encryptorcode/iam-oauth

When encrypting data with the Cipher Block Chaining (CBC) mode an Initialization Vector (IV) is used to randomize the encryption, ie under a given key the same plaintext doesn't always produce the same ciphertext. The IV doesn't need to be secret but should be unpredictable to avoid "Chosen-Plaintext Attack".

To generate Initialization Vectors, NIST recommends to use a secure random number generator.

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

• OWASP Top 10 2017 Category A6 - Security Misconfiguration
• MITRE, CWE-329 - CWE-329: Not Using an Unpredictable IV with CBC Mode
• MITRE, CWE-330 - Use of Insufficiently Random Values
• NIST, SP-800-38A - Recommendation for Block Cipher Modes of Operation
• Derived from FindSecBugs rule STATIC_IV

When encrypting data with the Cipher Block Chaining (CBC) mode an Initialization Vector (IV) is used to randomize the encryption, ie under a given key the same plaintext doesn't always produce the same ciphertext. The IV doesn't need to be secret but should be unpredictable to avoid "Chosen-Plaintext Attack".

To generate Initialization Vectors, NIST recommends to use a secure random number generator.

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

• OWASP Top 10 2017 Category A6 - Security Misconfiguration
• MITRE, CWE-329 - CWE-329: Not Using an Unpredictable IV with CBC Mode
• MITRE, CWE-330 - Use of Insufficiently Random Values
• NIST, SP-800-38A - Recommendation for Block Cipher Modes of Operation
• Derived from FindSecBugs rule STATIC_IV

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for long lines.

Rationale: Long lines are hard to read in printouts or if developershave limited screen space for the source code, e.g. if the IDEdisplays additional information like project tree, class hierarchy,etc.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that the groups of import declarations appear in the order specifiedby the user. If there is an import but its group is not specified in theconfiguration such an import should be placed at the end of the import list.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for long lines.

Rationale: Long lines are hard to read in printouts or if developershave limited screen space for the source code, e.g. if the IDEdisplays additional information like project tree, class hierarchy,etc.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that there are no import statements that use the * notation.

Rationale: Importing all classes from a package or staticmembers from a class leads to tight coupling between packagesor classes and might lead to problems when a new version of alibrary introduces name clashes.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks that class type parameter names conform to a specified pattern.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.

Checks for long lines.

Rationale: Long lines are hard to read in printouts or if developershave limited screen space for the source code, e.g. if the IDEdisplays additional information like project tree, class hierarchy,etc.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.