1 files changed, 16 insertions, 20 deletions

diff --git a/src/usr.bin/nc/netcat.c b/src/usr.bin/nc/netcat.c
index 4c3ed4e97f..cfc5a2363b 100644
--- a/src/usr.bin/nc/netcat.c
+++ b/src/usr.bin/nc/netcat.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: netcat.c,v 1.144 2015/11/23 01:23:56 bcook Exp $ */
+/* $OpenBSD: netcat.c,v 1.145 2015/12/07 02:38:54 tb Exp $ */
 /*
  * Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
  * Copyright (c) 2015 Bob Beck.  All rights reserved.
@@ -58,7 +58,6 @@
 #include "atomicio.h"
 
 #define PORT_MAX        65535
-#define PORT_MAX_LEN    6
 #define UNIX_DG_TMP_SOCKET_SIZE 19
 
 #define POLL_STDIN 0
@@ -1289,25 +1288,22 @@ build_ports(char *p)
                         lo = cp;
                 }
 
-                /* Load ports sequentially. */
-                for (cp = lo; cp <= hi; cp++) {
-                        portlist[x] = calloc(1, PORT_MAX_LEN);
-                        if (portlist[x] == NULL)
-                                err(1, NULL);
-                        snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
-                        x++;
-                }
-
-                /* Randomly swap ports. */
+                /*
+                 * Initialize portlist with a random permutation.  Based on
+                 * Knuth, as in ip_randomid() in sys/netinet/ip_id.c.
+                 */
                 if (rflag) {
-                        int y;
-                        char *c;
-
-                        for (x = 0; x <= (hi - lo); x++) {
-                                y = (arc4random() & 0xFFFF) % (hi - lo);
-                                c = portlist[x];
-                                portlist[x] = portlist[y];
-                                portlist[y] = c;
+                        for (x = 0; x <= hi - lo; x++) {
+                                cp = arc4random_uniform(x + 1);
+                                portlist[x] = portlist[cp];
+                                if (asprintf(&portlist[cp], "%d", x + lo) < 0)
+                                        err(1, "asprintf");
+                        }
+                } else { /* Load ports sequentially. */
+                        for (cp = lo; cp <= hi; cp++) {
+                                if (asprintf(&portlist[x], "%d", cp) < 0)
+                                        err(1, "asprintf");
+                                x++;
                         }
                 }
         } else {