Encrypted data

As of PHP 7.2, the mcrypt library that iTop was using to encrypt AttributeEncryptedString, was removed from PHP core.
iTop versions before 2.6.0 are only able to encrypt through mcrypt, thus AttributeEncryptedString for these versions, is not compatible with PHP >= 7.2.

iTop 2.6 supports other PHP encryption library and retro-compatibility for data already encrypted with mcrypt in previous versions.

Choose & configure new encryption library

In order to pick an encryption library you'll need to define encryption_library in the configuration file, this parameter can take for value : Sodium, OpenSSL, Mcrypt (or OpenSSLMcryptCompatibility for PHP > 7.2) or Simple. The picked library needs to be installed and enabled in the current PHP installation (see setup/phpinfo.php).

You will also be required to define the key encryption_key that is used for iTop symetrical encryption (make sure you never loose it!).

If encryption_library and/or encryption_key are not defined, iTop will choose a library depending on your PHP installation and generate a key if Sodium or OpenSSL library were chosen

Sodium

LibSodium is a cryptography library shipped with PHP core as of PHP 7.2.

The current usage of Sodium in iTop encrypt data with Salsa20 stream cipher using the PHP (> 7.0) built in function random_bytes to generate a salt and saves data as base64 values.

LibSodium needs a SODIUM_CRYPTO_SECRETBOX_KEYBYTES bytes long encryption key. In order to ease admin to generate this key, we save it as an hexadecimal value.

Example to generate a valid Sodium key :

 php -r "echo bin2hex(sodium_crypto_secretbox_keygen());" > itop_secret_key.txt

OpenSSL

OpenSSL is a cryptography library frequently shipped with PHP.

The current usage of OpenSSL in iTop encrypt data with AES-256-CBC block cipher using openssl pseudo random bytes function to generate an initialisation vector.

This implementation of OpenSSL automaticaly pads the encryption key with zeros and saves data as base64 values.

For security reasons OpenSSL needs a 256 bits long encryption key. In order to ease admin to generate this key, we save it as an hexadecimal value.

Example to generate a valid AES-256 key :

 php -r "echo bin2hex(openssl_random_pseudo_bytes(32));" > itop_secret_key.txt

Until PHP 5.6.12 open_ssl_random_pseudo_bytes() is not a cryptographically secure pseudo-random number generator. As we use it for initialisation vector creation, we recommand you to update your PHP installation to >= 5.6.12.

Mcrypt (and OpenSSLMcryptCompatibility)

We DO NOT recommand using Mcrypt as it is an abandonware and was dropped from PHP core for obvious security reasons. However, if you already have mcrypt encrypted data, you can use OpenSSLMcryptCompatibility library option which allows you to still work on these data.

Mcrypt is a (deprecated) cryptography library that used to be shipped with PHP core up to PHP 7.1.

The current usage of Mcrypt in iTop encrypt data with BLOWFISH-CBC block cipher using mcrypt (or openssl) pseudo random bytes function to generate an initialisation vector.

If Mcrypt is specified but the library not installed (eg. in PHP 7.2+), iTop will try to use its backup OpenSSLMcryptCompatibility using OpenSSL library.

Simple