Harden scan robustness and tests

plugins/services/rsync_test.go

@@ -0,0 +1,39 @@
+//go:build (plugin_rsync || !plugin_selective) && go1.21
+
+package services
+
+import (
+	"io"
+	"testing"
+)
+
+type chunkedRsyncReader struct {
+	data      []byte
+	chunkSize int
+}
+
+func (r *chunkedRsyncReader) Read(p []byte) (int, error) {
+	if len(r.data) == 0 {
+		return 0, io.EOF
+	}
+	n := len(r.data)
+	if r.chunkSize > 0 && n > r.chunkSize {
+		n = r.chunkSize
+	}
+	if n > len(p) {
+		n = len(p)
+	}
+	copy(p, r.data[:n])
+	r.data = r.data[n:]
+	return n, nil
+}
+
+func TestReadRsyncLineHandlesChunkedReads(t *testing.T) {
+	got, err := readRsyncLine(&chunkedRsyncReader{data: []byte("@RSYNCD: 31.0\nrest"), chunkSize: 1}, 256)
+	if err != nil {
+		t.Fatalf("readRsyncLine() error = %v", err)
+	}
+	if got != "@RSYNCD: 31.0\n" {
+		t.Fatalf("readRsyncLine() = %q", got)
+	}
+}