1- import { BlacklightEvent , JsInstrumentEvent } from './types' ;
2-
31/**
42 * @fileOverview Utility functions for canvas finerprinting analysis.
53 * Implemented following the Princeton study's methodology.
64 */
7-
8- import { getScriptUrl , serializeCanvasCallMap } from './utils' ;
5+ import { BlacklightEvent , JsInstrumentEvent , CanvasCallMap } from './types' ;
6+ import { getScriptUrl , serializeCanvasCallMap } from './helpers/ utils' ;
97
108const MIN_CANVAS_IMAGE_WIDTH = 16 ;
119const MIN_CANVAS_IMAGE_HEIGHT = 16 ;
1210const MIN_FONT_LIST_SIZE = 50 ;
1311const MIN_TEXT_MEASURE_COUNT = 50 ;
1412const MIN_TEXT_LENGTH = 10 ;
13+
14+ const CANVAS_READ_FUNCS = [ 'HTMLCanvasElement.toDataURL' , 'CanvasRenderingContext2D.getImageData' ] ;
15+ const CANVAS_WRITE_FUNCS = [ 'CanvasRenderingContext2D.fillText' , 'CanvasRenderingContext2D.strokeText' ] ;
16+ const CANVAS_FP_DO_NOT_CALL_LIST = [ 'CanvasRenderingContext2D.save' , 'CanvasRenderingContext2D.restore' , 'HTMLCanvasElement.addEventListener' ] ;
17+ const CANVAS_FONT = [ 'CanvasRenderingContext2D.measureText' , 'CanvasRenderingContext2D.font' ] ;
18+
1519/**
1620 * Return the string that is written onto canvas from function arguments
17- * @param arguments
21+ * @param args
1822 */
1923const getCanvasText = ( args : string [ ] ) => {
2024 if ( ! args || ! args [ 0 ] ) {
@@ -31,40 +35,34 @@ const getTextLength = (text: string) => {
3135/**
3236 * Check if the retrieved pixel data is larger than min. dimensions.
3337 * {@link https://developer.mozilla.org/en-US/docsz1/Web/API/CanvasRenderingContext2D/getImageData#Parameters | Web API Image Data Parameters}
34- * @param arguments
38+ * @param args
3539 */
36- const isGetImageDataDimsTooSmall = ( args : string [ ] ) => {
37- const sw = parseInt ( args [ 2 ] , 10 ) ;
38- const sh = parseInt ( args [ 3 ] , 10 ) ;
39- return sw < MIN_CANVAS_IMAGE_WIDTH || sh < MIN_CANVAS_IMAGE_HEIGHT ;
40+ const isImageTooSmall = ( args : string [ ] ) => {
41+ const width = parseInt ( args [ 2 ] , 10 ) ;
42+ const height = parseInt ( args [ 3 ] , 10 ) ;
43+ return width < MIN_CANVAS_IMAGE_WIDTH || height < MIN_CANVAS_IMAGE_HEIGHT ;
4044} ;
41- type ScriptUrl = string ;
42- type CanvasCallValue = string ;
43- type CanvasCallMap = Map < ScriptUrl , Set < CanvasCallValue > > ;
45+
4446/**
45- * This function takes a list of Javascript calls to HTML Canvas properties from a browsers window object.
47+ * This function takes a list of Javascript calls to HTML Canvas properties from a browser's window object.
4648 * It sorts the functions in order to evaluate which script are fingerprinting a browser using the criteria
4749 * described by Englehardt & Narayanan, 2016
4850 * We Filter for 4 Criteria
49- * Criteria 1: The canvas element’s height and width properties must not be set below 16
50- * Criteria 2: Text must be written to canvas with least two colors or at least 10 distinct charachters
51- * Criteria 3: The script should not call the save, restore, or addEventListener methods of the rendering context.
52- * Criteria 4: The script extracts an image withtoDataURL or with a single call togetImageData that specifies an area with a minimum size of 16px×16px
51+ * Criteria 1: The canvas element’s height and width properties must not be set below 16px
52+ * Criteria 2: Text must be written to canvas with least two colors or at least 10 distinct characters
53+ * Criteria 3: The script should not call the save, restore, or addEventListener methods of the rendering context.
54+ * Criteria 4: The script extracts an image with toDataURL or with a single call to getImageData that specifies an area with a minimum size of 16px×16px
5355 * @param canvasCalls
5456 * @see {@link http://randomwalker.info/publications/OpenWPM_1_million_site_tracking_measurement.pdf#page=12 }
5557 */
5658export const sortCanvasCalls = ( canvasCalls : BlacklightEvent [ ] ) => {
57- const CANVAS_READ_FUNCS = [ 'HTMLCanvasElement.toDataURL' , 'CanvasRenderingContext2D.getImageData' ] ;
58-
59- const CANVAS_WRITE_FUNCS = [ 'CanvasRenderingContext2D.fillText' , 'CanvasRenderingContext2D.strokeText' ] ;
60- const CANVAS_FP_DO_NOT_CALL_LIST = [ 'CanvasRenderingContext2D.save' , 'CanvasRenderingContext2D.restore' , 'HTMLCanvasElement.addEventListener' ] ;
61-
62- const cReads = new Map ( ) as CanvasCallMap ;
59+ const cReads = new Map ( ) as CanvasCallMap ;
6360 const cDataUrls = new Map ( ) as CanvasCallMap ;
64- const cWrites = new Map ( ) as CanvasCallMap ;
65- const cTexts = new Map ( ) as CanvasCallMap ;
66- const cBanned = new Map ( ) as CanvasCallMap ;
67- const cStyles = new Map ( ) as CanvasCallMap ;
61+ const cWrites = new Map ( ) as CanvasCallMap ;
62+ const cTexts = new Map ( ) as CanvasCallMap ;
63+ const cBanned = new Map ( ) as CanvasCallMap ;
64+ const cStyles = new Map ( ) as CanvasCallMap ;
65+
6866 for ( const item of canvasCalls ) {
6967 const { url, data } = item as JsInstrumentEvent ;
7068 const url_host = new URL ( url ) . hostname ;
@@ -75,7 +73,7 @@ export const sortCanvasCalls = (canvasCalls: BlacklightEvent[]) => {
7573 }
7674
7775 if ( CANVAS_READ_FUNCS . includes ( symbol ) && operation === 'call' ) {
78- if ( symbol === 'CanvasRenderingContext2D.getImageData' && isGetImageDataDimsTooSmall ( data . arguments ) ) {
76+ if ( symbol === 'CanvasRenderingContext2D.getImageData' && isImageTooSmall ( data . arguments ) ) {
7977 continue ;
8078 }
8179 if ( symbol === 'HTMLCanvasElement.toDataURL' ) {
@@ -111,37 +109,31 @@ export const sortCanvasCalls = (canvasCalls: BlacklightEvent[]) => {
111109 * @see {@link sortCanvasCalls }
112110 * @param canvasCalls
113111 */
114- export const getCanvasFp = (
112+ export const getCanvasFingerprinters = (
115113 canvasCalls
116114) : {
117115 fingerprinters : string [ ] ;
118116 texts : any ;
119117 styles : any ;
120118 data_url : any ;
121119} => {
120+ const fingerprinters : Set < string > = new Set ( ) ;
122121 const { cDataUrls, cReads, cWrites, cBanned, cTexts, cStyles } = sortCanvasCalls ( canvasCalls ) ;
123122
124- const fingerprinters : Set < string > = new Set ( ) ;
125123 for ( const [ script_url , url_hosts ] of cReads . entries ( ) ) {
126- if ( fingerprinters . has ( script_url ) ) {
127- continue ;
128- }
124+ if ( fingerprinters . has ( script_url ) ) continue ;
129125
130126 const rwIntersection = new Set ( [ ...url_hosts ] . filter ( x => cWrites . has ( script_url ) && cWrites . get ( script_url ) . has ( x ) ) ) ;
131-
132- if ( rwIntersection . size < 1 ) {
133- continue ;
134- }
127+ if ( rwIntersection . size < 1 ) continue ;
128+
135129 for ( const canvasRwVisit of rwIntersection . values ( ) ) {
136130 if ( cBanned . has ( script_url ) && cBanned . get ( script_url ) . has ( canvasRwVisit ) ) {
137- // console.log(
138- // `Ignoring script ${script_url} from url_host ${canvasRwVisit}`
139- // );
140131 continue ;
141132 }
142133 fingerprinters . add ( script_url ) ;
143134 }
144135 }
136+
145137 return {
146138 data_url : serializeCanvasCallMap ( cDataUrls ) ,
147139 fingerprinters : Array . from ( fingerprinters ) ,
@@ -150,12 +142,12 @@ export const getCanvasFp = (
150142 } ;
151143} ;
152144
153- export const getCanvasFontFp = jsCalls => {
154- const CANVAS_FONT = [ 'CanvasRenderingContext2D.measureText' , 'CanvasRenderingContext2D.font' ] ;
145+ export const getCanvasFontFingerprinters = jsCalls => {
155146 const font_shorthand =
156147 / ^ \s * (? = (?: (?: [ - a - z ] + \s * ) { 0 , 2 } ( i t a l i c | o b l i q u e ) ) ? ) (? = (?: (?: [ - a - z ] + \s * ) { 0 , 2 } ( s m a l l - c a p s ) ) ? ) (? = (?: (?: [ - a - z ] + \s * ) { 0 , 2 } ( b o l d (?: e r ) ? | l i g h t e r | [ 1 - 9 ] 0 0 ) ) ? ) (?: (?: n o r m a l | \1| \2| \3) \s * ) { 0 , 3 } ( (?: x x ? - ) ? (?: s m a l l | l a r g e ) | m e d i u m | s m a l l e r | l a r g e r | [ . \d ] + (?: \% | i n | [ c e m ] m | e x | p [ c t x ] ) ) (?: \s * \/ \s * ( n o r m a l | [ . \d ] + (?: \% | i n | [ c e m ] m | e x | p [ c t x ] ) ) ) ? \s * ( [ - _ \{ \} \( \) \& ! \' , \* \. \" \s a - z A - Z 0 - 9 ] + ?) \s * $ / g;
157148 const textMeasure = new Map ( ) as Map < string , any > ;
158149 const canvasFont = new Map ( ) as CanvasCallMap ;
150+
159151 for ( const item of jsCalls ) {
160152 const script_url = getScriptUrl ( item ) ;
161153 const { symbol, value } = item . data ;
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