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| 1 | <?php |
| 2 | |
| 3 | /** |
| 4 | * A version of the abuse filter parser that separates parsing the filter and |
| 5 | * evaluating it into different passes, allowing the parse tree to be cached. |
| 6 | * |
| 7 | * @file |
| 8 | * @phan-file-suppress PhanPossiblyInfiniteRecursionSameParams Recursion controlled by class props |
| 9 | */ |
| 10 | |
| 11 | namespace MediaWiki\Extension\AbuseFilter\Parser; |
| 12 | |
| 13 | use MediaWiki\Extension\AbuseFilter\KeywordsManager; |
| 14 | use MediaWiki\Extension\AbuseFilter\Parser\Exception\UserVisibleException; |
| 15 | use Psr\Log\LoggerInterface; |
| 16 | use Wikimedia\Stats\IBufferingStatsdDataFactory; |
| 17 | |
| 18 | /** |
| 19 | * A parser that transforms the text of the filter into a parse tree. |
| 20 | */ |
| 21 | class AFPTreeParser { |
| 22 | /** |
| 23 | * @var array<int,array{0:AFPToken,1:int}> Contains the AFPTokens for the code being parsed |
| 24 | */ |
| 25 | private $mTokens; |
| 26 | /** |
| 27 | * @var AFPToken The current token |
| 28 | */ |
| 29 | private $mCur; |
| 30 | /** @var int The position of the current token */ |
| 31 | private $mPos; |
| 32 | |
| 33 | /** |
| 34 | * @var string|null The ID of the filter being parsed, if available. Can also be "global-$ID" |
| 35 | */ |
| 36 | private $mFilter; |
| 37 | |
| 38 | public const CACHE_VERSION = 2; |
| 39 | |
| 40 | public function __construct( |
| 41 | private readonly LoggerInterface $logger, |
| 42 | private readonly IBufferingStatsdDataFactory $statsd, |
| 43 | private readonly KeywordsManager $keywordsManager |
| 44 | ) { |
| 45 | $this->resetState(); |
| 46 | } |
| 47 | |
| 48 | /** |
| 49 | * @param string $filter |
| 50 | */ |
| 51 | public function setFilter( $filter ) { |
| 52 | $this->mFilter = $filter; |
| 53 | } |
| 54 | |
| 55 | /** |
| 56 | * Resets the state |
| 57 | */ |
| 58 | private function resetState() { |
| 59 | $this->mTokens = []; |
| 60 | $this->mPos = 0; |
| 61 | $this->mFilter = null; |
| 62 | } |
| 63 | |
| 64 | /** |
| 65 | * Advances the parser to the next token in the filter code. |
| 66 | */ |
| 67 | private function move() { |
| 68 | [ $this->mCur, $this->mPos ] = $this->mTokens[$this->mPos]; |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * Get the next token. This is similar to move() but doesn't change class members, |
| 73 | * allowing to look ahead without rolling back the state. |
| 74 | * |
| 75 | * @return AFPToken |
| 76 | */ |
| 77 | private function getNextToken() { |
| 78 | return $this->mTokens[$this->mPos][0]; |
| 79 | } |
| 80 | |
| 81 | /** |
| 82 | * getState() function allows parser state to be rollbacked to several tokens |
| 83 | * back. |
| 84 | * |
| 85 | * @return AFPParserState |
| 86 | */ |
| 87 | private function getState() { |
| 88 | return new AFPParserState( $this->mCur, $this->mPos ); |
| 89 | } |
| 90 | |
| 91 | /** |
| 92 | * setState() function allows parser state to be rollbacked to several tokens |
| 93 | * back. |
| 94 | */ |
| 95 | private function setState( AFPParserState $state ) { |
| 96 | $this->mCur = $state->token; |
| 97 | $this->mPos = $state->pos; |
| 98 | } |
| 99 | |
| 100 | /** |
| 101 | * Parse the supplied filter source code into a tree. |
| 102 | * |
| 103 | * @param array<int,array{0:AFPToken,1:int}> $tokens |
| 104 | * @return AFPSyntaxTree |
| 105 | * @throws UserVisibleException |
| 106 | */ |
| 107 | public function parse( array $tokens ): AFPSyntaxTree { |
| 108 | $this->mTokens = $tokens; |
| 109 | $this->mPos = 0; |
| 110 | |
| 111 | return $this->buildSyntaxTree(); |
| 112 | } |
| 113 | |
| 114 | private function buildSyntaxTree(): AFPSyntaxTree { |
| 115 | $startTime = microtime( true ); |
| 116 | $root = $this->doLevelEntry(); |
| 117 | $this->statsd->timing( 'abusefilter_cachingParser_buildtree', microtime( true ) - $startTime ); |
| 118 | return new AFPSyntaxTree( $root ); |
| 119 | } |
| 120 | |
| 121 | /* Levels */ |
| 122 | |
| 123 | /** |
| 124 | * Handles unexpected characters after the expression. |
| 125 | * @return AFPTreeNode|null Null only if no statements |
| 126 | * @throws UserVisibleException |
| 127 | */ |
| 128 | private function doLevelEntry() { |
| 129 | $result = $this->doLevelSemicolon(); |
| 130 | |
| 131 | if ( $this->mCur->type !== AFPToken::TNONE ) { |
| 132 | throw new UserVisibleException( |
| 133 | 'unexpectedatend', |
| 134 | $this->mPos, [ $this->mCur->type ] |
| 135 | ); |
| 136 | } |
| 137 | |
| 138 | return $result; |
| 139 | } |
| 140 | |
| 141 | /** |
| 142 | * Handles the semicolon operator. |
| 143 | * |
| 144 | * @return AFPTreeNode|null |
| 145 | */ |
| 146 | private function doLevelSemicolon() { |
| 147 | $statements = []; |
| 148 | |
| 149 | do { |
| 150 | $this->move(); |
| 151 | $position = $this->mPos; |
| 152 | |
| 153 | if ( |
| 154 | $this->mCur->type === AFPToken::TNONE || |
| 155 | ( $this->mCur->type === AFPToken::TBRACE && $this->mCur->value == ')' ) |
| 156 | ) { |
| 157 | // Handle special cases which the other parser handled in doLevelAtom |
| 158 | break; |
| 159 | } |
| 160 | |
| 161 | // Allow empty statements. |
| 162 | if ( $this->mCur->type === AFPToken::TSTATEMENTSEPARATOR ) { |
| 163 | continue; |
| 164 | } |
| 165 | |
| 166 | $statements[] = $this->doLevelSet(); |
| 167 | $position = $this->mPos; |
| 168 | } while ( $this->mCur->type === AFPToken::TSTATEMENTSEPARATOR ); |
| 169 | |
| 170 | // Flatten the tree if possible. |
| 171 | if ( count( $statements ) === 0 ) { |
| 172 | return null; |
| 173 | } elseif ( count( $statements ) === 1 ) { |
| 174 | return $statements[0]; |
| 175 | } else { |
| 176 | return new AFPTreeNode( AFPTreeNode::SEMICOLON, $statements, $position ); |
| 177 | } |
| 178 | } |
| 179 | |
| 180 | /** |
| 181 | * Handles variable assignment. |
| 182 | * |
| 183 | * @return AFPTreeNode |
| 184 | * @throws UserVisibleException |
| 185 | */ |
| 186 | private function doLevelSet() { |
| 187 | if ( $this->mCur->type === AFPToken::TID ) { |
| 188 | $varname = (string)$this->mCur->value; |
| 189 | |
| 190 | // Speculatively parse the assignment statement assuming it can |
| 191 | // potentially be an assignment, but roll back if it isn't. |
| 192 | // @todo Use $this->getNextToken for clearer code |
| 193 | $initialState = $this->getState(); |
| 194 | $this->move(); |
| 195 | |
| 196 | if ( $this->mCur->type === AFPToken::TOP && $this->mCur->value === ':=' ) { |
| 197 | $position = $this->mPos; |
| 198 | $this->move(); |
| 199 | $value = $this->doLevelSet(); |
| 200 | |
| 201 | return new AFPTreeNode( AFPTreeNode::ASSIGNMENT, [ $varname, $value ], $position ); |
| 202 | } |
| 203 | |
| 204 | if ( $this->mCur->type === AFPToken::TSQUAREBRACKET && $this->mCur->value === '[' ) { |
| 205 | $this->move(); |
| 206 | |
| 207 | if ( $this->mCur->type === AFPToken::TSQUAREBRACKET && $this->mCur->value === ']' ) { |
| 208 | $index = 'append'; |
| 209 | } else { |
| 210 | // Parse index offset. |
| 211 | $this->setState( $initialState ); |
| 212 | $this->move(); |
| 213 | $index = $this->doLevelSemicolon(); |
| 214 | if ( !( $this->mCur->type === AFPToken::TSQUAREBRACKET && $this->mCur->value === ']' ) ) { |
| 215 | throw new UserVisibleException( 'expectednotfound', $this->mPos, |
| 216 | [ ']', $this->mCur->type, $this->mCur->value ] ); |
| 217 | } |
| 218 | } |
| 219 | |
| 220 | $this->move(); |
| 221 | if ( $this->mCur->type === AFPToken::TOP && $this->mCur->value === ':=' ) { |
| 222 | $position = $this->mPos; |
| 223 | $this->move(); |
| 224 | $value = $this->doLevelSet(); |
| 225 | if ( $index === 'append' ) { |
| 226 | return new AFPTreeNode( |
| 227 | AFPTreeNode::ARRAY_APPEND, [ $varname, $value ], $position ); |
| 228 | } else { |
| 229 | return new AFPTreeNode( |
| 230 | AFPTreeNode::INDEX_ASSIGNMENT, |
| 231 | [ $varname, $index, $value ], |
| 232 | $position |
| 233 | ); |
| 234 | } |
| 235 | } |
| 236 | } |
| 237 | |
| 238 | // If we reached this point, we did not find an assignment. Roll back |
| 239 | // and assume this was just a literal. |
| 240 | $this->setState( $initialState ); |
| 241 | } |
| 242 | |
| 243 | return $this->doLevelConditions(); |
| 244 | } |
| 245 | |
| 246 | /** |
| 247 | * Handles ternary operator and if-then-else-end. |
| 248 | * |
| 249 | * @return AFPTreeNode |
| 250 | * @throws UserVisibleException |
| 251 | */ |
| 252 | private function doLevelConditions() { |
| 253 | if ( $this->mCur->type === AFPToken::TKEYWORD && $this->mCur->value === 'if' ) { |
| 254 | $position = $this->mPos; |
| 255 | $this->move(); |
| 256 | $condition = $this->doLevelBoolOps(); |
| 257 | |
| 258 | if ( !( $this->mCur->type === AFPToken::TKEYWORD && $this->mCur->value === 'then' ) ) { |
| 259 | throw new UserVisibleException( 'expectednotfound', |
| 260 | $this->mPos, |
| 261 | [ |
| 262 | 'then', |
| 263 | $this->mCur->type, |
| 264 | $this->mCur->value |
| 265 | ] |
| 266 | ); |
| 267 | } |
| 268 | $this->move(); |
| 269 | |
| 270 | $valueIfTrue = $this->doLevelConditions(); |
| 271 | |
| 272 | if ( $this->mCur->type === AFPToken::TKEYWORD && $this->mCur->value === 'else' ) { |
| 273 | $this->move(); |
| 274 | $valueIfFalse = $this->doLevelConditions(); |
| 275 | } else { |
| 276 | $valueIfFalse = null; |
| 277 | } |
| 278 | |
| 279 | if ( !( $this->mCur->type === AFPToken::TKEYWORD && $this->mCur->value === 'end' ) ) { |
| 280 | throw new UserVisibleException( 'expectednotfound', |
| 281 | $this->mPos, |
| 282 | [ |
| 283 | 'end', |
| 284 | $this->mCur->type, |
| 285 | $this->mCur->value |
| 286 | ] |
| 287 | ); |
| 288 | } |
| 289 | $this->move(); |
| 290 | |
| 291 | return new AFPTreeNode( |
| 292 | AFPTreeNode::CONDITIONAL, |
| 293 | [ $condition, $valueIfTrue, $valueIfFalse ], |
| 294 | $position |
| 295 | ); |
| 296 | } |
| 297 | |
| 298 | $condition = $this->doLevelBoolOps(); |
| 299 | if ( $this->mCur->type === AFPToken::TOP && $this->mCur->value === '?' ) { |
| 300 | $position = $this->mPos; |
| 301 | $this->move(); |
| 302 | |
| 303 | $valueIfTrue = $this->doLevelConditions(); |
| 304 | if ( !( $this->mCur->type === AFPToken::TOP && $this->mCur->value === ':' ) ) { |
| 305 | throw new UserVisibleException( 'expectednotfound', |
| 306 | $this->mPos, |
| 307 | [ |
| 308 | ':', |
| 309 | $this->mCur->type, |
| 310 | $this->mCur->value |
| 311 | ] |
| 312 | ); |
| 313 | } |
| 314 | $this->move(); |
| 315 | |
| 316 | $valueIfFalse = $this->doLevelConditions(); |
| 317 | return new AFPTreeNode( |
| 318 | AFPTreeNode::CONDITIONAL, |
| 319 | [ $condition, $valueIfTrue, $valueIfFalse ], |
| 320 | $position |
| 321 | ); |
| 322 | } |
| 323 | |
| 324 | return $condition; |
| 325 | } |
| 326 | |
| 327 | /** |
| 328 | * Handles logic operators. |
| 329 | * |
| 330 | * @return AFPTreeNode |
| 331 | */ |
| 332 | private function doLevelBoolOps() { |
| 333 | $leftOperand = $this->doLevelCompares(); |
| 334 | $ops = [ '&', '|', '^' ]; |
| 335 | while ( $this->mCur->type === AFPToken::TOP && in_array( $this->mCur->value, $ops ) ) { |
| 336 | $op = $this->mCur->value; |
| 337 | $position = $this->mPos; |
| 338 | $this->move(); |
| 339 | |
| 340 | $rightOperand = $this->doLevelCompares(); |
| 341 | |
| 342 | $leftOperand = new AFPTreeNode( |
| 343 | AFPTreeNode::LOGIC, |
| 344 | [ $op, $leftOperand, $rightOperand ], |
| 345 | $position |
| 346 | ); |
| 347 | } |
| 348 | return $leftOperand; |
| 349 | } |
| 350 | |
| 351 | /** |
| 352 | * Handles comparison operators. |
| 353 | * |
| 354 | * @return AFPTreeNode |
| 355 | */ |
| 356 | private function doLevelCompares() { |
| 357 | $leftOperand = $this->doLevelSumRels(); |
| 358 | $equalityOps = [ '==', '===', '!=', '!==', '=' ]; |
| 359 | $orderOps = [ '<', '>', '<=', '>=' ]; |
| 360 | // Only allow either a single operation, or a combination of a single equalityOps and a single |
| 361 | // orderOps. This resembles what PHP does, and allows `a < b == c` while rejecting `a < b < c` |
| 362 | $allowedOps = array_merge( $equalityOps, $orderOps ); |
| 363 | while ( $this->mCur->type === AFPToken::TOP && in_array( $this->mCur->value, $allowedOps ) ) { |
| 364 | $op = $this->mCur->value; |
| 365 | $allowedOps = in_array( $op, $equalityOps ) ? |
| 366 | array_diff( $allowedOps, $equalityOps ) : |
| 367 | array_diff( $allowedOps, $orderOps ); |
| 368 | $position = $this->mPos; |
| 369 | $this->move(); |
| 370 | $rightOperand = $this->doLevelSumRels(); |