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// Copyright 2016 Cong Ding
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package stun
import (
"encoding/binary"
"hash/crc32"
"net"
)
type attribute struct {
types uint16
length uint16
value []byte
}
func newAttribute(types uint16, value []byte) *attribute {
att := new(attribute)
att.types = types
att.value = padding(value)
att.length = uint16(len(att.value))
return att
}
func newFingerprintAttribute(packet *packet) *attribute {
crc := crc32.ChecksumIEEE(packet.bytes()) ^ fingerprint
buf := make([]byte, 4)
binary.BigEndian.PutUint32(buf, crc)
return newAttribute(attributeFingerprint, buf)
}
func newSoftwareAttribute(name string) *attribute {
return newAttribute(attributeSoftware, []byte(name))
}
func newChangeReqAttribute(changeIP bool, changePort bool) *attribute {
value := make([]byte, 4)
if changeIP {
value[3] |= 0x04
}
if changePort {
value[3] |= 0x02
}
return newAttribute(attributeChangeRequest, value)
}
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |x x x x x x x x| Family | X-Port |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | X-Address (Variable)
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//
// Figure 6: Format of XOR-MAPPED-ADDRESS Attribute
func (v *attribute) xorAddr(transID []byte) *Host {
xorIP := make([]byte, 16)
for i := 0; i < len(v.value)-4; i++ {
xorIP[i] = v.value[i+4] ^ transID[i]
}
family := uint16(v.value[1])
port := binary.BigEndian.Uint16(v.value[2:4])
// Truncate if IPv4, otherwise net.IP sometimes renders it as an IPv6 address.
if family == attributeFamilyIPv4 {
xorIP = xorIP[:4]
}
x := binary.BigEndian.Uint16(transID[:2])
return &Host{family, net.IP(xorIP).String(), port ^ x}
}
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |0 0 0 0 0 0 0 0| Family | Port |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// | Address (32 bits or 128 bits) |
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//
// Figure 5: Format of MAPPED-ADDRESS Attribute
func (v *attribute) rawAddr() *Host {
host := new(Host)
host.family = uint16(v.value[1])
host.port = binary.BigEndian.Uint16(v.value[2:4])
// Truncate if IPv4, otherwise net.IP sometimes renders it as an IPv6 address.
if host.family == attributeFamilyIPv4 {
v.value = v.value[:8]
}
host.ip = net.IP(v.value[4:]).String()
return host
}
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