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Merged
mosajjal merged 2 commits into from
Aug 1, 2025
Merged

ipsec: implement DecodingLayer #117

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d446ac5
ipsec: implement DecodingLayer
smagnani96 May 7, 2025
9a0e7e9
Update layers/ipsec.go
mosajjal Jun 2, 2025
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72 changes: 54 additions & 18 deletions layers/ipsec.go
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Original file line number Diff line number Diff line change
Expand Up @@ -29,29 +29,46 @@ type IPSecAH struct {
func (i *IPSecAH) LayerType() gopacket.LayerType { return LayerTypeIPSecAH }

func decodeIPSecAH(data []byte, p gopacket.PacketBuilder) error {
i := &IPSecAH{}
return decodingLayerDecoder(i, data, p)
}

// DecodeFromBytes takes a byte buffer and decodes
func (i *IPSecAH) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
if len(data) < 12 {
p.SetTruncated()
df.SetTruncated()
return errors.New("IPSec AH packet less than 12 bytes")
}
i := &IPSecAH{
ipv6ExtensionBase: ipv6ExtensionBase{
NextHeader: IPProtocol(data[0]),
HeaderLength: data[1],
},
Reserved: binary.BigEndian.Uint16(data[2:4]),
SPI: binary.BigEndian.Uint32(data[4:8]),
Seq: binary.BigEndian.Uint32(data[8:12]),

i.ipv6ExtensionBase = ipv6ExtensionBase{
NextHeader: IPProtocol(data[0]),
HeaderLength: data[1],
}

i.Reserved = binary.BigEndian.Uint16(data[2:4])
i.SPI = binary.BigEndian.Uint32(data[4:8])
i.Seq = binary.BigEndian.Uint32(data[8:12])

i.ActualLength = (int(i.HeaderLength) + 2) * 4
if len(data) < i.ActualLength {
p.SetTruncated()
df.SetTruncated()
return errors.New("Truncated AH packet < ActualLength")
}
i.AuthenticationData = data[12:i.ActualLength]
i.Contents = data[:i.ActualLength]
i.Payload = data[i.ActualLength:]
p.AddLayer(i)
return p.NextDecoder(i.NextHeader)

return nil
}

// CanDecode returns the layer type this DecodingLayer can decode
func (i *IPSecAH) CanDecode() gopacket.LayerClass {
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return LayerTypeIPSecAH
}

// NextLayerType returns the next layer we should see after IPSecAH
func (i *IPSecAH) NextLayerType() gopacket.LayerType {
return i.NextHeader.LayerType()
}

// IPSecESP is the encapsulating security payload defined in
Expand All @@ -67,12 +84,31 @@ type IPSecESP struct {
func (i *IPSecESP) LayerType() gopacket.LayerType { return LayerTypeIPSecESP }

func decodeIPSecESP(data []byte, p gopacket.PacketBuilder) error {
i := &IPSecESP{
BaseLayer: BaseLayer{data, nil},
SPI: binary.BigEndian.Uint32(data[:4]),
Seq: binary.BigEndian.Uint32(data[4:8]),
Encrypted: data[8:],
i := &IPSecESP{}
return decodingLayerDecoder(i, data, p)
}

// DecodeFromBytes takes a byte buffer and decodes
func (i *IPSecESP) DecodeFromBytes(data []byte, df gopacket.DecodeFeedback) error {
if len(data) < 8 {
df.SetTruncated()
return errors.New("IPSec ESP packet less than 8 bytes")
}
p.AddLayer(i)

i.BaseLayer = BaseLayer{data, nil}
i.SPI = binary.BigEndian.Uint32(data[:4])
i.Seq = binary.BigEndian.Uint32(data[4:8])
i.Encrypted = data[8:]

return nil
}

// CanDecode returns the layer type this DecodingLayer can decode
func (i *IPSecESP) CanDecode() gopacket.LayerClass {
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return LayerTypeIPSecESP
}

// NextLayerType retuns the next layer we should see after IPSecESP
func (i *IPSecESP) NextLayerType() gopacket.LayerType {
return gopacket.LayerTypePayload
}
8 changes: 8 additions & 0 deletions layers/ipsec_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,10 @@ func BenchmarkDecodePacketIPSecAHTunnel(b *testing.B) {
}
}

func TestIPSecAHAsDecodingLayer(t *testing.T) {
_ = gopacket.NewDecodingLayerParser(LayerTypeIPSecAH, &IPSecAH{})
}

// testPacketIPSecESP is the packet:
//
// 04:30:37.629376 IP 190.0.0.1 > 190.0.0.2: ESP(spi=0x0000006e,seq=0x13), length 116
Expand Down Expand Up @@ -156,3 +160,7 @@ func BenchmarkDecodePacketIPSecESP(b *testing.B) {
gopacket.NewPacket(testPacketIPSecESP, LinkTypeEthernet, gopacket.NoCopy)
}
}

func TestIPSecESPAsDecodingLayer(t *testing.T) {
_ = gopacket.NewDecodingLayerParser(LayerTypeIPSecESP, &IPSecESP{})
}