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stun: fix IPv6 bug, refactor a bit

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Fixes #104

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2020-02-26 09:19:39 -08:00
parent 6879581891
commit 2489ea4268
2 changed files with 99 additions and 59 deletions
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108
stun/stun.go
View File

@ -6,14 +6,12 @@
package stun
import (
"bytes"
crand "crypto/rand"
"errors"
"hash/crc32"
)
var (
bindingRequest = []byte{0x00, 0x01}
magicCookie = []byte{0x21, 0x12, 0xa4, 0x42}
attrSoftware = append([]byte{
0x80, 0x22, // software header
0x00, byte(len("tailnode")), // attr length
@ -21,13 +19,32 @@
lenMsg = byte(len(attrSoftware) + lenFingerprint) // number of bytes following header
)
const lenFingerprint = 8 // 2+byte header + 2-byte length + 4-byte crc32
const (
bindingRequest = "\x00\x01"
magicCookie = "\x21\x12\xa4\x42"
lenFingerprint = 8 // 2+byte header + 2-byte length + 4-byte crc32
ipv4Len = 4
ipv6Len = 16
headerLen = 20
)
// TxID is a transaction ID.
type TxID [12]byte
// NewTxID returns a new random TxID.
func NewTxID() TxID {
var tx TxID
if _, err := crand.Read(tx[:]); err != nil {
panic(err)
}
return tx
}
// Request generates a binding request STUN packet.
// The transaction ID, tID, should be a random sequence of bytes.
func Request(tID [12]byte) []byte {
func Request(tID TxID) []byte {
// STUN header, RFC5389 Section 6.
b := make([]byte, 0, 20+len(attrSoftware)+lenFingerprint)
b := make([]byte, 0, headerLen+len(attrSoftware)+lenFingerprint)
b = append(b, bindingRequest...)
b = append(b, 0x00, lenMsg)
b = append(b, magicCookie...)
@ -58,16 +75,17 @@ func Request(tID [12]byte) []byte {
// ParseResponse parses a successful binding response STUN packet.
// The IP address is extracted from the XOR-MAPPED-ADDRESS attribute.
func ParseResponse(b []byte) (tID [12]byte, addr []byte, port uint16, err error) {
// The returned addr slice is owned by the caller and does not alias b.
func ParseResponse(b []byte) (tID TxID, addr []byte, port uint16, err error) {
if !Is(b) {
return tID, nil, 0, ErrNotSTUN
}
copy(tID[:], b[8:20])
copy(tID[:], b[8:headerLen])
if b[0] != 0x01 || b[1] != 0x01 {
return tID, nil, 0, ErrNotSuccessResponse
}
attrsLen := int(b[2])<<8 | int(b[3])
b = b[20:] // remove STUN header
b = b[headerLen:] // remove STUN header
if attrsLen > len(b) {
return tID, nil, 0, ErrMalformedAttrs
} else if len(b) > attrsLen {
@ -143,64 +161,66 @@ func ParseResponse(b []byte) (tID [12]byte, addr []byte, port uint16, err error)
return tID, nil, 0, ErrMalformedAttrs
}
func xorMappedAddress(tID [12]byte, b []byte) (addr []byte, port uint16, err error) {
func xorMappedAddress(tID TxID, b []byte) (addr []byte, port uint16, err error) {
// XOR-MAPPED-ADDRESS attribute, RFC5389 Section 15.2
if len(b) < 8 {
if len(b) < 4 {
return nil, 0, ErrMalformedAttrs
}
xorPort := uint16(b[2])<<8 | uint16(b[3])
addrField := b[4:]
port = xorPort ^ 0x2112 // first half of magicCookie
switch ipFamily := b[1]; ipFamily { // RFC5389 Section 15.1
addrLen := familyAddrLen(b[1])
if addrLen == 0 {
return nil, 0, ErrMalformedAttrs
}
if len(addrField) < addrLen {
return nil, 0, ErrMalformedAttrs
}
xorAddr := addrField[:addrLen]
addr = make([]byte, addrLen)
for i := range xorAddr {
if i < len(magicCookie) {
addr[i] = xorAddr[i] ^ magicCookie[i]
} else {
addr[i] = xorAddr[i] ^ tID[i-len(magicCookie)]
}
}
return addr, port, nil
}
func familyAddrLen(fam byte) int {
switch fam {
case 0x01: // IPv4
addr = make([]byte, 4)
xorAddr := b[4 : 4+len(addr)]
for i := range xorAddr {
addr[i] = xorAddr[i] ^ magicCookie[i]
}
return ipv4Len
case 0x02: // IPv6
addr = make([]byte, 16)
xorAddr := b[4 : 4+len(addr)]
for i := range xorAddr {
addr[i] = xorAddr[i] ^ magicCookie[i]
}
for i := 4; i < len(addr); i++ {
addr[i] = xorAddr[i] ^ tID[4-i]
}
return ipv6Len
default:
return nil, 0, ErrMalformedAttrs
return 0
}
if len(b) < 4+len(addr) {
return nil, 0, ErrMalformedAttrs
}
return addr, port, err
}
func mappedAddress(b []byte) (addr []byte, port uint16, err error) {
if len(b) < 8 {
if len(b) < 4 {
return nil, 0, ErrMalformedAttrs
}
port = uint16(b[2])<<8 | uint16(b[3])
switch ipFamily := b[1]; ipFamily { // RFC5389 Section 15.1
case 0x01: // IPv4
addr = b[4 : 4+4]
case 0x02: // IPv6
addr = b[4 : 4+16]
default:
addrField := b[4:]
addrLen := familyAddrLen(b[1])
if addrLen == 0 {
return nil, 0, ErrMalformedAttrs
}
return addr, port, err
if len(addrField) < addrLen {
return nil, 0, ErrMalformedAttrs
}
return append([]byte(nil), addrField[:addrLen]...), port, nil
}
// Is reports whether b is a STUN message.
func Is(b []byte) bool {
if len(b) < 20 {
if len(b) < headerLen {
return false // every STUN message must have a 20-byte header
}
// TODO RFC5389 suggests checking the first 2 bits of the header are zero.
if !bytes.Equal(b[4:8], magicCookie) {
return false
}
return true
return string(b[4:8]) == magicCookie
}

48
stun/stun_test.go
View File

@ -6,21 +6,18 @@
import (
"bytes"
"crypto/rand"
"fmt"
"log"
"net"
"testing"
"tailscale.com/stun"
)
func ExampleRequest() {
var transactionID [12]byte
if _, err := rand.Read(transactionID[:]); err != nil {
log.Fatal(err)
}
// TODO(bradfitz): fuzz this.
req := stun.Request(transactionID)
func ExampleRequest() {
txID := stun.NewTxID()
req := stun.Request(txID)
fmt.Printf("%x\n", req)
}
@ -44,7 +41,7 @@ func ExampleRequest() {
0x93, 0xe0, 0x80, 0x07,
},
wantAddr: []byte{72, 69, 33, 45},
wantPort: uint16(59028),
wantPort: 59028,
},
{
name: "google-2",
@ -59,7 +56,7 @@ func ExampleRequest() {
0x92, 0x3c, 0xe2, 0x71,
},
wantAddr: []byte{72, 69, 33, 45},
wantPort: uint16(59029),
wantPort: 59029,
},
{
name: "stun.sipgate.net:10000",
@ -81,7 +78,7 @@ func ExampleRequest() {
0xae, 0xad, 0x64, 0x44,
},
wantAddr: []byte{72, 69, 33, 45},
wantPort: uint16(58539),
wantPort: 58539,
},
{
name: "stun.powervoip.com:3478",
@ -99,7 +96,7 @@ func ExampleRequest() {
0x9d, 0x1d, 0xea, 0xa6,
},
wantAddr: []byte{72, 69, 33, 45},
wantPort: uint16(59859),
wantPort: 59859,
},
{
name: "in-process pion server",
@ -118,7 +115,30 @@ func ExampleRequest() {
0x4f, 0x3e, 0x30, 0x8e,
},
wantAddr: []byte{127, 0, 0, 1},
wantPort: uint16(61300),
wantPort: 61300,
},
{
name: "stuntman-server ipv6",
data: []byte{
0x01, 0x01, 0x00, 0x48, 0x21, 0x12, 0xa4, 0x42,
0x06, 0xf5, 0x66, 0x85, 0xd2, 0x8a, 0xf3, 0xe6,
0x9c, 0xe3, 0x41, 0xe2, 0x00, 0x01, 0x00, 0x14,
0x00, 0x02, 0x90, 0xce, 0x26, 0x02, 0x00, 0xd1,
0xb4, 0xcf, 0xc1, 0x00, 0x38, 0xb2, 0x31, 0xff,
0xfe, 0xef, 0x96, 0xf6, 0x80, 0x2b, 0x00, 0x14,
0x00, 0x02, 0x0d, 0x96, 0x26, 0x04, 0xa8, 0x80,
0x00, 0x02, 0x00, 0xd1, 0x00, 0x00, 0x00, 0x00,
0x00, 0xc5, 0x70, 0x01, 0x00, 0x20, 0x00, 0x14,
0x00, 0x02, 0xb1, 0xdc, 0x07, 0x10, 0xa4, 0x93,
0xb2, 0x3a, 0xa7, 0x85, 0xea, 0x38, 0xc2, 0x19,
0x62, 0x0c, 0xd7, 0x14,
},
wantTID: []byte{
6, 245, 102, 133, 210, 138, 243, 230, 156, 227,
65, 226,
},
wantAddr: net.ParseIP("2602:d1:b4cf:c100:38b2:31ff:feef:96f6"),
wantPort: 37070,
},
}
@ -134,7 +154,7 @@ func TestParseResponse(t *testing.T) {
t.Errorf("tid=%v, want %v", tID[:], test.wantTID)
}
if !bytes.Equal(addr, test.wantAddr) {
t.Errorf("addr=%v, want %v", addr, test.wantAddr)
t.Errorf("addr=%v (%v), want %v", addr, net.IP(addr), test.wantAddr)
}
if port != test.wantPort {
t.Errorf("port=%d, want %d", port, test.wantPort)