CreateThread interception, to use CreateRemoteThread

sandbox/win/src/process_policy_test.cc

Index: sandbox/win/src/process_policy_test.cc
diff --git a/sandbox/win/src/process_policy_test.cc b/sandbox/win/src/process_policy_test.cc
index 44effa36354b247bd84a339343c5aa8131a927f3..1b7c9fc228987aaa4e93bee9c4d9f49331504a1f 100644
--- a/sandbox/win/src/process_policy_test.cc
+++ b/sandbox/win/src/process_policy_test.cc
@@ -10,6 +10,7 @@
 #include "base/win/scoped_handle.h"
 #include "base/win/scoped_process_information.h"
 #include "base/win/windows_version.h"
+#include "sandbox/win/src/process_thread_interception.h"
 #include "sandbox/win/src/sandbox.h"
 #include "sandbox/win/src/sandbox_factory.h"
 #include "sandbox/win/src/sandbox_policy.h"
@@ -258,6 +259,75 @@ SBOX_TESTS_COMMAND int Process_OpenToken(int argc, wchar_t **argv) {
   return SBOX_TEST_FAILED;
 }
 
+// Generate a event name, used to test thread creation.
+std::wstring GenerateEventName(DWORD pid) {
+  wchar_t buff[30] = {0};
+  int res = swprintf_s(buff, sizeof(buff) / sizeof(buff[0]),
+                       L"ProcessPolicyTest_%08x", pid);
+  if (-1 != res) {
+    return std::wstring(buff);
+  }
+  return std::wstring();
+}
+
+// This is the function that is called when testing thread creation.
+// It is expected to set an event that the caller is waiting on.
+DWORD TestThreadFunc(LPVOID lpdwThreadParam) {
+  std::wstring event_name = GenerateEventName((DWORD)lpdwThreadParam);
+  if (!event_name.length()) {
+    return 1;
+  }
+  HANDLE event = ::OpenEvent(EVENT_ALL_ACCESS | EVENT_MODIFY_STATE, FALSE,
+                             event_name.c_str());
+  if (!event) {
+    return 1;
+  }
+  if (!SetEvent(event)) {
+    return 1;
+  }
+  return 0;
+}
+
+SBOX_TESTS_COMMAND int Process_CreateThread(int argc, wchar_t** argv) {
+  DWORD pid = ::GetCurrentProcessId();
+  std::wstring event_name = GenerateEventName(pid);
+  if (!event_name.length()) {
+    return SBOX_TEST_FAILED;
+  }
+  HANDLE event = ::CreateEvent(NULL, TRUE, FALSE, event_name.c_str());
+
+  if (!event) {
+    return SBOX_TEST_FAILED;
+  }
+
+  DWORD thread_id = 0;
+  HANDLE thread = NULL;
+  thread = ::CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)&TestThreadFunc,
+                          (LPVOID)pid, 0, &thread_id);
+
+  if (!thread) {
+    return SBOX_TEST_FAILED;
+  }
+  if (!thread_id) {
+    return SBOX_TEST_FAILED;

[Will Harris, 2015/12/03 06:41:50]

if the interception returns 0 thread_id on XP how does this test pass?

EDIT: oh, csrss isn't disconnected so it always passes through to the system?

EDIT2: presumably passing invalid arguments to CreateThread on XP would 

[liamjm (20p), 2015/12/03 21:53:29]

Yes, CSRSS is only disable on >= win8 so this code is never called for XP.

+  }
+
+  if (WaitForSingleObject(thread, INFINITE) != WAIT_OBJECT_0) {
+    return SBOX_TEST_FAILED;
+  }
+  DWORD exit_code = 0;
+  if (!GetExitCodeThread(thread, &exit_code)) {
+    return SBOX_TEST_FAILED;
+  }
+  if (exit_code) {
+    return SBOX_TEST_FAILED;
+  }
+  if (WaitForSingleObject(event, INFINITE) != WAIT_OBJECT_0) {
+    return SBOX_TEST_FAILED;
+  }
+  return SBOX_TEST_SUCCEEDED;
+}
+
 TEST(ProcessPolicyTest, TestAllAccess) {
   // Check if the "all access" rule fails to be added when the token is too
   // powerful.
@@ -382,4 +452,41 @@ TEST(ProcessPolicyTest, TestGetProcessTokenMaxAccessNoJob) {
             runner.RunTest(L"Process_GetChildProcessToken findstr.exe"));
 }
 
+// This tests that the CreateThread works with CSRSS not locked down.
+// In other words, that the interception passes through OK.
+TEST(ProcessPolicyTest, TestCreateThreadWithCsrss) {
+  TestRunner runner(JOB_NONE, USER_INTERACTIVE, USER_INTERACTIVE);
+  EXPECT_EQ(SBOX_TEST_SUCCEEDED, runner.RunTest(L"Process_CreateThread"));
+}
+
+// This tests that the CreateThread works with CSRSS locked down.
+// In other words, that the interception correctly works.
+TEST(ProcessPolicyTest, TestCreateThreadWithoutCsrss) {
+  TestRunner runner(JOB_NONE, USER_INTERACTIVE, USER_INTERACTIVE);
+
+  EXPECT_TRUE(runner.AddRule(TargetPolicy::SUBSYS_PROCESS,
+                             TargetPolicy::PROCESS_MIN_EXEC,

[Will Harris, 2015/12/03 06:41:50]

why do you need TargetPolicy::PROCESS_MIN_EXEC

[liamjm (20p), 2015/12/03 21:53:29]

Changed to PROCESS_ALL_EXEC as this is more suitable.

[Will Harris, 2015/12/03 23:58:13]

can you explain why this policy is needed at all?

[rickyz (no longer on Chrome), 2015/12/07 10:37:54]

Background for "this is not important" - this was a quick hack on my part to
work around the unintuitive fact that interceptions for CreateThread are not
performed unless there is a rule for that subsystem. Ideally hooking and policy
rules could be decoupled so that this isn't needed.

+                             L"this is not important"));
+
+  EXPECT_EQ(SBOX_TEST_SUCCEEDED, runner.RunTest(L"Process_CreateThread"));
+}
+
+// This tests that our CreateThread interceptors works when called directly.
+TEST(ProcessPolicyTest, TestCreateThreadOutsideSandbox) {
+  DWORD pid = ::GetCurrentProcessId();
+  std::wstring event_name = GenerateEventName(pid);
+  ASSERT_STRNE(NULL, event_name.c_str());
+  HANDLE event = ::CreateEvent(NULL, TRUE, FALSE, event_name.c_str());
+  EXPECT_NE(NULL, int(event));
+
+  DWORD thread_id = 0;
+  HANDLE thread = NULL;
+  thread = TargetCreateThread(::CreateThread, NULL, 0,
+                              (LPTHREAD_START_ROUTINE)&TestThreadFunc,
+                              (LPVOID)pid, 0, &thread_id);
+  EXPECT_NE(NULL, int(thread));
+  EXPECT_EQ(WAIT_OBJECT_0, WaitForSingleObject(thread, INFINITE));
+  EXPECT_EQ(WAIT_OBJECT_0, WaitForSingleObject(event, INFINITE));
+}
+
 }  // namespace sandbox