address review: canonicalize through the checked io gateway, treat any occupied export name as taken

crates/engine/src/clip_group_file.rs

@@ -89,7 +89,7 @@ fn decode_group_audio(
     let (mut decoded, mut index, mut file_of) = (Vec::new(), BTreeMap::new(), BTreeMap::new());
     // The folder as the file system knows it, so a link among the group's files can't lead out.
     let dir = if dir.as_os_str().is_empty() { Path::new(".") } else { dir };
-    let root = std::fs::canonicalize(dir).map_err(|err| EngineError::Io(format!("{}: {err}", dir.display())))?;
+    let root = crate::io::canonical_path(dir)?;
     for (old, rel) in audio_entries {
         let full = dir.join(rel);
         let escapes = |rel: &str| EngineError::BadParams(cmd_id.into(), format!("audio path escapes the group folder: {rel}"));
@@ -100,7 +100,7 @@ fn decode_group_audio(
         {
             return Err(escapes(rel));
         }
-        let key = std::fs::canonicalize(&full).map_err(|err| EngineError::Io(format!("{rel}: {err}")))?;
+        let key = crate::io::canonical_path(&full)?;
         if !key.starts_with(&root) {
             return Err(escapes(rel));
         }
@@ -292,6 +292,42 @@ mod tests {
         let _ = std::fs::remove_dir_all(&dir);
     }
 
+    /// Under a read root, a link in the group folder to a folder outside the root is refused the same way
+    /// whether or not the file asked for exists there, so the group cannot be used to probe for names.
+    #[cfg(unix)]
+    #[test]
+    fn links_out_of_the_read_root_are_refused_alike_for_existing_and_missing_files() {
+        let base = std::env::temp_dir().join(format!("sc-grp-root-{}", std::process::id()));
+        let _ = std::fs::remove_dir_all(&base);
+        let (dir, outside) = (base.join("group"), base.join("outside"));
+        std::fs::create_dir_all(&dir).unwrap();
+        std::fs::create_dir_all(&outside).unwrap();
+        let path = dir.join("drums.scgrp").to_string_lossy().to_string();
+        let mut e = crate::demo::demo_engine();
+        let kick = e.session().tracks.iter().find(|t| t.name == "Kick").map(|t| t.id).unwrap();
+        let ids: Vec<_> = e.session().track(kick).unwrap().clips().iter().take(1).map(|c| c.id.0).collect();
+        e.execute("file.export_clip_groups", &json!({"path": path, "clips": ids})).unwrap();
+        let mut file: serde_json::Value = serde_json::from_str(&std::fs::read_to_string(&path).unwrap()).unwrap();
+        let exported = file["audio"].as_object().unwrap().values().next().unwrap().as_str().unwrap().to_string();
+        std::fs::copy(dir.join(&exported), outside.join("real.wav")).unwrap();
+        std::os::unix::fs::symlink(&outside, dir.join("out")).unwrap();
+        let roots = crate::file_access::AutomationRoots::new(&[&dir], &[]).unwrap().unwrap();
+        let mut refusals = Vec::new();
+        for target in ["out/real.wav", "out/missing.wav"] {
+            for rel in file["audio"].as_object_mut().unwrap().values_mut() {
+                *rel = json!(target);
+            }
+            std::fs::write(&path, file.to_string()).unwrap();
+            let r = crate::file_access::confine(Some(&roots), || {
+                e.execute("file.import_clip_groups", &json!({"path": path, "at": 1000, "track": "Bass"}))
+            });
+            refusals.push(r.unwrap_err().to_string());
+        }
+        assert!(refusals[0].contains("outside the read root"), "{}", refusals[0]);
+        assert_eq!(refusals[0].replace("real.wav", "X"), refusals[1].replace("missing.wav", "X"), "existing and missing names are refused alike");
+        let _ = std::fs::remove_dir_all(&base);
+    }
+
     #[test]
     fn imported_clips_carry_no_auto_rename_scheme() {
         let dir = std::env::temp_dir().join(format!("sc-grp-names-{}", std::process::id()));

crates/engine/src/io.rs

@@ -85,6 +85,17 @@ pub(crate) fn make_dir(dir: impl AsRef<Path>) -> Result<()> {
     std::fs::create_dir_all(dir).map_err(|err| EngineError::Io(format!("{}: {err}", dir.display())))
 }
 
+/// `path` with its links followed, inside the automation read root when there is one. The root is
+/// checked on the path as named (links followed, a missing tail resolved by its nearest folder)
+/// before anything is resolved, so a name that leads out of the root is refused the same way
+/// whether or not it exists there.
+pub(crate) fn canonical_path(path: impl AsRef<Path>) -> Result<PathBuf> {
+    let path = path.as_ref();
+    let checked = if path.as_os_str().is_empty() { Path::new(".") } else { path };
+    crate::file_access::check_read(checked).map_err(EngineError::Io)?;
+    std::fs::canonicalize(path).map_err(|err| EngineError::Io(format!("{}: {err}", path.display())))
+}
+
 /// Write `bytes` to the file at `path`, inside the automation write root when there is one.
 pub(crate) fn write_path(path: impl AsRef<Path>, bytes: impl AsRef<[u8]>) -> Result<()> {
     let path = path.as_ref();
@@ -465,11 +476,16 @@ pub fn export_clips(e: &Engine, ids: &[soundcraft_model::ClipId], dir: &str) ->
         // The name is taken by creating the file, so whatever entry already has it (a link
         // to elsewhere included) is left alone rather than written through.
         let mut file = loop {
-            crate::file_access::check_write(&path).map_err(EngineError::Io)?;
-            match std::fs::OpenOptions::new().write(true).create_new(true).open(&path) {
-                Ok(f) => break f,
-                Err(err) if err.kind() == std::io::ErrorKind::AlreadyExists => {}
-                Err(err) => return Err(EngineError::Io(format!("{}: {err}", path.display()))),
+            // An occupied name is taken whatever it is (a link whose target is outside the write
+            // root too): it is only looked at, never resolved, so the root check does not stop the
+            // search for a free name. The folder itself was checked above.
+            if std::fs::symlink_metadata(&path).is_err() {
+                crate::file_access::check_write(&path).map_err(EngineError::Io)?;
+                match std::fs::OpenOptions::new().write(true).create_new(true).open(&path) {
+                    Ok(f) => break f,
+                    Err(err) if err.kind() == std::io::ErrorKind::AlreadyExists => {}
+                    Err(err) => return Err(EngineError::Io(format!("{}: {err}", path.display()))),
+                }
             }
             path = Path::new(dir).join(format!("{stem}-{k}.wav"));
             k = k.saturating_add(1);
@@ -849,6 +865,25 @@ mod exclusive_tests {
         assert!(dir.join(format!("{}-2.wav", sanitize_name(&c.name))).is_file(), "the next free name was used");
         let _ = std::fs::remove_dir_all(&dir);
     }
+
+    /// With a write root, a link out of it that holds the name is still just an occupied name.
+    #[cfg(unix)]
+    #[test]
+    fn export_skips_a_link_out_of_the_write_root_too() {
+        let dir = scratch("export-root-link");
+        let e = crate::demo::demo_engine();
+        let c = e.session().tracks.iter().find_map(|t| t.clips().iter().find(|c| c.is_audio()).cloned()).unwrap();
+        let elsewhere = scratch("export-root-elsewhere");
+        let target = elsewhere.join("target.wav");
+        std::os::unix::fs::symlink(&target, dir.join(format!("{}.wav", sanitize_name(&c.name)))).unwrap();
+        let roots = crate::file_access::AutomationRoots::new(&[], &[&dir]).unwrap().unwrap();
+        let n = crate::file_access::confine(Some(&roots), || export_clips(&e, &[c.id], &dir.to_string_lossy())).unwrap();
+        assert_eq!(n, 1);
+        assert!(!target.exists(), "the export followed the link out of the root");
+        assert!(dir.join(format!("{}-2.wav", sanitize_name(&c.name))).is_file(), "the next free name was used");
+        let _ = std::fs::remove_dir_all(&dir);
+        let _ = std::fs::remove_dir_all(&elsewhere);
+    }
 }
 
 #[cfg(test)]