MSC31-J. Never hardcode sensitive information

Hardcoding sensitive information, such as passwords, 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 07]].

Noncompliant Code Example

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

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

A malicious user can use the javap -c Hardcoded 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 "Hardcoded.java"
class Hardcoded extends java.lang.Object{
java.lang.String password;

Hardcoded();
  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 secured directory. The password is immediately cleared out after use. This limits 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("password.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();
    }
}

Noncompliant Code Example

This noncompliant code example hard codes the user name and password fields.

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.

Compliant Solution

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

// username and password are read at runtime from a secure config file
public final Connection getConnection() throws SQLException {
  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 a malicious user to glean the information.

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Other Languages

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

References

[[Gong 03]] 9.4 Private Object State and Object Immutability
[[Chess 07]] 11.2 Outbound Passwords: Keep Passwords out of Source Code
[[MITRE 09]] CWE ID 259 "Hard-Coded Password"

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