b2sum: fix UAR with --check with malformed checksum lines

* src/digest.c (split_3): Reinstate the check for whitespace after the
digest portion of the line, so that we exit early before inspecting
the file name which would be outside the passed buffer in the case
where the input does not contain a newline.
* tests/cksum/b2sum.sh: Add a test case.
* NEWS: Mention the bug fix.
* THANKS.in: Add Frank Busse who has reported multiple bugs using KLEE.
Fixes https://bugs.gnu.org/64229

NEWS

@@ -8,6 +8,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   fail on files with inode numbers that do not fit into 32 bits.
   [This bug was present in "the beginning".]
 
+  'b2sum --check' will no longer read unallocated memory when
+  presented with malformed checksum lines.
+  [bug introduced in coreutils-9.2]
+
   'cp --parents' again succeeds when preserving mode for absolute directories.
   Previously it would have failed with a "No such file or directory" error.
   [bug introduced in coreutils-9.1]

THANKS.in

@@ -211,6 +211,7 @@ Francesco Montorsi                  fr_m@hotmail.com
 François Pinard                     pinard@iro.umontreal.ca
 François Rigault                    rigault.francois@gmail.com
 Frank Adler                         fadler@allesklar.de
+Frank Busse                         f.busse@imperial.ac.uk
 Frank T Lofaro                      ftlofaro@snooks.Egr.UNLV.EDU
 Fred Fish                           fnf@ninemoons.com
 Frédéric L. W. Meunier              0@pervalidus.net

src/digest.c

@@ -862,6 +862,10 @@ split_3 (char *s, size_t s_len,
   while (s[i] && !ISWHITE (s[i]))
     i++;
 
+  /* The digest must be followed by at least one whitespace character.  */
+  if (i == s_len)
+    return false;
+
   *d_len = &s[i] - (char *) *digest;
   s[i++] = '\0';
 

tests/cksum/b2sum.sh

@@ -61,6 +61,11 @@ printf '%s\n' 'BLAKE2' 'BLAKE2b' 'BLAKE2-' 'BLAKE2(' 'BLAKE2 (' > crash.check \
   || framework_failure_
 returns_ 1 $prog -c crash.check || fail=1
 
+# This would read unallocated memory from coreutils-9.2 to coreutils-9.3
+# which would trigger with ASAN or valgrind
+printf '0A0BA0' > overflow.check || framework_failure_
+returns_ 1 $prog -c overflow.check || fail=1
+
 done
 
 Exit $fail