Use an HTML5 compliant parser that interprets HTML as a browser would to parse
the Markdown result and then sanitize based on the result.
Escape unrecognized and disallowed HTML in the result.
Currently works with a hard coded whitelist of safe HTML tags and attributes.
Fixing:
55cd82008e
This commit introduced a html tag whitelist which does not include any table tags (<td>,<tr>,<thead>...). Therefore even tables the markdown parser itself generated will be removed.
Change firstPass() code that checks for fenced code blocks to check all
of them and properly keep track of lastFencedCodeBlockEnd.
This way, it won't misinterpret the end of a fenced code block as a
beginning of a new one.
The issue is that when there are more than 1 fenced code blocks with a
blank line before and after, the parser introduces a single extra new
line to all the fenced code blocks except the last one.
If autolink encounters a link which already has an escaped html entity,
it would escape the ampersand again, producing things like these:
& --> &amp;
" --> &quot;
This commit solves that by first looking for all entity-looking things
in the link and copying those ranges verbatim, only considering the rest
of the string for escaping.
Doesn't seem to have considerable performance impact.
The mailto: links are processed the old way.
This gives a ~10% slowdown of a full test run, which is tolerable.
Switch statement is still slightly slower (~5%). Using map turned out to
be unacceptably slow (~3x slowdown).
When the source Markdown contains an anchor tag with URL as link text
(i.e. <a href=...>http://foo.bar</a>), autolink converts that link text
into another anchor tag, which is nonsense. Detect this situation with
regexp and early exit autolink processing.
This drops the naive approach at <script> tag stripping and resorts to
full sanitization of html. The general idea (and the regexps) is grabbed
from Stack Exchange's PageDown JavaScript Markdown processor[1]. Like in
PageDown, it's implemented as a separate pass over resulting html.
Includes a metric ton (but not all) of test cases from here[2]. Several
are commented out since they don't pass yet.
Stronger (but still incomplete) fix for #11.
[1] http://code.google.com/p/pagedown/wiki/PageDown
[2] https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet
