Change error handling to new package

This commit changes the error handing for the crypto, filesystem,
metadata, pam, and util packages to use the error handling library
github.com/pkg/errors. This means elimination of the FSError type, an
increased use of wrapping errors (as opposed to logging), switching
on the Cause() of an error (as opposed to its value), and improving our
integration tests involving TEST_FILESYSTEM_ROOT.

This commit also fixes a few bugs with the keyring code to ensure that
our {Find|Remove|Insert}PolicyKey functions are always operating on the
same keyring. The check for filesystem support has been moved from the
filesystem package to the metadata package. Finally, the API for the
filesystem package has been slightly modified:
	* filesystem.AllFilesystems() now returns all the filesystems in
	  sorted order
	* certain path methods are now public

O_SYNC is also removed for writing the metadata. We don't get that much
from syncing the metadata, as the actual file data could also be
corrupted by and IO error. The sync operation is also occasionally very
slow (~3 seconds) and can be unfriendly to battery life.

Change-Id: I392c2655141714b16dfdbc84ac09780072be2cf0

1 files changed, 9 insertions, 1 deletions

diff --git a/filesystem/path.go b/filesystem/path.go
index 3be1859..d788a6b 100644
--- a/filesystem/path.go
+++ b/filesystem/path.go
@@ -23,6 +23,8 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+
+	"github.com/pkg/errors"
 )
 
 // We only check the unix permissions and the sticky bit
@@ -34,8 +36,14 @@ func cannonicalizePath(path string) (string, error) {
 	if err != nil {
 		return "", err
 	}
+	path, err = filepath.EvalSymlinks(path)
+
+	// Get a better error if we have an invalid path
+	if pathErr, ok := err.(*os.PathError); ok {
+		err = errors.Wrap(pathErr.Err, pathErr.Path)
+	}
 
-	return filepath.EvalSymlinks(path)
+	return path, err
 }
 
 // loggedStat runs os.Stat, but it logs the error if stat returns any error