1 files changed, 47 insertions, 0 deletions
diff --git a/internal/proxy/intrude_test.go b/internal/proxy/intrude_test.go
index 5df80e6..6a0007f 100644
--- a/internal/proxy/intrude_test.go
+++ b/internal/proxy/intrude_test.go
@@ -114,3 +114,50 @@ func TestIntrudeRequestCount(t *testing.T) {
 		t.Fatalf("expected 2 positions, got %d", len(positions))
 	}
 }
+
+func TestFixContentLength(t *testing.T) {
+	tests := []struct {
+		name string
+		raw  string
+		want string
+	}{
+		{
+			name: "recalculates a stale length",
+			raw:  "POST / HTTP/1.1\r\nHost: x\r\nContent-Length: 3\r\n\r\nfuzzedvalue",
+			want: "POST / HTTP/1.1\r\nHost: x\r\nContent-Length: 11\r\n\r\nfuzzedvalue",
+		},
+		{
+			name: "case-insensitive header name",
+			raw:  "POST / HTTP/1.1\r\nHost: x\r\ncontent-length: 1\r\n\r\nabc",
+			want: "POST / HTTP/1.1\r\nHost: x\r\nContent-Length: 3\r\n\r\nabc",
+		},
+		{
+			name: "no content-length header - unchanged",
+			raw:  "GET /§1§ HTTP/1.1\r\nHost: x\r\n\r\n",
+			want: "GET /§1§ HTTP/1.1\r\nHost: x\r\n\r\n",
+		},
+		{
+			name: "no body boundary - unchanged",
+			raw:  "GET / HTTP/1.1\r\nHost: x",
+			want: "GET / HTTP/1.1\r\nHost: x",
+		},
+		{
+			name: "two content-length headers - left alone, ambiguous smuggling case",
+			raw:  "POST / HTTP/1.1\r\nContent-Length: 3\r\nContent-Length: 999\r\n\r\nabc",
+			want: "POST / HTTP/1.1\r\nContent-Length: 3\r\nContent-Length: 999\r\n\r\nabc",
+		},
+		{
+			name: "empty body recalculates to zero",
+			raw:  "POST / HTTP/1.1\r\nContent-Length: 5\r\n\r\n",
+			want: "POST / HTTP/1.1\r\nContent-Length: 0\r\n\r\n",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := fixContentLength([]byte(tt.raw))
+			if string(got) != tt.want {
+				t.Errorf("fixContentLength(%q) = %q, want %q", tt.raw, got, tt.want)
+			}
+		})
+	}
+}