Bug 29877 - TarBuffer cycles forever on some TAR file inputs
Summary: TarBuffer cycles forever on some TAR file inputs
Alias: None
Product: Ant
Classification: Unclassified
Component: Core (show other bugs)
Version: 1.1
Hardware: All All
: P3 normal with 2 votes (vote)
Target Milestone: ---
Assignee: Ant Notifications List
Keywords: PatchAvailable
Depends on:
Reported: 2004-07-01 18:22 UTC by Ray Waldin
Modified: 2008-02-22 12:18 UTC (History)
1 user (show)


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Description Ray Waldin 2004-07-01 18:22:39 UTC
The length of some TAR files are not multiples of a fixed block size, and so
they seem to end abrubtly in the middle of a block.  These files are definitely
in error, but do appear to be somewhat common.  So common, in fact, that the
org.apache.tools.tar.TarBuffer code already attempts to handle these files, but
this attempt results in an infinite cycle when reading the last block on certain
files, such as the TAR file found within this gzip:


The last block is read repeatedly forever as the input buffer is left unclean
and the data found earlier is mistakenly parsed as new TAR entries.  The
following patch fixes this case by zeroing out unread portions of the input
buffer when foreshortened input files are encountered:

(the same patch can also be found:

--- ..\ant-1.6.1\src\main\org\apache\tools\tar\TarBuffer.java	2004-03-09
08:48:00.000000000 -0800
+++ src\org\apache\tools\tar\TarBuffer.java	2004-06-15 16:24:27.992961600 -0700
@@ -25,6 +25,7 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.IOException;
+import java.util.Arrays;
  * The TarBuffer class implements the tar archive concept
@@ -231,6 +232,19 @@
             // Thanks to 'Yohann.Roussel@alcatel.fr' for this fix.
             if (numBytes == -1) {
+                // However, just leaving the unread portion of the buffer dirty
+                // cause problems in some cases.  This problem can be seen when 
+                // processing the TAR file found within this GZIP:
+                //
+                //    
+                //
+                // The solution is to fill the unused portion of the buffer
with zeros.
+                // 
+                //                     - ray@palamida.com
+                Arrays.fill(blockBuffer, offset, bytesNeeded, (byte) 0);
Comment 1 Peter Reilly 2005-01-10 18:13:44 UTC
Committed the patch, (with a small fix to the
paramters to Arrays.fill())
Thanks for the report and the test file.
This will be in the next release of ant.