fix: Check image can be read before opening

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug Fixes
 
 - Correctly launch CleanupHost process only when needed in `--sif-fuse` flow.
+- Add specific error for unreadable image / overlay file.
 
 ## 3.10.0-rc.1 \[2022-05-04\]
 

internal/pkg/util/fs/helper.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2018-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE.md file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -397,7 +397,13 @@ func CopyFileAtomic(from, to string, mode os.FileMode) (err error) {
 	return nil
 }
 
-// IsWritable returns true of the file that is passed in
+// IsReadable returns true if the file that is passed in
+// is readable by the user (note: uid is checked, not euid).
+func IsReadable(path string) bool {
+	return unix.Access(path, unix.R_OK) == nil
+}
+
+// IsWritable returns true if the file that is passed in
 // is writable by the user (note: uid is checked, not euid).
 func IsWritable(path string) bool {
 	return unix.Access(path, unix.W_OK) == nil

pkg/image/image.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2020, Sylabs Inc. All rights reserved.
+// Copyright (c) 2018-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE.md file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -393,6 +393,10 @@ func Init(path string, writable bool) (*Image, error) {
 		return nil, err
 	}
 
+	if !fs.IsReadable(resolvedPath) {
+		return nil, fmt.Errorf("%s is not readable by the current user, check permissions", resolvedPath)
+	}
+
 	img := &Image{
 		Path:  resolvedPath,
 		Name:  filepath.Base(resolvedPath),