PolicyManager: Add a random number provider.
This patch adds a new provider with a single variable that returns a
random value from /dev/urandom every time it is called. The variable
is exported to all the policy implementations (currently none) in the
policy_manager/all_variables.h file.
BUG=None
TEST=unittests.
Change-Id: I6efdecd0f37f1a706b5a0dfd3a77ac4205e35aa0
Reviewed-on: https://chromium-review.googlesource.com/181537
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
diff --git a/policy_manager/all_variables.h b/policy_manager/all_variables.h
index e1982f2..be77698 100644
--- a/policy_manager/all_variables.h
+++ b/policy_manager/all_variables.h
@@ -13,4 +13,6 @@
// This file includes all the different provider's header files with these
// definitions.
+#include "policy_manager/random_vars.h"
+
#endif // CHROMEOS_PLATFORM_UPDATE_ENGINE_POLICY_MANAGER_ALL_VARIABLES_H
diff --git a/policy_manager/random_provider.cc b/policy_manager/random_provider.cc
new file mode 100644
index 0000000..f2373b0
--- /dev/null
+++ b/policy_manager/random_provider.cc
@@ -0,0 +1,84 @@
+// Copyright (c) 2014 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 <stdio.h>
+#include <unistd.h>
+
+#include <base/file_path.h>
+#include <base/file_util.h>
+
+#include "policy_manager/random_provider.h"
+#include "policy_manager/random_vars.h"
+
+using std::string;
+
+namespace {
+
+// The device providing randomness.
+const char* kRandomDevice = "/dev/urandom";
+
+} // namespace
+
+namespace chromeos_policy_manager {
+
+// The random variable class implementation.
+class RandomVariable : public Variable<uint64> {
+ public:
+ RandomVariable(FILE* fp) : fp_(fp) {}
+ virtual ~RandomVariable() {}
+
+ protected:
+ virtual const uint64* GetValue(base::TimeDelta /* timeout */,
+ string* errmsg) {
+ uint8 buf[sizeof(uint64)];
+ unsigned int buf_rd = 0;
+
+ while (buf_rd < sizeof(uint64)) {
+ int rd = fread(buf + buf_rd, 1, sizeof(uint64) - buf_rd, fp_.get());
+ if (rd == 0 || ferror(fp_.get())) {
+ // Either EOF on fp or read failed.
+ if (errmsg)
+ *errmsg = string("Error reading from the random device: ")
+ + kRandomDevice;
+ return NULL;
+ }
+ buf_rd += rd;
+ }
+ // Convert the result to a uint64.
+ uint64 result = 0;
+ for (unsigned int i = 0; i < sizeof(uint64); ++i)
+ result = (result << 8) | buf[i];
+
+ return new uint64(result);
+ }
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(RandomVariable);
+
+ file_util::ScopedFILE fp_;
+};
+
+
+// RandomProvider implementation.
+
+bool RandomProvider::Init(void) {
+ // Check for double Init()
+ if (var_random_seed != NULL)
+ return false;
+
+ FILE* fp = fopen(kRandomDevice, "r");
+ if (!fp)
+ return false;
+ var_random_seed = new RandomVariable(fp);
+ return true;
+}
+
+void RandomProvider::Finalize(void) {
+ if (var_random_seed) {
+ delete var_random_seed;
+ var_random_seed = NULL;
+ }
+}
+
+} // namespace chromeos_policy_manager
diff --git a/policy_manager/random_provider.h b/policy_manager/random_provider.h
new file mode 100644
index 0000000..7c7bae9
--- /dev/null
+++ b/policy_manager/random_provider.h
@@ -0,0 +1,30 @@
+// Copyright (c) 2014 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.
+
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_PROVIDER_H
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_PROVIDER_H
+
+#include "base/basictypes.h"
+
+namespace chromeos_policy_manager {
+
+// Provider of random values.
+class RandomProvider {
+ public:
+ RandomProvider() {}
+
+ // Initialize the provider variables and internal state. Returns whether it
+ // succeeded.
+ bool Init();
+
+ // Destroy all the provider variables in a best-effor approach.
+ void Finalize();
+
+ private:
+ DISALLOW_COPY_AND_ASSIGN(RandomProvider);
+};
+
+} // namespace chromeos_policy_manager
+
+#endif // CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_PROVIDER_H
diff --git a/policy_manager/random_provider_unittest.cc b/policy_manager/random_provider_unittest.cc
new file mode 100644
index 0000000..82ee5cc
--- /dev/null
+++ b/policy_manager/random_provider_unittest.cc
@@ -0,0 +1,57 @@
+// Copyright (c) 2014 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 <base/memory/scoped_ptr.h>
+#include <gtest/gtest.h>
+#include <string>
+
+#include "policy_manager/random_provider.h"
+#include "policy_manager/random_vars.h"
+
+using base::TimeDelta;
+using std::string;
+
+namespace chromeos_policy_manager {
+
+class PMRandomProviderTest : public ::testing::Test {
+ protected:
+ virtual void SetUp() {
+ ASSERT_TRUE(var_random_seed == NULL);
+ EXPECT_TRUE(provider_.Init());
+ }
+
+ virtual void TearDown() {
+ provider_.Finalize();
+ ASSERT_TRUE(var_random_seed == NULL);
+ }
+
+ private:
+ RandomProvider provider_;
+};
+
+TEST_F(PMRandomProviderTest, InitFinalize) {
+ // The provider should initialize the variable with a valid object.
+ ASSERT_TRUE(var_random_seed != NULL);
+}
+
+TEST_F(PMRandomProviderTest, GetRandomValues) {
+ string errmsg;
+ scoped_ptr<const uint64> value(
+ var_random_seed->GetValue(TimeDelta::FromSeconds(1.), &errmsg));
+ ASSERT_TRUE(value != NULL);
+
+ bool returns_allways_the_same_value = true;
+ // Test that at least the returned values are different. This test fails,
+ // by design, once every 2^320 runs.
+ for (int i = 0; i < 5; i++) {
+ scoped_ptr<const uint64> other_value(
+ var_random_seed->GetValue(TimeDelta::FromSeconds(1.), &errmsg));
+ ASSERT_TRUE(other_value != NULL);
+ returns_allways_the_same_value = returns_allways_the_same_value &&
+ *other_value == *value;
+ }
+ EXPECT_FALSE(returns_allways_the_same_value);
+}
+
+} // namespace chromeos_policy_manager
diff --git a/policy_manager/random_vars.cc b/policy_manager/random_vars.cc
new file mode 100644
index 0000000..1eb0c0a
--- /dev/null
+++ b/policy_manager/random_vars.cc
@@ -0,0 +1,11 @@
+// Copyright (c) 2014 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 "policy_manager/random_vars.h"
+
+namespace chromeos_policy_manager {
+
+Variable<uint64>* var_random_seed = NULL;
+
+} // namespace chromeos_policy_manager
diff --git a/policy_manager/random_vars.h b/policy_manager/random_vars.h
new file mode 100644
index 0000000..c1563c5
--- /dev/null
+++ b/policy_manager/random_vars.h
@@ -0,0 +1,21 @@
+// Copyright (c) 2014 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.
+
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_VARS_H
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_VARS_H
+
+#include "base/basictypes.h"
+#include "policy_manager/variable.h"
+
+namespace chromeos_policy_manager {
+
+// Return a random number every time it is requested. Note that values returned
+// by the variables are cached by the EvaluationContext, so the returned value
+// will be the same during the same policy request. If more random values are
+// needed use a PRNG seeded with this value.
+extern Variable<uint64>* var_random_seed;
+
+} // namespace chromeos_policy_manager
+
+#endif // CHROMEOS_PLATFORM_UPDATE_ENGINE_PM_RANDOM_VARS_H
diff --git a/policy_manager/variable.h b/policy_manager/variable.h
index 46defbc..6acd31f 100644
--- a/policy_manager/variable.h
+++ b/policy_manager/variable.h
@@ -8,6 +8,7 @@
#include <string>
#include <base/time.h>
+#include <gtest/gtest_prod.h> // for FRIEND_TEST
namespace chromeos_policy_manager {
@@ -18,6 +19,9 @@
virtual ~Variable() {}
protected:
+ friend class PMRandomProviderTest;
+ FRIEND_TEST(PMRandomProviderTest, GetRandomValues);
+
// Gets the current value of the variable. The current value is copied to a
// new object and returned. The caller of this method owns the object and
// should delete it.