<?php
/**
 * ownCloud
 *
 * @author Sam Tuke, Frank Karlitschek
 * @copyright 2012 Sam Tuke samtuke@owncloud.com, 
 * Frank Karlitschek frank@owncloud.org
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

// Todo:
//  - Crypt/decrypt button in the userinterface
//  - Setting if crypto should be on by default
//  - Add a setting "Don´t encrypt files larger than xx because of performance reasons"
//  - Transparent decrypt/encrypt in filesystem.php. Autodetect if a file is encrypted (.encrypted extension)
//  - Don't use a password directly as encryption key. but a key which is stored on the server and encrypted with the user password. -> password change faster
//  - IMPORTANT! Check if the block lenght of the encrypted data stays the same

namespace OCA\Encryption;

/**
 * @brief Class for utilities relating to encrypted file storage system
 * @param $view OC_FilesystemView object, expected to have OC '/' as root path
 * @param $client flag indicating status of client side encryption. Currently
 * unused, likely to become obsolete shortly
 */

class Util {

	# DONE: add method to check if file is encrypted using new system
	# DONE: add method to check if file is encrypted using old system
	# DONE: add method to fetch legacy key
	# DONE: add method to decrypt legacy encrypted data
	# DONE: fix / test the crypt stream proxy class	
	# DONE: replace cryptstream wrapper new AES based system
	# DONE: Encryption works for writing new text files in web ui
	# DONE: reading unencrypted files when encryption is enabled works via webdav
	
	# TODO: file uploaded via web ui get encrypted
	# TODO: new files created and uploaded via webdav get encrypted
	
	# TODO: add support for optional recovery user in case of lost passphrase / keys
	# TODO: add admin optional required long passphrase for users
	# TODO: implement flag system to allow user to specify encryption by folder, subfolder, etc.
	# TODO: add UI buttons for encrypt / decrypt everything?
	
	# TODO: add method to encrypt all user files using new system
	# TODO: add method to decrypt all user files using new system
	# TODO: add method to encrypt all user files using old system
	# TODO: add method to decrypt all user files using old system
	
	# TODO: test new encryption with webdav
	# TODO: test new encryption with versioning
	# TODO: test new encryption with sharing
	# TODO: test new encryption with proxies
	
	# NOTE: Curretly code on line 206 onwards in lib/proxy.php needs work. This code is executed when webdav writes take place, and appears to need to convert streams into fopen resources. Currently code within the if statement on 215 is not executing. Investigate the paths (handled there (which appear to be blank), and whether oc_fsv is borking them during processing.
	
	# NOTE: When files are written via webdav, they are encrypted and saved on the server, though they are not readable via web ui or webdav. proof of this is the changing length of content. When read in web ui, text reads "false", persumably because decryption failed. Why no error in 
	
	# NOTE: for some reason file_get_contents is not working in proxy class postfopen. The same line works in sscce, but always returns an empty string in proxy.php. this is the same regardless of whether oc_fs, oc_fsv, or direct use of phps file_get_contents is used

	private $view; // OC_FilesystemView object for filesystem operations
	private $pwd; // User Password
	private $client; // Client side encryption mode flag
	private $publicKeyDir; // Directory containing all public user keys
	private $encryptionDir; // Directory containing user's files_encryption
	private $keyfilesPath; // Directory containing user's keyfiles
	private $publicKeyPath; // Path to user's public key
	private $privateKeyPath; // Path to user's private key

	public function __construct( \OC_FilesystemView $view, $userId, $client = false ) {
	
		$this->view = $view;
		$this->userId = $userId;
		$this->client = $client;
		$this->publicKeyDir =  '/' . 'public-keys';
		$this->encryptionDir =  '/' . $this->userId . '/' . 'files_encryption';
		$this->keyfilesPath = $this->encryptionDir . '/' . 'keyfiles';
		$this->publicKeyPath = $this->publicKeyDir . '/' . $this->userId . '.public.key'; // e.g. data/public-keys/admin.public.key
		$this->privateKeyPath = $this->encryptionDir . '/' . $this->userId . '.private.key'; // e.g. data/admin/admin.private.key
		
	}
	
	public function ready() {
		
		if( 
		!$this->view->file_exists( $this->keyfilesPath )
		or !$this->view->file_exists( $this->publicKeyPath )
		or !$this->view->file_exists( $this->privateKeyPath ) 
		) {
		
			return false;
			
		} else {
		
			return true;
			
		}
	
	}
	
        /**
         * @brief Sets up user folders and keys for serverside encryption
         * @param $passphrase passphrase to encrypt server-stored private key with
         */
	public function setupServerSide( $passphrase = null ) {
		
		// Create shared public key directory
		if( !$this->view->file_exists( $this->publicKeyDir ) ) {
		
			$this->view->mkdir( $this->publicKeyDir );
		
		}
		
		// Create encryption app directory
		if( !$this->view->file_exists( $this->encryptionDir ) ) {
		
			$this->view->mkdir( $this->encryptionDir );
		
		}
		
		// Create mirrored keyfile directory
		if( !$this->view->file_exists( $this->keyfilesPath ) ) {
		
			$this->view->mkdir( $this->keyfilesPath );
		
		}
		
		// Create user keypair
		if ( 
		!$this->view->file_exists( $this->publicKeyPath ) 
		or !$this->view->file_exists( $this->privateKeyPath ) 
		) {
		
			// Generate keypair
			$keypair = Crypt::createKeypair();
		
			\OC_FileProxy::$enabled = false;
			
			// Save public key
			$this->view->file_put_contents( $this->publicKeyPath, $keypair['publicKey'] );
			
			// Encrypt private key with user pwd as passphrase
			$encryptedPrivateKey = Crypt::symmetricEncryptFileContent( $keypair['privateKey'], $passphrase );
			
			// Save private key
			$this->view->file_put_contents( $this->privateKeyPath, $encryptedPrivateKey );
			
			\OC_FileProxy::$enabled = true;
			
		}
		
		return true;
	
	}
	
	public function findFiles( $directory, $type = 'plain' ) {
	
	# TODO: test finding non plain content
		
		if ( $handle = $this->view->opendir( $directory ) ) {

			while ( false !== ( $file = readdir( $handle ) ) ) {
			
				if (
				$file != "." 
				&& $file != ".."
				) {
				
					$filePath = $directory . '/' . $this->view->getRelativePath( '/' . $file );
					
					var_dump($filePath);
					
					if ( $this->view->is_dir( $filePath ) ) { 
						
						$this->findFiles( $filePath );
						
					} elseif ( $this->view->is_file( $filePath ) ) {
					
						if ( $type == 'plain' ) {
					
							$this->files[] = array( 'name' => $file, 'path' => $filePath );
							
						} elseif ( $type == 'encrypted' ) {
						
							if (  Crypt::isEncryptedContent( $this->view->file_get_contents( $filePath ) ) ) {
							
								$this->files[] = array( 'name' => $file, 'path' => $filePath );
							
							}
						
						} elseif ( $type == 'legacy' ) {
						
							if (  Crypt::isLegacyEncryptedContent( $this->view->file_get_contents( $filePath ) ) ) {
							
								$this->files[] = array( 'name' => $file, 'path' => $filePath );
							
							}
						
						}
					
					}
					
				}
				
			}
			
			if ( !empty( $this->files ) ) {
			
				return $this->files;
			
			} else {
			
				return false;
			
			}
		
		}
		
		return false;

	}
	
        /**
         * @brief Check if a given path identifies an encrypted file
         * @return true / false
         */
	public function isEncryptedPath( $path ) {
	
		$data = $this->view->file_get_contents( $path );
		
		return Crypt::isEncryptedContent( $data );
	
	}
	
	public function encryptAll( $directory ) {
	
		$plainFiles = $this->findFiles( $this->view, 'plain' );
		
		if ( $this->encryptFiles( $plainFiles ) ) {
		
			return true;
			
		} else {
		
			return false;
			
		}
		
	}
	
	/**
	 * @brief Get the blowfish encryption handeler for a key
	 * @param $key string (optional)
	 * @return Crypt_Blowfish blowfish object
	 *
	 * if the key is left out, the default handeler will be used
	 */
	public function getBlowfish( $key = '' ) {
	
		if ( $key ) {
		
			return new \Crypt_Blowfish( $key );
		
		} else {
		
			return false;
			
		}
		
	}
	
	/**
	 * @brief Fetch the legacy encryption key from user files
	 * @param string $login used to locate the legacy key
	 * @param string $passphrase used to decrypt the legacy key
	 * @return true / false
	 *
	 * if the key is left out, the default handeler will be used
	 */
	public function getLegacyKey( $passphrase ) {
		
		// Disable proxies to prevent attempt to automatically decrypt key
		OC_FileProxy::$enabled = false;
		
		if ( 
		$passphrase 
		and $key = $this->view->file_get_contents( '/encryption.key' ) 
		) {
		
			OC_FileProxy::$enabled = true;
		
			if ( $this->legacyKey = $this->legacyDecrypt( $key, $passphrase ) ) {
			
				return true;
				
			} else {
			
				return false;
				
			}
			
		} else {
		
			OC_FileProxy::$enabled = true;
		
			return false;
			
		}
		
	}
	
	/**
	 * @brief encrypts content using legacy blowfish system
	 * @param $content the cleartext message you want to encrypt
	 * @param $key the encryption key (optional)
	 * @returns encrypted content
	 *
	 * This function encrypts an content
	 */
	public function legacyEncrypt( $content, $passphrase = '' ) {
	
		$bf = $this->getBlowfish( $passphrase );
		
		return $bf->encrypt( $content );
		
	}
	
	/**
	* @brief decryption of an content
	* @param $content the cleartext message you want to decrypt
	* @param $key the encryption key (optional)
	* @returns cleartext content
	*
	* This function decrypts an content
	*/
	public function legacyDecrypt( $content, $passphrase = '' ) {
	
		$bf = $this->getBlowfish( $passphrase );
		
		$decrypted = $bf->decrypt( $content );
		
		$trimmed = rtrim( $decrypted, "\0" );
		
		return $trimmed;
		
	}
	
	public function legacyKeyRecryptKeyfile( $legacyEncryptedContent, $legacyPassphrase, $publicKey, $newPassphrase ) {
	
		$decrypted = $this->legacyDecrypt( $legacyEncryptedContent, $legacyPassphrase );
	
		$recrypted = Crypt::keyEncryptKeyfile( $decrypted, $publicKey );
		
		return $recrypted;
	
	}
	
	/**
	* @brief Re-encryptes a legacy blowfish encrypted file using AES with integrated IV
	* @param $legacyContent the legacy encrypted content to re-encrypt
	* @returns cleartext content
	*
	* This function decrypts an content
	*/
	public function legacyRecrypt( $legacyContent, $legacyPassphrase, $newPassphrase ) {
		
		# TODO: write me
	
	}
	
	public function getPath( $pathName ) {
	
		switch ( $pathName ) {
			
			case 'publicKeyDir':
			
				return $this->publicKeyDir;
				
				break;
				
			case 'encryptionDir':
			
				return $this->encryptionDir;
				
				break;
				
			case 'keyfilesPath':
			
				return $this->keyfilesPath;
				
				break;
				
			case 'publicKeyPath':
			
				return $this->publicKeyPath;
				
				break;
				
			case 'privateKeyPath':
			
				return $this->privateKeyPath;
				
				break;
			
		}
		
	}

}