initial release

internal/fileutil/fileutil.go

@@ -0,0 +1,32 @@
+package fileutil // import "github.com/pomerium/pomerium/internal/fileutil"
+
+import (
+	"errors"
+	"os"
+)
+
+// IsReadableFile reports whether the file exists and is readable.
+// If the error is non-nil, it means there might be a file or directory
+// with that name but we cannot read it.
+//
+// Adapted from the upspin.io source code.
+func IsReadableFile(path string) (bool, error) {
+	// Is it stattable and is it a plain file?
+	info, err := os.Stat(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false, nil // Item does not exist.
+		}
+		return false, err // Item is problematic.
+	}
+	if info.IsDir() {
+		return false, errors.New("is directory")
+	}
+	// Is it readable?
+	fd, err := os.Open(path)
+	if err != nil {
+		return false, errors.New("permission denied")
+	}
+	fd.Close()
+	return true, nil // Item exists and is readable.
+}