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packet.go
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packet.go
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package radius
import (
"bytes"
"crypto/md5"
"crypto/rand"
"encoding/binary"
"errors"
)
// MaxPacketLength is the maximum wire length of a RADIUS packet.
const MaxPacketLength = 4096
// Packet is a RADIUS packet.
type Packet struct {
Code Code
Identifier byte
Authenticator [16]byte
CryptoAuthenticator [16]byte
Secret []byte
Attributes
}
// New creates a new packet with the Code, Secret fields set to the given
// values. The returned packet's Identifier and Authenticator fields are filled
// with random values.
//
// The function panics if not enough random data could be generated.
func New(code Code, secret []byte) *Packet {
var buff [17]byte
if _, err := rand.Read(buff[:]); err != nil {
panic(err)
}
packet := &Packet{
Code: code,
Identifier: buff[0],
Secret: secret,
}
copy(packet.Authenticator[:], buff[1:])
switch code {
case CodeAccountingRequest, CodeDisconnectRequest, CodeCoARequest:
// use null CryptoAuthenticator
default:
packet.CryptoAuthenticator = packet.Authenticator
}
return packet
}
// Parse parses an encoded RADIUS packet b. An error is returned if the packet
// is malformed.
func Parse(b []byte, cryptoAuthenticator []byte, secret []byte) (*Packet, error) {
if len(b) < 20 {
return nil, errors.New("radius: packet not at least 20 bytes long")
}
length := int(binary.BigEndian.Uint16(b[2:4]))
if length < 20 || length > MaxPacketLength || len(b) < length {
return nil, errors.New("radius: invalid packet length")
}
if len(cryptoAuthenticator) != 0 && len(cryptoAuthenticator) != 16 {
return nil, errors.New("cryptoAuthenticator has invalid length")
}
attrs, err := ParseAttributes(b[20:length])
if err != nil {
return nil, err
}
packet := &Packet{
Code: Code(b[0]),
Identifier: b[1],
Secret: secret,
Attributes: attrs,
}
copy(packet.Authenticator[:], b[4:20])
switch packet.Code {
case CodeAccountingRequest, CodeDisconnectRequest, CodeCoARequest:
// use null CryptoAuthenticator
default:
copy(packet.CryptoAuthenticator[:], cryptoAuthenticator)
}
return packet, nil
}
// Response returns a new packet that has the same identifier, secret, and
// authenticator as the current packet.
func (p *Packet) Response(code Code) *Packet {
q := &Packet{
Code: code,
Identifier: p.Identifier,
Secret: p.Secret,
}
q.Authenticator = p.Authenticator
q.CryptoAuthenticator = p.Authenticator
return q
}
// Encode encodes the RADIUS packet to wire format that can then
// be sent to a RADIUS client.
//
// If the RADIUS packet code requires it, the authenticator in
// the returned data will be a hash calculation based off of the packet
// data and secret. Use MarshalBinary() to get the packet in wire
// format without the hash calculation.
//
// An error is returned if the encoded packet is too long (due to its Attributes),
// or if the packet has an unknown Code.
func (p *Packet) Encode() ([]byte, error) {
b, err := p.MarshalBinary()
if err != nil {
return nil, err
}
switch p.Code {
case CodeAccessRequest, CodeStatusServer:
// Authenticator is sent as-is
case CodeAccessAccept, CodeAccessReject, CodeAccountingRequest, CodeAccountingResponse, CodeAccessChallenge, CodeDisconnectRequest, CodeDisconnectACK, CodeDisconnectNAK, CodeCoARequest, CodeCoAACK, CodeCoANAK:
hash := md5.New()
hash.Write(b[:4])
switch p.Code {
case CodeAccountingRequest, CodeDisconnectRequest, CodeCoARequest:
var nul [16]byte
hash.Write(nul[:])
default:
hash.Write(p.Authenticator[:])
}
hash.Write(b[20:])
hash.Write(p.Secret)
hash.Sum(b[4:4:20])
default:
return nil, errors.New("radius: unknown Packet Code")
}
return b, nil
}
// MarshalBinary returns the packet in wire format.
//
// The authenticator in the returned data is copied from p.Authenticator
// without any hash calculation. Use Encode() if the packet is intended
// to be sent to a RADIUS client and requires the authenticator to be
// calculated.
func (p *Packet) MarshalBinary() ([]byte, error) {
attributesLen, err := AttributesEncodedLen(p.Attributes)
if err != nil {
return nil, err
}
size := 20 + attributesLen
if size > MaxPacketLength {
return nil, errors.New("radius: packet is too large")
}
b := make([]byte, size)
b[0] = byte(p.Code)
b[1] = p.Identifier
binary.BigEndian.PutUint16(b[2:4], uint16(size))
copy(b[4:20], p.Authenticator[:])
p.Attributes.encodeTo(b[20:])
return b, nil
}
// IsAuthenticResponse returns if the given RADIUS response is an authentic
// response to the given request.
func IsAuthenticResponse(response, request, secret []byte) bool {
if len(response) < 20 || len(request) < 20 || len(secret) == 0 {
return false
}
hash := md5.New()
hash.Write(response[:4])
hash.Write(request[4:20])
hash.Write(response[20:])
hash.Write(secret)
var sum [md5.Size]byte
return bytes.Equal(hash.Sum(sum[:0]), response[4:20])
}
// IsAuthenticRequest returns if the given RADIUS request is an authentic
// request using the given secret.
func IsAuthenticRequest(request, secret []byte) bool {
if len(request) < 20 || len(secret) == 0 {
return false
}
switch Code(request[0]) {
case CodeAccessRequest, CodeStatusServer:
return true
case CodeAccountingRequest, CodeDisconnectRequest, CodeCoARequest:
hash := md5.New()
hash.Write(request[:4])
var nul [16]byte
hash.Write(nul[:])
hash.Write(request[20:])
hash.Write(secret)
var sum [md5.Size]byte
return bytes.Equal(hash.Sum(sum[:0]), request[4:20])
default:
return false
}
}