有谁知道如何使用Java GSS-API从密钥分发中心（KDC）获取服务票证？
我有一个胖客户端应用程序，首先通过JAAS使用Krb5LoginModule从票证缓存中获取TGT进行身份验证（后台：Windows，例如使用kerberos实现并将票证授予票证存储在安全的内存区域）。从LoginManager我得到包含TGT的Subject对象。现在我希望当我为我的服务创建一个特定的GSSCredential对象时，服务票证也将被放入Subject的私人凭证中（我已经在网上的某处读过）。所以我尝试了以下内容：
// Exception handling ommitted
LoginContext lc = new LoginContext("HelloEjbClient", new DialogCallbackHandler());
lc.login()
Subject.doAs(lc.getSubject(), new PrivilegedAction() {
public Object run() {
GSSManager manager = GSSManager.getInstance();
GSSName clientName = manager.createName("clientUser", GSSName.NT_USER_NAME);
GSSCredential clientCreds = manager.createCredential(clientName, 8 * 3600, createKerberosOid(), GSSCredential.INITIATE_ONLY);
GSSName serverName = manager.createName("myService@localhost", GSSName.NT_HOSTBASED_SERVICE);
manager.createCredential(serverName, GSSCredential.INDEFINITE_LIFETIME, createKerberosOid(), GSSCredential.INITIATE_ONLY);
return null;
}
private Oid createKerberosOid() {
return new Oid("1.2.840.113554.1.2.2");
}
});
不幸的是我得到了一个GSSException：没有提供有效的凭据（机制级别：找不到任何Kerberos tgt）。
答案 0 :(得分：16)
我对获取服务票证的理解是错误的。我不需要从服务获取凭据 - 这在客户端上是不可能的，因为客户端实际上没有服务器的TGT，因此无权获取服务凭据。 这里缺少的是创建一个新的GSSContext并初始化它。如果我已正确理解，此方法的返回值包含服务票证。这是一个有效的代码示例。它必须代表已登录的主题在PrivilegedAction中运行：
GSSManager manager = GSSManager.getInstance();
GSSName clientName = manager.createName("clientUser", GSSName.NT_USER_NAME);
GSSCredential clientCred = manager.createCredential(clientName,
8 * 3600,
createKerberosOid(),
GSSCredential.INITIATE_ONLY);
GSSName serverName = manager.createName("http@server", GSSName.NT_HOSTBASED_SERVICE);
GSSContext context = manager.createContext(serverName,
createKerberosOid(),
clientCred,
GSSContext.DEFAULT_LIFETIME);
context.requestMutualAuth(true);
context.requestConf(false);
context.requestInteg(true);
byte[] outToken = context.initSecContext(new byte[0], 0, 0);
System.out.println(new BASE64Encoder().encode(outToken));
context.dispose();
然后outToken包含服务票证。然而，这不是GSS-API的使用方式。它的目标是将这些细节隐藏到代码中，因此最好使用两侧的GSS-API建立GSSContext。否则你真的应该知道你在做什么，因为潜在的安全漏洞。 有关详细信息，请比我更仔细地阅读Sun SSO tutorial with kerberos。
编辑： 忘记我使用的是Windows XP SP2。此版本的Windows中有一个新的“功能”，它不允许在Windows RAM中使用TGT。您必须编辑注册表才能允许此操作。有关更多信息，请查看JGSS Troubleshooting page主题，以防您遇到“KrbException：KDC不支持加密类型（14）”，就像我一样。
答案 1 :(得分：9)
使用此代码时遇到了很多问题，但我至少有一个解决方案。我在这里发布，也许它会帮助你们中的一些......
/**
* Tool to retrieve a kerberos ticket. This one will not be stored in the windows ticket cache.
*/
public final class KerberosTicketRetriever
{
private final static Oid KERB_V5_OID;
private final static Oid KRB5_PRINCIPAL_NAME_OID;
static {
try
{
KERB_V5_OID = new Oid("1.2.840.113554.1.2.2");
KRB5_PRINCIPAL_NAME_OID = new Oid("1.2.840.113554.1.2.2.1");
} catch (final GSSException ex)
{
throw new Error(ex);
}
}
/**
* Not to be instanciated
*/
private KerberosTicketRetriever() {};
/**
*
*/
private static class TicketCreatorAction implements PrivilegedAction
{
final String userPrincipal;
final String applicationPrincipal;
private StringBuffer outputBuffer;
/**
*
* @param userPrincipal p.ex. <tt>MuelleHA@MYFIRM.COM</tt>
* @param applicationPrincipal p.ex. <tt>HTTP/webserver.myfirm.com</tt>
*/
private TicketCreatorAction(final String userPrincipal, final String applicationPrincipal)
{
this.userPrincipal = userPrincipal;
this.applicationPrincipal = applicationPrincipal;
}
private void setOutputBuffer(final StringBuffer newOutputBuffer)
{
outputBuffer = newOutputBuffer;
}
/**
* Only calls {@link #createTicket()}
* @return <tt>null</tt>
*/
public Object run()
{
try
{
createTicket();
}
catch (final GSSException ex)
{
throw new Error(ex);
}
return null;
}
/**
*
* @throws GSSException
*/
private void createTicket () throws GSSException
{
final GSSManager manager = GSSManager.getInstance();
final GSSName clientName = manager.createName(userPrincipal, KRB5_PRINCIPAL_NAME_OID);
final GSSCredential clientCred = manager.createCredential(clientName,
8 * 3600,
KERB_V5_OID,
GSSCredential.INITIATE_ONLY);
final GSSName serverName = manager.createName(applicationPrincipal, KRB5_PRINCIPAL_NAME_OID);
final GSSContext context = manager.createContext(serverName,
KERB_V5_OID,
clientCred,
GSSContext.DEFAULT_LIFETIME);
context.requestMutualAuth(true);
context.requestConf(false);
context.requestInteg(true);
final byte[] outToken = context.initSecContext(new byte[0], 0, 0);
if (outputBuffer !=null)
{
outputBuffer.append(String.format("Src Name: %s\n", context.getSrcName()));
outputBuffer.append(String.format("Target : %s\n", context.getTargName()));
outputBuffer.append(new BASE64Encoder().encode(outToken));
outputBuffer.append("\n");
}
context.dispose();
}
}
/**
*
* @param realm p.ex. <tt>MYFIRM.COM</tt>
* @param kdc p.ex. <tt>kerbserver.myfirm.com</tt>
* @param applicationPrincipal cf. {@link #TicketCreatorAction(String, String)}
* @throws GSSException
* @throws LoginException
*/
static public String retrieveTicket(
final String realm,
final String kdc,
final String applicationPrincipal)
throws GSSException, LoginException
{
// create the jass-config-file
final File jaasConfFile;
try
{
jaasConfFile = File.createTempFile("jaas.conf", null);
final PrintStream bos = new PrintStream(new FileOutputStream(jaasConfFile));
bos.print(String.format(
"Krb5LoginContext { com.sun.security.auth.module.Krb5LoginModule required refreshKrb5Config=true useTicketCache=true debug=true ; };"
));
bos.close();
jaasConfFile.deleteOnExit();
}
catch (final IOException ex)
{
throw new IOError(ex);
}
// set the properties
System.setProperty("java.security.krb5.realm", realm);
System.setProperty("java.security.krb5.kdc", kdc);
System.setProperty("java.security.auth.login.config",jaasConfFile.getAbsolutePath());
// get the Subject(), i.e. the current user under Windows
final Subject subject = new Subject();
final LoginContext lc = new LoginContext("Krb5LoginContext", subject, new DialogCallbackHandler());
lc.login();
// extract our principal
final Set<Principal> principalSet = subject.getPrincipals();
if (principalSet.size() != 1)
throw new AssertionError("No or several principals: " + principalSet);
final Principal userPrincipal = principalSet.iterator().next();
// now try to execute the SampleAction as the authenticated Subject
// action.run() without doAsPrivileged leads to
// No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt)
final TicketCreatorAction action = new TicketCreatorAction(userPrincipal.getName(), applicationPrincipal);
final StringBuffer outputBuffer = new StringBuffer();
action.setOutputBuffer(outputBuffer);
Subject.doAsPrivileged(lc.getSubject(), action, null);
return outputBuffer.toString();
}
public static void main (final String args[]) throws Throwable
{
final String ticket = retrieveTicket("MYFIRM.COM", "kerbserver", "HTTP/webserver.myfirm.com");
System.out.println(ticket);
}
}