util: Add better user lookup functions

When looking up users in fscrypt, we often want to proceed even if the
requested uid doesn't appear to be a valid user on the system. This
mainly occurs when a user is deleted, but they still have a login
protector on disk.

Thus, GetUser() with a bad uid creates a fake user with a pretty
placeholder name. The corresponding call sites of util.EffectiveUser are
changed (often simplifying logic). Various documentation is updated and
typos are fixed.

1 files changed, 3 insertions, 5 deletions

diff --git a/pam/pam.go b/pam/pam.go
index 0f20f30..adcb0c2 100644
--- a/pam/pam.go
+++ b/pam/pam.go
@@ -52,8 +52,9 @@ type Handle struct {
 func NewHandle(pamh unsafe.Pointer) (*Handle, error) {
 	var err error
 	h := &Handle{
-		handle: (*C.pam_handle_t)(pamh),
-		status: C.PAM_SUCCESS,
+		handle:   (*C.pam_handle_t)(pamh),
+		status:   C.PAM_SUCCESS,
+		OrigUser: util.CurrentUser(),
 	}
 
 	var pamUsername *C.char
@@ -65,9 +66,6 @@ func NewHandle(pamh unsafe.Pointer) (*Handle, error) {
 	if h.PamUser, err = user.Lookup(C.GoString(pamUsername)); err != nil {
 		return nil, err
 	}
-	if h.OrigUser, err = util.EffectiveUser(); err != nil {
-		return nil, err
-	}
 	return h, nil
 }