Merge pull request #155 from EmDecay/fix/147-input-channel-caps

fix: cap control requests and refuse file reads that never end

crates/engine/src/cmd/file.rs

@@ -51,11 +51,7 @@ fn path_arg<'a>(p: &'a Value, cmd: &str) -> Result<&'a str> {
 
 /// Read a STEP file as an Import feature.
 fn read_step(path: &str) -> Result<solvecraft_io::StepFeature> {
-    let meta = solvecraft_io::vfs::len(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
-    if meta > solvecraft_io::MAX_STEP_BYTES as u64 {
-        return Err(EngineError::Other(format!("{path}: file too large")));
-    }
-    let bytes = solvecraft_io::vfs::read(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
+    let bytes = solvecraft_io::vfs::read(path, solvecraft_io::MAX_STEP_BYTES).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
     solvecraft_io::step_import_feature(&bytes, path).map_err(|e| EngineError::Other(format!("{path}: {e}")))
 }
 
@@ -80,11 +76,7 @@ fn add_step(s: &mut Session, path: &str, name: Option<&str>) -> Result<Value> {
 
 /// Add a MeshImport feature for a 3MF or STL file.
 fn add_mesh(s: &mut Session, path: &str, name: Option<&str>) -> Result<Value> {
-    let meta = solvecraft_io::vfs::len(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
-    if meta > solvecraft_io::MAX_3MF_BYTES as u64 {
-        return Err(EngineError::Other(format!("{path}: file too large")));
-    }
-    let bytes = solvecraft_io::vfs::read(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
+    let bytes = solvecraft_io::vfs::read(path, solvecraft_io::MAX_3MF_BYTES).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
     let mf = solvecraft_io::mesh_import_feature(&bytes, path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
     let fname = name.filter(|n| !n.trim().is_empty()).unwrap_or(&mf.name).to_string();
     let id = s.doc_mut().add_feature(mf.kind, Some(&fname))?;
@@ -132,11 +124,7 @@ fn open(s: &mut Session, p: &Value) -> Result<Value> {
         let errors = s.model.results.iter().filter(|r| r.error.is_some()).count();
         return Ok(json!({"path": path, "features": s.doc.features.len(), "errors": errors, "bodies": r["bodies"], "warnings": r["warnings"]}));
     }
-    let meta = solvecraft_io::vfs::len(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
-    if meta as usize > solvecraft_io::MAX_DESIGN_BYTES {
-        return Err(EngineError::Other(format!("{path}: file too large")));
-    }
-    let bytes = solvecraft_io::vfs::read(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
+    let bytes = solvecraft_io::vfs::read(path, solvecraft_io::MAX_DESIGN_BYTES).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
     let doc = solvecraft_io::read_design(&bytes)?;
     *s = Session::new(doc);
     s.path = Some(path.to_string());

crates/engine/src/cmd/parameters.rs

@@ -226,16 +226,15 @@ fn export(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(json!({"format": format, "path": path, "text": text}))
 }
 
+/// Largest parameter table we read from a file.
+const MAX_PARAMETER_BYTES: usize = 16 << 20;
+
 fn import(s: &mut Session, p: &Value) -> Result<Value> {
     let cmd = "parameters.import";
     let text = match (str_(p, "text"), str_(p, "path")) {
         (Some(t), _) => t.to_string(),
         (None, Some(path)) => {
-            let meta = solvecraft_io::vfs::len(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
-            if meta > 16 << 20 {
-                return Err(bad(cmd, "file too large"));
-            }
-            solvecraft_io::vfs::read_to_string(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?
+            solvecraft_io::vfs::read_to_string(path, MAX_PARAMETER_BYTES).map_err(|e| EngineError::Other(format!("{path}: {e}")))?
         }
         _ => return Err(bad(cmd, "give `text` or `path`")),
     };

crates/engine/src/cmd/sketch_canvas.rs

@@ -31,11 +31,7 @@ fn image_bytes(p: &Value, cmd: &str) -> Result<Vec<u8>> {
         base64_decode(d).ok_or_else(|| bad(cmd, "`data` is not base64"))?
     } else {
         let path = str_(p, "path").filter(|x| !x.trim().is_empty() && x.len() < 4096).ok_or_else(|| bad(cmd, "give `path` or `data`"))?;
-        let meta = solvecraft_io::vfs::len(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
-        if meta as usize > MAX_CANVAS_BYTES {
-            return Err(bad(cmd, "the image is too large"));
-        }
-        solvecraft_io::vfs::read(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?
+        solvecraft_io::vfs::read(path, MAX_CANVAS_BYTES).map_err(|e| EngineError::Other(format!("{path}: {e}")))?
     };
     if b.len() > MAX_CANVAS_BYTES {
         return Err(bad(cmd, "the image is too large"));

crates/engine/src/cmd/sketch_import.rs

@@ -34,11 +34,7 @@ fn source_text(p: &Value, cmd: &str) -> Result<String> {
         return Ok(t.to_string());
     }
     let path = str_(p, "path").filter(|x| !x.trim().is_empty() && x.len() < 4096).ok_or_else(|| bad(cmd, "give `path` or `text`"))?;
-    let meta = solvecraft_io::vfs::len(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
-    if meta as usize > MAX_DRAWING_BYTES {
-        return Err(EngineError::Other(format!("{path}: file too large")));
-    }
-    let bytes = solvecraft_io::vfs::read(path).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
+    let bytes = solvecraft_io::vfs::read(path, MAX_DRAWING_BYTES).map_err(|e| EngineError::Other(format!("{path}: {e}")))?;
     Ok(String::from_utf8_lossy(&bytes).to_string())
 }
 

crates/engine/src/lib.rs

@@ -33,6 +33,10 @@ pub use solvecraft_kernel as kernel;
 pub use solvecraft_render as render;
 pub use solvecraft_sketch as sketch;
 
+/// Longest accepted request line on the JSON-lines channels (MCP over stdio and the control
+/// server over loopback), so both refuse runaway input at the same size.
+pub const MAX_LINE: usize = 16 << 20;
+
 #[derive(Debug, thiserror::Error)]
 pub enum EngineError {
     #[error("unknown command `{0}`")]

crates/engine/src/recovery.rs

@@ -100,7 +100,9 @@ pub fn load(dir: &Path, id: &str) -> Result<(Document, Entry)> {
         .ok()
         .and_then(|b| serde_json::from_slice(&b).ok())
         .ok_or_else(|| EngineError::Other(format!("no recovered design `{id}`")))?;
-    let bytes = fs::read(file(dir, id, "solvecraft")).map_err(|e| EngineError::Other(format!("recovered design `{id}`: {e}")))?;
+    let path = file(dir, id, "solvecraft");
+    let bytes = solvecraft_io::vfs::read(&path.to_string_lossy(), solvecraft_io::MAX_DESIGN_BYTES)
+        .map_err(|e| EngineError::Other(format!("recovered design `{id}`: {e}")))?;
     Ok((solvecraft_io::read_design(&bytes)?, entry))
 }
 

crates/engine/src/tests.rs

@@ -2299,3 +2299,29 @@ fn adopting_a_computed_component_keeps_its_warm_world_geometry() {
     s.invalidate_view(100);
     assert!(std::sync::Arc::ptr_eq(&prepared, &s.world_state()));
 }
+
+/// Every file command checked the size with the metadata and then read to the end. A character
+/// device reports a length of 0, so the cap passed and the read never finished; a FIFO blocked
+/// the calling thread, which over the control channel is the thread drawing the window.
+#[cfg(unix)]
+#[test]
+fn special_files_are_refused_by_every_file_command() {
+    let mut s = Session::default();
+    for cmd in ["doc.open", "parameters.import"] {
+        let r = s.execute(cmd, &json!({"path": "/dev/zero"}));
+        assert!(r.as_ref().is_err_and(|e| e.to_string().contains("not a regular file")), "{cmd}: {r:?}");
+    }
+    // The commands that check the extension first need a special file with the right name.
+    let dir = std::env::temp_dir().join(format!("solvecraft-special-{}", std::process::id()));
+    let _ = std::fs::create_dir_all(&dir);
+    for (cmd, name) in [("file.insert_step", "x.step"), ("file.insert_mesh", "x.3mf"), ("sketch.insert_dxf", "x.dxf")] {
+        let p = dir.join(name);
+        let _ = std::fs::remove_file(&p);
+        if !std::process::Command::new("mkfifo").arg(&p).status().map(|st| st.success()).unwrap_or(false) {
+            continue;
+        }
+        let r = s.execute(cmd, &json!({"path": p.to_string_lossy()}));
+        assert!(r.as_ref().is_err_and(|e| e.to_string().contains("not a regular file")), "{cmd}: {r:?}");
+    }
+    let _ = std::fs::remove_dir_all(&dir);
+}