Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

security: replace vulnerable regex with parser #1223

Merged
merged 5 commits into from
Apr 17, 2018
Merged

security: replace vulnerable regex with parser #1223

Changes from 4 commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
4717be9
security: replace vulnerable regex with parser
davisjam Apr 15, 2018
1ad9ca0
Travis failure: use backwards-compatible JS
davisjam Apr 15, 2018
fbf93a8
address review comments
davisjam Apr 16, 2018
ba2fc13
address review comments
davisjam Apr 16, 2018
47f4388
address review comments
davisjam Apr 16, 2018
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
69 changes: 66 additions & 3 deletions lib/marked.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -554,9 +554,72 @@ inline.normal = merge({}, inline);
inline.pedantic = merge({}, inline.normal, {
strong: /^__(?=\S)([\s\S]*?\S)__(?!_)|^\*\*(?=\S)([\s\S]*?\S)\*\*(?!\*)/,
em: /^_(?=\S)([\s\S]*?\S)_(?!_)|^\*(?=\S)([\s\S]*?\S)\*(?!\*)/,
link: edit(/^!?\[(label)\]\(\s*<?([\s\S]*?)>?(?:\s+(['"][\s\S]*?['"]))?\s*\)/)
.replace('label', inline._label)
.getRegex(),
/* Original link re: /^!?\[(label)\]\(\s*<?([\s\S]*?)>?(?:\s+(['"][\s\S]*?['"]))?\s*\)/
* This captures the spec reasonably well but is vulnerable to REDOS.
* Instead we use a custom parser that follows the RegExp.exec semantics. */
link: {
exec: function (s) {
Copy link
Member

@joshbruce joshbruce Apr 16, 2018 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Might be worth adding some doc blocks to introduce the why behind some of this...nothing too major, just to help those new to the code.

// [TEXT](DESTINATION)
var generalLinkRe = edit(/^!?\[(label)\]\((.*?)\)/)
.replace('label', inline._label)
.getRegex();

// destination: DESTINATION from generalLinkRe
// returns [destination, title]: no angle-brackets on destination, no quotes on title
function splitIntoDestinationAndTitle (destination) {
function unwrapAngleBrackets (str) {
if (str.match(/^<.*>$/)) {
str = str.slice(1, -1);
}
return str;
}

// Valid DESTINATIONs, in decreasing specificity.
var destinationAndTitleRe = /^([^'"(]*[^\s])\s+(['"(].*['")])/;
var destinationRe = /^(<?[\s\S]*>?)/;
var parsingRegexes = [destinationAndTitleRe, destinationRe];

var match = false;
var dest = undefined;
var title = undefined;
for (var i = 0; i < parsingRegexes.length; i++) {
match = parsingRegexes[i].exec(destination);
if (match) {
dest = match[1];
title = match[2];
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

You don't need to assign dest and title here. Simply use match below.

break;
}
}

if (match) {
Copy link
Member

@styfle styfle Apr 16, 2018 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can you flip this so that the if statement is smaller:

if (!match) {
  return null;
}
// ... get dest and title here
return [dest, title];

// title is optional.
if (typeof title === 'undefined') {
title = '';
}

// Format dest.
dest = dest.trim();
dest = unwrapAngleBrackets(dest);

return [dest, title];
}
return null;
}

var fullMatch = generalLinkRe.exec(s);
if (fullMatch) {
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can you flip this so that the if statement is smaller:

if (!fullMatch) {
  return null;
}
// ... split and such here
return [fullMatch[0], text, destinationAndTitle[0], destinationAndTitle[1]];

var text = fullMatch[1];
var destination = fullMatch[2];

// Does 'destination' match spec?
var destinationAndTitle = splitIntoDestinationAndTitle(destination);
if (destinationAndTitle) {
return [fullMatch[0], text, destinationAndTitle[0], destinationAndTitle[1]];
}
}
return null;
}
},
reflink: edit(/^!?\[(label)\]\s*\[([^\]]*)\]/)
.replace('label', inline._label)
.getRegex()
Expand Down