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This chapter is about how cryptographic password hashing is done in ASEE Flow 7. In particular, the hashing algorithm that is being used and the salt generation. If you are not familiar with these topics, we recommend reading the articles about cryptographic hash function, salt and secure password hashing. The ASEE Flow version 7.6 and earlier use the cryptographic hash function SHA-1. Since ASEE Flow version 7.7 the hash function SHA-512 is used. If there is a need for another custom hash function, it is possible to plugin a custom password hashing algorithm in ASEE Flow. At salt generation, a random 16-byte per-user value is created, which is generated with SecureRandom. It is also possible to customize the salt generation if desired.

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Customize the Hashing Algorithm

If it is necessary to use a more secure hash algorithm, you can provide your own implementation. You can do this by implementing the PasswordEncryptor interface from the org.camunda.bpm.engine.impl.digest package. The interface ensures that all necessary functions for password hashing are implemented. You can have a look at the classes Base64EncodedHashDigest and ShaHashDigest from the org.camunda.bpm.engine.impl.digest package to see how this is done in ASEE Flow. A template for your own implementation could look as follows: 
public class MyPasswordEncryptor implements PasswordEncryptor {

  @Override
  public String encrypt(String password) {
    // do something
  }

  @Override
  public boolean check(String password, String encrypted) {
    // do something
  }
  
  @Override
  public String hashAlgorithmName() {
	// This name is used to resolve the algorithm used for the encryption of a password.
	return "NAME_OF_THE_ALGORITHM";
  }
}
Once this is done, you can use the process engine configuration to plug in the custom implementation by the setting the passwordEncryptor property to your custom implementation, e.g., MyPasswordEncryptor. See Process Engine Bootstrapping on where you have to set the property for your ASEE Flow environment. Note that, even if you have already users created with passwords hashed by other algorithms, e.g., old custom algorithms or the ASEE Flow default hash algorithm SHA-512, they can still automatically be resolved by the engine although you have added your custom algorithm afterwards. The property customPasswordChecker is a list of hashing algorithms to be used to check (older) passwords. The ASEE Flow default hashing algorithms are automatically added, so please only add your previous custom passwordEncryptor implementation to that list.
Heads Up!Please do not use your own implementation of a hash function, but rather a standard that has been peer reviewed!

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Customize the Salt generation

Similar to the hashing algorithm, the salt generation can be adjusted. First, implement the SaltGenerator interface from the org.camunda.bpm.engine.impl.digest. This ensures that all necessary functions are implemented. You can have a look at the classes Base64EncodedSaltGenerator and Default16ByteSaltGenerator from the org.camunda.bpm.engine.impl.digest package to see how this is done in ASEE Flow. A template for your own implementation could look as follows: 
public class MyCustomSaltGenerator implements SaltGenerator {

  @Override
  public String generateSalt() {
    // do something
  }
}
Once this is done, you can use the process engine configuration to plug in the custom implementation by the setting the saltGenerator property to your custom implementation, e.g., MyCustomSaltGenerator. See Process Engine Bootstrapping on where you have to set the property for your ASEE Flow environment.