Fix crash when analyzing multipart RAR downloads

On Windows, when downloading the second or later part of a multipart
archive, unrar will attempt to open another file. Due to the
modifications we place on unrar to work within the sandbox, we
don't open the file, but instead use File::hOpenFile as the handle.
This is uninitialized memory, which is passed to GetFileType, causing
a crash.

This CL initializes hOpenFile to fix this problem and adds a test that
would have caught the issue.

Fixed: 1135503
Change-Id: I6cc83a5a2b5925900cde7b8b2dc8be64f0620d21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490334
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820896}

chrome/browser/safe_browsing/download_protection/download_protection_service_browsertest.cc

@@ -137,4 +137,23 @@ IN_PROC_BROWSER_TEST_F(DownloadProtectionServiceBrowserTest,
   EXPECT_EQ("random.exe", requests[0]->archived_binary(0).file_basename());
 }
 
+IN_PROC_BROWSER_TEST_F(DownloadProtectionServiceBrowserTest,
+                       MultipartRarInspectionSecondPart) {
+  embedded_test_server()->ServeFilesFromDirectory(GetTestDataDirectory());
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  WebUIInfoSingleton::GetInstance()->AddListenerForTesting();
+
+  GURL url = embedded_test_server()->GetURL(
+      "/safe_browsing/rar/multipart.part0002.rar");
+  DownloadAndWait(url);
+
+  const std::vector<std::unique_ptr<ClientDownloadRequest>>& requests =
+      WebUIInfoSingleton::GetInstance()->client_download_requests_sent();
+
+  ASSERT_EQ(1u, requests.size());
+  ASSERT_EQ(1, requests[0]->archived_binary_size());
+  EXPECT_EQ("random.exe", requests[0]->archived_binary(0).file_basename());
+}
+
 }  // namespace safe_browsing

third_party/unrar/patches/chromium_changes.patch

@@ -224,6 +224,15 @@ diff --git b/third_party/unrar/src/file.cpp a/third_party/unrar/src/file.cpp
 index 52c86c0621af..7dc5b724ca73 100644
 --- b/third_party/unrar/src/file.cpp
 +++ a/third_party/unrar/src/file.cpp
+@@ -17,6 +17,10 @@ File::File()
+ NoSequentialRead=false;
+ CreateMode=FMF_UNDEFINED;
+#endif
++
++#ifdef CHROMIUM_UNRAR
++  hOpenFile=FILE_BAD_HANDLE;
++#endif
+}
 @@ -51,6 +53,11 @@ bool File::Open(const wchar *Name,uint Mode)
    bool UpdateMode=(Mode & FMF_UPDATE)!=0;
    bool WriteMode=(Mode & FMF_WRITE)!=0;

third_party/unrar/src/file.cpp

@@ -17,6 +17,10 @@ File::File()
   NoSequentialRead=false;
   CreateMode=FMF_UNDEFINED;
 #endif
+
+#ifdef CHROMIUM_UNRAR
+  hOpenFile=FILE_BAD_HANDLE;
+#endif
 }