From b36320c643f5b09cad2ed574c4c456aabc9cb8dd Mon Sep 17 00:00:00 2001 From: Raymond Hill Date: Fri, 29 Dec 2017 20:26:03 -0500 Subject: [PATCH] code review: improve scriptlet inject code in stream data listener --- src/js/traffic.js | 80 ++++++++++++++++++++++++++++++----------------- 1 file changed, 52 insertions(+), 28 deletions(-) diff --git a/src/js/traffic.js b/src/js/traffic.js index 21cfc9c2d..b894b8d26 100644 --- a/src/js/traffic.js +++ b/src/js/traffic.js @@ -576,10 +576,23 @@ var reMediaContentTypes = /^(?:audio|image|video)\//; var filterDocument = (function() { var µb = µBlock, filterers = new Map(), - reDoctype = /^\s*]+?>/, domParser, xmlSerializer, textDecoderCharset, textDecoder, textEncoder; + // Purpose of following helper is to disconnect from watching the stream + // if all the following conditions are fulfilled: + // - Only need to inject scriptlets. + // - Charset of resource is utf-8. + // - A well-formed doc type declaration is found at the top. + // + // When all the conditions are fulfilled, then the scriptlets are safely + // injected after the doc type declaration, and the stream listener is + // disconnected, thus removing overhead from future streaming data. + // + // If at least one of the condition is not fulfilled and scriptlets need + // to be injected, it will be done the longer way when the whole stream + // has been collated in memory. + var streamJobDone = function(filterer, responseBytes) { if ( filterer.scriptlets === undefined || @@ -588,40 +601,51 @@ var filterDocument = (function() { ) { return false; } - if ( textDecoder === undefined ) { - textDecoder = new TextDecoder(); - } - if ( textEncoder === undefined ) { - textEncoder = new TextEncoder(); - } // We need to insert after DOCTYPE, or else the browser may falls into // quirks mode. - var firstResponseBytes = new Uint8Array(responseBytes, 0, 512), - haystack = textDecoder.decode(firstResponseBytes), - match = reDoctype.exec(haystack); - if ( match === null ) { return false; } - filterers.delete(filterer.stream); - // Output bytes may be different than response bytes: the BOM sequence - // if present is removed by the decoder. - var firstOutputBytes = textEncoder.encode( - haystack.slice(0, match.index + match[0].length) - ); - var insertAt = firstOutputBytes.byteLength; - // Mind BOM if present: - // https://en.wikipedia.org/wiki/Byte_order_mark#UTF-8 - if ( - firstResponseBytes[0] === 0xEF && - firstResponseBytes[0] === 0xBB && - firstResponseBytes[0] === 0xBF - ) { - insertAt += 3; + var bb = new Uint8Array(responseBytes, 0, 256), + i = 0, b; + // Skip BOM if present. + if ( bb[0] === 0xEF && bb[1] === 0xBB && bb[2] === 0xBF ) { i += 3; } + // Scan for '<' + for (;;) { + b = bb[i++]; + if ( b === 0x3C /* '<' */ ) { break; } + if ( b > 0x20 || b > 0x7F || i > 240 ) { return false; } } - filterer.stream.write(firstOutputBytes); + // Test for '!DOCTYPE' + if ( + bb[i++] !== 0x21 /* '!' */ || + bb[i++] !== 0x44 /* 'D' */ || + bb[i++] !== 0x4F /* 'O' */ || + bb[i++] !== 0x43 /* 'C' */ || + bb[i++] !== 0x54 /* 'T' */ || + bb[i++] !== 0x59 /* 'Y' */ || + bb[i++] !== 0x50 /* 'P' */ || + bb[i++] !== 0x45 /* 'E' */ + ) { + return false; + } + // Scan for '>'. + var qcount = 0; + for (;;) { + b = bb[i++]; + if ( b === 0x3E /* '>' */ ) { break; } + if ( b === 0x22 /* '"' */ || b === 0x27 /* "'" */ ) { qcount += 1; } + if ( b > 127 || i > 240 ) { return false; } + } + // Bail out if mismatched quotes. + if ( (qcount & 1) !== 0 ) { return false; } + // We found a valid insertion point. + if ( textEncoder === undefined ) { textEncoder = new TextEncoder(); } + filterer.stream.write( + new Uint8Array(responseBytes, 0, i) + ); filterer.stream.write( textEncoder.encode('') ); filterer.stream.write( - new Uint8Array(responseBytes, insertAt) + new Uint8Array(responseBytes, i) ); filterer.stream.disconnect(); return true;