1 files changed, 19 insertions, 0 deletions
diff --git a/cli/standalone.rs b/cli/standalone.rs
index 067fec36a..6559242bd 100644
--- a/cli/standalone.rs
+++ b/cli/standalone.rs
@@ -5,6 +5,7 @@ use crate::tokio_util;
 use crate::version;
 use crate::worker::MainWorker;
 use crate::worker::WorkerOptions;
+use deno_core::error::bail;
 use deno_core::error::type_error;
 use deno_core::error::AnyError;
 use deno_core::futures::FutureExt;
@@ -169,6 +170,24 @@ pub async fn create_standalone_binary(
     } else {
       output
     };
+
+  if output.exists() {
+    // If the output is a directory, throw error
+    if output.is_dir() {
+      bail!("Could not compile: {:?} is a directory.", &output);
+    }
+
+    // Make sure we don't overwrite any file not created by Deno compiler.
+    // Check for magic trailer in last 16 bytes
+    let mut output_file = File::open(&output)?;
+    output_file.seek(SeekFrom::End(-16))?;
+    let mut trailer = [0; 16];
+    output_file.read_exact(&mut trailer)?;
+    let (magic_trailer, _) = trailer.split_at(8);
+    if magic_trailer != MAGIC_TRAILER {
+      bail!("Could not compile: cannot overwrite {:?}.", &output);
+    }
+  }
   tokio::fs::write(&output, final_bin).await?;
   #[cfg(unix)]
   {