add support for kernel persistent keyring

See this PR for details: jsipprell#15

Author: cthayer

keyring.go

@@ -23,6 +23,7 @@ type Keyring interface {
 	Search(string) (*Key, error)
 	SearchType(string, string) (*Key, error)
 	SetDefaultTimeout(uint)
+	AttachPersistent() (Keyring, error)
 }
 
 // Named keyrings are user-created keyrings linked to a parent keyring. The
@@ -103,6 +104,13 @@ func (kr *keyring) SearchType(name string, keyType string) (*Key, error) {
 	return nil, err
 }
 
+// AttachPersistent attaches the current executing context's persistent
+// keyring to this keyring. See persistent-keyring(7) for more info.
+// It returns either an error, or the persistent Keyring.
+func (kr *keyring) AttachPersistent() (Keyring, error) {
+	return attachPersistent(kr.id)
+}
+
 // Return the current login session keyring
 func SessionKeyring() (Keyring, error) {
 	return newKeyring(keySpecSessionKeyring)

keyring_test.go

@@ -112,6 +112,18 @@ func TestCreateKeyring(t *testing.T) {
 	}
 }
 
+func TestAttachPersistentKeyring(t *testing.T) {
+	kr, err := SessionKeyring()
+	if err != nil {
+		t.Fatalf("unexpected test failure: could not create session keyring: %v", err)
+	}
+	pkr, err := kr.AttachPersistent()
+	if err != nil {
+		t.Fatalf("unexpected test failure: could not attach persistent keyring: %v", err)
+	}
+	t.Logf("found persistent keyring %d", pkr.Id())
+}
+
 func TestCreateNestedKeyring(t *testing.T) {
 	ring := helperTestCreateKeyring(nil, "", t)
 

sys_linux.go

@@ -354,3 +354,12 @@ func keyctl_Move(id, from_ring keyId, to_ring keyId, flags uint) error {
 	}
 	return nil
 }
+
+func attachPersistent(id keyId) (*keyring, error) {
+	uid := int32(-1)
+	r1, _, errno := syscall.Syscall(syscall_keyctl, uintptr(keyctlGetPersistent), uintptr(uid), uintptr(id))
+	if errno != 0 {
+		return nil, errno
+	}
+	return &keyring{id: keyId(r1)}, nil
+}