rspec/rules/S3329/java/rule.adoc

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== Noncompliant Code Example

----
public class MyCbcClass {

  public String applyCBC(String strKey, String plainText) {
    byte[] bytesIV = "7cVgr5cbdCZVw5WY".getBytes("UTF-8");

    /* KEY + IV setting */
    IvParameterSpec iv = new IvParameterSpec(bytesIV);
    SecretKeySpec skeySpec = new SecretKeySpec(strKey.getBytes("UTF-8"), "AES");

    /* Ciphering */
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);  // Noncompliant: the IV is hard coded and thus not generated with a secure random generator
    byte[] encryptedBytes = cipher.doFinal(plainText.getBytes("UTF-8"));
    return DatatypeConverter.printBase64Binary(bytesIV)
            + ";" + DatatypeConverter.printBase64Binary(encryptedBytes);
  }
}
----

== Compliant Solution

----
public class MyCbcClass {

  SecureRandom random = new SecureRandom();

  public String applyCBC(String strKey, String plainText) {
    byte[] bytesIV = new byte[16];
    random.nextBytes(bytesIV);

    /* KEY + IV setting */
    IvParameterSpec iv = new IvParameterSpec(bytesIV);
    SecretKeySpec skeySpec = new SecretKeySpec(strKey.getBytes("UTF-8"), "AES");

    /* Ciphering */
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");
    cipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv); // Compliant
    byte[] encryptedBytes = cipher.doFinal(plainText.getBytes("UTF-8"));
    return DatatypeConverter.printBase64Binary(bytesIV)
            + ";" + DatatypeConverter.printBase64Binary(encryptedBytes);
  }
}
----

== See

* https://www.owasp.org/index.php/Top_10-2017_A6-Security_Misconfiguration[OWASP Top 10 2017 Category A6] - Security Misconfiguration
* http://cwe.mitre.org/data/definitions/329[MITRE, CWE-329] - CWE-329: Not Using an Unpredictable IV with CBC Mode
* http://cwe.mitre.org/data/definitions/330[MITRE, CWE-330] - Use of Insufficiently Random Values
* https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38a.pdf[NIST, SP-800-38A] - Recommendation for Block  Cipher Modes of Operation 
* Derived from FindSecBugs rule https://find-sec-bugs.github.io/bugs.htm#STATIC_IV[STATIC_IV]

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