element-web/src/HtmlUtils.js

/*
Copyright 2015, 2016 OpenMarket Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

'use strict';

var React = require('react');
var sanitizeHtml = require('sanitize-html');
var highlight = require('highlight.js');
var linkifyMatrix = require('./linkify-matrix');
import escape from 'lodash/escape';
import emojione from 'emojione';
import classNames from 'classnames';

emojione.imagePathSVG = 'emojione/svg/';
emojione.imageType = 'svg';

const EMOJI_REGEX = new RegExp(emojione.unicodeRegexp+"+", "gi");
const COLOR_REGEX = /^[#a-z0-9]+$/;
const ALLOWED_CSS = {
    "background-color": COLOR_REGEX,
    "color": COLOR_REGEX,
};

/* modified from https://github.com/Ranks/emojione/blob/master/lib/js/emojione.js
 * because we want to include emoji shortnames in title text
 */
export function unicodeToImage(str) {
    let replaceWith, unicode, alt;
    const mappedUnicode = emojione.mapUnicodeToShort();

    str = str.replace(emojione.regUnicode, function(unicodeChar) {
        if ( (typeof unicodeChar === 'undefined') || (unicodeChar === '') || (!(unicodeChar in emojione.jsEscapeMap)) ) {
            // if the unicodeChar doesnt exist just return the entire match
            return unicodeChar;
        }
        else {
            // get the unicode codepoint from the actual char
            unicode = emojione.jsEscapeMap[unicodeChar];

            // depending on the settings, we'll either add the native unicode as the alt tag, otherwise the shortname
            alt = (emojione.unicodeAlt) ? emojione.convert(unicode.toUpperCase()) : mappedUnicode[unicode];
            const title = mappedUnicode[unicode];

            replaceWith = `<img class="mx_emojione" title="${title}" alt="${alt}" src="${emojione.imagePathSVG}${unicode}.svg${emojione.cacheBustParam}"/>`;
            return replaceWith;
        }
    });

    return str;
}

export function stripParagraphs(html: string): string {
    const contentDiv = document.createElement('div');
    contentDiv.innerHTML = html;

    if (contentDiv.children.length === 0) {
        return contentDiv.innerHTML;
    }

    let contentHTML = "";
    for (let i=0; i<contentDiv.children.length; i++) {
        const element = contentDiv.children[i];
        if (element.tagName.toLowerCase() === 'p') {
            contentHTML += element.innerHTML + '<br />';
        } else {
            const temp = document.createElement('div');
            temp.appendChild(element.cloneNode(true));
            contentHTML += temp.innerHTML;
        }
    }

    return contentHTML;
}

var sanitizeHtmlParams = {
    allowedTags: [
        'font', // custom to matrix for IRC-style font coloring
        'del', // for markdown
        // deliberately no h1/h2 to stop people shouting.
        'h3', 'h4', 'h5', 'h6', 'blockquote', 'p', 'a', 'ul', 'ol',
        'nl', 'li', 'b', 'i', 'u', 'strong', 'em', 'strike', 'code', 'hr', 'br', 'div',
        'table', 'thead', 'caption', 'tbody', 'tr', 'th', 'td', 'pre'
    ],
    allowedAttributes: {
        // custom ones first:
        font: ['color', 'style'], // custom to matrix
        a: ['href', 'name', 'target', 'rel'], // remote target: custom to matrix
        // We don't currently allow img itself by default, but this
        // would make sense if we did
        img: ['src'],
    },
    // Lots of these won't come up by default because we don't allow them
    selfClosing: ['img', 'br', 'hr', 'area', 'base', 'basefont', 'input', 'link', 'meta'],
    // URL schemes we permit
    allowedSchemes: ['http', 'https', 'ftp', 'mailto'],

    // DO NOT USE. sanitize-html allows all URL starting with '//'
    // so this will always allow links to whatever scheme the
    // host page is served over.
    allowedSchemesByTag: {},

    transformTags: { // custom to matrix
        // add blank targets to all hyperlinks except vector URLs
        'a': function(tagName, attribs) {
            if (attribs.href) {
                attribs.target = '_blank'; // by default

                var m;
                // FIXME: horrible duplication with linkify-matrix
                m = attribs.href.match(linkifyMatrix.VECTOR_URL_PATTERN);
                if (m) {
                    attribs.href = m[1];
                    delete attribs.target;
                }

                m = attribs.href.match(linkifyMatrix.MATRIXTO_URL_PATTERN);
                if (m) {
                    var entity = m[1];
                    if (entity[0] === '@') {
                        attribs.href = '#/user/' + entity;
                    }
                    else if (entity[0] === '#' || entity[0] === '!') {
                        attribs.href = '#/room/' + entity;
                    }
                    delete attribs.target;
                }
            }
            attribs.rel = 'noopener'; // https://mathiasbynens.github.io/rel-noopener/
            return { tagName: tagName, attribs : attribs };
        },
        '*': function(tagName, attribs) {
            // Only allow certain CSS attributes to avoid XSS attacks
            // Sanitizing values to avoid `url(...)` and `expression(...)` attacks
            if (!attribs.style) {
                return { tagName: tagName, attribs: attribs };
            }

            const pairs = attribs.style.split(';');
            let sanitisedStyle = "";
            for (let i = 0; i < pairs.length; i++) {
                const pair = pairs[i].split(':');
                if (!Object.keys(ALLOWED_CSS).includes(pair[0]) ||
                    !ALLOWED_CSS[pair[0]].test(pair[1])
                ) {
                    continue;
                }
                sanitisedStyle += pair[0] + ":" + pair[1] + ";";
            }

            if (sanitisedStyle) {
                attribs.style = sanitisedStyle;
            } else {
                delete attribs.style;
            }

            return { tagName: tagName, attribs: attribs };
        },
    },
};

class BaseHighlighter {
    constructor(highlightClass, highlightLink) {
        this.highlightClass = highlightClass;
        this.highlightLink = highlightLink;
    }

    /**
     * apply the highlights to a section of text
     *
     * @param {string} safeSnippet The snippet of text to apply the highlights
     *     to.
     * @param {string[]} safeHighlights A list of substrings to highlight,
     *     sorted by descending length.
     *
     * returns a list of results (strings for HtmlHighligher, react nodes for
     * TextHighlighter).
     */
    applyHighlights(safeSnippet, safeHighlights) {
        var lastOffset = 0;
        var offset;
        var nodes = [];

        var safeHighlight = safeHighlights[0];
        while ((offset = safeSnippet.toLowerCase().indexOf(safeHighlight.toLowerCase(), lastOffset)) >= 0) {
            // handle preamble
            if (offset > lastOffset) {
                var subSnippet = safeSnippet.substring(lastOffset, offset);
                nodes = nodes.concat(this._applySubHighlights(subSnippet, safeHighlights));
            }

            // do highlight. use the original string rather than safeHighlight
            // to preserve the original casing.
            var endOffset = offset + safeHighlight.length;
            nodes.push(this._processSnippet(safeSnippet.substring(offset, endOffset), true));

            lastOffset = endOffset;
        }

        // handle postamble
        if (lastOffset !== safeSnippet.length) {
            subSnippet = safeSnippet.substring(lastOffset, undefined);
            nodes = nodes.concat(this._applySubHighlights(subSnippet, safeHighlights));
        }
        return nodes;
    }

    _applySubHighlights(safeSnippet, safeHighlights) {
        if (safeHighlights[1]) {
            // recurse into this range to check for the next set of highlight matches
            return this.applyHighlights(safeSnippet, safeHighlights.slice(1));
        }
        else {
            // no more highlights to be found, just return the unhighlighted string
            return [this._processSnippet(safeSnippet, false)];
        }
    }
}

class HtmlHighlighter extends BaseHighlighter {
    /* highlight the given snippet if required
     *
     * snippet: content of the span; must have been sanitised
     * highlight: true to highlight as a search match
     *
     * returns an HTML string
     */
    _processSnippet(snippet, highlight) {
        if (!highlight) {
            // nothing required here
            return snippet;
        }

        var span = "<span class=\""+this.highlightClass+"\">"
            + snippet + "</span>";

        if (this.highlightLink) {
            span = "<a href=\""+encodeURI(this.highlightLink)+"\">"
                +span+"</a>";
        }
        return span;
    }
}

class TextHighlighter extends BaseHighlighter {
    constructor(highlightClass, highlightLink) {
        super(highlightClass, highlightLink);
        this._key = 0;
    }

    /* create a <span> node to hold the given content
     *
     * snippet: content of the span
     * highlight: true to highlight as a search match
     *
     * returns a React node
     */
    _processSnippet(snippet, highlight) {
        var key = this._key++;

        var node =
            <span key={key} className={highlight ? this.highlightClass : null }>
                { snippet }
            </span>;

        if (highlight && this.highlightLink) {
            node = <a key={key} href={this.highlightLink}>{node}</a>;
        }

        return node;
    }
}


    /* turn a matrix event body into html
     *
     * content: 'content' of the MatrixEvent
     *
     * highlights: optional list of words to highlight, ordered by longest word first
     *
     * opts.highlightLink: optional href to add to highlighted words
     */
export function bodyToHtml(content, highlights, opts) {
    opts = opts || {};

    var isHtml = (content.format === "org.matrix.custom.html");
    let body = isHtml ? content.formatted_body : escape(content.body);

    var safeBody;
    // XXX: We sanitize the HTML whilst also highlighting its text nodes, to avoid accidentally trying
    // to highlight HTML tags themselves.  However, this does mean that we don't highlight textnodes which
    // are interrupted by HTML tags (not that we did before) - e.g. foo<span/>bar won't get highlighted
    // by an attempt to search for 'foobar'.  Then again, the search query probably wouldn't work either
    try {
        if (highlights && highlights.length > 0) {
            var highlighter = new HtmlHighlighter("mx_EventTile_searchHighlight", opts.highlightLink);
            var safeHighlights = highlights.map(function(highlight) {
                return sanitizeHtml(highlight, sanitizeHtmlParams);
            });
            // XXX: hacky bodge to temporarily apply a textFilter to the sanitizeHtmlParams structure.
            sanitizeHtmlParams.textFilter = function(safeText) {
                return highlighter.applyHighlights(safeText, safeHighlights).join('');
            };
        }
        safeBody = sanitizeHtml(body, sanitizeHtmlParams);
        safeBody = unicodeToImage(safeBody);
    }
    finally {
        delete sanitizeHtmlParams.textFilter;
    }

    EMOJI_REGEX.lastIndex = 0;
    let contentBodyTrimmed = content.body !== undefined ? content.body.trim() : '';
    let match = EMOJI_REGEX.exec(contentBodyTrimmed);
    let emojiBody = match && match[0] && match[0].length === contentBodyTrimmed.length;

    const className = classNames({
        'mx_EventTile_body': true,
        'mx_EventTile_bigEmoji': emojiBody,
        'markdown-body': isHtml,
    });
    return <span className={className} dangerouslySetInnerHTML={{ __html: safeBody }} />;
}

export function emojifyText(text) {
    return {
        __html: unicodeToImage(escape(text)),
    };
}