Program: 30202
Project: 30202
Buggy source:
/** 
 * Get the username and password either from the JAAS subject or from thread local storage. For appclients if login has'nt happened this method would trigger login and popup a user interface to gather authentication information.
 * @return the security context.
 */
private SecurityContext getUsernameAndPassword(ComponentInvocation ci,CompoundSecMech mechanism) throws SecurityMechanismException {
  try {
    Subject s=null;
    if (isNotServerOrACC()) {
      ClientSecurityContext sc=ClientSecurityContext.getCurrent();
      if (sc == null) {
        return null;
      }
      s=sc.getSubject();
      if (_logger.isLoggable(Level.FINE)) {
        _logger.log(Level.FINE,"String_Node_Str" + s);
      }
    }
 else {
      if (isACC()) {
        ClientSecurityContext sc=ClientSecurityContext.getCurrent();
        if (sc == null) {
          s=LoginContextDriver.doClientLogin(SecurityConstants.USERNAME_PASSWORD,SecurityServicesUtil.getInstance().getCallbackHandler());
        }
 else {
          s=sc.getSubject();
        }
      }
 else {
        s=getSubjectFromSecurityCurrent();
      }
    }
    SecurityContext ctx=new SecurityContext();
    final Subject sub=s;
    ctx.subject=s;
    Set privateCredSet=AccessController.doPrivileged(new PrivilegedAction<Set>(){
      public Set run(){
        return sub.getPrivateCredentials();
      }
    }
);
    if (privateCredSet.isEmpty()) {
      if (_logger.isLoggable(Level.FINE)) {
        _logger.log(Level.FINE,"String_Node_Str");
      }
      ctx.authcls=null;
      ctx.identcls=GSSUPName.class;
    }
 else {
      AS_ContextSec asContext=mechanism.as_context_mech;
      final byte[] target_name=asContext.target_name;
      byte[] _realm=null;
      if (target_name == null || target_name.length == 0) {
        _realm=Realm.getDefaultRealm().getBytes();
      }
 else {
        _realm=GSSUtils.importName(GSSUtils.GSSUP_MECH_OID,target_name);
      }
      final String realm_name=new String(_realm);
      final Iterator it=privateCredSet.iterator();
      for (; it.hasNext(); ) {
        AccessController.doPrivileged(new PrivilegedAction<Object>(){
          public java.lang.Object run(){
            PasswordCredential pc=(PasswordCredential)it.next();
            pc.setRealm(realm_name);
            return null;
          }
        }
);
      }
      ctx.authcls=PasswordCredential.class;
    }
    return ctx;
  }
 catch (  LoginException le) {
    throw le;
  }
catch (  Exception e) {
    _logger.log(Level.SEVERE,"String_Node_Str",e);
    return null;
  }
}

Fixed version (ground truth):
/** 
 * Get the username and password either from the JAAS subject or from thread local storage. For appclients if login has'nt happened this method would trigger login and popup a user interface to gather authentication information.
 * @return the security context.
 */
private SecurityContext getUsernameAndPassword(ComponentInvocation ci,CompoundSecMech mechanism) throws SecurityMechanismException {
  try {
    Subject s=null;
    if (isNotServerOrACC()) {
      ClientSecurityContext sc=ClientSecurityContext.getCurrent();
      if (sc == null) {
        return null;
      }
      s=sc.getSubject();
      if (_logger.isLoggable(Level.FINE)) {
        _logger.log(Level.FINE,"String_Node_Str" + s);
      }
    }
 else {
      if (isACC()) {
        ClientSecurityContext sc=ClientSecurityContext.getCurrent();
        if (sc == null) {
          s=LoginContextDriver.doClientLogin(SecurityConstants.USERNAME_PASSWORD,SecurityServicesUtil.getInstance().getCallbackHandler());
        }
 else {
          s=sc.getSubject();
        }
      }
 else {
        s=getSubjectFromSecurityCurrent();
      }
    }
    SecurityContext ctx=new SecurityContext();
    final Subject sub=s;
    ctx.subject=s;
    Set<PasswordCredential> privateCredSet=AccessController.doPrivileged(new PrivilegedAction<Set>(){
      public Set run(){
        return sub.getPrivateCredentials(PasswordCredential.class);
      }
    }
);
    if (privateCredSet.isEmpty()) {
      if (_logger.isLoggable(Level.FINE)) {
        _logger.log(Level.FINE,"String_Node_Str");
      }
      ctx.authcls=null;
      ctx.identcls=GSSUPName.class;
    }
 else {
      AS_ContextSec asContext=mechanism.as_context_mech;
      final byte[] target_name=asContext.target_name;
      byte[] _realm=null;
      if (target_name == null || target_name.length == 0) {
        _realm=Realm.getDefaultRealm().getBytes();
      }
 else {
        _realm=GSSUtils.importName(GSSUtils.GSSUP_MECH_OID,target_name);
      }
      final String realm_name=new String(_realm);
      final Iterator it=privateCredSet.iterator();
      for (; it.hasNext(); ) {
        AccessController.doPrivileged(new PrivilegedAction<Object>(){
          public java.lang.Object run(){
            PasswordCredential pc=(PasswordCredential)it.next();
            pc.setRealm(realm_name);
            return null;
          }
        }
);
      }
      ctx.authcls=PasswordCredential.class;
    }
    return ctx;
  }
 catch (  LoginException le) {
    throw le;
  }
catch (  Exception e) {
    _logger.log(Level.SEVERE,"String_Node_Str",e);
    return null;
  }
}