Creating a new RNG and replacing rand().

[ Merge of http://go/wvgerrit/84607 ]
[ Merge of http://go/wvgerrit/84608 ]

The primary goal is to replace the use of `rand()` with the random
number generators provided with the C++11 standard.

This simplified generator wraps some of the technical aspects of the
<random> library and provides an interface for uniformly distributed
integers.

As part of the `rand()` purge in the CDM, all uses of the C random int
function in `core()` have been removed.  Places that previously used
`rand()` now use `CdmRandom` facilities.

Test: Linux unittest and Android unittest
Bug: 130680365
Change-Id: Ica383870536ed462dbb80e630c2d66845e38b937

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -392,8 +392,6 @@ class CdmEngine {
   Clock clock_;
   std::string spoid_;
 
-  static bool seeded_;
-
   // usage related variables
   std::unique_ptr<CdmSession> usage_session_;
   std::unique_ptr<UsagePropertySet> usage_property_set_;

libwvdrmengine/cdm/core/include/usage_table_header.h

@@ -83,10 +83,6 @@ class UsageTableHeader {
   // for the objects that DeleteEntry depends on.
   void DeleteEntryForTest(uint32_t usage_entry_number);
 
-  // TODO(rfrias): Move to utility class
-  static int64_t GetRandomInRange(size_t upper_bound_exclusive);
-  static int64_t GetRandomInRangeWithExclusion(size_t upper_bound_exclusive,
-                                               size_t exclude);
   size_t size() { return usage_entry_info_.size(); }
 
  private:

libwvdrmengine/cdm/core/src/cdm_engine.cpp

@@ -12,6 +12,7 @@
 #include <memory>
 #include <sstream>
 
+#include "cdm_random.h"
 #include "cdm_session.h"
 #include "cdm_session_map.h"
 #include "clock.h"
@@ -69,8 +70,6 @@ class UsagePropertySet : public CdmClientPropertySet {
   const std::string empty_;
 };
 
-bool CdmEngine::seeded_ = false;
-
 CdmEngine::CdmEngine(FileSystem* file_system,
                      std::shared_ptr<metrics::EngineMetrics> metrics,
                      const std::string& spoid)
@@ -83,11 +82,7 @@ CdmEngine::CdmEngine(FileSystem* file_system,
       usage_property_set_(),
       last_usage_information_update_time_(0) {
   assert(file_system);
-  if (!seeded_) {
-    Properties::Init();
-    srand(clock_.GetCurrentTime());
-    seeded_ = true;
-  }
+  Properties::Init();
 }
 
 CdmEngine::~CdmEngine() {
@@ -1260,7 +1255,8 @@ CdmResponseType CdmEngine::GetUsageInfo(const std::string& app_id,
                                         CdmUsageInfo* usage_info) {
   LOGI("Getting usage info: app_id = %s", app_id.c_str());
   // Return a random usage report from a random security level
-  SecurityLevel security_level = ((rand() % 2) == 0) ? kLevelDefault : kLevel3;
+  SecurityLevel security_level =
+      CdmRandom::RandomBool() ? kLevelDefault : kLevel3;
   CdmResponseType status = UNKNOWN_ERROR;
   if (!usage_info) {
     LOGE("No usage info destination");
@@ -1328,7 +1324,7 @@ CdmResponseType CdmEngine::GetUsageInfo(const std::string& app_id,
 
   usage_info->resize(kUsageReportsPerRequest);
 
-  size_t index = rand() % usage_data.size();
+  size_t index = CdmRandom::RandomInRange(usage_data.size() - 1);
   status = usage_session_->RestoreUsageSession(usage_data[index], error_detail);
   if (KEY_ADDED != status) {
     LOGE("RestoreUsageSession failed: index = %zu, status = %d", index,

libwvdrmengine/cdm/core/src/usage_table_header.cpp

@@ -4,6 +4,7 @@
 
 #include "usage_table_header.h"
 
+#include "cdm_random.h"
 #include "crypto_session.h"
 #include "license.h"
 #include "log.h"
@@ -21,6 +22,7 @@ std::string kOldUsageEntryServerMacKey(wvcdm::MAC_KEY_SIZE, 0);
 std::string kOldUsageEntryClientMacKey(wvcdm::MAC_KEY_SIZE, 0);
 std::string kOldUsageEntryPoviderSessionToken =
     "nahZ6achSheiqua3TohQuei0ahwohv";
+
 }  // namespace
 
 namespace wvcdm {
@@ -152,8 +154,11 @@ CdmResponseType UsageTableHeader::AddEntry(
   for (uint32_t retry_count = 0; retry_count < kMaxCryptoRetries &&
                                  status == INSUFFICIENT_CRYPTO_RESOURCES_3;
        ++retry_count) {
-    int64_t entry_number_to_delete = GetRandomInRange(usage_entry_info_.size());
-    if (entry_number_to_delete < 0) break;
+    if (usage_entry_info_.size() == 0) {
+      break;
+    }
+    uint32_t entry_number_to_delete =
+        CdmRandom::RandomInRange(usage_entry_info_.size() - 1);
     DeleteEntry(entry_number_to_delete, file_handle_.get(), metrics);
 
     status = crypto_session->CreateUsageEntry(usage_entry_number);
@@ -226,10 +231,14 @@ CdmResponseType UsageTableHeader::LoadEntry(CryptoSession* crypto_session,
   for (uint32_t retry_count = 0; retry_count < kMaxCryptoRetries &&
                                  status == INSUFFICIENT_CRYPTO_RESOURCES_3;
        ++retry_count) {
+    if (usage_entry_info_.size() <= 1) break;
     // Get a random entry from the other entries.
-    int64_t entry_number_to_delete = GetRandomInRangeWithExclusion(
-        usage_entry_info_.size(), usage_entry_number);
-    if (entry_number_to_delete < 0) break;
+    uint32_t entry_number_to_delete =
+        CdmRandom::RandomInRange(usage_entry_info_.size() - 2);
+    if (entry_number_to_delete >= usage_entry_number) {
+      // Exclude |usage_entry_number|.
+      ++entry_number_to_delete;
+    }
     DeleteEntry(entry_number_to_delete, file_handle_.get(), metrics);
     status = crypto_session->LoadUsageEntry(usage_entry_number, usage_entry);
   }
@@ -723,27 +732,6 @@ bool UsageTableHeader::UpgradeUsageInfoFromUsageTable(
   return NO_ERROR;
 }
 
-int64_t UsageTableHeader::GetRandomInRange(size_t upper_bound_exclusive) {
-  if (upper_bound_exclusive == 0) {
-    LOGE("|upper_bound_exclusive| must be > 0");
-    return -1;
-  }
-  return (int)((double)rand() / ((double)RAND_MAX + 1) * upper_bound_exclusive);
-}
-
-int64_t UsageTableHeader::GetRandomInRangeWithExclusion(
-    size_t upper_bound_exclusive, size_t exclude) {
-  if ((upper_bound_exclusive <= 1) || (exclude >= upper_bound_exclusive)) {
-    LOGE(
-        "|upper_bound_exclusive| must be > 1 and |exclude| must be < "
-        "|upper_bound_exclusive|");
-    return -1;
-  }
-  uint32_t random = GetRandomInRange(upper_bound_exclusive - 1);
-  if (random >= exclude) random++;
-  return random;
-}
-
 // TODO(fredgc): remove when b/65730828 is addressed
 bool UsageTableHeader::CreateDummyOldUsageEntry(CryptoSession* crypto_session) {
   return crypto_session->CreateOldUsageEntry(

libwvdrmengine/cdm/core/test/device_files_unittest.cpp

@@ -11,6 +11,7 @@
 #include <string>
 
 #include "arraysize.h"
+#include "cdm_random.h"
 #include "file_store.h"
 #include "properties.h"
 #include "string_conversions.h"
@@ -2014,14 +2015,6 @@ class DeviceFilesTest : public ::testing::Test {
                                                    &device_base_path_));
   }
 
-  std::string GenerateRandomData(uint32_t len) {
-    std::string data(len, 0);
-    for (size_t i = 0; i < len; i++) {
-      data[i] = rand() % 256;
-    }
-    return data;
-  }
-
   size_t GetLicenseDataSize(LicenseInfo& data) {
     CdmAppParameterMap app_parameters = GetAppParameters(data.app_parameters);
     size_t app_parameters_len = 0;
@@ -2169,8 +2162,8 @@ MATCHER_P8(Contains, str1, str2, str3, str4, str5, str6, map7, str8, "") {
 
 TEST_F(DeviceCertificateStoreTest, StoreCertificate) {
   MockFileSystem file_system;
-  std::string certificate(GenerateRandomData(kCertificateLen));
-  std::string wrapped_private_key(GenerateRandomData(kWrappedKeyLen));
+  std::string certificate(CdmRandom::RandomData(kCertificateLen));
+  std::string wrapped_private_key(CdmRandom::RandomData(kWrappedKeyLen));
   std::string device_certificate_path =
       device_base_path_ + DeviceFiles::GetCertificateFileName();
 
@@ -2243,8 +2236,8 @@ TEST_F(DeviceCertificateTest, HasCertificate) {
 
 TEST_P(DeviceFilesSecurityLevelTest, SecurityLevel) {
   MockFileSystem file_system;
-  std::string certificate(GenerateRandomData(kCertificateLen));
-  std::string wrapped_private_key(GenerateRandomData(kWrappedKeyLen));
+  std::string certificate(CdmRandom::RandomData(kCertificateLen));
+  std::string wrapped_private_key(CdmRandom::RandomData(kWrappedKeyLen));
 
   CdmSecurityLevel security_level = GetParam();
   std::string device_base_path;

libwvdrmengine/cdm/core/test/file_store_unittest.cpp

@@ -5,6 +5,7 @@
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 
+#include "cdm_random.h"
 #include "file_store.h"
 #include "test_vectors.h"
 
@@ -30,14 +31,6 @@ class FileTest : public testing::Test {
     EXPECT_TRUE(file_system.Remove(test_vectors::kTestDir));
   }
 
-  std::string GenerateRandomData(uint32_t len) {
-    std::string data(len, 0);
-    for (size_t i = 0; i < len; i++) {
-      data[i] = rand() % 256;
-    }
-    return data;
-  }
-
   FileSystem file_system;
 };
 
@@ -104,7 +97,7 @@ TEST_F(FileTest, FileSize) {
   std::string path = test_vectors::kTestDir + kTestFileName;
   file_system.Remove(path);
 
-  std::string write_data = GenerateRandomData(600);
+  std::string write_data = CdmRandom::RandomData(600);
   size_t write_data_size = write_data.size();
   std::unique_ptr<File> file = file_system.Open(path, FileSystem::kCreate);
   ASSERT_TRUE(file);
@@ -119,7 +112,7 @@ TEST_F(FileTest, WriteReadBinaryFile) {
   std::string path = test_vectors::kTestDir + kTestFileName;
   file_system.Remove(path);
 
-  std::string write_data = GenerateRandomData(600);
+  std::string write_data = CdmRandom::RandomData(600);
   size_t write_data_size = write_data.size();
   std::unique_ptr<File> file = file_system.Open(path, FileSystem::kCreate);
   ASSERT_TRUE(file);

libwvdrmengine/cdm/core/test/usage_table_header_unittest.cpp

@@ -10,6 +10,7 @@
 #include <string>
 
 #include "arraysize.h"
+#include "cdm_random.h"
 #include "crypto_session.h"
 #include "device_files.h"
 #include "file_store.h"
@@ -990,10 +991,9 @@ TEST_F(UsageTableHeaderTest,
 
   // We try to load a usage entry from the first 9 entries, since DeleteEntry
   // can't delete an entry if the last one is in use.
-  int64_t usage_entry_number_to_load = MockUsageTableHeader::GetRandomInRange(
-      k10UsageEntryInfoVector.size() - 1);
-  ASSERT_THAT(usage_entry_number_to_load,
-              AllOf(Ge(0), Lt((int64_t)k10UsageEntryInfoVector.size() - 1)));
+
+  uint32_t usage_entry_number_to_load =
+      CdmRandom::RandomInRange(k10UsageEntryInfoVector.size() - 2);
   CdmUsageEntry usage_entry_to_load = kUsageEntry;
 
   // Setup expectations
@@ -1025,10 +1025,8 @@ TEST_F(UsageTableHeaderTest,
 
   // We try to load a usage entry from the first 8 entries, since DeleteEntry
   // can't delete an entry if the last one is in use.
-  int64_t usage_entry_number_to_load = MockUsageTableHeader::GetRandomInRange(
-      k10UsageEntryInfoVector.size() - 2);
-  ASSERT_THAT(usage_entry_number_to_load,
-              AllOf(Ge(0), Lt((int64_t)k10UsageEntryInfoVector.size() - 2)));
+  uint32_t usage_entry_number_to_load =
+      CdmRandom::RandomInRange(k10UsageEntryInfoVector.size() - 3);
   CdmUsageEntry usage_entry_to_load = kUsageEntry;
 
   // Setup expectations
@@ -1060,10 +1058,8 @@ TEST_F(UsageTableHeaderTest, LoadEntry_LoadUsageEntryFailsThrice) {
 
   // We try to load a usage entry from the first 7 entries, since DeleteEntry
   // can't delete an entry if the last one is in use.
-  int64_t usage_entry_number_to_load = MockUsageTableHeader::GetRandomInRange(
-      k10UsageEntryInfoVector.size() - 3);
-  ASSERT_THAT(usage_entry_number_to_load,
-              AllOf(Ge(0), Lt((int64_t)k10UsageEntryInfoVector.size() - 3)));
+  uint32_t usage_entry_number_to_load =
+      CdmRandom::RandomInRange(k10UsageEntryInfoVector.size() - 4);
   CdmUsageEntry usage_entry_to_load = kUsageEntry;
 
   // Setup expectations