problem with busybox tar

Denis Vlasenko vda.linux at googlemail.com
Sat Mar 3 19:40:06 UTC 2007 

On Saturday 03 March 2007 13:36, Rogelio Serrano wrote:
> On 3/3/07, Denis Vlasenko <vda.linux at googlemail.com> wrote:
> > On Saturday 03 March 2007 07:35, Rogelio Serrano wrote:
> > > i get an "invalid header checksum error" on some archives that are
> > > fine on gnu tar. both on glibc and uclibc
> >
> > I assume you mean "i get an invalid header checksum error
> > _on untarring_ some archives".
> >
> > > one example is git-1.5.0.tar.bz2
> >
> > URL where it can be downloaded?
> >
> 
> http://kernel.org/pub/software/scm/git/git-1.5.0.tar.bz2

tar tf git-1.5.0.tar works ok up to this chunk:

0033e000  67 69 74 2d 31 2e 35 2e  30 2f 67 69 74 77 65 62  |git-1.5.0/gitweb|
0033e010  2f 74 65 73 74 2f 00 00  00 00 00 00 00 00 00 00  |/test/..........|
0033e020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e060  00 00 00 00 30 30 30 30  37 37 35 00 30 30 30 30  |....0000775.0000|
0033e070  30 30 30 00 30 30 30 30  30 30 30 00 30 30 30 30  |000.0000000.0000|
0033e080  30 30 30 30 30 30 30 00  31 30 35 36 34 34 37 34  |0000000.10564474|
0033e090  30 32 36 00 30 30 31 34  35 35 30 00 35 00 00 00  |026.0014550.5...|
0033e0a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e0b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e0c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e0d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e0e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e0f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e100  00 75 73 74 61 72 00 30  30 72 6f 6f 74 00 00 00  |.ustar.00root...|
0033e110  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e120  00 00 00 00 00 00 00 00  00 72 6f 6f 74 00 00 00  |.........root...|
0033e130  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e140  00 00 00 00 00 00 00 00  00 30 30 30 30 30 30 30  |.........0000000|
0033e150  00 30 30 30 30 30 30 30  00 00 00 00 00 00 00 00  |.0000000........|
0033e160  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e170  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e180  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e190  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e1a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e1b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e1c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e1d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e1e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e1f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

It's ok, and so reported:

git-1.5.0/gitweb/test/

Then it fails in next block (a bit of debug output is included):

nam = 'git-1.5.0/gitweb/test/Mц╓rchen'
sum = 7463
xstr= 6951
str = '0015447'
tar: invalid tar header checksum

The block inself:

0033e200  67 69 74 2d 31 2e 35 2e  30 2f 67 69 74 77 65 62  |git-1.5.0/gitweb|
0033e210  2f 74 65 73 74 2f 4d c3  a4 72 63 68 65 6e 00 00  |/test/M..rchen..|
0033e220  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e230  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e240  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e250  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e260  00 00 00 00 30 30 30 30  36 36 34 00 30 30 30 30  |....0000664.0000|
0033e270  30 30 30 00 30 30 30 30  30 30 30 00 30 30 30 30  |000.0000000.0000|
0033e280  30 30 30 30 30 32 31 00  31 30 35 36 34 34 37 34  |0000021.10564474|
0033e290  30 32 36 00 30 30 31 35  34 34 37 00 30 00 00 00  |026.0015447.0...|
0033e2a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e2b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e2c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e2d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e2e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e2f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e300  00 75 73 74 61 72 00 30  30 72 6f 6f 74 00 00 00  |.ustar.00root...|
0033e310  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e320  00 00 00 00 00 00 00 00  00 72 6f 6f 74 00 00 00  |.........root...|
0033e330  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e340  00 00 00 00 00 00 00 00  00 30 30 30 30 30 30 30  |.........0000000|
0033e350  00 30 30 30 30 30 30 30  00 00 00 00 00 00 00 00  |.0000000........|
0033e360  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e370  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e380  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e390  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e3a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e3b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e3c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e3d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e3e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
0033e3f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

GNU tar doesn't fail here:

...
git-1.5.0/gitweb/test/
git-1.5.0/gitweb/test/Mц╓rchen
git-1.5.0/gitweb/test/file with spaces
git-1.5.0/gitweb/test/file+plus+sign
git-1.5.0/grep.c
...

Hmm wait a second... GNU tar seems to use SIGNED bytes for checksumming!

The fix: archival/libunarchive/get_header_tar.c:

        sum = ' ' * sizeof(tar.chksum);
        for (i = 0; i < 148 ; i++) {
                sum += ((signed char*)&tar)[i]; // <- 'signed' added
        }
        for (i = 156; i < 512 ; i++) {
                sum += ((signed char*)&tar)[i]; // <- 'signed' added
        }

Works for me, will fix in svn now.
--
vda

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