add keyctl read&describe to remove auth from keyring

Add method removeAllAuthFromKeyring.
Get key describes from keyring using KEYCTL_READ and KEYCTL_DESCRIBE, and remove them from keyring if the decription has prefix 'container-registry-login:'.

Signed-off-by: Qi Wang <[email protected]>

pkg/docker/config/config_linux.go

@@ -6,8 +6,11 @@ import (
 
 	"github.com/containers/image/pkg/keyctl"
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
+const keyDescribePrefix = "container-registry-login:"
+
 func getAuthFromKernelKeyring(registry string) (string, string, error) {
 	userkeyring, err := keyctl.UserKeyring()
 	if err != nil {
@@ -41,6 +44,37 @@ func deleteAuthFromKernelKeyring(registry string) error {
 	return key.Unlink()
 }
 
+func removeAllAuthFromKernelKeyring() error {
+	userkeyring, err := keyctl.UserKeyring()
+	if err != nil {
+		return err
+	}
+	keyIDs, err := userkeyring.ReadUserKeyring()
+	if err != nil {
+		return err
+	}
+	for _, kID := range keyIDs {
+		keyAttr, err := keyctl.Describe(kID)
+		if err != nil {
+			return nil
+		}
+		// split string "type;uid;gid;perm;description"
+		keyAttrs := strings.SplitN(keyAttr, ";", 5)
+		if len(keyAttrs) == 0 {
+			return errors.Errorf("Key attributes of %d are not avaliable", kID.ID())
+		}
+		keyDescribe := keyAttrs[len(keyAttrs)-1]
+		if strings.HasPrefix(keyDescribe, keyDescribePrefix) {
+			err := keyctl.Unlink(userkeyring, kID)
+			if err != nil {
+				return errors.Wrapf(err, "error unlinking key %d", kID.ID())
+			}
+			logrus.Debugf("unlink key %d:%s", kID.ID(), keyAttr)
+		}
+	}
+	return nil
+}
+
 func setAuthToKernelKeyring(registry, username, password string) error {
 	keyring, err := keyctl.SessionKeyring()
 	if err != nil {

pkg/keyctl/key.go

@@ -62,3 +62,12 @@ func (k *Key) Unlink() error {
 	_, err := unix.KeyctlInt(unix.KEYCTL_UNLINK, int(k.id), int(k.ring), 0, 0)
 	return err
 }
+
+// Describe returns a string describing the attributes of a specified key
+func Describe(kID ID) (string, error) {
+	keyDescribe, err := unix.KeyctlString(unix.KEYCTL_DESCRIBE, int(kID.ID()))
+	if err != nil {
+		return "", err
+	}
+	return keyDescribe, nil
+}

pkg/keyctl/keyring.go

@@ -11,6 +11,9 @@
 package keyctl
 
 import (
+	"encoding/binary"
+	"unsafe"
+
 	"golang.org/x/sys/unix"
 )
 
@@ -19,10 +22,12 @@ type Keyring interface {
 	ID
 	Add(string, []byte) (*Key, error)
 	Search(string) (*Key, error)
+	ReadUserKeyring() ([]*Key, error)
 }
 
 type keyring struct {
-	id keyID
+	id   keyID
+	size int
 }
 
 // ID is unique 32-bit serial number identifiers for all Keys and Keyrings have.
@@ -77,3 +82,68 @@ func Link(parent Keyring, child ID) error {
 	_, err := unix.KeyctlInt(unix.KEYCTL_LINK, int(child.ID()), int(parent.ID()), 0, 0)
 	return err
 }
+
+// ReadUserKeyring reads user keyring and returns slice of Key with id field(key_serial_t) representing the IDs of all the keys that are linked to it
+func (kr *keyring) ReadUserKeyring() ([]*Key, error) {
+	var (
+		b        []byte
+		err      error
+		sizeRead int
+		keyArr   []*Key
+	)
+
+	if kr.size == 0 {
+		kr.size = 4
+	}
+
+	size := kr.size
+
+	b = make([]byte, size)
+	sizeRead = size + 1
+	for sizeRead > size {
+		r1, err := unix.KeyctlBuffer(unix.KEYCTL_READ, unix.KEY_SPEC_USER_KEYRING, b, size)
+
+		if err != nil {
+			return nil, err
+		}
+
+		if sizeRead = int(r1); sizeRead > size {
+			b = make([]byte, sizeRead)
+			size = sizeRead
+			sizeRead = size + 1
+		} else {
+			kr.size = sizeRead
+		}
+	}
+
+	keyIDs := getKeyIDsFromByte(b[:kr.size])
+	for _, kid := range keyIDs {
+		keyArr = append(keyArr, &Key{id: kid})
+	}
+	return keyArr, err
+}
+
+func getKeyIDsFromByte(byteKeyIDs []byte) []keyID {
+	idSize := 4
+
+	// check the endianness
+	var nativeEndian binary.ByteOrder
+	buf := [2]byte{}
+	*(*uint16)(unsafe.Pointer(&buf[0])) = uint16(0xABCD)
+
+	switch buf {
+	case [2]byte{0xCD, 0xAB}:
+		nativeEndian = binary.LittleEndian
+	case [2]byte{0xAB, 0xCD}:
+		nativeEndian = binary.BigEndian
+	default:
+		panic("Could not determine native endianness.")
+	}
+
+	var keyIDs []keyID
+	for idx := 0; idx+idSize <= len(byteKeyIDs); idx = idx + idSize {
+		tempID := byteKeyIDs[idx : idx+idSize]
+		keyIDs = append(keyIDs, keyID(nativeEndian.Uint32(tempID)))
+	}
+	return keyIDs
+}

pkg/keyctl/keyring_test.go

@@ -4,6 +4,7 @@ package keyctl
 
 import (
 	"crypto/rand"
+	"strings"
 	"testing"
 )
 
@@ -124,3 +125,73 @@ func TestUnlink(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestReadUserKeyring(t *testing.T) {
+	token := make([]byte, 20)
+	rand.Read(token)
+
+	testname := "testread"
+
+	userKeyring, err := UserKeyring()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	sessionKeyring, err := SessionKeyring()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	key, err := sessionKeyring.Add(testname, token)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := true
+	err = Link(userKeyring, key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	keys, err := userKeyring.ReadUserKeyring()
+	if err != nil {
+		t.Fatal(err)
+	}
+	keyExists := false
+	for _, k := range keys {
+		if key.ID() == k.ID() {
+			keyExists = true
+			break
+		}
+	}
+	if keyExists != expected {
+		t.Errorf("ReadUserKeyring error: expected ID %d does not exist", key.ID())
+	}
+}
+
+func TestDescribe(t *testing.T) {
+	token := make([]byte, 20)
+	rand.Read(token)
+
+	testname := "testdescribe"
+
+	sessionKeyring, err := SessionKeyring()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	key, err := sessionKeyring.Add(testname, token)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	describe, err := Describe(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expected := true
+	getDescribe := strings.Contains(describe, testname)
+	if getDescribe != expected {
+		t.Errorf("Describe error: expect to get %s, but get %s", testname, describe)
+	}
+}