103 lines
2.1 KiB
Go
103 lines
2.1 KiB
Go
package dht
|
|
|
|
import (
|
|
"hash/crc32"
|
|
"net"
|
|
)
|
|
|
|
func maskForIP(ip net.IP) []byte {
|
|
switch {
|
|
case ip.To4() != nil:
|
|
return []byte{0x03, 0x0f, 0x3f, 0xff}
|
|
default:
|
|
return []byte{0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff}
|
|
}
|
|
}
|
|
|
|
// Generate the CRC used to make or validate secure node ID.
|
|
func crcIP(ip net.IP, rand uint8) uint32 {
|
|
if ip4 := ip.To4(); ip4 != nil {
|
|
ip = ip4
|
|
}
|
|
// Copy IP so we can make changes. Go sux at this.
|
|
ip = append(make(net.IP, 0, len(ip)), ip...)
|
|
mask := maskForIP(ip)
|
|
for i := range mask {
|
|
ip[i] &= mask[i]
|
|
}
|
|
r := rand & 7
|
|
ip[0] |= r << 5
|
|
return crc32.Checksum(ip[:len(mask)], crc32.MakeTable(crc32.Castagnoli))
|
|
}
|
|
|
|
// Makes a node ID secure, in-place. The ID is 20 raw bytes.
|
|
// http://www.libtorrent.org/dht_sec.html
|
|
func SecureNodeId(id *[20]byte, ip net.IP) {
|
|
crc := crcIP(ip, id[19])
|
|
id[0] = byte(crc >> 24 & 0xff)
|
|
id[1] = byte(crc >> 16 & 0xff)
|
|
id[2] = byte(crc>>8&0xf8) | id[2]&7
|
|
}
|
|
|
|
// Returns whether the node ID is considered secure. The id is the 20 raw
|
|
// bytes. http://www.libtorrent.org/dht_sec.html
|
|
func NodeIdSecure(id [20]byte, ip net.IP) bool {
|
|
if isLocalNetwork(ip) {
|
|
return true
|
|
}
|
|
if ip4 := ip.To4(); ip4 != nil {
|
|
ip = ip4
|
|
}
|
|
crc := crcIP(ip, id[19])
|
|
if id[0] != byte(crc>>24&0xff) {
|
|
return false
|
|
}
|
|
if id[1] != byte(crc>>16&0xff) {
|
|
return false
|
|
}
|
|
if id[2]&0xf8 != byte(crc>>8&0xf8) {
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
|
|
var (
|
|
classA, classB, classC *net.IPNet
|
|
)
|
|
|
|
func mustParseCIDRIPNet(s string) *net.IPNet {
|
|
_, ret, err := net.ParseCIDR(s)
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
return ret
|
|
}
|
|
|
|
func init() {
|
|
classA = mustParseCIDRIPNet("10.0.0.0/8")
|
|
classB = mustParseCIDRIPNet("172.16.0.0/12")
|
|
classC = mustParseCIDRIPNet("192.168.0.0/16")
|
|
}
|
|
|
|
// Per http://www.libtorrent.org/dht_sec.html#enforcement, the IP is
|
|
// considered a local network address and should be exempted from node ID
|
|
// verification.
|
|
func isLocalNetwork(ip net.IP) bool {
|
|
if classA.Contains(ip) {
|
|
return true
|
|
}
|
|
if classB.Contains(ip) {
|
|
return true
|
|
}
|
|
if classC.Contains(ip) {
|
|
return true
|
|
}
|
|
if ip.IsLinkLocalUnicast() {
|
|
return true
|
|
}
|
|
if ip.IsLoopback() {
|
|
return true
|
|
}
|
|
return false
|
|
}
|