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Posted to bugs@httpd.apache.org by bu...@apache.org on 2011/06/09 22:42:22 UTC

DO NOT REPLY [Bug 51350] New: mod_deflate compresses zero length content into an invalid 20 byte body

https://issues.apache.org/bugzilla/show_bug.cgi?id=51350

             Bug #: 51350
           Summary: mod_deflate compresses zero length content into an
                    invalid 20 byte body
           Product: Apache httpd-2
           Version: 2.2.16
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: mod_deflate
        AssignedTo: bugs@httpd.apache.org
        ReportedBy: apache@tibit.com
    Classification: Unclassified


When my web application returns a response with an empty body and Content-Type:
text/plain or text/html, mod_deflate replaces the body with 20 bytes that can't
be decompressed.  I'm guessing this is a gzip header created when trying to
deflate 0 bytes of data.

Wireshark reports "Error: Decompression Failed" on those 20 bytes, and I
believe some browsers choke on them as well.

Unfortunately, since various web frameworks default to a text Content-Type for
empty responses, this means the bad body is pretty common on things like
OPTIONS responses.

I have verified that the Content-Type header field triggers the problem by
writing special-case code to intercept it on 0-byte responses.  Removing that
header field or using an alternative type (e.g. 'application/json') makes the
invalid 20-byte body disappear.

I'm using a stock Ubuntu build of Apache.

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DO NOT REPLY [Bug 51350] mod_deflate compresses zero length content into an invalid 20 byte body

Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=51350

Stefan Fritsch <sf...@sfritsch.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED

--- Comment #3 from Stefan Fritsch <sf...@sfritsch.de> 2012-02-26 17:11:27 UTC ---
fixed in 2.4.1

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DO NOT REPLY [Bug 51350] mod_deflate compresses zero length content into an invalid 20 byte body

Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=51350

Stefan Fritsch <sf...@sfritsch.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |FixedInTrunk

--- Comment #1 from Stefan Fritsch <sf...@sfritsch.de> 2011-07-13 20:39:24 UTC ---
For me (on trunk and 2.2.19), httpd sends "Content-Length: 20" but no body at
all. Is that what you see or do you see those 20 bytes of body data?

In any case, fixed in trunk in r1146418.

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DO NOT REPLY [Bug 51350] mod_deflate compresses zero length content into an invalid 20 byte body

Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=51350

--- Comment #2 from Stefan Fritsch <sf...@sfritsch.de> 2011-07-13 21:11:37 UTC ---
(In reply to comment #1)
> For me (on trunk and 2.2.19), httpd sends "Content-Length: 20" but no body at
> all. Is that what you see or do you see those 20 bytes of body data?

Never mind. I just didn't look correctly.

But skipping compression for zero length files is a valid optimization, anyway.

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