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