MSC03-J. Never hardcode sensitive information

Hardcoding sensitive information, such as passwords, server IP addresses and encryption keys, is an extremely dangerous practice. This is because adversaries who have access to the class files can decompile them to discover the sensitive information. Additionally, once the system goes into production mode, it can become unwieldy to manage and accommodate changes to the code. For instance, a change in password may need to be communicated using a patch [[Chess 2007]].

Noncompliant Code Example

This noncompliant code example uses a password field instantiated as a String.

class Password {
  String password = new String("guest");
  public static void main(String[] args) {
    //..
 }
}

A malicious user can use the javap -c Password command to disassemble the class and discover the hardcoded password. The output of the disassembler as shown below, reveals the password guest in cleartext.

Compiled from "Password.java"
class Password extends java.lang.Object{
java.lang.String password;

Password();
  Code:
   0:	aload_0
   1:	invokespecial	#1; //Method java/lang/Object."<init>":()V
   4:	aload_0
   5:	new	#2; //class java/lang/String
   8:	dup
   9:	ldc	#3; //String guest
   11:	invokespecial	#4; //Method java/lang/String."<init>":(Ljava/lang/String;)V
   14:	putfield	#5; //Field password:Ljava/lang/String;
   17:	return

public static void main(java.lang.String[]);
  Code:
   0:	return

}

Compliant Solution

This compliant solution uses a char array to store the password after it is retrieved from an external file existing in a secure directory. The password is immediately cleared after use, limiting the exposure time.

class Password {
  public static void main(String[] args) throws IOException {
    char[] password = new char[100];	
    BufferedReader br = new BufferedReader(new InputStreamReader(
      new FileInputStream("credentials.txt")));

    // Reads the password into the char array, returns the number of bytes read 
    int n = br.read(password);  
    // Decrypt password, perform operations
    for(int i = n - 1; i >= 0; i--) {  // Manually clear out the password immediately after use 
      password[i] = 0;	 
    }
    br.close();
  }
}

To further limit the exposure time of the sensitive password, follow the guideline MSC10-J. Limit the lifetime of sensitive data by replacing BufferedReader with a direct NIO buffer.

Noncompliant Code Example (hardcoded database password)

This noncompliant code example hardcodes the user name and password fields in the SQL connection request.

public final Connection getConnection() throws SQLException {
  return DriverManager.getConnection("jdbc:mysql://localhost/dbName", "username", "password");
}

Note that the one and two argument java.sql.DriverManager.getConnection() methods may also be used incorrectly. Applets that contain similar code are also unacceptable because they may be executed in untrusted environments.

Compliant Solution

This compliant solution reads the user name and password from a configuration file present in a secure directory.

public final Connection getConnection() throws SQLException {
  // Username and password are read at runtime from a secure config file
  return DriverManager.getConnection("jdbc:mysql://localhost/dbName", username, password);
}

It is also permissible to prompt the user for the user name and password at runtime and use the entered values.

Risk Assessment

Hardcoding sensitive information allows an attacker to glean the information.

Automated Detection

TODO

Related Vulnerabilities

GERONIMO-2925, GERONIMO-1135

Other Languages

This guideline appears in the C Secure Coding Standard as MSC18-C. Be careful while handling sensitive data, such as passwords, in program code

Bibliography

[[Gong 2003]] 9.4 Private Object State and Object Immutability
[[Chess 2007]] 11.2 Outbound Passwords: Keep Passwords out of Source Code
[[Fortify 2008]] "Unsafe Mobile Code: Database Access"
[[MITRE 2009]] CWE-259 "Hard-Coded Password," CWE-798, "Use of Hard-coded Credentials"

      Miscellaneous (MSC)      MSC04-J. Do not use Object.equals() to compare cryptographic keys