archive/zip: CL 6811080 broke the ability to read a zip file

[gopherbot]

by mpvanlohuizen:

What steps will reproduce the problem?
If possible, include a link to a program on play.golang.org.
1. Download attached go and zip file.
2. Run the go program. 
3. It will panic:

What is the expected output?
The expected output is not to panic.

What do you see instead?
panic: zip: not a valid zip file

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
MacOS X 10.8.2

Which version are you using?  (run 'go version')
go version devel +f5c69f87ef34 Mon Nov 12 12:21:00 2012 +0100

Please provide any additional information below.
This bug was introduced with CL 6811080:
archive/zip: Fix bounds check panic for ZIP files with a truncated extra header.
from dave, reviewed by adg.

Attachments:

1. testzip.go (379 bytes)
2. core.zip (5222881 bytes)

[davecheney]

Comment 1:

I'm taking a look now. For the record, the panic comes from the test program, not the
archive/zip package.

[davecheney]

Comment 2:

That zip file contains 13 bytes of extra data, the first 4 bytes, and the following 5
bytes are consumed, leaving 4 bytes unconsumed. This was my fault, I wrote the logic
assuming that you need _more_ than 4 bytes of extra data, but in this case there is a
tag with a 0 length.
zip: tag 30805 size 0
What program created that zip file? Can you possibly recreate the core.zip file
containing only one file, so it can be used as a test file ?

Owner changed to @davecheney.

Status changed to Accepted.

[davecheney]

Comment 3:

http://golang.org/cl/6854058

Labels changed: added priority-soon, removed priority-triage.

[mpvl]

Comment 4:

Yes, sorry, the panic is in the test program.
The zip file was obtained from http://www.unicode.org/Public/cldr/22/core.zip.
I don't know which program they used to create it, but I do know this error does not
occur with most of their zip files, so I'm not sure how easy it would be to reproduce
with a smaller set.

[davecheney]

Comment 5:

It should be fixed in the CL linked above.

[davecheney]

Comment 6:

This issue was closed by revision 7ec76e2.

Status changed to Fixed.