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authorKevin Krakauer <krakauer@google.com>2020-02-14 17:19:32 -0800
committerKevin Krakauer <krakauer@google.com>2020-02-26 11:04:00 -0800
commit408979e619c4b5df74503c7a887aaaa06fd0d730 (patch)
tree45c8cae6cad967802f28defd96a72a8f5f308771 /pkg
parentb8f56c79be40d9c75f4e2f279c9d821d1c1c3569 (diff)
iptables: filter by IP address (and range)
Enables commands such as: $ iptables -A INPUT -d 127.0.0.1 -j ACCEPT $ iptables -t nat -A PREROUTING ! -d 127.0.0.1 -j REDIRECT Also adds a bunch of REDIRECT+destination tests.
Diffstat (limited to 'pkg')
-rw-r--r--pkg/abi/linux/netfilter.go28
-rw-r--r--pkg/sentry/socket/netfilter/netfilter.go17
-rw-r--r--pkg/tcpip/iptables/iptables.go28
-rw-r--r--pkg/tcpip/iptables/types.go12
4 files changed, 76 insertions, 9 deletions
diff --git a/pkg/abi/linux/netfilter.go b/pkg/abi/linux/netfilter.go
index bd2e13ba1..aa149afb5 100644
--- a/pkg/abi/linux/netfilter.go
+++ b/pkg/abi/linux/netfilter.go
@@ -158,10 +158,36 @@ type IPTIP struct {
// Flags define matching behavior for the IP header.
Flags uint8
- // InverseFlags invert the meaning of fields in struct IPTIP.
+ // InverseFlags invert the meaning of fields in struct IPTIP. See the
+ // IPT_INV_* flags.
InverseFlags uint8
}
+// Inverts the meaning of the Protocol field. Corresponds to a constant in
+// include/uapi/linux/netfilter/x_tables.h.
+const XT_INV_PROTO = 0x40
+
+// Flags in IPTIP.InverseFlags. Corresponding constants are in
+// include/uapi/linux/netfilter_ipv4/ip_tables.h.
+const (
+ // Invert the meaning of InputInterface.
+ IPT_INV_VIA_IN = 0x01
+ // Invert the meaning of OutputInterface.
+ IPT_INV_VIA_OUT = 0x02
+ // Unclear what this is, as no references to it exist in the kernel.
+ IPT_INV_TOS = 0x04
+ // Invert the meaning of Src.
+ IPT_INV_SRCIP = 0x08
+ // Invert the meaning of Dst.
+ IPT_INV_DSTIP = 0x10
+ // Invert the meaning of the IPT_F_FRAG flag.
+ IPT_INV_FRAG = 0x20
+ // Invert the meaning of the Protocol field.
+ IPT_INV_PROTO = XT_INV_PROTO
+ // Enable all flags.
+ IPT_INV_MASK = 0x7F
+)
+
// SizeOfIPTIP is the size of an IPTIP.
const SizeOfIPTIP = 84
diff --git a/pkg/sentry/socket/netfilter/netfilter.go b/pkg/sentry/socket/netfilter/netfilter.go
index 2ec11f6ac..faa3e892a 100644
--- a/pkg/sentry/socket/netfilter/netfilter.go
+++ b/pkg/sentry/socket/netfilter/netfilter.go
@@ -26,6 +26,7 @@ import (
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/syserr"
"gvisor.dev/gvisor/pkg/tcpip"
+ "gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/pkg/tcpip/iptables"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"gvisor.dev/gvisor/pkg/usermem"
@@ -630,8 +631,14 @@ func filterFromIPTIP(iptip linux.IPTIP) (iptables.IPHeaderFilter, error) {
if containsUnsupportedFields(iptip) {
return iptables.IPHeaderFilter{}, fmt.Errorf("unsupported fields in struct iptip: %+v", iptip)
}
+ if len(iptip.Dst) != header.IPv4AddressSize || len(iptip.DstMask) != header.IPv4AddressSize {
+ return iptables.IPHeaderFilter{}, fmt.Errorf("incorrect length of destination (%d) and/or destination mask (%d) fields", len(iptip.Dst), len(iptip.DstMask))
+ }
return iptables.IPHeaderFilter{
- Protocol: tcpip.TransportProtocolNumber(iptip.Protocol),
+ Protocol: tcpip.TransportProtocolNumber(iptip.Protocol),
+ Dst: tcpip.Address(iptip.Dst[:]),
+ DstMask: tcpip.Address(iptip.DstMask[:]),
+ DstInvert: iptip.InverseFlags&linux.IPT_INV_DSTIP != 0,
}, nil
}
@@ -639,16 +646,16 @@ func containsUnsupportedFields(iptip linux.IPTIP) bool {
// Currently we check that everything except protocol is zeroed.
var emptyInetAddr = linux.InetAddr{}
var emptyInterface = [linux.IFNAMSIZ]byte{}
- return iptip.Dst != emptyInetAddr ||
- iptip.Src != emptyInetAddr ||
+ // Disable any supported inverse flags.
+ inverseMask := uint8(linux.IPT_INV_DSTIP)
+ return iptip.Src != emptyInetAddr ||
iptip.SrcMask != emptyInetAddr ||
- iptip.DstMask != emptyInetAddr ||
iptip.InputInterface != emptyInterface ||
iptip.OutputInterface != emptyInterface ||
iptip.InputInterfaceMask != emptyInterface ||
iptip.OutputInterfaceMask != emptyInterface ||
iptip.Flags != 0 ||
- iptip.InverseFlags != 0
+ iptip.InverseFlags&^inverseMask != 0
}
func validUnderflow(rule iptables.Rule) bool {
diff --git a/pkg/tcpip/iptables/iptables.go b/pkg/tcpip/iptables/iptables.go
index dbaccbb36..262b6448d 100644
--- a/pkg/tcpip/iptables/iptables.go
+++ b/pkg/tcpip/iptables/iptables.go
@@ -240,9 +240,8 @@ func (it *IPTables) checkChain(hook Hook, pkt tcpip.PacketBuffer, table Table, r
func (it *IPTables) checkRule(hook Hook, pkt tcpip.PacketBuffer, table Table, ruleIdx int) (RuleVerdict, int) {
rule := table.Rules[ruleIdx]
- // First check whether the packet matches the IP header filter.
- // TODO(gvisor.dev/issue/170): Support other fields of the filter.
- if rule.Filter.Protocol != 0 && rule.Filter.Protocol != header.IPv4(pkt.NetworkHeader).TransportProtocol() {
+ // Check whether the packet matches the IP header filter.
+ if !filterMatch(rule.Filter, header.IPv4(pkt.NetworkHeader)) {
// Continue on to the next rule.
return RuleJump, ruleIdx + 1
}
@@ -263,3 +262,26 @@ func (it *IPTables) checkRule(hook Hook, pkt tcpip.PacketBuffer, table Table, ru
// All the matchers matched, so run the target.
return rule.Target.Action(pkt)
}
+
+func filterMatch(filter IPHeaderFilter, hdr header.IPv4) bool {
+ // TODO(gvisor.dev/issue/170): Support other fields of the filter.
+ // Check the transport protocol.
+ if filter.Protocol != 0 && filter.Protocol != hdr.TransportProtocol() {
+ return false
+ }
+
+ // Check the destination IP.
+ dest := hdr.DestinationAddress()
+ matches := true
+ for i := range filter.Dst {
+ if dest[i]&filter.DstMask[i] != filter.Dst[i] {
+ matches = false
+ break
+ }
+ }
+ if matches == filter.DstInvert {
+ return false
+ }
+
+ return true
+}
diff --git a/pkg/tcpip/iptables/types.go b/pkg/tcpip/iptables/types.go
index 7d032fd23..e7fcf6bff 100644
--- a/pkg/tcpip/iptables/types.go
+++ b/pkg/tcpip/iptables/types.go
@@ -144,6 +144,18 @@ type Rule struct {
type IPHeaderFilter struct {
// Protocol matches the transport protocol.
Protocol tcpip.TransportProtocolNumber
+
+ // Dst matches the destination IP address.
+ Dst tcpip.Address
+
+ // DstMask masks bits of the destination IP address when comparing with
+ // Dst.
+ DstMask tcpip.Address
+
+ // DstInvert inverts the meaning of the destination IP check, i.e. when
+ // true the filter will match packets that fail the destination
+ // comparison.
+ DstInvert bool
}
// A Matcher is the interface for matching packets.