md5sum -c: ignore a line with a NUL byte among checksum hex digits

* src/md5sum.c (hex_digits): Require that all "digest_hex_bytes"
be hexadecimal digits, not just those before the first NUL byte.
This bug dates back to the original version:
3763a4f24eb21be40674d13ff7b04e078f473e85
* tests/misc/md5sum (nul-in-cksum): Test for the above.
* NEWS [Bug fixes]: Mention this.
Prompted by a report from Flóki Pálsson in
http://bugzilla.redhat.com/439531

1 files changed, 5 insertions, 2 deletions

diff --git a/src/md5sum.c b/src/md5sum.c
index ba762d149..f83a7b115 100644
--- a/src/md5sum.c
+++ b/src/md5sum.c
@@ -343,16 +343,19 @@ split_3 (char *s, size_t s_len,
   return true;
 }
 
+/* Return true if S is a NUL-terminated string of DIGEST_HEX_BYTES hex digits.
+   Otherwise, return false.  */
 static bool
 hex_digits (unsigned char const *s)
 {
-  while (*s)
+  unsigned int i;
+  for (i = 0; i < digest_hex_bytes; i++)
     {
       if (!isxdigit (*s))
         return false;
       ++s;
     }
-  return true;
+  return *s == '\0';
 }
 
 /* An interface to the function, DIGEST_STREAM.