add perm guard

src/unix/permission_guard.rs

@@ -0,0 +1,81 @@
+//! Unix-specific implementation of the `PermissionGuard` struct.
+use std::fs::Permissions;
+use std::io;
+use std::os::unix::fs::PermissionsExt;
+use std::path::{Path, PathBuf};
+
+pub struct PermissionGuard {
+    path: PathBuf,
+    original_permissions: Permissions,
+}
+
+pub const READ_WRITE: u32 = 0o600; // User read/write
+
+impl PermissionGuard {
+    pub fn new<P: AsRef<Path>>(path: P, permissions: u32) -> io::Result<Self> {
+        let path = path.as_ref().to_path_buf();
+        let metadata = std::fs::metadata(&path)?;
+        let original_permissions = metadata.permissions();
+
+        let new_permissions = Permissions::from_mode(original_permissions.mode() | permissions);
+
+        // Set new permissions
+        std::fs::set_permissions(&path, new_permissions)?;
+
+        Ok(Self {
+            path,
+            original_permissions,
+        })
+    }
+}
+
+impl Drop for PermissionGuard {
+    fn drop(&mut self) {
+        if self.path.exists() {
+            if let Err(e) = std::fs::set_permissions(&self.path, self.original_permissions.clone())
+            {
+                eprintln!("Failed to restore file permissions: {}", e);
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs::{self, File};
+    use tempfile::tempdir;
+
+    #[test]
+    fn test_permission_guard_modifies_and_restores() -> io::Result<()> {
+        let dir = tempdir()?;
+        let test_file = dir.path().join("test-restore.txt");
+        File::create(&test_file)?;
+
+        // Set initial permissions to 0o002 so we can check if the guard modifies them
+        fs::set_permissions(&test_file, Permissions::from_mode(0o002))?;
+        let initial_mode = fs::metadata(&test_file)?.permissions().mode();
+
+        // Create scope for PermissionGuard
+        {
+            let _guard = PermissionGuard::new(&test_file, 0o200)?; // Write permission
+
+            // Check permissions were modified
+            let modified_mode = fs::metadata(&test_file)?.permissions().mode();
+            assert_ne!(initial_mode, modified_mode);
+            assert_eq!(modified_mode & 0o200, 0o200);
+        }
+
+        // Check permissions were restored after guard dropped
+        let final_mode = fs::metadata(&test_file)?.permissions().mode();
+        assert_eq!(initial_mode, final_mode);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_permission_guard_nonexistent_file() {
+        let result = PermissionGuard::new("nonexistent_file", 0o777);
+        assert!(result.is_err());
+    }
+}