java 1.7.
try { JSch jsch = new JSch(); jsch.setKnownHosts(KNOWN_HOSTS_PATH); jsch.addIdentity(PRIVATE_KEY_PATH, PASSPHRASE); Session session = jsch.getSession(USERNAME, HOSTNAME, 22); session.connect(2500); Channel channel = session.openChannel("shell"); channel.setInputStream(System. in ); channel.setOutputStream(System.out); channel.connect(); } catch (Exception e) { e.printStackTrace(System.err); }
The key I'm using is an ssh-rsa 4096 bit key. The .pub key file exists in the same directory as the private key.
When connecting a logger, I see the following messages before the exception (which occurs on channel.connect();):
INFO: Connecting to <redacted> port 22 INFO: Connection established INFO: Remote version string: SSH-2.0-OpenSSH_5.1p1 Debian-5 INFO: Local version string: SSH-2.0-JSCH-0.1.42 INFO: CheckCiphers: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,3des-ctr,arcfour,arcfour128,arcfour256 INFO: arcfour is not available. INFO: arcfour128 is not available. INFO: arcfour256 is not available. INFO: SSH_MSG_KEXINIT sent INFO: SSH_MSG_KEXINIT received INFO: kex: server->client aes128-ctr hmac-md5 none INFO: kex: client->server aes128-ctr hmac-md5 none INFO: SSH_MSG_KEXDH_INIT sent INFO: expecting SSH_MSG_KEXDH_REPLY INFO: ssh_rsa_verify: signature true INFO: Host '<redacted>' is known and mathces the RSA host key INFO: SSH_MSG_NEWKEYS sent INFO: SSH_MSG_NEWKEYS received INFO: SSH_MSG_SERVICE_REQUEST sent INFO: SSH_MSG_SERVICE_ACCEPT received INFO: Authentications that can continue: publickey,keyboard-interactive,password INFO: Next authentication method: publickey INFO: Authentications that can continue: password INFO: Next authentication method: password INFO: Disconnecting from <redacted> port 22 com.jcraft.jsch.JSchException: Auth fail at com.jcraft.jsch.Session.connect(Session.java:452) at TestJsch.main(TestJsch.java:19)
When I run the same program with Java 1.7, it says
INFO: Connecting to <redacted> port 22 INFO: Connection established INFO: Remote version string: SSH-2.0-OpenSSH_5.1p1 Debian-5 INFO: Local version string: SSH-2.0-JSCH-0.1.42 INFO: CheckCiphers: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,3des-ctr,arcfour,arcfour128,arcfour256 INFO: SSH_MSG_KEXINIT sent INFO: SSH_MSG_KEXINIT received INFO: kex: server->client aes128-ctr hmac-md5 none INFO: kex: client->server aes128-ctr hmac-md5 none INFO: SSH_MSG_KEXDH_INIT sent INFO: expecting SSH_MSG_KEXDH_REPLY INFO: ssh_rsa_verify: signature true INFO: Host '<redacted>' is known and mathces the RSA host key INFO: SSH_MSG_NEWKEYS sent INFO: SSH_MSG_NEWKEYS received INFO: SSH_MSG_SERVICE_REQUEST sent INFO: SSH_MSG_SERVICE_ACCEPT receivedINFO: Authentications that can continue: publickey,keyboard-interactive,password INFO: Next authentication method: publickey INFO: Authentication succeeded (publickey). Linux <redacted> 2.6.26-2-amd64 #1 SMP Mon Jun 13 16:29:33 UTC 2011 x86_64 <server welcome message follows>
I have installed the Java Cryptography Extensions (JCE) for the 1.4 VM.
What could be the source of that problem?
回答1:
Java has a limitation for using strong crypto algorithm. Check content of $JRE_HOME/lib/security/US_Export_policy.jar and $JRE_HOME/lib/security/local_policy.jar. If you find something like this:
// File: default_local.policy // Some countries have import limits on crypto strength. // This policy file is worldwide importable. grant { permission javax.crypto.CryptoPermission "DES", 64; permission javax.crypto.CryptoPermission "DESede", *; permission javax.crypto.CryptoPermission "RC2", 128, "javax.crypto.spec.RC2ParameterSpec", 128; permission javax.crypto.CryptoPermission "RC4", 128; permission javax.crypto.CryptoPermission "RC5", 128, "javax.crypto.spec.RC5ParameterSpec", *, 12, *; permission javax.crypto.CryptoPermission "RSA", 2048; permission javax.crypto.CryptoPermission *, 128; };
Decision is to download and install JCE Unlimited Strength Jurisdiction Policy. Previously, it was located on Sun's site, now I don't know where it can be found.
You can read more in this article
EDIT: After some research, I found my answer was incorrect.
Java 1.4 does not support RSA keys more than 2048 byte length BUG 4524097
回答2:
My problems with jsch have been around permissions. So i would do the following to eliminate them as problems
- Make sure you can ssh to the remote on the command line using the generated keys.
- Pass in the password and make sure you can get a connection to the remote.
- Check the permissions on the directory locally and on the remote good ssh summary.
- Try using the local host as a remote.
Failing that download the source code and step though it in a debug session.
回答3:
Have you tried using an Open SSH key? jsch uses Open SSH key formats. You can convert your existing one to an Open SSH format. This is how: Use putty keygen and load your existing key. You may be prompted to enter your password to decrypt it. After that click on the conversions option above and choose the "Export OpenSSH Key". Use this newly generated key in your program above. Hope this helps.
回答4:
This code works fine...
public class Exec2 { static String SSH_SERVER_PATH = "localhost"; static String SSH_SERVER_USERNAME = "root"; static String SSH_SERVER_PASSWORD = "root"; public static void main(String[] arg) { try { JSch jsch = new JSch(); String host = SSH_SERVER_PATH; String user = SSH_SERVER_USERNAME; Session session = jsch.getSession(user, host, 22); // username and password will be given via UserInfo interface. UserInfo ui = new MyUserInfo(); session.setUserInfo(ui); session.connect(); String command = "uname"; Channel channel = session.openChannel("exec"); ((ChannelExec) channel).setCommand(command); channel.setInputStream(null); ((ChannelExec) channel).setErrStream(System.err); InputStream in = channel.getInputStream(); channel.connect(); byte[] tmp = new byte[1024]; while (true) { while (in.available() > 0) { int i = in.read(tmp, 0, 1024); if (i < 0) break; System.out.print(new String(tmp, 0, i)); } if (channel.isClosed()) { System.out.println("exit-status: " + channel.getExitStatus()); break; } try { Thread.sleep(1000); } catch (Exception ee) { } } channel.disconnect(); session.disconnect(); } catch (Exception e) { System.out.println(e); } } public static class MyUserInfo implements UserInfo, UIKeyboardInteractive { String passwd; public String getPassword() { return passwd; } public boolean promptYesNo(String str) { return true; } public String getPassphrase() { return null; } public boolean promptPassphrase(String message) { return true; } public boolean promptPassword(String message) { passwd = SSH_SERVER_PASSWORD; return true; } public void showMessage(String message) { System.out.println("message = " + message); } public String[] promptKeyboardInteractive(String destination, String name, String instruction, String[] prompt, boolean[] echo) { if (prompt[0].equals("Password: ")){ String[] response = new String[1]; response[0] = SSH_SERVER_PASSWORD; return response; } return null; } } }
回答5:
public String getPassphrase() { return null; }
public boolean promptPassphrase(String message) { return true; } public boolean promptPassword(String message) { passwd = SSH_SERVER_PASSWORD; return true; } public void showMessage(String message) { System.out.println("message = " + message);
