Prevent rootfs copy from following symlinks

1 files changed, 14 insertions, 2 deletions

diff --git a/src/rootfs.rs b/src/rootfs.rs
index 9246aa8..ea7d87b 100644
--- a/src/rootfs.rs
+++ b/src/rootfs.rs
@@ -173,8 +173,7 @@ fn copy_entry(
         if let Some(parent) = output.parent() {
             fs::create_dir_all(parent)?;
         }
-        fs::copy(source, &output)
-            .with_context(|| format!("copy {} to {}", source.display(), output.display()))?;
+        replace_with_file(source, &output)?;
         fs::set_permissions(&output, metadata.permissions())?;
         manifest.record(destination);
     } else {
@@ -213,6 +212,19 @@ fn enable_service(rootfs: &Path, service: &ServiceName, manifest: &mut MutationM
     Ok(())
 }
 
+fn replace_with_file(source: &Path, output: &Path) -> Result<()> {
+    match fs::symlink_metadata(output) {
+        Ok(metadata) if metadata.file_type().is_dir() => {
+            bail!("cannot replace directory with file: {}", output.display());
+        }
+        Ok(_) => fs::remove_file(output).with_context(|| format!("replace {}", output.display()))?,
+        Err(error) if error.kind() == std::io::ErrorKind::NotFound => {}
+        Err(error) => return Err(error).with_context(|| format!("inspect {}", output.display())),
+    }
+    fs::copy(source, output).with_context(|| format!("copy {} to {}", source.display(), output.display()))?;
+    Ok(())
+}
+
 fn replace_with_symlink(target: &Path, output: &Path) -> Result<()> {
     match fs::symlink_metadata(output) {
         Ok(metadata) if metadata.file_type().is_dir() => {