Bug#168443: md5sum -c and unexpected inputs

[Richard Kettlewell <rjk@greenend.org.uk>]

> Dpkg's md5sum segfault if presented an invalid file with -c:

Also, it fails in strange and misleading ways if you give it a file in
a subtly different format from that expected.  For instance:

  rjk@rollercoaster:~/junk$ cat md5sums
  cd7fd662dfd566d2e909b09a15047342 *exp.tar.gz
  f3d0724b37006a9f714e419055fa885b *all-tag-versions
  f409221a22823d5fd045855179fdb192 *build-info
  end
  rjk@rollercoaster:~/junk$ /usr/bin/md5sum -c <md5sums
  /usr/bin/md5sum: can't open build-inf

The textutils md5sum, however, works fine with this input:

  rjk@rollercoaster:~/junk$ /usr/bin/md5sum.textutils -c <md5sums
  exp.tar.gz: OK
  all-tag-versions: OK
  build-info: OK

Anyway, the patch below works for me.

  rjk@rollercoaster:~/junk$ ~/3rd/dpkg-1.9.21/build/utils/md5sum -c < md5sums
  rjk@rollercoaster:~/junk$ echo $?
  0

It also produces more graceful behaviour in the case reported by the
original submitter:

  rjk@rollercoaster:~/junk$ ~/3rd/dpkg-1.9.21/build/utils/md5sum  -c < /bin/ls
  /home/rjk/3rd/dpkg-1.9.21/build/utils/md5sum: unterminated or too-long line
  rjk@rollercoaster:~/junk$ echo $?
  1

ttfn/rjk

--- utils/md5sum.c.orig	Wed Jan  8 14:00:44 2003
+++ utils/md5sum.c	Wed Jan  8 14:04:26 2003
@@ -206,6 +206,16 @@
 	if (fgets(buf, sizeof(buf), fp) == NULL)
 		return -1;
 
+	if (!strchr(buf, '\n')) {
+		fprintf(stderr, _("%s: unterminated or too-long line\n"),
+			progname);
+		exit(1);
+	}		
+
+	/* must be at least a digest and a separator */
+	if (strlen(p) <= 32)
+		return 0;
+
 	memcpy(digest, p, 32);
 	p += 32;
 	if (*p++ != ' ')