sprinkle a few %q's in the username/password handling to allow for difficult parameters,
my case I have embedded systems which have a nil zero length) password for root in the lab,
and this has to be quoted to make it work.


Reference: /n/sources/patch/applied/ssh-nil-password
Date: Thu Sep 20 12:16:37 CES 2012
Signed-off-by: steve@quintile.net

--- /sys/src/cmd/ssh2/ssh.c	Thu Sep 20 12:15:06 2012
+++ /sys/src/cmd/ssh2/ssh.c	Thu Sep 20 12:15:02 2012
@@ -591,9 +591,9 @@
 
  	if (!nopka) {
 		if (whichkey)
-			n = fprint(cfd1, "ssh-userauth K %s %s", user, whichkey);
+			n = fprint(cfd1, "ssh-userauth K %q %q", user, whichkey);
 		else
-			n = fprint(cfd1, "ssh-userauth K %s", user);
+			n = fprint(cfd1, "ssh-userauth K %q", user);
 		if (n >= 0)
 			return 0;
 	}
@@ -605,13 +605,13 @@
 		fprint(2, "%s: didn't get password: %r\n", argv0);
 		return -1;
 	}
-	n = fprint(cfd1, "ssh-userauth k %s %s", user, up->passwd);
+	n = fprint(cfd1, "ssh-userauth k %q %q", user, up->passwd);
 	if (n >= 0)
 		return 0;
 
 	path[0] = '\0';
 	fd2path(cfd1, path, sizeof path);
-	fprint(2, "%s: auth ctl msg `ssh-userauth k %s <password>' for %s: %r\n",
+	fprint(2, "%s: auth ctl msg `ssh-userauth k %q <password>' for %q: %r\n",
 		argv0, user, path);
 	return -1;
 }