Use OpenBSD's knuth shuffle algorithm of random values from bind to

produce the DNS request ids instead of a simple per-request
arc4random().  This ensure randomness but also satisfies the
non-repeating property we need.

ok deraadt@

diff --git a/usr.sbin/relayd/Makefile b/usr.sbin/relayd/Makefile
index 7bfb74a..3015ba6 100644 (file)
--- a/usr.sbin/relayd/Makefile
+++ b/usr.sbin/relayd/Makefile
@@ -1,10 +1,10 @@
-#      $OpenBSD: Makefile,v 1.17 2008/02/11 10:42:50 reyk Exp $
+#      $OpenBSD: Makefile,v 1.18 2008/07/09 17:16:51 reyk Exp $
 
 PROG=          relayd
 SRCS=          parse.y log.c control.c buffer.c imsg.c ssl.c ssl_privsep.c \
                relayd.c pfe.c pfe_filter.c hce.c relay.c relay_udp.c \
                carp.c check_icmp.c check_tcp.c check_script.c name2id.c \
-               snmp.c
+               snmp.c shuffle.c
 MAN=           relayd.8 relayd.conf.5
 
 LDADD=         -levent -lssl -lcrypto

diff --git a/usr.sbin/relayd/relay.c b/usr.sbin/relayd/relay.c
index 005ca68..c943281 100644 (file)
--- a/usr.sbin/relayd/relay.c
+++ b/usr.sbin/relayd/relay.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: relay.c,v 1.91 2008/07/09 14:57:01 reyk Exp $ */
+/*     $OpenBSD: relay.c,v 1.92 2008/07/09 17:16:51 reyk Exp $ */
 
 /*
  * Copyright (c) 2006, 2007, 2008 Reyk Floeter <reyk@openbsd.org>
@@ -485,6 +485,16 @@ relay_init(void)
                            rlay->rl_dstnhosts, rlay->rl_dsttable->conf.name,
                            rlay->rl_dsttable->conf.check ? "" : " (no check)");
                }
+
+               switch (rlay->rl_proto->type) {
+               case RELAY_PROTO_DNS:
+                       relay_udp_init(rlay);
+                       break;
+               case RELAY_PROTO_TCP:
+               case RELAY_PROTO_HTTP:
+                       /* Use defaults */
+                       break;
+               }
        }
 
        /* Schedule statistics timer */

diff --git a/usr.sbin/relayd/relay_udp.c b/usr.sbin/relayd/relay_udp.c
index a2971a6..71fc4b8 100644 (file)
--- a/usr.sbin/relayd/relay_udp.c
+++ b/usr.sbin/relayd/relay_udp.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: relay_udp.c,v 1.13 2008/07/09 14:57:01 reyk Exp $     */
+/*     $OpenBSD: relay_udp.c,v 1.14 2008/07/09 17:16:51 reyk Exp $     */
 
 /*
  * Copyright (c) 2007, 2008 Reyk Floeter <reyk@openbsd.org>
@@ -54,6 +54,7 @@ extern struct imsgbuf *ibuf_pfe;
 extern int debug;
 
 struct relayd *env = NULL;
+struct shuffle relay_shuffle;
 
 int             relay_udp_socket(struct sockaddr_storage *, in_port_t,
                    struct protocol *);
@@ -72,20 +73,25 @@ int          relay_dns_cmp(struct session *, struct session *);
 void
 relay_udp_privinit(struct relayd *x_env, struct relay *rlay)
 {
-       struct protocol         *proto = rlay->rl_proto;
-
        if (env == NULL)
                env = x_env;
 
        if (rlay->rl_conf.flags & F_SSL)
                fatalx("ssl over udp is not supported");
        rlay->rl_conf.flags |= F_UDP;
+}
+
+void
+relay_udp_init(struct relay *rlay)
+{
+       struct protocol         *proto = rlay->rl_proto;
 
        switch (proto->type) {
        case RELAY_PROTO_DNS:
                proto->validate = relay_dns_validate;
                proto->request = relay_dns_request;
                proto->cmp = relay_dns_cmp;
+               shuffle_init(&relay_shuffle);
                break;
        default:
                fatalx("unsupported udp protocol");
@@ -401,7 +407,7 @@ relay_dns_validate(struct session *con, struct relay *rlay,
                priv = malloc(sizeof(struct relay_dns_priv));
                if (priv == NULL)
                        return (NULL);
-               priv->dp_inkey = arc4random() & 0xffff;
+               priv->dp_inkey = shuffle_generate16(&relay_shuffle);
                priv->dp_outkey = key;
                return ((void *)priv);
        }

diff --git a/usr.sbin/relayd/relayd.h b/usr.sbin/relayd/relayd.h
index b9b81a7..1979e42 100644 (file)
--- a/usr.sbin/relayd/relayd.h
+++ b/usr.sbin/relayd/relayd.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: relayd.h,v 1.105 2008/07/09 14:57:01 reyk Exp $       */
+/*     $OpenBSD: relayd.h,v 1.106 2008/07/09 17:16:51 reyk Exp $       */
 
 /*
  * Copyright (c) 2006, 2007 Pierre-Yves Ritschard <pyr@openbsd.org>
@@ -64,6 +64,12 @@
 #define DPRINTF(x...)  do {} while(0)
 #endif
 
+/* Used for DNS request ID randomization */
+struct shuffle {
+       u_int16_t        id_shuffle[65536];
+       int              isindex;
+};
+
 /* buffer */
 struct buf {
        TAILQ_ENTRY(buf)         entry;
@@ -801,6 +807,7 @@ SPLAY_PROTOTYPE(session_tree, session, se_nodes, relay_session_cmp);
 
 /* relay_udp.c */
 void    relay_udp_privinit(struct relayd *, struct relay *);
+void    relay_udp_init(struct relay *);
 int     relay_udp_bind(struct sockaddr_storage *, in_port_t,
            struct protocol *);
 void    relay_udp_server(int, short, void *);
@@ -871,3 +878,8 @@ void                 pn_ref(u_int16_t);
 void    snmp_init(struct relayd *, struct imsgbuf *);
 int     snmp_sendsock(struct imsgbuf *);
 void    snmp_hosttrap(struct table *, struct host *);
+
+/* shuffle.c */
+void           shuffle_init(struct shuffle *);
+u_int16_t      shuffle_generate16(struct shuffle *);
+

diff --git a/usr.sbin/relayd/shuffle.c b/usr.sbin/relayd/shuffle.c
new file mode 100644 (file)
index 0000000..a6ce822
--- /dev/null
+++ b/usr.sbin/relayd/shuffle.c
@@ -0,0 +1,75 @@
+/*     $OpenBSD: shuffle.c,v 1.1 2008/07/09 17:16:51 reyk Exp $        */
+
+/*
+ * Portions Copyright (C) 2008 Theo de Raadt
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
+ * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
+ * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
+ * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+ * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
+ * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* based on: bind/lib/isc/shuffle.c,v 1.4 2008/07/09 17:07:32 reyk Exp $ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <net/if.h>
+#include <arpa/inet.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <event.h>
+#include <assert.h>
+
+#include <openssl/ssl.h>
+
+#include "relayd.h"
+
+#define VALID_SHUFFLE(x)       (x != NULL)
+
+void
+shuffle_init(struct shuffle *shuffle)
+{
+       int i, i2;
+
+       assert(VALID_SHUFFLE(shuffle));
+
+       shuffle->isindex = 0;
+       /* Initialize using a Knuth shuffle */
+       for (i = 0; i < 65536; ++i) {
+               i2 = arc4random_uniform(i + 1);
+               shuffle->id_shuffle[i] = shuffle->id_shuffle[i2];
+               shuffle->id_shuffle[i2] = i;
+       }
+}
+
+u_int16_t
+shuffle_generate16(struct shuffle *shuffle)
+{
+       u_int32_t si;
+       u_int16_t r;
+       int i, i2;
+
+       assert(VALID_SHUFFLE(shuffle));
+
+       do {
+               si = arc4random();
+               i = shuffle->isindex & 0xFFFF;
+               i2 = (shuffle->isindex - (si & 0x7FFF)) & 0xFFFF;
+               r = shuffle->id_shuffle[i];
+               shuffle->id_shuffle[i] = shuffle->id_shuffle[i2];
+               shuffle->id_shuffle[i2] = r;
+               shuffle->isindex++;
+       } while (r == 0);
+
+       return (r);
+}