| From | Sent On | Attachments |
|---|---|---|
| Igor Sysoev | Aug 27, 2011 1:10 am | .ranges |
| Juan Angulo Moreno | Aug 27, 2011 7:03 pm | |
| Maxim Dounin | Aug 28, 2011 1:45 am | |
| Venky Shankar | Aug 28, 2011 2:41 am | |
| Gena Makhomed | Aug 28, 2011 7:18 am | |
| Maxim Dounin | Aug 28, 2011 7:24 am | |
| Maxim Dounin | Aug 28, 2011 9:35 am | |
| Venky Shankar | Aug 28, 2011 9:48 am | |
| Maxim Dounin | Aug 28, 2011 1:21 pm | |
| Gena Makhomed | Aug 28, 2011 1:38 pm | |
| Maxim Dounin | Aug 28, 2011 5:14 pm | |
| Gena Makhomed | Aug 29, 2011 11:30 am | |
| Igor Sysoev | Aug 29, 2011 11:45 am | |
| Jim Ohlstein | Sep 1, 2011 4:59 am |
| Subject: | Re: nginx and Apache killer | |
|---|---|---|
| From: | Venky Shankar (ykne...@gmail.com) | |
| Date: | Aug 28, 2011 2:41:43 am | |
| List: | ru.sysoev.nginx | |
First of all, nginx doesn't favor HEAD requests with compression, so the exact mentioned attack doesn't work against a standalone nginx installation.
Well, with apache; the problem is not really due to the compression module (you can disable compression and still get DoS'ed)
It is with how it handles byte ranges (by ignoring overlapping ranges etc...)
Currently with apache requests like
Range: bytes=0-1,0-2,0-3...................... <nnn-nnn>
OR
Range: bytes=0-0, 1-1, 2-2.................<nnn-nnn>
will not result in merging of the ranges and deliver data for each range. With huge number of those ranges there is a lot of memory consumed.
If you're using nginx in combination with proxying to apache backend, please check your configuration to see if nginx actually passes range requests to the backend:
1) If you're using proxying WITH caching then range requests are not sent to backend and your apache should be safe.
2) If you're NOT using caching then you might be vulnerable to the attack.
In order to mitigate this attack when your installation includes apache behind nginx we recommend you the following:
1. Refer to the above mentioned security advisory CVE-2011-3192 for apache and implement described measures accordingly.
2. Consider using nginx configuration below (in server{} section of configuration). This particular example filters 5 and more ranges in the request:
if ($http_range ~ "(?:\d*\s*-\s*\d*\s*,\s*){5,}") { return 416; }
We'd also like to notify you that for standalone nginx installations we've produced the attached patch. This patch prevents handling malicious range requests at all, instead outputting just the entire file if the total size of all ranges is greater than the expected response.
-- Igor Sysoev
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.ranges