Web-Environment-Integrity/docs/spec/index.html

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<!doctype html><html lang="en">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title>Web Environment Integrity</title>
<meta content="width=device-width, initial-scale=1, shrink-to-fit=no" name="viewport">
<style data-fill-with="stylesheet">/******************************************************************************
* Style sheet for the W3C specifications *
*
* Special classes handled by this style sheet include:
*
* Indices
* - .toc for the Table of Contents (<ol class="toc">)
* + <span class="secno"> for the section numbers
* - #toc for the Table of Contents (<nav id="toc">)
* - ul.index for Indices (<a href="#ref">term</a><span>, in §N.M</span>)
* - table.index for Index Tables (e.g. for properties or elements)
*
* Structural Markup
* - table.data for general data tables
* -> use 'scope' attribute, <colgroup>, <thead>, and <tbody> for best results !
* -> use <table class='complex data'> for extra-complex tables
* -> use <td class='long'> for paragraph-length cell content
* -> use <td class='pre'> when manual line breaks/indentation would help readability
* - dl.switch for switch statements
* - ol.algorithm for algorithms (helps to visualize nesting)
* - .figure and .caption (HTML4) and figure and figcaption (HTML5)
* -> .sidefigure for right-floated figures
* - ins/del
* -> ins/del.c### for candidate and proposed changes (amendments)
*
* Code
* - pre and code
*
* Special Sections
* - .note for informative notes (div, p, span, aside, details)
* - .example for informative examples (div, p, pre, span)
* - .issue for issues (div, p, span)
* - .advisement for loud normative statements (div, p, strong)
* - .annoying-warning for spec obsoletion notices (div, aside, details)
* - .correction for "candidate corrections" (div, aside, details, section)
* - .addition for "candidate additions" (div, aside, details, section)
* - .correction.proposed for "proposed corrections" (div, aside, details, section)
* - .addition.proposed for "proposed additions" (div, aside, details, section)
*
* Definition Boxes
* - pre.def for WebIDL definitions
* - table.def for tables that define other entities (e.g. CSS properties)
* - dl.def for definition lists that define other entitles (e.g. HTML elements)
*
* Numbering
* - .secno for section numbers in .toc and headings (<span class='secno'>3.2</span>)
* - .marker for source-inserted example/figure/issue numbers (<span class='marker'>Issue 4</span>)
* - ::before styled for CSS-generated issue/example/figure numbers:
* -> Documents wishing to use this only need to add
* figcaption::before,
* .caption::before { content: "Figure " counter(figure) " "; }
* .example::before { content: "Example " counter(example) " "; }
* .issue::before { content: "Issue " counter(issue) " "; }
*
* Header Stuff (ignore, just don't conflict with these classes)
* - .head for the header
* - .copyright for the copyright
*
* Outdated warning for old specs
*
* Miscellaneous
* - .overlarge for things that should be as wide as possible, even if
* that overflows the body text area. This can be used on an item or
* on its container, depending on the effect desired.
* Note that this styling basically doesn't help at all when printing,
* since A4 paper isn't much wider than the max-width here.
* It's better to design things to fit into a narrower measure if possible.
*
* - js-added ToC jump links (see fixup.js)
*
******************************************************************************/
/* color variables included separately for reliability */
/******************************************************************************/
/* Body */
/******************************************************************************/
html {
}
body {
counter-reset: example figure issue;
/* Layout */
max-width: 50em; /* limit line length to 50em for readability */
margin: 0 auto; /* center text within page */
padding: 1.6em 1.5em 2em 50px; /* assume 16px font size for downlevel clients */
padding: 1.6em 1.5em 2em calc(26px + 1.5em); /* leave space for status flag */
/* Typography */
line-height: 1.5;
font-family: sans-serif;
widows: 2;
orphans: 2;
word-wrap: break-word;
overflow-wrap: break-word;
hyphens: auto;
color: black;
color: var(--text);
background: white top left fixed no-repeat;
background: var(--bg) top left fixed no-repeat;
background-size: 25px auto;
}
/******************************************************************************/
/* Front Matter & Navigation */
/******************************************************************************/
/** Header ********************************************************************/
div.head { margin-bottom: 1em; }
div.head hr { border-style: solid; }
div.head h1 {
font-weight: bold;
margin: 0 0 .1em;
font-size: 220%;
}
div.head h2 { margin-bottom: 1.5em;}
/** W3C Logo ******************************************************************/
.head .logo {
float: right;
margin: 0.4rem 0 0.2rem .4rem;
}
.head img[src*="logos/W3C"] {
display: block;
border: solid #1a5e9a;
border: solid var(--logo-bg);
border-width: .65rem .7rem .6rem;
border-radius: .4rem;
background: #1a5e9a;
background: var(--logo-bg);
color: white;
color: var(--logo-text);
font-weight: bold;
}
.head a:hover > img[src*="logos/W3C"],
.head a:focus > img[src*="logos/W3C"] {
opacity: .8;
}
.head a:active > img[src*="logos/W3C"] {
background: #c00;
background: var(--logo-active-bg);
border-color: #c00;
border-color: var(--logo-active-bg);
}
/* see also additional rules in Link Styling section */
/** Copyright *****************************************************************/
p.copyright,
p.copyright small { font-size: small; }
/** Back to Top / ToC Toggle **************************************************/
@media print {
#toc-nav {
display: none;
}
}
@media not print {
#toc-nav {
position: fixed;
z-index: 3;
bottom: 0; left: 0;
margin: 0;
min-width: 1.33em;
border-top-right-radius: 2rem;
box-shadow: 0 0 2px;
font-size: 1.5em;
}
#toc-nav > a {
display: block;
white-space: nowrap;
height: 1.33em;
padding: .1em 0.3em;
margin: 0;
box-shadow: 0 0 2px;
border: none;
border-top-right-radius: 1.33em;
color: #707070;
color: var(--tocnav-normal-text);
background: white;
background: var(--tocnav-normal-bg);
}
#toc-nav > a:hover,
#toc-nav > a:focus {
color: black;
color: var(--tocnav-hover-text);
background: #f8f8f8;
background: var(--tocnav-hover-bg);
}
#toc-nav > a:active {
color: #c00;
color: var(--tocnav-active-text);
background: white;
background: var(--tocnav-active-bg);
}
#toc-nav > #toc-jump {
padding-bottom: 2em;
margin-bottom: -1.9em;
}
/* statusbar gets in the way on keyboard focus; remove once browsers fix */
#toc-nav > a[href="#toc"]:not(:hover):focus:last-child {
padding-bottom: 1.5rem;
}
#toc-nav:not(:hover) > a:not(:focus) > span + span {
/* Ideally this uses :focus-within on #toc-nav */
display: none;
}
#toc-nav > a > span + span {
padding-right: 0.2em;
}
}
/** ToC Sidebar ***************************************************************/
/* Floating sidebar */
@media screen {
body.toc-sidebar #toc {
position: fixed;
top: 0; bottom: 0;
left: 0;
width: 23.5em;
max-width: 80%;
max-width: calc(100% - 2em - 26px);
overflow: auto;
padding: 0 1em;
padding-left: 42px;
padding-left: calc(1em + 26px);
color: black;
color: var(--tocsidebar-text);
background: inherit;
background-color: #f7f8f9;
background-color: var(--tocsidebar-bg);
z-index: 1;
box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
}
body.toc-sidebar #toc h2 {
margin-top: .8rem;
font-variant: small-caps;
font-variant: all-small-caps;
text-transform: lowercase;
font-weight: bold;
color: gray;
color: hsla(203,20%,40%,.7);
color: var(--tocsidebar-heading-text);
}
body.toc-sidebar #toc-jump:not(:focus) {
width: 0;
height: 0;
padding: 0;
position: absolute;
overflow: hidden;
}
}
/* Hide main scroller when only the ToC is visible anyway */
@media screen and (max-width: 28em) {
body.toc-sidebar {
overflow: hidden;
}
}
/* Sidebar with its own space */
@media screen and (min-width: 78em) {
body:not(.toc-inline) #toc {
position: fixed;
top: 0; bottom: 0;
left: 0;
width: 23.5em;
overflow: auto;
padding: 0 1em;
padding-left: 42px;
padding-left: calc(1em + 26px);
color: black;
color: var(--tocsidebar-text);
background: inherit;
background-color: #f7f8f9;
background-color: var(--tocsidebar-bg);
z-index: 1;
box-shadow: -.1em 0 .25em rgba(0,0,0,.1) inset;
box-shadow: -.1em 0 .25em var(--tocsidebar-shadow) inset;
}
body:not(.toc-inline) #toc h2 {
margin-top: .8rem;
font-variant: small-caps;
font-variant: all-small-caps;
text-transform: lowercase;
font-weight: bold;
color: gray;
color: hsla(203,20%,40%,.7);
color: var(--tocsidebar-heading-text);
}
body:not(.toc-inline) {
padding-left: 29em;
}
/* See also Overflow section at the bottom */
body:not(.toc-inline) #toc-jump:not(:focus) {
width: 0;
height: 0;
padding: 0;
position: absolute;
overflow: hidden;
}
}
@media screen and (min-width: 90em) {
body:not(.toc-inline) {
margin: 0 4em;
}
}
/******************************************************************************/
/* Sectioning */
/******************************************************************************/
/** Headings ******************************************************************/
h1, h2, h3, h4, h5, h6, dt {
page-break-after: avoid;
page-break-inside: avoid;
font: 100% sans-serif; /* Reset all font styling to clear out UA styles */
font-family: inherit; /* Inherit the font family. */
line-height: 1.2; /* Keep wrapped headings compact */
hyphens: manual; /* Hyphenated headings look weird */
}
h2, h3, h4, h5, h6 {
margin-top: 3rem;
}
h1, h2, h3 {
color: #005A9C;
color: var(--heading-text);
}
h1 { font-size: 170%; }
h2 { font-size: 140%; }
h3 { font-size: 120%; }
h4 { font-weight: bold; }
h5 { font-style: italic; }
h6 { font-variant: small-caps; }
dt { font-weight: bold; }
/** Subheadings ***************************************************************/
h1 + h2,
#profile-and-date {
/* #profile-and-date is a subtitle in an H2 under the H1 */
margin-top: 0;
}
h2 + h3,
h3 + h4,
h4 + h5,
h5 + h6 {
margin-top: 1.2em; /* = 1 x line-height */
}
/** Section divider ***********************************************************/
:not(.head) > :not(.head) + hr {
font-size: 1.5em;
text-align: center;
margin: 1em auto;
height: auto;
color: black;
color: var(--hr-text);
border: transparent solid 0;
background: transparent;
}
:not(.head) > hr::before {
content: "\2727\2003\2003\2727\2003\2003\2727";
}
/******************************************************************************/
/* Paragraphs and Lists */
/******************************************************************************/
p {
margin: 1em 0;
}
dd > p:first-child,
li > p:first-child {
margin-top: 0;
}
ul, ol {
margin-left: 0;
padding-left: 2em;
}
li {
margin: 0.25em 0 0.5em;
padding: 0;
}
dl dd {
margin: 0 0 .5em 2em;
}
.head dd + dd { /* compact for header */
margin-top: -.5em;
}
/* Style for algorithms */
ol.algorithm ol:not(.algorithm),
.algorithm > ol ol:not(.algorithm) {
border-left: 0.5em solid #DEF;
border-left: 0.5em solid var(--algo-border);
}
/* Put nice boxes around each algorithm. */
[data-algorithm]:not(.heading) {
padding: .5em;
border: thin solid #ddd;
border: thin solid var(--algo-border);
border-radius: .5em;
margin: .5em calc(-0.5em - 1px);
}
[data-algorithm]:not(.heading) > :first-child {
margin-top: 0;
}
[data-algorithm]:not(.heading) > :last-child {
margin-bottom: 0;
}
/* Style for switch/case <dl>s */
dl.switch > dd > ol.only,
dl.switch > dd > .only > ol {
margin-left: 0;
}
dl.switch > dd > ol.algorithm,
dl.switch > dd > .algorithm > ol {
margin-left: -2em;
}
dl.switch {
padding-left: 2em;
}
dl.switch > dt {
text-indent: -1.5em;
margin-top: 1em;
}
dl.switch > dt + dt {
margin-top: 0;
}
dl.switch > dt::before {
content: '\21AA';
padding: 0 0.5em 0 0;
display: inline-block;
width: 1em;
text-align: right;
line-height: 0.5em;
}
/** Terminology Markup ********************************************************/
/******************************************************************************/
/* Inline Markup */
/******************************************************************************/
/** Terminology Markup ********************************************************/
dfn { /* Defining instance */
font-weight: bolder;
}
a > i { /* Instance of term */
font-style: normal;
}
dt dfn code, code.idl {
font-size: inherit;
}
dfn var {
font-style: normal;
}
/** Change Marking ************************************************************/
del {
color: #aa0000;
color: var(--del-text);
background: transparent;
background: var(--del-bg);
text-decoration: line-through;
}
ins {
color: #006100;
color: var(--ins-text);
background: transparent;
background: var(--ins-bg);
text-decoration: underline;
}
/* for amendments (candidate/proposed changes) */
.amendment ins, .correction ins, .addition ins,
ins[class^=c] {
text-decoration-style: dotted;
}
.amendment del, .correction del, .addition del,
del[class^=c] {
text-decoration-style: dotted;
}
.amendment.proposed ins, .correction.proposed ins, .addition.proposed ins,
ins[class^=c].proposed {
text-decoration-style: double;
}
.amendment.proposed del, .correction.proposed del, .addition.proposed del,
del[class^=c].proposed {
text-decoration-style: double;
}
/** Miscellaneous improvements to inline formatting ***************************/
sup {
vertical-align: super;
font-size: 80%
}
/******************************************************************************/
/* Code */
/******************************************************************************/
/** General monospace/pre rules ***********************************************/
pre, code, samp {
font-family: Menlo, Consolas, "DejaVu Sans Mono", Monaco, monospace;
font-size: .9em;
hyphens: none;
text-transform: none;
text-align: left;
text-align: start;
font-variant: normal;
orphans: 3;
widows: 3;
page-break-before: avoid;
}
pre code,
code code {
font-size: 100%;
}
pre {
margin-top: 1em;
margin-bottom: 1em;
overflow: auto;
}
/** Inline Code fragments *****************************************************/
/* Do something nice. */
/******************************************************************************/
/* Links */
/******************************************************************************/
/** General Hyperlinks ********************************************************/
/* We hyperlink a lot, so make it less intrusive */
a[href] {
color: #034575;
color: var(--a-normal-text);
text-decoration: underline #707070;
text-decoration: underline var(--a-normal-underline);
text-decoration-skip-ink: none;
}
a:visited {
color: #034575;
color: var(--a-visited-text);
text-decoration-color: #bbb;
text-decoration-color: var(--a-visited-underline);
}
/* Indicate interaction with the link */
a[href]:focus,
a[href]:hover {
text-decoration-thickness: 2px;
}
a[href]:active {
color: #c00;
color: var(--a-active-text);
text-decoration-color: #c00;
text-decoration-color: var(--a-active-underline);
}
/* Backout above styling for W3C logo */
.head .logo,
.head .logo a {
border: none;
text-decoration: none;
background: transparent;
}
/******************************************************************************/
/* Images */
/******************************************************************************/
img {
border-style: none;
}
img, svg {
/* Intentionally not color-scheme aware. */
background: white;
}
/* For autogen numbers, add
.caption::before, figcaption::before { content: "Figure " counter(figure) ". "; }
*/
figure, .figure, .sidefigure {
page-break-inside: avoid;
text-align: center;
margin: 2.5em 0;
}
.figure img, .sidefigure img, figure img,
.figure object, .sidefigure object, figure object {
max-width: 100%;
margin: auto;
height: auto;
}
.figure pre, .sidefigure pre, figure pre {
text-align: left;
display: table;
margin: 1em auto;
}
.figure table, figure table {
margin: auto;
}
@media screen and (min-width: 20em) {
.sidefigure {
float: right;
width: 50%;
margin: 0 0 0.5em 0.5em;
}
}
.caption, figcaption, caption {
font-style: italic;
font-size: 90%;
}
.caption::before, figcaption::before, figcaption > .marker {
font-weight: bold;
}
.caption, figcaption {
counter-increment: figure;
}
/* DL list is indented 2em, but figure inside it is not */
dd > .figure, dd > figure { margin-left: -2em; }
/******************************************************************************/
/* Colored Boxes */
/******************************************************************************/
.issue, .note, .example, .assertion, .advisement, blockquote,
.amendment, .correction, .addition {
margin: 1em auto;
padding: .5em;
border: .5em;
border-left-style: solid;
page-break-inside: avoid;
}
span.issue, span.note {
padding: .1em .5em .15em;
border-right-style: solid;
}
blockquote > :first-child,
.note > p:first-child,
.issue > p:first-child,
.amendment > p:first-child,
.correction > p:first-child,
.addition > p:first-child {
margin-top: 0;
}
blockquote > :last-child,
.note > p:last-child,
.issue > p:last-child,
.amendment > p:last-child,
.correction > p:last-child,
.addition > p:last-child {
margin-bottom: 0;
}
.issue::before, .issue > .marker,
.example::before, .example > .marker,
.note::before, .note > .marker,
details.note > summary > .marker,
.amendment::before, .amendment > .marker,
details.amendment > summary > .marker,
.addition::before, .addition > .marker,
addition.amendment > summary > .marker,
.correction::before, .correction > .marker,
correction.amendment > summary > .marker
{
text-transform: uppercase;
padding-right: 1em;
}
.example::before, .example > .marker {
display: block;
padding-right: 0em;
}
/** Blockquotes ***************************************************************/
blockquote {
border-color: silver;
border-color: var(--blockquote-border);
background: transparent;
background: var(--blockquote-bg);
color: currentcolor;
color: var(--blockquote-text);
}
/** Open issue ****************************************************************/
.issue {
border-color: #e05252;
border-color: var(--issue-border);
background: #fbe9e9;
background: var(--issue-bg);
color: black;
color: var(--issue-text);
counter-increment: issue;
overflow: auto;
}
.issue::before, .issue > .marker {
color: #831616;
color: var(--issueheading-text);
}
/* Add .issue::before { content: "Issue " counter(issue) " "; } for autogen numbers,
or use class="marker" to mark up the issue number in source. */
/** Example *******************************************************************/
.example {
border-color: #e0cb52;
border-color: var(--example-border);
background: #fcfaee;
background: var(--example-bg);
color: black;
color: var(--example-text);
counter-increment: example;
overflow: auto;
clear: both;
}
.example::before, .example > .marker {
color: #574b0f;
color: var(--exampleheading-text);
}
/* Add .example::before { content: "Example " counter(example) " "; } for autogen numbers,
or use class="marker" to mark up the example number in source. */
/** Non-normative Note ********************************************************/
.note {
border-color: #52e052;
border-color: var(--note-border);
background: #e9fbe9;
background: var(--note-bg);
color: black;
color: var(--note-text);
overflow: auto;
}
.note::before, .note > .marker,
details.note > summary {
color: hsl(120, 70%, 30%);
color: var(--noteheading-text);
}
/* Add .note::before { content: "Note "; } for autogen label,
or use class="marker" to mark up the label in source. */
details.note[open] > summary {
border-bottom: 1px silver solid;
border-bottom: 1px var(--notesummary-underline) solid;
}
/** Assertion Box *************************************************************/
/* for assertions in algorithms */
.assertion {
border-color: #AAA;
border-color: var(--assertion-border);
background: #EEE;
background: var(--assertion-bg);
color: black;
color: var(--assertion-text);
}
/** Advisement Box ************************************************************/
/* for attention-grabbing normative statements */
.advisement {
border-color: orange;
border-color: var(--advisement-border);
border-style: none solid;
background: #fec;
background: var(--advisement-bg);
color: black;
color: var(--advisement-text);
}
strong.advisement {
display: block;
text-align: center;
}
.advisement::before, .advisement > .marker {
color: #b35f00;
color: var(--advisementheading-text);
}
/** Amendment Box *************************************************************/
.amendment, .correction, .addition {
border-color: #330099;
border-color: var(--amendment-border);
background: #F5F0FF;
background: var(--amendment-bg);
color: black;
color: var(--amendment-text);
}
.amendment.proposed, .correction.proposed, .addition.proposed {
border-style: solid;
border-block-width: 0.25em;
}
.amendment::before, .amendment > .marker,
details.amendment > summary::before, details.amendment > summary > .marker,
.correction::before, .correction > .marker,
details.correction > summary::before, details.correction > summary > .marker,
.addition::before, .addition > .marker,
details.addition > summary::before, details.addition > summary > .marker {
color: #220066;
color: var(--amendmentheading-text);
}
.amendment.proposed::before, .amendment.proposed > .marker,
details.amendment.proposed > summary::before, details.amendment.proposed > summary > .marker,
.correction.proposed::before, .correction.proposed > .marker,
details.correction.proposed > summary::before, details.correction.proposed > summary > .marker,
.addition.proposed::before, .addition.proposed > .marker,
details.addition.proposed > summary::before, details.addition.proposed > summary > .marker {
font-weight: bold;
}
/** Spec Obsoletion Notice ****************************************************/
/* obnoxious obsoletion notice for older/abandoned specs. */
details {
display: block;
}
summary {
font-weight: bolder;
}
.annoying-warning:not(details),
details.annoying-warning:not([open]) > summary,
details.annoying-warning[open] {
background: hsla(40,100%,50%,0.95);
background: var(--warning-bg);
color: black;
color: var(--warning-text);
padding: .75em 1em;
border: red;
border: var(--warning-border);
border-style: solid none;
box-shadow: 0 2px 8px black;
text-align: center;
}
.annoying-warning :last-child {
margin-bottom: 0;
}
@media not print {
details.annoying-warning[open] {
position: fixed;
left: 0;
right: 0;
bottom: 2em;
z-index: 1000;
}
}
details.annoying-warning:not([open]) > summary {
text-align: center;
}
/** Entity Definition Boxes ***************************************************/
.def {
padding: .5em 1em;
background: #def;
background: var(--def-bg);
margin: 1.2em 0;
border-left: 0.5em solid #8ccbf2;
border-left: 0.5em solid var(--def-border);
color: black;
color: var(--def-text);
}
/******************************************************************************/
/* Tables */
/******************************************************************************/
th, td {
text-align: left;
text-align: start;
}
/** Property/Descriptor Definition Tables *************************************/
table.def {
/* inherits .def box styling, see above */
width: 100%;
border-spacing: 0;
}
table.def td,
table.def th {
padding: 0.5em;
vertical-align: baseline;
border-bottom: 1px solid #bbd7e9;
border-bottom: 1px solid var(--defrow-border);
}
table.def > tbody > tr:last-child th,
table.def > tbody > tr:last-child td {
border-bottom: 0;
}
table.def th {
font-style: italic;
font-weight: normal;
padding-left: 1em;
width: 3em;
}
/* For when values are extra-complex and need formatting for readability */
table td.pre {
white-space: pre-wrap;
}
/* A footnote at the bottom of a def table */
table.def td.footnote {
padding-top: 0.6em;
}
table.def td.footnote::before {
content: " ";
display: block;
height: 0.6em;
width: 4em;
border-top: thin solid;
}
/** Data tables (and properly marked-up index tables) *************************/
/*
<table class="data"> highlights structural relationships in a table
when correct markup is used (e.g. thead/tbody, th vs. td, scope attribute)
Use class="complex data" for particularly complicated tables --
(This will draw more lines: busier, but clearer.)
Use class="long" on table cells with paragraph-like contents
(This will adjust text alignment accordingly.)
Alternately use class="longlastcol" on tables, to have the last column assume "long".
*/
table {
word-wrap: normal;
overflow-wrap: normal;
hyphens: manual;
}
table.data,
table.index {
margin: 1em auto;
border-collapse: collapse;
border: hidden;
width: 100%;
}
table.data caption,
table.index caption {
max-width: 50em;
margin: 0 auto 1em;
}
table.data td, table.data th,
table.index td, table.index th {
padding: 0.5em 1em;
border-width: 1px;
border-color: silver;
border-color: var(--datacell-border);
border-top-style: solid;
}
table.data thead td:empty {
padding: 0;
border: 0;
}
table.data thead,
table.index thead,
table.data tbody,
table.index tbody {
border-bottom: 2px solid;
}
table.data colgroup,
table.index colgroup {
border-left: 2px solid;
}
table.data tbody th:first-child,
table.index tbody th:first-child {
border-right: 2px solid;
border-top: 1px solid silver;
border-top: 1px solid var(--datacell-border);
padding-right: 1em;
}
table.data th[colspan],
table.data td[colspan] {
text-align: center;
}
table.complex.data th,
table.complex.data td {
border: 1px solid silver;
border: 1px solid var(--datacell-border);
text-align: center;
}
table.data.longlastcol td:last-child,
table.data td.long {
vertical-align: baseline;
text-align: left;
}
table.data img {
vertical-align: middle;
}
/*
Alternate table alignment rules
table.data,
table.index {
text-align: center;
}
table.data thead th[scope="row"],
table.index thead th[scope="row"] {
text-align: right;
}
table.data tbody th:first-child,
table.index tbody th:first-child {
text-align: right;
}
Possible extra rowspan handling
table.data tbody th[rowspan]:not([rowspan='1']),
table.index tbody th[rowspan]:not([rowspan='1']),
table.data tbody td[rowspan]:not([rowspan='1']),
table.index tbody td[rowspan]:not([rowspan='1']) {
border-left: 1px solid silver;
}
table.data tbody th[rowspan]:first-child,
table.index tbody th[rowspan]:first-child,
table.data tbody td[rowspan]:first-child,
table.index tbody td[rowspan]:first-child{
border-left: 0;
border-right: 1px solid silver;
}
*/
/******************************************************************************/
/* Indices */
/******************************************************************************/
/** Table of Contents *********************************************************/
.toc a {
/* More spacing; use padding to make it part of the click target. */
padding: 0.1rem 1px 0;
/* Larger, more consistently-sized click target */
display: block;
/* Switch to using border-bottom for underlines */
text-decoration: none;
border-bottom: 1px solid;
/* Reverse color scheme */
color: black;
color: var(--toclink-text);
border-color: #3980b5;
border-color: var(--toclink-underline);
}
.toc a:visited {
color: black;
color: var(--toclink-visited-text);
border-color: #054572;
border-color: var(--toclink-visited-underline);
}
.toc a:focus,
.toc a:hover {
background: rgba(75%, 75%, 75%, .25);
background: var(--a-hover-bg);
border-bottom-width: 3px;
margin-bottom: -2px;
}
.toc a:not(:focus):not(:hover) {
/* Allow colors to cascade through from link styling */
border-bottom-color: transparent;
}
.toc, .toc ol, .toc ul, .toc li {
list-style: none; /* Numbers must be inlined into source */
/* because generated content isn't search/selectable and markers can't do multilevel yet */
margin: 0;
padding: 0;
}
.toc {
line-height: 1.1em;
}
/* ToC not indented until third level, but font style & margins show hierarchy */
.toc > li { font-weight: bold; }
.toc > li li { font-weight: normal; }
.toc > li li li { font-size: 95%; }
.toc > li li li li { font-size: 90%; }
.toc > li li li li li { font-size: 85%; }
/* @supports not (display:grid) { */
.toc > li { margin: 1.5rem 0; }
.toc > li li { margin: 0.3rem 0; }
.toc > li li li { margin-left: 2rem; }
/* Section numbers in a column of their own */
.toc .secno {
float: left;
width: 4rem;
white-space: nowrap;
}
.toc > li li li li .secno { font-size: 85%; }
.toc > li li li li li .secno { font-size: 100%; }
.toc li {
clear: both;
}
:not(li) > .toc { margin-left: 5rem; }
.toc .secno { margin-left: -5rem; }
.toc > li li li .secno { margin-left: -7rem; }
.toc > li li li li .secno { margin-left: -9rem; }
.toc > li li li li li .secno { margin-left: -11rem; }
/* Tighten up indentation in narrow ToCs */
@media (max-width: 30em) {
:not(li) > .toc { margin-left: 4rem; }
.toc .secno { margin-left: -4rem; }
.toc > li li li { margin-left: 1rem; }
.toc > li li li .secno { margin-left: -5rem; }
.toc > li li li li .secno { margin-left: -6rem; }
.toc > li li li li li .secno { margin-left: -7rem; }
}
/* Loosen it on wide screens */
@media screen and (min-width: 78em) {
body:not(.toc-inline) :not(li) > .toc { margin-left: 4rem; }
body:not(.toc-inline) .toc .secno { margin-left: -4rem; }
body:not(.toc-inline) .toc > li li li { margin-left: 1rem; }
body:not(.toc-inline) .toc > li li li .secno { margin-left: -5rem; }
body:not(.toc-inline) .toc > li li li li .secno { margin-left: -6rem; }
body:not(.toc-inline) .toc > li li li li li .secno { margin-left: -7rem; }
}
/* } */
@supports (display:grid) and (display:contents) {
/* Use #toc over .toc to override non-@supports rules. */
#toc {
display: grid;
align-content: start;
grid-template-columns: auto 1fr;
grid-column-gap: 1rem;
column-gap: 1rem;
grid-row-gap: .6rem;
row-gap: .6rem;
}
#toc h2 {
grid-column: 1 / -1;
margin-bottom: 0;
}
#toc ol,
#toc li,
#toc a {
display: contents;
/* Switch <a> to subgrid when supported */
}
#toc span {
margin: 0;
}
#toc > .toc > li > a > span {
/* The spans of the top-level list,
comprising the first items of each top-level section. */
margin-top: 1.1rem;
}
#toc#toc .secno { /* Ugh, need more specificity to override base.css */
grid-column: 1;
width: auto;
margin-left: 0;
}
#toc .content {
grid-column: 2;
width: auto;
margin-right: 1rem;
}
#toc .content:hover,
#toc .content:focus {
background: rgba(75%, 75%, 75%, .25);
background: var(--a-hover-bg);
border-bottom: 3px solid #054572;
border-bottom: 3px solid var(--toclink-underline);
margin-bottom: -3px;
}
#toc li li li .content {
margin-left: 1rem;
}
#toc li li li li .content {
margin-left: 2rem;
}
}
/** Index *********************************************************************/
/* Index Lists: Layout */
ul.index { margin-left: 0; columns: 15em; text-indent: 1em hanging; }
ul.index li { margin-left: 0; list-style: none; break-inside: avoid; }
ul.index li li { margin-left: 1em; }
ul.index dl { margin-top: 0; }
ul.index dt { margin: .2em 0 .2em 20px;}
ul.index dd { margin: .2em 0 .2em 40px;}
/* Index Lists: Typography */
ul.index ul,
ul.index dl { font-size: smaller; }
@media not print {
ul.index li a + span {
white-space: nowrap;
color: transparent; }
ul.index li a:hover + span,
ul.index li a:focus + span {
color: #707070;
color: var(--indexinfo-text);
}
}
/** Index Tables *****************************************************/
/* See also the data table styling section, which this effectively subclasses */
table.index {
font-size: small;
border-collapse: collapse;
border-spacing: 0;
text-align: left;
margin: 1em 0;
}
table.index td,
table.index th {
padding: 0.4em;
}
table.index tr:hover td:not([rowspan]),
table.index tr:hover th:not([rowspan]) {
color: black;
color: var(--indextable-hover-text);
background: #f7f8f9;
background: var(--indextable-hover-bg);
}
/* The link in the first column in the property table (formerly a TD) */
table.index th:first-child a {
font-weight: bold;
}
/** Outdated warning **********************************************************/
.outdated-spec {
color: black;
color: var(--outdatedspec-text);
background-color: rgba(0,0,0,0.5);
background-color: var(--outdatedspec-bg);
}
.outdated-warning {
position: fixed;
bottom: 50%;
left: 0;
right: 0;
margin: 0 auto;
width: 50%;
background: maroon;
background: var(--outdated-bg);
color: white;
color: var(--outdated-text);
border-radius: 1em;
box-shadow: 0 0 1em red;
box-shadow: 0 0 1em var(--outdated-shadow);
padding: 2em;
text-align: center;
z-index: 2;
}
.outdated-warning a {
color: currentcolor;
background: transparent;
}
.edited-rec-warning {
background: darkorange;
background: var(--editedrec-bg);
box-shadow: 0 0 1em;
}
.outdated-warning button {
color: var(--outdated-text);
border-radius: 1em;
box-shadow: 0 0 1em red;
box-shadow: 0 0 1em var(--outdated-shadow);
padding: 2em;
text-align: center;
z-index: 2;
}
.outdated-warning a {
color: currentcolor;
background: transparent;
}
.edited-rec-warning {
background: darkorange;
background: var(--editedrec-bg);
box-shadow: 0 0 1em;
}
.outdated-warning button {
position: absolute;
top: 0;
right:0;
margin: 0;
border: 0;
padding: 0.25em 0.5em;
background: transparent;
color: white;
color: var(--outdated-text);
font:1em sans-serif;
text-align:center;
}
.outdated-warning span {
display: block;
}
.outdated-collapsed {
bottom: 0;
border-radius: 0;
width: 100%;
padding: 0;
}
/******************************************************************************/
/* Print */
/******************************************************************************/
@media print {
/* Pages have their own margins. */
html {
margin: 0;
}
/* Serif for print. */
body {
font-family: serif;
}
.outdated-warning {
position: absolute;
border-style: solid;
border-color: red;
}
.outdated-warning input {
display: none;
}
}
@page {
margin: 1.5cm 1.1cm;
}
/******************************************************************************/
/* Overflow Control */
/******************************************************************************/
.figure .caption, .sidefigure .caption, figcaption {
/* in case figure is overlarge, limit caption to 50em */
max-width: 50rem;
margin-left: auto;
margin-right: auto;
}
.overlarge {
/* Magic to create good item positioning:
"content column" is 50ems wide at max; less on smaller screens.
Extra space (after ToC + content) is empty on the right.
1. When item < content column, centers item in column.
2. When content < item < available, left-aligns.
3. When item > available, fills available + scroll bar.
*/
display: grid;
grid-template-columns: minmax(0, 50em);
}
.overlarge > table {
/* limit preferred width of table */
max-width: 50em;
margin-left: auto;
margin-right: auto;
}
@media (min-width: 55em) {
.overlarge {
margin-right: calc(13px + 26.5rem - 50vw);
max-width: none;
}
}
@media screen and (min-width: 78em) {
body:not(.toc-inline) .overlarge {
/* 30.5em body padding 50em content area */
margin-right: calc(40em - 50vw) !important;
}
}
@media screen and (min-width: 90em) {
body:not(.toc-inline) .overlarge {
/* 4em html margin 30.5em body padding 50em content area */
margin-right: calc(84.5em - 100vw) !important;
}
}
@media not print {
.overlarge {
overflow-x: auto;
/* See Lea Verou's explanation background-attachment:
* http://lea.verou.me/2012/04/background-attachment-local/
*
background: top left / 4em 100% linear-gradient(to right, #ffffff, rgba(255, 255, 255, 0)) local,
top right / 4em 100% linear-gradient(to left, #ffffff, rgba(255, 255, 255, 0)) local,
top left / 1em 100% linear-gradient(to right, #c3c3c5, rgba(195, 195, 197, 0)) scroll,
top right / 1em 100% linear-gradient(to left, #c3c3c5, rgba(195, 195, 197, 0)) scroll,
white;
background-repeat: no-repeat;
*/
}
}
</style>
<meta content="Bikeshed version 5fcd28d6d, updated Tue May 30 13:12:11 2023 -0700" name="generator">
<meta content="2ec2dd7752939adf032c92c0ed97d7908b381965" name="document-revision">
<style>/* Boilerplate: style-autolinks */
.css.css, .property.property, .descriptor.descriptor {
color: var(--a-normal-text);
font-size: inherit;
font-family: inherit;
}
.css::before, .property::before, .descriptor::before {
content: "";
}
.css::after, .property::after, .descriptor::after {
content: "";
}
.property, .descriptor {
/* Don't wrap property and descriptor names */
white-space: nowrap;
}
.type { /* CSS value <type> */
font-style: italic;
}
pre .property::before, pre .property::after {
content: "";
}
[data-link-type="property"]::before,
[data-link-type="propdesc"]::before,
[data-link-type="descriptor"]::before,
[data-link-type="value"]::before,
[data-link-type="function"]::before,
[data-link-type="at-rule"]::before,
[data-link-type="selector"]::before,
[data-link-type="maybe"]::before {
content: "";
}
[data-link-type="property"]::after,
[data-link-type="propdesc"]::after,
[data-link-type="descriptor"]::after,
[data-link-type="value"]::after,
[data-link-type="function"]::after,
[data-link-type="at-rule"]::after,
[data-link-type="selector"]::after,
[data-link-type="maybe"]::after {
content: "";
}
[data-link-type].production::before,
[data-link-type].production::after,
.prod [data-link-type]::before,
.prod [data-link-type]::after {
content: "";
}
[data-link-type=element],
[data-link-type=element-attr] {
font-family: Menlo, Consolas, "DejaVu Sans Mono", monospace;
font-size: .9em;
}
[data-link-type=element]::before { content: "<" }
[data-link-type=element]::after { content: ">" }
[data-link-type=biblio] {
white-space: pre;
}
@media (prefers-color-scheme: dark) {
:root {
--selflink-text: black;
--selflink-bg: silver;
--selflink-hover-text: white;
}
}
</style>
<style>/* Boilerplate: style-colors */
/* Any --*-text not paired with a --*-bg is assumed to have a transparent bg */
:root {
color-scheme: light dark;
--text: black;
--bg: white;
--unofficial-watermark: url(https://www.w3.org/StyleSheets/TR/2016/logos/UD-watermark);
--logo-bg: #1a5e9a;
--logo-active-bg: #c00;
--logo-text: white;
--tocnav-normal-text: #707070;
--tocnav-normal-bg: var(--bg);
--tocnav-hover-text: var(--tocnav-normal-text);
--tocnav-hover-bg: #f8f8f8;
--tocnav-active-text: #c00;
--tocnav-active-bg: var(--tocnav-normal-bg);
--tocsidebar-text: var(--text);
--tocsidebar-bg: #f7f8f9;
--tocsidebar-shadow: rgba(0,0,0,.1);
--tocsidebar-heading-text: hsla(203,20%,40%,.7);
--toclink-text: var(--text);
--toclink-underline: #3980b5;
--toclink-visited-text: var(--toclink-text);
--toclink-visited-underline: #054572;
--heading-text: #005a9c;
--hr-text: var(--text);
--algo-border: #def;
--del-text: red;
--del-bg: transparent;
--ins-text: #080;
--ins-bg: transparent;
--a-normal-text: #034575;
--a-normal-underline: #bbb;
--a-visited-text: var(--a-normal-text);
--a-visited-underline: #707070;
--a-hover-bg: rgba(75%, 75%, 75%, .25);
--a-active-text: #c00;
--a-active-underline: #c00;
--blockquote-border: silver;
--blockquote-bg: transparent;
--blockquote-text: currentcolor;
--issue-border: #e05252;
--issue-bg: #fbe9e9;
--issue-text: var(--text);
--issueheading-text: #831616;
--example-border: #e0cb52;
--example-bg: #fcfaee;
--example-text: var(--text);
--exampleheading-text: #574b0f;
--note-border: #52e052;
--note-bg: #e9fbe9;
--note-text: var(--text);
--noteheading-text: hsl(120, 70%, 30%);
--notesummary-underline: silver;
--assertion-border: #aaa;
--assertion-bg: #eee;
--assertion-text: black;
--advisement-border: orange;
--advisement-bg: #fec;
--advisement-text: var(--text);
--advisementheading-text: #b35f00;
--warning-border: red;
--warning-bg: hsla(40,100%,50%,0.95);
--warning-text: var(--text);
--amendment-border: #330099;
--amendment-bg: #F5F0FF;
--amendment-text: var(--text);
--amendmentheading-text: #220066;
--def-border: #8ccbf2;
--def-bg: #def;
--def-text: var(--text);
--defrow-border: #bbd7e9;
--datacell-border: silver;
--indexinfo-text: #707070;
--indextable-hover-text: black;
--indextable-hover-bg: #f7f8f9;
--outdatedspec-bg: rgba(0, 0, 0, .5);
--outdatedspec-text: black;
--outdated-bg: maroon;
--outdated-text: white;
--outdated-shadow: red;
--editedrec-bg: darkorange;
}
@media (prefers-color-scheme: dark) {
:root {
--text: #ddd;
--bg: black;
--unofficial-watermark: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='400' height='400'%3E%3Cg fill='%23100808' transform='translate(200 200) rotate(-45) translate(-200 -200)' stroke='%23100808' stroke-width='3'%3E%3Ctext x='50%25' y='220' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EUNOFFICIAL%3C/text%3E%3Ctext x='50%25' y='305' style='font: bold 70px sans-serif; text-anchor: middle; letter-spacing: 6px;'%3EDRAFT%3C/text%3E%3C/g%3E%3C/svg%3E");
--logo-bg: #1a5e9a;
--logo-active-bg: #c00;
--logo-text: white;
--tocnav-normal-text: #999;
--tocnav-normal-bg: var(--bg);
--tocnav-hover-text: var(--tocnav-normal-text);
--tocnav-hover-bg: #080808;
--tocnav-active-text: #f44;
--tocnav-active-bg: var(--tocnav-normal-bg);
--tocsidebar-text: var(--text);
--tocsidebar-bg: #080808;
--tocsidebar-shadow: rgba(255,255,255,.1);
--tocsidebar-heading-text: hsla(203,20%,40%,.7);
--toclink-text: var(--text);
--toclink-underline: #6af;
--toclink-visited-text: var(--toclink-text);
--toclink-visited-underline: #054572;
--heading-text: #8af;
--hr-text: var(--text);
--algo-border: #456;
--del-text: #f44;
--del-bg: transparent;
--ins-text: #4a4;
--ins-bg: transparent;
--a-normal-text: #6af;
--a-normal-underline: #555;
--a-visited-text: var(--a-normal-text);
--a-visited-underline: var(--a-normal-underline);
--a-hover-bg: rgba(25%, 25%, 25%, .2);
--a-active-text: #f44;
--a-active-underline: var(--a-active-text);
--borderedblock-bg: rgba(255, 255, 255, .05);
--blockquote-border: silver;
--blockquote-bg: var(--borderedblock-bg);
--blockquote-text: currentcolor;
--issue-border: #e05252;
--issue-bg: var(--borderedblock-bg);
--issue-text: var(--text);
--issueheading-text: hsl(0deg, 70%, 70%);
--example-border: hsl(50deg, 90%, 60%);
--example-bg: var(--borderedblock-bg);
--example-text: var(--text);
--exampleheading-text: hsl(50deg, 70%, 70%);
--note-border: hsl(120deg, 100%, 35%);
--note-bg: var(--borderedblock-bg);
--note-text: var(--text);
--noteheading-text: hsl(120, 70%, 70%);
--notesummary-underline: silver;
--assertion-border: #444;
--assertion-bg: var(--borderedblock-bg);
--assertion-text: var(--text);
--advisement-border: orange;
--advisement-bg: #222218;
--advisement-text: var(--text);
--advisementheading-text: #f84;
--warning-border: red;
--warning-bg: hsla(40,100%,20%,0.95);
--warning-text: var(--text);
--amendment-border: #330099;
--amendment-bg: #080010;
--amendment-text: var(--text);
--amendmentheading-text: #cc00ff;
--def-border: #8ccbf2;
--def-bg: #080818;
--def-text: var(--text);
--defrow-border: #136;
--datacell-border: silver;
--indexinfo-text: #aaa;
--indextable-hover-text: var(--text);
--indextable-hover-bg: #181818;
--outdatedspec-bg: rgba(255, 255, 255, .5);
--outdatedspec-text: black;
--outdated-bg: maroon;
--outdated-text: white;
--outdated-shadow: red;
--editedrec-bg: darkorange;
}
/* In case a transparent-bg image doesn't expect to be on a dark bg,
which is quite common in practice... */
img { background: white; }
}
</style>
<style>/* Boilerplate: style-counters */
body {
counter-reset: example figure issue;
}
.issue {
counter-increment: issue;
}
.issue:not(.no-marker)::before {
content: "Issue " counter(issue);
}
.example {
counter-increment: example;
}
.example:not(.no-marker)::before {
content: "Example " counter(example);
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<body class="h-entry">
<div class="head">
<p data-fill-with="logo"></p>
<h1 class="p-name no-ref" id="title">Web Environment Integrity</h1>
<h2 class="no-num no-toc no-ref heading settled" id="profile-and-date"><span class="content">A Collection of Interesting Ideas, <time class="dt-updated" datetime="2023-06-16">16 June 2023</time></span></h2>
<div data-fill-with="spec-metadata">
<dl>
<dt>Issue Tracking:
<dd><a href="https://github.com/RupertBenWiser/Web-Environment-Integrity/issues/">GitHub</a>
<dt class="editor">Editor:
<dd class="editor p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:bewise@chromium.org">Ben Wiser</a> (<span class="p-org org">Google</span>)
</dl>
</div>
<div data-fill-with="warning"></div>
<p class="copyright" data-fill-with="copyright"><a href="http://creativecommons.org/publicdomain/zero/1.0/" rel="license"><img alt="CC0" height="15" src="https://licensebuttons.net/p/zero/1.0/80x15.png" width="80"></a> To the extent possible under law, the editors have waived all copyright
and related or neighboring rights to this work.
In addition, as of 16 June 2023,
the editors have made this specification available under the <a href="http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0" rel="license">Open Web Foundation Agreement Version 1.0</a>,
which is available at http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0.
Parts of this work may be from another specification document. If so, those parts are instead covered by the license of that specification document. </p>
<hr title="Separator for header">
</div>
<div class="p-summary" data-fill-with="abstract">
<h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
<p>An API used to integrity check the environment a web page runs on. This check is performed
by trusted attesters.</p>
</div>
<div data-fill-with="at-risk"></div>
<nav data-fill-with="table-of-contents" id="toc">
<h2 class="no-num no-toc no-ref" id="contents">Table of Contents</h2>
<ol class="toc" role="directory">
<li>
<a href="#introduction"><span class="secno">1</span> <span class="content">Introduction</span></a>
<ol class="toc">
<li><a href="#motivations"><span class="secno">1.1</span> <span class="content">Motivations</span></a>
<li><a href="#examples"><span class="secno">1.2</span> <span class="content">Examples</span></a>
</ol>
<li><a href="#key-terms"><span class="secno">2</span> <span class="content">Key terms</span></a>
<li>
<a href="#attester"><span class="secno">3</span> <span class="content">Attesters</span></a>
<ol class="toc">
<li><a href="#attester-tokens"><span class="secno">3.1</span> <span class="content">Token Format</span></a>
<li><a href="#attester-browser-requirements"><span class="secno">3.2</span> <span class="content">Browser Acceptance Requirements</span></a>
<li><a href="#attester-connection"><span class="secno">3.3</span> <span class="content"><code class="idl"><span>AttesterConnection</span></code></span></a>
</ol>
<li>
<a href="#api"><span class="secno">4</span> <span class="content">Web Environment Integrity API</span></a>
<ol class="toc">
<li>
<a href="#extensions-to-navigator"><span class="secno">4.1</span> <span class="content">Extensions to <code class="idl"><span>Navigator</span></code></span></a>
<ol class="toc">
<li><a href="#navigator-getenvironmentintegrity"><span class="secno">4.1.1</span> <span class="content"><code class="idl"><span>getEnvironmentIntegrity()</span></code></span></a>
</ol>
<li><a href="#environment-integrity"><span class="secno">4.2</span> <span class="content"><code class="idl"><span>EnvironmentIntegrity</span></code></span></a>
</ol>
<li>
<a href="#security-and-privacy"><span class="secno">5</span> <span class="content">Security and privacy considerations</span></a>
<ol class="toc">
<li><a href="#security"><span class="secno">5.1</span> <span class="content">Security considerations</span></a>
<li><a href="#privacy"><span class="secno">5.2</span> <span class="content">Privacy considerations</span></a>
</ol>
<li><a href="#conformance"><span class="secno"></span> <span class="content"> Conformance</span></a>
<li>
<a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
<ol class="toc">
<li><a href="#index-defined-here"><span class="secno"></span> <span class="content">Terms defined by this specification</span></a>
<li><a href="#index-defined-elsewhere"><span class="secno"></span> <span class="content">Terms defined by reference</span></a>
</ol>
<li>
<a href="#references"><span class="secno"></span> <span class="content">References</span></a>
<ol class="toc">
<li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
</ol>
<li><a href="#idl-index"><span class="secno"></span> <span class="content">IDL Index</span></a>
</ol>
</nav>
<main>
<h2 class="heading settled" data-level="1" id="introduction"><span class="secno">1. </span><span class="content">Introduction</span><a class="self-link" href="#introduction"></a></h2>
<p><i>Todo</i></p>
<h3 class="heading settled" data-level="1.1" id="motivations"><span class="secno">1.1. </span><span class="content">Motivations</span><a class="self-link" href="#motivations"></a></h3>
<p><i>Todo</i></p>
<h3 class="heading settled" data-level="1.2" id="examples"><span class="secno">1.2. </span><span class="content">Examples</span><a class="self-link" href="#examples"></a></h3>
<div class="example" id="client-integrity-request">
<a class="self-link" href="#client-integrity-request"></a> Requesting environment integrity attestation.
<pre class="lang-js highlight"><c- c1>// getEnvironmentIntegrity expects a "content binding" of the request you are</c->
<c- c1>// about to make. The content binding protects against this information being</c->
<c- c1>// used for a different request.</c->
<c- c1>// The contentBinding will be concatenated with top-level domain name and hashed</c->
<c- c1>// before it is sent to the attester.</c->
<c- a>const</c-> contentBinding <c- o>=</c-> <c- u>"/someRequestPath?requestID=xxxx"</c-> <c- o>+</c->
<c- u>"Any other data needed for a request-specific contentBinding..."</c-><c- p>;</c->
<c- a>const</c-> attestation <c- o>=</c-> <c- k>await</c-> navigator<c- p>.</c->getEnvironmentIntegrity<c- p>(</c->contentBinding<c- p>);</c->
console<c- p>.</c->log<c- p>(</c->attestation<c- p>.</c->encode<c- p>());</c->
<c- u>"base-64 encoding of the attestation payload and signature approx 500 bytes; see below for details"</c->
<c- c1>// More on attestation validation below</c->
<c- a>const</c-> response <c- o>=</c-> <c- k>await</c-> fetch<c- p>(</c-><c- sb>`/someRequest?requestID=xxxx&amp;attested=</c-><c- si>${</c->attestation<c- p>.</c->encode<c- p>()</c-><c- si>}</c-><c- sb>`</c-><c- p>);</c->
<c- c1>// Do something with this ...</c->
</pre>
</div>
<h2 class="heading settled" data-level="2" id="key-terms"><span class="secno">2. </span><span class="content">Key terms</span><a class="self-link" href="#key-terms"></a></h2>
<p>The <dfn class="dfn-paneled" data-dfn-for="web environment" data-dfn-type="dfn" data-noexport id="web-environment-web-environment">web environment</dfn> is defined as <i>TODO</i></p>
<h2 class="heading settled" data-level="3" id="attester"><span class="secno">3. </span><span class="content">Attesters</span><a class="self-link" href="#attester"></a></h2>
<p>The term <dfn class="dfn-paneled" data-dfn-for="attester" data-dfn-type="dfn" data-noexport id="attester-attester">attester</dfn> refers to a third party capable of returning an <a data-link-type="dfn" href="#integrity-verdict-integrity-verdict" id="ref-for-integrity-verdict-integrity-verdict">Integrity verdict</a>. A <dfn class="dfn-paneled" data-dfn-for="Integrity verdict" data-dfn-type="dfn" data-noexport id="integrity-verdict-integrity-verdict">Integrity verdict</dfn> refers
to a response that confirms if the <a data-link-type="dfn" href="#attester-attester" id="ref-for-attester-attester">attester</a> trusts the <a data-link-type="dfn" href="#web-environment-web-environment" id="ref-for-web-environment-web-environment">web environment</a> the <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#user-agent" id="ref-for-user-agent">user agent</a> is
executing in.</p>
<p>The <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#user-agent" id="ref-for-user-agent①">user agent</a> connects to the <a data-link-type="dfn" href="#attester-attester" id="ref-for-attester-attester①">attester</a> through an <code class="idl"><a data-link-type="idl" href="#attesterconnection" id="ref-for-attesterconnection">AttesterConnection</a></code>.</p>
<p>The <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#user-agent" id="ref-for-user-agent②">user agent</a> SHOULD use separate <code class="idl"><a data-link-type="idl" href="#attesterconnection" id="ref-for-attesterconnection①">AttesterConnection</a></code>s if the <code class="idl"><a data-link-type="idl" href="#attesterconnection" id="ref-for-attesterconnection②">AttesterConnection</a></code> stores state in the <a data-link-type="dfn" href="#integrity-verdict-integrity-verdict" id="ref-for-integrity-verdict-integrity-verdict①">Integrity verdict</a> that can be used for cross site tracking.</p>
<h3 class="heading settled" data-level="3.1" id="attester-tokens"><span class="secno">3.1. </span><span class="content">Token Format</span><a class="self-link" href="#attester-tokens"></a></h3>
<p><i>Todo</i></p>
<h3 class="heading settled" data-level="3.2" id="attester-browser-requirements"><span class="secno">3.2. </span><span class="content">Browser Acceptance Requirements</span><a class="self-link" href="#attester-browser-requirements"></a></h3>
<p><i>Todo</i></p>
<h3 class="heading settled" data-level="3.3" id="attester-connection"><span class="secno">3.3. </span><span class="content"><code class="idl"><a data-link-type="idl" href="#attesterconnection" id="ref-for-attesterconnection③">AttesterConnection</a></code></span><a class="self-link" href="#attester-connection"></a></h3>
<pre class="idl highlight def"><c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="attesterconnection"><code><c- g>AttesterConnection</c-></code></dfn> {
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-ArrayBuffer" id="ref-for-idl-ArrayBuffer"><c- b>ArrayBuffer</c-></a> <dfn class="dfn-paneled idl-code" data-dfn-for="AttesterConnection" data-dfn-type="method" data-export data-lt="getAttestation(contentBinding)" id="dom-attesterconnection-getattestation"><code><c- g>getAttestation</c-></code></dfn>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="AttesterConnection/getAttestation(contentBinding)" data-dfn-type="argument" data-export id="dom-attesterconnection-getattestation-contentbinding-contentbinding"><code><c- g>contentBinding</c-></code><a class="self-link" href="#dom-attesterconnection-getattestation-contentbinding-contentbinding"></a></dfn>);
};
</pre>
<dl>
<dt data-md>getAttestation
<dd data-md>
<p>Returns a COSE signed CBOR object as an ArrayBuffer from the <a data-link-type="dfn" href="#attester-attester" id="ref-for-attester-attester②">attester</a> that contains the <a data-link-type="dfn" href="#integrity-verdict-integrity-verdict" id="ref-for-integrity-verdict-integrity-verdict②">Integrity verdict</a>.</p>
</dl>
<h2 class="heading settled" data-level="4" id="api"><span class="secno">4. </span><span class="content">Web Environment Integrity API</span><a class="self-link" href="#api"></a></h2>
<h3 class="heading settled" data-level="4.1" id="extensions-to-navigator"><span class="secno">4.1. </span><span class="content">Extensions to <code class="idl"><a data-link-type="idl" href="https://html.spec.whatwg.org/multipage/system-state.html#navigator" id="ref-for-navigator">Navigator</a></code></span><a class="self-link" href="#extensions-to-navigator"></a></h3>
<pre class="idl highlight def">[<a class="idl-code" data-link-type="extended-attribute" href="https://webidl.spec.whatwg.org/#Exposed" id="ref-for-Exposed"><c- g>Exposed</c-></a>=<c- n>Window</c->]
<c- b>partial</c-> <c- b>interface</c-> <a class="idl-code" data-link-type="interface" href="https://html.spec.whatwg.org/multipage/system-state.html#navigator" id="ref-for-navigator①"><c- g>Navigator</c-></a> {
[<a class="idl-code" data-link-type="extended-attribute" href="https://webidl.spec.whatwg.org/#SecureContext" id="ref-for-SecureContext"><c- g>SecureContext</c-></a>] <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise" id="ref-for-idl-promise"><c- b>Promise</c-></a>&lt;<a data-link-type="idl-name" href="#environmentintegrity" id="ref-for-environmentintegrity"><c- n>EnvironmentIntegrity</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-navigator-getenvironmentintegrity" id="ref-for-dom-navigator-getenvironmentintegrity"><c- g>getEnvironmentIntegrity</c-></a>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString①"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="Navigator/getEnvironmentIntegrity(contentBinding)" data-dfn-type="argument" data-export id="dom-navigator-getenvironmentintegrity-contentbinding-contentbinding"><code><c- g>contentBinding</c-></code><a class="self-link" href="#dom-navigator-getenvironmentintegrity-contentbinding-contentbinding"></a></dfn>);
};
</pre>
<h4 class="heading settled" data-level="4.1.1" id="navigator-getenvironmentintegrity"><span class="secno">4.1.1. </span><span class="content"><code class="idl"><a data-link-type="idl" href="#dom-navigator-getenvironmentintegrity" id="ref-for-dom-navigator-getenvironmentintegrity①">getEnvironmentIntegrity()</a></code></span><a class="self-link" href="#navigator-getenvironmentintegrity"></a></h4>
<div class="algorithm" data-algorithm="navigator-getenvironmentintegrity-alg">
The <a data-link-type="dfn" href="https://infra.spec.whatwg.org/#user-agent" id="ref-for-user-agent③">user agent</a> has the global <dfn class="dfn-paneled" data-dfn-for="attesterConnection" data-dfn-type="dfn" data-noexport id="attesterconnection-attesterconnection">attesterConnection</dfn>, which is
an <code class="idl"><a data-link-type="idl" href="#attesterconnection" id="ref-for-attesterconnection④">AttesterConnection</a></code> with the <a data-link-type="dfn" href="#attester-attester" id="ref-for-attester-attester③">attester</a>.
<p>The <dfn class="dfn-paneled idl-code" data-dfn-for="Navigator" data-dfn-type="method" data-export id="dom-navigator-getenvironmentintegrity"><code>getEnvironmentIntegrity(<var>contentBinding</var>)</code></dfn> method, when invoked, runs these steps:</p>
<ol>
<li data-md>
<p>Let <var>promise</var> be <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#a-new-promise" id="ref-for-a-new-promise">a new promise</a></p>
<li data-md>
<p>Run the following steps <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/infrastructure.html#in-parallel" id="ref-for-in-parallel">in parallel</a>:</p>
<ol>
<li data-md>
<p>Let <var>environmentIntegrity</var> be a new <code class="idl"><a data-link-type="idl" href="#environmentintegrity" id="ref-for-environmentintegrity①">EnvironmentIntegrity</a></code></p>
<li data-md>
<p>Set <var>environmentIntegrity</var>.<code class="idl"><a data-link-type="idl" href="#dom-environmentintegrity-attestationtoken" id="ref-for-dom-environmentintegrity-attestationtoken">attestationToken</a></code> to <a data-link-type="dfn" href="#attesterconnection-attesterconnection" id="ref-for-attesterconnection-attesterconnection">attesterConnection</a>.<a class="idl-code" data-link-type="method" href="#dom-attesterconnection-getattestation" id="ref-for-dom-attesterconnection-getattestation">getAttestation(<var>contentBinding</var>)</a>. If this fails then:</p>
<ol>
<li data-md>
<p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#reject" id="ref-for-reject">Reject</a> <var>promise</var> with a <i>TODO</i> <a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#dfn-exception" id="ref-for-dfn-exception">Exception</a></p>
<li data-md>
<p>Abort these steps</p>
</ol>
<li data-md>
<p><a data-link-type="dfn" href="https://webidl.spec.whatwg.org/#resolve" id="ref-for-resolve">Resolve</a> <var>promise</var> with <var>environmentIntegrity</var></p>
</ol>
<li data-md>
<p>Return <var>promise</var></p>
</ol>
</div>
<h3 class="heading settled" data-level="4.2" id="environment-integrity"><span class="secno">4.2. </span><span class="content"><code class="idl"><a data-link-type="idl" href="#environmentintegrity" id="ref-for-environmentintegrity②">EnvironmentIntegrity</a></code></span><a class="self-link" href="#environment-integrity"></a></h3>
<pre class="idl highlight def"><c- b>interface</c-> <dfn class="dfn-paneled idl-code" data-dfn-type="interface" data-export id="environmentintegrity"><code><c- g>EnvironmentIntegrity</c-></code></dfn> {
<c- b>readonly</c-> <c- b>attribute</c-> <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-ArrayBuffer" id="ref-for-idl-ArrayBuffer①"><c- b>ArrayBuffer</c-></a> <dfn class="dfn-paneled idl-code" data-dfn-for="EnvironmentIntegrity" data-dfn-type="attribute" data-export data-readonly data-type="ArrayBuffer" id="dom-environmentintegrity-attestationtoken"><code><c- g>attestationToken</c-></code></dfn>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString" id="ref-for-idl-DOMString②"><c- b>DOMString</c-></a> <dfn class="idl-code" data-dfn-for="EnvironmentIntegrity" data-dfn-type="method" data-export data-lt="encode()" id="dom-environmentintegrity-encode"><code><c- g>encode</c-></code><a class="self-link" href="#dom-environmentintegrity-encode"></a></dfn>();
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-object" id="ref-for-idl-object"><c- b>object</c-></a> <dfn class="idl-code" data-dfn-for="EnvironmentIntegrity" data-dfn-type="method" data-export data-lt="toJSON()" id="dom-environmentintegrity-tojson"><code><c- g>toJSON</c-></code><a class="self-link" href="#dom-environmentintegrity-tojson"></a></dfn>();
};
</pre>
<dl>
<dt data-md>attestationToken
<dd data-md>
<p>The attestation token is a COSE signed CBOR object as an ArrayBuffer from the attester.</p>
<dt data-md>encode()
<dd data-md>
<p>The encode method will return a Base64 string representation of the attestation token.</p>
<dt data-md>toJSON()
<dd data-md>
<p>The toJSON method returns a human readable JSON representation of the attestation token. It will first decode the CBOR object. Useful for local debugging.</p>
</dl>
<h2 class="heading settled" data-level="5" id="security-and-privacy"><span class="secno">5. </span><span class="content">Security and privacy considerations</span><a class="self-link" href="#security-and-privacy"></a></h2>
<h3 class="heading settled" data-level="5.1" id="security"><span class="secno">5.1. </span><span class="content">Security considerations</span><a class="self-link" href="#security"></a></h3>
<p><i>Todo</i></p>
<h3 class="heading settled" data-level="5.2" id="privacy"><span class="secno">5.2. </span><span class="content">Privacy considerations</span><a class="self-link" href="#privacy"></a></h3>
<p><i>Todo</i></p>
</main>
<div data-fill-with="conformance">
<h2 class="no-ref no-num heading settled" id="conformance"><span class="content"> Conformance</span><a class="self-link" href="#conformance"></a></h2>
<p> Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology.
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL”
in the normative parts of this document
are to be interpreted as described in RFC 2119.
However, for readability,
these words do not appear in all uppercase letters in this specification. </p>
<p> All of the text of this specification is normative
except sections explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119" title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</a> </p>
<p> Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with <code>class="example"</code>, like this: </p>
<div class="example" id="example-example"><a class="self-link" href="#example-example"></a> This is an example of an informative example. </div>
<p> Informative notes begin with the word “Note”
and are set apart from the normative text with <code>class="note"</code>, like this: </p>
<p class="note" role="note"> Note, this is an informative note.</p>
</div>
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<h2 class="no-num no-ref heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
<h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="content">Terms defined by this specification</span><a class="self-link" href="#index-defined-here"></a></h3>
<ul class="index">
<li><a href="#dom-environmentintegrity-attestationtoken">attestationToken</a><span>, in §4.2</span>
<li><a href="#attester-attester">attester</a><span>, in §3</span>
<li><a href="#attesterconnection">AttesterConnection</a><span>, in §3.3</span>
<li><a href="#attesterconnection-attesterconnection">attesterConnection</a><span>, in §4.1.1</span>
<li><a href="#dom-environmentintegrity-encode">encode()</a><span>, in §4.2</span>
<li><a href="#environmentintegrity">EnvironmentIntegrity</a><span>, in §4.2</span>
<li><a href="#dom-attesterconnection-getattestation">getAttestation(contentBinding)</a><span>, in §3.3</span>
<li><a href="#dom-navigator-getenvironmentintegrity">getEnvironmentIntegrity(contentBinding)</a><span>, in §4.1.1</span>
<li><a href="#integrity-verdict-integrity-verdict">Integrity verdict</a><span>, in §3</span>
<li><a href="#dom-environmentintegrity-tojson">toJSON()</a><span>, in §4.2</span>
<li><a href="#web-environment-web-environment">web environment</a><span>, in §2</span>
</ul>
<h3 class="no-num no-ref heading settled" id="index-defined-elsewhere"><span class="content">Terms defined by reference</span><a class="self-link" href="#index-defined-elsewhere"></a></h3>
<ul class="index">
<li>
<a data-link-type="biblio">[HTML]</a> defines the following terms:
<ul>
<li><span class="dfn-paneled" id="be0c27b2">Navigator</span>
<li><span class="dfn-paneled" id="a72449dd">in parallel</span>
</ul>
<li>
<a data-link-type="biblio">[INFRA]</a> defines the following terms:
<ul>
<li><span class="dfn-paneled" id="6d19ac93">user agent</span>
</ul>
<li>
<a data-link-type="biblio">[WEBIDL]</a> defines the following terms:
<ul>
<li><span class="dfn-paneled" id="2f8afbfe">ArrayBuffer</span>
<li><span class="dfn-paneled" id="8855a9aa">DOMString</span>
<li><span class="dfn-paneled" id="889e932f">Exposed</span>
<li><span class="dfn-paneled" id="bdbd19d1">Promise</span>
<li><span class="dfn-paneled" id="b75bb3bd">SecureContext</span>
<li><span class="dfn-paneled" id="dacde8b5">a new promise</span>
<li><span class="dfn-paneled" id="cd787c3f">exception</span>
<li><span class="dfn-paneled" id="efd1ec5d">object</span>
<li><span class="dfn-paneled" id="b262501e">reject</span>
<li><span class="dfn-paneled" id="3b90bdcd">resolve</span>
</ul>
</ul>
<h2 class="no-num no-ref heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
<h3 class="no-num no-ref heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
<dl>
<dt id="biblio-html">[HTML]
<dd>Anne van Kesteren; et al. <a href="https://html.spec.whatwg.org/multipage/"><cite>HTML Standard</cite></a>. Living Standard. URL: <a href="https://html.spec.whatwg.org/multipage/">https://html.spec.whatwg.org/multipage/</a>
<dt id="biblio-infra">[INFRA]
<dd>Anne van Kesteren; Domenic Denicola. <a href="https://infra.spec.whatwg.org/"><cite>Infra Standard</cite></a>. Living Standard. URL: <a href="https://infra.spec.whatwg.org/">https://infra.spec.whatwg.org/</a>
<dt id="biblio-rfc2119">[RFC2119]
<dd>S. Bradner. <a href="https://datatracker.ietf.org/doc/html/rfc2119"><cite>Key words for use in RFCs to Indicate Requirement Levels</cite></a>. March 1997. Best Current Practice. URL: <a href="https://datatracker.ietf.org/doc/html/rfc2119">https://datatracker.ietf.org/doc/html/rfc2119</a>
<dt id="biblio-webidl">[WEBIDL]
<dd>Edgar Chen; Timothy Gu. <a href="https://webidl.spec.whatwg.org/"><cite>Web IDL Standard</cite></a>. Living Standard. URL: <a href="https://webidl.spec.whatwg.org/">https://webidl.spec.whatwg.org/</a>
</dl>
<h2 class="no-num no-ref heading settled" id="idl-index"><span class="content">IDL Index</span><a class="self-link" href="#idl-index"></a></h2>
<pre class="idl highlight def"><c- b>interface</c-> <a href="#attesterconnection"><code><c- g>AttesterConnection</c-></code></a> {
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-ArrayBuffer"><c- b>ArrayBuffer</c-></a> <a href="#dom-attesterconnection-getattestation"><code><c- g>getAttestation</c-></code></a>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString"><c- b>DOMString</c-></a> <a href="#dom-attesterconnection-getattestation-contentbinding-contentbinding"><code><c- g>contentBinding</c-></code></a>);
};
[<a class="idl-code" data-link-type="extended-attribute" href="https://webidl.spec.whatwg.org/#Exposed"><c- g>Exposed</c-></a>=<c- n>Window</c->]
<c- b>partial</c-> <c- b>interface</c-> <a class="idl-code" data-link-type="interface" href="https://html.spec.whatwg.org/multipage/system-state.html#navigator"><c- g>Navigator</c-></a> {
[<a class="idl-code" data-link-type="extended-attribute" href="https://webidl.spec.whatwg.org/#SecureContext"><c- g>SecureContext</c-></a>] <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-promise"><c- b>Promise</c-></a>&lt;<a data-link-type="idl-name" href="#environmentintegrity"><c- n>EnvironmentIntegrity</c-></a>> <a class="idl-code" data-link-type="method" href="#dom-navigator-getenvironmentintegrity"><c- g>getEnvironmentIntegrity</c-></a>(<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString"><c- b>DOMString</c-></a> <a href="#dom-navigator-getenvironmentintegrity-contentbinding-contentbinding"><code><c- g>contentBinding</c-></code></a>);
};
<c- b>interface</c-> <a href="#environmentintegrity"><code><c- g>EnvironmentIntegrity</c-></code></a> {
<c- b>readonly</c-> <c- b>attribute</c-> <a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-ArrayBuffer"><c- b>ArrayBuffer</c-></a> <a data-readonly data-type="ArrayBuffer" href="#dom-environmentintegrity-attestationtoken"><code><c- g>attestationToken</c-></code></a>;
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-DOMString"><c- b>DOMString</c-></a> <a href="#dom-environmentintegrity-encode"><code><c- g>encode</c-></code></a>();
<a class="idl-code" data-link-type="interface" href="https://webidl.spec.whatwg.org/#idl-object"><c- b>object</c-></a> <a href="#dom-environmentintegrity-tojson"><code><c- g>toJSON</c-></code></a>();
};
</pre>
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} else {
// 7 classes right now
indexes = [0,0,0,0,0,0,0];
indexCounts.set(algoName, indexes);
}
// If the element was recently unclicked,
// *and* that color is still unclaimed,
// give it back the same color.
const lastIndex = previousHighlightIndex(algoName, varName);
if(indexes[lastIndex] === 0) return lastIndex;
// Find the earliest index with the lowest count.
const minCount = Math.min.apply(null, indexes);
let index = null;
for(var i = 0; i < indexes.length; i++) {
if(indexes[i] == minCount) {
return i;
}
}
}
function previousHighlightIndex(algoName, varName) {
return indexNames.get(algoName+"///"+varName);
}
function nameFromIndex(index) {
return "selected" + index;
}
}
</script>