apt-get's HTTP pipeline desynchronizes, hilarity ensues
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| apt (Ubuntu) |
New
|
Undecided
|
Unassigned | ||
Bug Description
tl;dr: apt-get improperly handles servers which respond 404 with HTTP content to a Range query, resulting in a desychronized HTTP buffer and hilarious bugs.
OK, this is going to be a long one. Where to begin? I was updating my Aptitude packages and noticed that my Dropbox source was not updating correctly:
Err http://
Bad header line
Silly Dropbox, not checking their package list! I report it to them, and they report back that the URL being fetched seems to be giving back a well formed HTTP response, and that they couldn't reproduce. I verify that is the case. We ponder the problem for a while, clearing caches and permuting the source.list line, and finally someone suggests running -o Debug::
Answer for: http://
Package: dropbox
Priority: optional
Section: gnome
Installed-Size: 404
Maintainer: Rian Hunter <email address hidden>
Architecture: amd64
Version: 2.10.0
Replaces: nautilus-dropbox
Provides: nautilus-dropbox
Depends: procps, python-gtk2 (>= 2.12), python (>= 2.5), libatk1.0-0 (>= 1.20.0), libc6 (>= 2.4), libcairo2 (>= 1.6.0), libglib2.0-0 (>= 2.16.0), libgtk2.0-0 (>= 2.12.0), libpango1.0-0 (>= 1.20.1)
Suggests: nautilus (>= 2.16.0), python-gpgme (>= 0.1)
Breaks: nautilus-dropbox
Filename: pool/main/
Size: 94296
MD5sum: 39d2f6558a35def
SHA1: f68b9e102b96a72
SHA256: 5ddf820c1f2e2b1
Description: cloud synchronization engine - CLI and Nautilus extension
Dropbox is a free service that lets you bring your photos, docs, and videos
anywhere and share them easily.
.
This package provides a command-line tool and a Nautilus extension that
integrates the Dropbox web service with your GNOME Desktop.
Homepage: https:/
Err http://
Bad header line
Well. That *sort* of looks reasonable. But I looked around at some of the other responses in the log, and I realized, "Oh shit, these should be HTTP headers!"
Answer for: http://
HTTP/1.1 404 Not Found
Date: Wed, 21 Jan 2015 22:54:17 GMT
Server: Apache
Vary: Accept-Encoding
Content-Length: 227
Content-Type: text/html; charset=iso-8859-1
So, why, then, does Apt think that the content is the HTTP headers? I was reminded of an old bug I encountered in MediaWiki:
https:/
https:/
https:/
Checking the source, it does seem apt pipelines requests by default, so if it desynchronized in its processing of the HTTP stream, that would be bad news. Seeking back in the log, we see this:
Answer for: http://
HTTP/1.1 404 Not Found
Server: nginx
Date: Wed, 21 Jan 2015 22:54:17 GMT
Content-Type: text/html
Content-Length: 162
Connection: keep-alive
Content-Range: bytes */1142
GET /ubuntu/
Host: linux.dropbox.com
Cache-Control: max-age=0
Range: bytes=2635-
If-Range: Mon, 29 Dec 2014 22:30:54 GMT
User-Agent: Debian APT-HTTP/1.3 (1.0.9.2ubuntu2)
Answer for: http://
<html>
<head><title>404 Not Found</
<body bgcolor="white">
<center><h1>404 Not Found</h1></center>
<hr><center>
</body>
</html>
Bingo.
By the way, you won't be able to reproduce the error unless you can induce apt-get to send the If-Range/Range header to the server. apt-get only sends the header if it has some cached partial lists (which, BY THE WAY, are not cleared when you clear your apt cache, WHY?!) I'll attach some files which you can put in /var/lib/
deb [arch=amd64,i386] http://
to your sources list, should cause you to be able to reproduce the error.
For what it's worth, I also think the server is also partially to blame; I'm not sure but 404 doesn't seem like the right code to return here. I'll also attach full HTTP cache logs.
Can forward to upstream on request. (In fact, I'll probably do it anyway.)
ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: apt 1.0.9.2ubuntu2
ProcVersionSign
Uname: Linux 3.16.0-28-generic x86_64
NonfreeKernelMo
ApportVersion: 2.14.7-0ubuntu8.1
Architecture: amd64
Date: Wed Jan 21 15:27:02 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2013-11-21 (426 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
SourcePackage: apt
UpgradeStatus: Upgraded to utopic on 2014-12-04 (48 days ago)
| Edward Z. Yang (ezyang) wrote | #1 |
| Edward Z. Yang (ezyang) wrote | #2 |
| Edward Z. Yang (ezyang) wrote | #3 |
| Edward Z. Yang (ezyang) wrote | #4 |
| Edward Z. Yang (ezyang) wrote | #5 |
| Edward Z. Yang (ezyang) wrote | #6 |
| Edward Z. Yang (ezyang) wrote | #7 |
Oh, apparently you have to set the timestamp on the files sometime before 29 Dec 2014 too, because nginx doesn't spazz unless the if-range is also sent.