infos = Information about crypto plugin is in keys below
infos/author = Peter Nirschl peter.nosp@m..nir.nosp@m.schl@.nosp@m.gmai.nosp@m.l.com
infos/licence = BSD
infos/needs =
infos/provides = filefilter
infos/placements = postgetstorage presetstorage
infos/description = Cryptographic operations

This plugin is a filter plugin allowing Elektra to encrypt values before they are persisted and to decrypt values after they have been read from a backend.

The idea is to provide protection of sensible values before they are persisted. This means the value of a key needs to be encrypted before it is written to a file or a database. It also needs to be decrypted whenever an admissible access (read) is being performed.

The users of Elektra should not be bothered too much with the internals of the cryptographic operations. Also the cryptographic keys must never be exposed to the outside of the crypto module.

Dependencies

libgcrypt20-dev or libgcrypt-devel

Restrictions

The crypto plugin will encrypt and decrypt values using AES-256 in CBC mode.

The key derivation is still WIP.

Planned Features

Encryption of values
Decryption of values
Key derivation by metadata (password provided within a meta-key)
Key derivation by using a specified key-file (like the SSH client does)
Key derivation by utilizing the pgp-agent

The encryption and decryption of values is a straight forward process, once the key and IV are supplied. The key-derivation process in a library is a bit tricky.

The crypto plugin itself can hold configuration data about the order of the applied key derivation functions. For example, if a password is provided by a meta-key, it will be used, otherwise we look for a key file. If no key file has been configured, we try to trigger the PGP agent, etc.

The following example configuration illustrates this concept:

    system/elektra/crypto/config/key-derivation/#0 = meta
    system/elektra/crypto/config/key-derivation/#1 = file
    system/elektra/crypto/config/key-derivation/#2 = agent
    system/elektra/crypto/config/key-file/path/#0 = ~/.elektra/id_aes
    system/elektra/crypto/config/key-file/path/#1 = /etc/elektra/id_aes

Only keys marked with a certain meta-key will be considered for encryption/decryption.

Examples

Metadata based encyption

You specify the parameters of the cryptographic operations in a KeySet together with the keys to be encrypted. The following parameters are required:

Key - the symmetric cryptographic key for encryption
IV - the initialization vector (IV) that is required by the CBC mode

The following keys are required for metadata based encryption:

    /elektra/modules/crypto/key-derivation/key
    /elektra/modules/crypto/key-derivation/iv

You can use the following meta-key to mark a key for encryption:

    crypto/encrypt

If this meta-key has a value with a string-length greater than 0 (strlen() > 0) then the crypto-plugin will try to encrypt it.