Enigma Plugin for Roundcube

This plugin adds support for viewing and sending of signed and encrypted
messages in PGP (RFC 2440) and PGP/MIME (RFC 3156) format.

The plugin uses gpg binary on the server and stores all keys
(including private keys of the users) on the server.
Encryption/decryption is done server-side. So, this plugin
is for users that trust the server.


Implemented features:
---------------------
+ PGP: signatures verification
+ PGP: messages decryption
+ PGP: Sending of encrypted/signed messages
+ PGP: keys management UI (key import, export, delete)
+ PGP: key generation (client- or server-side)
+ Handling of PGP keys attached to incoming messages
+ User preferences to disable plugin features
+ Attaching public keys to email


TODO:
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- Handling of big messages with temp files
- Key info in contact details page (optional)
- Extended key management:
   - disable,
   - revoke,
   - change expiration date, change passphrase, add photo,
   - manage user IDs
   - export private keys
- Generate revocation certs
- Search filter to see invalid/expired keys
- Key server(s) support (search, import, upload, refresh)
- Mark keys as trusted/untrasted, display appropriate message in verify/decrypt status
- Change attachment icon on messages list for encrypted messages (like vcard_attachment plugin does)
- Support for multi-server installations (store keys in sql database?)
- Per-Identity settings (including keys/certs)
- Performance improvements:
   - cache decrypted message key id so we can skip decryption if we have no password in session
   - cache (last or successful only?) sig verification status to not verify on every msg preview (optional)
- S/MIME: Certs generation
- S/MIME: Certs management
- S/MIME: signed messages verification
- S/MIME: encrypted messages decryption
- S/MIME: Sending signed/encrypted messages
- S/MIME: Handling of certs attached to incoming messages
- S/MIME: Certificate info in Contacts details page (optional)


KNOWN ISSUES:
-------------
There are some know issues with accepting key passphrases on various
system configurations. This is caused by issues in PinEntry handling.
Make sure that vendor/bin/crypt-gpg-pinentry works from command line.
Possible reasons:
- non-supported GnuPG version, i.e. >= 2.1
- non-working loader in shebang (#! /usr/bin/env php)
