fix(embedding): extract ONNX runtime atomically via temp file and rename

internal/embedding/service.go

@@ -628,21 +628,35 @@ func (s *Service) Close() error {
 }
 
 // writeGunzipped decompresses gz into path with the executable bit the dynamic linker needs.
-func writeGunzipped(path string, gz []byte) error {
+// It writes a temp file and renames it, so a crash never leaves a truncated library at path.
+func writeGunzipped(path string, gz []byte) (err error) {
 	zr, err := gzip.NewReader(bytes.NewReader(gz))
 	if err != nil {
 		return err
 	}
 	defer func() { _ = zr.Close() }()
 
-	// #nosec G302 G304 -- shared library needs 0755; path is under our own cache dir
-	f, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0755)
+	f, err := os.CreateTemp(filepath.Dir(path), filepath.Base(path)+".tmp*")
 	if err != nil {
 		return err
 	}
-	if _, err := io.Copy(f, zr); err != nil {
+	tmp := f.Name()
+	defer func() {
+		if err != nil {
+			_ = os.Remove(tmp)
+		}
+	}()
+
+	if _, err = io.Copy(f, zr); err != nil {
 		_ = f.Close()
 		return err
 	}
-	return f.Close()
+	if err = f.Close(); err != nil {
+		return err
+	}
+	// #nosec G302 -- shared library needs the executable bit for the dynamic linker
+	if err = os.Chmod(tmp, 0o755); err != nil {
+		return err
+	}
+	return os.Rename(tmp, path)
 }

internal/embedding/service_test.go

@@ -1,9 +1,13 @@
 package embedding
 
 import (
+	"bytes"
+	"compress/gzip"
 	"context"
 	"errors"
 	"math"
+	"os"
+	"path/filepath"
 	"sync"
 	"testing"
 	"time"
@@ -475,3 +479,57 @@ func cosineSimilarity(a, b []float32) float64 {
 
 	return dotProduct / (math.Sqrt(normA) * math.Sqrt(normB))
 }
+
+func gzipBytes(t *testing.T, data []byte) []byte {
+	t.Helper()
+	var buf bytes.Buffer
+	zw := gzip.NewWriter(&buf)
+	_, err := zw.Write(data)
+	require.NoError(t, err)
+	require.NoError(t, zw.Close())
+	return buf.Bytes()
+}
+
+func TestWriteGunzipped(t *testing.T) {
+	payload := bytes.Repeat([]byte("onnx"), 50_000)
+	good := gzipBytes(t, payload)
+
+	tests := []struct {
+		name     string
+		gz       []byte
+		wantErr  bool
+		wantFile bool
+	}{
+		{"valid archive", good, false, true},
+		{"truncated archive leaves no file", good[:len(good)/2], true, false},
+		{"not gzip leaves no file", []byte("plain text"), true, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			dir := t.TempDir()
+			path := filepath.Join(dir, "lib.so")
+
+			err := writeGunzipped(path, tt.gz)
+
+			if tt.wantErr {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+			}
+			_, statErr := os.Stat(path)
+			assert.Equal(t, tt.wantFile, statErr == nil)
+			entries, _ := os.ReadDir(dir)
+			if !tt.wantFile {
+				assert.Empty(t, entries, "no partial or temp files may remain")
+			}
+			if tt.wantFile {
+				got, err := os.ReadFile(path)
+				require.NoError(t, err)
+				assert.Equal(t, payload, got)
+				info, err := os.Stat(path)
+				require.NoError(t, err)
+				assert.Equal(t, os.FileMode(0o755), info.Mode().Perm())
+			}
+		})
+	}
+}