BUG/MEDIUM: h2: report frame bits only for handled types
As part of his GREASE experiments on Chromium, Bence Béky reported in
https://lists.w3.org/Archives/Public/ietf-http-wg/2020JulSep/0202.html
and https://bugs.chromium.org/p/chromium/issues/detail?id=1127060 that
a certain combination of frame type and frame flags was causing an error
on app.slack.com. It turns out that it's haproxy that is causing this
issue because the frame type is wrongly assumed to support padding, the
frame flags indicate padding is present, and the frame is too short for
this, resulting in an error.
The reason why only some frame types are affected is due to the frame
type being used in a bit shift to match against a mask, and where the
5 lower bits of the frame type only are used to compute the frame bit.
If the resulting frame bit matches a DATA, HEADERS or PUSH_PROMISE frame
bit, then padding support is assumed and the test is enforced, resulting
in a PROTOCOL_ERROR or FRAME_SIZE_ERROR depending on the payload size.
We must never match any such bit for unsupported frame types so let's
add a check for this. This must be backported as far as 1.8.
Thanks to Cooper Bethea for providing enough context to help narrow the
issue down and to Bence Béky for creating a simple reproducer.
(cherry picked from commit 3ca2365904062f883751a4099e2eb5e47ecf11b7)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 1ec08a4d48d2a13859063712b86c82db7920e06e)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 06744f6a0d0e9838c91c8ae35b6dbb5c27b670dd)
Signed-off-by: Willy Tarreau <w@1wt.eu>
1 file changed