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-rw-r--r--pkg/tcpip/network/ip_test.go9
-rw-r--r--pkg/tcpip/network/ipv4/ipv4.go26
-rw-r--r--pkg/tcpip/network/ipv4/ipv4_test.go18
3 files changed, 52 insertions, 1 deletions
diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go
index c1848a19c..f20b94d97 100644
--- a/pkg/tcpip/network/ip_test.go
+++ b/pkg/tcpip/network/ip_test.go
@@ -322,6 +322,7 @@ func TestSourceAddressValidation(t *testing.T) {
SrcAddr: src,
DstAddr: localIPv4Addr,
})
+ ip.SetChecksum(^ip.CalculateChecksum())
e.InjectInbound(header.IPv4ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
Data: hdr.View().ToVectorisedView(),
@@ -344,7 +345,6 @@ func TestSourceAddressValidation(t *testing.T) {
SrcAddr: src,
DstAddr: localIPv6Addr,
})
-
e.InjectInbound(header.IPv6ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
Data: hdr.View().ToVectorisedView(),
}))
@@ -581,6 +581,7 @@ func TestIPv4Receive(t *testing.T) {
SrcAddr: remoteIPv4Addr,
DstAddr: localIPv4Addr,
})
+ ip.SetChecksum(^ip.CalculateChecksum())
// Make payload be non-zero.
for i := header.IPv4MinimumSize; i < totalLen; i++ {
@@ -662,6 +663,7 @@ func TestIPv4ReceiveControl(t *testing.T) {
SrcAddr: "\x0a\x00\x00\xbb",
DstAddr: localIPv4Addr,
})
+ ip.SetChecksum(^ip.CalculateChecksum())
// Create the ICMP header.
icmp := header.ICMPv4(view[header.IPv4MinimumSize:])
@@ -681,6 +683,7 @@ func TestIPv4ReceiveControl(t *testing.T) {
SrcAddr: localIPv4Addr,
DstAddr: remoteIPv4Addr,
})
+ ip.SetChecksum(^ip.CalculateChecksum())
// Make payload be non-zero.
for i := dataOffset; i < len(view); i++ {
@@ -734,6 +737,8 @@ func TestIPv4FragmentationReceive(t *testing.T) {
SrcAddr: remoteIPv4Addr,
DstAddr: localIPv4Addr,
})
+ ip1.SetChecksum(^ip1.CalculateChecksum())
+
// Make payload be non-zero.
for i := header.IPv4MinimumSize; i < totalLen; i++ {
frag1[i] = uint8(i)
@@ -750,6 +755,8 @@ func TestIPv4FragmentationReceive(t *testing.T) {
SrcAddr: remoteIPv4Addr,
DstAddr: localIPv4Addr,
})
+ ip2.SetChecksum(^ip2.CalculateChecksum())
+
// Make payload be non-zero.
for i := header.IPv4MinimumSize; i < totalLen; i++ {
frag2[i] = uint8(i)
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index 743aa0575..e7c58ae0a 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -440,6 +440,32 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) {
return
}
+ // There has been some confusion regarding verifying checksums. We need
+ // just look for negative 0 (0xffff) as the checksum, as it's not possible to
+ // get positive 0 (0) for the checksum. Some bad implementations could get it
+ // when doing entry replacement in the early days of the Internet,
+ // however the lore that one needs to check for both persists.
+ //
+ // RFC 1624 section 1 describes the source of this confusion as:
+ // [the partial recalculation method described in RFC 1071] computes a
+ // result for certain cases that differs from the one obtained from
+ // scratch (one's complement of one's complement sum of the original
+ // fields).
+ //
+ // However RFC 1624 section 5 clarifies that if using the verification method
+ // "recommended by RFC 1071, it does not matter if an intermediate system
+ // generated a -0 instead of +0".
+ //
+ // RFC1071 page 1 specifies the verification method as:
+ // (3) To check a checksum, the 1's complement sum is computed over the
+ // same set of octets, including the checksum field. If the result
+ // is all 1 bits (-0 in 1's complement arithmetic), the check
+ // succeeds.
+ if h.CalculateChecksum() != 0xffff {
+ r.Stats().IP.MalformedPacketsReceived.Increment()
+ return
+ }
+
// As per RFC 1122 section 3.2.1.3:
// When a host sends any datagram, the IP source address MUST
// be one of its own IP addresses (but not a broadcast or
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index 16c36707d..fee11bb38 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -120,6 +120,7 @@ func TestIPv4Sanity(t *testing.T) {
tests := []struct {
name string
headerLength uint8 // value of 0 means "use correct size"
+ badHeaderChecksum bool
maxTotalLength uint16
transportProtocol uint8
TTL uint8
@@ -135,6 +136,14 @@ func TestIPv4Sanity(t *testing.T) {
transportProtocol: uint8(header.ICMPv4ProtocolNumber),
TTL: ttl,
},
+ {
+ name: "bad header checksum",
+ maxTotalLength: defaultMTU,
+ transportProtocol: uint8(header.ICMPv4ProtocolNumber),
+ TTL: ttl,
+ badHeaderChecksum: true,
+ shouldFail: true,
+ },
// The TTL tests check that we are not rejecting an incoming packet
// with a zero or one TTL, which has been a point of confusion in the
// past as RFC 791 says: "If this field contains the value zero, then the
@@ -290,6 +299,12 @@ func TestIPv4Sanity(t *testing.T) {
if test.headerLength != 0 {
ip.SetHeaderLength(test.headerLength)
}
+ ip.SetChecksum(0)
+ ipHeaderChecksum := ip.CalculateChecksum()
+ if test.badHeaderChecksum {
+ ipHeaderChecksum += 42
+ }
+ ip.SetChecksum(^ipHeaderChecksum)
requestPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
Data: hdr.View().ToVectorisedView(),
})
@@ -1427,6 +1442,7 @@ func TestReceiveFragments(t *testing.T) {
SrcAddr: frag.srcAddr,
DstAddr: frag.dstAddr,
})
+ ip.SetChecksum(^ip.CalculateChecksum())
vv := hdr.View().ToVectorisedView()
vv.AppendView(frag.payload)
@@ -1695,6 +1711,7 @@ func TestPacketQueing(t *testing.T) {
SrcAddr: host2IPv4Addr.AddressWithPrefix.Address,
DstAddr: host1IPv4Addr.AddressWithPrefix.Address,
})
+ ip.SetChecksum(^ip.CalculateChecksum())
e.InjectInbound(ipv4.ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
Data: hdr.View().ToVectorisedView(),
}))
@@ -1738,6 +1755,7 @@ func TestPacketQueing(t *testing.T) {
SrcAddr: host2IPv4Addr.AddressWithPrefix.Address,
DstAddr: host1IPv4Addr.AddressWithPrefix.Address,
})
+ ip.SetChecksum(^ip.CalculateChecksum())
e.InjectInbound(header.IPv4ProtocolNumber, stack.NewPacketBuffer(stack.PacketBufferOptions{
Data: hdr.View().ToVectorisedView(),
}))
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-26 20:03:14 +0000