I have a simple Java application which runs a ssh command on remote using Jsch. The implementation works for username and password.
Now, I've setup a Kerberos server and want to authenticate using the same.
From a client system (Linux) I can ssh to remote and run commands using Kerberos authentication and it works fine.
Things I tried:
Initialise the kerberos user with: kinit -kt <keytab_file_path> <kUser>
Run ssh command: ssh <kUser>@<remote_host> uname -a
Above command works perfectly without asking me to authenticate using password.
Configuration details:
- KDC server on: Linux 7.6
- Client and server on: Linux 7.6
- Kerberos user: kuser
- kuser is also present on client and server system but do not have home directory
- Jsch version: 0.1.50
- Java version: Amazon Corretto 11.0.7
openjdk version "11.0.7" 2020-04-14 LTS
OpenJDK Runtime Environment Corretto-11.0.7.10.1 (build 11.0.7+10-LTS)
OpenJDK 64-Bit Server VM Corretto-11.0.7.10.1 (build 11.0.7+10-LTS, mixed mode)
Code snippet:
JSch jsch = new JSch();
jsch.setLogger(new MyLogger());
System.setProperty("java.security.krb5.conf", "/etc/krb5.conf");
System.setProperty("java.security.auth.login.config", "/etc/krb5login.conf");
System.setProperty("javax.security.auth.useSubjectCredsOnly", "false");
System.setProperty("sun.security.krb5.debug", "true");
System.setProperty("java.security.debug", "gssloginconfig,configfile,configparser,logincontext");
System.setProperty("java.security.krb5.realm", "MYREALM.COM");
System.setProperty("java.security.krb5.kdc", "myrealm.com");
String user = "kuser";
String host = "remote_host";
String port = "22";
try {
System.out.println("Starting session");
Session session = jsch.getSession(user ,host, Integer.parseInt(port));
Properties config = new java.util.Properties();
config.put("StrictHostKeyChecking", "no");
config.put("PreferredAuthentications", "gssapi-with-mic");
session.setConfig(config);
System.out.println("Connecting to session");
session.connect(20000);
System.out.println("Opening Channel");
Channel channel = session.openChannel("exec");
System.out.println("Connecting to channel");
// Creating BufferReader to read input from host
BufferedReader bufferReader = new BufferedReader(new InputStreamReader(channel.getInputStream()));
((ChannelExec) channel).setCommand("uname -a");
channel.connect();
System.out.println("Command executed");
StringBuilder stringBuilder = new StringBuilder();
for (String string = bufferReader.readLine(); string != null; string = bufferReader.readLine()) {
stringBuilder.append(string);
}
System.out.println(stringBuilder.toString());
channel.disconnect();
session.disconnect();
System.out.println("DONE");
} catch (Exception e) {
System.out.println("Exception:");
e.printStackTrace();
}
Below is my JASS conf file:
com.sun.security.jgss.krb5.initiate {
com.sun.security.auth.module.Krb5LoginModule required
doNotPrompt=true
principal="kuser"
useKeyTab=true
refreshKrb5Config=true
keyTab="/etc/kuser.keytab"
debug=true
storeKey=true;
};
krb5.conf as below:
[libdefaults]
default_realm = MYREALM.COM
default_ccache_name = KEYRING:persistent:%{uid}
default_tkt_enctypes = camellia128-cts-cmac camellia256-cts-cmac hmac aes256-cts aes128-cts des3-cbc-sha1 des-cbc-md5 aes256-cts-hmac-sha1-96 aes128-cts-hmac-sha1-96 des3-cbc-sha1-kd rc4-hmac
default_tgs_enctypes = camellia128-cts-cmac camellia256-cts-cmac hmac aes256-cts aes128-cts des3-cbc-sha1 des-cbc-md5 aes256-cts-hmac-sha1-96 aes128-cts-hmac-sha1-96 des3-cbc-sha1-kd rc4-hmac
permitted_enctypes = camellia128-cts-cmac camellia256-cts-cmac hmac aes256-cts aes128-cts des3-cbc-sha1 des-cbc-md5 aes256-cts-hmac-sha1-96 aes128-cts-hmac-sha1-96 des3-cbc-sha1-kd rc4-hmac
[realms]
MYREALM.COM = {
kdc = myrealm.com
admin_server = myrealm.com
default_domain = myrealm.com
}
After running the above standalone java program, I get below exception:
Starting session
Connecting to session
INFO: Connecting to remote_host port 22
INFO: Connection established
INFO: Remote version string: SSH-2.0-OpenSSH_7.4
INFO: Local version string: SSH-2.0-JSCH-0.1.50
INFO: Authentications that can continue: gssapi-with-mic
INFO: Next authentication method: gssapi-with-mic
Java config name: /etc/krb5.conf
Loading krb5 profile at /etc/krb5.conf
Loaded from Java config
Debug is true storeKey true useTicketCache false useKeyTab true doNotPrompt true ticketCache is null isInitiator true KeyTab is /etc/kuser.keytab refreshKrb5Config is true principal is kuser tryFirstPass is false useFirstPass is false storePass is false clearPass is false
Refreshing Kerberos configuration
Java config name: /etc/krb5.conf
Loading krb5 profile at /etc/krb5.conf
Loaded from Java config
KdcAccessibility: reset
KdcAccessibility: reset
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 76; type: 18
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 60; type: 17
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 68; type: 16
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 60; type: 23
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 76; type: 26
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 60; type: 25
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 52; type: 8
KeyTabInputStream, readName(): MYREALM.com
KeyTabInputStream, readName(): kuser
KeyTab: load() entry length: 52; type: 3
Looking for keys for: kuser@MYREALM.com
Added key: 3version: 4
Found unsupported keytype (8) for kuser@MYREALM.com
Found unsupported keytype (25) for kuser@MYREALM.com
Found unsupported keytype (26) for kuser@MYREALM.com
Added key: 23version: 4
Added key: 16version: 4
Added key: 17version: 4
Added key: 18version: 4
Looking for keys for: kuser@MYREALM.com
Added key: 3version: 4
Found unsupported keytype (8) for kuser@MYREALM.com
Found unsupported keytype (25) for kuser@MYREALM.com
Found unsupported keytype (26) for kuser@MYREALM.com
Added key: 23version: 4
Added key: 16version: 4
Added key: 17version: 4
Added key: 18version: 4
default etypes for default_tkt_enctypes: 18 17 16 3 18 17 16 23.
KrbAsReq creating message
KrbKdcReq send: kdc=myrealm.com UDP:88, timeout=30000, number of retries =3, #bytes=199
KDCCommunication: kdc=myrealm.com UDP:88, timeout=30000,Attempt =1, #bytes=199
KrbKdcReq send: #bytes read=738
KdcAccessibility: remove myrealm.com
Looking for keys for: kuser@MYREALM.com
Added key: 3version: 4
Found unsupported keytype (8) for kuser@MYREALM.com
Found unsupported keytype (25) for kuser@MYREALM.com
Found unsupported keytype (26) for kuser@MYREALM.com
Added key: 23version: 4
Added key: 16version: 4
Added key: 17version: 4
Added key: 18version: 4
EType: sun.security.krb5.internal.crypto.Aes256CtsHmacSha1EType
[Krb5LoginModule] authentication failed
Message stream modified (41)
INFO: Disconnecting from remote_host 22
Exception:
com.jcraft.jsch.JSchException: Auth fail
at com.jcraft.jsch.Session.connect(Session.java:512)
at com.example.TestJsch.main(TestJsch.java:49)
Thanks
