diff options
Diffstat (limited to 'net/netfilter')
| -rw-r--r-- | net/netfilter/nf_nat_core.c | 43 |
1 files changed, 40 insertions, 3 deletions
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c index ab9f6c75524d..3dd130487b5b 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -494,6 +494,38 @@ another_round: goto another_round; } +static bool tuple_force_port_remap(const struct nf_conntrack_tuple *tuple) +{ + u16 sp, dp; + + switch (tuple->dst.protonum) { + case IPPROTO_TCP: + sp = ntohs(tuple->src.u.tcp.port); + dp = ntohs(tuple->dst.u.tcp.port); + break; + case IPPROTO_UDP: + case IPPROTO_UDPLITE: + sp = ntohs(tuple->src.u.udp.port); + dp = ntohs(tuple->dst.u.udp.port); + break; + default: + return false; + } + + /* IANA: System port range: 1-1023, + * user port range: 1024-49151, + * private port range: 49152-65535. + * + * Linux default ephemeral port range is 32768-60999. + * + * Enforce port remapping if sport is significantly lower + * than dport to prevent NAT port shadowing, i.e. + * accidental match of 'new' inbound connection vs. + * existing outbound one. + */ + return sp < 16384 && dp >= 32768; +} + /* Manipulate the tuple into the range given. For NF_INET_POST_ROUTING, * we change the source to map into the range. For NF_INET_PRE_ROUTING * and NF_INET_LOCAL_OUT, we change the destination to map into the @@ -507,11 +539,17 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple, struct nf_conn *ct, enum nf_nat_manip_type maniptype) { + bool random_port = range->flags & NF_NAT_RANGE_PROTO_RANDOM_ALL; const struct nf_conntrack_zone *zone; struct net *net = nf_ct_net(ct); zone = nf_ct_zone(ct); + if (maniptype == NF_NAT_MANIP_SRC && + !random_port && + !ct->local_origin) + random_port = tuple_force_port_remap(orig_tuple); + /* 1) If this srcip/proto/src-proto-part is currently mapped, * and that same mapping gives a unique tuple within the given * range, use that. @@ -520,8 +558,7 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple, * So far, we don't do local source mappings, so multiple * manips not an issue. */ - if (maniptype == NF_NAT_MANIP_SRC && - !(range->flags & NF_NAT_RANGE_PROTO_RANDOM_ALL)) { + if (maniptype == NF_NAT_MANIP_SRC && !random_port) { /* try the original tuple first */ if (in_range(orig_tuple, range)) { if (!nf_nat_used_tuple(orig_tuple, ct)) { @@ -545,7 +582,7 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple, */ /* Only bother mapping if it's not already in range and unique */ - if (!(range->flags & NF_NAT_RANGE_PROTO_RANDOM_ALL)) { + if (!random_port) { if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) { if (!(range->flags & NF_NAT_RANGE_PROTO_OFFSET) && l4proto_in_range(tuple, maniptype, |