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|
package dbus
import (
"bufio"
"bytes"
"crypto/rand"
"crypto/sha1"
"encoding/hex"
"errors"
"io"
"net"
"os"
"strconv"
)
type authenticator interface {
Mechanism() []byte
InitialResponse() []byte
ProcessData(challenge []byte) (response []byte, err error)
}
type authExternal struct {
}
func (p *authExternal) Mechanism() []byte {
return []byte("EXTERNAL")
}
func (p *authExternal) InitialResponse() []byte {
uid := []byte(strconv.Itoa(os.Geteuid()))
uidHex := make([]byte, hex.EncodedLen(len(uid)))
hex.Encode(uidHex, uid)
return uidHex
}
func (p *authExternal) ProcessData([]byte) ([]byte, error) {
return nil, errors.New("Unexpected Response")
}
type authDbusCookieSha1 struct {
}
func (p *authDbusCookieSha1) Mechanism() []byte {
return []byte("DBUS_COOKIE_SHA1")
}
func (p *authDbusCookieSha1) InitialResponse() []byte {
user := []byte(os.Getenv("USER"))
userHex := make([]byte, hex.EncodedLen(len(user)))
hex.Encode(userHex, user)
return userHex
}
func (p *authDbusCookieSha1) ProcessData(mesg []byte) ([]byte, error) {
decodedLen, err := hex.Decode(mesg, mesg)
if err != nil {
return nil, err
}
mesgTokens := bytes.SplitN(mesg[:decodedLen], []byte(" "), 3)
file, err := os.Open(os.Getenv("HOME") + "/.dbus-keyrings/" + string(mesgTokens[0]))
if err != nil {
return nil, err
}
defer file.Close()
fileStream := bufio.NewReader(file)
var cookie []byte
for {
line, _, err := fileStream.ReadLine()
if err == io.EOF {
return nil, errors.New("SHA1 Cookie not found")
} else if err != nil {
return nil, err
}
cookieTokens := bytes.SplitN(line, []byte(" "), 3)
if bytes.Compare(cookieTokens[0], mesgTokens[1]) == 0 {
cookie = cookieTokens[2]
break
}
}
challenge := make([]byte, len(mesgTokens[2]))
if _, err = rand.Read(challenge); err != nil {
return nil, err
}
for temp := challenge; ; {
if index := bytes.IndexAny(temp, " \t"); index == -1 {
break
} else if _, err := rand.Read(temp[index : index+1]); err != nil {
return nil, err
} else {
temp = temp[index:]
}
}
hash := sha1.New()
if _, err := hash.Write(bytes.Join([][]byte{mesgTokens[2], challenge, cookie}, []byte(":"))); err != nil {
return nil, err
}
resp := bytes.Join([][]byte{challenge, []byte(hex.EncodeToString(hash.Sum(nil)))}, []byte(" "))
respHex := make([]byte, hex.EncodedLen(len(resp)))
hex.Encode(respHex, resp)
return respHex, nil
}
func authenticate(conn net.Conn, authenticators []authenticator) error {
// If no authenticators are provided, try them all
if authenticators == nil {
authenticators = []authenticator{
new(authExternal),
new(authDbusCookieSha1)}
}
// The authentication process starts by writing a nul byte
if _, err := conn.Write([]byte{0}); err != nil {
return err
}
inStream := bufio.NewReader(conn)
send := func(command ...[]byte) ([][]byte, error) {
msg := bytes.Join(command, []byte(" "))
_, err := conn.Write(append(msg, []byte("\r\n")...))
if err != nil {
return nil, err
}
line, isPrefix, err := inStream.ReadLine()
if err != nil {
return nil, err
}
if isPrefix {
return nil, errors.New("Received line is too long")
}
return bytes.Split(line, []byte(" ")), err
}
success := false
for _, auth := range authenticators {
reply, err := send([]byte("AUTH"), auth.Mechanism(), auth.InitialResponse())
StatementLoop:
for {
if err != nil {
return err
}
if len(reply) < 1 {
return errors.New("No response command from server")
}
switch string(reply[0]) {
case "OK":
success = true
break StatementLoop
case "REJECTED":
// XXX: should note the list of
// supported mechanisms
break StatementLoop
case "ERROR":
return errors.New("Received error from server: " + string(bytes.Join(reply, []byte(" "))))
case "DATA":
var response []byte
response, err = auth.ProcessData(reply[1])
if err == nil {
reply, err = send([]byte("DATA"), response)
} else {
// Cancel so we can move on to
// the next mechanism.
reply, err = send([]byte("CANCEL"))
}
default:
return errors.New("Unknown response from server: " + string(bytes.Join(reply, []byte(" "))))
}
}
if success {
break
}
}
if !success {
return errors.New("Could not authenticate with any mechanism")
}
// XXX: UNIX FD negotiation would go here.
if _, err := conn.Write([]byte("BEGIN\r\n")); err != nil {
return err
}
return nil
}
|
