mirror of
https://gerrit.wikimedia.org/r/mediawiki/extensions/OATHAuth
synced 2024-09-25 03:09:59 +00:00
a24d6adfbf
During the two-step login, users with OATH enabled need to have their login details saved into their session while we prompt them for their OATH code. This encrypts that data, so we don't write their user's password into our session storage. Change-Id: I9969871205ac5c438706df41ef1519cb4cd7a964
106 lines
3.4 KiB
PHP
106 lines
3.4 KiB
PHP
<?php
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/**
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* Utility class for various OATH functions
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*
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* @ingroup Extensions
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*/
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class OATHAuthUtils {
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/**
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* Encrypt an aray of variables to put into the user's session. We use this
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* when storing the user's password in their session. We can use json as the
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* serialization format because $plaintextVars is an array of strings.
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* @param array of user input strings
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* @param int user_id, passed to key derivation functions so each user uses
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* distinct encryption and hmac keys
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* @return string encrypted data packet
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*/
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public static function encryptSessionData( array $plaintextVars, $userId ) {
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$keyMaterial = self::getKeyMaterials();
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$keys = self::getUserKeys( $keyMaterial, $userId );
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return self::seal( json_encode( $plaintextVars ), $keys['encrypt'], $keys['hmac'] );
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}
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/**
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* Decrypt an encrypted packet, generated with encryptSessionData
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* @param string Encrypted data packet
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* @return array of strings
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*/
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public static function decryptSessionData( $ciphertext, $userId ) {
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$keyMaterial = self::getKeyMaterials();
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$keys = self::getUserKeys( $keyMaterial, $userId );
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return json_decode( self::unseal( $ciphertext, $keys['encrypt'], $keys['hmac'] ), true );
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}
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/**
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* Get the base secret for this wiki, used to derive all of the encryption
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* keys. When $wgOATHAuthSecret is rotated, users who are part way through the
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* two-step login will get an exception, and have to re-start the login.
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* @return array $keys
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*/
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private static function getKeyMaterials() {
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global $wgOATHAuthSecret, $wgSecretKey;
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return $wgOATHAuthSecret ?: $wgSecretKey;
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}
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/**
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* Generate encryption and hmac keys, unique to this user, based on a single
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* wiki secret. Use a moderate pbkdf2 work factor in case we ever leak keys.
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* @return array including key for encryption and integrity checking
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*/
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private static function getUserKeys( $secret, $userid ) {
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$keymats = hash_pbkdf2( 'sha256', $secret, "oath-$userid", 10001, 64, true );
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return array(
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'encrypt' => substr( $keymats, 0, 32 ),
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'hmac' => substr( $keymats, 32, 32 ),
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);
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}
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/**
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* Actually encrypt the data, using a new random IV, and prepend the hmac
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* of the encrypted data + IV, using a separate hmac key.
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* @return $hmac.$iv.$ciphertext, each component b64 encoded
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*/
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private static function seal( $data, $encKey, $hmacKey ) {
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$iv = MWCryptRand::generate( 16, true );
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$ciphertext = openssl_encrypt(
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$data,
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'aes-256-ctr',
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$encKey,
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OPENSSL_RAW_DATA,
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$iv
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);
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$sealed = base64_encode( $iv ) . '.' . base64_encode( $ciphertext );
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$hmac = hash_hmac( 'sha256', $sealed, $hmacKey, true );
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return base64_encode( $hmac ) . '.' . $sealed;
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}
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/**
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* Decrypt data sealed using seal(). First checks the hmac to prevent various
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* attacks.
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* @return plaintext
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*/
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private static function unseal( $encrypted, $encKey, $hmacKey ) {
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$pieces = explode( '.', $encrypted );
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if ( count( $pieces ) !== 3 ) {
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throw new InvalidArgumentException( 'Invalid sealed-secret format' );
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}
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list( $hmac, $iv, $ciphertext ) = $pieces;
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$integCalc = hash_hmac( 'sha256', $iv . '.' . $ciphertext, $hmacKey, true );
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if ( !hash_equals( $integCalc, base64_decode( $hmac ) ) ) {
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throw new Exception( 'Sealed secret has been tampered with, aborting.' );
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}
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return openssl_decrypt(
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base64_decode( $ciphertext ),
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'aes-256-ctr',
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$encKey,
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OPENSSL_RAW_DATA,
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base64_decode( $iv )
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);
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}
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}
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