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Diffstat (limited to 'src/usr/local/www/csrf/csrf-magic.php')
| -rw-r--r-- | src/usr/local/www/csrf/csrf-magic.php | 403 |
1 files changed, 403 insertions, 0 deletions
diff --git a/src/usr/local/www/csrf/csrf-magic.php b/src/usr/local/www/csrf/csrf-magic.php new file mode 100644 index 0000000..58f4eba --- /dev/null +++ b/src/usr/local/www/csrf/csrf-magic.php @@ -0,0 +1,403 @@ +<?php + +/** + * @file + * + * csrf-magic is a PHP library that makes adding CSRF-protection to your + * web applications a snap. No need to modify every form or create a database + * of valid nonces; just include this file at the top of every + * web-accessible page (or even better, your common include file included + * in every page), and forget about it! (There are, of course, configuration + * options for advanced users). + * + * This library is PHP4 and PHP5 compatible. + */ + +// CONFIGURATION: + +/** + * By default, when you include this file csrf-magic will automatically check + * and exit if the CSRF token is invalid. This will defer executing + * csrf_check() until you're ready. You can also pass false as a parameter to + * that function, in which case the function will not exit but instead return + * a boolean false if the CSRF check failed. This allows for tighter integration + * with your system. + */ +$GLOBALS['csrf']['defer'] = false; + +/** + * This is the amount of seconds you wish to allow before any token becomes + * invalid; the default is two hours, which should be more than enough for + * most websites. + */ +$GLOBALS['csrf']['expires'] = 7200; + +/** + * Callback function to execute when there's the CSRF check fails and + * $fatal == true (see csrf_check). This will usually output an error message + * about the failure. + */ +$GLOBALS['csrf']['callback'] = 'csrf_callback'; + +/** + * Whether or not to include our JavaScript library which also rewrites + * AJAX requests on this domain. Set this to the web path. This setting only works + * with supported JavaScript libraries in Internet Explorer; see README.txt for + * a list of supported libraries. + */ +$GLOBALS['csrf']['rewrite-js'] = false; + +/** + * A secret key used when hashing items. Please generate a random string and + * place it here. If you change this value, all previously generated tokens + * will become invalid. + */ +$GLOBALS['csrf']['secret'] = ''; +// nota bene: library code should use csrf_get_secret() and not access +// this global directly + +/** + * Set this to false to disable csrf-magic's output handler, and therefore, + * its rewriting capabilities. If you're serving non HTML content, you should + * definitely set this false. + */ +$GLOBALS['csrf']['rewrite'] = true; + +/** + * Whether or not to use IP addresses when binding a user to a token. This is + * less reliable and less secure than sessions, but is useful when you need + * to give facilities to anonymous users and do not wish to maintain a database + * of valid keys. + */ +$GLOBALS['csrf']['allow-ip'] = true; + +/** + * If this information is available, use the cookie by this name to determine + * whether or not to allow the request. This is a shortcut implementation + * very similar to 'key', but we randomly set the cookie ourselves. + */ +$GLOBALS['csrf']['cookie'] = '__csrf_cookie'; + +/** + * If this information is available, set this to a unique identifier (it + * can be an integer or a unique username) for the current "user" of this + * application. The token will then be globally valid for all of that user's + * operations, but no one else. This requires that 'secret' be set. + */ +$GLOBALS['csrf']['user'] = false; + +/** + * This is an arbitrary secret value associated with the user's session. This + * will most probably be the contents of a cookie, as an attacker cannot easily + * determine this information. Warning: If the attacker knows this value, they + * can easily spoof a token. This is a generic implementation; sessions should + * work in most cases. + * + * Why would you want to use this? Lets suppose you have a squid cache for your + * website, and the presence of a session cookie bypasses it. Let's also say + * you allow anonymous users to interact with the website; submitting forms + * and AJAX. Previously, you didn't have any CSRF protection for anonymous users + * and so they never got sessions; you don't want to start using sessions either, + * otherwise you'll bypass the Squid cache. Setup a different cookie for CSRF + * tokens, and have Squid ignore that cookie for get requests, for anonymous + * users. (If you haven't guessed, this scheme was(?) used for MediaWiki). + */ +$GLOBALS['csrf']['key'] = false; + +/** + * The name of the magic CSRF token that will be placed in all forms, i.e. + * the contents of <input type="hidden" name="$name" value="CSRF-TOKEN" /> + */ +$GLOBALS['csrf']['input-name'] = '__csrf_magic'; + +/** + * Set this to false if your site must work inside of frame/iframe elements, + * but do so at your own risk: this configuration protects you against CSS + * overlay attacks that defeat tokens. + */ +$GLOBALS['csrf']['frame-breaker'] = true; + +/** + * Whether or not CSRF Magic should be allowed to start a new session in order + * to determine the key. + */ +$GLOBALS['csrf']['auto-session'] = true; + +/** + * Whether or not csrf-magic should produce XHTML style tags. + */ +$GLOBALS['csrf']['xhtml'] = true; + +// FUNCTIONS: + +// Don't edit this! +$GLOBALS['csrf']['version'] = '1.0.4'; + +/** + * Rewrites <form> on the fly to add CSRF tokens to them. This can also + * inject our JavaScript library. + */ +function csrf_ob_handler($buffer, $flags) { + // Even though the user told us to rewrite, we should do a quick heuristic + // to check if the page is *actually* HTML. We don't begin rewriting until + // we hit the first <html tag. + static $is_html = false; + if (!$is_html) { + // not HTML until proven otherwise + if (stripos($buffer, '<html') !== false) { + $is_html = true; + } else { + return $buffer; + } + } + $tokens = csrf_get_tokens(); + $name = $GLOBALS['csrf']['input-name']; + $endslash = $GLOBALS['csrf']['xhtml'] ? ' /' : ''; + $input = "<input type='hidden' name='$name' value=\"$tokens\"$endslash>"; + $buffer = preg_replace('#(<form[^>]*method\s*=\s*["\']post["\'][^>]*>)#i', '$1' . $input, $buffer); + if ($GLOBALS['csrf']['frame-breaker']) { + $buffer = str_ireplace('</head>', '<script type="text/javascript">if (top != self) {top.location.href = self.location.href;}</script></head>', $buffer); + } + if ($js = $GLOBALS['csrf']['rewrite-js']) { + $buffer = str_ireplace( + '</head>', + '<script type="text/javascript">'. + 'var csrfMagicToken = "'.$tokens.'";'. + 'var csrfMagicName = "'.$name.'";</script>'. + '<script src="'.$js.'" type="text/javascript"></script></head>', + $buffer + ); + $script = '<script type="text/javascript">CsrfMagic.end();</script>'; + $buffer = str_ireplace('</body>', $script . '</body>', $buffer, $count); + if (!$count) { + $buffer .= $script; + } + } + return $buffer; +} + +/** + * Checks if this is a post request, and if it is, checks if the nonce is valid. + * @param bool $fatal Whether or not to fatally error out if there is a problem. + * @return True if check passes or is not necessary, false if failure. + */ +function csrf_check($fatal = true) { + if ($_SERVER['REQUEST_METHOD'] !== 'POST') return true; + csrf_start(); + $name = $GLOBALS['csrf']['input-name']; + $ok = false; + $tokens = ''; + do { + if (!isset($_POST[$name])) break; + // we don't regenerate a token and check it because some token creation + // schemes are volatile. + $tokens = $_POST[$name]; + if (!csrf_check_tokens($tokens)) break; + $ok = true; + } while (false); + if ($fatal && !$ok) { + $callback = $GLOBALS['csrf']['callback']; + if (trim($tokens, 'A..Za..z0..9:;,') !== '') $tokens = 'hidden'; + $callback($tokens); + exit; + } + return $ok; +} + +/** + * Retrieves a valid token(s) for a particular context. Tokens are separated + * by semicolons. + */ +function csrf_get_tokens() { + $has_cookies = !empty($_COOKIE); + + // $ip implements a composite key, which is sent if the user hasn't sent + // any cookies. It may or may not be used, depending on whether or not + // the cookies "stick" + $secret = csrf_get_secret(); + if (!$has_cookies && $secret) { + // :TODO: Harden this against proxy-spoofing attacks + $ip = ';ip:' . csrf_hash($_SERVER['IP_ADDRESS']); + } else { + $ip = ''; + } + csrf_start(); + + // These are "strong" algorithms that don't require per se a secret + if (session_id()) return 'sid:' . csrf_hash(session_id()) . $ip; + if ($GLOBALS['csrf']['cookie']) { + $val = csrf_generate_secret(); + setcookie($GLOBALS['csrf']['cookie'], $val); + return 'cookie:' . csrf_hash($val) . $ip; + } + if ($GLOBALS['csrf']['key']) return 'key:' . csrf_hash($GLOBALS['csrf']['key']) . $ip; + // These further algorithms require a server-side secret + if (!$secret) return 'invalid'; + if ($GLOBALS['csrf']['user'] !== false) { + return 'user:' . csrf_hash($GLOBALS['csrf']['user']); + } + if ($GLOBALS['csrf']['allow-ip']) { + return ltrim($ip, ';'); + } + return 'invalid'; +} + +function csrf_flattenpost($data) { + $ret = array(); + foreach($data as $n => $v) { + $ret = array_merge($ret, csrf_flattenpost2(1, $n, $v)); + } + return $ret; +} +function csrf_flattenpost2($level, $key, $data) { + if(!is_array($data)) return array($key => $data); + $ret = array(); + foreach($data as $n => $v) { + $nk = $level >= 1 ? $key."[$n]" : "[$n]"; + $ret = array_merge($ret, csrf_flattenpost2($level+1, $nk, $v)); + } + return $ret; +} + +/** + * @param $tokens is safe for HTML consumption + */ +function csrf_callback($tokens) { + // (yes, $tokens is safe to echo without escaping) + header($_SERVER['SERVER_PROTOCOL'] . ' 403 Forbidden'); + $data = ''; + foreach (csrf_flattenpost($_POST) as $key => $value) { + if ($key == $GLOBALS['csrf']['input-name']) continue; + $data .= '<input type="hidden" name="'.htmlspecialchars($key).'" value="'.htmlspecialchars($value).'" />'; + } + echo "<html><head><title>CSRF check failed</title></head> + <body> + <p>CSRF check failed. Your form session may have expired, or you may not have + cookies enabled.</p> + <form method='post' action=''>$data<input type='submit' value='Try again' /></form> + <p>Debug: $tokens</p></body></html> +"; +} + +/** + * Checks if a composite token is valid. Outward facing code should use this + * instead of csrf_check_token() + */ +function csrf_check_tokens($tokens) { + if (is_string($tokens)) $tokens = explode(';', $tokens); + foreach ($tokens as $token) { + if (csrf_check_token($token)) return true; + } + return false; +} + +/** + * Checks if a token is valid. + */ +function csrf_check_token($token) { + if (strpos($token, ':') === false) return false; + list($type, $value) = explode(':', $token, 2); + if (strpos($value, ',') === false) return false; + list($x, $time) = explode(',', $token, 2); + if ($GLOBALS['csrf']['expires']) { + if (time() > $time + $GLOBALS['csrf']['expires']) return false; + } + switch ($type) { + case 'sid': + return $value === csrf_hash(session_id(), $time); + case 'cookie': + $n = $GLOBALS['csrf']['cookie']; + if (!$n) return false; + if (!isset($_COOKIE[$n])) return false; + return $value === csrf_hash($_COOKIE[$n], $time); + case 'key': + if (!$GLOBALS['csrf']['key']) return false; + return $value === csrf_hash($GLOBALS['csrf']['key'], $time); + // We could disable these 'weaker' checks if 'key' was set, but + // that doesn't make me feel good then about the cookie-based + // implementation. + case 'user': + if (!csrf_get_secret()) return false; + if ($GLOBALS['csrf']['user'] === false) return false; + return $value === csrf_hash($GLOBALS['csrf']['user'], $time); + case 'ip': + if (!csrf_get_secret()) return false; + // do not allow IP-based checks if the username is set, or if + // the browser sent cookies + if ($GLOBALS['csrf']['user'] !== false) return false; + if (!empty($_COOKIE)) return false; + if (!$GLOBALS['csrf']['allow-ip']) return false; + return $value === csrf_hash($_SERVER['IP_ADDRESS'], $time); + } + return false; +} + +/** + * Sets a configuration value. + */ +function csrf_conf($key, $val) { + if (!isset($GLOBALS['csrf'][$key])) { + trigger_error('No such configuration ' . $key, E_USER_WARNING); + return; + } + $GLOBALS['csrf'][$key] = $val; +} + +/** + * Starts a session if we're allowed to. + */ +function csrf_start() { + if ($GLOBALS['csrf']['auto-session'] && !session_id()) { + session_start(); + } +} + +/** + * Retrieves the secret, and generates one if necessary. + */ +function csrf_get_secret() { + if ($GLOBALS['csrf']['secret']) return $GLOBALS['csrf']['secret']; + $dir = dirname(__FILE__); + $file = $dir . '/csrf-secret.php'; + $secret = ''; + if (file_exists($file)) { + include $file; + return $secret; + } + if (is_writable($dir)) { + $secret = csrf_generate_secret(); + $fh = fopen($file, 'w'); + fwrite($fh, '<?php $secret = "'.$secret.'";' . PHP_EOL); + fclose($fh); + return $secret; + } + return ''; +} + +/** + * Generates a random string as the hash of time, microtime, and mt_rand. + */ +function csrf_generate_secret($len = 32) { + $r = ''; + for ($i = 0; $i < 32; $i++) { + $r .= chr(mt_rand(0, 255)); + } + $r .= time() . microtime(); + return sha1($r); +} + +/** + * Generates a hash/expiry double. If time isn't set it will be calculated + * from the current time. + */ +function csrf_hash($value, $time = null) { + if (!$time) $time = time(); + return sha1(csrf_get_secret() . $value . $time) . ',' . $time; +} + +// Load user configuration +if (function_exists('csrf_startup')) csrf_startup(); +// Initialize our handler +if ($GLOBALS['csrf']['rewrite']) ob_start('csrf_ob_handler'); +// Perform check +if (!$GLOBALS['csrf']['defer']) csrf_check(); |
