panics and overlap

3 files changed, 45 insertions, 0 deletions

diff --git a/overlap.go b/overlap.go
new file mode 100644
index 0000000..564736b
--- /dev/null
+++ b/overlap.go
@@ -0,0 +1,18 @@
+//go:build !purego
+
+package rabbitio
+
+import "unsafe"
+
+func AnyOverlap(x, y []byte) bool {
+	return len(x) > 0 && len(y) > 0 &&
+		uintptr(unsafe.Pointer(&x[0])) <= uintptr(unsafe.Pointer(&y[len(y)-1])) &&
+		uintptr(unsafe.Pointer(&y[0])) <= uintptr(unsafe.Pointer(&x[len(x)-1]))
+}
+
+func InexactOverlap(x, y []byte) bool {
+	if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
+		return false
+	}
+	return AnyOverlap(x, y)
+}
diff --git a/purelap.go b/purelap.go
new file mode 100644
index 0000000..debd418
--- /dev/null
+++ b/purelap.go
@@ -0,0 +1,18 @@
+//go:build purego
+
+package rabbitio
+
+import "reflect"
+
+func AnyOverlap(x, y []byte) bool {
+	return len(x) > 0 && len(y) > 0 &&
+		reflect.ValueOf(&x[0]).Pointer() <= reflect.ValueOf(&y[len(y)-1]).Pointer() &&
+		reflect.ValueOf(&y[0]).Pointer() <= reflect.ValueOf(&x[len(x)-1]).Pointer()
+}
+
+func InexactOverlap(x, y []byte) bool {
+	if len(x) == 0 || len(y) == 0 || &x[0] == &y[0] {
+		return false
+	}
+	return AnyOverlap(x, y)
+}
diff --git a/rabbit.go b/rabbit.go
index 3b2ed12..3d77daa 100644
--- a/rabbit.go
+++ b/rabbit.go
@@ -136,6 +136,15 @@ func (r *rabbitCipher) extract() {
 // XORKeyStream read from src and perform xor on every elemnt of src and
 // write result on dst
 func (r *rabbitCipher) XORKeyStream(dst, src []byte) {
+
+	if len(dst) < len(src) {
+		panic("rabbitio: output smaller than input")
+	}
+
+	if InexactOverlap(dst, src) {
+		panic("rabbitio: invalid buffer memory overlap")
+	}
+
 	for i := range src {
 		if len(r.ks) == 0x00 {
 			r.extract()