disallow empty incoming filename or ones that refer to the current

directory; based on report/patch from Harry Sintonen

usr.bin/ssh/scp.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: scp.c,v 1.197 2018/06/01 04:31:48 dtucker Exp $ */
+/* $OpenBSD: scp.c,v 1.198 2018/11/16 03:03:10 djm Exp $ */
 /*
  * scp - secure remote copy.  This is basically patched BSD rcp which
  * uses ssh to do the data transfer (instead of using rcmd).
@@ -1083,7 +1083,8 @@ sink(int argc, char **argv)
 			SCREWUP("size out of range");
 		size = (off_t)ull;
 
-		if ((strchr(cp, '/') != NULL) || (strcmp(cp, "..") == 0)) {
+		if (*cp == '\0' || strchr(cp, '/') != NULL ||
+		    strcmp(cp, ".") == 0 || strcmp(cp, "..") == 0) {
 			run_err("error: unexpected filename: %s", cp);
 			exit(1);
 		}