U2F::fixSignatureUnusedBits() - Code Metrics - Inspection of "Using Proton Coding Standard" - ProtonMail/php-u2flib-server - Measure and Improve Code Quality continuously with Scrutinizer

Passed
Pull Request — master (#5)

by Thomas
created 2019-05-07 15:20 UTC
U2F::fixSignatureUnusedBits() A

↳ Parent: U2F
Complexity

Conditions	2
Paths	2
Size

Total Lines	6
Code Lines	3
Duplication

Lines	0
Ratio	0 %
Importance

Changes
Metric	Value
cc	2
eloc	3
nc	2
nop	1
dl	0
loc	6
rs	10
c	0
b	0
f	0
<?php

namespace u2flib_server;

/* Copyright (c) 2014 Yubico AB
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

use Exception;
use InvalidArgumentException;

/**
 * Constant for the version of the u2f protocol
 */
const U2F_VERSION = 'U2F_V2';

/**
 * Constant for the type value in registration clientData
 */
const REQUEST_TYPE_REGISTER = 'navigator.id.finishEnrollment';

/**
 * Constant for the type value in authentication clientData
 */
const REQUEST_TYPE_AUTHENTICATE = 'navigator.id.getAssertion';

/**
 * Error for the authentication message not matching any outstanding
 * authentication request
 */
const ERR_NO_MATCHING_REQUEST = 1;

/**
 * Error for the authentication message not matching any registration
 */
const ERR_NO_MATCHING_REGISTRATION = 2;

/**
 * Error for the signature on the authentication message not verifying with
 * the correct key
 */
const ERR_AUTHENTICATION_FAILURE = 3;

/**
 * Error for the challenge in the registration message not matching the
 * registration challenge
 */
const ERR_UNMATCHED_CHALLENGE = 4;

/**
 * Error for the attestation signature on the registration message not
 * verifying
 */
const ERR_ATTESTATION_SIGNATURE = 5;

/**
 * Error for the attestation verification not verifying
 */
const ERR_ATTESTATION_VERIFICATION = 6;

/**
 * Error for not getting good random from the system
 */
const ERR_BAD_RANDOM = 7;

/**
 * Error when the counter is lower than expected
 */
const ERR_COUNTER_TOO_LOW = 8;

/**
 * Error decoding public key
 */
const ERR_PUBKEY_DECODE = 9;

/**
 * Error user-agent returned error
 */
const ERR_BAD_UA_RETURNING = 10;

/**
 * Error old OpenSSL version
 */
const ERR_OLD_OPENSSL = 11;

/**
 * Error for the origin not matching the appId
 */
const ERR_NO_MATCHING_ORIGIN = 12;

/**
 * Error for the type in clientData being invalid
 */
const ERR_BAD_TYPE = 13;

/**
 * Error for bad user presence byte value
 */
const ERR_BAD_USER_PRESENCE = 14;

/**
 * @internal
 */
const PUBKEY_LEN = 65;

class U2F
{
    /**
     * @var string
     */
    private $appId;

    /**
     * @var string|string
     */
    private $attestDir;

    /**
     * @var array
     */
    private $facetIds;

    /**
     * @internal
     */
    private const FIXCERTS = [
        '349bca1031f8c82c4ceca38b9cebf1a69df9fb3b94eed99eb3fb9aa3822d26e8',
        'dd574527df608e47ae45fbba75a2afdd5c20fd94a02419381813cd55a2a3398f',
        '1d8764f0f7cd1352df6150045c8f638e517270e8b5dda1c63ade9c2280240cae',
        'd0edc9a91a1677435a953390865d208c55b3183c6759c9b5a7ff494c322558eb',
        '6073c436dcd064a48127ddbf6032ac1a66fd59a0c24434f070d4e564c124c897',
        'ca993121846c464d666096d35f13bf44c1b05af205f9b4a1e00cf6cc10c5e511',
    ];

    /**
     * @param string      $appId     Application id for the running application
     * @param string|null $attestDir Directory where trusted attestation roots may be found
     * @param array|null  $facetIds  List of trusted Facet IDs
     * @throws Error If OpenSSL older than 1.0.0 is used
     */
    public function __construct($appId, $attestDir = null, $facetIds = null)
    {
        if (OPENSSL_VERSION_NUMBER < 0x10000000) {
            throw new Error(
                'OpenSSL has to be at least version 1.0.0, this is ' . OPENSSL_VERSION_TEXT,
                ERR_OLD_OPENSSL
            );
        }
        $this->appId = $appId;
        $this->attestDir = $attestDir;

        if (!is_array($facetIds)) {
            $facetIds = [$appId];
        }
        $this->facetIds = $facetIds;
    }

    /**
     * Called to get a registration request to send to a user.
     * Returns an array of one registration request and a array of sign requests.
     *
     * @param array $registrations  List of current registrations for this
     *                              user, to prevent the user from registering the same authenticator several
     *                              times.
     * @return array An array of two elements, the first containing a
     *                              RegisterRequest the second being an array of SignRequest
     * @throws Exception
     */
    public function getRegisterData(array $registrations = []): array
    {
        $challenge = $this->createChallenge();
        $request = new RegisterRequest($challenge, $this->appId);
        $signs = $this->getAuthenticateData($registrations);
        return [$request, $signs];
    }

    /**
     * Called to verify and unpack a registration message.
     *
     * @param RegisterRequest $request      this is a reply to
     * @param object          $response     response from a user
     * @param bool            $includeCert  set to true if the attestation certificate should be
     *                                      included in the returned Registration object
     * @return Registration
     * @throws Error
     */
    public function doRegister($request, $response, $includeCert = true): ?Registration
    {
        if (!is_object($request)) {
            throw new InvalidArgumentException('$request of doRegister() method only accepts object.');
        }

        if (!is_object($response)) {
            throw new InvalidArgumentException('$response of doRegister() method only accepts object.');
        }

        if (property_exists($response, 'errorCode') && $response->errorCode !== 0) {
            throw new Error('User-agent returned error. Error code: ' . $response->errorCode, ERR_BAD_UA_RETURNING);
        }

        if (!is_bool($includeCert)) {

            throw new InvalidArgumentException('$include_cert of doRegister() method only accepts boolean.');
        }

        $rawReg = $this->base64uDecode($response->registrationData);
        $regData = array_values(unpack('C*', $rawReg));
        $regData = array_values(/** @scrutinizer ignore-type */ unpack('C*', $rawReg));
        $clientData = $this->base64uDecode($response->clientData);
        $cli = json_decode($clientData, false);

        if ($cli->challenge !== $request->challenge) {
            throw new Error('Registration challenge does not match', ERR_UNMATCHED_CHALLENGE);
        }

        if (isset($cli->typ) && $cli->typ !== REQUEST_TYPE_REGISTER) {
            throw new Error('ClientData type is invalid', ERR_BAD_TYPE);
        }

        if (isset($cli->origin) && !in_array($cli->origin, $this->facetIds, true)) {
            throw new Error('App ID does not match the origin', ERR_NO_MATCHING_ORIGIN);
        }

        $registration = new Registration();
        $offs = 1;
        $pubKey = substr($rawReg, $offs, PUBKEY_LEN);
        $offs += PUBKEY_LEN;
        // decode the pubKey to make sure it's good
        $tmpKey = $this->pubkeyToPem($pubKey);
        if ($tmpKey === null) {
            throw new Error('Decoding of public key failed', ERR_PUBKEY_DECODE);
        }
        $registration->publicKey = base64_encode($pubKey);
        $khLen = $regData[$offs++];
        $kh = substr($rawReg, $offs, $khLen);
        $offs += $khLen;
        $registration->keyHandle = $this->base64uEncode($kh);

        // length of certificate is stored in byte 3 and 4 (excluding the first 4 bytes)
        $certLen = 4;
        $certLen += ($regData[$offs + 2] << 8);
        $certLen += $regData[$offs + 3];

        $rawCert = $this->fixSignatureUnusedBits(substr($rawReg, $offs, $certLen));
        $offs += $certLen;
        $pemCert = "-----BEGIN CERTIFICATE-----\r\n";
        $pemCert .= chunk_split(base64_encode($rawCert), 64);
        $pemCert .= '-----END CERTIFICATE-----';
        if ($includeCert) {
            $registration->certificate = base64_encode($rawCert);
        }
        if ($this->attestDir) {
            if (openssl_x509_checkpurpose($pemCert, -1, $this->getCerts()) !== true) {
                throw new Error('Attestation certificate can not be validated', ERR_ATTESTATION_VERIFICATION);
            }
        }

        if (!openssl_pkey_get_public($pemCert)) {
            throw new Error('Decoding of public key failed', ERR_PUBKEY_DECODE);
        }
        $signature = substr($rawReg, $offs);

        $dataToVerify = pack('C', 0);
        $dataToVerify .= hash('sha256', $request->appId, true);
        $dataToVerify .= hash('sha256', $clientData, true);
        $dataToVerify .= $kh;
        $dataToVerify .= $pubKey;

        if (openssl_verify($dataToVerify, $signature, $pemCert, 'sha256') === 1) {
        if (openssl_verify($dataToVerify, $signature, $pemCert, /** @scrutinizer ignore-type */ 'sha256') === 1) {
            return $registration;
        }

        throw new Error('Attestation signature does not match', ERR_ATTESTATION_SIGNATURE);
    }

    /**
     * Called to get an authentication request.
     *
     * @param array $registrations An array of the registrations to create authentication requests for.
     * @return array An array of SignRequest
     * @throws Exception
     */
    public function getAuthenticateData(array $registrations): array
    {
        $sigs = [];
        $challenge = $this->createChallenge();
        foreach ($registrations as $reg) {
            if (!is_object($reg)) {
                throw new InvalidArgumentException(
                    '$registrations of getAuthenticateData() method only accepts array of object.'
                );
            }
            /**
             * @var Registration $reg
             */

            $sig = new SignRequest();
            $sig->appId = $this->appId;
            $sig->keyHandle = $reg->keyHandle;
            $sig->challenge = $challenge;
            $sigs[] = $sig;
        }
        return $sigs;
    }

    /**
     * Called to verify an authentication response.
     *
     * The Registration object returned on success contains an updated counter
     * that should be saved for future authentications.
     * If the Error returned is ERR_COUNTER_TOO_LOW this is an indication of
     * token cloning or similar and appropriate action should be taken.
     *
     * @param array  $requests      An array of outstanding authentication requests
     * @param array  $registrations An array of current registrations
     * @param object $response      A response from the authenticator
     * @return Registration
     * @throws Error
     */
    public function doAuthenticate(array $requests, array $registrations, $response): ?Registration
    {
        if (!is_object($response)) {
            throw new InvalidArgumentException('$response of doAuthenticate() method only accepts object.');
        }

        if (property_exists($response, 'errorCode') && $response->errorCode !== 0) {
            throw new Error('User-agent returned error. Error code: ' . $response->errorCode, ERR_BAD_UA_RETURNING);
        }

        /**
         * @var object|null $req
         */
        $req = null;

        /**
         * @var object|null $reg
         */
        $reg = null;

        $clientData = $this->base64uDecode($response->clientData);
        $decodedClient = json_decode($clientData, false);

        if (isset($decodedClient->typ) && $decodedClient->typ !== REQUEST_TYPE_AUTHENTICATE) {
            throw new Error('ClientData type is invalid', ERR_BAD_TYPE);
        }

        foreach ($requests as $req) {
            if (!is_object($req)) {
                throw new InvalidArgumentException(
                    '$requests of doAuthenticate() method only accepts array of object.'
                );
            }

            if ($req->keyHandle === $response->keyHandle && $req->challenge === $decodedClient->challenge) {
                break;
            }

            $req = null;
        }
        if ($req === null) {
            throw new Error('No matching request found', ERR_NO_MATCHING_REQUEST);
        }
        if (isset($decodedClient->origin) && !in_array($decodedClient->origin, $this->facetIds, true)) {
            throw new Error('App ID does not match the origin', ERR_NO_MATCHING_ORIGIN);
        }
        foreach ($registrations as $reg) {
            if (!is_object($reg)) {
                throw new InvalidArgumentException(
                    '$registrations of doAuthenticate() method only accepts array of object.'
                );
            }

            if ($reg->keyHandle === $response->keyHandle) {
                break;
            }
            $reg = null;
        }
        if ($reg === null) {
            throw new Error('No matching registration found', ERR_NO_MATCHING_REGISTRATION);
        }
        $pemKey = $this->pubkeyToPem($this->base64uDecode($reg->publicKey));
        if ($pemKey === null) {
            throw new Error('Decoding of public key failed', ERR_PUBKEY_DECODE);
        }

        $signData = $this->base64uDecode($response->signatureData);
        $dataToVerify = hash('sha256', $req->appId, true);
        $dataToVerify .= substr($signData, 0, 5);
        $dataToVerify .= hash('sha256', $clientData, true);
        $signature = substr($signData, 5);

        if (openssl_verify($dataToVerify, $signature, $pemKey, 'sha256') === 1) {
        if (openssl_verify($dataToVerify, $signature, $pemKey, /** @scrutinizer ignore-type */ 'sha256') === 1) {
            $upb = unpack('Cupb', substr($signData, 0, 1));
            if ($upb['upb'] !== 1) {
                throw new Error('User presence byte value is invalid', ERR_BAD_USER_PRESENCE);
            }
            $ctr = unpack('Nctr', substr($signData, 1, 4));
            $counter = $ctr['ctr'];
            /* TODO: wrap-around should be handled somehow.. */
            if ($counter > $reg->counter) {
                $reg->counter = $counter;
                return self::castObjectToRegistration($reg);
            }

            throw new Error('Counter too low.', ERR_COUNTER_TOO_LOW);
        }

        throw new Error('Authentication failed', ERR_AUTHENTICATION_FAILURE);
    }

    /**
     * @param object $object
     * @return Registration
     */
    protected static function castObjectToRegistration($object): Registration
    {
        $reg = new Registration();
        if (isset($object->publicKey)) {
            $reg->publicKey = $object->publicKey;
        }
        if (isset($object->certificate)) {
            $reg->certificate = $object->certificate;
        }
        if (isset($object->counter)) {
            $reg->counter = $object->counter;
        }
        if (isset($object->keyHandle)) {
            $reg->keyHandle = $object->keyHandle;
        }
        return $reg;
    }

    /**
     * @return array
     */
    private function getCerts(): array
    {
        $files = [];
        $dir = $this->attestDir;
        if ($dir !== null && is_dir($dir) && $handle = opendir($dir)) {
            while (false !== ($entry = readdir($handle))) {
                if (is_file("$dir/$entry")) {
                    $files[] = "$dir/$entry";
                }
            }
            closedir($handle);
        } elseif (is_file((string) $dir)) {
            $files[] = (string) $dir;
        }
        return $files;
    }

    /**
     * Retrieves the challenge from a raw response.
     *
     * @param object $response A response from the authenticator
     * @return mixed the decoded client data
     */
    public function extractChallenge($response)
    {
        $clientData = $this->base64uDecode($response->clientData);
        return json_decode($clientData, false)->challenge;
    }

    /**
     * @param string $data
     * @return string
     */
    private function base64uEncode($data): string
    {
        return trim(strtr(base64_encode($data), '+/', '-_'), '=');
    }

    /**
     * @param string $data
     * @return string
     */
    private function base64uDecode($data): string
    {
        return base64_decode(strtr($data, '-_', '+/'));
    }

    /**
     * @param string $key
     * @return string|null
     */
    private function pubkeyToPem($key): ?string
    {
        if (strlen($key) !== PUBKEY_LEN || $key[0] !== "\x04") {
            return null;
        }

        /*
         * Convert the public key to binary DER format first
         * Using the ECC SubjectPublicKeyInfo OIDs from RFC 5480
         *
         *  SEQUENCE(2 elem)                        30 59
         *   SEQUENCE(2 elem)                       30 13
         *    OID1.2.840.10045.2.1 (id-ecPublicKey) 06 07 2a 86 48 ce 3d 02 01
         *    OID1.2.840.10045.3.1.7 (secp256r1)    06 08 2a 86 48 ce 3d 03 01 07
         *   BIT STRING(520 bit)                    03 42 ..key..
         */
        $der = "\x30\x59\x30\x13\x06\x07\x2a\x86\x48\xce\x3d\x02\x01";
        $der .= "\x06\x08\x2a\x86\x48\xce\x3d\x03\x01\x07\x03\x42";
        $der .= "\0" . $key;

        $pem = "-----BEGIN PUBLIC KEY-----\r\n";
        $pem .= chunk_split(base64_encode($der), 64);
        $pem .= '-----END PUBLIC KEY-----';

        return $pem;
    }

    /**
     * called to create a challenge. For testing purposes, the U2F class can be inherited,
     * and this method overridden to always return the same challenge.
     *
     * @return string the challenge
     * @throws Exception if openssl doesn't have cryptographically strong source
     */
    protected function createChallenge(): string
    {
        $challenge = random_bytes(32);
        $challenge = $this->base64uEncode($challenge);

        return $challenge;
    }

    /**
     * Fixes a certificate where the signature contains unused bits.
     *
     * @param string $cert
     * @return mixed
     */
    private function fixSignatureUnusedBits($cert)
    {
        if (in_array(hash('sha256', $cert), static::FIXCERTS, true)) {
            $cert[strlen($cert) - 257] = "\0";
        }
        return $cert;
    }
}

ProtonMail / php-u2flib-server

Pull Request — master (#5)

U2F::fixSignatureUnusedBits() A

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