Java Runtime Error Message Containing Sensitive Information

Incomplete Variant

Structure: Simple

Description

In many cases, an attacker can leverage the conditions that cause unhandled exception errors in order to gain unauthorized access to the system.

Common Consequences 1

Scope: Confidentiality

Impact: Read Application Data

Potential Mitigations 1

Phase: Implementation

Do not expose sensitive error information to the user.

Demonstrative Examples 2

ID : DX-191

In the following Java example the class InputFileRead enables an input file to be read using a FileReader object. In the constructor of this class a default input file path is set to some directory on the local file system and the method setInputFile must be called to set the name of the input file to be read in the default directory. The method readInputFile will create the FileReader object and will read the contents of the file. If the method setInputFile is not called prior to calling the method readInputFile then the File object will remain null when initializing the FileReader object. A Java RuntimeException will be raised, and an error message will be output to the user.

Code Example:

Bad

Java

java

/* Assume appropriate validation / encoding is used and privileges / permissions are preserved / }

java

However, the error message output to the user contains information regarding the default directory on the local file system. This information can be exploited and may lead to unauthorized access or use of the system. Any Java RuntimeExceptions that are handled should not expose sensitive information to the user.

In the example below, the BankManagerLoginServlet servlet class will process a login request to determine if a user is authorized to use the BankManager Web service. The doPost method will retrieve the username and password from the servlet request and will determine if the user is authorized. If the user is authorized the servlet will go to the successful login page. Otherwise, the servlet will raise a FailedLoginException and output the failed login message to the error page of the service.

Code Example:

Bad

Java

java

// Get username and password from login page request* String username = request.getParameter("username"); String password = request.getParameter("password");

java

java

// output failed login message to error page* request.setAttribute("error", new String("Login Error")); request.setAttribute("message", ex.getMessage()); getServletContext().getRequestDispatcher("/ErrorPage.jsp").forward(request, response);}}

However, the output message generated by the FailedLoginException includes the user-supplied password. Even if the password is erroneous, it is probably close to the correct password. Since it is printed to the user's page, anybody who can see the screen display will be able to see the password. Also, if the page is cached, the password might be written to disk.

Applicable Platforms

Languages:

Java : Undetermined

Modes of Introduction

Implementation

Related Weaknesses

ChildOf:

Externally-Generated Error Message Containing Sensitive Information (CWE-211)