AU: Check the delta magic and fail on mismatch.

delta_performer_unittest.cc

 // Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sys/mount.h>
 #include <inttypes.h>
 
 #include <algorithm>
 #include <string>
 #include <vector>
@@ skipping 349 matching lines @@
 }
 
 TEST(DeltaPerformerTest, RunAsRootFullSmallImageTest) {
   DoSmallImageTest(true, true, false);
 }
 
 TEST(DeltaPerformerTest, RunAsRootNoopSmallImageTest) {
   DoSmallImageTest(false, false, true);
 }
 
+TEST(DeltaPerformerTest, BadDeltaMagicTest) {
+  PrefsMock prefs;
+  DeltaPerformer performer(&prefs);
+  EXPECT_EQ(0, performer.Open("/dev/null", 0, 0));
+  EXPECT_TRUE(performer.OpenKernel("/dev/null"));
+  EXPECT_EQ(4, performer.Write("junk", 4));
+  EXPECT_EQ(8, performer.Write("morejunk", 8));
+  EXPECT_LT(performer.Write("morejunk", 8), 0);
+  EXPECT_LT(performer.Close(), 0);
+}
+
 TEST(DeltaPerformerTest, IsIdempotentOperationTest) {
   DeltaArchiveManifest_InstallOperation op;
   EXPECT_TRUE(DeltaPerformer::IsIdempotentOperation(op));
   *(op.add_dst_extents()) = ExtentForRange(0, 5);
   EXPECT_TRUE(DeltaPerformer::IsIdempotentOperation(op));
   *(op.add_src_extents()) = ExtentForRange(4, 1);
   EXPECT_FALSE(DeltaPerformer::IsIdempotentOperation(op));
   op.clear_src_extents();
   *(op.add_src_extents()) = ExtentForRange(5, 3);
   EXPECT_TRUE(DeltaPerformer::IsIdempotentOperation(op));
   *(op.add_dst_extents()) = ExtentForRange(20, 6);
   EXPECT_TRUE(DeltaPerformer::IsIdempotentOperation(op));
   *(op.add_src_extents()) = ExtentForRange(19, 2);
   EXPECT_FALSE(DeltaPerformer::IsIdempotentOperation(op));
 }
 
 }  // namespace chromeos_update_engine