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packet.go
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packet.go
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package nsca
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/des"
"crypto/rand"
"encoding/binary"
"fmt"
"hash/crc32"
"io"
)
const (
STATE_OK = iota
STATE_WARNING
STATE_CRITICAL
STATE_UNKNOWN
)
const (
ENCRYPT_NONE = iota /* no encryption */
ENCRYPT_XOR /* not really encrypted, just obfuscated */
ENCRYPT_DES /* DES */
ENCRYPT_3DES /* 3DES or Triple DES */
ENCRYPT_CAST128 /* CAST-128 */ /* UNUSED */
ENCRYPT_CAST256 /* CAST-256 */ /* UNUSED */
ENCRYPT_XTEA /* xTEA */ /* UNUSED */
ENCRYPT_3WAY /* 3-WAY */ /* UNUSED */
ENCRYPT_BLOWFISH /* SKIPJACK */ /* UNUSED */
ENCRYPT_TWOFISH /* TWOFISH */ /* UNUSED */
ENCRYPT_LOKI97 /* LOKI97 */ /* UNUSED */
ENCRYPT_RC2 /* RC2 */ /* UNUSED */
ENCRYPT_ARCFOUR /* RC4 */ /* UNUSED */
ENCRYPT_RC6 /* RC6 */ /* UNUSED */
ENCRYPT_RIJNDAEL128 /* RIJNDAEL-128 */ /* AES-128 */
ENCRYPT_RIJNDAEL192 /* RIJNDAEL-192 */ /* AES-192 */
ENCRYPT_RIJNDAEL256 /* RIJNDAEL-256 */ /* AES-256 */
ENCRYPT_MARS /* MARS */ /* UNUSED */
ENCRYPT_PANAMA /* PANAMA */ /* UNUSED */
ENCRYPT_WAKE /* WAKE */ /* UNUSED */
ENCRYPT_SERPENT /* SERPENT */ /* UNUSED */
ENCRYPT_IDEA /* IDEA */ /* UNUSED */
ENCRYPT_ENIGMA /* ENIGMA (Unix crypt) */ /* UNUSED */
ENCRYPT_GOST /* GOST */ /* UNUSED */
ENCRYPT_SAFER64 /* SAFER-sk64 */ /* UNUSED */
ENCRYPT_SAFER128 /* SAFER-sk128 */ /* UNUSED */
ENCRYPT_SAFERPLUS /* SAFER+ */ /* UNUSED */
)
type dataPacket struct {
packetVersion int16
crc32 uint32
timestamp uint32
returnCode int16
hostName string // 64 char max
serviceDescription string // 128 char max
pluginOutput string // 512 char max
}
type initializationPacket struct {
iv []byte // 128 bytes
timestamp uint32
}
type encryption struct {
method int
iv []byte
password []byte
}
func (e *encryption) encrypt(b []byte) error {
if e.method == ENCRYPT_NONE {
return nil
}
if len(e.password) == 0 {
return fmt.Errorf("Zero length password")
}
if e.method == ENCRYPT_XOR {
for i := range b {
b[i] = b[i] ^ e.iv[i%len(e.iv)] ^ e.password[i%len(e.password)]
}
return nil
}
var err error
var block cipher.Block
key := make([]byte, 128)
copy(key, e.password)
switch e.method {
case ENCRYPT_DES:
block, err = des.NewCipher(key[:des.BlockSize])
case ENCRYPT_3DES:
block, err = des.NewTripleDESCipher(key[:des.BlockSize*3])
case ENCRYPT_RIJNDAEL128:
block, err = aes.NewCipher(key[:16])
case ENCRYPT_RIJNDAEL192:
block, err = aes.NewCipher(key[:24])
case ENCRYPT_RIJNDAEL256:
block, err = aes.NewCipher(key[:32])
case ENCRYPT_CAST128:
fallthrough
case ENCRYPT_CAST256:
fallthrough
case ENCRYPT_XTEA:
fallthrough
case ENCRYPT_3WAY:
fallthrough
case ENCRYPT_BLOWFISH:
fallthrough
case ENCRYPT_TWOFISH:
fallthrough
case ENCRYPT_LOKI97:
fallthrough
case ENCRYPT_RC2:
fallthrough
case ENCRYPT_ARCFOUR:
fallthrough
case ENCRYPT_RC6:
fallthrough
case ENCRYPT_MARS:
fallthrough
case ENCRYPT_PANAMA:
fallthrough
case ENCRYPT_WAKE:
fallthrough
case ENCRYPT_SERPENT:
fallthrough
case ENCRYPT_IDEA:
fallthrough
case ENCRYPT_ENIGMA:
fallthrough
case ENCRYPT_GOST:
fallthrough
case ENCRYPT_SAFER64:
fallthrough
case ENCRYPT_SAFER128:
fallthrough
case ENCRYPT_SAFERPLUS:
err = fmt.Errorf("Unsupported encryption method")
default:
err = fmt.Errorf("Unrecognized encryption method")
}
if err != nil {
return err
}
enc := cipher.NewCFBEncrypter(block, e.iv[:block.BlockSize()])
enc.XORKeyStream(b, b)
return nil
}
func newEncryption(method int, iv []byte, password string) *encryption {
e := encryption{
method: method,
iv: make([]byte, len(iv)),
password: make([]byte, len(password)),
}
copy(e.iv, iv)
copy(e.password, password)
return &e
}
func readInitializationPacket(reader io.Reader) (*initializationPacket, error) {
p := initializationPacket{iv: make([]byte, 128)}
err := binary.Read(reader, binary.BigEndian, p.iv)
if err != nil {
return nil, err
}
err = binary.Read(reader, binary.BigEndian, &p.timestamp)
if err != nil {
return nil, err
}
return &p, nil
}
func makeBuffer(s string, length int) ([]byte, error) {
if length == 0 {
return make([]byte, 0), nil
}
b := make([]byte, length)
n, err := rand.Read(b)
if err != nil {
return nil, err
}
if n != len(b) {
return nil, fmt.Errorf("Unexpected result from rand.Read")
}
n = copy(b, s)
if n == len(b) {
b[len(b)-1] = 0
} else {
b[n] = 0
}
return b, nil
}
func newDataPacket(serverTimestamp uint32, returnCode int16, hostName, serviceDescription, pluginOutput string) *dataPacket {
d := dataPacket{
packetVersion: 3,
timestamp: serverTimestamp,
returnCode: returnCode,
hostName: hostName,
serviceDescription: serviceDescription,
pluginOutput: pluginOutput,
}
return &d
}
func (p *dataPacket) write(w io.Writer, e *encryption) error {
if p.packetVersion == 0 {
p.packetVersion = 3
}
p.crc32 = 0
hostName, err := makeBuffer(p.hostName, 64)
if err != nil {
return err
}
service, err := makeBuffer(p.serviceDescription, 128)
if err != nil {
return err
}
output, err := makeBuffer(p.pluginOutput, 512)
if err != nil {
return err
}
// 2 bytes for c struct padding
padding, err := makeBuffer("", 2)
if err != nil {
return err
}
buf := new(bytes.Buffer)
binary.Write(buf, binary.BigEndian, p.packetVersion)
binary.Write(buf, binary.BigEndian, padding)
binary.Write(buf, binary.BigEndian, p.crc32)
binary.Write(buf, binary.BigEndian, p.timestamp)
binary.Write(buf, binary.BigEndian, p.returnCode)
binary.Write(buf, binary.BigEndian, hostName)
binary.Write(buf, binary.BigEndian, service)
binary.Write(buf, binary.BigEndian, output)
binary.Write(buf, binary.BigEndian, padding)
b := buf.Bytes()
p.crc32 = crc32.ChecksumIEEE(b)
crc := make([]byte, 4)
binary.BigEndian.PutUint32(crc, p.crc32)
copy(b[4:], crc)
err = e.encrypt(b)
if err != nil {
return err
}
n, err := w.Write(b)
if err != nil {
return err
}
if n != len(b) {
return fmt.Errorf("Wrong byte count returned from write: expected %d, got %d", len(b), n)
}
return nil
}