abstimm-idD/functions.php

<?php

class AbstimmIDd {
	private $cfg;
	private $mysqli;

	function __construct() {
		$this->cfg = parse_ini_file('config.ini', $process_sections = true);
		$this->mysqli = new mysqli(
			$this->cfg['database']['host'],
			$this->cfg['database']['user'], 
			$this->cfg['database']['password'],
			$this->cfg['database']['database']);
		$this->cfg['database']['password'] = '';
	}

	/**
	* Utility function to get the event ID for an event token
	* @param string $token The UUID of the event
	* @return int The ID if the event was found, 0 otherwise
	*/
	function get_event_id(string $token) : int {
		$query = 'SELECT id FROM events WHERE token=? LIMIT 1';
		$stmt = $this->mysqli->prepare($query);
		$stmt->bind_param('s', $token);
		$stmt->execute();

		$event_id = 0;
		$stmt->bind_result($event_id);
		$stmt->fetch();
		$stmt->close();
		return (int)$event_id;
	}

	/**
	* API endpoint to register an event token
	* @param mixed $body The JSON object as specified in the API documentation
	* @return mixed The JSON response object
	*/
	function register_event($body) {
		// check if the event already exists
		if ($this->get_event_id($body->event_token) !== 0) {
			return ['success' => false];
		}

		// otherwise, create the event
		$query = 'INSERT INTO events (token) VALUES (?)';
		$stmt = $this->mysqli->prepare($query);
		$stmt->bind_param('s', $body->event_token);
		$stmt->execute();
		$stmt->close();
		return ['success' => true];
	}

	/**
	* API endpoint to get voting IDs (will be generated on demand if needed)
	* @param mixed $body The JSON object as specified in the API documentation
	* @return mixed The JSON response object
	*/
	function get_voting_ids($body) {
		if (($event_id = $this->get_event_id($body->event_token)) === 0) {
			return ['error' => 'event not found'];
		}

		$vote_round = (int)$body->round;
		$result = [];

		foreach($body->user_names as $name) {
			// skip empty names (e.g. if batch processing text files with empty lines)
			if (strlen($name) > 0) {
				$hash = $this->get_hash($event_id, $vote_round, $name);
				$result[] = ['round' => $vote_round, 'user_name' => $name, 'hash' => $hash];
			}
		}
		return $result;
	}

	/**
	* Utility function to get a specific voting hash
	* @param int $event_id The ID of the event
	* @param int $vote_round The vote round
	* @param string $name The name of the delegatee
	* @return string The voting hash
	*/
	function get_hash(int $event_id, int $vote_round, string $name) : string {
		$query = 'SELECT hash FROM hashes WHERE event=? AND vote_round=? AND name=? LIMIT 1';
		$stmt = $this->mysqli->prepare($query);
		$stmt->bind_param('iis', $event_id, $vote_round, $name);
		$stmt->execute();

		$hash = '';
		$stmt->bind_result($hash);
		$stmt->fetch();
		$stmt->close();

		if (strlen($hash) == 0)
			return $this->create_hash($event_id, $vote_round, $name);
		else
			return $hash;
	}

	/**
	* Utility function to generate a new hash
	* @param int $event_id The ID of the event
	* @param int $vote_round The vote round
	* @param string $name The name of the delegatee
	* @return string The voting hash
	*/
	function create_hash(int $event_id, int $vote_round, string $name) : string {
		// sanitize the inputs which will go to the shell
		$vote_round = (int)$vote_round;
		$name = addslashes($name);

		// generate the hash (the PHP password_hash function does not provide the required options)
		$hash = shell_exec("echo -n '$name' | argon2 'Abstimmung $vote_round' \
			-p {$this->cfg['argon2']['threads']} \
			-m {$this->cfg['argon2']['memory']} \
			-t {$this->cfg['argon2']['iterations']} \
			-l {$this->cfg['argon2']['length']} -id -r");
		$hash = str_replace(array("\n", "\r"), '', $hash);

		// insert the new hash into the database
		$query = 'INSERT INTO hashes (event, vote_round, name, hash) VALUES (?, ?, ?, ?)';
		$stmt = $this->mysqli->prepare($query);
		$stmt->bind_param('iiss', $event_id, $vote_round, $name, $hash);
		$stmt->execute();
		$stmt->close();

		return $hash;
	}

	/**
	* API endpoint to generate a voting result textfile and PDF
	* @param mixed $body The JSON object as specified in the API documentation
	* @return mixed The JSON response object
	*/
	function export_result($body) {
		if ($this->get_event_id($body->event_token) === 0) {
			return ['success' => false];
		}

		// if a raw JSON export is configured, write the data
		if (strlen($this->cfg['export']['rawpath']) > 0) {
			$filepath = "{$this->cfg['export']['rawpath']}/{$body->event_token}-{$body->vote_round}.json";
			file_put_contents($filepath, json_encode($body));
		}

		// sanitize the inputs which will go to the filesystem path
		$vote_round = (int)$body->vote_round;
		$event_title = str_replace(' ', '_', addslashes($body->event_title));

		$file_path = $this->cfg['export']['path'] . '/' . date('Y-m-d') .
			"__{$event_title}__Abstimmung-$vote_round";

		$sha256_txt = $this->create_text_file($body, "$file_path.txt");
		$sha256_pdf = $this->create_pdf_file($body, "$file_path.pdf");

		return [
			'success' => true,
			'hash_txt' => $sha256_txt,
			'hash_pdf' => $sha256_pdf,
			'signing_key' => $this->cfg['export']['pgpkey']];
	}

	/**
	* Utility function to create a signed voting result text file 
	* @param mixed $body The complete JSON object from the API endpoint
	* @param string $file_path The path and name of the output file
	* @return string The SHA256 hash of the file created
	*/
	function create_text_file($body, string $file_path) : string {
		// create the file's header
		$header = str_replace('%t', $body->event_title, $this->cfg['export']['header']);
		$header = str_replace('%d', date('d.m.Y'), $header);
		$header = str_replace('%r', $body->vote_round, $header);

		$file_data = <<<EOT
$header\n
Abstimm-ID                       | Stimme(n)
#################################|#############\n
EOT;

		// append the votes
		foreach ($body->votes as $vote) {
			$file_data .= $vote->hash . ' | ' . implode(', ', $vote->vote) . "\n";
		}
		$file_data .= "\n";

		// write the file and create a detached GPG signature
		file_put_contents($file_path, $file_data);
		shell_exec("gpg --sign '$file_path'");

		// synchronize both files
		$this->sync_command($file_path);
		$this->sync_command($file_path.".gpg");

		// return the hash of the text file
		return trim(shell_exec("/usr/bin/sha256sum '$file_path' | awk '{ print $1 }'"));
	}

	/**
	* Utility function to create a signed voting result PDF file 
	* @param mixed $body The complete JSON object from the API endpoint
	* @param string $file_path The path and name of the output file
	* @return string The SHA256 hash of the file created
	*/
	function create_pdf_file($body, string $file_path) : string {
		// get the maximum number of votes a single person did to determine the number of columns
		$col_count = 0;
		foreach ($body->votes as $vote)
			if (count($vote->vote) > $col_count)
				$col_count = count($vote->vote);

		// if no columns (or too many), stop the pdf process
		if ($col_count < 1 || $col_count > 5)
			return '';

		// build the table header variables
		$table_col_count = str_repeat('|l', $col_count);
		$table_col_headers = '';
		for ($i = 0; $i < $col_count; $i++)
			$table_col_headers .= ' & \textbf{Stimme '.($i+1).'}';

		// build the table body with the votes
		$table_body = '';
		foreach ($body->votes as $vote) {
			// start with the vote hash
			$table_body .= " $vote->hash";

			// continue with the existing votes
			$cols_done = 0;
			foreach ($vote->vote as $v){
				$table_body .= " & $v";
				$cols_done++;
			}

			// fill the empty columns, if any
			for ($i = $cols_done; $i < $col_count; $i++)
				$table_body .= ' &';

			// end the line
			$table_body .= " \\\\\n";
		}

		// read in the template file
		if (($tmpl = file_get_contents($this->cfg['export']['pdf_tmpl'])) === false)
			throw new Exception('PDF template not found');

		// do the template variable replacements
		$tmpl = str_replace('==EVENT_NAME==', $body->event_title, $tmpl);
		$tmpl = str_replace('==VOTE_ROUND==', $body->vote_round,  $tmpl);
		$tmpl = str_replace('==COL_COUNT==',  $table_col_count,   $tmpl);
		$tmpl = str_replace('==COL_HDRS==',   $table_col_headers, $tmpl);
		$tmpl = str_replace('==TABLE_BODY==', $table_body,        $tmpl);

		$fdir  = pathinfo($file_path, PATHINFO_DIRNAME).'/'; // just the directory part
		$fname = pathinfo($file_path, PATHINFO_FILENAME); // filename without extension
		$ffull = $fdir.$fname;

		// write the temporary tex file and convert it to pdf
		if (file_put_contents("$ffull.tex", $tmpl) === false)
			throw new Exception('Could not write tex file');

		shell_exec("cd $fdir; /usr/bin/pdflatex $fname.tex");

		// remove the temporary files
		unlink("$ffull.tex");
		unlink("$ffull.log");
		unlink("$ffull.aux");

		// TODO: sign the pdf file
		shell_exec("gpg --sign '$ffull'.pdf");

		// synchronize the file
		$this->sync_command("$ffull.pdf");

		// return the hash of the file
		return trim(shell_exec("/usr/bin/sha256sum '$file_path' | awk '{ print $1 }'"));
	}

	/**
	* Utility function to synchronize a specific file with a remote location,
	* with a command specified in the config.ini file
	* @param string $file_path The path to the file
	* @return none
	*/
	function sync_command(string $file_path) {
		if (isset($this->cfg['export']['synccmd'])) {
			$cmd = $this->cfg['export']['synccmd'];
			if (strlen($cmd) > 0) {
				$cmd = str_replace('%f', $file_path, $cmd);
				shell_exec($cmd);
			}
		}
	}

}