Add optional PGP key verification on web server side.

gpg-mailgate-web/public_html/config.sample.php

@@ -42,6 +42,9 @@ $config['site_url'] = 'http://example.com/gpgmw';
 //title of the website (displayed on home page)
 $config['site_title'] = 'PGP key management';
 
+//whether debug mode should be enabled
+$config['debug'] = false;
+
 //
 // MAIL SETTINGS
 //
@@ -71,6 +74,27 @@ $config['db_username'] = 'gpgmw';
 //database password
 $config['db_password'] = '';
 
+//
+// PGP VERIFICATION SETTINGS
+//
+
+//whether to enable immediate verification of PGP keys
+// keys will always be verified with the email address in our cron job
+// but this will enable verification from the web interface before email confirmation
+//for this to work, Crypt_GPG from http://pear.php.net/Crypt_GPG must be installed
+// (as well as any of its dependencies), and pgpverify_tmpdir must be set
+$config['pgpverify_enable'] = false;
+
+//a temporary directory to use for PGP verification, without trailing slash
+// gpgmw will create subdirectories from here to use as temporary gpg home directories
+// these directories will (should) be deleted immediately after use
+$config['pgpverify_tmpdir'] = '/tmp';
+
+//whether to allow blank "keys"
+// this is useful to allow users to delete their key from the keystore
+// if they no longer want encryption
+$config['pgpverify_allowblank'] = true;
+
 //
 // LOCK SETTINGS
 //

gpg-mailgate-web/public_html/include/common.php

@@ -99,6 +99,21 @@ function secure_random() {
 	return hexdec(bin2hex(secure_random_bytes(3)));
 }
 
+function recursiveDelete($dirPath) {
+	foreach(
+		new RecursiveIteratorIterator(
+			new RecursiveDirectoryIterator(
+				$dirPath, FilesystemIterator::SKIP_DOTS
+			),
+			RecursiveIteratorIterator::CHILD_FIRST
+		)
+		as $path) {
+		$path->isFile() ? unlink($path->getPathname()) : rmdir($path->getPathname());
+	}
+
+	rmdir($dirPath);
+}
+
 function gpgmw_mail($subject, $body, $to) { //returns true=ok, false=notok
 	$config = $GLOBALS['config'];
 	$from = filter_var($config['email_from'], FILTER_SANITIZE_EMAIL);

gpg-mailgate-web/public_html/include/gpg.php

@@ -0,0 +1,85 @@
+<?php
+/*
+
+	gpg-mailgate
+
+	This file is part of the gpg-mailgate source code.
+
+	gpg-mailgate is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Affero General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	gpg-mailgate source code 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 gpg-mailgate source code. If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+//uses gpg to verify that a key belongs to a given email address
+function verifyPGPKey($content, $email) {
+	global $config;
+
+	//allow blank "keys" if this is set
+	//this means that encryption for $email will be disabled by the cron if it
+	// was enabled originally
+	if($config['pgpverify_allowblank'] && trim($content) == '') {
+		return true;
+	}
+
+	require_once("Crypt/GPG.php");
+
+	//try to create a random subdirectory of $config['pgpverify_tmpdir']
+	do {
+		$path = $config['pgpverify_tmpdir'] . '/' . uid(16);
+	} while(file_exists($path));
+
+	$result = @mkdir($path);
+
+	if($result === false) {
+		if($config['debug']) {
+			die("Failed to create directory [" . $path . "] for PGP verification.");
+		} else {
+			return false;
+		}
+	}
+
+	$gpg = new Crypt_GPG(array('homedir' => $path));
+
+	//import the key to our GPG temp directory
+	try {
+		$gpg->importKey($content);
+	} catch(Crypt_GPG_NoDataException $e) {
+		//user supplied an invalid key!
+		recursiveDelete($path);
+		return false;
+	}
+
+	//verify the email address matches
+	$keys = $gpg->getKeys();
+
+	if(count($keys) != 1) {
+		if($config['debug']) {
+			die("Error in PGP verification: key count is " . count($keys) . "!");
+		} else {
+			recursiveDelete($path);
+			return false;
+		}
+	}
+
+	$userIds = $keys[0]->getUserIds();
+
+	if(count($userIds) != 1 || strtolower($userIds[0]->getEmail()) != strtolower($email)) {
+		recursiveDelete($path);
+		return false;
+	}
+
+	recursiveDelete($path);
+	return true;
+}
+
+?>

gpg-mailgate-web/public_html/include/pgp.php

@@ -56,6 +56,15 @@ function requestPGP($email, $key) {
 		}
 	}
 
+	//if PGP key verification is enabled, do it
+	if($config['pgpverify_enable']) {
+		require_once(includePath() . "/gpg.php");
+
+		if(!verifyPGPKey($key, $email)) {
+			return "your key does not appear to be valid (ensure ASCII armor is enabled and that the email address entered matches the email address of the key)";
+		}
+	}
+
 	//well, it looks good, let's submit it
 	lockAction('requestpgp');
 	$confirm = uid(32);