This commit adds three `.pysa` model files: `false_positives.pysa`
for ruling out false positive flows with `Sanitize` annotations,
`req_lib.pysa` for educating pysa about Zulip's `REQ()` pattern for
extracting user input, and `redirects.pysa` for capturing the risk
of open redirects within Zulip code. Additionally, this commit
introduces `mark_sanitized`, an identity function which can be used
to selectively clear taint in cases where `Sanitize` models will not
work. This commit also puts `mark_sanitized` to work removing known
false postive flows.
Some sites don't render correctly unless you are one of the latest browsers.
YouTube Music, for instance, changes the page title to "Your browser is
deprecated, please upgrade.", which makes our URL previews look bad.
Our open graph parser logic sloppily mixed data obtained by parsing
open graph properties with trusted data set by our oembed parser.
We fix this by consistenly using our explicit whitelist of generic
properties (image, title, and description) in both places where we
interact with open graph properties. The fixes are redundant with
each other, but doing both helps in making the intent of the code
clearer.
This issue fixed here was originally reported as an XSS vulnerability
in the upcoming Inline URL Previews feature found by Graham Bleaney
and Ibrahim Mohamed using Pysa. The recent Oembed changes close that
vulnerability, but this change is still worth doing to make the
implementation do what it looks like it does.
Ensure that the html is safe, before using it. The html is considered if it is
in an iframe with a http/https src, based on the recommendations here:
https://oembed.com/#section3
We directly embed the `iframe` html into the lightbox overlay.
We may be successfully able to get the page once, to get the content type, but
the server or network may go down and cause problems when fetching the page for
parsing its meta tags.
Currently, we only show previews for URLs which are HTML pages, which could
contain other media. We don't show previews for links to non-HTML pages, like
pdf documents or audio/video files. To verify that the URL posted is an HTML
page, we verify the content-type of the page, either using server headers or by
sniffing the content.
Closes#8358
We don't want really long urls to lead to truncated
keys, or we could theoretically have two different
urls get mixed up previews.
Also, this suppresses warnings about exceeding the
250 char limit.
Finally, this gives the key a proper prefix.
This change adds support for displaying inline open graph previews for
links posted into Zulip.
It is designed to interact correctly with message editing.
This adds the new settings.INLINE_URL_EMBED_PREVIEW setting to control
whether this feature is enabled.
By default, this setting is currently disabled, so that we can burn it
in for a bit before it impacts users more broadly.
Eventually, we may want to make this manageable via a (set of?)
per-realm settings. E.g. I can imagine a realm wanting to be able to
enable/disable it for certain URLs.
Graham Bleaney
Puneeth Chaganti
Mateusz Mandera
Tim Abbott
Anders Kaseorg
Anders Kaseorg
Steve Howell
neiljp (Neil Pilgrim)
Aditya Bansal
rht
Mark Shannon
Robert Hönig
Igor Tokarev