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| 1 | <?php |
| 2 | |
| 3 | namespace MediaWiki\Rest; |
| 4 | |
| 5 | use MediaWiki\Rest\HeaderParser\HttpDate; |
| 6 | use MediaWiki\Rest\HeaderParser\IfNoneMatch; |
| 7 | use RuntimeException; |
| 8 | use Wikimedia\Timestamp\ConvertibleTimestamp; |
| 9 | |
| 10 | class ConditionalHeaderUtil { |
| 11 | private $varnishETagHack = true; |
| 12 | private $eTag; |
| 13 | private $lastModified; |
| 14 | private $hasRepresentation; |
| 15 | |
| 16 | /** |
| 17 | * Initialize the object with information about the requested resource. |
| 18 | * |
| 19 | * @param string|null $eTag The entity-tag (including quotes), or null if |
| 20 | * it is unknown. |
| 21 | * @param string|int|null $lastModified The Last-Modified date in a format |
| 22 | * accepted by ConvertibleTimestamp, or null if it is unknown. |
| 23 | * @param bool|null $hasRepresentation Whether the server has a current |
| 24 | * representation of the target resource. This should be true if the |
| 25 | * resource exists, and false if it does not exist. It is used for |
| 26 | * wildcard validators -- the intended use case is to abort a PUT if the |
| 27 | * resource does (or does not) exist. If null is passed, we assume that |
| 28 | * the resource exists if an ETag was specified for it. |
| 29 | */ |
| 30 | public function setValidators( $eTag, $lastModified, $hasRepresentation ) { |
| 31 | $this->eTag = $eTag; |
| 32 | if ( $lastModified === null ) { |
| 33 | $this->lastModified = null; |
| 34 | } else { |
| 35 | $this->lastModified = (int)ConvertibleTimestamp::convert( TS_UNIX, $lastModified ); |
| 36 | } |
| 37 | $this->hasRepresentation = $hasRepresentation ?? ( $eTag !== null ); |
| 38 | } |
| 39 | |
| 40 | /** |
| 41 | * If the Varnish ETag hack is disabled by calling this method, |
| 42 | * strong ETag comparison will follow RFC 7232, rejecting all weak |
| 43 | * ETags for If-Match comparison. |
| 44 | * |
| 45 | * @param bool $hack |
| 46 | */ |
| 47 | public function setVarnishETagHack( $hack ) { |
| 48 | $this->varnishETagHack = $hack; |
| 49 | } |
| 50 | |
| 51 | /** |
| 52 | * Check conditional request headers in the order required by RFC 7232 section 6. |
| 53 | * |
| 54 | * @param RequestInterface $request |
| 55 | * @return int|null The status code to immediately return, or null to |
| 56 | * continue processing the request. |
| 57 | */ |
| 58 | public function checkPreconditions( RequestInterface $request ) { |
| 59 | $parser = new IfNoneMatch; |
| 60 | if ( $this->eTag !== null ) { |
| 61 | $resourceTag = $parser->parseETag( $this->eTag ); |
| 62 | if ( !$resourceTag ) { |
| 63 | throw new RuntimeException( 'Invalid ETag returned by handler: `' . |
| 64 | $parser->getLastError() . '`' ); |
| 65 | } |
| 66 | } else { |
| 67 | $resourceTag = null; |
| 68 | } |
| 69 | $getOrHead = in_array( $request->getMethod(), [ 'GET', 'HEAD' ] ); |
| 70 | if ( $request->hasHeader( 'If-Match' ) ) { |
| 71 | $im = $request->getHeader( 'If-Match' ); |
| 72 | $match = false; |
| 73 | foreach ( $parser->parseHeaderList( $im ) as $tag ) { |
| 74 | if ( $tag['whole'] === '*' && $this->hasRepresentation ) { |
| 75 | $match = true; |
| 76 | break; |
| 77 | } |
| 78 | |
| 79 | if ( $this->strongCompare( $resourceTag, $tag ) ) { |
| 80 | $match = true; |
| 81 | break; |
| 82 | } |
| 83 | } |
| 84 | if ( !$match ) { |
| 85 | return 412; |
| 86 | } |
| 87 | } elseif ( $request->hasHeader( 'If-Unmodified-Since' ) ) { |
| 88 | $requestDate = HttpDate::parse( $request->getHeader( 'If-Unmodified-Since' )[0] ); |
| 89 | if ( $requestDate !== null |
| 90 | && ( $this->lastModified === null || $this->lastModified > $requestDate ) |
| 91 | ) { |
| 92 | return 412; |
| 93 | } |
| 94 | } |
| 95 | if ( $request->hasHeader( 'If-None-Match' ) ) { |
| 96 | $inm = $request->getHeader( 'If-None-Match' ); |
| 97 | foreach ( $parser->parseHeaderList( $inm ) as $tag ) { |
| 98 | if ( $tag['whole'] === '*' && $this->hasRepresentation ) { |
| 99 | return $getOrHead ? 304 : 412; |
| 100 | } |
| 101 | if ( $this->weakCompare( $resourceTag, $tag ) ) { |
| 102 | if ( $getOrHead ) { |
| 103 | return 304; |
| 104 | } else { |
| 105 | return 412; |
| 106 | } |
| 107 | } |
| 108 | } |
| 109 | } elseif ( $getOrHead && $request->hasHeader( 'If-Modified-Since' ) ) { |
| 110 | $requestDate = HttpDate::parse( $request->getHeader( 'If-Modified-Since' )[0] ); |
| 111 | if ( $requestDate !== null && $this->lastModified !== null |
| 112 | && $this->lastModified <= $requestDate |
| 113 | ) { |
| 114 | return 304; |
| 115 | } |
| 116 | } |
| 117 | // RFC 7232 states that If-Range should be evaluated here. However, the |
| 118 | // purpose of If-Range is to cause the Range request header to be |
| 119 | // conditionally ignored, not to immediately send a response, so it |
| 120 | // doesn't fit here. RFC 7232 only requires that If-Range be checked |
| 121 | // after the other conditional header fields, a requirement that is |
| 122 | // satisfied if it is processed in Handler::execute(). |
| 123 | return null; |
| 124 | } |
| 125 | |
| 126 | /** |
| 127 | * Set Last-Modified and ETag headers in the response according to the cached |
| 128 | * values set by setValidators(), which are also used for precondition checks. |
| 129 | * |
| 130 | * If the headers are already present in the response, the existing headers |
| 131 | * take precedence. |
| 132 | * |
| 133 | * @param ResponseInterface $response |
| 134 | */ |
| 135 | public function applyResponseHeaders( ResponseInterface $response ) { |
| 136 | if ( $this->lastModified !== null && !$response->hasHeader( 'Last-Modified' ) ) { |
| 137 | $response->setHeader( 'Last-Modified', HttpDate::format( $this->lastModified ) ); |
| 138 | } |
| 139 | if ( $this->eTag !== null && !$response->hasHeader( 'ETag' ) ) { |
| 140 | $response->setHeader( 'ETag', $this->eTag ); |
| 141 | } |
| 142 | } |
| 143 | |
| 144 | /** |
| 145 | * The weak comparison function, per RFC 7232, section 2.3.2. |
| 146 | * |
| 147 | * @param array|null $resourceETag ETag generated by the handler, parsed tag info array |
| 148 | * @param array|null $headerETag ETag supplied by the client, parsed tag info array |
| 149 | * @return bool |
| 150 | */ |
| 151 | private function weakCompare( $resourceETag, $headerETag ) { |
| 152 | if ( $resourceETag === null || $headerETag === null ) { |
| 153 | return false; |
| 154 | } |
| 155 | return $resourceETag['contents'] === $headerETag['contents']; |
| 156 | } |
| 157 | |
| 158 | /** |
| 159 | * The strong comparison function |
| 160 | * |
| 161 | * A strong ETag returned by the server may have been "weakened" by Varnish when applying |
| 162 | * compression. So optionally ignore the weakness of the header. |
| 163 | * {@link https://varnish-cache.org/docs/6.0/users-guide/compression.html}. |
| 164 | * @see T238849 and T310710 |
| 165 | * |
| 166 | * @param array|null $resourceETag ETag generated by the handler, parsed tag info array |
| 167 | * @param array|null $headerETag ETag supplied by the client, parsed tag info array |
| 168 | * |
| 169 | * @return bool |
| 170 | */ |
| 171 | private function strongCompare( $resourceETag, $headerETag ) { |
| 172 | if ( $resourceETag === null || $headerETag === null ) { |
| 173 | return false; |
| 174 | } |
| 175 | |
| 176 | return !$resourceETag['weak'] |
| 177 | && ( $this->varnishETagHack || !$headerETag['weak'] ) |
| 178 | && $resourceETag['contents'] === $headerETag['contents']; |
| 179 | } |
| 180 | |
| 181 | } |