103 lines
2.4 KiB
Go
103 lines
2.4 KiB
Go
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package dbus
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import (
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"bufio"
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"bytes"
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"crypto/rand"
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"crypto/sha1"
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"encoding/hex"
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"os"
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)
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// AuthCookieSha1 returns an Auth that authenticates as the given user with the
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// DBUS_COOKIE_SHA1 mechanism. The home parameter should specify the home
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// directory of the user.
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func AuthCookieSha1(user, home string) Auth {
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return authCookieSha1{user, home}
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}
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type authCookieSha1 struct {
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user, home string
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}
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func (a authCookieSha1) FirstData() ([]byte, []byte, AuthStatus) {
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b := make([]byte, 2*len(a.user))
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hex.Encode(b, []byte(a.user))
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return []byte("DBUS_COOKIE_SHA1"), b, AuthContinue
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}
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func (a authCookieSha1) HandleData(data []byte) ([]byte, AuthStatus) {
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challenge := make([]byte, len(data)/2)
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_, err := hex.Decode(challenge, data)
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if err != nil {
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return nil, AuthError
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}
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b := bytes.Split(challenge, []byte{' '})
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if len(b) != 3 {
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return nil, AuthError
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}
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context := b[0]
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id := b[1]
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svchallenge := b[2]
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cookie := a.getCookie(context, id)
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if cookie == nil {
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return nil, AuthError
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}
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clchallenge := a.generateChallenge()
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if clchallenge == nil {
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return nil, AuthError
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}
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hash := sha1.New()
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hash.Write(bytes.Join([][]byte{svchallenge, clchallenge, cookie}, []byte{':'}))
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hexhash := make([]byte, 2*hash.Size())
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hex.Encode(hexhash, hash.Sum(nil))
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data = append(clchallenge, ' ')
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data = append(data, hexhash...)
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resp := make([]byte, 2*len(data))
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hex.Encode(resp, data)
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return resp, AuthOk
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}
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// getCookie searches for the cookie identified by id in context and returns
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// the cookie content or nil. (Since HandleData can't return a specific error,
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// but only whether an error occurred, this function also doesn't bother to
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// return an error.)
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func (a authCookieSha1) getCookie(context, id []byte) []byte {
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file, err := os.Open(a.home + "/.dbus-keyrings/" + string(context))
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if err != nil {
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return nil
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}
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defer file.Close()
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rd := bufio.NewReader(file)
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for {
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line, err := rd.ReadBytes('\n')
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if err != nil {
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return nil
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}
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line = line[:len(line)-1]
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b := bytes.Split(line, []byte{' '})
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if len(b) != 3 {
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return nil
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}
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if bytes.Equal(b[0], id) {
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return b[2]
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}
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}
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}
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// generateChallenge returns a random, hex-encoded challenge, or nil on error
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// (see above).
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func (a authCookieSha1) generateChallenge() []byte {
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b := make([]byte, 16)
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n, err := rand.Read(b)
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if err != nil {
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return nil
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}
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if n != 16 {
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return nil
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}
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enc := make([]byte, 32)
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hex.Encode(enc, b)
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return enc
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}
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