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package authorizer
import (
// WithUnixPeerCreds returns the credentials of the caller
func WithUnixPeerCreds() grpc.ServerOption {
return grpc.Creds(serverPeerCreds{})
// serverPeerCreds encapsulates a TransportCredentials which extracts uid and pid of caller via Unix Socket SO_PEERCRED
type serverPeerCreds struct{}
func (serverPeerCreds) ServerHandshake(conn net.Conn) (net.Conn, credentials.AuthInfo, error) {
var cred *unix.Ucred
// net.Conn is an interface. Expect only *net.UnixConn types
uc, ok := conn.(*net.UnixConn)
if !ok {
return conn, nil, fmt.Errorf(i18n.G("unexpected socket type"))
// Fetches raw network connection from UnixConn
raw, err := uc.SyscallConn()
if err != nil {
return conn, nil, fmt.Errorf(i18n.G("error opening raw connection: %s"), err)
// The raw.Control() callback does not return an error directly.
// In order to capture errors, we wrap already defined variable
// 'err' within the closure. 'err2' is then the error returned
// by Control() itself.
err2 := raw.Control(func(fd uintptr) {
cred, err = unix.GetsockoptUcred(int(fd),
if err != nil {
return conn, nil, fmt.Errorf(i18n.G("GetsockoptUcred() error: %s"), err)
if err2 != nil {
return conn, nil, fmt.Errorf(i18n.G("Control() error: %s"), err2)
return conn, peerCredsInfo{uid: cred.Uid, pid: cred.Pid}, nil
func (serverPeerCreds) ClientHandshake(ctx context.Context, authority string, conn net.Conn) (net.Conn, credentials.AuthInfo, error) {
return conn, nil, nil
func (serverPeerCreds) Info() credentials.ProtocolInfo { return credentials.ProtocolInfo{} }
func (serverPeerCreds) Clone() credentials.TransportCredentials { return nil }
func (serverPeerCreds) OverrideServerName(s string) error { return nil }
type peerCredsInfo struct {
uid uint32
pid int32
// AuthType returns a string encrypting uid and pid of caller.
func (p peerCredsInfo) AuthType() string {
return fmt.Sprintf("uid: %d, pid: %d", p.uid,