[src/trunk]: src/sys/netinet6 Move the address checks into one function, ip6_...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/a6985b1e86e4
branches:  trunk
changeset: 832004:a6985b1e86e4
user:      maxv <maxv%NetBSD.org@localhost>
date:      Thu Apr 26 07:01:38 2018 +0000

description:
Move the address checks into one function, ip6_badaddr(). In this function,
reinstate the "IPv4-compatible IPv6 addresses" check; these addresses are
deprecated by RFC4291 (2006).

diffstat:

 sys/netinet6/ip6_input.c |  86 ++++++++++++++++++++++-------------------------
 1 files changed, 41 insertions(+), 45 deletions(-)

diffs (127 lines):

diff -r 3a9312c44967 -r a6985b1e86e4 sys/netinet6/ip6_input.c
--- a/sys/netinet6/ip6_input.c  Thu Apr 26 06:23:33 2018 +0000
+++ b/sys/netinet6/ip6_input.c  Thu Apr 26 07:01:38 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ip6_input.c,v 1.198 2018/04/15 08:31:18 maxv Exp $     */
+/*     $NetBSD: ip6_input.c,v 1.199 2018/04/26 07:01:38 maxv Exp $     */
 /*     $KAME: ip6_input.c,v 1.188 2001/03/29 05:34:31 itojun Exp $     */
 
 /*
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ip6_input.c,v 1.198 2018/04/15 08:31:18 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip6_input.c,v 1.199 2018/04/26 07:01:38 maxv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_gateway.h"
@@ -138,6 +138,7 @@
 
 static void ip6_init2(void);
 static void ip6intr(void *);
+static bool ip6_badaddr(struct ip6_hdr *);
 static struct m_tag *ip6_setdstifaddr(struct mbuf *, const struct in6_ifaddr *);
 
 static int ip6_process_hopopts(struct mbuf *, u_int8_t *, int, u_int32_t *,
@@ -320,55 +321,13 @@
                goto bad;
        }
 
-       /*
-        * Check against address spoofing/corruption.
-        */
-       if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src) ||
-           IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
-               /*
-                * XXX: "badscope" is not very suitable for a multicast source.
-                */
+       if (ip6_badaddr(ip6)) {
                IP6_STATINC(IP6_STAT_BADSCOPE);
                in6_ifstat_inc(rcvif, ifs6_in_addrerr);
                goto bad;
        }
 
        /*
-        * The following check is not documented in specs.  A malicious
-        * party may be able to use IPv4 mapped addr to confuse tcp/udp stack
-        * and bypass security checks (act as if it was from 127.0.0.1 by using
-        * IPv6 src ::ffff:127.0.0.1).  Be cautious.
-        *
-        * This check chokes if we are in an SIIT cloud.  As none of BSDs
-        * support IPv4-less kernel compilation, we cannot support SIIT
-        * environment at all.  So, it makes more sense for us to reject any
-        * malicious packets for non-SIIT environment, than try to do a
-        * partial support for SIIT environment.
-        */
-       if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
-           IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
-               IP6_STATINC(IP6_STAT_BADSCOPE);
-               in6_ifstat_inc(rcvif, ifs6_in_addrerr);
-               goto bad;
-       }
-
-#if 0
-       /*
-        * Reject packets with IPv4 compatible addresses (auto tunnel).
-        *
-        * The code forbids auto tunnel relay case in RFC1933 (the check is
-        * stronger than RFC1933).  We may want to re-enable it if mech-xx
-        * is revised to forbid relaying case.
-        */
-       if (IN6_IS_ADDR_V4COMPAT(&ip6->ip6_src) ||
-           IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
-               IP6_STATINC(IP6_STAT_BADSCOPE);
-               in6_ifstat_inc(rcvif, ifs6_in_addrerr);
-               goto bad;
-       }
-#endif
-
-       /*
         * Assume that we can create a fast-forward IP flow entry
         * based on this packet.
         */
@@ -804,6 +763,43 @@
        return;
 }
 
+static bool
+ip6_badaddr(struct ip6_hdr *ip6)
+{
+       /* Check against address spoofing/corruption. */
+       if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_src) ||
+           IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_dst)) {
+               return true;
+       }
+
+       /*
+        * The following check is not documented in specs.  A malicious
+        * party may be able to use IPv4 mapped addr to confuse tcp/udp stack
+        * and bypass security checks (act as if it was from 127.0.0.1 by using
+        * IPv6 src ::ffff:127.0.0.1).  Be cautious.
+        *
+        * This check chokes if we are in an SIIT cloud.  As none of BSDs
+        * support IPv4-less kernel compilation, we cannot support SIIT
+        * environment at all.  So, it makes more sense for us to reject any
+        * malicious packets for non-SIIT environment, than try to do a
+        * partial support for SIIT environment.
+        */
+       if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
+           IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
+               return true;
+       }
+
+       /*
+        * Reject packets with IPv4-compatible IPv6 addresses (RFC4291).
+        */
+       if (IN6_IS_ADDR_V4COMPAT(&ip6->ip6_src) ||
+           IN6_IS_ADDR_V4COMPAT(&ip6->ip6_dst)) {
+               return true;
+       }
+
+       return false;
+}
+
 /*
  * set/grab in6_ifaddr correspond to IPv6 destination address.
  */