Re: [Bug-tar] 'BZh[1-9]' file in v7 format archive confuses GNU tar

[Sergey Poznyakoff]

Michał Górny <address@hidden> ha escrit:

> FWICS the problem is that one of the checksum variants evaluates to zero
> and tar is rather lax on accepting null checksum string (with trailing
> garbage) as zero.

That's easy to fix (see the attached patch). I'm not quite convinced
that it doesn't break backward compatibility though (can such headers be
found in some old archives?)

Regards,
Sergey

diff --git a/src/buffer.c b/src/buffer.c
index ddb63cc..5632aee 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -406,10 +406,6 @@ check_compressed_archive (bool *pshort)
   read_full_records = sfr;
 
   if (record_start != record_end /* no files smaller than BLOCKSIZE */
-      && (strcmp (record_start->header.magic, TMAGIC) == 0
-          || strcmp (record_start->buffer + offsetof (struct posix_header,
-                                                      magic),
-                     OLDGNU_MAGIC) == 0)
       && tar_checksum (record_start, true) == HEADER_SUCCESS)
     /* Probably a valid header */
     return ct_tar;
diff --git a/src/list.c b/src/list.c
index ba9c306..0dacbb7 100644
--- a/src/list.c
+++ b/src/list.c
@@ -892,6 +892,11 @@ from_header (char const *where0, size_t digs, char const 
*type,
        value = -value;
     }
 
+  /* Skip consecutive \0's. This ensures the test below will catch eventual
+     trailing garbage */
+  while (where < lim && !*where)
+    where++;
+
   if (where != lim && *where && !isspace ((unsigned char) *where))
     {
       if (type)