streams/Code/Web/HTTPSig.php

<?php

namespace Code\Web;

use DateTime;
use DateTimeZone;
use Code\Lib\ActivityStreams;
use Code\Lib\Activity;
use Code\Lib\Channel;
use Code\Lib\Webfinger;
use Code\Lib\Zotfinger;
use Code\Lib\Libzot;
use Code\Lib\Crypto;
use Code\Lib\Keyutils;

/**
 * @brief Implements HTTP Signatures per draft-cavage-http-signatures-10.
 *
 * @see https://tools.ietf.org/html/draft-cavage-http-signatures-10
 */
class HTTPSig
{

    /**
     * @brief RFC5843
     *
     * @see https://tools.ietf.org/html/rfc5843
     *
     * @param string $body The value to create the digest for
     * @param string $alg hash algorithm (one of 'sha256','sha512')
     * @return string The generated digest header string for $body
     */

    public static function generate_digest_header($body, $alg = 'sha256')
    {

        $digest = base64_encode(hash($alg, $body, true));
        switch ($alg) {
            case 'sha512':
                return 'SHA-512=' . $digest;
            case 'sha256':
            default:
                return 'SHA-256=' . $digest;
                break;
        }
    }


    public static function find_headers($data, &$body)
    {

        // decide if $data arrived via controller submission or curl
        // changes $body for the caller

        if (is_array($data) && array_key_exists('header', $data)) {
            if (!$data['success']) {
                $body = EMPTY_STR;
                return [];
            }

            if (!$data['header']) {
                $body = EMPTY_STR;
                return [];
            }

            $h = new HTTPHeaders($data['header']);
            $headers = $h->fetcharr();
            $body = $data['body'];
            $headers['(request-target)'] = $data['request_target'];
        } else {
            $headers = [];
            $headers['(request-target)'] = strtolower($_SERVER['REQUEST_METHOD']) . ' ' . $_SERVER['REQUEST_URI'];
            $headers['content-type'] = $_SERVER['CONTENT_TYPE'];
            $headers['content-length'] = $_SERVER['CONTENT_LENGTH'];

            foreach ($_SERVER as $k => $v) {
                if (strpos($k, 'HTTP_') === 0) {
                    $field = str_replace('_', '-', strtolower(substr($k, 5)));
                    $headers[$field] = $v;
                }
            }
        }

        //logger('SERVER: ' . print_r($_SERVER,true), LOGGER_ALL);
        //logger('found_headers: ' . print_r($headers,true), LOGGER_ALL);

        return $headers;
    }


    // See draft-cavage-http-signatures-10

    public static function verify($data, $key = '', $keytype = '')
    {

        $body = $data;
        $headers = null;

        $result = [
            'signer' => '',
            'portable_id' => '',
            'header_signed' => false,
            'header_valid' => false,
            'content_signed' => false,
            'content_valid' => false
        ];


        $headers = self::find_headers($data, $body);

        if (!$headers) {
            return $result;
        }

        if (is_array($body)) {
            btlogger('body is array!' . print_r($body, true));
        }


        $sig_block = null;

        if (array_key_exists('signature', $headers)) {
            $sig_block = self::parse_sigheader($headers['signature']);
        } elseif (array_key_exists('authorization', $headers)) {
            $sig_block = self::parse_sigheader($headers['authorization']);
        }

        if (!$sig_block) {
            logger('no signature provided.', LOGGER_DEBUG);
            return $result;
        }

        // Warning: This log statement includes binary data
        // logger('sig_block: ' . print_r($sig_block,true), LOGGER_DATA);

        $result['header_signed'] = true;

        $signed_headers = $sig_block['headers'];
        if (!$signed_headers) {
            $signed_headers = ['date'];
        }
        $signed_data = '';
        foreach ($signed_headers as $h) {
            if (array_key_exists($h, $headers)) {
                $signed_data .= $h . ': ' . $headers[$h] . "\n";
            }
            if ($h === '(created)') {
                if ($sig_block['algorithm'] && (strpos($sig_block['algorithm'], 'rsa') !== false || strpos($sig_block['algorithm'], 'hmac') !== false || strpos($sig_block['algorithm'], 'ecdsa') !== false)) {
                    logger('created not allowed here');
                    return $result;
                }
                if ((!isset($sig_block['(created)'])) || (!intval($sig_block['(created)'])) || intval($sig_block['(created)']) > time()) {
                    logger('created in future');
                    return $result;
                }
                $signed_data .= '(created): ' . $sig_block['(created)'] . "\n";
            }
            if ($h === '(expires)') {
                if ($sig_block['algorithm'] && (strpos($sig_block['algorithm'], 'rsa') !== false || strpos($sig_block['algorithm'], 'hmac') !== false || strpos($sig_block['algorithm'], 'ecdsa') !== false)) {
                    logger('expires not allowed here');
                    return $result;
                }
                if ((!isset($sig_block['(expires)'])) || (!intval($sig_block['(expires)'])) || intval($sig_block['(expires)']) < time()) {
                    logger('signature expired');
                    return $result;
                }
                $signed_data .= '(expires): ' . $sig_block['(expires)'] . "\n";
            }
            if ($h === 'date') {
                $d = new DateTime($headers[$h]);
                $d->setTimeZone(new DateTimeZone('UTC'));
                $dplus = datetime_convert('UTC', 'UTC', 'now + 1 day');
                $dminus = datetime_convert('UTC', 'UTC', 'now - 1 day');
                $c = $d->format('Y-m-d H:i:s');
                if ($c > $dplus || $c < $dminus) {
                    logger('bad time: ' . $c);
                    return $result;
                }
            }
        }
        $signed_data = rtrim($signed_data, "\n");

        $algorithm = null;

        if ($sig_block['algorithm'] === 'rsa-sha256') {
            $algorithm = 'sha256';
        }
        if ($sig_block['algorithm'] === 'rsa-sha512') {
            $algorithm = 'sha512';
        }

        if (!array_key_exists('keyId', $sig_block)) {
            return $result;
        }

        $result['signer'] = $sig_block['keyId'];

        $fkey = self::get_key($key, $keytype, $result['signer']);

        if ($sig_block['algorithm'] === 'hs2019') {
            if (isset($fkey['algorithm'])) {
                if (strpos($fkey['algorithm'], 'rsa-sha256') !== false) {
                    $algorithm = 'sha256';
                }
                if (strpos($fkey['algorithm'], 'rsa-sha512') !== false) {
                    $algorithm = 'sha512';
                }
            }
        }


        if (!($fkey && $fkey['public_key'])) {
            return $result;
        }

        $x = Crypto::verify($signed_data, $sig_block['signature'], $fkey['public_key'], $algorithm);

        logger('verified: ' . intval($x), LOGGER_DEBUG);

        if (!$x) {
            // try again, ignoring the local actor (xchan) cache and refetching the key
            // from its source

            $fkey = self::get_key($key, $keytype, $result['signer'], true);

            if ($fkey && $fkey['public_key']) {
                $y = Crypto::verify($signed_data, $sig_block['signature'], $fkey['public_key'], $algorithm);
                logger('verified: (cache reload) ' . intval($y), LOGGER_DEBUG);
            }

            if (!$y) {
                logger('verify failed for ' . $result['signer'] . ' alg=' . $algorithm . (($fkey['public_key']) ? '' : ' no key'));
                $sig_block['signature'] = base64_encode($sig_block['signature']);
                logger('affected sigblock: ' . print_r($sig_block, true));
                logger('headers: ' . print_r($headers, true));
                logger('server: ' . print_r($_SERVER, true));
                return $result;
            }
        }

        $result['portable_id'] = $fkey['portable_id'];
        $result['header_valid'] = true;

        if (in_array('digest', $signed_headers)) {
            $result['content_signed'] = true;
            $digest = explode('=', $headers['digest'], 2);
            if ($digest[0] === 'SHA-256') {
                $hashalg = 'sha256';
            }
            if ($digest[0] === 'SHA-512') {
                $hashalg = 'sha512';
            }

            if (base64_encode(hash($hashalg, $body, true)) === $digest[1]) {
                $result['content_valid'] = true;
            }

            logger('Content_Valid: ' . (($result['content_valid']) ? 'true' : 'false'));
            if (!$result['content_valid']) {
                logger('invalid content signature: data ' . print_r($data, true));
                logger('invalid content signature: headers ' . print_r($headers, true));
                logger('invalid content signature: body ' . print_r($body, true));
            }
        }

        return $result;
    }

    public static function get_key($key, $keytype, $id, $force = false)
    {    
        if ($key) {
            if (function_exists($key)) {
                return $key($id);
            }
            return ['public_key' => $key];
        }

        if ($keytype === 'zot6') {
            $key = self::get_zotfinger_key($id, $force);
            if ($key) {
                return $key;
            }
        }


        if (strpos($id, '#') === false) {
            $key = self::get_webfinger_key($id, $force);
            if ($key) {
                return $key;
            }
        }

        $key = self::get_activitystreams_key($id, $force);
        return $key;
    }


    public static function convertKey($key)
    {

        if (strstr($key, 'RSA ')) {
            return Keyutils::rsatopem($key);
        } elseif (substr($key, 0, 5) === 'data:') {
            return Keyutils::convertSalmonKey($key);
        } else {
            return $key;
        }
    }


    /**
     * @brief
     *
     * @param string $id
     * @return bool|string
     *   false if no pub key found, otherwise return the pub key
     */

    public static function get_activitystreams_key($id, $force = false)
    {

        // Check the local cache first, but remove any fragments like #main-key since these won't be present in our cached data

        $cache_url = ((strpos($id, '#')) ? substr($id, 0, strpos($id, '#')) : $id);

        // $force is used to ignore the local cache and only use the remote data; for instance the cached key might be stale

        if (!$force) {
            $x = q(
                "select * from xchan left join hubloc on xchan_hash = hubloc_hash where ( hubloc_addr = '%s' or hubloc_id_url = '%s' or hubloc_hash = '%s') and hubloc_deleted = 0 order by hubloc_id desc",
                dbesc(str_replace('acct:', '', $cache_url)),
                dbesc($cache_url),
                dbesc($cache_url)
            );

            if ($x) {
                $best = Libzot::zot_record_preferred($x);
            }

            if ($best && $best['xchan_pubkey']) {
                return ['portable_id' => $best['xchan_hash'], 'public_key' => $best['xchan_pubkey'], 'algorithm' => get_xconfig($best['xchan_hash'], 'system', 'signing_algorithm'), 'hubloc' => $best];
            }
        }

        // The record wasn't in cache. Fetch it now.

        $r = Activity::fetch($id);
        $signatureAlgorithm = EMPTY_STR;

        if ($r) {
            if (array_key_exists('publicKey', $r) && array_key_exists('publicKeyPem', $r['publicKey']) && array_key_exists('id', $r['publicKey'])) {
                if ($r['publicKey']['id'] === $id || $r['id'] === $id) {
                    $portable_id = ((array_key_exists('owner', $r['publicKey'])) ? $r['publicKey']['owner'] : EMPTY_STR);

                    // the w3c sec context has conflicting names and no defined values for this property except
                    // "http://www.w3.org/2000/09/xmldsig#rsa-sha1"

                    // Since the names conflict, it could mess up LD-signatures but we will accept both, and at this
                    // time we will only look for the substrings 'rsa-sha256' and 'rsa-sha512' within those properties.
                    // We will also accept a toplevel 'sigAlgorithm' regardless of namespace with the same constraints.
                    // Default to rsa-sha256 if we can't figure out. If they're sending 'hs2019' we have to
                    // look for something.

                    if (isset($r['publicKey']['signingAlgorithm'])) {
                        $signatureAlgorithm = $r['publicKey']['signingAlgorithm'];
                        set_xconfig($portable_id, 'system', 'signing_algorithm', $signatureAlgorithm);
                    }
                    if (isset($r['publicKey']['signatureAlgorithm'])) {
                        $signatureAlgorithm = $r['publicKey']['signatureAlgorithm'];
                        set_xconfig($portable_id, 'system', 'signing_algorithm', $signatureAlgorithm);
                    }

                    if (isset($r['sigAlgorithm'])) {
                        $signatureAlgorithm = $r['sigAlgorithm'];
                        set_xconfig($portable_id, 'system', 'signing_algorithm', $signatureAlgorithm);
                    }

                    return ['public_key' => self::convertKey($r['publicKey']['publicKeyPem']), 'portable_id' => $portable_id, 'algorithm' => (($signatureAlgorithm) ? $signatureAlgorithm : 'rsa-sha256'), 'hubloc' => []];
                }
            }
        }

        // No key was found

        return false;
    }


    public static function get_webfinger_key($id, $force = false)
    {

        if (!$force) {
            $x = q(
                "select * from xchan left join hubloc on xchan_hash = hubloc_hash where ( hubloc_addr = '%s' or hubloc_id_url = '%s' or hubloc_hash = '%s') and hubloc_deleted = 0 order by hubloc_id desc",
                dbesc(str_replace('acct:', '', $id)),
                dbesc($id),
                dbesc($id)
            );

            if ($x) {
                $best = Libzot::zot_record_preferred($x);
            }

            if ($best && $best['xchan_pubkey']) {
                return ['portable_id' => $best['xchan_hash'], 'public_key' => $best['xchan_pubkey'], 'algorithm' => get_xconfig($best['xchan_hash'], 'system', 'signing_algorithm'), 'hubloc' => $best];
            }
        }

        $wf = Webfinger::exec($id);
        $key = ['portable_id' => '', 'public_key' => '', 'algorithm' => '', 'hubloc' => []];
        if ($wf) {
            if (array_key_exists('properties', $wf) && array_key_exists('https://w3id.org/security/v1#publicKeyPem', $wf['properties'])) {
                $key['public_key'] = self::convertKey($wf['properties']['https://w3id.org/security/v1#publicKeyPem']);
            }
            if (array_key_exists('links', $wf) && is_array($wf['links'])) {
                foreach ($wf['links'] as $l) {
                    if (!(is_array($l) && array_key_exists('rel', $l))) {
                        continue;
                    }

                    if (in_array($l['rel'], ['http://purl.org/nomad', 'http://purl.org/zot/protocol/6.0']) && array_key_exists('href',$l) && $l['href'] !== EMPTY_STR) {
                        // The third argument to Zotfinger::exec() tells it not to verify signatures
                        // Since we're inside a function that is fetching keys with which to verify signatures,
                        // this is necessary to prevent infinite loops.

                        $z = Zotfinger::exec($l['href'], null, false);
                        if ($z) {
                            $i = Libzot::import_xchan($z['data']);
                            if ($i['success']) {
                                $key['portable_id'] = $i['hash'];

                                $x = q(
                                    "select * from xchan left join hubloc on xchan_hash = hubloc_hash where hubloc_id_url = '%s' and hubloc_deleted = 0 order by hubloc_id desc limit 1",
                                    dbesc($l['href'])
                                );
                                if ($x) {
                                    $key['hubloc'] = $x[0];
                                }
                                $key['algorithm'] = get_xconfig($i['hash'], 'system', 'signing_algorithm');
                            }
                        }
                    }


    
                    if ($l['rel'] === 'magic-public-key' && array_key_exists('href', $l) && $key['public_key'] === EMPTY_STR) {
                        $key['public_key'] = self::convertKey($l['href']);
                    }
                }
            }
        }
        return (($key['public_key']) ? $key : false);
    }


    public static function get_zotfinger_key($id, $force = false)
    {

        if (!$force) {
            $x = q(
                "select * from xchan left join hubloc on xchan_hash = hubloc_hash where ( hubloc_addr = '%s' or hubloc_id_url = '%s' ) and hubloc_network in ('nomad','zot6') and hubloc_deleted = 0 order by hubloc_id desc",
                dbesc(str_replace('acct:', '', $id)),
                dbesc($id)
            );

            if ($x) {
                $best = Libzot::zot_record_preferred($x);
            }

            if ($best && $best['xchan_pubkey']) {
                return ['portable_id' => $best['xchan_hash'], 'public_key' => $best['xchan_pubkey'], 'algorithm' => get_xconfig($best['xchan_hash'], 'system', 'signing_algorithm'), 'hubloc' => $best];
            }
        }

        $wf = Webfinger::exec($id);
        $key = ['portable_id' => '', 'public_key' => '', 'algorithm' => '', 'hubloc' => []];

        if ($wf) {
            if (array_key_exists('properties', $wf) && array_key_exists('https://w3id.org/security/v1#publicKeyPem', $wf['properties'])) {
                $key['public_key'] = self::convertKey($wf['properties']['https://w3id.org/security/v1#publicKeyPem']);
            }
            if (array_key_exists('links', $wf) && is_array($wf['links'])) {
                foreach ($wf['links'] as $l) {
                    if (!(is_array($l) && array_key_exists('rel', $l))) {
                        continue;
                    }
                    if (in_array($l['rel'], ['http://purl.org/nomad', 'http://purl.org/zot/protocol/6.0']) && array_key_exists('href',$l) && $l['href'] !== EMPTY_STR) {
                        // The third argument to Zotfinger::exec() tells it not to verify signatures
                        // Since we're inside a function that is fetching keys with which to verify signatures,
                        // this is necessary to prevent infinite loops.

                        $z = Zotfinger::exec($l['href'], null, false);
                        if ($z) {
                            $i = Libzot::import_xchan($z['data']);
                            if ($i['success']) {
                                $key['portable_id'] = $i['hash'];

                                $x = q(
                                    "select * from xchan left join hubloc on xchan_hash = hubloc_hash where hubloc_id_url = '%s' and hubloc_deleted = 0 order by hubloc_id desc limit 1",
                                    dbesc($l['href'])
                                );
                                if ($x) {
                                    $key['hubloc'] = $x[0];
                                }
                                $key['algorithm'] = get_xconfig($i['hash'], 'system', 'signing_algorithm');
                            }
                        }
                    }
                    if ($l['rel'] === 'magic-public-key' && array_key_exists('href', $l) && $key['public_key'] === EMPTY_STR) {
                        $key['public_key'] = self::convertKey($l['href']);
                    }
                }
            }
        }

        return (($key['public_key']) ? $key : false);
    }


    /**
     * @brief
     *
     * @param array $head
     * @param string $prvkey
     * @param string $keyid (optional, default '')
     * @param bool $auth (optional, default false)
     * @param string $alg (optional, default 'sha256')
     * @param array $encryption [ 'key', 'algorithm' ] or false
     * @return array
     */
    public static function create_sig($head, $prvkey, $keyid = EMPTY_STR, $auth = false, $alg = 'sha256', $encryption = false)
    {

        $return_headers = [];

    
        if ($alg === 'sha256') {
            $algorithm = 'rsa-sha256';
        }
        if ($alg === 'sha512') {
            $algorithm = 'rsa-sha512';
        }

        // Use hs2019 by default.
    
        if (get_config('system', 'use_hs2019', false) && $algorithm === 'rsa-sha256') {
            $algorithm = 'hs2019';
        }

        $x = self::sign($head, $prvkey, $alg);

        $headerval = 'keyId="' . $keyid . '",algorithm="' . $algorithm . '",headers="' . $x['headers'] . '",signature="' . $x['signature'] . '"';

        if ($encryption) {
            $x = Crypto::encapsulate($headerval, $encryption['key'], $encryption['algorithm']);
            if (is_array($x)) {
                $headerval = 'iv="' . $x['iv'] . '",key="' . $x['key'] . '",alg="' . $x['alg'] . '",data="' . $x['data'] . '"';
            }
        }

        if ($auth) {
            $sighead = 'Authorization: Signature ' . $headerval;
        } else {
            $sighead = 'Signature: ' . $headerval;
        }

        if ($head) {
            foreach ($head as $k => $v) {
                // strip the request-target virtual header from the output headers
                if ($k === '(request-target)') {
                    continue;
                }
                $return_headers[] = $k . ': ' . $v;
            }
        }
        $return_headers[] = $sighead;

        return $return_headers;
    }

    /**
     * @brief set headers
     *
     * @param array $headers
     * @return void
     */

    public static function set_headers($headers)
    {
        if ($headers && is_array($headers)) {
            foreach ($headers as $h) {
                header($h);
            }
        }
    }


    /**
     * @brief
     *
     * @param array $head
     * @param string $prvkey
     * @param string $alg (optional) default 'sha256'
     * @return array
     */

    public static function sign($head, $prvkey, $alg = 'sha256')
    {

        $ret = [];

        $headers = '';
        $fields = '';

        logger('signing: ' . print_r($head, true), LOGGER_DATA);

        if ($head) {
            foreach ($head as $k => $v) {
                $headers .= strtolower($k) . ': ' . trim($v) . "\n";
                if ($fields) {
                    $fields .= ' ';
                }
                $fields .= strtolower($k);
            }
            // strip the trailing linefeed
            $headers = rtrim($headers, "\n");
        }

        $sig = base64_encode(Crypto::sign($headers, $prvkey, $alg));

        $ret['headers'] = $fields;
        $ret['signature'] = $sig;

        return $ret;
    }

    /**
     * @brief
     *
     * @param string $header
     * @return array associate array with
     *   - \e string \b keyID
     *   - \e string \b algorithm
     *   - \e array  \b headers
     *   - \e string \b signature
     */

    public static function parse_sigheader($header)
    {

        $ret = [];
        $matches = [];

        // if the header is encrypted, decrypt with (default) site private key and continue

        if (preg_match('/iv="(.*?)"/ism', $header, $matches)) {
            $header = self::decrypt_sigheader($header);
        }

        if (preg_match('/keyId="(.*?)"/ism', $header, $matches)) {
            $ret['keyId'] = $matches[1];
        }
        if (preg_match('/created=([0-9]*)/ism', $header, $matches)) {
            $ret['(created)'] = $matches[1];
        }
        if (preg_match('/expires=([0-9]*)/ism', $header, $matches)) {
            $ret['(expires)'] = $matches[1];
        }
        if (preg_match('/algorithm="(.*?)"/ism', $header, $matches)) {
            $ret['algorithm'] = $matches[1];
        }
        if (preg_match('/headers="(.*?)"/ism', $header, $matches)) {
            $ret['headers'] = explode(' ', $matches[1]);
        }
        if (preg_match('/signature="(.*?)"/ism', $header, $matches)) {
            $ret['signature'] = base64_decode(preg_replace('/\s+/', '', $matches[1]));
        }

        if (($ret['signature']) && ($ret['algorithm']) && (!$ret['headers'])) {
            $ret['headers'] = ['date'];
        }

        return $ret;
    }


    /**
     * @brief
     *
     * @param string $header
     * @param string $prvkey (optional), if not set use site private key
     * @return array|string associative array, empty string if failue
     *   - \e string \b iv
     *   - \e string \b key
     *   - \e string \b alg
     *   - \e string \b data
     */

    public static function decrypt_sigheader($header, $prvkey = null)
    {

        $iv = $key = $alg = $data = null;

        if (!$prvkey) {
            $prvkey = get_config('system', 'prvkey');
        }

        $matches = [];

        if (preg_match('/iv="(.*?)"/ism', $header, $matches)) {
            $iv = $matches[1];
        }
        if (preg_match('/key="(.*?)"/ism', $header, $matches)) {
            $key = $matches[1];
        }
        if (preg_match('/alg="(.*?)"/ism', $header, $matches)) {
            $alg = $matches[1];
        }
        if (preg_match('/data="(.*?)"/ism', $header, $matches)) {
            $data = $matches[1];
        }

        if ($iv && $key && $alg && $data) {
            return Crypto::unencapsulate(['encrypted' => true, 'iv' => $iv, 'key' => $key, 'alg' => $alg, 'data' => $data], $prvkey);
        }

        return '';
    }
}