├── .travis.yml ├── CONTRIBUTING.md ├── LICENSE ├── Makefile ├── README.md ├── classes └── class-exoskeleton.php └── exoskeleton.php /.travis.yml: -------------------------------------------------------------------------------- 1 | language: php 2 | 3 | php: 4 | - 7.1 5 | - 7.2 6 | - nightly 7 | 8 | script: 9 | - make test 10 | -------------------------------------------------------------------------------- /CONTRIBUTING.md: -------------------------------------------------------------------------------- 1 | # Contributing 2 | 3 | Welcome! Thanks for contributing to Exoskeleton. 4 | 5 | ## Coding Standards 6 | 7 | Exoskeleton adheres to the WordPress VIP coding standards. All pull requests are 8 | automatically tested with PHP Codesniffer. To make testing easy, we've provided 9 | phpcs and phpcbf make targets. The first will test the repo against the 10 | WordPress-VIP PHP Codesniifer rules and the second will automatically fix many 11 | coding standards issues. You can also add phpcbf integrations to many text 12 | editors to automatically fix issues as you write. 13 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 2, June 1991 3 | 4 | Copyright (C) 1989, 1991 Free Software Foundation, Inc., 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | Preamble 10 | 11 | The licenses for most software are designed to take away your 12 | freedom to share and change it. By contrast, the GNU General Public 13 | License is intended to guarantee your freedom to share and change free 14 | software--to make sure the software is free for all its users. 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In such case, this License incorporates 235 | the limitation as if written in the body of this License. 236 | 237 | 9. The Free Software Foundation may publish revised and/or new versions 238 | of the General Public License from time to time. Such new versions will 239 | be similar in spirit to the present version, but may differ in detail to 240 | address new problems or concerns. 241 | 242 | Each version is given a distinguishing version number. If the Program 243 | specifies a version number of this License which applies to it and "any 244 | later version", you have the option of following the terms and conditions 245 | either of that version or of any later version published by the Free 246 | Software Foundation. If the Program does not specify a version number of 247 | this License, you may choose any version ever published by the Free Software 248 | Foundation. 249 | 250 | 10. If you wish to incorporate parts of the Program into other free 251 | programs whose distribution conditions are different, write to the author 252 | to ask for permission. For software which is copyrighted by the Free 253 | Software Foundation, write to the Free Software Foundation; we sometimes 254 | make exceptions for this. Our decision will be guided by the two goals 255 | of preserving the free status of all derivatives of our free software and 256 | of promoting the sharing and reuse of software generally. 257 | 258 | NO WARRANTY 259 | 260 | 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY 261 | FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN 262 | OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES 263 | PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED 264 | OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 265 | MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 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IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 271 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR 272 | REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, 273 | INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING 274 | OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED 275 | TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY 276 | YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER 277 | PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE 278 | POSSIBILITY OF SUCH DAMAGES. 279 | 280 | END OF TERMS AND CONDITIONS 281 | -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | .PHONY: init lint phpcs phpcbf clean 2 | 3 | test: lint phpcs 4 | 5 | init: 6 | test -d /tmp/phpcs || git clone -b master --depth 1 https://github.com/squizlabs/PHP_CodeSniffer.git /tmp/phpcs 7 | test -d /tmp/wpcs || git clone -b master --depth 1 https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards.git /tmp/wpcs 8 | /tmp/phpcs/bin/phpcs --config-set installed_paths /tmp/wpcs 9 | 10 | lint: 11 | find . -name '*.php' -type f -print0 | xargs -0 -n 1 php -nl 12 | 13 | phpcs: init 14 | /tmp/phpcs/bin/phpcs -p . --standard=WordPress-VIP --extensions=php --runtime-set ignore_warnings_on_exit true 15 | 16 | phpcbf: init 17 | /tmp/phpcs/bin/phpcbf -p . --standard=WordPress-VIP --extensions=php 18 | 19 | clean: 20 | rm -rf /tmp/phpcs /tmp/wpcs 21 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Exoskeleton [![Build Status](https://travis-ci.org/Automattic/exoskeleton.svg?branch=master)](https://travis-ci.org/Automattic/exoskeleton) 2 | Exoskeleton provides self-contained, basic, configurable rate limiting for the WordPress REST API. It works with both default and custom endpoints. 3 | 4 | **NOTE: This is experimental code. It works in initial testing, but please know that it has yet to be tested in a production setting.** 5 | 6 | ## What does it do? 7 | Exoskeleton counts each access to REST API endpoints you specify. If the number of accesses exceeds a configured limit in a configured time window, Exoskeleton switches off the endpoint by not dispatching the route and ends execution after issuing a `429` (too many requests) response header along with a configured `Retry-After` header. 8 | 9 | Exoskeleton is not a replacement for infrastructural rate-limiting or other security measures. Rather, it is designed to politely enforce usage limits on REST API endpoints that might be particularly expensive, and promote good client behavior. That said, it may, if properly used, prevent over-use of expensive REST API endpoints, resulting in better site performance and stability. 10 | 11 | Exoskeleton employs the transient API to meter endpoints -- it will therefore use an object cache if one is available. It is recommended that you use Exoskeleton with an object cache backend such as memcache -- doing so will ensure that the plugin generates no database activity. If your site stores transients in the database, a lightweight mysql `UPDATE` query will be executed each time a metered endpoint is accessed (unless it is currently locked.) This is still likely to be many times less expensive than whatever endpoint you're protecting, but you have been warned :-) 12 | 13 | ## Configuration 14 | 15 | Metering is configured using the following array of arguments: 16 | 17 | ```php 18 | array( 19 | 'route' => '/my-namespace/v1/route/(?P[\d]+)', // the fully namespaced route to be filtered 20 | 'window' => 10, // the time window in seconds 21 | 'limit' => 5, // the maximum number of requests allowed in the time window 22 | 'lockout' => 20, // the lockout time in seconds 23 | 'method' => 'POST', // the methods (endpoints) to meter. 'any' may be used to meter all methods for a route 24 | ) 25 | ``` 26 | 27 | ### metering built-in endpoints 28 | 29 | To meter a built-in REST API endpoint, use the provided utility function `exoskeleton_add_rule`. 30 | Example: 31 | 32 | ```php 33 | 34 | exoskeleton_add_rule( 35 | [ 36 | 'route' => '/wp/v2/posts', 37 | 'window' => 10, 38 | 'limit' => 7, 39 | 'lockout' => 20, 40 | 'method' => 'any', 41 | ] 42 | ); 43 | ``` 44 | causes the route `/wp/v2/posts` to be metered for _any_ endpoint (see below for details on the method parameter.) In the example, if more than 7 requests are detected in a 10 second period, a lockout of 20 seconds will occur, during which the 429 responses will be issued and the endpoint will not be dispatched. 45 | 46 | To set multiple endpoints, use `exoskeleton_add_rules` and pass an array of arrays like the above. 47 | 48 | ### metering custom endpoints 49 | 50 | You can configure metering for custom endpoints during their definition, ie: when calling `register_rest_route`. Just pass in a configuration array (minus the route and method which are already provided) as `exoskeleton`. Example: 51 | 52 | ```php 53 | add_action( 'rest_api_init', function () { 54 | register_rest_route( 'myplugin/v1', '/author/(?P\d+)', array( 55 | 'methods' => 'GET', 56 | 'callback' => 'my_awesome_func', 57 | 'exoskeleton' => [ 'window' => 10, 'limit' => 5, 'lockout' => 20 ], 58 | ) ); 59 | } ); 60 | ``` 61 | 62 | ### methods 63 | 64 | To specify which endpoints of a built-in route should be metered, use the `method` parameter. Passing `any` here will cause the method to meter all requests regardless of method under a single counter -- ie: `limit` requests for any method at all within the time window will cause a lockout. 65 | 66 | `method` can also be a comma-separated list of methods, eg: `POST,GET,PUT`, in which case (as for `any`) all listed methods will be counted together. To limit each endpoint of a built-in route separately, define a rule for each method rather than using a comma-separated list in a single rule. 67 | 68 | The boolean parameter `treat_head_like_get` may also be passed in a rule defintion. If false, it causes `GET` and `HEAD` to be counted metered separately. Otherwise, the limiter considers `HEAD`requests as if they were `GET`. This is only really useful during testing, when `HEAD` requests are sometimes handy. 69 | 70 | When filtering custom endpoints, the `method` parameter is not needed, since one or more methods are already specified. However, `treat_head_like_get` may still be passed and is respected for custom endpoints 71 | -------------------------------------------------------------------------------- /classes/class-exoskeleton.php: -------------------------------------------------------------------------------- 1 | 'any', 49 | 'treat_head_like_get' => true, 50 | ]; 51 | $args = array_merge( $defaults, $args ); 52 | 53 | if ( ! $this->validate_rule( $args ) ) { 54 | return false; 55 | } 56 | $key = $this->generate_rule_key( $args ); 57 | $any_key = $this->anyize_rule_key( $key ); 58 | if ( ! isset( $this->rules[ $key ] ) && ! isset( $this->rules[ $any_key ] ) ) { 59 | $this->rules[ $key ] = $args; 60 | return true; 61 | } else { 62 | return false; 63 | } 64 | } 65 | 66 | /** 67 | * Makes a key for the rule based on its method and argyments 68 | * @param Array $rule 69 | * @return String the generated key 70 | */ 71 | private function generate_rule_key( $rule ) { 72 | $method = $rule['method']; 73 | unset( $rule['method'] ); 74 | return md5( serialize( $rule ) ) . '_' . $method; 75 | } 76 | 77 | /** 78 | * Turn a _method key into an _any key 79 | * @param String $key 80 | * @return String the key with a _any suffix 81 | */ 82 | private function anyize_rule_key( $key ) { 83 | $parts = explode( '_', $key ); 84 | return $parts[0] . '_any'; 85 | } 86 | 87 | /** 88 | * Make sure a rule is valid. Valid rules are those with a valid method or "any", a positive numeric argument for lockout, window and limit and a boolean argument for treat_head_like_get. We don't validate routes. 89 | * @param Array $args 90 | * @return Bool whether the rule is valid 91 | */ 92 | public function validate_rule( $args ) { 93 | 94 | //every rule must have 95 | $required = [ 'route', 'method', 'window', 'limit', 'lockout', 'treat_head_like_get' ]; 96 | 97 | //gets a list of the supported rules and tacks on 'HEAD' and the psedo-method 'any' 98 | if ( class_exists( 'WP_REST_Server' ) ) { 99 | $available_methods = WP_REST_Server::ALLMETHODS; 100 | if ( false === strpos( $available_methods, 'HEAD' ) ) { 101 | $available_methods .= ', HEAD'; 102 | } 103 | $available_methods .= ', any'; 104 | } else { 105 | $available_methods = 'GET, POST, PUT, PATCH, DELETE, HEAD, any'; 106 | } 107 | 108 | $valid = true; //innocent until proven guilty 109 | 110 | foreach ( $required as $key ) { 111 | 112 | if ( ! isset( $args[ $key ] ) ) { 113 | $valid = false; 114 | } else { 115 | switch ( $key ) { 116 | case 'method': 117 | $valid = ( false !== strpos( $available_methods, $args[ $key ] ) ); 118 | break; 119 | case 'lockout': 120 | case 'window': 121 | case 'limit': 122 | $valid = ( is_numeric( $args[ $key ] ) && $args[ $key ] > 0 ); 123 | break; 124 | case 'treat_head_like_get': 125 | $valid = is_bool( $args[ $key ] ); 126 | break; 127 | case 'route': //don't validate routes 128 | default: 129 | $valid = true; 130 | break; 131 | } 132 | } 133 | if ( ! (bool) $valid ) { 134 | return (bool) $valid; 135 | } 136 | } 137 | 138 | return (bool) $valid; 139 | } 140 | 141 | /** 142 | * Custom (non-built-in) routes receive their rules when they are defined. This callback sniffs out rules from all the server's endpoints and adds them. 143 | * @param WP_REST_Server $server 144 | * @return null 145 | */ 146 | public function process_custom_routes( $server ) { 147 | foreach ( $server->get_routes() as $path => $endpoints ) { 148 | foreach ( $endpoints as $endpoint ) { 149 | if ( isset( $endpoint['exoskeleton'] ) ) { 150 | $rule = $endpoint['exoskeleton']; 151 | //set rule methds -- turn multiple methods into a list 152 | if ( is_array( $endpoint['methods'] ) ) { 153 | $rule['method'] = implode( ',', array_keys( $endpoint['methods'] ) ); 154 | } else { 155 | $rule['method'] = 'any'; 156 | } 157 | //set rule path 158 | $rule['route'] = $path; 159 | 160 | $this->add_rule( $rule ); 161 | } 162 | } 163 | } 164 | } 165 | 166 | /** 167 | * Decide whether a given WP_REST_Request is subject to an Exoskeleton Rule. If so, it invoke the limiter. 168 | * @param WP_REST_Response $response 169 | * @param WP_REST_Server $handler 170 | * @param WP_REST_Request $request 171 | * @return WP_REST_Response | null 172 | */ 173 | public function shields_up( $response, $handler, $request ) { 174 | 175 | // if there's already a nonempty response, someone else got here first, so bail 176 | if ( ! empty( $response ) ) { 177 | return $response; 178 | } 179 | 180 | $path = $request->get_route(); 181 | $method = $request->get_method(); 182 | $matched_rule = []; 183 | 184 | foreach ( $this->rules as $key => $rule ) { 185 | $match = preg_match( '@^' . $rule['route'] . '$@i', $path, $match_result ); 186 | if ( 1 === $match ) { 187 | if ( $this->match_rule_method( $method, $rule ) ) { 188 | $matched_rule = [ 189 | $key => $rule, 190 | ]; 191 | $this->maybe_back_off( $matched_rule ); 192 | } 193 | } 194 | } 195 | return $response; 196 | } 197 | 198 | /** 199 | * For a given rule, does the method match? 200 | * @param String $method 201 | * @param Array $rule 202 | * @return Bool whether or not the method applies to the rule 203 | */ 204 | private function match_rule_method( $method, $rule ) { 205 | 206 | //by default we meter HEAD requests as though they were GETs rules may override this for particular routes 207 | if ( 'HEAD' === $method && $rule['treat_head_like_get'] ) { 208 | $method = 'GET'; 209 | } 210 | 211 | return ( 212 | 'any' === $rule['method'] || 213 | $rule['method'] === $method || 214 | in_array( $method, explode( ',', $rule['method'] ) ) 215 | ); 216 | } 217 | 218 | /** 219 | * Decide whether to tell the request to back off based on the current state of the applicable rule's lock. Also, increment the rule's counter, and set a lock if needed. 220 | * @param Array $matched_rule 221 | * @return null 222 | */ 223 | private function maybe_back_off( $matched_rule ) { 224 | 225 | $rule_id = array_keys( $matched_rule )[0]; 226 | $lock = $this->get_lock( $rule_id ); 227 | 228 | if ( $lock ) { 229 | $this->back_off_please( $rule_id, $matched_rule, $lock ); 230 | } 231 | 232 | // since there's no lock we'll allow the request to continue, but first increment the counter 233 | $counter = $this->increment_counter( $rule_id, $matched_rule ); 234 | 235 | //now see if we need to lock things down for next time 236 | if ( $counter >= $matched_rule[ $rule_id ]['limit'] ) { 237 | $this->set_lock( $rule_id, $matched_rule ); 238 | } 239 | } 240 | 241 | /** 242 | * Check for a lock on a given rule or it's universal version 243 | * @param String $rule_id 244 | * @return Array | Bool the lock, or false if no lock is found 245 | */ 246 | private function get_lock( $rule_id ) { 247 | $lock = self::LOCK_PREFIX . $rule_id; 248 | //we might need to check for universal locks and not just the method requested 249 | $any_lock = self::LOCK_PREFIX . $this->anyize_rule_key( $rule_id ); 250 | 251 | $found_lock = get_transient( $lock ); 252 | // looking for the any method lock in the first place? then we're done 253 | if ( $lock === $any_lock ) { 254 | return $found_lock; 255 | } 256 | 257 | //if nothing could be found for the original lock, check the _any version of the lock instead 258 | if ( false === $found_lock ) { 259 | return get_transient( $any_lock ); 260 | } 261 | return $found_lock; 262 | } 263 | 264 | /** 265 | * Sets a lock (transient) lasting lockout seconds for a matched rule_id 266 | * @param String $rule_id 267 | * @param Array $matched_rule 268 | * @return Bool whether or not the lock was successfully set 269 | */ 270 | private function set_lock( $rule_id, $matched_rule ) { 271 | $lock = self::LOCK_PREFIX . $rule_id; 272 | $lock_data = [ 273 | 'lockout' => $matched_rule[ $rule_id ]['lockout'], 274 | 'lock_set' => time(), 275 | ]; 276 | return set_transient( $lock, $lock_data, $matched_rule[ $rule_id ]['lockout'] ); 277 | } 278 | 279 | /** 280 | * Terminate the request after sending a 429 and Retry-After header 281 | * @param String $rule_id 282 | * @param Array $matched_rule 283 | * @param Array $lock 284 | * @return null 285 | */ 286 | private function back_off_please( $rule_id, $matched_rule, $lock ) { 287 | 288 | $lockout = $matched_rule[ $rule_id ]['lockout']; 289 | $retry_after = ( isset( $lock['lock_set'] ) ) ? max( $lockout - ( time() - $lock['lock_set'] ), 1 ) : $lockout; 290 | status_header( 429, 'Exoskeleton: too many requests for this endpoint. Please consult Retry-After and come back later. Meanwhile enjoy a well-deserved REST' ); 291 | @header( "Retry-After: $retry_after" ); 292 | @header( "Cache-Control: public max-age=$retry_after" ); 293 | status_header( 429, 'Exoskeleton: too many requests for this endpoint. Please consult Retry-After and come back later. Meanwhile enjoy a well-deserved REST' ); 294 | @header( "Retry-After: $retry_after" ); 295 | die(); 296 | } 297 | 298 | /** 299 | * Increment the counter for requests on the matched endpoint. 300 | * @param String $rule_id 301 | * @param Array $matched_rule 302 | * @return Int the value of the counter after increment 303 | */ 304 | private function increment_counter( $rule_id, $matched_rule ) { 305 | 306 | $counter_id = self::COUNTER_PREFIX . $rule_id; 307 | $counter = get_transient( $counter_id ); 308 | 309 | $new_counter = []; 310 | $new_counter['started_counting_at'] = ( false === $counter ) ? time() : $counter['started_counting_at']; 311 | $new_counter['value'] = ( false === $counter ) ? 1 : $counter['value'] + 1; 312 | 313 | // the transient life. This is either the rule window (for a new counter) or the window minus the number of seconds we've already been waiting. Make sure we set the transient to last at least 1 second here. 314 | $time_left = ( false === $counter ) ? $matched_rule[ $rule_id ]['window'] : max( 1, $matched_rule[ $rule_id ]['window'] - ( time() - $counter['started_counting_at'] ) ); 315 | 316 | set_transient( $counter_id, $new_counter, $time_left ); 317 | return $new_counter['value']; 318 | } 319 | } 320 | -------------------------------------------------------------------------------- /exoskeleton.php: -------------------------------------------------------------------------------- 1 | add_rule( $args ); 21 | } 22 | 23 | /** 24 | * Add many rules at once 25 | * @param Array $rules an array of rules arrays 26 | * @return null 27 | */ 28 | function exoskeleton_add_rules( $rules ) { 29 | foreach ( $rules as $rule ) { 30 | exoskeleton_add_rule( $rule ); 31 | } 32 | } 33 | 34 | Exoskeleton::get_instance(); 35 | --------------------------------------------------------------------------------