[PATCH] TarBuffer cycles forever on some TAR inputs

[Ray Waldin]

Some TAR files do not adhere to 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.  The 
org.apache.tools.tar.TarBuffer code does attempt 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:

   
http://prdownloads.sourceforge.net/amphetadesk/amphetadesk-src-v0.93.tar.gz

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 attached patch fixes this case by zeroing out unread 
portions of the input buffer when foreshortened input files are encountered.

-Ray
--- ..\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 '[EMAIL PROTECTED]' for this fix.
             //
             if (numBytes == -1) {
+
+                // However, just leaving the unread portion of the buffer 
dirty does 
+                // cause problems in some cases.  This problem can be seen 
when 
+                // processing the TAR file found within this GZIP:
+                //
+                //     
http://prdownloads.sourceforge.net/amphetadesk/amphetadesk-src-v0.93.tar.gz
+                //
+                // The solution is to fill the unused portion of the buffer 
with zeros.
+                // 
+                //                     - [EMAIL PROTECTED]
+
+                Arrays.fill(blockBuffer, offset, bytesNeeded, (byte) 0);
+
                 break;
             }
 
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