lib

commit a83f1388a9f6b5a8538d87f8fcbc3dbd1bacf9d3
parent 5667824c6f254a3e7cf8ea0680a38ada9f32fc9e
Author: triesap <tyson@radroots.org>
Date:   Sun,  9 Aug 2026 18:56:38 +0000

mobile_ffi: duplicate host media descriptors

- avoid /dev/fd path reliance on sandboxed Unix hosts
- preserve caller descriptor ownership through immediate duplication
- reject descriptor values outside the platform range
- verify formatting, checks, clippy, and focused tests

Diffstat:
M
crates/mobile_ffi/src/dto.rs
 | 
31
++++++++++++++++++++++++++++++-

1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/crates/mobile_ffi/src/dto.rs b/crates/mobile_ffi/src/dto.rs
@@ -2,6 +2,8 @@
 
 #[cfg(unix)]
 use std::os::unix::fs::FileExt;
+#[cfg(unix)]
+use std::os::{fd::BorrowedFd, unix::io::RawFd};
 
 use radroots_blossom::{BlobDescriptor, MediaType, Sha256};
 use radroots_event::{
@@ -1115,8 +1117,15 @@ fn read_media_file_descriptor(
     expected_size: u64,
     byte_size: usize,
 ) -> Result<Vec<u8>, RadrootsAppError> {
-    let file = std::fs::File::open(format!("/dev/fd/{file_descriptor}"))
+    let raw_file_descriptor = RawFd::try_from(file_descriptor)
+        .map_err(|_| RadrootsAppError::invalid_argument("media_handle_unavailable"))?;
+    // SAFETY: the host owns this descriptor for the duration of the synchronous
+    // FFI call. Duplicating it immediately gives Rust independent ownership
+    // without closing or otherwise consuming the host descriptor.
+    let borrowed = unsafe { BorrowedFd::borrow_raw(raw_file_descriptor) };
+    let owned = rustix::io::dup(borrowed)
         .map_err(|_| RadrootsAppError::invalid_argument("media_handle_unavailable"))?;
+    let file = std::fs::File::from(owned);
     let metadata = file
         .metadata()
         .map_err(|_| RadrootsAppError::invalid_argument("media_handle_unavailable"))?;
@@ -2182,6 +2191,26 @@ mod tests {
             media[0].url(),
             format!("http://127.0.0.1:3000/{digest}.png")
         );
+        assert_eq!(
+            file.as_file().metadata().expect("caller-owned media").len(),
+            bytes.len() as u64
+        );
+    }
+
+    #[test]
+    fn prepared_media_rejects_file_descriptors_outside_the_platform_range() {
+        let bytes = png(2, 2);
+        let blossom = blossom_slot();
+        let input = photo_input(u64::MAX, &bytes, Sha256::digest(&bytes).to_hex());
+
+        assert_eq!(
+            input
+                .command_and_media(1_800_000_000, Some(&blossom))
+                .expect_err("out-of-range descriptor")
+                .report()
+                .code,
+            "media_handle_unavailable"
+        );
     }
 
     #[test]