tar segfaults (busybox 1.8.1)

[walter harms]

Tito wrote:
>
> Hi,
> by compiling the latest svn i get this warning:
> 
> CC      archival/tar.o
> archival/tar.c: In function ‘writeFileToTarball’:
> archival/tar.c:183: warning: call to __builtin___strcpy_chk will always overflow destination buffer
>   AR      archival/lib.a
>   LINK    busybox_unstripped
> Trying libraries: crypt m
> Library crypt is needed
> Library m is needed
> Final link with: crypt m
> 
> 
> and after changing the line 183 of tar.c
> 
> -	strcpy(hp->magic, "ustar  ");
> +	strcpy(hp->magic, "ustar");
> 
> there is no segfault due to the fact
> that the size of hp->magic is
> 
> 	char magic[6];            /* 257-262 */
> 
> root at localhost:~/Desktop/busybox#  touch a s d
> root at localhost:~/Desktop/busybox#  ./busybox tar cf test.tar a s d
> root at localhost:~/Desktop/busybox# ls -la test.tar
> -rw-r--r-- 1 root root 2560 2007-11-16 14:15 test.tar
> 
> 
> I cannot say if this fix is correct or if maybe it should be
> done the other way by increasing the size of char magic
> to 8.
> 
> 

hi tito,
this is a classical bug. :)

i  vote for: prevent the next overflow.
strncpy(hp->magic, "ustar",sizeof(hp->magic));

re,
 walter